ABSTRACT:

The shear response of rock discontinuities has a direct relevance to the mechanism of earthquakes and their source characteristics, and their effect on rock engineering structures. The authors are concerned with the development of a dynamic shearing testing machine on rock discontinuities, interfaces and soft rocks. The device is capable of applying four different loading schemes, namely, shear testing with constant loading rate, creep loading, cyclic loading and arbitrary form dynamic loading based on the recent large earthquakes with strong motion records. This paper describes the features of this new testing machine and results of some experimental results.

1 INTRODUCTION

Rock dynamics have become one of the most important topics in the field of rock mechanics and rock engineering. The spectrum of rock dynamics is very wide and includes the failure of rocks, rock masses and rock engineering structures such as rock bursting, spalling, popping, collapse, toppling, sliding, blasting, non-destructive testing, geophysical explorations, science and engineering of rocks and impacts of projectiles and meteorites.

Earthquake is an instability problem of Earth's crust and it should be regarded as a subject of rock mechanics. Earthquake is caused by the varying crustal stresses and it is a product of rock fracturing and/or slippage of major discontinuities such as faults and fracture zones. Therefore, the shear response of rock discontinuities has a direct relevance to the mechanism of earthquakes and their source characteristics, and their effect on rock engineering structures.

Rockbolts and rock anchors are the primary reinforcement members for rock engineering structures. They may be subjected sustained loading, cyclic loading and dynamic loads due to earthquakes or blasting. The load bearing capacity of the rockbolts and rock anchors are governed by the shear behaviour of interfaces such as grout-bar (cable) and grout-rock interfaces. Their mechanical behaviour under conventional direct shear, shear creep and cyclic loading conditions were studied experimentally by Aydan (1989) and Aydan et al. (1990, 1994). However, their behaviour under dynamic loading conditions is still necessary.

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