原状黄土节理面剪切强度及其本构关系研究

发布时间：2018-06-16 05:11

本文选题：黄土节理 + 剪切强度　；参考：《西安建筑科技大学》2017年硕士论文

【摘要】：黄土节理的剪切强度特性对于含节理黄土工程的稳定性有重要影响,而节理剪切强度特性与节理表面形态密切相关。为此,需对节理表面形态进行了研究。首先,在大量野外调研的基础上,选取合适场地采集了天然黄土节理试样,利用轮廓曲线仪测量节理表面形态,并绘制了节理面轮廓曲线。运用统计学方法计算了节理表面特征参数,然后选取高度均方根z1、峰点密度η、坡度均方根z2三个参数,根据数据统计结果及经验确定单因素分级范围,利用模糊数学方法综合评价节理表面形态,最终得到了所取天然黄土节理试样表面形态的综合特征参数RJ及分级结果。依据节理表面形态分级标准制备试样,采用室内小型直剪试验方法研究了含水量对黄土节理剪切强度参数的影响规律,并对比室内大型直剪试验与小型直剪试验结果,研究了尺寸效应对剪切强度的影响,根据所有试验结果研究了节理剪切应力-位移关系曲线特征。节理表面形态研究发现：不同场地间天然黄土土样的节理表面形态存在差异,同一场地,节理表面形态相近;各节理面的峰态系数K值的范围为2~3,均值接近3,表明节理面的全坐标高度分布为高斯分布或准高斯分布;验证发现RJ与节理剪切强度具有较好的线性相关性,说明本次对节理面分级的方法具有可行性。直剪试验结果表明：黄土节理的抗剪强度关系符合摩尔-库伦准则,且粘聚力很小,可以忽略不计;随含水量的增加,黄土节理峰值内摩擦角最初的变化幅度较小,当大于某个含水量值时,峰值内摩擦角减小幅度变大,黄土节理强度随含水量的变化规律可用指数形式进行描述,并提出了节理剪切强度的经验计算公式,验证了公式的合理性;黄土节理直剪试验存在尺寸效应,试样尺寸主要影响节理面起伏度对剪切强度的贡献,尺寸越大,其剪切强度也越大;黄土节理剪切应力-位移的关系曲线属于无峰值的应变硬化型曲线,并提出了合理的本构模型;利用提出的本构模型拟合试验结果,得到了节理初始剪切刚度,发现其随含水量增加减小,随正应力增加呈线性增加。
[Abstract]:The shear strength characteristics of loess joints have an important effect on the stability of loess engineering with joints, and the shear strength characteristics of joints are closely related to the surface morphology of joints. Therefore, it is necessary to study the surface morphology of joints. Firstly, on the basis of a large number of field investigations, natural loess joint samples were collected in a suitable site, the joint surface morphology was measured by profilometer, and the contour curve of joint surface was drawn. The surface characteristic parameters of joints were calculated by statistical method, and then three parameters of high RMS root z1, peak density 畏, slope RMS root z2 were selected, and the single factor classification range was determined according to the statistical results and experience. The surface morphology of joints was evaluated by fuzzy mathematics method, and the synthetic characteristic parameters RJ and classification results of the surface morphology of natural loess joints were obtained. The effect of water content on the shear strength parameters of loess joints was studied by means of laboratory direct shear test, and the results of large-scale direct shear test and small direct shear test were compared. The influence of size effect on shear strength is studied. According to all the experimental results, the characteristics of shear stress-displacement curves of joints are studied. It is found that the joint surface morphology of natural loess soil samples is different between different sites, and the joint surface morphology is similar at the same site. The range of peak coefficient K of each joint plane is 2 ~ 3, the mean value is close to 3, indicating that the whole coordinate height distribution of joint surface is Gao Si distribution or quasi-Gao Si distribution, and it is found that RJ has a good linear correlation with joint shear strength. It shows that the method of joint surface classification is feasible. The results of direct shear test show that the shear strength relationship of loess joints accords with the Moor-Coulomb criterion, and the cohesion is very small, which can be ignored, and the initial variation of the peak internal friction angle of loess joints is small with the increase of water content. When the value of water content is greater than a certain value of water content, the amplitude of peak internal friction angle decreases and the variation of loess joint strength with water content can be described exponentially, and the empirical formula for calculating joint shear strength is put forward. The rationality of the formula is verified: the size effect exists in the direct shear test of loess joints, the size of the specimen mainly affects the contribution of the undulation of the joint surface to the shear strength, and the larger the size, the greater the shear strength; The relationship curve between shear stress and displacement of loess joints is a strain hardening curve without peak value, and a reasonable constitutive model is proposed, and the initial shear stiffness of joints is obtained by fitting the test results with the proposed constitutive model. It is found that it decreases with the increase of water content and increases linearly with the increase of normal stress.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444

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