Experiment And Numerical Simulation On Type ? Fracture Toughness Of Soil

Previous researches on soil strength were mainly focused on the compressive strength and shear strength.With the development of engineering construction,soil fracture has often occurred.In order to meet the actual requirements of engineering,more and more attention has been paid to the research of soil fracture toughness and numerical simulation of soil cracks.In this thesis,based on previous studies,the failure process of the type I fracture of the soil is investigated through laboratory tests and numerical simulations,and the following conclusions can be drawn:(1)Dry density and water content of clay have a significant effect on its type I fracture toughness.For a constant water content,the fracture toughness of the soil almost increases linearly with the increasing dry density.For a constant dry density,the fracture toughness of the soil increases first and then decreases with the increasing water content,nearly conforming to the Gaussian function in between.(2)The extended finite element method can simulate the type I fracture and crack propagation of the soil well.During the fracture failure of the specimen,a “?” shaped transverse tensile stress field is formed around the crack,and the displacement field is symmetrically distributed.The smaller the length of the initial crack,the greater the fracture resistance of the specimen.The greater the eccentricity of the initial crack,the greater the bearing capacity of the specimen.Under different initiation criteria,the crack propagates in different ways.(3)The discrete element method can also simulate the laboratory test of soil type I fracture toughness.During the loading process,stress concentration occurs at the tip of crack and near the three loading points,and the displacement field exhibits a certain asymmetry.The fracture resistance of the specimen containing a triangular-shaped initial crack is the weak.As the angle between the initial crack and the bottom edge of the specimen increases and the initial crack length increases,the fracture resistance of the specimen decreases.As the initial crack eccentricity increases,the fracture resistance of the specimen is enhanced.The tensile strength of the parallel bond has the greatest impact on the peak load value of the push rod.Such parameters as effective modulus and bond effective modulus affect the shape of the load-displacement curve of the push rod.(4)In the numerical simulation of the soil type I fracture toughness test,the modeling process of ABAQUS software is relatively simple.In terms of the initial crack initiation criterion,the results of ABAQUS calculations are more reasonable.However,the crack propagation path and displacement field calculated by ABAQUS are not as reasonable as those calculated by PFC software.In terms of the effect of initial crack length and eccentricity on the type I fracture characteristics of the specimen,the results calculated by ABAQUS software and PFC software are similar,which means the calculation results of the two methods are consistent.