大断面浅埋土质隧道施工工法优化分析

为探明大断面浅埋土质隧道在不同施工工法开挖下的变形及支护力学响应特征,寻求适用的工法,以宁安铁路钟鸣1号隧道工程为依托,采取现场试验与数值模拟相结合的方法,研究该类隧道在3种不同工法下的洞周及地表变形、围岩塑性区分布范围、初期支护及二次衬砌内力变化规律。研究结果表明：大断面浅埋土质隧道围岩变形有明显的空间效应,开挖面处预收敛变形所占比例约40%-50%;CRD法与六步CD法施工在控制洞周及地表变形方面明显优于三台阶临时仰拱法,且开挖产生的围岩塑性区分布范围小,两者均能满足围岩及支护稳定性的要求,而CRD法较六步CD法施工工期稍长、造价稍高,因此六步CD法为该类地层隧道施工的优选工法。

Optimization Analysis of Tunneling Schemes of Shallow and Large-section Soil Tunnel

In order to research the deformation of surrounding rocks and mechanical response of supporting systemof shallow and large-section tunnel in soil,and find a reasonable construction scheme system,this study combinesthe field tests and numerical simulations to present the variation laws of the deformation around the tunnel andground,distribution of plastic zone for surrounding rocks,and the internal forces in primary support and the sec-ondary lining under three different tunneling schemes.It indicates that the spatial effect of the deformation of sur-rounding rocks for shallow and large-section tunnel in soil is very obvious,and proportion of the pre-convergencedeformation at excavation face is 40%-50%.The schemes of CRD and six steps of CD are better than three-steptemporary inverted arch method in the way of controlling the deformation around the tunnel and ground,and pro-duce less surrounding rock mass plastic zone,while both two schemes can meet the requirements of stability of sur-rounding rock and support stability.Because the scheme of CRD needs a little longer construction period and costsmore,the six-step method of CD is the desirable tunneling scheme of shallow and large-section soil tunnel.