锚杆在隧道初期支护体系中的作用机理分析

Analysis of Bolt's Action Mechanism in the Tunnel Initial Support System

通过理论分析对锚杆在围岩和隧道初期支护体系中的作用机理进行探讨,运用数值模拟的方法对Ⅲ～Ⅴ级围岩中考虑锚杆作用后初期支护的受力响应规律进行分析总结。结果表明,在Ⅲ级围岩(浅埋段)、Ⅳ级围岩中,锚杆对初期支护受力的改善作用较为突出,对于Ⅴ级围岩,由于其坍落拱范围远远大于拱部锚杆及周边岩体形成的组合拱结构,拱部锚杆的作用微乎其微,而边墙锚杆能有效改善初期支护受力状况,且利于稳固钢架。因此,边墙锚杆的设置显得更有必要。最后,对现行衬砌通用图的设计参数提出了建议。Ⅲ级围岩(浅埋段)和Ⅳ级围岩深埋工况安全系数较大,建议适当优化设计参数;Ⅴ级围岩工况的围岩压力小于Ⅳ级围岩(浅埋段),而初期支护设计参数却强于Ⅳ级围岩(浅埋段),建议优化Ⅴ级围岩初期支护参数,使各级围岩初期支护的安全度较为一致。

The bolt’s action mechanisms in the tunnel initial support system were discussed through theoretical analysis. The responses of initial support in rocks of grade Ⅲ ~ Ⅴ after considering the action of bolts were summarized by using numerical simulation. The result indicates that,bolt has a more prominent effect in rocks of grade Ⅲ and Ⅳ than in rocks of grade Ⅴ. Compared with insignificant effect of arch bolts in rocks of gradeⅤ,sidewall bolt can effectively improve stress state of the initial support,that’s because in the sounding rocks of grade Ⅴ,the range of collapsing arch are much larger than the built-up arch structures composed of arch bolts and surrounding rocks,while the sidewall bolts could effectively improve the stress condition of initial support and help to stabilize steel frames. Thus,setting sidewall bolts becomes more necessary. Finally,the optimization suggestions for standard drawing design parameters of tunnel multilayer lining structure were put forward. The safety factor of initial support should be reasonable by adjusting design parameters in shallow buried rocks of grade Ⅲ and deep buried rocks of grade Ⅳ,same as the situation in deep buried rocks of gradeⅤ and shallow buried rocks of grade Ⅳ,so as the safety degree of initial support in various surrounding rocks are consistent.