原状与重塑黄土冻融过程渗透特性对比试验研究

摘要

通过冻融条件下西安Q3原状和重塑黄土的电镜扫描观测和三轴固结渗透试验,对比分析了冻融作用对原状和重塑黄土渗透特性的影响规律.结果显示:冻融条件下原状与重塑黄土微观结构均发生明显变化,土体胶结连接强度变差且颗粒排列更加松散,孔隙比增加,渗透性增强.冻融作用对原状和重塑黄土表面结构破坏均较严重,但原状黄土表面结构破坏程度较重塑黄土更为强烈;冻融过程产生的裂缝使得土中水分渗流和迁移的通道形成,导致原状与重塑黄土体渗透性增强.冻融条件下原状与重塑黄土渗透系数随含水率增加均先增大后减小,表现出抛物线变化特征;渗透系数随冻融次数增加均先增大然后趋于稳定,表现出指数增大特征;渗透系数随围压增大均先减小然后趋于稳定,表现出指数下降特征;相同条件下原状黄土渗透系数高于重塑黄土;原状与重塑黄土渗透系数差异随围压增大逐渐减小.%The influence of freeze-thaw action on the permeability of undisturbed and remolded Q3 loess in Xi'an city is comparatively studied by the SEM and triaxial consolidation permeability tests.The experimental data indicates that the microstructure of undisturbed and remolded loess all changes significantly under freezing-thawing condition.The soil cementation structure is weakened,and then the particle alignment becomes more loose.Finally,the void ratio of soil increases and makes the permeability enhanced.Freezing-thawing makes the surface structure of undisturbed and remolded loess destroyed greatly,and has a bigger influence on the undisturbed loess.The cracks produced by freezing-thawing process become the main channel for water flow and migration,resulting in the obvious increase of permeability for undisturbed and remolded loess.With the increment of water content,the permeability coefficients for undisturbed and remolded loess all firstly increase and then decrease under freeze-thaw cycle condition,complying with the parabola law.With the increase of freezing-thawing times,the permeability coefficients all firstly increase and finally approach to a steady state,following the exponential rule.With the increment of cell pressure,the permeability coefficients all firstly decrease and finally reach a steady state,also following the exponential rule.The permeability of undisturbed loess is always greater than that of remolded loess under the same condition.Moreover,the permeability coefficient difference between undisturbed and remolded loess is smaller with the increase of cell pressure.