黄土结构性的单变量参数研究

发布时间：2018-06-07 21:14

本文选题：黄土 + 结构性　；参考：《西北农林科技大学》2014年博士论文

【摘要】：黄土是一种典型的结构性土，在我国有着广泛的分布，且多集中在烈度高地震多发的中西部地区。黄土的结构性直接影响其力学性质，是引起黄土地区环境灾害和工程问题的主要原因之一。本文总结了土结构性研究的基本途径和发展阶段，选择土力学研究方法研究土的结构性。通过分析土体结构在受力过程中的变化机理，分别构建静、动荷载条件下黄土结构性的单变量参数。该组单变量参数既继承了前人成果的合理内核，又拓展了结构性参数的应用空间，此外还具有简化计算过程，利于实现数值计算等优点。所获得的成果如下： 1．本文在深入分析前人提出的基于变形考虑的结构性定量化参数和基于强度考虑的结构性定量化参数的基础之上，提出了两者在形式上统一的表达式—即采用割线模量表示的土结构性参数。采用割线模量表示的土结构性参数的积极意义在于避免由于起始状态土的应力、应变都是零时基于应力考虑的和基于应变考虑的土结构性参数无初始解现象。 2．构建了以主动作用为单变量描述的土结构性单变量参数，分别为侧限压缩试验条件下的基于相同压力方法和基于相同变形方法的土结构性单变量参数，以及三轴试验条件下的基于相同主应力差方法和基于相同大主应变方法的土结构性单变量参数。所构建的结构性单变量参数具有的积极意义在于由于涉及的单变量是主动作用，所以该结构性参数可以直观地反映主动作用对土结构性的影响。 3．分别对侧限压缩试验条件下和三轴试验条件下的黄土结构性单变量参数进行检验。检验的结果表明所建议的黄土结构性单变量参数计算的结果能够和与原始公式计算结果较好地吻合，说明所建议的结构性单变量参数具有合理性。通过对不同地区黄土的原状样、重塑样和人工结构性样进行侧限压缩试验和三轴压缩试验，研究黄土结构性的变化规律。对相关影响因素展开分析，获取不同试验条件下结构性参数曲线的特征。同时，，试验结果还发现基于相同压力(主应力差)方法的黄土结构性参数和基于变形(大主应变)方法的黄土结构性参数除了主动作用起始点处相等外，其余的并不相等。因此，需在使用时注明是基于何种方法的黄土结构性参数。 4．分别构建了动荷载试验条件下黄土结构性单变量参数，即基于相同动剪应力方法和基于相同动剪应变方法的黄土动结构性单变量参数。对兰州、洛川、杨凌三个地区黄土进行了动扭剪三轴试验。在获得兰州、洛川、杨凌三个地区黄土动剪应力与动剪应变关系曲线的基础上，利用所构建的土动结构性的单变量参数对试验数据进行整理。检验了动荷载试验条件下黄土动结构性单变量参数的合理性，并且得到了兰州、洛川、杨凌这三个地区基于相同动剪应力方法的黄土动结构性单变量参数曲线和基于相同动剪应变方法的黄土动结构性单变量参数曲线，分析动力条件下黄土动结构性变化规律，及该特性在不同地区的差异。
[Abstract]:Loess is a typical structural soil, which is widely distributed in our country and concentrated in the central and western regions with high intensity and high earthquake. The structure of loess directly affects its mechanical properties, which is one of the main reasons causing environmental disasters and engineering problems in the loess region. This paper has always been the basic approach to the study of soil structure and the development order. The single variable parameters of loess structure under static and dynamic loading conditions are constructed by analyzing the change mechanism of soil structure in the stress process. The single variable parameters of this group not only inherit the reasonable kernel of the previous achievements, but also expand the application space of the structural parameters, in addition, it also has the application space of the structural parameters. The advantages of simplifying the calculation process and realizing numerical calculation are as follows.
1. in this paper, based on the in-depth analysis of the structural quantitative parameters based on deformation considerations and the structural quantitative parameters based on the strength consideration, this paper proposes a unified expression in the form of the soil structural parameters represented by the secant modulus. The extreme significance is to avoid the initial solution of soil structural parameters based on stress and strain considering the stress in the initial state.
2. the single variable parameters of soil structure based on the active action as a single variable are constructed, which are the single variable parameters based on the same pressure method and the same deformation method based on the lateral compression test, and the soil based on the same principal stress difference method and the same large principal strain method under the three axis test condition. Structural univariate parameters. The positive significance of the structural single variable parameters is that the structural parameters can directly reflect the effect of the active effect on the soil structure because the involved univariate is active.
3. the structural univariate parameters of loess under the condition of lateral compression test and three axis test are tested respectively. The results show that the calculated results of the proposed structural single variable parameters can be in good agreement with the original formula, indicating that the proposed structural parameters are reasonable. Through the lateral compression test and three axis compression test of the original samples, remolded samples and artificial structural samples in different regions, the changes in the structural changes of loess are studied. The related factors are analyzed to obtain the characteristics of the structural parameter curves under different test conditions. The structural parameters of the Loess and the structural parameters of the Loess Based on the deformation (large main strain) method are not equal except for the starting point of the active action. Therefore, the structural parameters of the Loess should be indicated in the use of the method.
4. the structural single variable parameters of loess under dynamic load test are constructed respectively, that is, based on the same dynamic shear stress method and the single variable parameter of loess dynamic structural based on the same dynamic shear strain method. Three loess areas in Lanzhou, Luochuan and Yangling are tested by the dynamic torsion shear three axis test. In the three regions of Lanzhou, Luochuan and Yangling, the Loess movement is obtained. On the basis of the relationship between the shear stress and the dynamic shear strain curve, the experimental data are sorted by the single variable parameters of the constructed soil dynamic structure. The rationality of the single variable parameters of the loess dynamic structure under the dynamic load test condition is tested and the Loess movement based on the same dynamic shear stress method in three regions of Lanzhou, Luochuan and Yang Lingzhe is obtained. The structural single variable parameter curve and the single variable parameter curve of loess dynamic structural based on the same dynamic shear strain method are used to analyze the changes of dynamic structural changes of loess under dynamic conditions, and the difference of this characteristic in different regions.
【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU444;TU43

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