互层软质岩隧道系统锚杆支护效用数值模拟研究

Numerical Simulation Study on the Supporting Effect of Bolts in Interbedded Soft Rock Tunnel

依托重庆高速公路某隧道工程建立地层结构法数值计算模型,对深埋Ⅳ级软质岩互层隧道系统锚杆的效用开展仿真分析研究,重点考虑系统锚杆布设范围及锚杆长度影响因素,将隧道初期支护结构锚杆设置分为6种工况,对比分析了各工况隧道围岩变形及塑性区、锚杆轴力、初期支护轴力表现出的特征。研究表明:(1)系统锚杆轴力较小,对围岩变形、支护结构受力及围岩塑性区发展均有一定的控制效果,但支护功效不明显;(2)隧道边墙设置的锁脚锚杆发挥效用较大且控制围岩水平收敛变形效果明显,因此取消施作系统锚杆的前提务必保证锁脚锚杆施作质量;(3)对于深埋泥岩、砂岩互层的Ⅳ级软质围岩隧道工程,通过科研试验段论证和工程类比验算满足规范要求的技术安全条件,软质岩隧道中的系统锚杆可以取消;(4)系统锚杆在深埋Ⅳ级软质岩互层隧道中的效用不明显,取消施作系统锚杆可减少施工工序,且有利于围岩和初期支护及时封闭和隧道结构受力变形控制。

Based on a tunnel project of Chongqing Expressway,the numerical calculation model of stratum structure method is established,and the effect of system bolts in deep buried gradeⅣinterbedded soft rock tunnel is simulated and analyzed.Considering the influence factors of system anchor distribution range and bolt length,the bolts setting types of tunnel initial support structure are divided into six simulated calculation conditions.The characteristics of surrounding rock deformation and plastic zone,bolt axial force and initial support axial force of tunnel in different simulated calculation conditions were compared and analyzed,and the following conclusions were obtained:(1)The axial force of the system bolt is small,which has certain control effect on surrounding rock deformation,supporting structure stress and surrounding rock plastic zone development,but the support effect is not obvious;(2)The feetlock bolts set on the side wall of the tunnel has a large effect and the effect of controlling the horizontal convergence deformation of surrounding rock is obvious.Therefore,the quality of the feet-lock bolts must be guaranteed before canceling the system bolt;(3)For the tunnel project of gradeⅣsoft rock with deep buried mudstone and sandstone interbedding,the system bolts in the tunnel of soft rock can be cancelled through the demonstration of scientific research test sections and engineering analogy checking to meet the technical safety conditions required by the codes;(4)The effect of system bolt in deep buried gradeⅣinterbedded soft rock tunnel is not obvious,and canceling the application of system bolts can reduce the construction process,close the initial support in time,and facilitate the deformation control of tunnel structure.