An effective stress equation for unsaturated silt considering the microstructure of pore water and its verification
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摘要:
有效应力参数的合理确定是非饱和土有效应力研究的重要内容。然而，现有的有效应力参数未能较好地考虑孔隙水的微观赋存形态对有效应力的影响。为此，分析了孔隙水的微观赋存形态，明确了孔隙水可分为收缩膜、吸附水和毛细水，建立了非饱和粉土的扩展三相孔隙介质模型，即孔隙气、毛细水和广义土骨架。基于该模型，采用分相平衡分析法，推导了非饱和粉土的有效应力方程，该方程通过采用毛细水有效饱和度合理地考虑了毛细水对有效应力的影响。依据推导的有效应力方程，提出了非饱和粉土的抗剪强度公式。采用5种不同围压下重塑非饱和粉质黏土试验数据验证了提出的公式。结果表明：与现有的抗剪强度公式相比，本次提出的公式更好地预测了重塑非饱和粉质黏土的抗剪强度随基质吸力的变化规律。因此，运用提出的抗剪强度公式评价非饱和土边坡稳定性、地基承载力和挡土墙稳定性将会取得更好的效果。
Abstract:Accurate determination of the effective stress coefficient is an important thing in the study of the effective stress of unsaturated soils. However, the existing effective stress coefficients have not well considered the effect of the microscopic occurrence of pore water in unsaturated soils on the effective stress. For this reason, the microscopic occurrence of pore water is analyzed firstly. It is recognized that the pore water in unsaturated soils can be divided into the contractile skin, adsorbed water and capillary water, and an extended three-phase porous medium model of unsaturated silt is established, considering the pore air, capillary water, and generalized soil skeleton. Based on the established model, an effective stress equation for unsaturated silt is derived by using an independent phase balance approach. The equation reasonably considers the influences of the capillary water on the effective stress by adopting a coefficient (i.e., the effective saturation of capillary water). In light of the derived effective stress equation, a shear strength equation for unsaturated silt is proposed. Finally, the proposed shear strength equation is verified by the experimental data on a reconstituted unsaturated silty clay under five different net confining pressures. The results show that compared with the existing two shear strength equations, the proposed equation better predicts the variation of the shear strength of the reconstituted unsaturated silty clay with matric suction. Therefore, under the unsaturated conditions, using the proposed shear strength formula to evaluate the stability of slopes, the bearing capacity of foundation, and the stability of retaining wall will achieve better results.
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Key words:
- unsaturated silt /
- pore water /
- microscopic occurrence /
- effective stress /
- shear strength /
- SWRC
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