Fracture Analysis of an Open Crack in a Rock Mass under Compression Li, Qiang (*) School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian, China anuoli@163.com Yang, Qing (*) School of Civil and Hydraulic Engineering and the State Key Lab. of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China Qyang@dlut.edu.cn Jia, Jingchao (*) School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian, China Liu, Hongliang (*) School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian, China (*) These names are in the family name (surname) first, given name last order; Commas are inserted here to conform to the convention used in this publication for all other names.
			ABSTRACT

Most cracks which really exist in rock masses or prefabricated in model experiments are of certain width, called open cracks, and the open cracks’ surface in the rock under compression will deform, even can be closed. Then there are two cases for an open crack initiation, one is that the crack initiation occurs before the crack is closed, and the other is after the crack closure. In the two cases, the intensity factors(SIFs) is different. So two questions for the fracture analysis of open cracks are generalized as follows: the first one is which model should be selected for fracture analysis, the open crack model(called the open model) or the closed crack model(called the closed model); the other is whether the stress intensity factors(SIFs) of two models need to be modified, and how to be modified when the crack closure effect is considered. In this paper the above questions are solved better. First, a closure criterion of an open crack is established to determine existence state of crack before initiation. If the crack is closed before initiation, the closed model must be chosen; otherwise, the open model should be used. Based on this, corresponding criterion for crack model selected is established. Next, the impact of the deformation or closure of the crack on the SIFs is analyzed, and then the modified formulas of SIFs are deduced for the stricter fracture analysis of the two models. The conclusions in the paper will present the theoretical support for the fracture analysis of an open crack.

Keywords: Closure effect, Open crack, Closed crack, Fracture criterion

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