Study on rock mode Ⅱ fracture based on discrete element model

Abstract

In order to solve the problem of accurate measurement of rock mode Ⅱ fracture toughness and improve the reliability of stability evaluation of engineering fractured rock mass, a detailed numerical study of short core compression (SCC) samples was carried out from the perspective of micro-crack, acoustic emission and block characteristics, combined with fracture toughness calculation by particle discrete element method. The results show that the failure mode of the sample changes from pure shear to tension-shear mixture with the increase of the ratio of slot spacing (C/H). The foreshock-mainshock-aftershock (C/H≥03) transformation and block failure characteristics of acoustic emission models also confirm the result. When C/H=02, the calculated fracture toughness is consistent with that measured in laboratory experiment, which verifies the accuracy of mode Ⅱ fracture toughness test in this case. With the help of discrete element method, the fracture characteristics of short core compression samples are elucidated, and the effect of groove spacing on the failure form and failure mode is determined from the angle of crack growth, which could provide some reference for accurate measurement of rock mode Ⅱ fracture toughness in lab.

Keywords

• rock and soil mechanics; mode ⅱ fracture toughness; discrete element; crack growth; fracture process; micro-crack