线性吸力下非饱和土地基临界荷载统一解

Unified solution of critical load for foundation in unsaturated soils under linear suction

基于非饱和土的平面应变抗剪强度统一解,考虑基质吸力与中间主应力的共同影响,建立线性吸力分布下能适用于任意侧压力系数的非饱和土地基临界荷载统一解,并进行可比性及参数影响分析。所得临界荷载统一解可退化为众多特别是均布吸力下的已有解,具有广泛的适用性。研究结果表明:基质吸力及其分布对临界荷载的影响显著,且线性吸力下的影响不如均布吸力时明显;临界荷载的强度理论效应重要,基于Mohr-Coulomb强度准则结果的基础设计及施工理论上偏保守;对于正常和一般超固结非饱和土,按侧压力系数为1得到的临界荷载偏高;应充分考虑中间主应力效应、选择合适的侧压力系数、实测吸力及分布并采取有效措施保证其稳定存在。所得结果可为非饱和土地基承载力确定及基础优化设计提供一定的理论指导,具有广阔的工程应用前景。

On the basis of the unified solution of shear strength for unsaturated soils in the plane strain condition, a unified solution of critical load for foundation in unsaturated soils under linear suction was derived, which took both matric suction and intermediate principal stress into account and was suitable for any lateral pressure coefficient. Comparability analysis and parametric studies were carried out. The unified solution of critical load obtained in this study can be reduced to many existing results, particularly for uniform suction, and thus has a broad applicability. The results show that the effect of matric suction and its distribution on critical load is significant, and the effect with linear suction is not as obvious as that with uniform suction; the strength theory effect for critical load is important, and the design and construction of foundation with use of Mohr-Coulomb failure criterion are theoretically conservative; for unsaturated soils under normal consolidation or general over-consolidation, the critical load with lateral pressure coefficient of 1 is higher; the intermediate principal stress effect should be fully considered and an appropriate lateral pressure coefficient is to be chosen; the matric suction and its distribution should be monitored in situ and some effective measures are adopted to ensure the stability of matric suction. This proposed result can provide a theoretical basis for the bearing capacity determination and optimization design of foundation in unsaturated soils, and therefore has a good prospect of engineering applications.