(1. School of Civil Engineering，Xi?an University of Architecture and Technology，Xi?an，Shaanxi 710055，China；2. Shaanxi Key Laboratory of Geotechnical and Underground Space，Xi?an University of Architecture and Technology，Xi?an，Shaanxi 710055，China；3. School of Highway，Chang?an University，Xi?an，Shaanxi 710064，China)
Abstract：The mechanical properties of loess are very sensitive to the change of the water content，and the immersion of water-sensitive loess stratum has obvious influence on its engineering structure. In order to study the influence of the collapsibility of large-thickness loess stratum induced by immersion on the subway tunnels，a model box which can reproduce the conditions of basement and surface immersion was developed，and the tests of tunnel mechanical response under different immersion conditions were carried out systematically. The influence mechanism of loess immersion on subway tunnels was studied，and the control standard of residual collapse settlement of the foundation was suggested. The results show that，with the increase of the immersion depth，the redistribution of the soil pressure around the tunnel will be caused by the local immersion of the foundation and the surface，and that the variation trend of the soil pressure is not uniform. The soil pressure decreases with the immersion depth under the condition of foundation all-range immersion but increases with the immersion depth in the case of surface all-range immersion. The change trend of the soil pressure of the both cases is relatively uniform. Foundation local immersion leads to a local decrease of the bearing capacity and hence，results in an irregular change of the bending moment of the tunnel lining. The uniform immersion of the whole basement leads to a uniform decrease of the bearing capacity，and the bending moment at each point of the tunnel lining changes relatively uniformly. The strength of the stratum above the tunnel losses partly due to local immersion，and the load gradually acts on the lining of the tunnel which causes a rapid increase of the bending moment of the lining. The bending moment increases with increasing the immersion depth under surface uniform immersion condition. The horizontal and vertical displacements of the tunnel are obvious when the foundation and the surface are partially immersed. When the foundation or the surface is fully immersed，the vertical displacement is predominant but the horizontal displacement is not obvious. The tunnel displacement caused by the foundation immersion is larger than that caused by the surface immersion. The differential settlement caused by the local uneven immersion will have an additional twisting effect on the tunnel，which is more harmful to the tunnel. When the collapsible layer of the tunnel foundation is 30 cm，only 10 cm of collapsible soil has little effect on the whole tunnel. It is suggested that the residual collapse settlement of 10 cm is allowed and the treatment depth of the collapsible foundation is 20 cm. The research results can be used for reference in the preliminary design and post operation of subway tunnels in large thickness loess area.
张玉伟1，2，宋战平1，2，翁效林3，谢永利3. 大厚度黄土地层浸水湿陷对地铁隧道影响的模型试验研究
[J]. 岩石力学与工程学报, 2019, 38(5): 1030-1040.
ZHANG Yuwei1，2，SONG Zhanping1，2，WENG Xiaolin3，XIE Yongli3. Model test study on influence of the collapsibility of large thickness loess stratum on subway tunnels. , 2019, 38(5): 1030-1040.
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2019, Vol. 38 
