Experimental investigation of face instability for tunnels in sandy cobble strata  

作　　者：Qiguang Di Pengfei Li Mingju Zhang Xiaopu Cui 

机构地区：[1]Key Laboratory of Urban Security and Disaster Engineering,Ministry of Education,Beijing University of Technology,Beijing 100124,China

出　　处：《Underground Space》2023年第3期199-216,共18页地下空间（英文）

基　　金：the financial support provided by Natural Science Foundation of China(Grant Nos.51978019,52278382);Beijing Natural Science Foundation,China(Grant No.8222004).

摘　　要：In order to investigate the influence of face instability for tunnels with different burial depths in sandy cobble strata on earth pressure and the instability region,geomechanical model tests and numerical simulations were performed.The continuous excavation method was adopted to reduce the pressure of the soil bin and restore the real engineering situation.Earth pressure in three directions of the obser-vation section in front of the tunnel face was monitored during the tunneling of the shield.Evolutions of the lateral stress ratios at dif-ferent stages were also investigated.The instability area of the shield tunnel face in sandy cobble strata with different burial depth ratios during the instability stage was obtained based on the change ratio of earth pressure and compared with existing researches.The earth pressure began to change when the excavation was one shield diameter away from the observation section,and when the excavation reached the observation section,the earth pressure decreased significantly.The burial depth of shield tunnel in the sandy cobble strata has a significant impact on the evolution of soil arch and the size of the failure area.The numerical simulation of the continuum medium cannot reflect the stress redistribution characteristics of the granular body like sandy cobble strata,and the failure area or stress distur-bance area obtained by the model test is larger than the numerical simulation result.Existing methods have deviations in analyzing the failure area of shield tunnel face in sandy cobble strata.It provides not only guidance for shield tunnel excavation engineering in sandy cobble strata,but also a reference for the theoretical research on failure areas.

关 键 词：Geomechanical model test Sandy cobble strata Face stability Arching effect Shield tunnel 

分 类 号：U45[建筑科学—桥梁与隧道工程]