考虑中间主应力的非饱和土上埋式涵洞竖向土压力公式

Formulation of Vertical Earth Pressure Against Positive Buried Culvert in Unsaturated Soils Considering Intermediate Principal Stress

基于非饱和土的平面应变抗剪强度公式,考虑中间主应力和基质吸力的共同影响,分别建立了均匀与线性2种吸力分布下非饱和土上埋式涵洞的竖向土压力公式,并对其进行可比性分析,对比文献数值模拟和模型试验进行正确性验证,最后探讨了各参数的影响特性。研究结果表明:所建立的上埋式涵洞竖向土压力公式为系列化的有序解析解,可退化为文献已有解答并包含众多新解答,并能计算涵顶上方不同高度处的竖向土压力,工程应用前景广泛;基质吸力对涵顶竖向土压力具有重要影响,且线性吸力影响不如均布吸力明显,应考虑回填土的非饱和特性并实测吸力分布;中间主应力效应随基质吸力和填土高度的增大而更加显著,同时均布吸力下中间主应力效应较明显,应合理选取强度准则以反映回填土强度的中间主应力作用;等沉面高度与回填土物理力学性质、中间主应力效应、基质吸力及分布形式等有关;基质吸力及其分布影响、中间主应力效应均与填土高度密切相关,体现了多因素对涵顶竖向土压力的综合影响。

Based on the shear strength equation of unsaturated soils in the plane strain condition to account for interaction influences of intermediate principal stress and matric suction,the formulations of vertical earth pressure against positive buried culvert in unsaturated soils under uniform and linear distributions of matric suction were established,respectively.Comparability analysis of the proposed formulation was then carried out.Comparing validations against numerical simulations and model tests reported in the literature were performed,and parametric studies were finally discussed.The study results show that the proposed formulation of vertical earth pressure is a series of orderly analytical solutions,which can reduce to available results and involve many new ones to calculate vertical earth pressure at different depths above the culvert top.Therefore,the proposed formulation has good comparability and broad applicability.The influence of matric suction on vertical earth pressure at the culvert top is significant,and the influence of linear suction is not as obvious as that of uniform suction,so the unsaturated characteristics of backfill soils should be considered and suction distributions should be field measured.The influence of intermediate principal stress on vertical earth pressure increases with matric suction and backfill soil height and is more obvious for uniform suction,so a reasonable strength criterion should be adopted to describe the influence of intermediate principal stress on backfill soil strength.The height of equal settlement plane is dependent on physical and mechanical properties of backfill soils,intermediate principal stress,matric suction and its distribution.The influence of matric suction and its distribution as well as the influence of intermediate principal stress are closely related to backfill soil height,which indicates comprehensive influences of multiple factors on vertical earth pressure at the culvert top.