Abstract

The dynamic mechanical behaviour and characteristics of rocks have been investigated using different techniques to evaluate the engineering structures under dynamic loads. The authors devised a new experimental apparatus to investigate the behaviour of rocks under shock waves. A new double shearing jig shown in figure 1 was developed and it was used to study the shearing of rocks and discontinuities under static and impact loading conditions using the device. Double shearing tests involve various rocks and discontinuities. The authors describe the experimental results under shock load and static loading and the results are compared with each other and their implications are discussed in rock mechanics and rock engineering. Although the system is quite simple, it is shown that it is very practical to study the shear behaviour of both intact rocks and discontinuities.

Introduction

Various techniques and equipments are used for studying the mechanical behaviour and characteristics of rocks foe evaluating the engineering structures under dynamic loads. Some direct shear devices have been developed and utilized [1-12]. These direct shear testing involves

a) One-way (uni-directional) shearing

b) Two-ways (bi-directional) shearing.

Another approach is to utilize shock loads [13-17]. Huang et al. [13] suggested a punch shear device to measure the dynamic shear strength of brittle solids. In this method, a split Hopkinson pressure bar system (SHPB) is used to apply the dynamic load to a thin disc sample by punching. The sample holder also allows the punch head to load the sample directly and in combination with momentum-trap technique in SHPB. However, there is no such test on rock discontinuities and interfaces utilizing a split Hopkinson pressure bar system (SHPB) and it is very unlikely unless some special jigs and cells are utilized.

The authors devised a new experimental apparatus to investigate the behaviour of rocks under shock waves (Aydan et al. [15]). The device is fundamentally categorized as the drop-weight apparatus and it is possible to evaluate the mechanical behaviour and characteristics of rocks and discontinuities subjected to shock waves during pre-failure as well as post-failure stages. This device is described in the next sections.

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