黄土非饱和湿陷变形特性的研究

The current collapse settlement calculation is based on the precondition that the collapsible loess is fully saturated. A large number of field observations and in-situ tests indicate that the infiltration depth of surface water in loess is limited and there is a great difference between the measured collapse deformation and the calculation value for most tests. The collapse settlement of loess includes saturated collapse settlement and unsaturated collapse settlement. The project here combines unsaturated seepage and unsaturated deformation theory, establishes calculation method of unsaturated collapse settlement of loess, and then validates this method by comparing with the field submerging test. Firstly, digging an exploratory well to take undisturbed samples to get the basic physical and mechanics parameters, and get the soil-water characteristic curve, and educe the permeability curve, and then perform oedometer tests on the samples with different saturation degrees. By means of the field submerging test, the variation with time of moisture field and the tiered collapse settlement in different depth in the exploratory well will be monitored, and the total collapse settlement on surface of loess will be gotten. Then this project will simulate the water field using the unsaturated seepage equation, determine the site tiered collapse settlement and total collapse settlement using the calculation method for unsaturated collapse settlement. And the calculation result is compared with the measured one to verify this method. Evaluation method of loess collapse in this project takes the characteristics of unsaturated loess into account, which is consistent with the essential characteristics of loess. Study on this project is expected to improve the existing evaluation methods of loess collapse in the current Code.

现行黄土地基的湿陷量计算是以湿陷土层全部饱和为前提的，但是大量浸水试验都表明地表水在黄土中的入渗深度有限，导致大多数湿陷量实测值和计算值差异大，黄土湿陷包括饱和湿陷和非饱和湿陷两部分。本项目拟将非饱和渗流和非饱和变形理论相结合，建立黄土非饱和湿陷量计算方法，并通过现场浸水试验进行验证。首先开挖探井取原状样测试其基本物理力学参数及土-水特征曲线，确定渗透性曲线，并进行不同含水率土体固结试验。通过地表浸水，在探井内监测不同深度水分、分层湿陷量随时间的变化，在地表监测总湿陷量。利用非饱和渗流方程模拟水分场，用非饱和湿陷量计算方法确定场地分层湿陷量和总湿陷量，并和探井实测结果进行对比，对所提出的方法进行检验。本项目的湿陷性评价方法，考虑了黄土的非饱和特性，这符合黄土的本质特性，期望能改进现有规范中的评价方法。

现行黄土地基的湿陷量计算是以湿陷土层全部饱和为前提的，但是大量浸水试验都表明地表水在黄土中的入渗深度有限，导致大多数湿陷量实测值和计算值差异大，黄土湿陷包括饱和湿陷和非饱和湿陷两部分。本项目将非饱和渗流和非饱和变形理论相结合，建立黄土非饱和湿陷量计算方法，并通过现场浸水试验进行验证。首先开挖探井取原状样测试其基本物理力学参数及土-水特征曲线，确定渗透性曲线，并进行不同含水率土体固结试验。通过地表浸水，在探井内监测不同深度水分、分层湿陷量随时间的变化，在地表监测总湿陷量。利用非饱和渗流方程模拟水分场，用非饱和湿陷量计算方法确定场地分层湿陷量和总湿陷量，并和探井实测结果进行对比，对所提出的方法进行检验。本项目的湿陷性评价方法，考虑了黄土的非饱和特性，这符合黄土的本质特性，改进了现有规范中的评价方法。