南阳膨胀土的持水特性及边坡稳定性分析

发布时间：2018-03-01 13:37

本文关键词： 膨胀土胀缩特性水化时间持水特性室内试验　出处：《中原工学院》2017年硕士论文　论文类型：学位论文

【摘要】：膨胀土具有膨胀性、裂隙性和超固结性,这其中以膨胀性最为突出。原状膨胀土与重塑膨胀土的膨胀性能差别显著。研究认为工程开挖等过程对膨胀土的卸荷扰动是诱发膨胀土边坡工程灾害的一个促进因素。研究不同卸荷扰动状态膨胀土的膨胀特性对于优化膨胀土边坡工程施工与设计意义重大。“无水不滑坡”,持水特性对膨胀土的膨胀性及力学特性也有重要影响。目前该研究主要集中于干湿循环、初始含水率等因素对膨胀土膨胀性及强度参数等的影响,而对于水化时间这一重要变量的研究较少。膨胀土由于具有显著的吸水膨胀、失水收缩过程,导致其与一般粘性土土水特征曲线的吸湿与脱湿过程差异较大。故开展不同扰动状态与水化时间膨胀土的膨胀性和膨胀土全吸力过程吸湿-脱湿特性研究,可深化膨胀土膨胀特性和持水特性的认识,为膨胀土地区边坡工程设计提供参考。本文以膨胀土边坡开挖失稳破坏为背景,以南阳膨胀土为研究对象,采用室内试验、理论分析和数值计算的方法,结合非饱和土力学,重点研究了结构性对膨胀土土水特征曲线的影响和不同扰动状态与水化时间的膨胀土膨胀性演化规律;最后,通过ANSYS有限元软件,对膨胀土在不同水化时间作用下的膨胀特性对边坡稳定性的影响规律进行分析和探讨,为膨胀土地区边坡灾害防治提供理论依据。本文研究内容和研究成果如下:(1)考虑吸湿-脱湿的全吸力过程膨胀土持水特性研究选取原状膨胀土样与相同干密度重塑膨胀土样,在压力板仪对土样脱湿-吸湿全过程土水特征曲线研究;通过溶液法,对南阳膨胀土样进行土水特征曲线研究,并与压力板仪法所得曲线进行对比与修正;对比重塑与膨胀土吸湿-脱湿土水特征曲线,分析发现孔隙结构以及孔隙分布是影响土水特征曲线的主要原因;通过Van Genuchten模型、Fredlund-xing3参数模型、Fredlund-xing4参数模型以及Gardner模型对原状膨胀土与相同干密度重塑膨胀土土水特征曲线拟合,发现4个模型拟合效果较好。对比小吸力范围(吸力小于1200kPa)和全吸力范围(吸力小于286MPa)各模型拟合参数,发现其拟合参数有所不同。(2)不同水化时间下的膨胀土变形特性试验模拟边坡开挖,在经历了不同卸荷幅度(拟定40kPa、80kPa、160kPa、240kPa)后进行不同水化时间的重新固结过程,进而开展不同水化时间(拟定0d、1d、10d、60d)下膨胀土的变形特性试验,发现卸荷扰动幅度越大,膨胀土的膨胀率越高。膨胀土的膨胀率随着水化时间的增加而小幅升高,一般在10d左右完全稳定,大于规范要求的24h膨胀率。最后对其膨胀特性进行了解释。(3)膨胀土边坡稳定性研究通过ANSYS软件等对不同水化时间与卸荷幅度膨胀土边坡稳定性进行分析,发现水化时间与卸荷幅度对膨胀土稳定性均有一定影响。
[Abstract]:Expansive soil has expansibility, fissures and overconsolidation, The difference between the expansive properties of undisturbed expansive soil and remolded expansive soil is significant. It is considered that the unloading disturbance of expansive soil caused by engineering excavation is a promotion of engineering disasters induced by expansive soil slope. It is very important to study the expansive characteristics of expansive soil in different unloading disturbance states for optimizing the engineering construction and design of expansive soil slope. "No water without landslide", the water-holding property also has an important influence on the expansive and mechanical properties of expansive soil. At present, the research is mainly focused on the dry and wet cycle, The effect of the initial moisture content on the expansive properties and strength parameters of expansive soils is less studied, but the hydration time is an important variable. As a result, the moisture absorption and dehumidification process of the expansive soil is different from that of the general clay soil, so the swelling property of expansive soil under different disturbance states and hydration time and the hygroscopic and desiccant characteristics of expansive soil during the whole suction process are studied. It can deepen the understanding of swelling characteristics and water-holding characteristics of expansive soil, and provide reference for slope engineering design in expansive soil area. In this paper, taking expansive soil slope excavation instability failure as background and Nanyang expansive soil as research object, laboratory tests are adopted. The theoretical analysis and numerical calculation, combined with unsaturated soil mechanics, focus on the influence of structure on the characteristic curve of expansive soil and the evolution of expansive soil with different disturbance states and hydration time. By means of ANSYS finite element software, the influence of expansive characteristics of expansive soil on slope stability under different hydration time is analyzed and discussed. The research contents and results of this paper are as follows: 1) considering the moisture absorption and desiccation of the whole suction process, the water holding capacity of expansive soil is studied. The original expansive soil sample and the same dry density remolded expansive soil sample are selected. The soil-water characteristic curve of the whole process of desiccation-moisture absorption of soil sample is studied by pressure plate method, and the soil-water characteristic curve of Nanyang expansive soil sample is studied by solution method, and the curve obtained by pressure plate method is compared and corrected. Comparing the characteristic curves of remolded and expansive soil with moisture absorption and desiccant soil, it is found that the pore structure and pore distribution are the main factors influencing the soil-water characteristic curve. By means of Van Genuchten model and Fredlund-xing3 parameter model and Fredlund-xing4 parameter model and Gardner model, the water characteristic curves of undisturbed expansive soil and remolded expansive soil with the same dry density are fitted. It was found that the fitting effect of the four models was better. The fitting parameters were compared between the small suction range (suction < 1200 KPA) and the full suction range (suction < 286 MPA). It is found that the deformation characteristics of expansive soil under different hydration time are simulated by the test of deformation characteristics of expansive soil under different fitting parameters. After different unloading ranges (40 kPa80kPa160kPa240kPa), the reconsolidation process of different hydration time is carried out. Then the deformation characteristic tests of expansive soil under different hydration time (1 day or 10 d ~ 60 d) were carried out. It was found that the larger the unloading disturbance amplitude, the higher the expansion rate of expansive soil, and the smaller the swelling rate of expansive soil increased with the increase of hydration time. Generally, it is completely stable in about 10 days. The stability of expansive soil slope is analyzed by ANSYS software, which is used to analyze the stability of expansive soil slope with different hydration time and unloading amplitude. It is found that hydration time and unloading range have certain influence on the stability of expansive soil.
【学位授予单位】：中原工学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU443

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