基于尖点突变理论的大凉山隧道断层带渗流/爆破开挖时围岩稳定性研究

Study on Surrounding Rock Stability of Seepage Tunnel Blasting Excavation in a Fault Zone Based on Cusp Mutation Theory

依托四川省乐西高速大凉山^(#)2隧道项目,基于尖点突变理论所提出的失稳判据对围岩稳定性进行判定,采用有限元软件MIDAS GTS NX建立相关隧道开挖模型,研究了隧道—断层系统在地下水渗流和爆破条件下围岩应力、位移和最大振速峰值的变化情况。结果表明,通过失稳判据计算发现,围岩综合刚度比k<1,分岔集方程Δ<0,两者结果均表明围岩具有失稳风险;渗流条件下断层围岩最大主应力为27.71 MPa,拱顶位移沉降为307.83 mm,应力比非断层处增加了约20.64%,位移增加了105.21%,受爆破因素影响,断层处竖向最大振速峰值是普通围岩的13倍左右,达到了162.97 cm/s,可见断层的存在会对其周边围岩动力响应产生放大效应;理论计算和数值模拟结果均表明大凉山隧道F3断层处具有失稳风险,施工时应当提前采取相应的防范措施。

Based on the instability criterion proposed by the cusp catastrophe theory,the whole surrounding rock was judged,and the relevant tunnel excavation model was established by using the finite element software MIDAS GTS NX,and the changes in surrounding rock stress,displacement and maximum vibration velocity peak in the tunnel-fault system under the conditions of groundwater seepage and blasting were studied by taking No.2 tunnel project of Daliangshan in Lexi Highway of Sichuan Province for an example.The results show that the comprehensive stiffness ratio of the surrounding rock k1 and the bifurcation set equation Δ0 are found by the calculation of the instability criterion,both of which indicate that the surrounding rock has the risk of instability.Under the seepage condition,the maximum principal stress of the fault surrounding rock is 27.71 MPa,and the displacement settlement of the vault is 307.83 mm.Compared with the non-fault area,the stress increases by about 20.64%,and the displacement increases by 105.21%.Influenced by blasting factors,the maximum vertical peak vibration velocity at the fault area is about 13 times that of the common surrounding rock,it is up to 162.97 cm/s.It can be seen that the existence of a fault will have an amplification effect on the dynamic response of surrounding rock.Both theoretical calculation and numerical simulation results show that the F3 fracture of the Daliangshan Tunnel has the risk of instability,and corresponding preventive measures should be taken in advance during construction.