土质隧道支护方式对围岩稳定性影响的模型试验研究

以相似理论为基础,采用砂土模拟围岩,铁丝模拟锚杆。实测隧道开挖过程中,不同洞周支护力、不同锚杆长度以及锚杆与洞周支护力共同作用下围岩应力分布、稳定性及分区的变化规律。采用有限元模拟不同锚杆长度下围岩的应力分布规律,并基于D-P屈服准则得出围岩塑性区的范围。研究结果表明,采用锚杆与洞周支护力联合支护,更能充分发挥围岩自身的承载能力。锚杆的支护长度应不小于无支护时的松动区外包半径大小。松散围岩条件下,锚杆的长度不宜小于隧洞跨度的1/5,综合支护时洞周支护力大小宜为原岩垂直应力的5%左右。对比试验与有限元模拟结果,有限元模拟所得结果相比于试验较为保守。

Model test research on influence of earth tunnel support patterns on stability of surrounding rock

Based on similarity theory, sand is used to simulate surrounding rock and iron wire is used to simulate rock bolt. The paper conducts actual measurement on the change rules of stress distribution, stability and regionalization of surrounding rock under different supporting forces of surrounding rock, different lengths of rock bolt and combined action of rock bolt and tunnel around supporting force during the excavation process of tunnels. Finite element modeling is used to simulate the stress distribution laws of surrounding rocks with different bolt lengths, and the range of surrounding rock plastic zone is acquired based on Drucker-Prager (D-P) yield criterion. The study shows that the carrying capacity of surrounding rock can be brought into full play through combined support of rock bolt and supporting force of surrounding rock. The supporting length of rock bolt should be no less than the external radius size of loose zone without any support. Under the condition of loose surrounding rock, the rock bolt length should be no less than one fifth of the tunnel span; and during comprehensive support process, the supporting force of surrounding rock should be about 5% of the vertical stress of primary rocks. By comparing the simulated results of the experiment and finite element modeling, the latter result is more conservative than the former one.