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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]

Estimation of the uncertainties of geotechnical parameters is a fundamental task in slope reliability analysis, and it becomes more challenging when only limited data on geotechnical parameters are available. In this study, a Bayesian bootstrap-Copula coupled method is proposed for slope reliability analysis based on limited geotechnical data. Specifically, the bivariate distribution of shear strength parameters ((cohesion (c) and friction angle (φ)) can be evaluated using the Bayesian bootstrap method and Copula theory, and then the slope reliability can be calculated using Monte Carlo simulation (MCS). Application to a homogeneous, undrained cohesive slope demonstrates the accuracy and effectiveness of the proposed approach. The results indicate that even when data are limited, the bivariate distribution of c and φ can be determined and the estimated statistics met the predefined ones well. Satisfying estimations of the mean (μFS\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\mu }_{FS}$$\end{document}) and standard deviation (σFS\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\sigma }_{FS}$$\end{document}) of the factor of safety (FS) and failure probability (Pf) can be obtained. The representative sliding surface with the greatest likelihood is found to approximate the critical one based on the mean values of c and φ. Besides, when the available sample size of geotechnical data exceeds a threshold, stable estimations of the bivariate distribution of c and φ can be obtained, and the estimated μFS\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\mu }_{FS}$$\end{document} is stable, while the values of σFS\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\sigma }_{FS}$$\end{document} and Pf synchronously vary within a small range. Applications of the proposed Bayesian bootstrap-Copula coupled method indicate that it can be used to estimate the bivariate distribution of correlated parameters and the reliability of various geotechnical problems based on limited data. [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]

Rainfall represents one of the most significant cause of landslide hazards. With runoff in the saturated zone of shallow soil considered, an improved Green–Ampt model was proposed to depict the rainfall infiltration process. Furthermore, a formula for calculating the depth of wetting front was derived, and the slope stability was evaluated accordingly. Finally, a formula for calculating the safety factor of multilayer slopes above different surfaces was obtained via the limit equilibrium method. An illustration is a multilayer colluvial slope in Guangdong Province of China, the results indicated that the downward speed of wetting front decreases gradually within the same layer with continuous rainfall but increases significantly when it extends to the interfaces between the soil layers. Safety factor of the slope decreases sharply at the initial stage of rainfall but then more slowly. Slope failure is more likely to occur along the first interface between the soil layers than along the surface of wetting front. The result from the proposed model is closer to the result of the physical model test than from the existed Green–Ampt model. The improved Green–Ampt model for multilayer slopes can accurately evaluate the infiltration process and related stability of multilayer slopes under rainfall. [ABSTRACT FROM AUTHOR]

Monitoring data show that many landslides in the Three Gorges region, China, undergo step-like displacements in response to the managed, quasi-sinusoidal annual variations in reservoir level. This behavior is consistent with motion initiating when the reservoir water level falls below a critical level that is intrinsic to each landslide, with the subsequent displacement rate of the landslide being proportional to the water depth below that critical level. Most motion terminates when the water level rises back above the critical level, so the annual step size is the time integral of the instantaneous displacement rate. These responses are incorporated into a differential equation that is easily calibrated with monitoring data, allowing prediction of landslide movement from actual or anticipated reservoir level changes. Model successes include (1) initiation and termination of the annual sliding steps at the critical reservoir level, producing a series of steps; (2) prediction of variable step size, year to year; and (3) approximate prediction of the shape and size of each annual step. Annual rainfall correlates poorly with step size, probably because its effect on groundwater levels is dwarfed by the 30 m annual variations in the level of the Three Gorges Reservoir. Viscous landslide behavior is suggested. [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]

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]

Sand layer sampling is important in water conservancy and hydropower exploration, and the accurate identification of sand layers is the premise for foundation design and treatment. In this study, a new method for identifying sand layers based on key drilling parameters was proposed. Simulated formation laboratory experiments using a self-developed measurement-while-drilling system were first conducted to study the relationships between four drilling parameters and sand layers. Quantitative criteria based on key drilling parameters for sand layer identification were then proposed, followed by validation through three engineering projects. The results showed that bit pressure and drilling speed are sensitive to formation changes and can be used for sand layer identification. Specifically, in sand layers, the variation ratio of drilling speed is more than 150% and the variation ratio of bit pressure is less than 200%. Applications of the proposed method in Na water conservancy project, Sancha water conservancy project, and Tuodan reservoir project show satisfying accuracy, indicating that it can be used as an effective tool for sand layer identification in various engineering projects. [ABSTRACT FROM AUTHOR]

Sand layer sampling is important in water conservancy and hydropower exploration, and the accurate identification of sand layers is the premise for foundation design and treatment. In this study, a new method for identifying sand layers based on key drilling parameters was proposed. Simulated formation laboratory experiments using a self-developed measurement-while-drilling system were first conducted to study the relationships between four drilling parameters and sand layers. Quantitative criteria based on key drilling parameters for sand layer identification were then proposed, followed by validation through three engineering projects. The results showed that bit pressure and drilling speed are sensitive to formation changes and can be used for sand layer identification. Specifically, in sand layers, the variation ratio of drilling speed is more than 150% and the variation ratio of bit pressure is less than 200%. Applications of the proposed method in Na water conservancy project, Sancha water conservancy project, and Tuodan reservoir project show satisfying accuracy, indicating that it can be used as an effective tool for sand layer identification in various engineering projects. [ABSTRACT FROM AUTHOR]

As one of China′s most precious cultural relics, the excavation and protection of the Terracotta Warriors pose significant challenges to archaeologists. A fairly common situation in the excavation is that the Terracotta Warriors are mostly found in the form of fragments, and manual reassembly among numerous fragments is laborious and time-consuming. This work presents a fracture-surface-based reassembling method, which is composed of SiamesePointNet, principal component analysis (PCA), and deep closest point (DCP), and is named SPPD. Firstly, SiamesePointNet is proposed to determine whether a pair of point clouds of 3D Terracotta Warrior fragments can be reassembled. Then, a coarse-to-fine registration method based on PCA and DCP is proposed to register the two fragments into a reassembled one. The above two steps iterate until the termination condition is met. A series of experiments on real-world examples are conducted, and the results demonstrate that the proposed method performs better than the conventional reassembling methods. We hope this work can provide a valuable tool for the virtual restoration of three-dimension cultural heritage artifacts. [ABSTRACT FROM AUTHOR]

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]

• A modified Bayesian sequential updating approach is proposed to estimate GSI. • Multi-source information can be integrated in the approach. • GSI can be estimated using limited data based on various rock mass classifications. • Evaluated probabilistic characteristics of the GSI agree with the observed GSI data. • Rational result is achieved by taking model uncertainties as random normal variables. Explicit determination of geotechnical parameters is an important but difficult task in rock engineering. Paradoxically, data are often limited even though data from multiple sources (e.g., different testing procedures, testing positions, and estimation models) are commonly available, and the integration of multi-source information for the determination of geotechnical parameters in a probabilistic context remains a great challenge. We have modified an existing Bayesian sequential updating approach and used it for the first time to estimate the geological strength index (GSI) of rock masses by integrating multi-source information in a way that considers prior information, multiple estimation models and probabilistic properties of model uncertainties. The argillaceous siltstone in Zigui County in the Three Gorges Reservoir region of China was used to quantitatively illustrate this method. Three data sets using rock mass rating (RMR)-, tunneling quality index (Q)-, and rock mass index (RMi)-based estimation models were sequentially incorporated into the Bayesian sequential updating framework, through which the information on the mean value and standard deviation of the GSI can be updated. Then a large number of equivalent GSI samples were generated through Markov chain Monte Carlo (MCMC) simulation for further statistical analysis. The results showed that the proposed Bayesian sequential updating approach can provide reasonable probabilistic estimates of the GSI, which compared well with observed data using the standard GSI chart. The Bayesian sequential updating approach is a promising tool for geotechnical parameter estimation and can combine large amounts of information, thereby effectively depicting the probabilistic characteristics of GSI. [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]

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]

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]

Highlights: A novel BAS-DNN model for prediction of TBM advance rate is developed. A database involving geotechnical and operating risks (RMR, TWCR, and RI) is set up. Quadratic relationships exist between RMR, TWCR, and AR. AR decreases while the descending rate gradually increases with RI increasing. The BAS-DNN model shows good performance in the tunnel section with a jamming event. [ABSTRACT FROM AUTHOR]

Based on the machine learning algorithms, prediction models for landslide displacement with step-like behavior in the reservoir area were established for landslides prevention and reduction; these models could predict a given test set very well. However, due to the length and the sequence of the training set in prediction models, the predictive ability of these prediction models could not be evaluated accurately if just validated with a given test set. To solve the problem, a hybrid reliability model was proposed. Complimentary ensemble empirical mode decomposition (CEEMD) algorithm was used to decompose the accumulated displacement into the trend displacement and the periodic displacement firstly. The Gauss function was used to predict the trend displacement, and the random forest (RF) and back propagation neural network (BPNN) algorithms were employed to predict the periodic displacement. Furthermore, a novel performance function for the reliability analysis of the displacement prediction model was derived to address failure probabilities in different cases. The Baijiabao landslide in the Three Gorges Reservoir Area was taken as an example for reliability analysis of the prediction model for landslide displacement with step-like behavior, and the predictive ability of the CEEMD-RF model and the CEEMD-BPNN model were compared. The results indicated that the CEEMD-RF model and CEEMD-BPNN model both can accurately predict the accumulated displacement of the given test set; the predictive value obtained with the CEEMD-RF model or the CEEMD-BPNN model showed uncertainties of the prediction model for landslide displacement and the predictive ability of the CEEMD-RF model was more reliable than the CEEMD-BPNN model under different cases. The failure probability proposed in the paper could evaluate the predictive ability of the model more accurately and comprehensively compared with the existing assessment indices. [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]

Most soft interlayers tend to be key factors affecting rock slope stability due to their low strengths. A series of ring shear tests is conducted on reconstituted overconsolidated soft interlayers to investigate the influences of remolded water content and normal stress on shear behavior under drained conditions. The soft interlayer raw samples taken from a potential landslide site in China are first remolded into overconsolidated samples with different water contents but the same dry density and further drained under different normal stresses. The peak strength, residual strength, corresponding shear displacement of the soft interlayers and the loss rate of water content are positively correlated with water content and normal stress. Transformation of strain softening to strain hardening occurs for samples under higher normal stresses. Variations in water contents have notable effects on the shear strengths. Meanwhile, displacements, fragmentations and orientations of samples differ, showing strain softening and hardening behaviors of soft interlayers. • Stress-strain characteristics of soft interlayers are systematically investigated. • Ring shear test is utilized successfully for shear behavior studying. • Variation in compaction moisture content has an obvious effect on shear strength. • Shear behaviors are closely related to the microstructure of soft interlayers. [ABSTRACT FROM AUTHOR]

Background: At present, the predictive ability of the prognostic indicator of hepatocellular carcinoma (HCC) is still limited. This study aims to analyze the relationship between the preoperative high-sensitivity C-reactive protein to lymphocyte ratio (HCLR) and the clinicopathologic characteristics of HCC. Patients and methods: A total of 229 HCC patients undergoing surgical resection were retrospectively analyzed. The majority of the patients (132/229) had tumors larger than 5 cm, and 45 out of 229 had more than one tumor focus. Receiver operating characteristic curve analysis was used to decide the cutoff value of HCLR. The overall survival (OS) and progression-free survival (PFS) rates were evaluated by adopting the Kaplan–Meier method. Results: The cutoff value of HCLR for the best discrimination of HCC prognosis was 1.3 with a sensitivity of 75.5% and a specificity of 71.8%. The area under the receiver operating characteristic curve was 0.791 (95% CI, 0.731–0.840). Preoperative HCLR at a high level (>1.3) was positively correlated with large tumor size, TNM stage, microvascular invasion, and recurrence. The mean OS and PFS in patients with HCLR >1.3 were significantly shorter than in those with HCLR ≤1.3. Univariate and multivariate analyses revealed the HCLR was an independent predictor of OS and PFS. Conclusion: HCLR was an important independent predictor of dismal prognosis in HCC patients and can be used as a sensitive indicator for the dynamic monitoring of postoperative patients. [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]

The construction of the huge Three Gorges reservoir affected a large region, and the resultant geological and environmental impacts have caused global concern. The remarkable, 30-m annual fluctuation in the reservoir water level poses a significant threat to slope stability in this area. Four hundred sixty-two landslides were identified in the Zigui basin using historical records, satellite images, field investigations and unmanned aerial vehicle (UAV) observations, enabling the construction of a complete landslide database and distribution map. Three failure modes of landslides in the Zigui basin are used to illustrate the major factors that govern reservoir-induced landslides. The results show that (1) > 99% of identified landslides occur on slopes angle <47°, while >80% occur at elevations below 600 m; (2) Jurassic Niejiashan Formation is highly prone to landslides; (3) Low reservoir levels of 145 m to 155 m greatly reduce slope stability. Based on the information entropy method that use the conditional probability of different influencing factors and principal component analysis as inputs, the relative contributions of various influencing factors are quantified and a landslide susceptibility map was drawn. This susceptibility map helps define the countermeasures that will best reduce fatalities and property losses for areas having different landslide conditions and susceptibilities. • Database of 462 reservoir-induced landslides in Zigui basin, TGR was created. • Identifying failure modes and quantifying contributions of influential factors. • Conditional probability and information entropy model yields landslide susceptibility. • Susceptibility map, failure modes, and strategies suppressing the slope instability. [ABSTRACT FROM AUTHOR]