膨胀土深基坑边坡侧向压力研究

发布时间：2018-05-19 00:00

本文选题：膨胀应力 + 侧向压力　；参考：《西南交通大学》2015年硕士论文

【摘要】：膨胀土主要是由强亲水性粘土矿物成分(如蒙脱石、伊利石和高岭石等)组成的,具有特殊的膨胀结构,以及强烈的胀缩特性、多裂隙性和强度衰减性的高塑性粘性土。通过对成都地区膨胀土基坑调研发现,膨胀土基坑边坡在降雨后,由于降雨和管道渗水等作用,基坑会出现变形或大裂缝。膨胀力是造成基坑失稳的主要原因,然而现有的膨胀土相关规范中,没有对其分布作出明确规定,无法在支护设计计算中考虑膨胀力的作用效果,导致基坑支护设计无法满足工程需求。通过对膨胀土基坑边坡侧向压力的研究,旨在探讨膨胀力对侧向压力的影响,为支护结构设计计算提供依据。主要研究内容和结论如下：(1)结合膨胀土及膨胀应力的相关文献,利用非饱和土力学及热力学相关知识,研究了膨胀应力计算问题,推导了膨胀应力计算公式△Pπ=κlnω0/ω1。结合土中含水量随深度变化曲线,分析半无限空间中膨胀应力随深度分布情况。(2)对膨胀土基坑边坡进行分区,结合湿度场理论,讨论膨胀土基坑边坡中湿度场分布情况,并得到膨胀土基坑边坡膨胀应力随深度分布,近似为不规则的梯形。(3)利用莫尔—库伦强度理论和极限平衡条件,推导了考虑膨胀应力作用时,主动土压力和被动土压力公式,分别为(4)以龙潭寺某基坑项目为例,对膨胀应力,侧向压力计算方法进行示例计算。结果证明膨胀力对基坑边坡侧向压力有非常大的影响。在进行支护设计计算时,考虑膨胀力的作用,其基坑顶部位移,基坑底部位移及计算嵌固深度均变大,因此设计时应考虑膨胀力的影响。
[Abstract]:Expansive soil is mainly composed of strong hydrophilic clay minerals (such as montmorillonite, Illite and kaolinite). It has a special swelling structure, strong dilatancy and shrinkage, multiple fissures and strength attenuation of high plastic cohesive soil. Through the investigation of expansive soil foundation pit in Chengdu area, it is found that the slope of expansive soil foundation pit will be deformed or cracked due to rainfall and pipe seepage. The expansion force is the main cause of foundation pit instability. However, there is no clear stipulation on its distribution in the existing relevant codes of expansive soil, so it is impossible to consider the effect of expansion force in the design and calculation of support. As a result, the foundation pit support design can not meet the engineering needs. Based on the study of lateral pressure of expansive soil foundation pit slope, the influence of expansion force on lateral pressure is discussed in order to provide basis for design and calculation of supporting structure. The main contents and conclusions are as follows: (1) based on the literature on expansive soil and expansion stress, and by using the knowledge of mechanics and thermodynamics of unsaturated soil, the calculation of expansion stress is studied, and the formula P 蟺 = 魏 ln 蠅 0 / 蠅 1 is deduced. Combined with the variation curve of soil moisture content with depth, the expansion stress distribution with depth in semi-infinite space is analyzed. The slope of expansive soil foundation pit is partitioned with moisture field theory. The distribution of moisture field in expansive soil foundation pit slope is discussed. The expansion stress distribution of expansive soil foundation pit slope with depth is obtained, which is approximately irregular trapezoidal.) based on Mohr-Coulomb strength theory and limit equilibrium condition, the formulas of active earth pressure and passive earth pressure are derived when the expansion stress is taken into account. Taking a foundation pit project in Longtan Temple as an example, the calculation method of expansion stress and lateral pressure is calculated. The results show that the expansion force has a great influence on the lateral pressure of foundation pit slope. In the calculation of support design, the effect of expansion force is considered, the displacement of the top of the foundation pit, the displacement of the bottom of the foundation pit and the calculation of the embedded depth are all increased, so the influence of the expansion force should be considered in the design of the foundation pit.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU443

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