Study Of Reinforcement Mechanism For Micropile Group In Slopes Under Rainwater

The projects’ practice shows anti-slide micropile improves the anti-slide performance,and improves the mechanism of load transfer between sliding bed and slide mass in landslides.Compared with rigid piles,lack of theoretical research for flexible piles limited it’s wide application in the project.So,anti-sliding mechanism of anti-slide micropiles were taken as research content;law of internal force distribution of anti-slid micropile was researched;design methodology suitable for anti-slid micropile was explored in order to bring out the performance of anti-slide micropile;soil modulation function considering the influence of soil pressure was adopted;Shear strength reduction method considering the influence of suction stress was established;following contents are mainly studied in this paper:（1）Constitutive model parameter: the functions of bulk modulus and shear modulus considered of effective stress and matric suction were established,based on compression curve of normally consolidated soil,volume strain expression of unsaturated soil.Then,numeric calculation based on finite difference software FLAC^3D was realized.（2）New Shear Strength Reduction Method:shear strength reduction method of unsaturated soil was modified,based on theory of suction stress proposed by Lu Ning.In other word,effective friction angle,cohesion in shear strength were reduced through different different methods.Compared with shear strength reduction method,the cohesion was distributed into aggregate interlock and suction,then they were reduced respectively;applicable application based on FLAC^3D finite difference software was exploited.Shear strength reduction method of unsaturated soil based on theory of suction stress accords with the define of strength reduction,and it has a clearer physical significance.（3）Experiental research for anti-slid micropile group: distribution of internal forces,soil pressure and displacement of pile head of anti-slid micropile group in reinforcement engineering of slope were researched,through laboratory model test.Distribution of internal forces,soil pressure and displacement of pile head under different heaped capacities were analyzed.Relevant numerical simulation and analysis were proceeded by FLAC^3D finite difference software.Agreeing with mechanics response of pile body in experimental group explains that the operational method of numerical analysis has particular reasonability and veracity.Relative to short-term precipitation process,the initial soil moisture condition in side slope has great influence on the stability of homogeneous cohesive slope.（4）Slope stability analysis: the influence of change of pore water pressure on slope stability were researched,in unsaturated soil slope reinforcement project;design of anti-slid micropile in unstable slope were proceeded.Analysis result indicates that,in the experiment ignored negative porewater pressure,N_max in micropile is151.4kN,S_max is 136.8kN,M_max is 146.8kN·m;in the experiment considerednegative porewater pressure,on account of that as water content reduces,cohesive force increase,N_max is 2.855 kN,S_max is 22.8N,M_max is 15.16kN·m,negative porewater pressure improves remarkably the stability of cohesive slope.