The Failure Mechanism Of Composite Retaining Structure Of Yangdixia Landslide

Sichuan Yingjing County Yangdixia landslide is the old landslide,due to the earthquake in April 4.20 residents concentrated in the old landslide excavation.Although the implementation of the anti-slide pile project had been done before the excavation,the pile plate can not be poured in time.In the first flood season in 2015,the soil collapses between the piles at first,then soil above slide-resistant pile A6?A9 had collapsed to the original slope roof,lattice frame anchor structure above slide-resistant pile A12?A24 pile had been damaged,slide-resistant pile A19?A24 had tilted.It is obvious that system research is not only important for this project but also has the significance of drawing and designing the anti-slide pile wall structure under similar geological conditions for the structural deformation and the failure mechanism of the composite structure of the front part of the landslide under the complicated construction conditions.The landslide has a long arcuate shape.Its body is 225m long and 440m in width,with an area of about 0.082km2,the total volume is about 176×104m3,and the main sliding direction is 120°.According to the drilling and anti-slide pile excavation,the lower part of the old landslide still retains the layered structure of the original rock structure.The sliding body is divided into two layers,the upper layer is the silty clay,the bottom layer is shaped giant rock layer,mainly by the original bedrock sliding body after the formation of broken.The slip belt is mainly composed of clay-bearing crushed earth,and the slip bed is the Cretaceous upper irrigation group(K2g)mudstone.Based on the field investigation and sampling laboratory test,this paper discusses the causes of the dumping and instability of the local anti-slide piles on the front of the landslide.Through the orthogonal test,the FLAC3D(Fast Lagrangian Analysis of Continua)numerical simulation method is used to analyze the landslide thrust,pile spacing,pile length,elastic modulus and poisson's ratio were used to analyze the effect of soil arching effect between piles.On the basis of the piles arching effect,the soil arch arch is analyzed by theoretical and simulation methods.Then the earth pressure generated by soil before pile and residual slippery force are analyzed according to the arch height,and the larger value is the load to the pile plate(Wall).Then analysis the failure mechanism of the combined support structure.Finally,according to the above research results,corresponding reinforcement reinforcement measures has been put forward to the dumping pile.The main research contents and achievements are showed as follows:1.Through the field investigation,described the engineering geological conditions and deformation and failure characteristics of the Yangdixia landslide.Then put forward the deformation and instability mechanism of the landslide.2.The stability analysis of the old landslide and the speculative surface landslide is analyzed by using the limit equilibrium method and the transfer coefficient method,and the treatment measures adopted by the building of the Lietai new city.3.The stress model of the interaction between anti-slide pile and soil is studied.The effects of landslide thrust,pile spacing,pile length,elastic modulus and Poisson's ratio on soil arching are analyzed by orthogonal test and FLAC3D numerical simulation.4.The influence of soil arching on the force distribution of each structure in pile-wall structure is analyzed.5.The failure mechanism of anti-slide pile combined support structure is analyzed by FLAC3D numerical simulation and soil arch theory.6.According to the overall research of the landslide and the failure mechanism of the failure part engineering,this paper puts forward the comprehensive measures of "sand bag piling + steel pipe pile foundation + temporary protection of bamboo plywood and slope formation".