深埋引水隧洞软弱围岩支护结构受力特征研究

Study of the Mechanical Characteristics of the Support Structure of a Deeply Buried Diversion Tunnel in Soft Rock

文章依托工程实例,针对深埋软弱围岩引水隧洞支护体系的受力特征,开展了现场试验研究,并基于强度折减理论和数值模拟分析,提出了一种计算软岩隧洞施工期间二次衬砌承载力及其强度安全系数的方法,对围岩和二次衬砌的稳定性进行了评估分析。研究表明:边墙部位锚杆发挥拉拔支护效应明显,根据锚杆中性点位置推测出的软弱围岩塑性区有不断发展和扩张的趋势;初期支护钢拱架架设后能立即发挥支护作用,给予围岩较大的支护力;采用该方法求出的二次衬砌在施工期间将参与承担12%的围岩释放荷载,墙脚应力集中部位的安全系数最小,二次衬砌承载特征的计算结论与二次衬砌接触压力的现场试验结论基本吻合。成果可为深埋软弱围岩条件下的隧洞修建提供一定参考。

In-situ tests were carried out regarding the mechanical characteristics of the support system of a diversion tunnel in soft rock by using one project as an example, and a calculation method is presented for calculating the bearing capacity and strength safety coefficients of secondary linings in the construction of soft rock tunnels based on the strength reduction theory and numerical simulation analysis. Additionally, the stability of the surrounding rock and secondary lining is estimated and analyzed. The results indicate that： l） the sidewall rock bolts play an important role in anti-pulling-out capacity, and the plastic zone of weak surrounding rock determined by the neutral point of rock bolts tends to develop and expand continuously; 2） in the primary support, the supporting effect of a steel arch will take effect immediately after it is erected, which plays a major role in surrounding rock support; 3） the secondary lining shall bear 12% of the surrounding rock load released during the construction period; 4） the stress concentrated area at the foot of the wall has the lowest safety coefficient; and 5） the calculation results of the secondary lining bearing characteristics basically agree with the in-situ test conclusions regarding secondary lining contact pressure.