In view of the nonuniform landslide driving force in practical cases and the common landslide-pipeline separation phenomenon, a new pipeline-soil separation model under the action of a parabolic landslide driving force is proposed in this paper, and the closed analytical solutions for this model are derived based on elastic foundation theory. Moreover, the case of a long transportation pipeline crossing the Luozhentian landslide was studied using the analytical method, and comparisons between the analytical results and finite-element method (FEM) results are also made to validate the exactitude of the analytical solutions. In addition, the deflection and stress results of the pipeline in different conditions were also compared, and influences of the calculation parameters on pipelines were analyzed. Three conclusions can be drawn: (1) the deflection and stress of the pipeline increase remarkably along with the growth of length of the separation section; (2) the deflection and stress of the pipeline increase along with the growth of |lambda|, which reflects the nonuniform degree of the parabolic driving force; (3) the deflection of the pipeline decreases slightly with the growth of the resistance coefficient k of the landslide soil, whereas the stress changes nonmonotonously; and (4) the deflection and stress of the pipeline slightly decrease with the growth of the lengths of pipeline crossing the landslide, and the maximum deflection of pipeline increases with the growth of the proportion Omega. (C) 2018 American Society of Civil Engineers.

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 (F-s) 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.

The failure of construction solid waste (CSW) landfill slopes caused by overload conditions often results in extensive losses to urban construction. Based on a strength reduction technique and geotechnical plastic limit analysis theory, the upper bound solutions of the overall and local stability of the double-step muck slope of a CSW landfill with overloads acting on the top and step are deduced. An optimisation programme is designed in MATLAB to solve for the safety factor and the potential slip surface. Through the introduced theoretical analysis method and the finite difference shear strength reduction method, the stability and critical slip surface trends of the studied slope are obtained for different overload positions and intensities. Furthermore, the influences of different overload ranges acting on the slope top are investigated. The results show that slope stability commonly decreases linearly with increasing overload intensity. When the overload acts on both the top and step of the slope, the overall stability is mainly affected by the overload on the slope top. Moreover, as the overload intensity increases, overall failure occurs first; then, the local failure of the case slope occurs.

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 degrees. It illustrates that the determination of the ultimate sliding surface requires comparison of multiple failure modes, not only mode A.

Pile-anchor reinforced slopes show to have better seismic resistance performance than other traditional supporting structures. However, their bearing mechanisms are not yet fully understood. In this study, dynamic centrifuge model tests are carried out to study the dynamic response and synergistic mechanism of rock slope reinforced by pile-anchor composite structures under seismic loading. The centrifuge model is devised by following the scaling principle, and the properties of the model materials are determined by laboratory tests. Some parameter studies are carried out considering the anchor elastic modulus, pile bending stiffness, and pile embedding depth. The test results are discussed in terms of the failure mechanism of the slope to help better understand the synergistic mechanism of the pile-anchor structure in seismically active areas. © 2023 Elsevier Ltd

The stability of landslides in reservoir areas is significantly influenced by water level fluctuations and seasonal precipitation events. To mitigate these landslides, a pile-anchor (PA) structure has been developed by adding anchors to common anti-slide piles. However, limited research has been conducted on the behaviours of PA reinforced reservoir landslides under changing environmental conditions. In this study, model tests of PA reinforced landslide were carried out using a multi-field monitoring technique to investigate the behaviours of PA reinforced landslides. The study utilized the Majiagou landslide in the Three Gorges Reservoir region of China as a prototype. Three sets of model tests were conducted to simulate the three different triggers of varying water level, rainfall, and thrust load experienced by landslides in reservoir areas. Furthermore, the performance of PA structures was compared to that of pile structures to demonstrate the superiority of the PA structure reinforced landslide. The results indicated that the behaviours of PA remain consistent regardless of the three different triggers, and their general performance can be divided into three stages: stable, fast-deformed, and slow-deformed stage. The distribution of the bending moment exhibits an S-shaped curve, with the maximum bending moment near the slip surface. The maximum negative shear force in the bedrock indicates that part of the structure embedded in the bedrock can effectively resist sliding thrust. In addition, the softening effect can lead to the different responses of PA reinforced landslides under different triggers. This study may provide a deeper understanding of the behaviors of the PA reinforced landslides in response to evolving environmental conditions in reservoir areas. © 2023 Elsevier B.V.

Aiming at the anisotropic characteristics of frozen soil, this paper established a modified linear bond contact model that can reflect the anisotropic characteristics of frozen soil based on the linear bond contact model, and generated a discrete element constitutive subroutine (DLL) for particle flow program (PFC3D) calls through C++. Firstly, tensile and shear stimulations were carried out on a single contact. By comparing numerical and theoretical results, the calculation accuracy of the modified linear bond contact model for frozen soil considering orthotropic was verified. In addition, the triaxial compression tests of frozen soil at different temperatures were simulated and compared with the stress-strain curves obtained from the tests. The results show that the proposed modified linear bond contact model has good applicability to frozen soil. Based on the calibrated meso-parameters of the model, a series of triaxial compression discrete element numerical simulations was carried out. Using the simulation results, the influences of the inclination of the virtual weak surface on the stress-strain curve characteristics, strength and shear strength indexes of frozen soil were discussed, and the evolution laws of effective coordination number and meso-fabric quantity were analyzed. The research results can provide a basis for using numerical methods to study the orthotropic macro meso-mechanical properties of frozen soil. © 2023 Biodiversity Research Center Academia Sinica. All rights reserved.

A spoil dump slope is a kind of artificial slope formed by the accumulation of engineering waste residue from multiple sources, which results in high variability of its mechanical properties. Large amounts of groundwater inside such a structure can make it prone to slope instability. Although an air-injection drainage method has been developed in recent years to reinforce common soil slopes by facilitating drainage, research involving the underlying mechanisms still needs to be further strengthened. In this study, a gas-water two-phase flow theory was applied for unsaturated soil seepage in a spoil dump slope, and the uncertainty of the spoil's physical and mechanical properties was considered in a reliability analysis to evaluate the reinforcement effect of the air-injection drainage method. Based on a case study, the changes in reliability index and failure probability were determined before and after injection under different air pressures. The results show that air-injection drainage methods can provide effective reinforcement for spoil dump slopes by significantly reducing porewater pressures in a potential slip zone, thus reducing the possibility of slope failure. Moreover, a spoil slope reinforced by this method can better resist the adverse impact of rainfall.

Anchored piles are an important combined supporting structure and widely used in landslide prevention and control. The calculation of the internal force of a pile-anchor is highly significant. In this paper, we propose a modified deformation coordination model to more accurately calculate the internal force of anchored piles based on a simple analysis model originally developed by (Qu et al. 2016). In the modified deformation coordination model, the pile-anchor interaction is divided into two stages: (1) prestressed anchor cable application stage; and (2) landslide thrust action stage. The anchor cable deformation is taken as the sum of the free section and anchorage section. A deformation coordination equation is established based on the unification of the horizontal pile displacement and anchor cable defor-mation at the junction of the pile and anchor cable. The anchor cable tensile stress calculation formula is then obtained by combining the virtual work principle and graph multiplication theory in structural mechanics. An engineering case study of a pile with double-row anchor cables is tested to compare the results obtained using the traditional model and Chinese codes, which demonstrates the capability of the proposed model to calculate the internal force of anchored piles.(c) 2023 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).