膨胀土增湿过程中膨胀规律的试验研究

摘要

为了研究膨胀土增湿过程中膨胀规律,取某高速铁路地基膨胀泥岩土样,研究其无荷膨胀率随含水率增大过程中的变化规律.试验结果表明:膨胀土无荷膨胀率随含水率变化过程分为3个阶段,分别为快速膨胀阶段、缓慢膨胀阶段和趋于稳定阶段,得到3个变化节点含水率.然后使用蒙脱石含量、阳离子交换量、自由膨胀率、液限这4个指标作为模型因子,利用主成分分析法得到能够表征膨胀土膨胀能力强弱的膨胀特性Z值.分析3个变化节点含水率与膨胀特性Z值的关系,得到3个含水率与Z值的函数关系式.在实际工程中,可以测定土样的当前含水率和4个指标值,由4个指标值得到膨胀特性Z值,由变化节点含水率与Z值的函数关系计算得到3个变化节点含水率,然后判断土体当前含水率与3个变化节点含水率的关系,就能判断土体在当前含水率下膨胀能力的强弱,这可对实际工程提供一定参考.%In mudstone order to study the swelling law of the expansive soil during humidification process, taking the expansive mudstone soil sample from a high-speed railway foundation as an specimen, studies of the change law of non-loading expansion rate with the increase of moisture content are carried out in this paper. The experimental results indicate that the change process of the non-loading expansion rate of the expansive soil with the changes in moisture content can be divided into three stages: the rapid expansion stage, the slow expansion stage and the tend-to-be-stable stage. This study obtains the values of the moisture content in three change nodes, then utilizes the four indexes, that is, montmorillonite content, cation exchange content, free expansion rate and liquid limit, as the model factors, and further uses the main ingredient analytic method to get the Z value of the expansion characteristic, which can represent the expansion capacity of the expansive soil. This study also analyzes the correlation characteristic, which can represent the expansion capacity of the expansive soil. This study also analyzes the correlation between the moisture content of three change nodes and the Z value of the expansion characteristic, and gets the function relationships between them. In practical works, the current moisture content of the soil sample and its four indexes can be measured, then the Z value of the expansion characteristic can be obtained from the four indexes. Furthermore, the moisture content of three change nodes can be calculated through the function relationships between the moisture content of the change nodes and Z value, and finally we can assess the relationships between the current soil moisture content and the moisture content of three change nodes and judge the strength of the soil mass under the current moisture content, and provide some reference for the practical works.