软岩公路隧道系统锚杆概率可靠度及灵敏度分析

Probabilistic Reliability and Sensitivity of System Bolt in Soft Rock Highway Tunnel

为了解锚喷支护中系统锚杆受力情况,判断隧道衬砌结构稳定性,确保施工安全,避免支护结构失稳带来的损失,结合工点工程地质条件,选择围岩弹性模量、衬砌厚度等作为主要随机变量,计算得到锚杆概率可靠度。利用Spearman秩相关系数对锚杆概率灵敏度进行分析,认为围岩物性参数和喷混凝土厚度是影响锚杆可靠性的主要因素。要提高锚喷支护的安全和稳定性,除保证系统锚杆施工质量外,应确保喷混凝土厚度及其施工质量。在研究段落选择任意断面埋设预制测试锚杆,对隧道周边围岩不同点位锚杆锚固力进行连续监测,获得了大量实测数据;通过绘制时态曲线和锚杆轴力图,分析得到锚杆轴力大小、横向分布及时态变化情况,从承载力角度验证了锚杆的可靠度,现场测试与概率可靠度计算结果吻合。

In order to understand the force in a system of rock bolts in bolt-shotcrete support, judge the stability of the tunnel lining structure and avoid loss resulting from instability of the support structure, the probabilistic reliability of the system of rock bolts is calculated based on the geological conditions of the discussed project with the elastic modulus of surrounding rock and thickness of the lining as the main random variables. Probabilistic sensitivity is analyzed using the Spearman rank correlation coefficient method. Prefabricated bolts were installed in random cross sections in the studied tunnel section, anchoring forces were monitored continually at different points within the surrounding rock, and a large number of data points were obtained. The magnitude, cross distribution and change of bolt axial forces over time are analyzed according to a curve of variation vs. time and an axial force diagram. Boh reliability is verified by bearing capacity and field test results are in accordance with the calculation of probabilistic reliability. It is concluded that physical property parameters of the surrounding rock and the thickness of shotcrete are the main factors affecting bolt reliability. The construction quality of system bolts should be guaranteed in order to improve safety and stability of bolt-shotcrete. Moreover, thickness of shotcrete and its construction quality should also be guaranteed.