西安市承压含水层高压渗透模拟试验研究

Simulated Study on High-pressure Penetration in Confined Aquifer of Xi'an

为了揭示在地下水头升降过程中西安市承压含水层的物理及力学性质,采用自行设计的高压渗透固结试验设备模拟西安市承压含水层中细砂高压渗透,研究了在不同竖向压力和孔隙水压力条件下砂柱应变与时间的关系、应力与应变的关系以及砂样的渗透性,同时对比探讨了试验前后砂样微观结构。结果表明:孔隙水压力降低或竖向压力增大时,砂柱发生压缩变形且表现出分段线性的特点;在一定应力范围内,增大孔隙水压力,砂柱变形几乎没有发生回弹或者恢复。根据试验前后颗粒分析曲线、双目镜照相及电镜扫描照片的对比,可以推断砂样在压缩过程中除产生颗粒滑移和位置调整外,部分颗粒被压碎或压裂,由此导致了砂样在地下水头升降过程中颗粒级配发生改变、渗透系数急剧降低以及砂样在不同应力下表现出的分段线性、粘滞性和部分不可恢复等非完全弹性性质。

In order to reveal the physical and mechanical properties of soil in confined aquifer of Xi＇an when groundwater head changes,high-pressure infiltration and consolidation test system was designed to simulate the high-pressure penetration of medium-fine sand in confined aquifer of Xi＇an.Relationships between strain and time,and strain and stress of sand column under different vertical pressure and pore water pressure were discussed;penetrability of sand sample was analyzed;and microstructures of sand samples before and after the test were compared.The results showed that sand column characterized compression deflection and piecewise linearity,when pore water pressure deceased or vertical pressure increased;deflection of sand column could not resile when pore water pressure increased in a certain limit of stress.According to the comparison of the test curves before and after the particle analysis,and the photographs of binocular microscope and electron scanning microscope before and after the tests,it was estimated that the sand sample characterized particle slides,position adjustment and particle crushed or fractured partly in the compression process.It caused particle composition changing and permeability coefficient sharply decreasing in the process of groundwater head change and the sand sample characterized imperfectly elastic,such as piecewise linearity,treacliness and partly irrecoverable.