重复荷载作用下非饱和黄土的动力特性试验研究

发布时间：2018-10-07 18:39

【摘要】：我国黄土的分布具有特别明显的气候性和地域性，其分布地区主要位于中西部。由于该地区处于地震活动频繁区，在地震及大变形振动条件下，常会使该区建筑物、构筑物的黄土地基与边坡产生严重震陷、滑坡等地质灾害。本文以神河高速公路边坡黄土为研究对象，采用动三轴试验，研究非饱和黄土（原状黄土和重塑黄土）受到重复荷载作用时，在不同固结围压、不同固结应力比、不同含水率条件下的动力学特性，由此探讨非饱和黄土的动本构关系、动弹性模量、动阻尼比和动强度的变化规律。本文所取得的主要成果总结如下：（1）神河高速非饱和黄土在重复荷载作用下动应力-动应变关系曲线基本表现为双曲线型，其中原状黄土对双曲线模型的拟合度高于重塑黄土；分别采用逐级加载和单级加载的方法，黄土动应力-动应变曲线表现出一定的差异；黄土动应力-动应变曲线受土体固结作用影响较为明显，，在相同的动应变条件下，动应力大小随固结围压和固结应力比值的增减同步增减；非饱和重塑黄土含水率在11%～19%范围内时，含水率对动应力-动应变曲线的形态几乎没有影响；（2）神河高速非饱和黄土的动弹性模量随动应变的增大而减小，两者之间的相关关系表现为随着动应变增大到一定程度后，黄土动弹性模量减小幅度减弱。黄土动弹性模量随初始固结围压、固结应力比值的增减同步增减；重塑黄土动弹性模量随含水率的增大而减小；（3）神河高速边坡非饱和原状黄土的动阻尼比约为0.10～0.25，重塑黄土约为0.05~0.20，重塑黄土动阻尼比略小于原状黄土，其原因在于黄土原位结构特性对其强度具有有利影响。通过对动三轴试验的结果分析得出，非饱和黄土的含水率、固结围压、固结应力比直接影响着黄土的动阻尼比大小。黄土动阻尼比随固结围压的增减同步增减；随固结应力比的增大而减小；重塑黄土动阻尼比随含水率大小的增减同步增减。原状土的动阻尼比-动应力曲线关系较重塑土的曲线关系更具规律性；（4）黄土的性质、黄土所处的应力状态环境、黄土所受的振动应力直接影响着非饱和黄土的动强度。动强度试验结果显示：非饱和黄土动强度随振动次数和固结应力比的增大而减小，随初始固结围压的增减同步增减；影响非饱和黄土抵抗破坏变形的最直接因素是固结围压大小，但当固结比增大到一定程度后，非饱和黄土动强度的直接影响因素（固结围压）的影响作用在不断减弱；（5）受非饱和黄土原位结构特性的影响，原状土所能承受的极限动载荷相比于重塑土略大；采用逐级加载的方法测定原状黄土的动强度，得出的结果高于单级加载测定的动强度值，该结果参数用于实际工程地基、边坡的设计中偏于不安全；非饱和黄土动强度各个指标的定量参数均随振次的增大呈现出减小的趋势。
[Abstract]:The distribution of loess in China is particularly climatic and regional, and its distribution is mainly located in the central and western regions. Because this area is in the area of frequent seismic activity, under the condition of earthquake and large deformation vibration, the loess foundation and slope of the buildings and structures in this area often produce serious earthquake subsidence, landslide and other geological disasters. Taking the loess slope of Shenhe Expressway as the research object, the dynamic triaxial test is used to study the different consolidation confining pressure and the different consolidation stress ratio of unsaturated loess (undisturbed loess and remolded loess) under repeated loading. The dynamic properties of unsaturated loess under different moisture content are discussed. The dynamic constitutive relation, dynamic elastic modulus, dynamic damping ratio and dynamic strength of unsaturated loess are discussed. The main results obtained in this paper are summarized as follows: (1) the dynamic stress-strain relationship curve of Shenhe high speed unsaturated loess under repeated loads is basically hyperbolic. The fitting degree of original loess to hyperbolic model is higher than that of remolded loess. The dynamic stress-strain curve of loess is obviously affected by soil consolidation. Under the same dynamic strain condition, the dynamic stress increases or decreases with the increase or decrease of consolidation confining pressure and consolidation stress ratio. When the moisture content of unsaturated remolded loess is in the range of 11% or 19%, the water content has little effect on the shape of dynamic stress-strain curve, (2) the dynamic elastic modulus of Shenhe high speed unsaturated loess decreases with the increase of dynamic strain. The correlation between the two shows that the dynamic elastic modulus of loess decreases when the dynamic strain increases to a certain extent. The dynamic elastic modulus of loess increases and decreases synchronously with the initial consolidation confining pressure, while the dynamic elastic modulus of remolded loess decreases with the increase of water content. (3) the dynamic damping ratio of unsaturated undisturbed loess is about 0.10 ~ 0.25, that of remolded loess is about 0.05 ~ 0.20. The dynamic damping ratio of remolded loess is slightly smaller than that of undisturbed loess. The reason is that the in-situ structural characteristics of loess have favorable influence on its strength. By analyzing the results of dynamic triaxial tests, it is concluded that the moisture content, consolidation confining pressure and consolidation stress ratio of unsaturated loess directly affect the dynamic damping ratio of loess. The dynamic damping ratio of loess increases and decreases with the increase of consolidation confining pressure, decreases with the increase of consolidation stress ratio, and increases and decreases with the increase of moisture content of remolded loess. The relationship between dynamic damping ratio and dynamic stress curve of undisturbed soil is more regular than that of remolded soil. (4) the nature of loess, the stress state environment of loess, The vibration stress of loess directly affects the dynamic strength of unsaturated loess. The dynamic strength test results show that the dynamic strength of unsaturated loess decreases with the increase of vibration frequency and consolidation stress ratio, and increases and decreases with the increase or decrease of initial consolidation confining pressure. The most direct factor affecting the failure and deformation of unsaturated loess is the consolidation confining pressure, but when the consolidation ratio increases to a certain extent, the influence of the direct influence factor (consolidation confining pressure) on the dynamic strength of unsaturated loess is weakening. (5) under the influence of the in-situ structural characteristics of unsaturated loess, the ultimate dynamic load of undisturbed soil is slightly larger than that of remolded soil, and the dynamic strength of undisturbed loess is measured by stepwise loading method. The results obtained are higher than the dynamic strength values measured by single stage loading. The parameters of the results are used in the actual engineering foundation and the slope design is not safe. The quantitative parameters of each index of dynamic strength of unsaturated loess decrease with the increase of vibration frequency.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411;TU444

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