原状黄土增湿过程中的静止土压力系数变化规律试验研究

Experimental Study of Variation Rules of the Coefficient of Earth Pressure at Rest During Wetting for Original Loess

目前得到的湿陷性黄土静止土压力系数K_0,无法反映应力和含水两个因素的影响。本文开展了原状黄土增湿过程中K_0变化规律的试验研究,得到了力水耦合作用下K_0的计算方法。首先引入"增湿水平"这一概念描述土体的含水状态;开展竖向压力作用下的侧限分级浸水试验,分别研究增湿水平、基质吸力、竖向应变与K_0的相关关系;开展黄土湿陷的离心模型试验,验证室内试验结论的有效性。试验结果表明:"增湿水平"物理意义明确,能够反映土体的含水率初始情况和增湿过程;原状黄土K_0随着增湿水平的增大而线性增加,增加速率取决于竖向压力的大小,竖向压力越大增加速率越慢;增湿过程中K_0随着吸力的减小而线性增加,竖向压力越大K_0增加的速率越慢,与增湿水平对K_0的影响规律相似;不同竖向压力下增湿过程中的竖向应变与静止土压力系数K_0试验点分布在一个较窄的范围内,可以采用同一双曲线描述,且不同压力作用与浸水作用的先后次序对曲线影响较小。基于上述新疆伊犁黄土试验规律,建立以增湿水平和竖向压力为自变量的K_0的表达式,以及以竖向应变为自变量的K_0的表达式。

At present,the coefficient of earth pressure at rest （K0） of collapsible loess is unable to reflect the influence of pressure and water content.In order to obtain the calculation method of K0 under coupling conditions of pressure and moisture,experimental research of variation rules of K0 during the wetting process for original loess was carried out.Firstly,a concept of wetting level was introduced to describe the moisture condition of soil.Secondly,stepped wetting tests were performed on loess under net vertical pressure to investigate the correlation between K0 and the wetting level,malric suction,as well as vertical strain.Lastly,the conclusion of stepped wetting tests was verified through centrifugal model tests for the loess collapsibility.The experimental results showed that： 1） the concept of wetting level,reflecting the initial condition of moisture content and the process of wetting of loess,had a specific physical meaning;2） K0 of original loess increased linearly with increasing wetting level.Addition- ally,the rate of increase of Ko depended on the vertical pressure;the greater vertical pressure the slower the rate of increase;3） during the wetting process under different but constant vertical pressure,K0 increased linearly with decreasing suction.However,the greater the vertical pressure the slower the rate of increase.The influence of matric suction on K0 was similar to that of wetting level;4） data on e（vertical strain） versus K0 during wetting processes under different vertical pressures were distributed in a narrow range,which could be described using a hyperbolic curve.There was a small difference between the e-K0 curves of different pressure and water action sequences.On the basis of stepped wetting tests,an empirical formula for K0 was established with the vertical pressure,wetting level and vertical strain as independent variables.