非饱和土体变试验研究及其在地面沉降中的应用

地下水位降低将导致非饱和土体中净平均应力和基质吸力发生变化,从而引起土体体积变化。针对重塑非饱和砂土、粉土、黏土和软土,结合土水特征曲线和收缩曲线,考察了土体在干燥收缩过程中基质吸力与孔隙比的关系;运用固结曲线分析了土体在经受净平均应力下的变形特性。基于试验结果,根据Fredlund弹性体变本构模型估算了不同的地下水位降低情况时非饱和土区域的沉降量。结果表明,在总沉降量中非饱和土区域的沉降量是不可忽略的,随着地下水位的降低,非饱和土区域的沉降量在总沉降量中所占比例逐渐增大。

Experimental Study on Volume Change of Unsaturated Soils and Its Application to Estimation of Subsidence

Drawdown of groundwater table causes change of net mean stress and matric suction in unsaturated soil and then induces volume change of the soil mass.For four types of soils including sand,silt,clay and soft clay,the empirical relationship between matric suction and void ratio on drying path is established by utilizing the shrinkage curves and the soil-water characteristic curves which are determined through experimental tests.The relationship between net mean stress and void ratio is obtained by utilizing the oedometer curve.Based on test results and the Fredlund elastic volume constitutive model,subsidence of unsaturated soil zone is estimated for different drawdown of groundwater table.Computed results indicate that in total amount of subsidence,the portion of subsidence of unsaturated soil zone cannot be overlooked.The contributions of unsaturated soil zone to total subsidence increases as drawdown increases.