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主要是对冻土的三轴蠕变特性进行分析研究,从而进一步确定具有明显流变特性的平面冻土墙的厚度。通过对冻土的流变特性进行理论分析,建立了冻黏土在复杂应力状态下的对数型蠕变方程。采用“低温箱-三轴压力室”轻型试验设备系统对人工配制的冻黏土试件进行了三轴蠕变试验,获得了冻黏土在复杂应力状态下的蠕变曲线。根据试验结果,对冻黏土的对数型非线性蠕变方程进行回归分析,得到了冻黏土对数型蠕变方程参数的数值。根据冻土流变理论和所建立的蠕变方程,以及平面冻土墙的厚度计算公式,利用Visualc++6.0和Matlab 6.0技术开发了冻土墙厚度计算的计算机应用软件。分析研究了平面冻土墙厚度与跨度、基坑暴露时间、基坑开挖深度的关系。平面冻土墙厚度随时间的延长在短期内具有急速增长的趋势,而后随时间的延长逐渐趋于稳定;平面冻土墙厚度受其跨度的影响较小,但随基坑开挖深度的加深具有逐步增长的趋势;温度对平面冻土墙厚度的影响显著,温度越高,厚度越大,所以,控制温度是平面冻土墙设计中的关键。从而为蠕变变形较大的平面冻土墙的厚度确定提供了依据。
Mainly on the triaxial creep characteristics of frozen soil analysis, in order to further determine the apparent rheological properties of the surface of the thickness of frozen soil wall. Through the theoretical analysis of the rheological characteristics of frozen soil, the logarithmic creep equation of frozen clay under complex stress conditions is established. The triaxial creep test of the frozen clay samples was carried out by using “Cryogenic Box - Triaxial Pressure Chamber” light test equipment system, and the creep curves of the frozen clay under complex stress conditions were obtained. According to the experimental results, the logarithmic nonlinear creep equation of frozen clay is regressed and the numerical value of logarithmic creep equation parameter of frozen clay is obtained. According to the rheological theory of permafrost and the established creep equation, and the calculation formula of the thickness of the plane frozen soil wall, the computer application software of the calculation of the thickness of the frozen soil wall was developed by using Visual C ++ 6.0 and Matlab 6.0 technology. The relationship between the thickness and the span of the plane frozen soil wall, the exposure time of the foundation pit and the excavation depth of the foundation pit is analyzed and studied. The thickness of the flat frozen earth wall increases rapidly with time in a short period of time and then tends to be stable with the extension of time. The thickness of the flat frozen earth wall is less affected by its span, but with the deepening of the excavation depth With the trend of gradual increase; temperature has a significant impact on the thickness of the flat frozen soil wall, the higher the temperature, the greater the thickness, so the control temperature is the key in the design of flat frozen soil wall. Which provides a basis for the determination of the thickness of the flat frozen soil wall with large creep deformation.