考虑黏聚力及不完全拱效应的太沙基松动土压力

Terzaghi Loosening Soil Pressure Considering Cohesion and Partially Mobilized Arching

考虑滑移面上主应力旋转和埋深对侧向土压力系数的影响,基于摩尔-库伦(Mohr-Coulomb)破坏准则推导黏聚力存在时滑移面上的侧向土压力系数,进而采用微分土条极限平衡方法推导滑移面上的竖向应力。在此基础上,假设小主应力轨迹为圆弧,进而推导不完全拱效应作用下滑移面间的竖向应力分布及平均竖向应力。结果表明:与传统太沙基(Terzaghi)松动土压力公式及其现有修正公式相比,本文推导的滑移面上的竖向应力受黏聚力和内摩擦角的影响更加显著,且滑移面上的主应力旋转会放大二者对滑移面上竖向应力的影响;黏聚力对滑移面间竖向应力及侧向土压力系数的横向分布具有相同的影响规律,即黏聚力越大,二者的非线性分布特征越显著;以小主应力轨迹为圆弧所得出的滑移面间竖向应力分布规律与杨明辉等的原位测试结果基本吻合,且活门上的平均竖向应力与Chevalier等的试验结果较为吻合。

With principle stress rotation on the slip surface and burial depth being taken into account,the coefficient of lateral earth pressure on shearing planes is derived by adopting Mohr-Coulomb criterion,and the vertical stress on shearing planes is deduced with the differential soil strip limit equilibrium method.Further,vertical stress distribution and average vertical stress between shearing planes are deduced with circular arc being selected as the minor principal stress trajectory to embody the effect of partially mobilized arching.The results demonstrate that:Vertical stress on shearing planes derived in this paper,compared with the traditional Terzaghi loosening earth pressure equation and its existing modified equations,is more dramatically influenced by soil cohesion and internal friction angle and both factorsinfluences are enhanced by principle stress rotation;Soil cohesion exerts the same impact on the distributions of vertical stress and coefficient of lateral earth pressure between shearing planes,namely greater soil cohesion leads to more prominent non-linear distributions;Vertical stress distribution between shearing planes obtained from taking the minor principal trajectory as arc is generally consistent with the in-situ test results of Yang Minghui et al.and average vertical stress above trap door also fits well with the experimental data from Chevalier et al.