粉质黏土负温抗剪强度试验研究

发布时间：2018-03-19 10:27

本文选题：冻结粉质黏土　切入点：三轴试验　出处：《哈尔滨理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：作为世界第三冻土分布大国,我国境内冻土分布广泛。“一带一路”战略和京津冀、“东北-蒙东经济区”战略的提出,几乎将我国冻土分布区域全部纳入其中。在经济飞速发展的前提下,国家必将对道路等交通基础设施建设投入大量人力物力;同时,公路运输呈现的多轮轴、重载化趋势也将增加道路的灾害风险。冻土作为一种复杂地质体,无疑会对道路安全运营产生严重威胁。本文以我国寒区冻土路基抗剪强度特性为应用背景,选取粉质黏土为研究对象,基于低温静三轴试验和理论分析等方法,研究粉质黏土的负温抗剪强度特性,并构建考虑温度、试样初始含水率的抗剪强度模型。主要研究工作如下:1.分析了冻土三轴试验中出现的温度控制困难、加载杆易冻结及围压补给受阻等问题的原因,给出了液体降温、干燥剂吸水、羽绒罩保温以及更换围压管路系统等措施,确保了试验的顺利开展。参考实际工况选取试样固结围压,改进了以往试验中冻结方式存在的不足,使试验条件与工程实际更加符合,从而确保结果的可靠性,并缩短了试验周期。2.不同温度及初始含水率条件下冻结粉质黏土负温三轴试验结果表明:在50kPa围压下,偏应力-轴向应变关系呈应变软化型,且随温度降低软化程度减弱。除个别试验点,温度及含水率对试样轴向破坏应变的影响存在临界值,在临界值以下,破坏应变随温度降低及含水率的升高而增大;在临界值以上,结果相反。同一含水率试样,其初始切线模量随温度降低而增大,但增长趋势逐渐变缓。温度降低时破坏强度近似线性增长,但破坏强度随含水率变化存在临界值。3.通过对试验数据的回归,建立了抗剪强度与温度之间的线性回归模型;通过将模型系数与含水率之间建立关系,得到了综合考虑温度及含水率的抗剪强度模型。误差分析显示,利用模型计算结果描述不同温度及初始含水率状态下冻结粉质黏土的抗剪强度较可靠。本文研究成果将对实际工程及相关研究提供一定的借鉴。
[Abstract]:As the third largest country in the world, permafrost is widely distributed in China. The strategy of "Belt and Road", "Beijing-Tianjin-Hebei" and "Northeast Mongolia Economic Zone" is put forward. In the premise of rapid economic development, the state will certainly invest a great deal of manpower and material resources in the construction of transportation infrastructure such as roads. At the same time, the road transportation presents multi-wheeled axles. The trend of heavy loading will also increase the disaster risk of roads. As a complex geological body, frozen soil will undoubtedly pose a serious threat to road safety operation. In this paper, the shear strength characteristics of permafrost roadbed in cold regions of China are taken as the application background. Based on low-temperature static triaxial test and theoretical analysis, the negative temperature shear strength of silty clay is studied, and the temperature is considered. Shear strength model of initial moisture content of sample. The main research work is as follows: 1. The causes of the problems such as difficult temperature control, easy freezing of loading rod and block of confining pressure recharge are analyzed in triaxial test of frozen soil, and the cooling of liquid is given. The measures of desiccant water absorption, down cover insulation and replacement of confining pressure piping system ensure the smooth development of the test. According to the actual working conditions, the sample consolidation confining pressure is selected, and the shortcomings of the freezing method in the previous tests are improved. The test conditions are more consistent with the engineering practice, so as to ensure the reliability of the results, and shorten the test period. 2. The negative temperature triaxial test results of frozen silty clay at different temperatures and initial moisture content show that: under the confining pressure of 50 KPA, The relationship between strain and axial strain is of strain softening type, and the softening degree decreases with the decrease of temperature. Except for a few test points, there is a critical value for the influence of temperature and moisture content on the axial failure strain of the specimen, which is below the critical value. The failure strain increases with the decrease of temperature and the increase of moisture content, but above the critical value, the results are opposite. The initial tangent modulus of the same moisture content sample increases with the decrease of temperature. However, the increasing trend is gradually decreasing. When the temperature decreases, the failure strength increases approximately linearly, but the critical value of the failure strength varies with the moisture content. A linear regression model between shear strength and temperature is established by regression of the test data. By establishing the relationship between the model coefficient and moisture content, the shear strength model considering temperature and moisture content is obtained. The error analysis shows that, It is more reliable to describe the shear strength of frozen silty clay under different temperature and initial moisture content by using the results of model calculation. The research results in this paper will provide some reference for practical engineering and related research.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD713

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