Numerical and Theoretical Analysis on Hydraulic Fracture of Rock Masses Based on Contour Integral and Auto-remeshing Technology

Abstract

The initiation and formation of hydraulic fracture are vital to the prevention of the failures of rock mass structures and the increase of oil production etc. In order to further understand the law and mechanism of hydraulic fracture, The Python language is used to compile the programme for the hydraulic crack propagation based on the Abaqus platform, the auto-remeshing technology is used and and the crack propagation process is realized. The numerical test of hydraulic fracture of No.15 coal roof rock mass in Wangtaipu coal mine under the condition of single and double pre-existing fractures is carried out, and the theoretical mechanism is also discussed, results show that: The “wing” crack first initiates from the crack tip and then develops towards the direction of the maximum principal stress. The crack initiation angle decreases with the increase of the value of hydraulic fracturing factor D ((P − σ1)/(σ1 − σ3)), and the wing crack combination mode includes the tensile-shear mode and the pure tensile mode. KI at the outer side of the crack tip increases during crack propagation and KII changes little, while KI at the inner side increases first and then decreases, and the KII increases after the crack tips coalescence, which indicates that shear effect exists. The research results will provide a reference for the understanding of the mechanism of single and double cracks propagation under hydraulic fracturing.