摘要
为控制深基坑降水和承压水降压引起的土体沉降问题,通常采用坑外回灌措施,而软黏土渗透特性在抽水回灌过程中出现的变化会影响回灌效果和土体变形特性。采用GDS三轴试验仪对上海黏土土样进行室内降压回灌模拟试验,研究降压回灌的渗流作用对黏土渗透特性的影响规律。试验通过设置围压和初始孔压来控制土样应力水平,利用反压变化模拟孔隙水的降压和回灌过程,测试土样的渗流变化与变形,从而分析土样孔隙比、渗透系数等参数的变化规律。研究发现,渗透系数在降压阶段因孔隙比减小而降低,并存在非线性关系;土体孔隙比在回灌阶段逐渐增大,但渗透系数因堵塞效应而呈现进一步降低趋势;可用e–lgk拟合曲线建立孔隙比与渗透系数之间的非线性关系。
For controlling the settlement caused by dewatering of deep foundation pits, the method of recharging is usually adopted. But the permeability coefficient of soft clay may change along with the variation of void ratio during the pumping and recharge, and it will affect the results of recharging and deformation characteristics of soils. For studying the permeability characteristics of Shanghai typical soft clay under the effect of pumping and recharge, the pumping and recharge tests were carried out on the soft clay by using the GDS triaxial apparatus. During the tests, the soil stress level is controlled by setting the radial pressure and initial pore pressure. Meanwhile, the process of pumping and recharge is simulated by changing the back pressure. The void ratio and permeability coefficient are obtained by dealing with the experimental results and data. The study shows that the permeability coefficient has a nonlinear relationship and a decreasing trend along with the decrease of void ratio during the pumping. During the recharge, with the increase in void ratio, the permeability coefficient has a decreasing trend due to the blockage effect and is smaller than that at the pumping stage. Meanwhile, the nonlinear relationship between permeability coefficient and void ratio can be fitted using the function of e–lgk.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2015年第S1期21-25,共5页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金项目(41330633)
国土资源部公益性行业科研专项经费项目(201311045-03)
关键词
黏土
降压回灌
模拟试验
孔隙比
渗透性
堵塞效应
soft clay
pumping and recharge
simulation test
void ratio
permeability
blockage effect
