高应力软岩隧洞稳定性及支护模拟研究

Simulation of Stability and Support of High Stress Soft Rock Tunnel

为分析高应力软岩隧洞的变形特征和支护效应,采用FLAC3D软件模拟滇中引水工程深埋输水隧洞软弱围岩稳定性与支护措施,对毛洞和支护条件下围岩的位移场、应力场和损伤破坏区的分布规律以及衬砌受力状态进行分析和围岩稳定性评价。结果表明:对深部软岩施加锚喷支护可以提高岩体的围压和承载能力,显著减小软弱围岩的变形和损伤破坏程度,但仅依靠锚喷支护时,围岩变形仍然较大。施加永久衬砌时的围岩位移释放率越大,衬砌的内力越小,但围岩的变形量越大。建议对高应力软岩洞室采用全断面锚喷支护,提高初期支护的刚度和强度。可根据不同围岩位移释放率条件下永久衬砌的内力和隧洞的变形特征,结合永久衬砌的承载能力和隧洞的净空要求,确定合适的永久衬砌支护时机。

In order to analyze the deformation characteristics and support effect of the high-stress soft rock tunnel, FLAC~(3D) software was adopted to simulate the stability and support measures of the soft surrounding rock of the deep buried water delivery tunnel of Central Yunnan Diversion Project. The displacement field, stress field and damage zone distribution of the surrounding rock under the conditions of the tunnel and support, as well as the stress state of the lining were calculated and analyzed, and the stability of the surrounding rock was evaluated. Reasonable timings for support are proposed. The results are as follows. The application of bolt-shotcrete support to deep soft rock can improve the confining pressure and bearing capacity of rock mass, and significantly reduce the deformation and damage degree of weak surrounding rock, but the deformation of surrounding rock is still large when only relying on bolt-shotcrete support. The greater the displacement release rate of surrounding rock when permanent lining is applied, the smaller the internal force of lining, but the greater the deformation of surrounding rock. Therefore, it is suggested to adopt full-section bolt-shotcrete support for high stress soft rock cavern to improve the rigidity and strength of the initial support. In addition, according to the internal force of the permanent lining and the deformation characteristics of the tunnel under the condition of different displacement release rate of surrounding rock, combined with the bearing capacity of the permanent lining and the clearance requirements of the tunnel, the appropriate time to apply the permanent lining can be determined.