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|Tunnels in South African gold mines are developed at depths down to 3 600 m below surface where the virgin rock stress approaches 100 MPa and, on occasions, through rock where the field stresses exceed 150 MPa. In addition, many tunnels are subjected to increases in field stress of over 50 MPa during their useful lifetime. As a consequence, the walls of most tunnels are fractured causing the rock to dilate into the tunnel. Quantitative data on the extent of this fractured zone are presented. The function of support in these circumstances is to reinforce and maintain the integrity of the fractured rock. In 80 per cent of the 800 km of tunnels developed annually, the support methods used are capable of maintaining the stability of the tunnels. However, the remaining 20 per cent of tunnels is subjected to severer conditions where dilation in excess of 250 mm occurs and/or where the probability of strong seismic ground motion is high. In these tunnels, additional support is required. The type and pattern of support for both normal and severe conditions is described. In spite of the improved support used, damage to tunnels may occur. To minimize this damage, the concept of a rock reinforcing tendon that will yield and do work, when subjected to quasi-static or rapid deformation, has been put forward. Specifications for such a tendon are presented and the development of certain yielding tendons are described.|
Additional chapters/articles from the SME-ICGCM book Proceedings 6th International Conference on Ground Control in Mining (ICGCM) 6th
|Microseismic Monitoring of Mountain Bumps and Bounces: A Cas||Factors Influencing the Occurrence of Coal Pillar Bumps at||Longwall Pace Bursts and Inadequate Caving: A Came Study||Mine Layout Deign for Coal Bump Control||The Strong Outbursts of Coal and Gas in Coal Mines in China||Bock Bursts Occurrence. in the Coeur D'Alene Mining Dis||A History of Bock Burst Research in the Coeur D'Alene M||Chemical Destressing to Alleviate Rockbursts||Rockburst Control Measures at INCO's Creighton Mine||Prevention. Control and Management of Coal and Gas Outbursts||Application in Design for Close Proximity Multi-Seem Mining||Geologic Conditions Affecting Mineability in the Jane Mine.||Analysis of Cutter Roof Using the Boundary Element Method||A Novel Ground Control Program at Plateau Mining Company||Evaluation of Anchorage Integrity for Grouted Bolts in Weak||STRATA III ? A Full-Spectrum Roof Control Concept||Study of Ground Movement Over a Longwall Mine||Field Measurements of Overburden and Chain Pillar Response t||A Method for Sizing Longwall Pillars Based on Field Measurem||Aspects of Chain Pillar Design in Relation to Longwall Minin||The Initial Collapse of the Overburden Over Longwall Panels||Monitoring and Prediction of Ground Movements Above Undergro||Mechanisms of Chimney Subsidence Over Abandoned Coal Mines||Time-dependent Behavior of Immediate Weak Floor Strata from||The Significance of Specimen Stiffness and Post Yield Charac||Frictional Properties of Rock Applied to Mining Excavations||Ice Pillars, Packwalls, and Brattices||Investigation of Subsidence Over AML: A Case Study||Deign of Support System for Mining Tunnels in Carboniferous||Support of Tunnels in South African Gold Mines||The Stress Measurement and Underground Engineering||Field Measurements Of Overburden And Chain Pillar Response T|