人工冻结粉质黏土力学性能演化规律研究

基于地铁工程中人工地层冻结法应用的工程背景,以粉质黏土地层为研究对象,通过室内试验研究冷冻温度、含水量和围压等因素对人工冻结粉质黏土强度和冻胀变形演化规律的影响。结果表明:冷冻温度、含水量和围压显著影响人工冻结粉质黏土的应力应变发展趋势和破坏模式,三轴剪切强度、弹性模量与冷冻温度、含水量和围压的相关性因三者的耦合作用而呈现不同的演化趋势;单向冻结模式下,温度场达到恒定温度梯度后,人工冻结粉质黏土达到了最大冻胀变形量;冻胀率与冷冻温度之间存在较好的线性回归关系,且外界水源补给条件下粉质黏土冻胀率远大于封闭不补水条件;冷冻温度、含水量和地层埋深是确保人工地层冻结技术中冻结壁达到设计强度、控制地表变形以及防止结构物破裂、渗水或漏泥等问题的3个关键指标。

Evolution Laws of Mechanical Properties of Artificially Frozen Silty Clay

Motivated by the application and development of artificial freezing method in subway engineering,with the silty clay layer as the research object,the evolution laws for the strength and frost heave deformation of artificially frozen silty clay affected by such factors as freezing temperature,moisture content and confining pressure were deeply studied through laboratory tests.Results indicate that the freezing temperature,moisture content,and confining pressure significantly affect the growing trend and failure mode of stress-strain curves.The relevance of the triaxial shear strength and elastic modulus with the freezing temperature,moisture content and confining pressure presents different evolution trends due to the coupling effects of the three.Under unidirectional freezing mode,the frost heave deformation of artificially frozen silty clay reaches the maximum once the temperature field reaches a constant temperature gradient.There is a better linear regression relationship between frost heave ratio and freezing temperature.Moreover,the frost heave ratio of silty clay under the condition of external water supply is much greater than that under the closed condition without water supply.In the engineering practice of artificial ground freezing technology,freezing temperature,moisture content and the buried depth of strata are the three indicators for ensuring the design strength of freezing wall,controlling surface deformation and preventing structure from fracture,water seepage or mud leakage.