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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]

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]

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]

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]

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]

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]

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]

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]

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]

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 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]

A correction is presented to the article "Clinical analysis of second trimester pregnancy termination after previous caesarean delivery in 51 patients with placenta previa and placenta accreta spectrum."

Objective: Allogeneic transplantation with umbilical cord blood (UCB) in adult recipients is limited mainly by a low CD34+ cell dose. To overcome this shortcoming, human placenta as a novel source of human mesenchymal progenitor cell (MPC) was incorporated in an attempt to expand CD34+ cells from UCB in vitro.Materials and methods: Human placenta MPC was isolated and characterized by morphologic, immunophenotypical, and functional analysis. UCB CD34+ cells were expanded by coculture with placental MPC. Suitable aliquots of cells were used to monitor cell production, clonogenic activity, and long-term culture-initiating culture (LTC-IC) output. Finally, the immunoregulatory effect of placental MPC was evaluated by T-cell proliferation assay.Results: In its undifferentiated state, placental MPC displayed fibroblastoid morphology; was CD73, CD105, CD29, CD44, HLA-ABC, and CD166 positive; produced fibronectin, laminin, and vimentin; but was negative for CD14, CD31, CD34, CD45, HLA-DR, and α-smooth muscle actin. Functionally, it could be induced into adipocytes, osteocytes, and chondrocytes. In vitro expansion of UCB hematopoietic cells, when cocultured with placental MPC in the presence of cytokines, was significantly enhanced: CD34+ cells by 14.89 ± 2.32 fold; colony-forming cell (CFC) by 36.73 ± 5.79 fold; and LTC-IC by 7.43 ± 2.66 fold. Moreover, placental MPC could suppress T-cell proliferation induced by cellular stimuli.Conclusion: These results strongly suggest that human placental MPC may be a suitable feeder layer for expansion of hematopoietic progenitors from UCB in vitro. [Copyright &y& Elsevier]

Five large and many small landslides are developed in Jurassic strata along the lower reaches of Xiangxi River, where interbedded weak and hard bedrock layers foster the development of landslides with a "stair-step" sliding surface. The paper investigates the evolution characteristics of these landslides and presents a novel forecasting model for their displacements. The distribution characteristics and behavior of landslides developed along Xiangxi River is revealed by the database of landslides in the larger Zigui basin, of which this area is part. Most landslides occur at rather low elevations of <300 m and in areas of moderate rainfall. The geological evolution of landslides in the Xiangxi River valley can be divided into four stages, beginning with anticline formation, followed by valley incision, then by weathering and erosion, and culminating in formation of the colluvial landslides. The accumulative displacement curves of landslides with a stair-step sliding surface in Xiangxi River region also present obvious, step-like characteristics. A novel GA-CEEMD-RF algorithm was developed to predict the displacement of these stair-step landslides, which helps to define the combination of induced factors and weak stableness of prediction results using a single displacement prediction model and the multi-field monitoring data. • The distribution characteristics of landslides developed along lower reaches of Xiangxi River was revealed. • Interbedded weak and hard bedrock layers foster the development of landslides with a "stair-step" sliding surface. • The geological evolution of landslides in the Xiangxi River valley can be divided into four stages. • A novel GA-CEEMD-RF algorithm was developed to predict the displacement of stair-step landslides. [ABSTRACT FROM AUTHOR]

Bentonite, used as a barrier material in landfill systems and the geological disposal of radioactive waste, undergoes various processes such as the cation exchange with landfill leachate and repository groundwater, desiccation shrinkage due to heat released from solid waste or nuclide decay. In the context of these engineering applications, it is crucial to consider the effect of interlayer cation composition on the desiccation-shrinkage behavior of bentonite for assessing the long-term performance of barrier systems. This study investigates this impact by conducting desiccation tests on four different cation-type bentonite samples (i.e., K-, Na-, Ca-, and Mg-bentonite) and elucidating the underlying mechanisms through mercury intrusion porosimetry test, X-ray diffraction analysis, and suction measurements. The results indicate that K-bentonite exhibits the highest water evaporation rate and the lowest shrinkage potential, with no shrinkage cracks detected, and that Na-bentonite evaporates water at a relatively fast rate but presents the most pronounced volumetric shrinkage. In contrast, Ca- and Mg-bentonite have the highest water-retention capacity, and their shrinkage potentials are less than Na-bentonite. An improved shrinkage model is proposed, which is shown to describe the measured shrinkage curves for four types of homoionic bentonite samples. Additionally, the mechanism behind the effect of different interlayer cations was interpreted in terms of the interlayer–cation–water interaction, pore structure evolution, and soil suction variation. [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]

Due to the complex and non-linear characteristics of landslide evolution, the deformation law of landslides is always hard to be predicted. Considering the dynamical evolution process of landslide physical mechanism, a Physics-Informed Data Assimilation (PIDA) method is first proposed for landslide displacement forecasting. It can enhance the prediction ability of the physical forecasting model, and solves the problem of ignoring the physical significance of landslides in mathematical prediction model. Additionally, the superiority of Particle Filter (PF) in nonlinear and non-Gaussian system determines its application in complex problem. Aiming at the hydrodynamic pressure-driven landslide, the Sliding Zone Deterioration (SZD) model is constructed as the state equation of the PF algorithm. And the observation equation is formed by the relationship between landslide deformation and monitoring datasets. The physics-informed landslide displacement prediction model serves as a bridge, consisting of the shear strength parameter dynamic updated model and physical mechanism analysis model, for key parameters feedback, modification, and update. Comparing the results to traditional Long Short-Term Memory (LSTM) and Back Propagation Neural Network (BPNN) methods, the PIDA method combining triggering and instability mechanisms performs better in accuracy. Moreover, it enables dynamic and reliable landslide deformation prediction. [ABSTRACT FROM AUTHOR]

The Zigui basin is one of the most landslide-prone areas where thousands of landslides are distributed. Performing the landslide susceptibility mapping is a heated issue in the area. Whereas, whether the random selection of the landslides or non-landslides grid cells are reasonable in research of landslide susceptibility mapping is the existence problem nowadays. Based on the two step cluster (TSC) algorithm and the self-organizing mapping - random forest (SOM-RF) model, a novel hybrid model is proposed to overcome the above drawbacks in this study. Rough set (RS) theory is employed as an attribute reduction tool to identify the significant influencing factors of landslides, and SOM is used to produce a preliminary landslide susceptibility mapping. Two step cluster algorithm is applied in telling apart the most reasonable True-Positive (TP) from landslide grid cells in high-susceptibility zones and the False-Positive (FP) in low-susceptibility zones. Afterwards, the TP and FP are imported into the RF model as samples to produce the improved landslide susceptibility mapping. The proposed method is utilized to develop landslide susceptibility mapping in the Zigui basin. Compared with the susceptibility mapping produced by RF model, which selects landslides and non-landslides grid cells randomly, the results of TSC and SOM-RF model demonstrates to have the superior prediction skill and higher reliability in landslides susceptibility mapping. [ABSTRACT FROM AUTHOR]

[Display omitted] • The desorption process with low temperature using pure ethylene as desorption gas for 3A zeolite drying device regeneration is proposed. • Adsorption of ethylene on the surface of 3A zeolite was investigated. • The polymerization network of ethylene on the surface of 3A zeolite were constructed. • The reaction properties of ethylene on the surface of 3A zeolite were studied by the combination of Density functional theory (DFT) and kinetic Monte Carlo (kMC). • Ethylene begins to polymerize to form polymerization species, which cover the surface and reduce the dehydration performance of 3A zeolite when the temperature is higher than 473 K. Separation is the core process of ethylene production, in which the reaction gas is usually dried using 3A zeolite. In this work, ethylene polymerization on the surface of 3A zeolite were investigated by the combination of Density Functional Theory (DFT) and kinetic Monte Carlo (kMC). DFT calculations showed that stepwise mechanism is the dominant path of ethylene dimerization on the surface of 3A zeolite. Then the effect of temperature on the polymerization of ethylene was studied by kMC simulation. When the temperature is higher than 473 K, ethylene begins to polymerize to form corresponding species, which cover the surface and reduce the dehydration performance of 3A zeolite. Based on these, the desorption process with low temperature using pure ethylene as desorption gas for 3A zeolite regeneration is proposed, which can avoid the use of N 2 , and reduce the equipment investment and energy consumption. [ABSTRACT FROM AUTHOR]

This paper presents a new framework for characterizing landslide deformation. Here, the deformation of a landslide is interpreted as a summation of three components: rigid deformation, within-mass deformation, and residual deformation. On the basis of the monitored data of the landslide deformation, these three components may be characterized separately: the rigid deformation is simulated by a summation of a trend term and a periodic term, the within-mass deformation is simulated by a high-order polynomial model, and the residual deformation is simulated by a conditional random field model. In particular, the characterization of the residual deformation, the third component of the landslide deformation, with the random field allows for a probabilistic assessment of the landslide deformation in the face of geological uncertainties. With the proposed framework, the evolution of landslide deformation in both geometric and time domains may be established, which allows for an assessment of the sliding mechanism of the landslide. Further, evolution in the geometric domain may allow for an assessment of the serviceability of infrastructures in the landslide area. To illustrate this new landslide deformation characterization framework, a case study of the Yu-Kai highway landslide in Guizhou, China is presented, through which the effectiveness of the proposed framework is demonstrated. [ABSTRACT FROM AUTHOR]

Fluid flow in rock fractures is described by Darcy's law and its nonlinear extension, the Forchheimer equation in form of a quadratic polynomial. Since the nonlinearity of the Forchheimer equation, determining its key coefficient of inertial permeability (i.e., the quadratic coefficient representing inertial losses) requires a series of flow tests under different hydraulic gradients. However, how to choose the volumetric flux range for deriving inertial permeability is never scrutinized. Here we report a seemly irrational dependency of inertial permeability on volumetric flux range by massive direct numerical simulations of fluid flow in rock fractures. This variation presents traceability and is closely related to the evolution of microscale eddies and macroscale flow regimes. A concept of global inertial permeability is thus proposed from this traceable variation, which can reproduce the whole flow regime in rock fractures. Two parametrized criterion models are subsequently established for calculating global inertial permeability using the lowest cost and ensuring its accuracy: one in terms of minimum Reynolds number for practical purposes, and the other in terms of minimum eddy volume ratio for mechanistic interpretation. Further discussions indicate that the proposed global inertial permeability is of great importance to non-Darcian flow prediction and flow regime assessment. Moreover, the parameterized criterion models in the form of power-law function for determining global inertial permeability, drawn from 2D fracture simulations, can apply to 3D fractures and large-scale fractured rock aquifers. The findings and results in this study are of great significance for accurately evaluating the hydraulic conductivity of rock fractures, especially at relatively high flow rates, and are useful for many geophysical and industrial applications. • Variation of inertial permeability with flow ranges is manifested which results from evolving eddies and flow regime. • Global inertial permeability referring to stable value of the variation is proposed to reproduce the whole flow regime. • Practical and mechanistic criterion models for determining global inertial permeability are both established. [ABSTRACT FROM AUTHOR]

Abstract To synthesize small and evenly distributed fillers in polymer matrix is important to fulfill the advantage of nanocomposite membranes in overcoming the tradeoff effect between permeability and selectivity. In this study, nanocomposite membranes were prepared by synthesizing calcium oxalate (CaOx) nanoparticles in confined space of the layer-by-layer (LbL) self-assembled polymer network through bio-inspired mineralization. The active layer was tightly coated on hydrolyzed polyacrylonitrile substrate with thickness less than 200 nm. The CaOx nanoparticles were uniformly distributed in the polymer matrix with diameter less than 50 nm. The hydrophilicity of the nanocomposite membranes was decreased due to the incorporation of CaOx nanoparticles. And the free volume properties were tuned by creating new polymer/filler interface. At precursor concentration of 1 mM, the permeation flux increased by 14% to 958 g/(m2h), the separation factor increased by 2.36 times to 1562 compared to the control membrane, and the membrane showed good operating stability. Graphical abstract fx1 Highlights • Ultrathin nanocomposite membranes were prepared based on LbL self-assembly. • CaOx was in situ synthesized in confined space of polymer via biomineralization. • The nanocomposite membrane showed good performance in ethanol dehydration. • The nanocomposite membrane showed good operating stability. [ABSTRACT FROM AUTHOR]

The physical model test of landslides is important for studying landslide structural damage, and parameter measurement is key in this process. To meet the measurement requirements for deep displacement in landslide physical models, an automatic flexible inclinometer probe with good coupling and large deformation capacity was designed. The flexible inclinometer probe consists of several gravity acceleration sensing units that are protected and positioned by silicon encapsulation, all the units are connected to a 485-comunication bus. By sensing the two-axis tilt angle, the direction and magnitude of the displacement for a measurement unit can be calculated, then the overall displacement is accumulated according to all units, integrated from bottom to top in turn. In the conversion from angle to displacement, two spline interpolation methods are introduced to correct and resample the data; one is to interpolate the displacement after conversion, and the other is to interpolate the angle before conversion; compared with the result read from checkered paper, the latter is proved to have a better effect, with an additional condition that the displacement curve move up half the length of the unit. The flexible inclinometer is verified with respect to its principle and arrangement by a laboratory physical model test, and the test results are highly consistent with the actual deformation of the landslide model. [ABSTRACT FROM AUTHOR]

The vibration deterioration of discontinuities with different joint wall material (DDJM) plays a vital role in the seismic behavior of soft and hard interbedded rock slopes under earthquake; however, too little work has been devoted to the subject due to lack of attention. In the present study, the seismic behavior of soft and hard interbedded rock slopes considering the vibration deterioration of DDJM was studied by taking the Shaba slope in China as a study case. A mathematical model quantitatively describing the strength deterioration of DDJM under strong earthquakes was established based on the results of the cyclic shear test, and the deterioration process was implemented by the FISH programming language in numerical software 3DEC. The deformation characteristics and supporting effects of the Shaba slope with the deterioration model were analyzed under seismic loads with different intensities. The results show that the maximum permanent displacements of the Shaba slope without supports obviously rise with the enlargement of seismic loads. Compared with results without considering the vibration deterioration of DDJM, the difference of maximum permanent displacements increases from 15 to 39.7% under seismic loads with intensities from VI to VIII degree. The existing supporting measures on the Shaba slope can not withstand the seismic load with intensities above VI degree and need to be optimized to prevent earthquake-induced disasters in the future. [ABSTRACT FROM AUTHOR]

Abstract Covalent organic framework (COF) is an emergent class of ordered porous materials with high stability. The fabrication of thin and continuous COF membrane for small molecule separation remains challenging due to the relatively large pore size of COF materials and weak COF-substrate interfacial interaction. Herein, a two-dimensional COF layer was spin-coated on a porous substrate followed by constructing a bio-inspired calcium alginate (Alg-Ca) layer to obtain a dual-layer membrane with a thickness less than 100 nm. The Alg-Ca layer afforded a superhydrophilic surface to capture water molecules, and the porous COF layer rendered selective water channels. The dual-layer membrane synergistically strenthened the solution-diffusion mechanism through the manipulation of the membrane structure and transport process. The synergy of two layers endowed the membrane with superior water-selective performance with permeation flux of 3614 g/(m2h) and water content in permeate of 99.7 wt% for n -butanol dehydration. The fabrication of dual-layer membrane in this study may offer a new strategy for highly efficient separation of liquid small molecule mixtures. Graphical abstract fx1 Highlights • Ultrathin dual-layer membrane was prepared with a polymer layer and a COF layer. • Superhydrophilic surface was obtained for the dual-layer membrane. • The dual-layer membrane showed excellent performance in n -butanol dehydration. • The dual-layer membrane showed good operating stability. [ABSTRACT FROM AUTHOR]

Previous determinations of the optimal stabilizing pile location have generally been based on the idealized assumption of arc-shaped sliding surfaces. This assumption, however, may be inconsistent with the actual situation of most common irregular shapes, such as the step shape; as a result, determinations based on this assumption tend to involve considerable error. This paper presents a strategy, termed the local safety partitioning (LSP) methodology, for accurately determining optimal pile locations for step-shaped configurations. Instead of assuming the sliding surface to be arc-shaped, this strategy considers the actual sliding shapes. A new index termed the local safety factor is introduced for measuring the stabilities of local landslide masses, and this method employs the Swedish slice method to calculate the value of the index. The LSP methodology consists of four procedures: slicing the landslide mass into blocks, calculating the local safety factor of each sliced block, dividing the landslide mass into local partitions based on the previous step, and identifying the optimum pile position using previously identified partitions. The performance of the presented methodology is illustrated using the Jinle No. 2 landslide case for well-rounded demonstration and using the Yancun landslide case for additional validation. The results indicate that analysis of a reinforced landslide employing the LSP methodology acquires the largest safety factor and smallest deflection, shear force and bending moment on the pile body compared with any other case from a series of positions that incorporate traditional positions for arc-shaped sliding surfaces. The presented methodology provides a simple but accurate determination of the optimal stabilizing pile location for stepped sliding surfaces, although it may involve errors and unexpected limitations when applied to arc shapes and peculiar scenarios. [ABSTRACT FROM AUTHOR]

Objective: To estimate the association between uterine fibroids and adverse obstetric outcomes. Methods: This was a retrospective cross-sectional study of 112,403 deliveries from 14 provinces and 39 different hospitals in 2011 in mainland China. We compared pregnancy outcomes in women with and without uterine fibroids who underwent detailed second trimester obstetric ultrasonography during 18 to 22 weeks. Obstetric outcomes include cesarean delivery, breech presentation, preterm delivery, placenta previa, placental abruption, premature rupture of membranes and neonatal birthweight. Univariate analyses and multivariate logistic regression analyses were performed. Results: Of 112,403 women who underwent routine obstetric survey, 3,012 (2.68%) women were identified with at least 1 fibroid. By univariate and multivariate analyses, the presence of uterine fibroids was significantly associated with cesarean delivery (Adjusted odds radio [AOR] 1.8, 95% confidence interval [CI] 1.7–2.0), breech presentation (AOR 1.3, 95% CI 1.2–1.5) and postpartum hemorrhage (AOR 1.2, 95% CI 1.1–1.4). The size of uterine fibroids and location in uterus had important effect on the mode of delivery. The rates of PPH were significantly higher with increasing size of the uterine fibroid (P<0.001). And the location of fibroid (intramural, submucosal or subserosal) also have a statistically significant impact on the risk of PPH (5.6% [subserosal] vs 4.7% [submucosal] vs 8.6% [intramural]). Conclusion: Pregnant women with uterine fibroids are at increased risk for cesarean delivery, breech presentation and postpartum hemorrhage. And different characteristics of uterine fibroids affect obstetric outcomes through different ways. Such detailed information may be useful in risk-stratifying pregnant women with fibroids. [ABSTRACT FROM AUTHOR]

The influence of wetting and drying cycles (WDC) on the strength weakening of typical rocks in soft and hard interbedded rock masses is vital to comprehend the mechanism of numerous bank slope failures in soft and hard interbedded strata induced by water level fluctuations. How WDC affect the strength of intact rocks in red stratum of the Badong Formation, a typical sliding-prone interbedded stratum in the Three Gorges area, is a topic worthy of comprehensive investigation. In this study, the effects of WDC on the physical and strength parameters of silty mudstone and silty sandstone were examined by performing a series of experiments on a total of 116 rock samples. Models of strength weakening were developed for the two rock types to express the relations between the strength deterioration coefficient (ratio of the weakened and initial value of strength parameters) and the number of WDC. The results indicate that treatment with WDC causes increases in the water absorption rate, and decreases in longitudinal wave velocity, tensile strength, cohesion and internal friction angle for both silty mudstone and silty sandstone samples with the rate of change decreasing with an increasing number of WDC; the variations in physical and strength parameters are larger for silty mudstone compared with silty sandstone; the effects of WDC on tensile strength and cohesion are higher than on internal friction angle for the studied rock types; Intergranular cracks and intragranular cracks were observed to increase with the number of WDC, evolution mode of rock microstructures was proposed, and the main weakening mechanisms induced by WDC was summarized as microcracks growth by mineral expansion and contraction, which weaken the strength of the studied rocks with the impact depending mainly on the mineral contents and microstructures in rocks. Finally, the established strength weakening models were applied in the numerical model to investigate the influence of WDC on the strength of rock mass with silty mudstone and silty sandstone interbedded layers in the Badong Formation. The obtained results provide useful guidance to reasonably evaluate the long-term stability of soft and hard interbedded bank slopes in reservoir area. • Typical rocks in a interbedded red stratum were sampled from the field. • Experiments were performed on 116 rock samples under wetting and drying cycles. • Effect on tensile strength and cohesion are higher than on internal friction angle. • Mineral expansion, contraction and dissolution induces weakening of rocks. • The test data were used to study strength weakening of interbedded rock mass. [ABSTRACT FROM AUTHOR]

The mechanical behavior of in situ sliding zone soil is unique and is significant for the state identification and prediction of landslides. This study focuses on interpreting the anisotropic deformation observed on the sliding zone soil of the Huangtupo landslide during an in situ triaxial creep test; specifically, the deformation of the A-Surface (towards 35° dip direction) of the soil cube, which points approximately to the landslide sliding orientation, is significantly large. Such anisotropy could be attributed to damaged structure, assumed as pre-existing directional cracks, of the in situ soil. Therefore, a Discrete Element Method (DEM) model containing prefabricated cracks is established to investigate the deforming behavior of compressed soil during in situ creep test on the mesoscopic scale. Results indicated that the specimen's anisotropic deformation is intimately related to the presence of prefabricated cracks. Subjected to the prefabricated cracks, microcracks generated during the loading process of the specimen initiated and developed in a directional way, subsequently forming directed cracks. Then the directed cracks tend to form a complete slip zone. However, due to the insufficient vertical load, the directed cracks were unable to coalesce, and the soil mass did not fail during the in situ creep test. Thereafter, additional load was applied in the simulation model. The directed cracks then merged and a full slip zone formed, and the soil was completely destroyed. As a consequence, the anisotropic characteristics of compressed in situ sliding zone soil can be well explained in view of the cracks development. This study may help perceive the landslide deformation characteristics and facilitate the evaluation and prediction methods of landslide stability. • Anisotropic deformation of the in situ sliding zone during compression • Formation of cracked slip zone in a compressed soil sample • Brand new recognition on the in situ sliding zone soil with prefabricated cracks [ABSTRACT FROM AUTHOR]

Strata consisting of massive, dipping layers of hard rock interbedded with thin, soft interlayers are common in Southwest China, and this structure is conducive to the formation of consequent bedding rockslides. The huge Jiweishan rockslide is an example that mobilized 5.6 million m 3 of massive, lower Permian limestone that was stratigraphically situated above a weak, 30 cm-thick layer of bituminous shale with a downslope dip of 21°. Field data and historical observations indicate that the rupture surface of this rockslide weakened gradually from the rear, upper part to the front. This evidence includes (1) a decrease in the thickness and areal extent of fracture-parallel calcite veinlets along the thin rupture zone. (2) the development of a wide, vertical tension fracture at the upper boundary of the slide block, about 50 years before the catastrophic failure; (3) a succession of small collapses that migrated from the upper to the lower parts of the slide block in the decade before the massive failure. This type of landslide is accordingly termed an advancing consequent bedding rockslide (ACB rockslide). An equation was developed to simulate the mechanical behavior of the rupture surface as a function of position and time. Finally, a computational model that incorporates this equation was used to simulate the evolutionary history using realistic mechanical parameters. The simulation results show how the size of an upper “driving block” progressively enlarges at the expense of a lower “ locking block” that restrains the slide mass, until the locking block becomes so small and weak that failure occurs. Good agreement between the simulation results and field data support the proposed evolution model, including the calculated size of the locking block prior to failure and the width of the upper tension fracture. [ABSTRACT FROM AUTHOR]

The distribution of soil pressure in landslides above anti-slide piles is a key factor in their design. The paper describes the evolution of stresses near soil-piles by testing a physical scale model during progressive loading. Displacement monitoring data on the surface of the landslide during loading discloses four main evolutionary stages: the initial stage of deformation, the uniform deformation stage, the accelerating deformation stage, and the damage stage. During initial deformation, the vertical distribution of soil pressure above anti-slide piles is sigmoidal, with the highest pressures occurring in the middle and upper parts of the slide mass. Next, during the uniform deformation stage, the soil pressure begins to assume a parabolic shape in a vertical profile, and this shape is fully realized during subsequent accelerating deformation. Finally, during the damage stage, the soil pressure relaxes to low values near the center of the slide mass, effectively inverting the parabola. Thus, the distribution of soil pressure above anti-slide piles changes in a complex manner during deformation, and these effects must be accommodated in the analysis and design of anti-slide piles. [ABSTRACT FROM AUTHOR]

Objective: To survey the proportion of births born after assisted reproductive technology (ART) and compare the obstetric and prenatal complications between ART and spontaneous pregnancy in women in mainland China. Design: Retrospective analysis. Setting: Thirty-nine hospitals. Patient(s): A total of 112,403 deliveries from 14 provinces and 39 different hospitals composed our retrospective study. Intervention(s): A multiprovince, hospital-based survey was performed. Main Outcome Measure(s): The prevalence of obstetric complications, mode of delivery, and prenatal outcomes were compared between ART and spontaneous pregnancy. For each group, data included singleton and twin deliveries. Result(s): The proportion of infants born as a result of ART in mainland China was about 1.013% in 2011. The incidence of hypertensive disorder in pregnancy (11.0%, odds ratio [OR], 1.27, 95% confidence interval [CI] 1.04–1.60), premature delivery (27.0%, OR, 4.53, 95% CI 3.91–5.25), gestational diabetes mellitus (15.1%, OR 3.05, 95% CI 2.57–3.60), and placenta previa (4.5%, OR 2.18, 95% CI 1.62–2.94) were markedly increased in women who conceived using ART. The cesarean section rate in the ART pregnancy group was 85.3%, which is significantly higher than spontaneous pregnancies (54.0%). Compared with spontaneous pregnancy, ART pregnancy had a significantly increased incidence of low birth weight babies (29.7%) and birth gestational age of less than 37 weeks (30.0%). Infants conceived by ART have increased low 5-minute Apgar and mortality. Conclusion(s): This population-based survey demonstrates that the proportion of births from ART in mainland China was about 1.013% in 2011. Multiple gestation is significantly increased in ART pregnancies, relative to spontaneous pregnancies. The increasing incidence and risk of maternal complications in ART pregnancies (e.g., premature delivery, placenta previa, gestational diabetes mellitus) are found in singleton and twin gestations in ART. A higher cesarean section rate, low birth weight infants, and higher infant mortality rate were also observed in ART pregnancies. Our survey provides a comprehensive overview of the prevalence of ART and ART-associated complications in mainland China, and provides insight into attitudes toward ART among the mainland Chinese population. [ABSTRACT FROM AUTHOR]

Hypertensive disorders of pregnancy (HDP) are a group of medical complications in pregnancy and also a risk factor for severe pregnancy outcomes, but it lacks a large-scale epidemiological investigation in recent years. This survey represents a multicenter cross-sectional retrospective study to estimate the prevalence and analyze the risk factors for HDP among the pregnant women who had referred for delivery between January 1st 2011 and December 31st 2011 in China Mainland. A total of 112,386 pregnant women were investigated from 38 secondary and tertiary specialized or general hospitals randomly selected across the country, of which 5,869 had HDP, accounting for 5.22% of all pregnancies. There were significant differences in the prevalence of HDP between geographical regions, in which the North China showed the highest (7.44%) and Central China showed the lowest (1.23%). Of six subtypes of HDP, severe preeclampsia accounted for 39.96%, gestational hypertension for 31.40%, mild preeclampsia for 15.13%, chronic hypertension in pregnancy for 6.00%, preeclampsia superimposed on chronic hypertension for 3.68% and eclampsia for 0.89%. A number of risk factors for HDP were identified, including twin pregnancy, age of >35 years, overweight and obesity, primipara, history of hypertension as well as family history of hypertension and diabetes. The prevalence of pre-term birth, placental abruption and postpartum hemorrhage were significantly higher in women with HDP than those without HDP. The possible risk factors confirmed in this study may be useful for the development of early diagnosis and appropriate treatment of HDP. [ABSTRACT FROM AUTHOR]

In 2014, the Varnes classification system for landslides was updated. Complex landslides can still be a problem to classify as the classification does not include the flow type in the hydrodynamical sense. Three examples of Icelandic landslides are presented and later used as case studies in order to demonstrate the methods suggested to analyze the flow. The methods are based on the different physical properties of the flow types of the slides. Three different flow types are presented, named type (i), (ii), and (iii). Types (i) and (ii) do not include turbulent flows and their flow paths are sometimes independent of the velocity. Type (iii) include high velocity flows; they are treated with the translator wave theory, where a new type of a slope factor is used. It allows the slide to stop when the slope has flattened out to the value that corresponds to the stable slope property of the flowing material. The type studies are for a fast slide of this type, also a large slip circle slide that turns into a fast-flowing slide farther down the path and finally a large slide running so fast that it can run for a kilometer on flat land where it stops with a steep front. [ABSTRACT FROM AUTHOR]

Landslide displacement monitoring plays a fundamental role in the study of landslide evolution mechanisms, forecasting, risk assessment, prevention, and control. To fill the deficiencies of traditional instrumentation for measuring landslide displacement distributed along lateral direction, a landslide displacement measurement method based on deformation-coupled pipeline trajectory measurement is proposed, and a pipeline trajectory inertial measurement instrument is developed. The developed instrument, primarily comprised of a single shaft gyro, two axis accelerometers, and an external roller encoder, is designed as an axial half strapdown-radial half platform structure combined with a mechanical gravity platform. This structure avoids the singularity of pitch angle and roll angle and can expediently calculate a pipeline trajectory with an Eulerian transformation when obtaining several basic physical variables, e.g., the axial linear velocity, pitch angle, roll angle, and azimuth angle. Additionally, the pipeline trajectory, measured at different times, possesses the ability to reflect the displacement evolution feature of landslides. The results of prototype simulation tests imply a single measurement accuracy of a 12 cm/100 m span and a singly periodic multiple (more than five times) measurement accuracy of a 3 cm/100 m span, which meets medium-precision displacement measurement requirements for a landslide. Additionally, the finished instrument has been successfully applied to the deformation monitoring of the Majiagou I# landslide, which further verifies its feasibility and offers a reference for similar landslides. [ABSTRACT FROM AUTHOR]