大拱脚三台阶法开挖浅埋软弱红黏土隧道的力学特性及适用性研究  

Applicability & mechanical characteristics of shallow buried soft red clay tunnel under 3-step benching tunneling method with large arch feet

作　　者：刘聪[1] 彭立敏[1] 雷明锋[1] 施成华[1] LIU Cong;PENG Limin;LEI Mingfeng;SHI Chenghua(School of Civil Engineering,Central South University,Changsha 410075,China)

机构地区：[1]中南大学土木工程学院

出　　处：《铁道科学与工程学报》2019年第8期2006-2017,共12页Journal of Railway Science and Engineering

基　　金：国家自然科学基金资助项目(51508575,U1734208)

摘　　要：依托渝黔铁路青冈山隧道工程,针对软弱红黏土自稳能力差、承载能力低的特点,原设计采用CRD法进行开挖,以减小围岩变形。为进一步提高作业效率,在三台阶法的基础上采取增设管棚、大拱脚等改进措施,并通过数值模拟分析2种不同工法下软弱红黏土隧道开挖后的力学特性。研究结果表明:采用改进的大拱脚三台阶法开挖,隧道拱顶沉降比CRD法增大165.90%,与此同时,初期支护第1和第3主应力也分别增大17.99%和24.59%,但是隧道拱顶沉降以及初期支护应力均满足相关要求,施工现场沉降监测数据与数值模拟所得结果较为吻合,验证了软弱红黏土隧道采用大拱脚三台阶法开挖的合理性,同时建议隧道开挖避开雨期施工,以降低围岩失稳风险。Based on the Qinggangshan tunnel project of Chongqing-Guizhou railway,according to the undesired stability and low bearing capacity of soft red clay,the CRD method was adopted in the original design.Then the modified three steps benching tunneling method by adding pipe shed and large arch feet was suggested to improve the efficiency of excavation,and the mechanical characteristics of the soft red clay tunnel under two different methods were analyzed by numerical simulation.The results reveal: when the three-step benching tunneling method with large arch feet is adopted,the settlement of the tunnel vault increases 165.90%,and the maximum and minimum principal stresses of the initial support are 17.99% and 24.59% greater than the CRD method,respectively;however,the settlement & stresses of the tunnel excavated by three-step benching tunneling method still satisfies the safety requirement.The field measurement of tunnel’s displacements is in good agreement with the numerical simulation results,which verifies the rationality of three-step benching tunneling method;further,excavation should be avoided in the rainy period so as to reduce the risk of surrounding rock instability.

关 键 词：红黏土 大拱脚三台阶法 CRD 法 沉降 

分 类 号：U25[交通运输工程—道路与铁道工程]