XFEM Simulation Of Crack Evolution In Earth Structures

The evolution of soil cracking involves the entire process from the generation of a soil crack to the formation of macroscopic discontinuities or even complete failure surface.Accurately simulating the soil crack evolution is helpful to in-depth understanding and accurate characterization of soil failure,and it is also of great significance to the soil reinforcement and the safety evaluation of geotechnical structures.This topic has been widely studied,and great progress has been made.However,due to the complexity of the evolution process and the limitations of traditional numerical methods,many difficulties remain to be solved.The extended finite element method(XFEM)can describe a discontinuous field without reconstructing the finite element mesh,which brings significant advantages in the simulation of cracks.The scope of this dissertation is to study and develop a simulation platform for the soil crack evolution based on the XFEM,focusing on the key problems in the simulation of the generation and expansion of two-dimensional soil cracks,the fluid-solid coupled simulation of soil cracks,and the three-dimensional crack simulation.The main work and contribution of this dissertation are as follows:1.The establishment of XFEM simulation platform for soil crack evolution.On the basis of the achievements of the research group,considering the different crack types in soil,the characteristics of stress concentration and redistribution at the crack tip are deeply analyzed,and the sensitivity and accuracy of the judgment condition of crack propagation are discussed.Then an XFEM simulation platform for soil crack evolution is developed by introducing appropriate integration scheme,nonlinear algorithm,and efficient equation solving algorithm and further verified by case study.2.The improvement of simulation method for the generation and propagation of two-dimensional cracks.A method for determining the crack initiation of soil based on element stress analysis and loading backtracking is proposed.Also,the extension mechanism of soil crack is studied,and an extended discriminant method of extended control domain based on the combination of sector and circle is proposed,which enables the program to more accurately and flexibly judge the type,timing,and direction of soil failure.3.The simulation of soil cracks considering fluid-solid coupling.An XFEM fluidsolid coupling scheme is constructed based on the Biot's consolidation theory.The hydraulic fracturing process of soil is described with the dispersed crack state and the embedded crack morphology,and the evolution process of pore water pressure is also discussed.4.The simulation of three-dimensional tensile cracks in soil.The cracking potential function method is introduced into the XFEM to trace the cracking direction more accurately from the macroscopic perspective.The characterization method and integral scheme of three-dimensional crack are given,and a three-dimensional XFEM program is developed,which can effectively simulate the three-dimensional tensile failure of soil.The XFEM simulation platform developed in this dissertation is highly extensible.Subsequent researchers can easily develop new functions on this platform.