锚杆格构梁在膨胀土边坡加固中的受力机理与设计方法研究

发布时间：2018-10-19 12:58

【摘要】：滑坡是一种常见的地质灾害,地质、气候、人类活动的变化等都会对滑坡的发生产生一定的影响。研究发现,与普通土质边坡相比膨胀土边坡滑坡具有明显的浅层性和牵引性等特点,并认为膨胀性是边坡发生破坏的主要原因,此外裂隙性、干湿循环以及超固结性都会对边坡的稳定性产生一定的影响。锚杆格构梁是利用格构梁进行坡面防护,同时利用锚杆加以固定的一种综合防护措施,由于其积极有效的支护效果,在边坡加固工程中得到了广泛的应用,特别是对于膨胀土等特殊土质边坡的加固效果尤为明显。然而相对实际应用来说,现有的理论研究中对于锚杆格构梁在膨胀土中的理论研究还相对较少,当考虑土体膨胀性时,锚固体的轴力是否会发生变化,变化趋势如何,以及考虑膨胀性时边坡的稳定性是否会发生变化,这些都是需要考虑的重要问题。针对以上不足,本文研究了如下内容,并得到了相应的结论:(1)根据弹性力学中的变形协调方程,推导膨胀应力与膨胀应变之间的关系,并根据已有研究成果推导得出膨胀土膨胀影响Z0范围内任意深度处土体的位移量,为后面章节考虑土体间相对位移提供计算依据。(2)本文借鉴桩基的受力特性来研究膨胀土中的锚固体受力。据弹性理论,在考虑膨胀土膨胀性的基础上,通过考虑土体-锚固体间的相对位移,对锚杆格构梁结构进行受力分析,得出了膨胀区域及非膨胀区域内锚固体的轴力及摩阻力解析解,通过算例分析其变化规律,并针对锚固体长度、直径及膨胀影响深度等可能产生影响的因素进行参数分析,并验证其合理性。(3)根据前人研究的膨胀土膨胀规律,利用瑞典条分法,计算考虑膨胀土不同膨胀阶段的边坡稳定系数。中性点理论是岩土锚固中的重要理论,通常把锚杆中无相对位移发生且摩阻力为零的点定义为中性点。以膨胀深度与中性点的位置关系为界,将膨胀阶段分为初期和减缓期两个阶段。通过算例分析验证,证明膨胀初期为土体急剧膨胀阶段,在锚固体与膨胀土界面会产生负摩阻力,使得边坡稳定系数在短时间内呈现增长趋势;而随着土体膨胀的减缓,界面出现正摩阻力,边坡稳定系数逐渐降低。(4)结合镇江象山边坡加固工程,运用岩土分析软件MIDAS/GTS建立三维边坡模型,把有限元计算结果与本文理论方法计算结果进行对比,证明本文方法的可行性、合理性及经济性。
[Abstract]:Landslide is a common geological hazard, geology, climate, human activities and other changes will have a certain impact on the occurrence of landslides. It is found that compared with ordinary soil slope, expansive soil slope has obvious characteristics of shallow layer and traction, and it is considered that expansion is the main reason of slope failure, in addition, fracture is also found. Dry-wet circulation and over-consolidation will affect slope stability to some extent. Anchor lattice beam is a kind of comprehensive protective measure which uses lattice beam to protect slope surface and is fixed by anchor rod. Because of its positive and effective supporting effect, it has been widely used in slope reinforcement engineering. Especially for expansive soil and other special soil slope reinforcement effect is particularly obvious. However, compared with the practical application, there are relatively few theoretical studies on anchoring lattice beam in expansive soil. When considering soil expansion, whether the axial force of anchor body will change and what the change trend is, It is important to consider whether the stability of slope will change when considering expansibility. In view of the above deficiencies, the following contents are studied and the corresponding conclusions are obtained: (1) according to the deformation coordination equation in elastic mechanics, the relationship between expansion stress and expansion strain is derived. According to the existing research results, it is deduced that the swelling of expansive soil affects the displacement of soil at any depth in the range Z0. It provides the basis for the later chapters to consider the relative displacement of soil. (2) this paper uses the mechanical characteristics of pile foundation to study the stress of anchoring body in expansive soil. According to the elastic theory, considering the expansive property of expansive soil and considering the relative displacement between soil and anchor body, the stress of the lattice beam structure is analyzed. The analytical solutions of axial force and frictional resistance of anchors in expansive and non-expansive regions are obtained. The variation law of anchors is analyzed by an example. The parameters of anchors such as length, diameter and depth of expansion are analyzed. The rationality of the method is verified. (3) according to the expansion law of expansive soil studied by predecessors, the slope stability coefficient considering different expansion stages of expansive soil is calculated by using Swedish slice method. The neutral point theory is an important theory in rock and soil anchoring. Usually, the point in which there is no relative displacement and the friction resistance is zero is defined as the neutral point. Based on the relationship between the depth of expansion and the position of neutral point, the expansion stage is divided into two stages: the initial stage and the slow stage. Through the example analysis and verification, it is proved that the initial expansion stage is the rapid expansion stage of soil, and the negative friction will occur at the interface between the anchor body and the expansive soil, which will make the slope stability coefficient increase in a short period of time, but with the slow down of soil expansion, the stability coefficient of the slope will increase in a short period of time. Due to the appearance of positive friction at the interface, the slope stability coefficient decreases gradually. (4) combined with the strengthening project of Xiangshan slope in Zhenjiang, a three-dimensional slope model is established by using the geotechnical analysis software MIDAS/GTS, and the finite element calculation results are compared with the calculated results of the theoretical method in this paper. The feasibility, rationality and economy of this method are proved.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU472

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