V级围岩小净距隧道二次衬砌支护荷载分担比优化研究

以某V级围岩小净距隧道为研究对象, 借助数值分析手段寻求小净距隧道在多种荷载分担比组合下的力学行为特征, 研究了先行洞和后行洞围岩支护的荷载分担比优化问题。结果表明, 先行洞在围岩和初期支护共同荷载比不变的情况下, 围岩相对初期支护承担较小荷载为宜, 二次衬砌荷载分担比的优化值为从大往小趋向60%;后行洞在二次衬砌荷载分担比60%条件下, 二次衬砌支护对地表沉降抑制效果较差, 确定二次衬砌支护荷载分担比的优化值为从大往小趋向70%。研究成果为类似小净距隧道围岩支护荷载分担比优化提供了新的思路。

Optimization of Load-Sharing Ratio of Secondary Liner Support for Small-Clearance Tunnel with V-Grade Surrounding Rock

A small-clearance tunnel with V-grade surrounding rock was taken as the research object. The mechanical behavior characteristics of the small-clearance tunnel under various combinations of load-sharing ratios were explored by means of numerical analysis and the optimization of load-sharing ratio of the surrounding rock support of the antecedent and the following tunnels were studied. The results show that when common load ratio for the surrounding rock and the primary support keep unchanged, the surrounding rock should bear a smaller load relative to the primary support. The optimized value of load-sharing ratio for the secondary liner shall be reduced from large to small, finally approaching 60%. When the load-sharing ratio of the secondary liner for the following tunnel is approaching 60%, the secondary liner has a poor effect in the suppression of the ground settlement. Consequently, the optimized load-sharing ratio of the secondary liner is determined to approach 70%, gradually decreasing from large to small. The research results provide a new idea for the optimization of the load-sharing ratio of small-clearance tunnels with surrounding rock support.