Influence mechanism of water content on tunnel stability in silty clay layer
MA Kaimeng1，ZHANG Junru1，XU Jian1，CHEN Xuefeng2，REN Zhaodan2，FENG Jimeng1
(1. School of Civil Engineering，Southwest Jiaotong University，Chengdu，Sichuan 610031，China；2. China Railway Siyuan Survey and Design Group Co.，Ltd.，Wuhan，Hubei 430063，China)
Abstract：The water content of silty clay stratum varies widely and greatly affects the mechanical properties. The water content of silty clay stratum has great influence on tunnel stability. Thus，based on Dayingpo tunnel of Yangliu-Xuanwei expressway，the influence of water content change on the stability of tunnels in silty clay stratum was studied. Firstly，the deformation characteristics and deformation mechanism of the unstable section of Dayingpo tunnel were analyzed. The mechanical parameters of silty clay with different water content were obtained by triaxial compression test. Secondly，based on the experimental data，the influence mechanism of silty clay water content change on tunnel stability was studied by numerical calculation method. Finally，the criterion for determining the instability of silty clay tunnel was proposed. The results show that：(1) the silty clay in this area has strong water sensitivity，and its mechanical properties deteriorate significantly with the increase of water content. When the water content reaches 40%，its shear strength and elastic modulus are only 10%–20% of that when water content is 15%. The increase of water content causes the overall settlement of the tunnel，and the maximum settlement of dayingpo tunnel is 76.7 cm. (2) According to the water content，the stability of silty clay tunnel can be divided into four stages：stable stage(15%–25%)，early warning stage(25%–27.5%)，alarm stage(27.5%–wcr) and unstable stage(＞wcr). (3) The increase of water content of surrounding earth in the arch foot area leads to insufficient foundation bearing capacity and insufficient support resistance，which is the main reason for overall subsidence，misplacement and serious intrusion of initial support.
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2023, Vol. 42 
