Understanding the behavior of brittle rocks under different stress conditions is extremely important to the design and construction of underground projects such as mines, tunnels and underground hydropower stations. At the University of Hong Kong, both laboratory tests and numerical simulation were carried out to study the behavior of typical Hong Kong rocks. For the laboratory tests, the deformation properties (expressed by stress-strain curve) and failure process of granite under compression and tension were investigated. In addition, the evolution of dilatancy and time-dependent strength degradation of granite under constant loading were studied. AE technique was used to study the development of fracture during these tests. For the numerical simulations, the discrete element method was adopted to carry out numerical tests to simulate the laboratory tests. A same set of tests were carried out in the numerical simulations using the discrete element method (DEM). The present paper, which focuses on granite, reports and compares the results of the laboratory tests and the numerical simulations.


Rock is a heterogeneous geological material filled with micro cracks and fractures. It is the formation, growth and eventually coalescence of these defects that govern the mechanical behavior of rock under different loading conditions. Understanding theway howthese flaws develops and the relationship between this process and the behavior of the rock is essential for engineering applications.

Experimental investigation is the basic method used to study the deformation and the failure process of rock under different loading conditions (Lonkner & Byerlee 1992, Wawersik & Fairhurst 1970, Hudson et al. 1971). The experimental studies have been carried out at different scales. In the macroscopic scale, uniaxial compression tests are the most common and widely used tests for studying rock properties. The stress-strain curve before peak strength is divided into four stages (Bieniawaski et al. 1969). The development of stiff testing machine and the advancement of the control system have made it possible to study the post-peak behavior of brittle rocks. The complete stress-strain curve of brittle rock under compression has been intensively studied (Wawersik&Brace 1971, Hudson et al. 1971, Okubo et al. 1990). In the microscopic scale, various technologies including microscopic photograph, scanning electron microscopic and X-ray tomo-densitometry have been used to investigate the change of internal structure of rocks under different loading conditions (Olsson & Peng 1976, Tham et al. 2003).

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