基于干湿循环的膨胀土工程特性试验研究

发布时间：2018-03-03 22:37

本文选题：膨胀土　切入点：干湿循环　出处：《西北农林科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：论文以膨胀土为研究对象,以膨胀土的干湿循环效应为研究目的,通过室内膨胀土单轴抗拉试验、直接剪切试验、无荷膨胀率试验,较为全面地揭示了膨胀土经过干湿循环后土体强度和变形的变化规律,并分析了其产生干湿循环效应的机制和造成试验结果的原理,主要研究结论如下:1.通过膨胀土的无荷膨胀率试验,研究了膨胀土在干湿循环条件下其胀缩变形的变化规律,并建立膨胀土胀缩率与初始含水率、干密度和脱湿温度的关系。得出在单变量条件下,膨胀土的胀缩指标随初始含水率的增加而减小,随干密度的增加而增大,随脱湿温度的增大而增大。随干湿循环次数的增多,试样的相对膨胀率逐渐减小,绝对膨胀率则而增大,最终趋于一稳定值。并得出膨胀土的干缩湿胀变形(相对膨胀率)并不完全可逆。2.对膨胀土在反复干湿循环作用下的渗透特性进行了室内试验研究。对不同干湿循环次数的试样进行变水头渗透试验。膨胀土的下渗强度均随着干湿循环次数的增加而增加。渗透系数随干湿循环次数的增加而增加,随干湿循环幅度的增大而增加,随脱湿温度的减小而增加。3.通过室内单轴抗拉,研究膨胀土在干湿循环条件下强度的变化规律,在此基础上探讨了干湿循环条件下膨胀土强度与初始含水率、干密度、干湿循环次数、循环幅度、脱湿温度的关系。4.通过室内直剪试验,研究干湿循环条件下膨胀土强度与初始含水率、干密度、干湿循环次数、循环幅度、脱湿温度的关系。并建立抗剪强度与不同试验参数的强度衰减公式。由试验结果可知,膨胀土的干湿循环强度衰减主要发生在1~3次循环,且强度稳定的次数随循环幅度的增大而减小,在相同初始含水率、干密度下建立了膨胀土强度参数与干湿循环次数、干湿循环幅度、脱湿温度的表达式。
[Abstract]:This paper takes expansive soil as the research object, takes the dry-wet cycle effect of expansive soil as the research purpose, through indoor expansive soil uniaxial tensile test, direct shear test, no load expansion test. The variation law of strength and deformation of expansive soil after dry-wet circulation is revealed, and the mechanism of producing dry-wet cycle effect and the principle of test result are analyzed. The main conclusions are as follows: 1. Through the load free expansion test of expansive soil, the variation law of swelling and shrinkage deformation of expansive soil under dry and wet cycling conditions is studied, and the expansion and shrinkage ratio and initial moisture content of expansive soil are established. The relation between dry density and desiccant temperature. It is concluded that under the condition of single variable, the swelling and shrinkage index of expansive soil decreases with the increase of initial moisture content, increases with the increase of dry density, increases with the increase of desiccant temperature, and increases with the increase of dry-wet cycle times. The relative expansion rate of the sample decreases gradually, while the absolute expansion rate increases. Finally, a stable value is obtained, and it is concluded that the swelling deformation (relative expansion ratio) of expansive soil is not completely reversible. 2. The permeability characteristics of expansive soil under repeated dry-wet cycle are studied in laboratory. The infiltration strength of expansive soil increased with the increase of dry-wet cycle times, and the permeability coefficient increased with the increase of dry-wet cycle times. With the increase of dry-wet cycle amplitude and the decrease of desiccant temperature, the strength of expansive soil under dry-wet cycle is studied. On this basis, the relationship between the strength of expansive soil and initial moisture content, dry density, dry and wet cycle times, cycle amplitude and desiccant temperature under dry and wet cycling conditions is discussed. The relationship between strength and initial moisture content, dry density, dry-wet cycle number, cycle amplitude and desiccant temperature of expansive soil under dry and wet cycling conditions was studied. The formula of shear strength and strength attenuation of different test parameters was established. The attenuation of dry-wet cycle strength of expansive soil mainly occurs in 1 ~ 3 cycles, and the number of stable strength decreases with the increase of cyclic amplitude. Under the same initial moisture content and dry density, the strength parameters and dry-wet cycle times of expansive soil are established. The range of dry and wet circulation and the expression of dehumidification temperature.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU443

【参考文献】