Page 10 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides

Contents ix

Effect of Tunnel Depth on Support Pressure and Closure 127
in Tunnels 127
129
Approach for Obtaining Ground Reaction Curve
Coefficient of Volumetric Expansion of Failed Rock Mass 133

10. Rock Mass Index 133
133
Introduction 134
Selection of Parameters used in RMi 137
Calibration of RMi from Known Rock Mass Strength Data 140
Scale Effect 141
Examples (Palmstrom, 1995) 141
Applications of RMi 142
Benefits of Using RMi
Limitations of RMi 145

11. Rate of Tunneling 145
146
Introduction 146
Classification of Ground/Job Conditions for Rate of Tunneling
Classification of Management Conditions for Rate of Tunneling 153
Combined Effect of Ground and Management Conditions 154
155
on Rate of Tunneling 156
Tunnel Management (Singh, 1993) 156
Poor Tender Specifications
Contracting Practice 159
Quality Management by International Tunneling Association
159
12. Support System in Caverns 160
162
Support Pressure 163
Wall Support in Caverns 164
Roof Support in Caverns 164
Stress Distribution in Caverns 164
Opening of Discontinuities in Roof Due to Tensile Stress 164
Rock Reinforcement Near Intersections
Radial Displacements 169
Precautions
169
13. Strength Enhancement of Rock Mass in Tunnels
169
Causes of Strength Enhancement 172
Effect of Intermediate Principal Stress on Tangential Stress
173
at Failure in Tunnels 177
Uniaxial Compressive Strength of Rock Mass 178
Reason for Strength Enhancement in Tunnels and a 178

New Failure Theory
Critical Strain of Rock Mass
Criterion for Squeezing Ground Condition
Rock Burst in Brittle Rocks