28 Estimation of ultimate rock pressure for tunnel linings under squeezing rock conditions—a new approach

Underground excavation design has always been regarded as a very difficult job for engineers. Up to now the problems concerning the determination of the value of ground pressure and its distribution have not been satisfactorily solved. Therefore, an essential means is to obtain field measurement data in tunnels and apply them in design. To study the displacement behavior of inside surface of tunnels and the interaction between the surrounding rock and the lining are of extreme importance in field instrumentation. In this paper, the traditional design methods and measuring technique used recently are briefly introduced and two practical design methods used in China, the Stress Relief Method and Displacement Method, are discussed. The former is by means of back analysis using surface stress value and applies to moulded concrete lining while the latter applies to shotcrete and rockbolt lining as well as double-lining.

The designer may use the displacement data to determine the proper tine for constructing each layer and to modify design parameters of lining. By the two methods and some practical experiences in tunnellings, the author presents a new design method - Information Control Method. The basic procedures of this method are to measure the pressure and displacement at some key points during construction, check and ixodify the initial design by using measurement data, then take the revised design as final one for following construction sections. The new method thus makes it possible for rapid in situ design.

• INTRODUCTION

• STATE OF ART

• PROPOSED THEORY

• VERIFICATION OF HYPOTHESIS

• APPLICABILITY OF THEORY

• CHARTS FOR ULTIMATE ROCK PRESSURE

• CONCLUSIONS

• REFERENCES