压实黄土在溶滤作用下的强度特性

Strength characteristics of compacted loess during leaching

为探究压实黄土Q2在溶滤作用下可溶盐对强度的影响,开展了12种应力组合的溶滤试验,测定了不同溶滤时长的离子浓度、可溶盐量与极限正应力。试验结果表明,各离子浓度、可溶盐量及极限正应力均具阶段性减少的特点。应力组合中,溶滤应力水平s影响离子和可溶盐变化曲线的形式及滞后性,σ3影响溶盐曲线的平滑度,而最终溶盐残余量与s和σ3均呈正相关。为衡量不同σ3时的溶盐溶解差异,定义了平均差异性指标ΔSc。,其值与s呈正比。为评价溶滤进程,将各溶滤阶段溶盐相对变化量定义为溶盐比Scs,其值小于1%时判定溶滤进程结束。在强度方面,极限正应力σ1f随相对可溶盐量Src的减少而减小,s决定弱化初期的剧烈程度,不同围压时σ1f值的差异性随s的增大而减弱。σ1f的这3种弱化特性表明,溶滤变形及强度弱化是可溶盐和应力组合共同作用的结果。最后,建立了考虑可溶盐与应力组合影响的强度弱化公式。

Leaching tests under 12 kinds of stress combination were carried out to explore the weakening effect of soluble salt on the strength of compacted loess(Q2)during leaching.The ion concentration,soluble salt content and ultimate normal stress with different times of infiltration were determined.The results showed that the ion concentrations,the soluble salt amount and shear strength decreased in a step-like manner during leaching.With regard to the stress combination,the leaching stress(s)affected the form and hysteresis of the curves of ion and soluble salt;the confining pressure(σ3)changed the smoothness of the curve;the soluble salt residue was positively correlated with s andσ3.To measure the difference of soluble salt content under differentσ3,the average difference index(ΔSc)was defined,and the index was positively proportional to s.To evaluate the process of leaching,the relative change amount of soluble salt content(Scs)was defined as the dissolved salt ratio.When the value Scs was less than 1%.,the leaching process was determined to be stable.In terms of shear strength,the ultimate normal stress(σ(1f))decreased with the decrease of relative soluble salt;s determined the intensity of the initial weakening;the difference ofσ1f,between different confining pressures weakened with the increase ofσ1f.The three characteristics ofσ1f indicate that the occurrences of weakened strength and deformation in the leaching process are the result of the combined action of stress and changes in the soluble salt.Finally,the strength weakening formula considering the combined effect of soluble salt and stress was established.