软岩小净距隧道中夹岩柱分区及加固方法研究

中夹岩柱是软岩小净距隧道围岩稳定控制的关键部位。结合具体工程,提出对中夹岩柱进行区域划分,针对软弱围岩,采用二维有限元计算方法,对中夹岩柱预应力锚杆及注浆加固、中岩墙预应力锚杆加固和中夹岩柱不同加固组合方式进行了研究。数值计算结果表明:在中夹岩柱各区加固中,中岩墙加固是最重要的,对其进行加固,可以减小隧道变形,提高围岩稳定性,改善支护结构的力学状态;各种加固方法对于不同级别的围岩其加固效果不同,在软弱围岩中,注浆加固比对拉锚杆或预应力锚杆效果更显著;加固参数应根据围岩级别、净距大小、中夹岩柱加固组合方式等综合确定,围岩越差,净距越小,则注浆参数应提高越大。

Study on Partition and Reinforcement Method of Middle Rock Pillar in Soft Rock Tunnel with Small Clear Distance

Middle rock pillar is the key in controlling stability of surrounding rock in soft rock tunnel with small clear distance. In this paper, combined with practical engineering, the partition of middle rock pillar is proposed. Applying the 2D finite element method, the prestressed anchor and grouting reinforcement of middle rock pillar, prestressed anchor reinforcement of middle rock wall and different reinforcement combination mode of middle rock pillar are studied. Numerical results show that the middle rock wall is the most important in each region of the middle rock pillar. Reinforcement of middle rock wall is able to decrease deformation of the tunnel, raise stability of surrounding rock and improve the mechanical state of supporting structure. Effect of various reinforcement methods for different grade of surrounding rock is different. Grouting reinforcement is more effective than counter-pulled bolts and prestressed anchor in soft rock. Reinforcement parameters are comprehensively determined according to surrounding rock grade, size of clear distance and reinforcement combination mode of middle rock pillar. Grouting parameters should be enhanced with weak surrounding rock condition and short clear distance.