短时冻土区花岗岩残积土边坡失稳机制研究

发布时间：2018-01-07 02:34

本文关键词：短时冻土区花岗岩残积土边坡失稳机制研究　出处：《福州大学》2013年硕士论文　论文类型：学位论文

【摘要】：福建省地处中国东南沿海,花岗岩分布广泛。境内短时冻土区(主要分布在南平市、三明市以及宁德市内),在花岗岩残积土边坡的运营过程中,经常在春融期间发生边坡失稳情况。基于此,本文基于南平武夷山地区的典型花岗岩残积土,采用传热学理论、渗流理论以及非饱和土力学等理论,通过室内试验对短时冻土区花岗岩残积土的工程特性进行研究,并采用数值模拟的方法,对武夷山地区典型边坡温度场和湿度场及边坡的失稳机制进行研究,主要结论如下：(1)南平武夷山地区的典型花岗岩残积土主要取了两类进行分析：Ⅰ号土为粒径级配不良的低液限砾质粘性土,其比重为2.425,最大干密度为1.79g/cm3,最优含水率为14.95%：Ⅱ号土为粒径级配不良的低液限砾质粘性土,其比重为2.316,最大干密度为1.84g/cm3,最优含水率为15.02%。(2)随着含水率的增大,土体的抗剪强度呈明显下降趋势,而对内摩擦角的影响比较小；抗剪强度随着压实度的升高均呈明显增大趋势；随着冻融循环次数的增多,土样的抗剪强度指标包括粘聚力和内摩擦角均呈下降趋势,但变化幅度越来越小,3次循环之后基本保持不变。(3)冻融作用下,地表浅层的含水量变化幅度最大,而10cm以下的含水量曲线平缓,总含水量和未冻水含量轻微下降或不变,武夷山地区冻结层厚度约为10cm。冻融状态下边坡土体温度和湿度随气温、初始含水率和导热系数变化较为明显,而随密实度和比热容变化较不明显。(4)短时冻土区在浅层冻土完全融化时,其物理参数包括重度,抗剪强度降低到一定值时,可能发生浅层失稳,且其稳定性随着冻融深度的增加呈显著下降趋势。随着边坡土体冻融循环次数的增加,稳定性不断降低,下降幅度越来越小,但由于武夷山地区边坡其冻融影响深度有限,故认为冻融循环对深层边坡的稳定性影响不大,但对浅层边坡的稳定性有较大的影响。(5)针对相关失稳机制,提出了改善土体温湿度环境、边坡条件和设置防护结构物的三类技术措施。
[Abstract]:Fujian province is located in the southeast coast of China, granite widely distributed. Short permafrost region (mainly in the territory of the city of Nanping, Sanming City and Ningde city), in the operation process of granite residual soil slope, often in the spring thaw during slope instability. Based on this, the typical granite residual soil in Nanping area of Wuyishan based on, using heat transfer theory, percolation theory and unsaturated soil mechanics theory, through the research of engineering characteristics of indoor tests of granite residual soil in permafrost area in short time, and by the method of numerical simulation, the slope of Wuyishan typical temperature field and humidity field and slope instability mechanism were studied. The main conclusions are as follows: (1) Nanping Wuyishan area of the typical granite residual soil mainly took two kinds of analysis: 1 soil particle size of poorly graded gravel cohesive soil with low liquid limit, the proportion is 2.425, the most Dry density is 1.79g/cm3, the optimal water content is 14.95%: II soil particle size of poorly graded gravel cohesive soil with low liquid limit, the proportion is 2.316, the maximum dry density is 1.84g/cm3, the optimum water content was 15.02%. (2) with the increase of moisture content, the shear strength of soil was significantly decreased, and the a relatively small effect on the internal friction angle; the shear strength increases with the degree of compaction showed a significantly increasing trend; with the increased freezing and thawing cycles, the shear strength of soils including cohesion and internal friction angle decreased, but the change rate is more and more small, 3 cycles after basically unchanged. (3) freezing and thawing, the shallow surface moisture variations, and water containing 10cm below the curve flat, total water content and unfrozen water content decreased slightly or unchanged, Wuyishan area of the frozen layer thickness of about 10cm. frozen thawing slope soil condition The temperature and humidity changes with the temperature, initial moisture content and thermal conductivity is more obvious, and with the density and specific heat capacity change is not obvious. (4) short permafrost zone in shallow permafrost to melt completely, the physical parameters including severe, shear strength is reduced to a certain value, may occur in shallow instability, and its stability with freeze-thaw depth decreased significantly. With the increase of slope increase of freeze-thaw cycles, the stability decreases, the decline is more and more small, but because of the influence of freeze-thaw slope in Wuyishan area with limited depth, so that the freeze-thaw cycle has little effect on the stability of the deep slope, but there are large influence on the stability of shallow slope. (5) aiming at the instability mechanism, put forward to improve the soil temperature and humidity environment, three kinds of technical measures of slope conditions and setting protective structures.

【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU43

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