土体抗剪强度指标对开挖卸荷引起隧道变形影响

Effect of Soil Shear Strength Index on Tunnel Deformation Due to Stress Relief

在文献报道的离心模型试验的基础上,采用有限元方法,分析了土体的抗剪强度指标(土体的黏聚力和内摩擦角)对基坑开挖卸荷引起隧道变形的影响。研究结果表明,土体的抗剪强度指标对隧道顶部隆起影响不大(3%);对隧道的横截面衬砌变形和隧道横截面弯曲应变影响较小。土体抗剪强度指标值越大,隧道纵向附加弯曲应变越小。在土体抗剪强度指标值正常变化范围内,其对基坑开挖卸荷引起邻近已建隧道的影响大小变化为5%～10%。研究成果可为工程实践中初步设计时的参数选取提供科学依据和理论基础。

Correctly predicting tunnel deformation is of great theoretical and practical significance for ensuring the safety of subway tunnels.In engineering practice,there are still many cases by conducting numerical analysis using elastic-perfectly plastic model based on Mohr-Coulomb criterion.To facilitate the engineers to select soil shear strength parameters,finite element method were conducted to analyze the effect of soil shear strength index(cohesive and internal friction angle)on tunnel deformation due to stress relief based on the centrifuge model test reported in the literature.The results show that soil shear strength index has only a little effect on the tunnel heave(less than 3%).It has little influence on tunnel diameter change and bending strain in tunnel transverse direction.The larger the shear strength index of the soil is,the smaller the tunnel additional longitudinal bending strain will be.In the normal variation range of the soil shear strength index,the influence value is 5%~10%.The research results can provide scientific and theoretical basis for parameter selection in preliminary design of engineering practice.