利用原位浸水试验计算非饱和黄土基质吸力方法研究

Calculation Method of Unsaturated Loess Matrix Suction by In-situ Soaking Test

精确计算非饱和土渗透系数时需要考虑土体的负孔隙水压力水头值,即基质吸力。然而基质吸力的准确测定有一定难度,通常室内试验与现场测定的结果相差较大,影响实际工程应用。提出一种全新的算法,即利用原位浸水试验数据对土体基质吸力进行计算,利用Green-Ampt入渗模型结合浸水坑水面下降速率和水分传感器测定的浸水渗透速率之间的差值计算出地层负孔隙压力水头值。选取黄土–古土壤互层场地开展原位浸水试验,根据试验数据计算出第一层厚度为4 m的黄土的负孔隙压力水头值为233 cm,第二层为厚度2 m的古土壤层的负孔隙压力水头值为124 cm;应用该算法预测出在浸水坑以下8.4m处地层基质吸力消减为零。本研究是对黄土地层基质吸力计算的一种新尝试。

When the permeability coefficient of unsaturated soil is calculated by a relatively accurate algorithm considering the suction head value of the soil matrix in the project,it is difficult to accurately measure the suction head value of the matrix,and the measurement results of the laboratory test are quite different from the head value measured in the field.A new algorithm was used to calculate the soil matrix suction by using the in-situ water immersion test data.It is different from various traditional testing methods such as the indoor tensiometer method.Instead,it uses the Green-Ampt infiltration model combined with the immersion pit.The suction head value of the formation matrix is calculated from the difference between the water surface falling rate and the water infiltration rate measured by the moisture sensor.Select a loess paleosol interlayer site for in-situ immersion testing.The suction head value of the first layer of loess matrix with a thickness of 4 meters is 233 cm,and the value of the second layer of paleosol with a thickness of 2 meters is 124 cm.Using this algorithm,the suction head value of each layer of soil matrix can be predicted and calculated,and finally it is predicted that the suction of the stratum matrix will decrease to zero at 8.4 m below the immersion pit.This is a new attempt to calculate the suction of soil matrix in loess strata.