基于强度测试结果的压实膨胀土有效应力参数OA

The effective stress parameter χ quantifies the efficiency with which suction was converted into effective stress;clarifying its variation pattern and reliable test methods remains one of the core challenges in unsaturated soil mechanics.Because χ was extremely difficult to measure directly,experimental data were scarce.Using a complete set of measured shear strength and suction data obtained for a compacted yellow-brown expansive soil from Jingmen,the dependencies were established among χ,net stress,suction,void ratio e,and gravimetric water content w.The results showed that:① Moisture effect:At a given density,χ increased with w,indicating that the efficiency of converting suction into effective stress rises with increasing water content.② Density effect:At a fixed moisture level,χ rised markedly as e decreased,demonstrating strong density dependence-higher density significantly enhances the suction-to-stress conversion efficiency.③ Stress effect:Under constant e and w,χ increased with vertical net stress,implying that the external stress state also influences χ;the mechanism was analogous to the density effect because greater vertical stress induces specimen compaction.④ Peak("mountain")effect:Unsaturated shear strength exhibited a"peak phenomenon"because χ increased whereas matric suction decreased with rising moisture.At low moisture,χ was small and suction was large;at high moisture,χ was large and suction was small.Consequently,suction-induced strength reached a maximum over the full transition from saturation to air-drying,producing a corresponding peak in unsaturated shear strength.⑤ Research outlook:Because χ was closely linked to density,moisture and stress state,developing more rational quantitative descriptions of these interrelations warranted further investigation.