| Clay has the advantages of good impermeability and high strength.It is often used as core wall filler in soil core rockfill dam.Core wall is the impervious body of earth rock dam,and its crack resistance is of great importance to dam safety.With the rise of high core dam,the crack problem of clay core wall is paid more attention.This paper relies on the National Natural Science Foundation of China(No.51479012)and the Graduate Innovation Fund of Chongqing City(No.CYS16180).From the angle of fracture mechanics and based on the summary of traditional fracture test methods,two-dimensional fracture test method of compacted clay was carried out according to the theory of fracture mechanics.The numerical simulation tests of two-dimensional fracture of compacted clay are carried out by using the discrete element PFC numerical method.The fracture characteristics of compacted clay under tension,shear,tension shear and compression shear stress are studied respectively from the macro and micro leve.Research contents and conclusions are as follows:(1)From the aspects of specimen structure,loading mode and monitoring method,a two-dimensional fracture test device for compacted clay is designed.The specimens were single fracture cuboid specimens.The loading equipment adopts WDW-100 microcomputer servo control electronic universal material testing machine.The propagation process and opening displacement of the cracks are monitored by the VIC-3D non-contact full field strain measurement system.The stress intensity factors under four stress states are analyzed according to the stress state at the crack tip under four stress states,namely,tension,shear,tension shear and compression shear.(2)Sensitivity analysis of mesoscopic parameters in linear contact model of PFC is carried out,and the influence of mesoscopic parameters on macro mechanical characteristics in linear contact model is studied.The three axis test of clay consolidation and drainage was carried out by using GDS dynamic three axis system,and the macro physical and mechanical parameters of clay were obtained.According to the relationship between micro structure parameters and macro mechanical properties of the biaxial numerical test was carried out using PFC meso parameters calibration,the linear contact model well with clay macro physical and mechanical parameters with PFC micro parameters.(3)Based on the two-dimensional fracture test method,the corresponding tensilefracture PFC numerical model and shear fracture PFC numerical model are established.Using discrete element numerical method,the fracture process of two basic fracture modes,tensile fracture and shear fracture,has been studied.The effects of initial fracture length,initial fracture length,loading rate and specimen size on the macroscopic fracture characteristics,crack propagation process and fracture morphology of the two basic fracture modes are analyzed.(4)Based on the two-dimensional fracture test method,the corresponding tensile shear fracture PFC model and compression shear fracture PFC model are established.Using discrete element numerical method.The fracture process of these two composite fracture modes is studied.The influences of loading angle,initial fracture length and loading rate on the two kinds of composite fracture types,macro fracture characteristics,crack propagation process and fracture failure morphology are analyzed. |
