Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

In this study, features and advantages of previous studies on the time dependent rock-support interaction were grafted to overcome the short comings in the existing approaches. Fictitious ground pressure coefficient that can define reduced self support pressure at the tunnel face is presented to take into account a more realistic reduction of longitudinal arching effect due to face advance and the shotcrete hardening in a domestic standard. The proposed model can estimate the time-dependent tunnel convergence and support pressure for a circular tunnel excavated in the homogeneous isotropic rock mass subjected to hydrostatic stress state. A more realistic rock-support interaction is obtained by including the effects of the radial displacement at the tunnel face that can not be measured directly in the field. Moreover, the factors affecting the rock-support interaction, such as rock condition, tunnel size and unsupported span, are analyzed using the proposed model. Through the axi-symmetric analysis of a circular tunnel using a 2-D finite difference code the trends of the variation of load distribution ratio are analyzed and compared with the results from the proposed model. The quantitative analysis on the load distribution ratio reveals that the existing load distribution ratios should be modified. Also, the range of the elastic modulus of soft shotcrete that can be used in the numerical analysis is obtained. A theoretical basis applying the rheological properties of rock mass to the determination of the load distribution ratio is also proposed.