青藏粉质黏土单向冻结冷生构造发育及冻胀发展过程试验研究

通过对青藏饱和粉质黏土进行开放条件下的单向冻结试验，并结合土样冻结过程的图像数据，分析土样在单向冻结过程中冷生构造的发育和冻胀变形的发展规律，得到以下结论：试样冻结稳定所需时间为26 h左右，基本不受顶板温度变化的影响，但土样冻结后形成不同冷生构造带的位置及薄厚与土样顶板温度（顶底板温度梯度）密切相关，顶板温度越低，微薄层状和薄层状构造带的厚度越大，最暖端厚层冰透镜体以及未冻土部分整体状构造带的厚度越小。研究结果还表明，土样的冻胀变形经历了快速冻胀、稳定冻胀和线性冻胀3个阶段，其中线性冻胀阶段是冻胀发展最快的阶段，也是冰透镜体生长最快的阶段。研究成果揭示了土样单向冻结过程中冷生构造发育和冻胀发展的动态过程，为冻胀机制的认识以及冻胀模型的建立与验证提供了试验基础。

Experimental study of development of cryostructure and frost heave of the Qinghai-Tibet silty clay under one-dimensional freezing

Based on one-dimensional freezing test at five different top cooling temperatures in an open system, the freezing behaviors of the saturated Qinghai-Tibet silty clay are studied experimentally. Combining with digital image acquisition technology and routine data measure system in laboratory, the temperature distribution and development, cryostructure profile development, frost heave development, water supplement process and water content profile are analyzed during one-dimensional freezing of soil sample. Some conclusions are drawn as follows. Firstly, the freezing front in sample reaches a stable state after 26 hours. After that, the longitudinal cryostructure of soil samples can be divided into four belts, including tiny thin layer structural belt, thin layer structural belt, thick layer structural belt and overall structure belt from the cold end to warm end. The frost heave development contains three stages, i. e. fast frost heave stage, stable frost heave stage and linear frost heave stage. The ice lens segregation at the bottom of thin layer structural belt and thick layer structural belt are the main source of frost heave. After tests, the water content profiles of the soil sample indicate that the water content increases in frozen part and decreases in unfrozen part. Meanwhile, the layers in which having the highest water content are located at the location of thick ice lenses. Because of the consolidation of the unfrozen part and water migration from unfrozen part to freezing front and frozen part, the water content of the unfrozen part has decreased and induced a drying phenomenon. The conclusions have provided the dynamic processes of the development of cryostructure and frost heave of the Qinghai-Tibet silty clay under one-dimensional freezing. It is expected that this study will provide a test basis for future study of more reasonable frost heave models.