水毁条件下盐渍土强度水敏性演化规律研究

Research on Evolution Law of Strength Water Sensitivity of Saline Soil under Water Damage Condition

近年来由于洪水水流不断浸润、冲刷盐渍土地区路基边坡,在水和盐的共同作用下,柴达木盆地内公路受水毁威胁日益严峻。针对盐渍土路基边坡土质条件开展了直剪试验,研究了盐渍土在浸泡条件下的强度水敏性演化规律;基于泥砂起动理论分析了盐渍土颗粒运动受力特征,提出了格(尔木)茫(崖)公路盐渍土临界起动切应力公式,分析了盐渍土起动切应力变化规律。结果表明:在饱水浸泡条件下,不同浸泡时间盐渍土抗剪强度差异明显;随着浸泡时间的增加,盐渍土抗剪强度及参数降低显著。另外:饱水浸泡条件下,随干密度增大,抗剪强度增大;随NaCl的掺入土颗粒周遭的水膜厚度被改变,抗剪强度降低;随Na_(2)SO_(4)的掺入,土体吸水后生成芒硝、填充土体孔隙,自由水转化为芒硝结晶水、土体中含水率降低,均使抗剪强度增大。该研究成果可为盐渍土路基边坡冲刷水毁防治和修复提供理论依据。

In recent years,due to the continuous infiltration and erosion of roadbed slope in saline soil area by flood water and salt,the roads in Qaidam Basin is increasingly threatened by water damage.A direct shear test has been carried out for the soil conditions of the saline soil roadbed slope,and the evolution law of the water sensitivity to strength of the saline soil under soaking conditions is studied.Based on the sediment incipient theory,the motion force characteristics of the saline soil particles are analyzed,and the critical incipient shear stress formula of the saline soil on the Golmud-Manya Road is proposed,and the change law of the starting shear stress of the saline soil is analyzed.The results show that:(1)under saturated soaking conditions,the shear strength of saline soil varies significantly with different soaking time.The shear strength and parameters of saline soil decrease significantly with the increase of soaking time.(2)Under saturated soaking conditions,the shear strength increases with the increase of dry density.With the addition of NaCl,the thickness of the water film around the soil particles is changed,and the shear strength decreases.With the addition of Na_(2)SO_(4),the soil absorbs water to form glauberite,fills the pores of the soil,converts the free water into glauberite crystal water,reduces the moisture content of the soil,and increases the shear strength.The research results can provide theoretical basis for the prevention and repair of erosion and water damage of saline soil subgrade slope.