Failure mechanism of rock-like material with random distribution of flaw under uniaxial compression

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Failure mechanism of rock-like material with random distribution of flaw under uniaxial compression

 

Author: Au, Chi-kwong
Title: Failure mechanism of rock-like material with random distribution of flaw under uniaxial compression
Degree: M.Sc.
Year: 2000
Subject: Rock mechanics
Joints (Geology)
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Civil and Structural Engineering
Pages: xi, 93 p. : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1559447
URI: http://theses.lib.polyu.edu.hk/handle/200/2075
Abstract: There are many joints in rock mass. Joints may be developed in the relief of tensional or shearing stress acting on rock masses. The cause of the stresses has been variously ascribed to shrinkage or contraction, compression, unequal uplift or subsidence and other phenomena. Basically, Joints are developed in vary angle on rock. When the rock mass sustained a surcharge and when the degree of surcharge increase to a particular level, the cracks will initiate at tip of joints. The length of cracks will grow with increasing force. Finally, the cracks will be coalescence with the neighboring joints. The crack coalescence is the cause of the rock mass failure. Most mathematical models were developed to explain and predict the processes of crack growth, interaction and rock failure in single joint and muti-parallel joints, but relatively few experimental investigations were done to examine the failure mechanism of joints on rock mass in varied angle. The failure mechanism is still not clear. This project examines the failure mechanism of limestone-like material with random distribution(varied angle) of flaw under uniaxial compression, the sample contains random distributed fictional flaws, with various length of flaws. Three main points are observed: (1) The first crack initiation is at the tip of flaw which is near the tension zone (the center part) of the sample under uniaxial compression. (2) The number of crack initiation increases with length of flaws. That is the longer length of flaw, the more number of crack initiations from the flaw tip. (3) The peak strength decreases with increasing length of flaw. The experimental peak strength was compared with an analytical method (the model of Ashby and Hallam) and a numerical method (RFPA). In the comparison, it is found the experimental result has a high degree of correlation with the predicted result by the numerical method. However, less with the predicted result by the analytical method.

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