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Multi-layer slopes are widely found in clay residue receiving fields. A generalized horizontal slice method (GHSM) for assessing the stability of multi-layer slopes that considers the energy dissipation between adjacent horizontal slices is presented. In view of the upper-bound limit analysis theory, the energy equation is derived and the ultimate failure mode is generated by comparing the sliding surface passing through the slope toe (mode A) with that below (mode B). In addition, the influence of the number of slices on the stability coefficients in the GHSM is studied and the stable value is obtained. Compared to the original method (Chen's method), the GHSM can acquire more precise results, which takes into account the energy dissipation in the inner sliding soil mass. Moreover, the GHSM, limit equilibrium method (LEM) and numerical simulation method (NSM) are applied to analyze the stability of a multi-layer slope with different slope angles and the results of the safety factor and failure mode are very close in each case. The ultimate failure modes are shown to be mode B when the slope angle is not more than 28°. It illustrates that the determination of the ultimate sliding surface requires comparison of multiple failure modes, not only mode A. [ABSTRACT FROM AUTHOR]

The two crucial shape factors (elongation ratio and flatness ratio) of brittle particles may influence the dynamic breakage of brittle particles upon impact. Hence, three‐dimensional discrete element method simulations of brittle rock blocks with different shapes upon normal impact were performed. The simulated results indicate that the elongation ratio, that is, ratio of width to length and flatness ratio, that is, ratio of thickness to width can significantly affect the breakage of brittle rock blocks. Three fracture mechanisms, that is, fragmentation, horizontal tensile fracture and vertical tensile fracture, were revealed, which determine the dynamic breakage of rock blocks. The fragmentation results in numerous single‐sphered fragments with velocities even larger than 2 times of the initial velocities. Fragmentation can provide a buffering effect at high impact velocities of larger than 4 m/s. With an increasing elongation ratio or flatness ratio, the phenomenon of fragmentation gradually disappears. The reflection of a compression stress wave results in horizontal tensile fracture. The expansion in the plane perpendicular to the impact velocity results in vertical tensile fracture. [ABSTRACT FROM AUTHOR]

Rock bolts are widely employed as an effective and efficient reinforcement method in geotechnical engineering. Sandwich composite structures formed by hard rock and weak rock are often encountered in practical projects. Furthermore, the spatial structure of the rock mass has a direct influence on the effect of the anchorage support. To investigate the impact of rock mass structure on the mechanical characteristics of anchorage interfaces, pull-out tests on reinforced specimens with different mudstone thicknesses and fracture dip angles are conducted. The experimental results indicate that the percentage of mudstone content and fracture dip angle have a significant influence on the pullout load of the samples. A weaker surrounding rock results in a lower peak load and a longer critical anchorage length, and vice versa. The results also show that 70% mudstone content can be considered a critical condition for impacting the peak load. Specifically, the percentage of mudstone content has a limited influence on the variation in the peak load when it exceeds 70%. Optical fiber deformation results show that compared to the rock mass with fracture dip angles of 0° and 60°, the rock mass with a fracture dip angle of 30° has a more uniformly distributed force at the anchorage interface. When the fracture dip angle exceeds 60°, the dip angle is no longer a key indicator of peak load. The accuracy of the experimentally obtained load-displacement curves is further verified although numerical simulation using the discrete element method. [ABSTRACT FROM AUTHOR]

Variations of reservoir water level and seasonal precipitation have reactivated or accelerated many reservoir landslides in the Three Gorges Reservoir area since impoundment in 2003. Updated daily monitoring data since 2017 reveals details about the step-like pattern of annual movement of the Baijiabao landslide, a large creeping landslide with a maximal cumulative surface displacement of 0.2 m over this 2-year period. The spatiotemporal deformation characteristics show that mass movement was greatest in 2017 and boundary cracks exhibit more frequent steps and are more sensitive to hydraulic factors than surface displacement. Acceleration periods are triggered when the reservoir water level falls below 153 m above mean sea level, with most annual movement occurring before the reservoir rises back to that critical level. The rate of daily surface movement is controlled by the daily variation of reservoir water level and by cumulative rainfall during the previous 1 to 7 days. The movement responses vary from different years and movement periods, but the one-factor critical-level model can effectively predict surface movement. The correlation between surface displacement rate and reservoir water level also comprehensively indicates the association between landslide movement and hydraulic factors including rainfall and variation of reservoir water level. Low reservoir level and its drawdown, and heavy or continuous rainfall, increase hydraulic gradients and change stress conditions, which destabilize the Baijiabao landslide and accelerate its surface movement. [ABSTRACT FROM AUTHOR]

• Impacts of water flow on hydrodynamic heat transfer in rock fractures were experimentally elucidated. • Parametric models linking heat transfer behaviors with flow rate and fracture geometry were developed. • Effect of nonlinear flow resistance on the feasibility of heat extraction was quantified. Hydrodynamic heat transfer in rock fractures is crucial for many geophysical processes and engineering activities, notably in harnessing geothermal energy. Despite extensive research, characterizing hydrodynamic heat transfer in rock fractures, complicated by their geometric heterogeneity, remains a formidable challenge. To address this challenge, we experimentally investigated the hydrodynamic heat transfer in rock fractures with diverse geometric features at steady-state elevated temperatures. We found that both heterogeneous fracture geometry and elevated temperatures promote the transition of fracture flow from a linear to nonlinear regime. This flow regime transition enhances the heterogeneity of heat transfer intensity within the fracture and exacerbates the increase in heat transfer efficiency with flow rate. At a fortyfold increase in flow rate, the heat transfer coefficient in the most heterogeneous fracture rises by approximately 72 times, compared to about 28 times in the least heterogeneous one. Leveraging experimental data, we developed parametric models linking heat transfer coefficients, outflow temperature, and heat recovery rate to flow rate and geometric features, yielding a theoretical formulation for the maximal heat recovery rate. By introducing the concept of an energy conversion rate, we quantitatively evaluated the effect of nonlinear flow resistance on heat extraction feasibility, revealing that energy conversion rates in highly heterogeneous fractures can be up to 452 times lower than in less heterogeneous ones. This highlights the pivotal role of flow resistance in heat extraction feasibility. Our findings are instrumental for understanding and predicting the hydrodynamic heat transfer within fractured geothermal reservoirs and analogous hydro-thermal systems. [ABSTRACT FROM AUTHOR]

The measurement of the water contact angle (θ) on the surface of clay minerals poses a significant challenge due to their microscopic particle sizes ranging from micrometers to nanometers and their extensive specific surface areas. We introduce an advanced computational framework based on molecular dynamics simulations. This framework leverages the coordination number (CN) differences of the water molecules and effectively eliminates the gaseous water molecules in the droplet equilibrium system. Additionally, our framework uses an alpha-shaped probe ball to accurately determine the three-dimensional (3D) coordinates of the droplet interface and utilizes a feed-forward neural network (FFNN) to optimize the objective function of the 3D-interface; this ensures highly accurate characterization of the interface contour and an accurate computation of θ. Our approach exhibits outstanding performance in typical clay mineral surface-water wetting systems; it significantly overcomes the limitations of the transformed cylindrical coordinate system algorithm and accurately captures the wettability variations under complex environmental conditions. This new θ computational framework provides crucial assistance for the in-depth exploration of the wettability characteristics of clay minerals in complex environments. • A novel computational framework for calculating θ in 3D wetting systems. • The precision of 3D interface contour characterization is greatly improved. • Computing framework has great potential in micro-nano wetting system. [ABSTRACT FROM AUTHOR]

The paper develops an analytical method to design the plane arrangement of stabilising piles under spatial lateral load of 3D colluvial landslides with multilayer sliding masses. Firstly, an approach based on the geological map and binary Lagrange Interpolation method was presented to establish 3D landslide calculation models. The improved 3D limit equilibrium method was then proposed to calculate the stability coefficient and spatial distributed lateral load of landslide with multilayer sliding masses. And main sliding direction of 3D multilayer landslide can be determined by the developed principle of minimum potential energy. Moreover, through assuming the piles and soil as elastic transversely isotropic continuum medium, analytical approach was employed to accurately calculate the stress distribution of soil between adjacent piles; and the maximum pile spacing can be calculated. Finally, the reasonable arrangement of stabilising piles can be determined based on Monte-Carlo method and cost of all piles. The finite difference method was employed to validate the theoretical results through the case study of Bazimen landslide. And it is found that the proposed method for the design of piles' arrangement is economically beneficial compared with the traditional method on the premise of ensuring safety. [ABSTRACT FROM AUTHOR]

A large-scale obliquely inclined bedding rockslide, activated by a heavy rainstorm, occurred on July 8, 2020, at 7:05 (UTC + 8) in Shiban Village, Songtao Miao Autonomous County, Guizhou Province, China. The loss of life in this event was greatly reduced owing to the local warning system for rainstorm-induced geohazards. To understand the failure characteristics, triggering factors, the genetic mechanism of the landslide, the geomorphological features, geological characteristics, hydrological conditions, and rainfall characteristics were systematically studied by a synthetic approach including field investigations, satellite imagery, unmanned aerial vehicle (UAV) photography, laboratory tests, and rainfall data statistics. The results indicated that the interface between the soft and hard rock, the well-developed joints, and the free face in front of the slope constituted the boundaries of this landslide. The concave topography at the back and southern edge of the landslide, the bare ground, and the cataclastic structure of the rock mass provided favorable conditions for the collection or infiltration of rainwater. The concentrated rainstorm was the direct trigger for the landslide, which led to a rapid inflow and retention of rainfall in the landslide through favorable landform and geological conditions. The groundwater recharge that cannot be drained in time caused the mechanical deterioration of rock mass and induced a rapid increase in pore water pressure in the landslide. Moreover, the water level of the Ganlong River at the toe of the slope also rose rapidly, and the uplift pressure in front of the slope increased accordingly. Under the combined action of these adverse factors, the overall anti-sliding force of the slope was less than the sliding force, finally resulting in the landslide. Remarkably, the local warning system for rainstorm-induced geohazards successfully forecasted the landslide, but the shortcoming is that the forecast time in advance is short. Nevertheless, the prediction has significantly reduced human casualties and provided valuable experience for the prediction of this type of landslide. [ABSTRACT FROM AUTHOR]

Accurate estimation of slope stability based on numerous candidate estimation methods is difficult as different results may be yielded. It becomes even more challenging when only limited data of geotechnical parameters (e.g., shear strength parameters) are available to evaluate slope reliability. Based on the Bayesian sequential updating technology, a hybrid framework for slope reliability was proposed in this study, through which prior knowledge, multiple estimation methods, and corresponding model uncertainties could be integrated to estimate slope reliability using a small amount of geotechnical data. Three slope examples with various stratigraphic configurations and soil properties were used to illustrate the accuracy and efficiency of the proposed framework, during which the Bishop's simplified method, the upper bound limit analysis method, and the finite element method were adopted. The results showed that with results of direct Monte Carlo simulation based on each method as the benchmark, a compromised mean of the factor of safety (μFS), and conservative standard deviation of the factor of safety (σFS) and failure probability (Pf) were yielded through the proposed framework. When the sample size of geotechnical parameters was greater than a threshold, the estimated μFS was stable, while the σFS and Pf synchronously varied within a small range with the increase in sample size. Demonstrations of the three examples indicated that the proposed hybrid framework can provide reliable and accurate estimations of slope reliability. The proposed framework may serve as a promising vehicle for slope/landslide engineering including failure and preventative mechanisms, movement prediction, and back analysis of geotechnical parameters in a probabilistic context, and big data analysis of geological and geotechnical problems as well. [ABSTRACT FROM AUTHOR]

Stabilizing piles are commonly used to effectively reinforce landslides and unstable slopes. However, the reinforcement mechanism of stabilizing piles, especially portal double-row (PDR) piles, remains poorly understood. The deformation characteristics and stabilizing mechanism of PDR piles were examined through physical model tests and numerical modeling by considering various embedded depths and interbedded weak and hard bedrock combinations. First, physical model tests were performed to study the effects of interbedded bedrock, orthogonal joints in the upper hard stratum, and embedded depths on the stabilizing mechanism. Second, six groups of numerical models based on the physical models were developed using the distinct element method. The results show that the bending moment and horizontal displacement of PDR piles increase in the presence of orthogonal joints and decrease with increasing embedded depth. The effects of crossbeam and hard bedrock percentage on the PDR pile deformation mechanism were then assessed. The results show that the crossbeam significantly affects the stabilizing PDR pile mechanism, while the effect of hard bedrock percentage is relevant to the embedded depth of PDR piles. The study provides some theoretical information for landslide prevention in areas with interbedded weak and hard bedrock. [ABSTRACT FROM AUTHOR]

Moraine soils are widely distributed in southeast Tibet of China, which poses a serious threat to local railway construction. The mechanical behavior of moraine soil containing ice in cold regions is difficult to capture under the joint action of stress conditions and temperature. To study the strength characteristics of ice-rich moraine soil, a total of 112 groups of thermal-mechanical triaxial tests under different ice forms, ice contents, and temperature conditions are carried out. The test results show that the mechanical properties of moraine soil with crushed ice and block ice are different, showing the characteristics of strain hardening and strain softening, respectively. Overall, the peak strength of moraine soil with block ice is greater than that of crushed ice. The cohesion and internal friction angle of moraine soil decreases with the temperature rise. With the increase of ice content, the peak strength of moraine soil with block ice increases, while that of crushed ice shows the opposite trend. In addition, the increase of ice content increases the cohesion of moraine soil with block ice, but there is a threshold value of ice content (25%) for moraine soil with crushed ice, which leads to the maximum cohesion at this time. Based on the test results, a unified function is proposed to describe the quantitative relationship between the strength parameters of ice-rich moraine soil, temperature, and ice content. Finally, to explore the nonlinear strength behavior of moraine soil, a binary-medium model is introduced to describe its stress-strain relationship, and the evolution of the main parameters in the model is analyzed. Comparing theoretical and experimental results demonstrates that the established model is of satisfactory applicability to simulate the mechanical behavior of moraine soil with different ice forms. • The stress-strain curve of soil containing crushed ice shows strain-hardening characteristics. • The stress-strain curve of soil containing block ice shows strain-softening characteristics. • There is an ice content threshold of moraine soil with crushed ice which makes the most effective cohesion. • The strength parameter model of moraine soil considering temperature and ice content is described. • The stress-strain relationship of ice-rich moraine soil is modeled utilizing a binary medium model. [ABSTRACT FROM AUTHOR]

Backgrounds: Pregnancy termination during the second trimester in patients with placenta previa and placenta accreta spectrum (PAS) is a complex and challenging clinical problem. Based on our literature review, there has been a relative increase in the number of such cases being treated by hysterotomy and/or local uterine lesion resection and repair. In the present study, a retrospective analysis was conducted to compare the clinical outcomes when different management strategies were used to terminate pregnancy in the patients with placenta previa and PAS. Methods: A total of 51 patients who underwent pregnancy termination in the second trimester in Beijing Obstetrics and Gynecology Hospital between June 2013 and December 2018 were retrospectively analyzed in this study. All patients having previous caesarean delivery (CD) were diagnosed with placenta previa status and PAS. Results: ① Among the 51 patients, 16 cases received mifepristone and misoprostol medical termination, 15 cases received mifepristone and Rivanol medical termination, but 1 of them was transferred to hysterotomy due to failed labor induction, another 20 cases were performed planned hysterotomy. There was no placenta percreta cases and uterine artery embolization (UAE) was all performed before surgery.② There were 31 cases who underwent medical termination and 30 cases were vaginal delivery. Dilation and evacuation (D&E) were used in 20 cases of medical abortion failure and in all 30 cases of difficult manual removal of placental tissue. ③ A statistically significant difference was found among the three different strategies in terms of gestational weeks, the type of placenta previa status, main operative success rate and β-HCG regression time (P < 0.05). ④ There were 4(7.8%) cases who were taken up for hysterectomy because of life-threatening bleeding or severe bacteremia during or after delivery and hysterotomy. The uterus was preserved with the implanted placenta partly or completely left in situ in 47(92.2%) cases. Combined medical and/or surgical management were used for the residual placenta and the time of menstrual recovery was 52(range: 33 to 86) days after pregnancy termination. Conclusions: Terminating a pregnancy by vaginal delivery through medical induction of labor may be feasible if clinicians have an overall understanding of gestational age, the type of placenta previa status, the type of placenta accreta, and patients concerns about preserving fertility. A collaborative team effort in tertiary medical centers with a very experience MDT and combined application of multiple methods is required to optimize patient outcomes. [ABSTRACT FROM AUTHOR]

Backgrounds: Pregnancy termination during the second trimester in patients with placenta previa and placenta accreta spectrum (PAS) is a complex and challenging clinical problem. Based on our literature review, there has been a relative increase in the number of such cases being treated by hysterotomy and/or local uterine lesion resection and repair. In the present study, a retrospective analysis was conducted to compare the clinical outcomes when different management strategies were used to terminate pregnancy in the patients with placenta previa and PAS. Methods: A total of 51 patients who underwent pregnancy termination in the second trimester in Beijing Obstetrics and Gynecology Hospital between June 2013 and December 2018 were retrospectively analyzed in this study. All patients having previous caesarean delivery (CD) were diagnosed with placenta previa status and PAS. Results: ① Among the 51 patients, 16 cases received mifepristone and misoprostol medical termination, 15 cases received mifepristone and Rivanol medical termination, but 1 of them was transferred to hysterotomy due to failed labor induction, another 20 cases were performed planned hysterotomy. There was no placenta percreta cases and uterine artery embolization (UAE) was all performed before surgery.② There were 31 cases who underwent medical termination and 30 cases were vaginal delivery. Dilation and evacuation (D&E) were used in 20 cases of medical abortion failure and in all 30 cases of difficult manual removal of placental tissue. ③ A statistically significant difference was found among the three different strategies in terms of gestational weeks, the type of placenta previa status, main operative success rate and β-HCG regression time (P < 0.05). ④ There were 4(7.8%) cases who were taken up for hysterectomy because of life-threatening bleeding or severe bacteremia during or after delivery and hysterotomy. The uterus was preserved with the implanted placenta partly or completely left in situ in 47(92.2%) cases. Combined medical and/or surgical management were used for the residual placenta and the time of menstrual recovery was 52(range: 33 to 86) days after pregnancy termination. Conclusions: Terminating a pregnancy by vaginal delivery through medical induction of labor may be feasible if clinicians have an overall understanding of gestational age, the type of placenta previa status, the type of placenta accreta, and patients concerns about preserving fertility. A collaborative team effort in tertiary medical centers with a very experience MDT and combined application of multiple methods is required to optimize patient outcomes. [ABSTRACT FROM AUTHOR]

Backgrounds: Pregnancy termination during the second trimester in patients with placenta previa and placenta accreta spectrum (PAS) is a complex and challenging clinical problem. Based on our literature review, there has been a relative increase in the number of such cases being treated by hysterotomy and/or local uterine lesion resection and repair. In the present study, a retrospective analysis was conducted to compare the clinical outcomes when different management strategies were used to terminate pregnancy in the patients with placenta previa and PAS.Methods: A total of 51 patients who underwent pregnancy termination in the second trimester in Beijing Obstetrics and Gynecology Hospital between June 2013 and December 2018 were retrospectively analyzed in this study. All patients having previous caesarean delivery (CD) were diagnosed with placenta previa status and PAS.Results: ① Among the 51 patients, 16 cases received mifepristone and misoprostol medical termination, 15 cases received mifepristone and Rivanol medical termination, but 1 of them was transferred to hysterotomy due to failed labor induction, another 20 cases were performed planned hysterotomy. There was no placenta percreta cases and uterine artery embolization (UAE) was all performed before surgery.② There were 31 cases who underwent medical termination and 30 cases were vaginal delivery. Dilation and evacuation (D&E) were used in 20 cases of medical abortion failure and in all 30 cases of difficult manual removal of placental tissue. ③ A statistically significant difference was found among the three different strategies in terms of gestational weeks, the type of placenta previa status, main operative success rate and β-HCG regression time (P < 0.05). ④ There were 4(7.8%) cases who were taken up for hysterectomy because of life-threatening bleeding or severe bacteremia during or after delivery and hysterotomy. The uterus was preserved with the implanted placenta partly or completely left in situ in 47(92.2%) cases. Combined medical and/or surgical management were used for the residual placenta and the time of menstrual recovery was 52(range: 33 to 86) days after pregnancy termination.Conclusions: Terminating a pregnancy by vaginal delivery through medical induction of labor may be feasible if clinicians have an overall understanding of gestational age, the type of placenta previa status, the type of placenta accreta, and patients concerns about preserving fertility. A collaborative team effort in tertiary medical centers with a very experience MDT and combined application of multiple methods is required to optimize patient outcomes. [ABSTRACT FROM AUTHOR]

An increasing number of landslides are occurring during the construction of highways in mountainous areas all over the world. A recent highway landslide located in the mountainous region of Southwest China is taken as a representative example to carry out the initiation mechanism and deformation characteristics analysis, and study the intelligent partitioning method in this paper. The geological conditions of the landslide are obtained through detailed geological surveys and investigation. A three-dimensional (3D) monitoring network with a total of 72 multi-points, including 53 surface displacement monitoring points and 19 deep displacement monitoring holes, is established to examine the spatial deformation characteristics of the landslide for nearly 25 months. The monitoring results of the surface displacement show that the dynamic deformation of the landslide can be divided into three stages, namely initial deformation stage, accelerated deformation stage, and stabilization stage. Based on the strata distribution obtained by the borehole investigation and the results of deep displacement monitoring, the depth of the slip surface can be reliably determined. The smart contract method in blockchain technology combined with the multi-point monitoring dataset is novelty applied to realize the intelligent automatic partition of the highway landslide without any human involvement. This method can provide the basis for further independent analysis of different landslide zones. According to the investigation and analysis, the initiation mechanism for the highway landslides is attributed to both internal poor geological conditions and external intense precipitation and engineering excavation. [ABSTRACT FROM AUTHOR]

Understandings of reinforcement mechanisms of landslide-stabilizing pile system are important for long-term safety of reservoir landslides installed piles. The paper proposes a framework to study deformation response and identify triggering factors for landslide–pile system by using geographic detector technology and uncertainty of monitoring data. Majiagou landslide, a representative reservoir landslide installed stabilizing and test piles, is selected as the case study. Firstly, monitoring data of monthly rainfall, variations of reservoir water level, deformation of landslide surface and piles' head were preprocessed. The random deformation data were generated considering uncertainty of deformation monitoring data. Meanwhile, the deformation response of landslide–pile system is analyzed through studying the monitoring deformation data and random deformation data using the clustering algorithm. Finally, geographic detector technique was used to identify main triggering factors of landslide surface deformation and explore interaction types of any two factors. The uncertainty of monitoring data was used to identify the most important triggering factor. Influences of different error and uncertainty of monitoring data on the influence degrees of each factor were further discussed. The comparison with improved Apriori algorithm shows that the presented framework can intuitively measure influence degrees of each factor and analyze interaction types of any two factors. The main conclusions by studying Majiagou landslide indicate that the anti-slide performance and action range of piles gradually decrease with the increase of hydraulic cycle; the deterioration of geomaterials' properties are the most important triggering factor leading to the deformation of landslide–pile system and the degradation of piles' performance, supported by most random deformation groups. [ABSTRACT FROM AUTHOR]

• Impacts of wall porosity on fracture flow were systematically investigated at pore scale. • Mechanisms governing direction and magnitude of fluid exchange at the fracture-matrix interface were elucidated. • Flux contributions of porous walls to fracture outlet and fracture-matrix interface were functionalized by wall porosity. • Influence of porous walls cannot be equivalently represented by applying slip boundary conditions. This study investigates the influence of porous walls on fluid flow behavior in single rough-walled fractures. A series of direct numerical simulations (DNS) were conducted to examine fluid flow through rough-walled fractures surrounded by porous walls under various hydraulic gradients. The simulation results clearly demonstrate the progressively significant impact of porous walls on flow characteristics as porosity increases. Regression analyses indicate that the Forchheimer's law, which characterizes the nonlinear flow of rock fractures, remains valid in the presence of porous walls. Moreover, increased porosity enhances fluid exchange and leads to an increased ability for single fractures to transmit fluid. Two double-parameter equations were established to quantitatively characterize the effects of porous walls on hydraulic conductivity of the fracture and fluid exchange between porous walls and the fracture. Further analysis revealed that the angle between the fracture profile and main flow direction profoundly influences the inflow/outflow exchange between the fracture and its adjacent porous walls. Moreover, the pore-scale results indicate that it is unreasonable to equate the effect of porous walls with slip boundaries as suggested in previous studies. The results and findings of this study deepen our understanding of flow behavior at the interface between the rough-walled fracture and adjacent porous walls, and they serve as a basis for accurately simulating large-scale fracture networks that consider the hydraulic contribution of fracture walls. [ABSTRACT FROM AUTHOR]

On 22 October 2018, at 17:20 (UTC+8), a bedding rockslide occurred on the right bank of the Jian-En expressway in Jianshi County, Hubei Province, Central China. Fortunately, a systematic displacement monitoring network provided an early warning. Thus, no casualties were caused by the rockslide, although two transport vehicles and three houses were damaged. To deduce the triggering factors and failure mechanism of the bedding rockslide, the geological characteristics, hydrogeological characteristics, slope excavation scheme, and rainfall data statistics were systematically investigated based upon field investigations, UAV photography, geological drilling, and laboratory tests. It was found that the bedding characteristics, presence of well-developed joints, and properties of the weak interlayers were the internal factors inducing the rockslide. The free face in front of the slope, the weak interlayer with low shear strength, and the through-going joint that formed the back boundary of slope constituted the boundary of the rockslide. The combined effects of improper slope excavation and concentrated rainfall were external factors that directly triggered the rockslide. The well-developed joints provided an effective infiltration channel for rainwater, and continuous rainfall deteriorated the shear strength of the weak interlayer ultimately causing the rockslide. [ABSTRACT FROM AUTHOR]

Zigui Basin is a major landslide-prone region in the Three Gorges Reservoir region of China, and the stabilizing pile is an effective and widely employed countermeasure to reinforce landslides in this region. However, stabilizing piles are mostly designed using deterministic and stability-oriented methods, which generally ignore the system performance and cost-effectiveness. Using the Majiagou landslide reinforced with stabilizing piles as a case study, a probabilistic multi-objective optimization framework for the design of stabilizing piles is proposed and illustrated. Specifically, performance objectives related to failure probability, system robustness and life-cycle cost of the landslide-stabilizing pile system with feasible designs are evaluated, then the best compromised design is obtained by means of Pareto optimality. Expert knowledge and professional judgment are required to set necessary restrictions and finally determine the optimal design. The results show that there is a better design of stabilizing piles than the existing one, with which acceptable reinforcement effectiveness, compromised life-cycle cost and robust system performance can be realized. The optimal design will also vary with the concerned performance objectives and knowledge-based judgment. Further relationships and interpretations between design parameters and system responses are discussed through parametric analyses. [ABSTRACT FROM AUTHOR]

Natural rock often suffers from cyclic wetting–drying involving different water types, and the resulting deterioration may differ from laboratory tests using distilled water or salt solutions. An inappropriate estimation of this deterioration effect may lead to fatal geological hazards and engineering failures. A multiscale study is conducted to investigate the physical and mechanical features of sandstone in Three Gorges Reservoir region (TGR sandstone) subjected to cyclic wetting–drying of Yangtze River water. During this study, three types of water, i.e., Yangtze River water, ionized water having similar ion compositions as the Yangtze River water, and distilled water, are used for comparison. The results show that the multiscale physical properties including mineral compositions (especially calcite and albite), micro-pore parameters, computed tomography values, and macro-mechanical parameters (i.e., Young's modulus, uniaxial compression strength and tensile strength) are remarkably altered during the cyclic wetting–drying process. Significant correlations are found between these numerous multiscale properties. The results indicate that changes of mineral compositions and microstructure are the primary reasons for the deterioration of sandstone strength. The deterioration effect of distilled water on TGR sandstone is the least, while the effect of ionized water is the greatest, and that of river water being intermediate. These differences are ascribed to different chemical interactions, together with possible microorganism effects for river water, as microorganisms in river water potentially weaken the deterioration of cyclic wetting–drying of river water. In situ water is recommended for studying how rock properties are affected by water–rock interactions in real settings. [ABSTRACT FROM AUTHOR]

Variations of reservoir water level and seasonal precipitation have resulted in significant movement and destabilization of landslides in the Three Gorges Reservoir (TGR) region of China since reservoir impoundment in 2003. An example is the Baijiabao landslide, a large, actively creeping landslide located in the steep lower valley of the Xiangxi River, about 55 km upstream of the TGR dam in the Yangtze River. Twelve years of monthly monitoring at four GPS stations and routine, monthly field observations show cumulative GPS displacements as large as >1.5 m and widely developed ground cracks. GPS monitoring results show that most movement takes place in rapid steps that coincide with the rainy season and the period of annual reservoir drawdown, with particularly large steps in 2009, 2012 and 2015. This step-like pattern of displacement is also shown by daily data from an automatic monitoring system installed in 2017. The total period of acceleration shown by these daily data was about six weeks long, with rapid movement starting during rapid reservoir drawdown, and terminating when the reservoir began to rise again. In particular, most of the 2018 displacement occurred in only two weeks. Different subzones of the landslide move at different rates and exhibit different features of deformation. The neighborhood rough set theory is used to identify the triggering factors responsible for landslide deformation. The most important triggering factors vary between different sites, data types and the time interval used to define them. The surface deformation and ground crack widening are controlled by the combination of rainfall and variations in the reservoir water levels, whereas the deformation of the sliding zone is most sensitive to the latter. The results show that daily data are needed to capture important, short-term landslide responses. The neighborhood rough set theory for determination of triggering factors is suggested for deformation prediction, stability evaluation, and prevention and control of reservoir landslides in this and other regions. • Spatiotemporal deformation characteristics of Baijiabao landslide over a twelve-year period are analyzed in detail. • Different acceleration periods and threshold hydraulic conditions are observed from daily and monthly monitoring data. • Neighborhood rough set theory is used to identify the triggering factors responsible for landslide deformation. • The most important triggering factors vary between different sites, data types and the time interval used to define them. [ABSTRACT FROM AUTHOR]

The Green-Ampt (GA) model is one of the most widely used analytical methods of slope stability under rainfall. However, it may overestimate the soil water content above the wetting front. In this study, a novel approach to evaluate the time-dependent slope stability during intense rainfall based on a modified GA model is presented, and is known as the stratified Green-Ampt (SGA) model. By considering the stratified soil water content above the wetting front, the soil above the wetting front can be divided into saturated and transitional layers, and the SGA model is used to analyze the infiltration process of intense rainfall into slopes. Thereafter, safety factors (Fs) of infinite and finite slopes are derived using the SGA model. In the analysis of an infinite slope, the conventional limit equilibrium method is adopted to calculate the safety factor; as for a finite slope, the residual thrust method is introduced to obtain the safety factor with sliding mass divided into multiple soil slices. The performance of the SGA model is illustrated in two cases: an infinite slope and the Majiagou landslide as a finite slope. The results indicate that compared to the GA model, the calculated wetting front based upon the SGA model moves faster, and the wetting front depth shows a positive correlation with the slope surface angle and rainfall intensity. The evolution of the safety factor above the sliding surface can be divided into three phases, while the evolution of the safety factor above the wetting front can be divided into two phases. The critical time of the slope reaching a less stable state (safety factor is 1.05) or unstable state (safety factor is 1.00) decreases exponentially with an increase in rainfall intensity. In addition, the rainfall has a significant influence on the design of stabilizing piles for the Majiagou landslide. The presented SGA model appears to be accurate to investigate slope stability during intense rainfall events. [ABSTRACT FROM AUTHOR]

Analyzing and quantifying the deformation process of landslides is of paramount importance in facilitating landslide early warning. As such, this study is committed to proposing a universal phenomenological model for deformation stages division and early warning of landslides based on the kinematic features. First, five landslide deformation patterns were classified based on the creep theory, and suggestions for stage division of each deformation pattern are presented. Then, the statistical characteristics of landslide velocity were analyzed, and a probability-based deformation stage division method was proposed. Finally, the Comprehensive Standardized Deformation Index (CSDI) model, which includes the calculation of the CSDI M - M (Min-Max normalization) and CSDI M (Mean normalization) was proposed and verified in 24 landslides worldwide. The results show that, except for the oscillating pattern, the CSDI M - M is feasible in the stages division of all deformation patterns with a strong correspondence with the actual state of the landslides. The CSDI M is a reliable landslide warning criterion and threshold determination method, as it is effective in the early warning of imminent landslides with a low false alarm rate. The CSDI model provides new insight into the division of landslide deformation stages and landslide risk assessment. [ABSTRACT FROM AUTHOR]

In a recent discussion by Rashida and Singh (Rock Mech Rock Eng, 2023) regarding our paper (Tan et al. Rock Mech Rock Eng 56:7599–7617, 2023) investigating the thermal effects on non-Darcian flow within heated rock fractures, several points were raised. They argued that the temperatures and durations in our experiments may not induce thermal expansion in fractured rock due to low thermal expansion coefficients. Additionally, they highlighted potential water phase changes during heating and recommended precautions, such as pre-heated water and confining pressure, which were not implemented in our experimental setup. In response, we provide further clarification. Firstly, concerning heating time, our focus is on temperature-induced alterations in fracture geometry during the heating process rather than after temperature stabilization. Secondly, our detailed analysis of the coefficient of thermal expansion for granite specimens confirms that thermal expansion does lead to fracture closure within the imposed temperature range, affecting flow characteristics. Lastly, considering the aims of the study, precautions against water phase changes were not implemented, but the potential water phase changes had a negligible effect on our results due to the low temperatures employed and the short water residence time in the fracture. In summary, we maintain the methodological soundness of our experimental setup and the appropriateness of the obtained results in alignment with the objectives of our study. The discussion and this response are helpful to further clarify our experimental results and eliminate potential ambiguities. Highlights: Temperature-induced alterations in fracture geometry during the heating process are noteworthy. Even minor fracture closure resulting from thermal expansion markedly influences flow behaviors. Low test temperatures render potential water phase changes inconsequential to our findings. [ABSTRACT FROM AUTHOR]

As a consequence of seasonal variations in groundwater level and reservoir water level, natural rocks generally experience the cyclic wetting-drying process, in which the change in microstructure becomes a critical factor leading to the deterioration of the macro-physical and mechanical properties of rocks. However, it remains a great challenge to quantitatively characterize the microstructures of rock, especially during the wetting-drying process. In this study, a systematic experimental investigation involving multiple techniques (mercury injection capillary pressure (MICP), computer tomography (CT), scanning electron microscope (SEM), and pores (particles) and cracks analysis system (PCAS) software package-based image analysis) were conducted to study the microstructure of sandstone subjected to cyclic wetting-drying. The results show that sandstone experiences increasing microporosity during the cyclic wetting-drying process, with progressive changes in micro grains, defects, and micropore structure and morphology. The pore compositions gradually change into a bimodal distribution with dominating small-medium pores (10 nm-10 μm) and large pores (>10 μm). Eventually, connected crack networks and large-scale fractures develop. There is a strong correlation between the microporosity values evaluated by CT and MICP, indicating the capacity of describing the micropore compositions ranging from 0.03 to 0.78 mm. Besides, comparisons of the three techniques (i.e., MICP, CT, and SEM) and evolution mechanisms of sandstone microstructures are further discussed. • Sandstone microstructures under cyclic wetting-drying are studied via multiple techniques. • Pore area, complexity, and microporosity gradually increase, and defects grow. • Micropores have a bimodal distribution with small-medium pores and large pores being dominant. • Micropores show morphological anisotropy in three dimensions. • CT agrees with MICP in describing micropore compositions ranging from 0.02 to 1 mm. [ABSTRACT FROM AUTHOR]

Several colluvial landslides have developed in the Jurassic strata region of Zigui County, a major landslide-prone region in the Three Gorges Reservoir Region of China. The bedrock in which stabilizing piles are placed in the landslide-prone Zigui region can be generally characterized as upper sandstone and lower silty mudstone. A site investigation of the Majiagou No. 1 landslide indicated that the pile heads were displaced horizontally by approximately 15.0 cm. This paper presents a novel model for determining the reasonable embedded length for stabilizing piles in colluvial landslides with upper hard and lower weak bedrock based on the deformation control principle. A negative power function relationship between the horizontal displacement of the pile head and the reasonable embedded ratio for stabilizing piles is proposed on the basis of the allowable pile deformation according to industrial standards. Furthermore, the lower limit on the horizontal displacement of the pile head is deduced to obtain the maximum reasonable embedded ratio of stabilizing piles. Reasonable embedded length ratio models of stabilizing piles are analyzed based on various influencing factors. The results show that (1) increasing the embedded length of the piles can significantly reduce both the horizontal displacement and the maximum absolute value of the shear force on the piles, (2) the increase in the maximum bending moment of the pile with increasing embedded pile length is insignificant, and (3) increasing the thickness of the upper hard rock and the coefficients of subgrade reaction of the upper hard and lower weak rock and reducing the driving force of the landslide help to reduce the reasonable embedded length of the piles. Consequently, it is suggested that stabilizing piles should be set in stronger and thicker upper hard rock in regions with low landslide driving force in order to minimize the reasonable embedded length of the piles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The incomplete α-cage on [1 0 0]-D4R-e surface can adsorb more than four ethylene molecules. • The Si–OH and the Si–O–Al bridge on [1 0 0]-D4R-e surface are the active sites of ethylene oligomerization. • The reaction network of ethylene oligomerization is divided into stepwise polymerization path, concerted polymerization path and concerted butene path. • The energy barrier of the rate-determining step of ethylene oligomerization on K-LTA zeolite is significantly higher than that on other zeolites. • Trace n-butene will be formed when the temperature reaches 473 K, and oligomerization will occur at 513 K, which may lead to carbon deposition. The regeneration gas used in the K-LTA zeolite dryer of the MTO plant is planning to be changed from high purity nitrogen to the top gas of the demethanizer tower with high ethylene content, which is helpful to energy saving and emission reduction. However, there is a risk of ethylene oligomerization and carbon deposition when the regeneration gas passes through the K-LTA zeolite. The reaction mechanism of ethylene oligomerization on the K-LTA zeolite surface must be clarified. DFT calculations showed that ethylene could be physically adsorbed on Si–OH, Al–OH, the incomplete α- and β-cage on [1 0 0]-D4R-e surface. Butoxide forms through ethylene dimerization by stepwise and concerted mechanisms first. Then the reaction of ethylene and butoxide to n-hexyloxide leads to the continued growth of the carbon chain. The oligomerization reaction barriers of rate-determining steps are between 1.65∼1.75 eV, which is more difficult to occur than other zeolites. The ethylene oligomerization reaction can be divided into stepwise polymerization path, concerted polymerization path and concerted butene path. kMC simulation found that the dominant reaction paths are different under different temperatures. When the regeneration temperature reaches 473 K, trace n-butene is generated. At 513 K, ethylene oligommerization occurs and carbon deposition is formed. The results put forward higher requirements for strictly controlling the temperature of the dryer to ensure the excellent performance of K-LTA zeolite. [ABSTRACT FROM AUTHOR]

In this study, to investigate the variability of mechanical parameters of rock, a three-dimensional (3D) discrete element model (DEM) with the consideration of random microcracks was proposed. The random microcracks follow the negative power-law distribution with upper and lower limits of microcrack size. The results showed that coefficient of variations (COVs) and average values of elastic modulus, Poisson's ratio, unconfined compression strength and tensile strength of Lac du Bonnet granite are well matched through the present model. The present simulations indicate that the large COVs were induced by the interconnected large microcracks. The parametric study clearly indicates that the random microcracks significantly affect COVs, while the effect of grain size variation can be ignored. The size of microcracks determines the variability of mechanical parameters, and the volume density of microcracks can significantly influence the COVs. The correlation between the fractal dimension of microcrack size distribution and COVs is not linear. The increasing variability of microcrack density can result in the increase of COVs. Finally, a calibration procedure was proposed to determine the present model's parameters. [ABSTRACT FROM AUTHOR]

Severe instability disasters of hard rock often occur in pressurized deep tunnels with support systems. To investigate the deformation characteristics, brittle fracture process, failure mechanism, and collaborative effect of the rock and support system in a pressurized deep tunnel, physical model tests were designed and performed. An analog material preparation method is proposed for simulating the brittle failure of deep tunnels. The test results indicated that the brittleness and the strength of the developed analog material were significantly increased compared to those of previously reported analog materials, and its characteristics were similar to those of deep hard rock. The physical model tests realistically simulated the instantaneous process of brittle fracture of a pressurized deep tunnel, and the mechanical response laws of deformation, digital images, and acoustic emissions were captured. The strains of the surrounding rock, the lining, and the bolt were the largest in the shallow part of the sidewall and gradually decreased away from the tunnel. The brittle cracking paths of the shallow rock were along the direction of the internal pressure, whereas that of the interior rock mass were along the direction of the maximum principal stress. The brittle failure of a pressurized deep tunnel is caused by the incompatible tensile strain of the surrounding rock under the control of the anisotropic stress field. The bearing capacities of the surrounding rock, the lining, and the bolt decreased successively. Cyclic loading and unloading of internal pressure can reduce the bearing capacities of deep tunnels, whereas a constant internal pressure has a supporting effect. Highlights: The brittleness and strength of the developed analogue material were significantly increased compared with those of previously reported analogue materials, and its characteristics were similar to those of deep hard rock. The processes of brittle fracture of a pressurized deep tunnel with support system were realistically simulated via physical model tests. The deformation characteristics, fracture mechanism, bearing ratio, and collaborative effect of the surrounding rock and support system in a pressurized deep tunnel were analyzed. [ABSTRACT FROM AUTHOR]

Water flow through fractured rocks in high-temperature settings is relevant to many subsurface geo-energy engineering projects including geothermal energy extraction, hydrocarbon production, and nuclear waste disposal. However, existing studies have either focused only on flow process within fractures at room temperature or on the thermal effect on fracture permeability. As a result, how and to what extent rock temperature affects the flow behavior in rock fractures remains poorly understood. Herein, we report an experimental study of the heated flow behavior in rock fractures at steady-state elevated temperatures under sequentially increasing flow rates. We find that rock temperature greatly affects the flow behavior within the fracture via two mechanisms: water properties variations and fracture closure. The former reduces the flow resistance, while the latter both reduces the effective hydraulic aperture and enhances the inertial effect. The more heterogeneous the initial aperture distribution is, the more significant the effect of the temperature-induced fracture closure on the flow nonlinearity will be. By combining the Forchheimer equation with water temperature measured at the fracture inlet and outlet, we quantitatively evaluated the effect of these two mechanisms on rock fracture permeability and flow nonlinearity. Finally, we develop an empirical expression for the critical hydraulic gradient of the fracture at different temperatures based on the nonlinear flow model for room-temperature fractures to quantify the emergence of non-Darcian flow. The findings from the present study are expected to shed insight into the prediction and evaluation of fluid flow within deep subsurface fractured reservoirs. Highlights: Physical mechanism of thermal effect on water flow in heated rock fractures is revealed experimentally. Thermal effect promotes non-Darcian flow by changing water properties and inducing fracture closure. A parametric model to predict onset of non-Darcian flow in heated fractures is proposed. [ABSTRACT FROM AUTHOR]

The paper presents a study on the location determination of stabilizing piles in colluvial landslides with the interbedding of hard and soft bedrocks. A double-arc model is proposed to describe the shape of sliding surface of colluvial landslides, and the corresponding slope surface can be divided into three types, namely the concave type, straight line type, and convex type, respectively. The driving force of colluvial landslides and interbedding characteristics of hard and soft bedrocks are two important factors affecting the determination of optimal location for stabilizing piles. The results indicate that the stabilizing effect of the piles mainly depends upon the hard bedrock. The effect of the location of hard layer bedrock on the pile deformation is represented by the location coefficient. It is found that the optimal location of stabilizing pile locates where both top and bottom hard layers are present; and, the location with a top soft layer is unfavorable, particularly when the hard layer has a large location coefficient. The case study of Yanguan landslide illustrates that the location of stabilizing pile is determined with the proposed method is effective, with a considerable decrease in both the displacement and internal force of the stabilizing piles. [ABSTRACT FROM AUTHOR]

• Flow behaviors are associated with fracture heterogeneity and the filling conditions. • Filling particles result in two competing mechanisms impacting flow regime in fractures. • Fracture walls confining the fluid flow significantly reduce the media permeability. • A semi-empirical model for predicting water flow in filled fractures is proposed. Fluid flow through filled rock fractures is relevant to numerous engineering applications and geophysical processes. However, a proper understanding of the flow behaviors in filled fractures is still far from being completed. To investigate the fluid flow in a rough-walled fracture filled with a porous medium, we systematically compare the micro- and macroscopic flow behaviors within filled fractures and corresponding open fractures and porous media based on a series of pore-scale simulation results. We find that the filling medium has a dual role in altering the flow regime, as the filling particles can not only cut the flow domain into several pore channels and thus limit the generation of large-span eddies, but also force the fluid to flow around them and promote the generation of local eddies. Compared with porous media, the fluid flow within filled fractures is confined by fracture walls, which greatly alters the media permeability and the flow nonlinearity therein. By introducing the hydraulic radius and Darcy-Weisbach equation, we develop a new semi-empirical model to estimate the fluid flow through filled fractures using phenomenological coefficients of corresponding open fractures and porous media. The proposed model, satisfying dimensional consistency, shows high fidelity in predicting water flow through filled fractures. More importantly, this model can be successfully reduced to the typical form of the Forchheimer equation applied to open fractures and porous media. The results and findings are expected to be useful in predicting and evaluating the fluid flow in complex geological setting. [ABSTRACT FROM AUTHOR]

Cyclic interactions between rocks and water have general significance and are particularly relevant to engineering failures and geohazards. A comprehensive investigation of the multi-scale deterioration effects and mechanisms of cyclic wetting-drying on rocks can contribute to better engineering applications, but the probabilistic characterization of rock mass properties under cyclic wetting-drying remains a problem due to the difficult-to-test parameters and limited data. Numerous experiments on rock samples of argillaceous siltstone subjected to cyclic wetting-drying of Yangtze River water demonstrate progressive alteration of rock properties on multiple scales, including changes in mineralogy, grain structure, computed tomography, microporosity, and complexity of micropores, with calcite and albite being the most active minerals. The uniaxial compression strength and indirect tensile strength decrease exponentially with the cyclic number, while the Young's modulus increases. Considering the probabilistic characteristics of the geological strength index, the probabilistic mechanical properties of rock mass of studied argillaceous siltstone are then estimated through the generalized Hoek-Brown criterion. The results indicate that the uniaxial compression strength and indirect tensile strength of rock mass both follow lognormal distributions, while the Young's modulus follows a skewed distribution. Long-term strength parameters of rock and rock mass can also be determined as they exhibit exponential trends with the cyclic number. During the cyclic wetting-drying process, the water-rock interactions produce progressive changes in mineral compositions, microstructures, and micropores; with the accumulation of variations of physical properties, defects grow and develop into weak zones, thus the mechanical properties of argillaceous siltstone are significantly weakened. Investigations of the wetting-drying effects on the geological strength index and probabilistic characteristics of rock sample properties are recommended to accurately evaluate rock mass properties affected by cyclic wetting-drying. • Argillaceous siltstone is treated by cyclic wetting-drying of Yangtze River water. • Dissolution of calcite and albite results in the synergistic evolution of rock properties. • Micropores with a diameter greater than 100 μm become predominant. • Probabilistic properties of rock mass strength under cyclic wetting-drying are evaluated. • Long-term strength of the rock mass is evaluated through the exponential fitting. [ABSTRACT FROM AUTHOR]

This paper presents an optimization study on the layout and length of anchor cables for stabilizing rock wedges from the perspective of their three-dimensional geological characteristics. On the basis of the generalized geometry model for rock wedges, the expression of driving force of slope at the arbitrary longitudinal section can be deduced by employing the hyperbolic model between driving force and scale factor of rock wedges. Due to the remarkable parabolic characteristics of the driving force expression of rock wedges, a corresponding non-uniform layout principle of anchor cables was proposed, with closer layout in the central part and sparse layout near the side boundaries. The rational length of anchor cables was quantified on the basis of specification and the three-dimensional spatial characteristics of rock wedges. Furthermore, the upper limit spacing of anchor cables was determined by the spacing threshold caused by the parabolic distributed driving force. The spacing distribution of the optimized anchor cables was verified as a parabolic distribution according to a case study on the Shuige rock wedge in Lishui City, China. Compared with the conventional uniform spacing and length design scheme, the adjusted optimal non-uniform scheme can reduce the anchor cables by 16.9 % and 18.9 % in number and in total length, respectively. [ABSTRACT FROM AUTHOR]

• Influencing factors of infiltration modes were systematically investigated. • A semi-analytical model for three infiltration scenarios was established. • Evolution features of water head and stratified wetting zone were revealed. The classic GA model assumes a constant-head ponded water and with a saturated water content above the wetting zone, which limits its application. This study investigated a semi-analytical method for predicting rainwater infiltration into an inclined soil interlayer considering time-varying head and stratified water content. An evolving wetting profile and a half-parabolic wetting profile of transient zone were observed during infiltration process based on numerical simulations. The water head in the fissure showed a linearly-increasing characteristic before the soil interlayer was fully saturated, while showed an exponentially-increasing feature after the soil interlayer was fully saturated. A semi-analytical model was subsequently established for predicting the variables (time-dependent water head and the length of the stratified wetting zone) based on the classical GA equation, Darcy's law, and mass conversation law, as well as the numerical simulation calibration. This semi-analytical model describes three specific infiltration scenarios (scenarios I, II, and III) involving two infiltration modes (i.e., rainfall infiltration and constant-head infiltration), which were comprehensively shaped by fissure height, rain intensity, and duration. This model has a concise expression satisfying dimensional consistency and can be successfully reduced to the classic GA model. The validity of this semi-empirical model was further confirmed by numerical simulations, which showed good performance by capturing the evolving trends of the water head, saturated, transitional, and wetting zones in the inclined soil interlayer. The results and findings deepen the understanding of transient infiltration in rock slopes with inclined soil interlayer, and are helpfully for assessing the evolving slope stability during rainfall. [ABSTRACT FROM AUTHOR]

• Influencing factors of infiltration modes were systematically investigated. • A semi-analytical model for three infiltration scenarios was established. • Evolution features of water head and stratified wetting zone were revealed. The classic GA model assumes a constant-head ponded water and with a saturated water content above the wetting zone, which limits its application. This study investigated a semi-analytical method for predicting rainwater infiltration into an inclined soil interlayer considering time-varying head and stratified water content. An evolving wetting profile and a half-parabolic wetting profile of transient zone were observed during infiltration process based on numerical simulations. The water head in the fissure showed a linearly-increasing characteristic before the soil interlayer was fully saturated, while showed an exponentially-increasing feature after the soil interlayer was fully saturated. A semi-analytical model was subsequently established for predicting the variables (time-dependent water head and the length of the stratified wetting zone) based on the classical GA equation, Darcy's law, and mass conversation law, as well as the numerical simulation calibration. This semi-analytical model describes three specific infiltration scenarios (scenarios I, II, and III) involving two infiltration modes (i.e., rainfall infiltration and constant-head infiltration), which were comprehensively shaped by fissure height, rain intensity, and duration. This model has a concise expression satisfying dimensional consistency and can be successfully reduced to the classic GA model. The validity of this semi-empirical model was further confirmed by numerical simulations, which showed good performance by capturing the evolving trends of the water head, saturated, transitional, and wetting zones in the inclined soil interlayer. The results and findings deepen the understanding of transient infiltration in rock slopes with inclined soil interlayer, and are helpfully for assessing the evolving slope stability during rainfall. [ABSTRACT FROM AUTHOR]

Moraine soils are widely distributed in the Qinghai-Tibet Plateau. With increased global warming, moraine soil-related geohazards have become increasingly common, posing a serious threat to the infrastructure (e.g., the Sichuan–Tibet Railway) and inhabitants of this region. This paper aims to investigate the mechanical behavior of ice-rich moraine soil in the Tianmo Valley by conducting a series of triaxial constant strain rate (CSR) and coupled thermomechanical (CTM) tests on artificially moraine soil containing different ice forms (crushed ice and block ice). The results show that in general, compared to moraine soil containing crushed ice, moraine soil with block ice has a higher peak strength, a similar internal frictional angle and a considerably larger cohesive strength. The stress–strain curve of the soil containing crushed ice shows a strain-hardening form, while that of the soil containing block ice is represented by a strain-softening model similar to that of dense soil. In the CTM tests, it is revealed that the rising temperature could cause a sharp increase in strain and lead to sample failure, even when the axial load is far below the material's peak strength. A comparison between samples with different ice forms reveal that the soil containing crushed ice is more sensitive to temperature change. The tests demonstrate that the ice form has a significant influence on the mechanical behavior of moraine soil, and the temperature rise can result in a dramatic decrease in soil strength. Therefore, efforts should be made to detect the occurrence form of buried ice and the changes in the environmental temperature as well as the stress state of moraine soil slopes in situ. • The strength of the moraine soil containing block ice is higher than that of the soil containing crushed ice. • The stress-strain curve of the soil containing crushed ice shows a strain-hardening form. • The stress-strain curve of the soil containing block ice is represented by a strain-softening model. • The mechanical behaviors of samples containing crushed ice are more sensitive to temperature rise than that of block ice. • A stress threshold value exists when the temperature rise acts as a dominant role affecting the deformation of moraine soil. [ABSTRACT FROM AUTHOR]

The behavior of stabilizing piles with different embedded lengths in bedrock with a hard upper layer and a weak lower layer is examined using physical model tests. Based on the geological model of the landslide with bedrock with a hard upper layer and a weak lower layer, the pile–landslide physical model is developed and includes the data collection system, the pile–landslide model and the loading system. The real-time deformation and moment of the stabilizing pile is obtained in the process of loading at the trailing edge of the landslide for different percentages of hard bedrock. The test results indicate that the percentage of hard bedrock has a strong influence on the deformation and moment of the stabilizing pile embedded in bedrock with a hard upper layer and a weak lower layer. A higher percentage of hard bedrock can result in a greater maximum bending moment of the stabilizing pile and a smaller displacement at the stabilizing pile head, and vice versa. The results also show that 40% of hard bedrock can be considered the critical condition in bedrock with a hard upper layer and a weak lower layer. The percentage of hard bedrock has a limited influence on the deformation of the stabilizing pile when the percentage is greater than 40%. Moreover, four tests with stabilizing piles with different embedded lengths are conducted to investigate the most suitable embedded length in the bedrock with a hard upper layer and a weak lower layer. The results indicate that 28.5 cm is a reasonable embedded length for the stabilizing pile in the two-layered bedrock with a hard rock percentage of 20%. [ABSTRACT FROM AUTHOR]

This paper develops a new method to directly determine the composite elastic modulus of the reinforced con- crete cantilever pile rather than adopt theoretical or empirical approaches. On the basis of the theory of material mecha- nism, the load-deflection equation was deduced to create the relationship between the elastic modulus and the ratio of load-deflection. The numerical modelling tests based on ANSYS separation modelling technology were carried out to determine the composite elastic modulus under different reinforcement ratio, concrete strength grade and distribution pat- tern of driving force. The results can be used to create the quantitative relationship between the composite elastic modulus and reinforcement ratio as well as concrete strength grade. Comparison amongst various lateral load pattern were made to show that the deflection of pile head is obviously affected by the lateral load pattern, and the corresponding equations of the deflection of the pile head under different lateral load pattern were proposed, which can reflect the ranking of the great influence on the deflection of the pile head, rectangular, trapezoidal and triangular lateral load pattern in order. [ABSTRACT FROM PUBLISHER]

The paper presents a novel optimal plane arrangement of stabilizing piles in terms of the provided half simplified flattened ellipsoid model, which can be used to describe the three-dimensional characteristics of sliding mass for colluvial landslides. By studying the friction soil arching effect between the adjacent stabilizing piles, a reasonable pile spacing model for stabilizing piles was deduced in consideration of the driving force and shear strength of sliding mass as well as the dimension of pile cross-section. The results indicate that the net pile spacing is in direct proportion to the height of pile cross-section and shear strength parameters of sliding mass, but in inverse proportion to the driving force intensity. Consequently, the net pile spacing should steadily increase from the major slip profile to the profiles near the boundaries accordingly, which can be called the non-uniformly spaced arrangement principle of stabilizing piles for colluvial landslides. In view of the scale factor and groundwater in the different cross sections of landslide, the improved formula of stability coefficient based on the Fellennius method was proposed accordingly. Furthermore, the concept of stability limit was put forward to confine the rational arrangement region for stabilizing piles; consequently, the region beyond the rational arrangement region is not necessary to set piles any more. The case study of the Erliban landslide in the Three Gorges Reservoir Region of China shows that the quantitative optimal plane arrangement scheme based on the proposed reasonable pile spacing model and stability limit only requires 25 stabilizing piles rather than 31 stabilizing piles in the conventional uniformly spaced arrangement scheme, with an obtainable savings of 19.4% in the number of stabilizing piles. [ABSTRACT FROM AUTHOR]

The Huangtupo landslide is the volumetrically largest, most complex, and economically most significant landslide in the Three Gorges Reservoir Region. Detailed information about the character and dynamics of this tractive landslide is available because of access provided by a unique, 908-meter in situ research tunnel, augmented by long-term data provided by an extensive monitoring system for ground water levels, rainfall, and in situ deformation. Three major rupture surfaces plus 12 interlayer sliding zones (weak layers) were recognized during tunnel excavation, which also provided access and samples that establish a complex, multistage deformation history. Data from the in situ monitoring system shows that the toe of the landslide is creeping at a steady annual rate of about 25-30 mm, but at a slower rate of about 12 mm/year near the crown. However, the monthly creep rates are variable, being highest during May-August when rainfall is heavy and reservoir levels are low. Displacement-depth curves in the HZ6 borehole inclinometer establish that the creep of Slump Mass I# is most rapid above a depth of 37 m, where a major rupture zone occurs immediately above bedrock. Engineered defense structures along the toe of Huangtupo landslide can improve its stability to some extent. The effect of rapid changes of the reservoir level on landslide stability should be considered in reservoir management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of surface models were constructed to study the different behaviors of H 2 S on Co-Cu catalyst surfaces. • The adsorption configurations and properties of related species on three Co-Cu catalyst surfaces were calculated by DFT. • The energy variations in the dissociation of H 2 S on Co-Cu surfaces were studied and compared with that on pure metal. • The factors impacting H 2 S dissociation reaction were explained in terms of adsorption structures, PDOS and Mulliken charge. Co-decorated Cu-based catalysts prepared on the basis of modified Fischer-Tropsch catalysts have high selectivity towards higher alcohols synthesis from syngas. However, H 2 S from syngas can easily deactivate the catalysts containing Co or Cu. In order to explore the interaction between Co-Cu catalyst and H 2 S and to clarify the sulfur poisoning mechanism on this catalyst, the dissociation process of H 2 S and adsorption properties of involved species (H 2 S, HS, S and H) on three surfaces (Cohcp-Cu (1 1 1), Cofcc-Cu (1 1 1) and Co-Cu (2 1 1)) were studied using Density Functional Theory (DFT) calculations. The interactions between S/H and Co are stronger than that Cu. The adsorption energy follows an order of S > HS > H > H 2 S, and the trend of adsorption abilities of three surfaces is Co-Cu (2 1 1) > Cofcc-Cu (1 1 1) ≈ Cohcp-Cu (1 1 1). The dissociation of H 2 S is thermodynamically spontaneous on three surfaces. It was found that the energy barrier of the first dissociation step is lower on Co-Cu (2 1 1) (0.12 eV). The energy barrier of the second dissociation step is relatively high on Co-Cu (2 1 1) (0.53 eV) but extremely low on Cohcp-Cu (1 1 1) (0.01 eV) and Cofcc-Cu (1 1 1) (0 eV). The results show that H 2 S is a bit harder to dissociate on Co-Cu (2 1 1) at low temperature. The difference in the H 2 S dissociation on three surfaces is explained in terms of adsorption configurations, PDOS and Mulliken charge distribution. In general, Co-decorated Cu-based catalyst surfaces are sensitive to H 2 S, which puts forward higher requirements for further improvement in sulfur tolerance of Co-Cu catalysts. [ABSTRACT FROM AUTHOR]

Salinity regulation of the wettability of clay minerals plays an important role in many research fields, but the mechanism influencing the process is not fully understood. Molecular dynamics simulations were used with a NaCl solution and the montmorillonite (Mt) to explore the process by which salinity changes surface wettability. Additionally, the effects of salinity on ionic water cooperation, hydration layer formation, and the hydrogen bond network were analyzed. The results showed that the droplet contact angle increased almost linearly with increasing salt concentration. In an ionic droplet, the oxygen atom of a water molecule moves toward the Na ion and the hydrogen atom moves toward the Cl ion, and the Cl ion has more influence on the droplet structure. There are multiple hydration layers in the droplet, and the ion concentration impacts the hydrogen bond network density more than the water structure density. The main ionic component in the first hydration layer of the ionic droplet is the Cl ion, which changes the direction of the OH bond and leads to a decrease in the hydrogen bond density between the first layer of the water molecule and the hydration layer above, which reduces the adsorption of the Mt. (001) surface charge on the upper water molecule. With an increase in salt ion concentration, the spread range of the first layer of water molecules on the mineral surface is reduced, and ionic hydration results in destruction of the hydrogen bond network of the droplet. Specifically, the connection between hydration layers is weakened, so the adsorption of the upper water on the surface is shielded, leading to an increase in hydrophobicity. This research helps to reveal the mechanism underlying many physical processes or phenomena in nature. [Display omitted] • The contact angle increases almost linearly with the salt concentration. • The anion is the main ionic component in the first hydration layer of the ionic wetting solution. • The deterioration of the hydrogen bond network leads to a larger contact angle. [ABSTRACT FROM AUTHOR]

The salts contained in water can gradually accumulate in pore networks of rocks under wetting-drying cycles, which could cause rock deterioration. The salt-induced damage under this cyclic process can result in dynamically evolving mechanical and hydraulic properties of the rock, which is relevant to many rock-related engineering activities and geological hazards. In this study, the structure damage and permeability evolution of Three Gorges Reservoir (TGR) sandstone subjected to wetting-drying cycles with salt solution were investigated by a series of multiscale experiments. The results showed that the salt solution has a significant impact on the physical properties of TGR sandstone during the wetting-drying process. With increasing wetting-drying cycles, two typical macroscopic damage modes in form of surface peeling and internal cracking were observed. Various physical parameters indicated that the internal structure of the TGR sandstone experienced two stages: 1) Salt accumulation and new crack formation stage and 2) Crack propagation stage. This variation also profoundly affected the permeability of the TGR sandstone. Specifically, the permeability of TGR sandstone decreased slightly at first due to blocked seepage channels by crystals before cycle 5, followed by a slow growth until the 15th cycle and a rapid increase after the 15th cycle. Cubic and exponential functions showed good performances to describe the evolution features of permeability with porosity and wetting-drying cycles, respectively. The deterioration mechanism was further elucidated by an evaporation test. This test indicated that the salt solution was more likely to crystallize in narrow pores and expectedly exert pressure enough to crack the pores, contributing to the structure damage feature and the permeability enhancement. These findings and results in this study deepen our understanding of salt-induced rock deterioration mechanism under the wetting-drying cycles and would be meaningful for rock engineering safety and geological disaster forecast in complex groundwater environments. • Structure damage of TGR sandstone by salt solution under wetting-drying cycles is systematically revealed. • Permeability enhancement of TGR sandstone is functionalized by porosity and wetting-drying cycle. • Salt-induced deterioration mechanism is elucidated by its crystallization features of location and pressure. [ABSTRACT FROM AUTHOR]

Huangtupo landslide, volumetrically the largest, most complex landslide in the Three Gorges Reservoir region of China, is a dangerous mass on which the district of Badong has been inadvertently situated. Risk remediation efforts include the construction of a large observational tunnel and monitoring system that are unique in the world. This tunnel and its side branches permit detailed mapping of its 3D structure while providing samples for laboratory analysis. The new investigations validate that the Huangtupo landslide is a composite of several independent landslides and that movement occurs along the major rupture zones as well as on interlayer sliding zones in the underlying Badong Formation. Uranium-thorium disequilibrium dating establishes that the northern part of the landslide, called the Riverside Slump, underwent at least two periods of movement at about 100 and 40 ka (ka stands for a thousand years). These events were induced by the steep slope created by the downcutting of the Yangzte River. The results from in situ displacement monitoring over a 7-year period confirm that the central part of the landslide is creeping at a slow, relatively stable rate of about 15 mm/year rather than being in a stage of acceleration under the protection of anchored concrete beams and other defense structures at its toe. Available data suggest that engineering measures can control the independent landslides that together constitute the huge Huangtupo mass, which will avoid the need for costly relocation of thousands of people. [ABSTRACT FROM AUTHOR]

In recent years, a large number of bank destruction occur in the reservoir area under the effect of water fluctuation, which may be lead to reservoir accumulative landslide geological hazards finally. The paper conducted the bank destruction forecasting study for accumulative landslides in the Three Gorges Reservoir Region, China utilizing back-propagation (BP) neural network approach. A representative scenario of Jinle landslide is then taken for analysis purposes. On the basis of the existing data sets of bank destruction cases, the BP neural network forecasting model and the corresponding programs for bank destruction are both presented, whose forecasting result is validated by two independent approaches, namely empirical method and numerical modeling method. Furthermore, the BP neural network model had obvious advantages over the convention approaches in the aspects of the fast calculation speed and high convenience. According to the bank destruction forecasting scale presented above, the corresponding revetment measures can be proposed to prevent the occurring of the bank destruction, whose effectiveness has been further validated by the actual engineering practice. [ABSTRACT FROM AUTHOR]

The model outcomes plotted as maps are a key factor in land planning and flood management. Abdelkarim et al. [[5]] cope with the issue of irregular flooding in dry and semiarid environments according to a case study in the city of Qurayyat in the Kingdom of Saudi Arabia. After the constructions of landslide flow models, the three case studies are explained in detail, and management and mitigation strategies are hypothesized and explained. [Extracted from the article]

Rainfall reservoir-induced landslides in the Zigui Basin, China Three Gorges Reservoir (CTGR) area, exhibit typical step-like deformation characteristics with mutation and creep states. Previous landslide displacement forecasting models yielded low prediction accuracy especially for mutational displacements. Coupled with the lack of monitoring sites and data limitations, it is extremely difficult to obtain accurate and reliable early warnings for landslides. The multi-feature fusion transfer learning (MFTL) method proposed in this paper applies the knowledge and skills obtained from the Baijiabao landslide scenario and sufficient monitoring data to improve the prediction capacity for other landslides, such as the Bazimen and Baishuihe landslides. The model barely relies on the long-time continuous monitoring process, and it can not only fill gaps in data when monitoring is interrupted, but also provide real-time displacement predictions based on accurate weather forecasting and periodic reservoir scheduling. In addition, the non-uniform weight error (NWE) evaluation method is proposed in this paper to focus more on the mutation state prediction accuracy because landslide instability is most likely to occur in this stage. Compared with other intelligent algorithms, the results indicate that the MFTL method owns low prediction error and high reliability, as well as the positive generalization ability in landslide prediction. This study paves the potential way for realizing the real-time, whole-process and accurate landslide forecasting. • An innovative model based on Transfer Learning method is firstly applied in landslide displacement prediction. • The model barely relies on long-time continuous monitoring dataset and it can fill data gaps due to monitoring interruptions. • The model is evaluated by three representative landslides with GPS monitoring datasets in Three Gorges Reservoir area, China. • The model owns low prediction error, high reliability and positive generalization ability in landslide prediction. • This study paves the potential way for realizing the real-time, whole-process and accurate landslide forecasting. [ABSTRACT FROM AUTHOR]