Propagation Of Crack In Rock Based On Extended Finite Element Method

As a new calculation methods,extended finite element method(XFEM)is super than the conventional finite element method(CFEM)in dealing with the problems of crack.Because it is not necessary to remesh during the process of describing crack propagation.It is every important to study and reveal the crack propagation behavior in rock for the practical problems related to oil extraction,substructure,and so on.In this thesis,the crack propagation behaviors in rack is researched based on the XFEM.Conceptual framework and development history of XFEM are introduced in brief.The advantages of XFEM in dealing with the discontinuous problems are explained by comparing with CFEM).The 2-D crack is described based on both isoparametric element and unity partition method,and the additional characteristic function for quadrilateral element is supported.Based on the level set method,the crack and its propagation path are orientated and followed,and the discriminated method of different element type is given out.Several kinds of XFEM models for the rock applied by static load are established.The stress intensity factors and crack propagation behaviors under several working conditions are numerically simulated,and the simulated results are reasonable.Then the propagation behaviors of hydrofracture crack in rack are numerically simulated.The influences of horizontal ground stress and material constant on the crack propagation path and crack propagation condition are investigated and analyzed.XFEM models for the rock applied by fatigue load are established.The crack propagation behaviors in rack under fatigue load are numerically simulated.The influences of the number of cyclic load upon the crack propagation behaviors and stress field in rack are investigated.The stress change regulation of the point near the crack tip are analyzed.XFEM models for the rock applied by dynamic load are established.The crack propagation behaviors in rack under dynamic load are numerically simulated.The influences of position of dynamic load upon crack propagation behaviors and stress field in rack are investigated and analyzed.