Study On The Stability Of The Weak Bond Slope With A Specific Gradation Under Soaking Condition

Highway?hydraulic engineering and mining etc,such as a large number of constraction,many permanent or temporary slopes were formed,they are always the core problem of geotechnical engineering.To the weak bond slope formed by soil-like rock in the Three Gorges reservoir area,using the discrete element method and physical model test,carring on the thorough anlysis and study.A large numerical triaxial shear test was established to simulation the colluvium's mechanical properties based on discrete element method PFC3 D.The sample's rock contents included 0%,20%,40%,60%,80% and 100%.In addition,the sample's size included 60 × 30 cm,65 × 32.5cm,70 × 35 cm,75 × 37.5cm and 80 × 40 cm.The simulation results showed that:(1)the colluvium's cohesive force decreased along with the increase of rock contents as a approximately linear relation.The internal friction angle didn't change when rock contents less than 40%,increased when rock contents more than 40% less than 60%,increased rapidly when rock contents more than 60%;(2)The sample's cohesive force with same rock contents decreased along with the increase of sample's size and the degree of decrease reached the maximum when the rock contents was 40%.The sample's internal friction angle didn't change when rock contents was 40%,decreased when rock contents was 20%,40% and 60%,increased when rock contents was 80% and 100% along with the increase of the sample's size;(3)The colluvium samples' volume would increase under “low rock contents and high confining pressure” and decrease under “high rock contents and confining pressure” when destroyed.Make the soil-like rock with gravel,clay,kaolin and cement in a certain proportion,Gongjiafang slope as the prototype,implement the outdoor physical model test,and estabilish the discrete element numerical model,the simulation and test results showed that:(1)The mixture with gravel,clay,kaolin,cement according to the 4:2:1:0.14 volume ratio can replace big size irregular wild soil-like rock mass;(2)during the water level rose,the front partial collapse,during the water level drop,the whole model collapse and water pressure gap can indirectly reflect the deformation of slope;(3)Comparaed with model test,the simulation results were in agreement with the actual situation.A numerical model was established to simulate the slope with PFC2 D.The simulation results showed that:(1)the colluvium would slide along the interface between rock and soil after the impoundment of the three gorges reservoir;(2)The failure process could be divided into four periods: the deformation of bottom,the upper and middle section's collapse,the integral sliding,stabilization and the ‘Gubao' in the first period is the key whether 2# slope start breaking;(3)The velocity of the bank slope's movement increased rapidly in a short term and decreased slowly.Comparaed with observation data,the simulation results were in agreement with the actual situation.A discrete element numerical model was established to simulate this landslide with PFC2 D under different water levels.The simulation results showed that:(1)the middle part of landslide has the largest vertical displacement and velocity in the same time under water level of 165 m.Besides,the horizontal stress and strain rate of the toe of landslide reaches the maximum value firstly in the late period under water level of 165 m.(2)Qingshi landslide has no deformation under water level of 145 m.The failure modes are same under water level of 155m?165m and 175 m and the failure process can be divided into four periods: Weaken and creep;Front part's deformation;The instability and sliding of middle part;Stabilization.In the sliding process,the rock and soil mass near the sliding zone will promate the sliding to some extent.The steady state of Qingshi landslide is consistent with the actual situation under different water levels.Cracks' appearance and development under 175 m water level are similar with real situation,and the deviation is in an acceptable range.The discrete element method and outdoor model test was carried to analysis the stability of the weak bond slope,enrich the application of discrete element method PFC2D/3D,provide reference for the prvevention and treatment of weak bond slope.