Anti-slide Pile Research Articles

Model test of cantilevered double-row anti-sliding piles in steeply slipping landslides

The mechanism governing pile–soil and rock interaction in steeply slipping landslides is quite different from that observed in gently slipping landslides. In particular, the mechanism responsible for the double-row anti-sliding pile stress is notoriously complex. Using the K285 landslide along the Neijiang-Liupanshui railway route as an example in our study, we demonstrated that pile safety in steeply slipping landslides was based on the similarity principle. A physical model interaction test between the double-row anti-sliding piles and the landslide was performed to determine the impact of factors such as the failure mode as well as pile stress, bending moment, and head (top) displacement on the safety of a project site. Herein, we noted that the landslide thrust located behind the lower row was about ½- to 1 times that of the upper row when the distance between two rows of anti-sliding piles was about the same as the pile length, assuming that the same loading conditions were used. Also, the resistance of the sliding mass in front of the upper row piles had a maximum value, and the maximum bending moment of the lower row was about - to 1 times that of the upper row under the aforementioned assumptions. The results indicated that the anti-sliding pile heads should be 0.5–1.0 m higher than the ground surface around the piles and backfilled behind the piles. Additionally, the bedrock located before the piles adopted a “wedge” fracture with a depth corresponding to the position of the maximum bending moment. The associated fracture angle and depth were related to the friction angle of the bedrock and the inclination angle of the slipping surface. In conclusion, the study provided insight that will be useful for designing anti-sliding piles to mitigate the occurrence and impact of these types of landslides.

Stability of Extended Earth Berm for High Landfill

This study presents a stability analysis of an extended berm reinforced by geotextiles, with a steep slope of 1V:1.1H (vertical: horizontal). Finite element (FE) analyses were carried out to explore the failure mechanism and factor of safety (FOS) of the berm, on which the effect of the strength of geotextiles, leachate level, and anti-slide pile arrangement located at the toe of the berm were considered. It was found that: (1) failure surfaces developed along the interface between the new and the existing berms; (2) the FOS decreased as the leachate increased, and an FOS value of 1.42 could be obtained if the leachate level was controlled at a height of 20 m; (3) the tensile force of geotextiles was far lower than the available strength, which suggested that the geotextile had enough of a safety reserve; and (4) one row of longer piles at the toe of the berm performed better than two rows of shorter piles if the total length of piles was the same. The design and analysis of this project can be used as a reference for landfill expansion. Especially for a site condition with limited space, a geosynthetic-reinforced soil (GRS) berm is a safe, reliable and promising alternative.

Model Test and Numerical Simulation of Single Pile Response under Combined Loading in Slope

Vertical loads are commonly transferred by piles primarily in the upper structures. However, lateral loads are also significant compared with vertical loads in pile foundation design. Compared with a pile on level ground, there are many particular characteristics in a pile that is on sloping ground. These characteristics depend on the combined loading and the magnitude of the soil lateral displacement. In order to investigate the pile’s bearing characteristics, a model test was conducted and ABAQUS software was adopted to conduct 3D numerical simulation of a single pile with different slope angles under combined loads. The experimental results indicated that (1) the soil pressure along the slope direction was smaller than the other side, resulting in an asymmetry of the slope soil around the pile, and in turn introducing a horizontal thrust to the pile; (2) with the increase of slope angle, the horizontal thrust increased while the single pile’s bearing capacity decreased; (3) the vertical load caused more pile horizontal displacement with the growth of slope angle; and (4) the pile’s moment and the displacement also increased with the growth of the slope angle. The findings in this study can provide a useful reference in the design of piles or anti-slide piles in sloping ground.

Model tests of the evolutionary process and failure mechanism of a pile-reinforced landslide under two different reservoir conditions

Anti-slide piles are widely used for stabilizing landslides and a large number of landslide-piles systems were constituted in reservoir areas. How these landslide-piles systems evolve under reservoir effects is vital for the safe operation of dams. In this study, two reservoir conditions, namely condition of static water level and water level fluctuations, were considered for detailly exploring the influence of static and dynamic water pressure on a landslide-piles system in physical model tests. The pore water pressure, surface deformation and photographs of visual observations were obtained for comparatively analyzing the deformation characteristic and failure mechanism of landslide-piles models under the two conditions. The results show that the soil deformation and failure around the piles were similar in the two tests due to the same pile arrangements. However, retrogressive deformation and two soil collapses occurred in the landslide front area under water level fluctuations instead of slight deformation and shallow erosion under the static water level. The outward hydrodynamic pressure caused by reservoir drawdowns was the primary reason for the soil collapses in the landslide front area. The progressively intensified deformation around the piles which indirectly decreased the soil stability in the landslide front area was the secondary cause for the collapses. The Majiagou landslide-piles system in the field was identified as in the early period of the uniform deformation stage at present based on the field observations, monitoring data and the test results under water level fluctuations.

Field direct shear tests on a backfill soil slope and finite element analysis of its reinforcement schemes

The field direct shear test was used to analyze the backfill soil strength of a filling slope, and the slope controlled by different reinforcement conditions was simulated by finite element method base on the shear strength by the field test. The results show that the shear strength parameters of the backfill soil are friction angle φ = 15° and cohesion c = 25 kPa. Reinforced by anti-slide pile with different lengths, the maximum horizontal displacement of the slope can be reduced by 79.7% ~ 81.3% compared with that of the unreinforced slope. The maximum shear strain of the soil is also reduced to some extent, and the sliding surface characteristics and the strain amplitude are weakened.

Determination of maximum pile spacing of anti-slide pile with rectangular section considering soil arching effects

The reasonable determination of pile spacing is an important link in the design of anti-slide pile. At present, there are many research results on the calculation method of maximum pile spacing of anti-slide pile. Due to different assumptions, different angles of analysis, and different complexity of the formula, the calculation results are quite different, and the research results have not been widely popularized. In this study, taking into account the whole soil arching as the research object, the formulas for calculating the maximum pile spacing of the anti-slide pile based on the soil arching effect behind piles or between piles are put forward considering the overall mechanical balance condition and strength condition of the soil arching, and its rationality is verified by an engineering example. Through calculation and analysis, it is considered that the soil arching between piles controls the maximum pile spacing of anti-slide pile. Through the comparison and analysis with the previous research, the results showed that the calculation formula in this paper is reasonable, feasible and simple, and is convenient for popularization and application in actual engineering.

Investigation of internal force of anti-slide pile on landslides considering the actual distribution of soil resistance acting on anti-slide piles

Frequent landslides have generated huge security threats and economic losses all over the world. As an important anti-slip retaining structure, anti-slide piles can maintain the slope stability. The distribution of soil resistance acting on piles is the critical factor influencing the design of anti-slide piles, and the method of calculating the internal force is directly related to the landslide treatment and construction cost. However, limitations in the method of calculating the internal force of anti-slide piles still exist. In this paper, the influence of the internal force of anti-slide piles both considering and ignoring the soil resistance acting on the piles was verified using ABAQUS software, revealing that the soil resistance indeed had a significant effect on the anti-slide piles, especially when the gradient of the soil before piles was less than 40°. Therefore, the formula for calculating the internal force of anti-slide piles was proposed considering the soil resistance. Based on this formula, the optimum quantity of steel reinforcement and the safety factor were compared in practical slope engineering. This proposed formula considering actual distribution of soil resistance can be used for approximate calculation for anti-slide piles, which can reduce the construction cost, especially in large and neutral landslide engineering.

Experimental Study of Bridge Foundation Reinforced with Front and Back Rows of Anti-Slide Piles on Gravel Soil Slope under El Centro Waves

A shaking table test for a bridge foundation reinforced with the front and back rows of anti-slide piles on a gravel soil slope was designed. The test results were obtained by loading El Centro waves with different peak accelerations. It was not an advantage for the deformation of bridge pile foundation while the distance between the front-row anti-slide piles and pier was large. The back-row anti-slide piles played a major role in seismic reinforcement, and the peak bending moment of the pile shaft and the peak earth pressure behind the pile had a triangular distribution. The distance from the crack to the sliding surface of the anti-slide pile was approximately one fifth of the length of the anchoring section. As the crack propagated, the bearing capacity of the pile shaft decreased gradually. Since the influence of pier inertia force and soil horizontal thrust, a peak negative bending moment and a peak positive bending moment were observed near the pile top and the sliding surface respectively. The rate of attenuation of the bending moment from the top of the pile along its depth was related to the resistance of the soil around the pile. The stress-induced deformation of the pile foundation behind the pier was larger than that in front of the pier. The peak ground acceleration (PGA) amplification factor of the slope had a vertical amplification effect and a layered distribution. The acceleration responses of the sliding section and the steep slope section were strong, while the acceleration responses of the region between the bridge pier and the back-row anti-slide piles were weak. With the increase in the vibration intensity, the soil damping ratio increased and the PGA amplification factor decreased. The feasibility of analyzing the acceleration response of the slope model by the two-dimensional equipotential map was experimentally verified.

Method to Control the Deformation of Anti-Slide Piles in Zhenzilin Landslide

Anti-slide piles were used in the region of the Zhenzilin landslide in Sichuan, China. The horizontal displacement of these piles exceeds specifications. Deterioration in bedrock properties may cause deformation, thereby causing landslide destabilization. An approach was developed for the analysis of anti-slide pile in two bedrocks with different strengths below the slip surface. A relationship has been established between the modulus of subgrade reaction of the first weak bedrock and reasonable embedded length for landfill slopes with strata of various strengths. Furthermore, the influence of embedding length on deformation has been studied to determine the reasonable embedded length, which helps reduce deformation and ensure landslide stability. The results reveal that (1) at a constant embedded length, horizontal displacement increases with the thickness of the first soft bedrock, meanwhile the maximum shear force remains constant, and the bending moment first increases followed by subsequent decrease; (2) with an increase in the embedded length, horizontal displacement and the maximum shear force of the pile in the embedded bedrock decrease, whereas the bending moment increases; (3) the maximum internal forces and horizontal displacement increase with a decrease in the subgrade reaction modulus of the first weak rock; and (4) the reasonable embedded length of an anti-slide pile increases with a decrease in the subgrade reaction modulus of the first weak bedrock. The proposed approach can be employed to design anti-slide piles in similar landslide regions to control pile-head deformation.

Case Study of the Effect of Rainfall Infiltration on a Tunnel Underlying the Roadbed Slope with Weak Inter-Layer

It is a common type of tunnel under-cross the roadbed slope with weak inter-layer. Rainfall infiltration will cause soil softening, matric suction and strength reduction, which seriously threaten the safety of slope and tunnel. This paper presents a case where a tunnel underlying the roadbed slope with weak inter-layer in Guiyang 1# line, China. The seepage calculation model in MIDAS GTS/NX software, considering hydraulic permeability coefficient characteristic curve and soil-water characteristic curve, was used to analyze the stress and deformation of the roadbed slope and tunnel. The results reveal that rainfall infiltration has great influence on the deformation of roadbed slope with weak inter-layer and the force of internal tunnel. Slope displacement increases rapidly in the early stage and decreases in the late stage, but the absolute value of displacement increases continuously and the slope safety factor decreases gradually, which makes the slope in a dangerous state. The force of tunnel lining increases in the early stage and decreases with the recovery of soil strength after rainfall. The control effects of anchor cable and anti-slide pile reinforcement on slope sliding and tunnel stress were studied. And the anchor cable reinforcement measure is more effective on reducing slope slip and tunnel lining structure internal force.

Numerical Study of Optimal Parameters on the High Filling Embankment Landslide Reinforced by the Portal Anti-Slide Pile

The landslide signs were discovered in a high filling embankment slope, which was located on an express highway construction site in Guizhou, China. According to the in-situ monitoring results, the landslide mechanism and the stabilization effect of the portal anti-slide pile were preliminarily analyzed. The sliding shear zone of the landslide was obtained by the in-situ monitoring. Tw o numerical models with imposed sliding shear zone were established to analyze the evolution of the landslide instability and the stabilizing effect of the portal anti-slide pile. The comparative analysis of in-situ monitoring data and numerical simulation result shows that the two numerical model are reliable. Furthermore, the numerical model of embankment slope that reinforced by portal anti-slide pile was implemented to analyze the structural behavior of pile under the different pile parameters, and the pile-soil interaction was considered in the numerical model. The influence of the pile parameters (pile spacing, pile row spacing, and linked beam size) on the stabilization effect, structural deformation, and economic benefit were studied. The numerical results provide a guide for determining the optimum parameters of the portal anti-slide pile.

Finite Element Analysis of Unsymmetrical Pressure Treatment of Shallow-Buried Tunnel with Half-road and Half-tunnel

Taking the Sajin tunnel project of T26 contract section of Du (Yun) An (Shun) Highway as an example, this paper analyzes the difficult problem of unsymmetrical pressure construction of the tunnel. This paper puts forward a systematic treatment scheme of setting anti slide pile as the main part, and compares and verifies the calculation model established by Midas SoilWorks software. The calculation results show that this method can effectively reduce the bending moment and deformation at the left arch waist of the tunnel. The minimum safety factor of the initial support structure of the tunnel is 1.36, which greatly reduces the construction risk. At the same time, the quality control of the treatment process of the project is analyzed, and the corresponding treatment suggestions are put forward, which can provide reference for similar highway tunnel engineering design and construction.

Numerical Analysis of The Three Piles of Facing Each Other

In order to study the deformation and stress characteristics of the pile under the action of landslide thrust. Taking the Suo Er Tou landslide in Gansu Province, China as the engineering background, In the paper the numerical analysis model by establishing the finite difference software FLAC3D of geotechnical engineering is analysed the displacement and bending moment of the pile. The anti-slide pile adopts pile element, soil constitutive model uses Mohr-Coulomb. The results show that the displacement of the piles at the top of the pile and the section of the pile are basically equal, but the horizontal displacement values are not equal above the sliding surface. In the sliding surface, the bending moment of the front pile is smaller than the bending moment of the back pile, but the bending moment of the front pile at the top of the pile is larger than the bending moment of the back pile.

Deformation characteristics and failure mechanism of a reactivated landslide in Leidashi, Sichuan, China, on August 6, 2019: an emergency investigation report

At approximately 2:00 p.m. (Beijing time) on August 6, 2019, the previously controlled Leidashi landslide was reactivated near group 7 of Zhangjiagou village, Jianyang County, Sichuan Province, China. The 2019 Leidashi landslide damaged two main roads and 44 antisliding piles and posed a threat to another main road. This landslide was a reactivation of the 2010 Leidashi landslide and had an accumulation zone of 2.2 × 106 m3. To explore the deformation characteristics and failure mechanism, detailed field investigations, unmanned aerial vehicle photogrammetry, airborne LiDAR surveys, borehole drilling and inclinometer installation were carried out, and the collected data were analyzed. The results show that the 2019 Leidashi landslide could be divided into main slipping zone and activated zone according to movement state, and the main slipping zone could also be divided into main scarp area, main deposit area, climbing area, uplift area, and local landslide area according to the local movement and geomorphic features. The rapidly increasing landslide thrust caused by short-term but continuous heavy rain caused the failure of the antisliding piles and ultimately reactivated the 2010 landslide.

Rainfall-induced reactivation mechanism of a landslide with multiple-soft layers

A study on the site investigation data from the Chengnan landslide, which was a partially reactivated ancient landslide in Meigu County, Xichang City, China, is presented. To explore the reactivation mechanism of the Chengnan landslide, we conducted site investigation, surface displacement monitoring, deep displacement monitoring, finite element analysis, and limit the equilibrium analysis of the Chengnan landslide. The results indicated that the Chengnan landslide experienced multiple reactivations. It was initially reactivated in 2002 along the first clay layer at a depth of 14 m; after comprehensive treatment measures, which included excavating to reduce loads, improving the drainage system, and installing anti-sliding piles in 2006, further deformation was prevented. However, heavy rainfall in 2007 caused groundwater infiltration, softening the second clay layer at a depth of 28 m and transforming it into a new sliding surface (i.e., the second sliding surface). Consequently, Chengnan landslide was reactivated again along the second sliding surface, and the anti-sliding piles moved together with upper sliding body along the second sliding surface because this sliding surface was located deeper than the anti-sliding piles. Based on the results of this study, a multilayer creeping–tension mechanism controlled by multiple soft layers of the Chengnan landslide was proposed. This interesting case study should be considered from a scientific and technical point of view; some valuable suggestions for site investigation and treatment of this kind of landslide are also proposed.

Study on the Structure Optimization of h-Type Anti-Slide Pile

Compared with the traditional anti-slide pile, the h-type anti-slide pile has larger overall lateral stiffness, more reasonable structure stress, and can resist the greater landslide thrust. However, due to the short development history, there are relatively few studies on h-type anti-slide pile, and its structural design is not perfect. Numerical software Flac3d was used to optimize the structural parameters of h-type anti-slide pile, and the results showed that the optimal beam stiffness was 3 times of the front and rear piles, the optimal rear pile depth was 0.28 times of the length of the rear pile, and the front pile depth was 0.5 times of the length of the front pile.

Kinematic limit analysis of three-dimensional unsaturated soil slopes reinforced with a row of piles

Abstract The variation of moisture content in unsaturated soils (i.e., suction) significantly impacts the soil’s strength and is critical in predicting the slope safety. Employing the kinematic limit analysis method, this paper proposes a new method for the stability evaluation of three-dimensional (3D) piled unsaturated soil slopes. A 3D kinematically admissible rotational failure mechanism incorporated with a row of piles is considered and extended to unsaturated conditions. A novel local layer-wise summation method (LLSM) is developed to account for the suction effect on the lateral forces acting on piles. The energy dissipated due to the resistance of anti-slide piles is computed using the LLSM. The proposed method is validated through a series of comparisons with existing results. Numerical studies about the parametric effects were conducted, indicating that the reinforcement of piles depends strongly on the soil types, pile location and pile spacing. The numerical results indicate that the optimum location of piles lies between the middle and top of the slope surface, especially in xp/lx = 0.6–0.7. For gentle unsaturated soil slopes with larger internal friction angles and narrower width constraints, the optimum location of piles approaches the middle of slope surface. The reinforcement of anti-slide piles is more pronounced when the pile spacing D1/dp ≤ 3. The slope stability can be improved by about 10% ~ 20% when the pile spacing D1/dp ≥ 5. Some useful suggestions are presented in this paper for engineering applications.

Deformation Control Method of the Antislide Pile under Trapezoidal Load in the Zhangjiawan Landslide

Antislide piles are set in the Zhangjiawan landslide area, where the general features of the bedrock below the slip surface include upper weak and lower hard strata. Based on a site investigation, the horizontal displacement of the antislide pile head is 14.8 cm, which is not conducive to the stability of the landslide. In the study, a displacement calculation method for the pile under trapezoidal load is proposed for a colluvial landslide controlling. Furthermore, factors affecting the deformation and internal forces of the pile were also studied. The results indicated that (1) when the embedded length of an antislide pile increases, the horizontal displacement on the pile and maximum absolute shear force decrease, while the bending moment of the pile exhibits opposite trends; (2) the relationship between maximum shear force and maximum bending moment is linear with increasing driving force of landslide; and (3) increase in the ratio of the driving force between the pile head and slip surface (q0/q1) steadily increases the horizontal displacement of the pile. The relationship between the distribution of the driving force (q0/q1) and the reasonable embedded length of a pile is a quadratic function, which can be used to determine the reasonable embedded length of a pile under the action of rectangular or triangular loads. It is very useful to use the above method to guide the design of antislide piles in similar areas.

Contrastive analysis of dynamic response of tailings dam with and without geofabriform by shaking table model test

Construction using geofabriform is a new promising technology to build fine grain tailings dam. Large-scale shaking table tests are conducted in this study to investigate the dynamic performances in terms of horizontal acceleration and displacement of the tailings dam with and without geofabriform subject to horizontal earthquakes. Test results indicate that the seismic performance of the tailings dam with geofabriform is significantly better than that of tailings dam without geofabriform. The two types of tailings dams have different failure modes under the action of earthquake. The acceleration amplification factor(Am), vertical displacement and horizontal displacement of the tailings dam with geofabriform under the same seismic acceleration input are smaller than that of the tailings dam without geofabriform, the maximum attenuation amplitude of the Am at the dam slope reaches to 81%. The horizontal displacements of the two types of dams are nonlinearly distributed in the height direction and the geotextile bags of the tailings dam have an upward displacement and are tilted upward. According to the failure mode of the tailings dam with geotextile bags, it is recommended to strengthen the drainage measures and set up anti-slide piles at the bottom of the geotextile bags body to strengthen the tailings dam.

Simulation study on rock slope reinforced by anti-slide pile: a case study

For the collapse of bedding rock slope in Yuqian Expressway, by using simulation software FLAC-3D this paper established simulation models bedding rock slope before and after reinforced by combined supporting, i.e., “slide-resistant pile+ diagonal bracing wall+ anchor cable”, and collected parameters such as deformation and shear stress through three monitory points established. As simulation results compared with field monitoring data, bedding rock slope before reinforced was unstable, belonging pull-type failure model, and this failure model was sudden; the displacement contour map after the slope was reinforced by combined supporting showed that there existed one bigger shear zone in the rock interface, and the shear zone was disappeared after this slope was reinforced, then maximum deformation was decreased; the displacement vector map of slope showed that this slope slipped along the rock interface before it was reinforced, but the whole slope slid along one arc after it was reinforced; shear stress concentration phenomenon in the rock interface was disappeared obviously after this slope was reinforced. As monitoring deformation compared with simulation deformation, slope deformation was less; and the slope was stable; the reinforcement measure of combined supporting has the better retaining effects.