Abstract
Rock material properties play an important role in assessing rock mass behaviour. Passive rock bolts stabilize a rock mass by restricting relative displacements; however, they may reduce rock material properties. While assessing properties of rock mass reinforced by rock bolts, the alteration caused in rock material properties due to drilling and bolting operation should be well understood. The present work makes an attempt to study the alteration in rock material properties due to drilling and bolting operations. The study has been conducted through physical tests on natural rock specimens in the laboratory. Virgin cylindrical specimens of intact rock were tested under uniaxial compression. Drilling was done through specimens and fully grouted bolts were installed. These specimens were also tested under uniaxial compression. It is observed that the drilling has substantial effect on the uniaxial compressive strength and modulus. A simple problem of tunnel is analysed which demonstrates the effect of alteration in material properties on the strength of rock mass around the tunnel in the field condition.
Highlights
Rock mass encountered in projects like tunnels and caverns generally consists of intact rock blocks separated by discontinuities
The drilling and bolting operations may affect the properties of intact rock material in the following manner
As the hole is drilled through intact rock blocks, zone of weakness will develop around the hole
Summary
Rock mass encountered in projects like tunnels and caverns generally consists of intact rock blocks separated by discontinuities (joints). Installation of bolts reduces relative displacement between rock blocks (Figure 1) and enhances the rock mass stability. (ii) The deduction of rock material for creating drill holes may induce weakness in the rock block. As the hole is drilled through intact rock blocks, zone of weakness will develop around the hole. The main aim of present study is to examine the effect of drilling and installation of bolts on rock material properties. For this purpose, cylindrical specimens of a natural rock have been prepared. The specimens were tested under uniaxial compression to investigate the weakness brought into intact rock by installation of bolts. Stability of rock mass with discontinuity and not the intact rock material, which does not have any discontinuity
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