软弱围岩小净距隧道动态施工力学行为分析

基于新奥法施工理念,结合某大跨度、小净距隧道工程浅埋段施工过程,根据采取的双侧壁施工方法,建立了数值模型,对其施工过程进行了三维有限元弹塑性模拟。分析了施工过程中随着各部的开挖,隧道周边各点竖向位移的变化;通过对开挖后地表沉降、支护受力和塑性区的模拟计算以及隧道拱顶沉降监测值与计算值的对比分析,进而对施工过程中隧道结构的安全性及围岩稳定性作出评价。数值计算结果表明,在软岩浅埋隧道中,超前小导管的设置可起到加固围岩和抑制隧道变形的作用,有效控制双线隧道开挖引起的反复扰动是小净距隧道施工成败的关键。

Dynamic construction mechanics analysis of small-distance tunnel in soft and weak rocks

Based on the construction theory of NATM and combined the construction process of long-span, small distance tunnel project, the numerical model has been formulated for the double-sidewalls to simulate 3D FEM elastoplastic of the construction process. The vertical displacement surrounding the tunnel along with the changes of its excavation has been analyzed. Through analyzing the surface subsidence, the force of support, the plastic zone and tunnel vault monitoring of the comparison with the calculated values after digging, the safety of the tunnel structure and stability of surrounding rock are assessed. The result of numerical simulation shows that the set of small pilot pipe in shallow-embedding tunnel can reinforce surrounding rock and control the tunnel deformation, and the effective control of two- lane tunnel repeated disturbances caused by excavation is the key to the construction of the small-distance tunnel.