流变特性对黄土边坡稳定性影响初探

发布时间：2018-11-13 12:38

【摘要】：我国中西部地区黄土分布广泛且深厚,由于历史上对黄土区森林的过度开发加上长期水土流失的作用,使得如今的中西部黄土区形成了大量的黄土边坡,严重制约着西部地区基础设施建设的发展。流变特性是黄土材料的主要力学特性之一。已有工程实例表明,自然界中许多的黄土边坡在失稳前都表现出了明显的流变现象,即边坡的失稳与边坡土体的流变性质有关。因此,如何在边坡稳定性分析中考虑边坡土体的流变性质对边坡工程的发展具有十分重要的意义。本文主要研究黄土流变特性对边坡稳定性的影响,同时将考虑黄土流变特性的边坡稳定性分析方法与传统的理想弹塑性强度折减法和极限平衡法进行对比。通过分析三种方法计算出的边坡潜在滑动面位置的不同、安全系数差异和边坡位移的大小,得出三种方法的异同。通过对不同坡高和不同坡脚的边坡模型进行计算分析,得出以下结论:(1)三种边坡稳定性分析方法计算出的滑面位置均是一条通过坡脚贯穿整个坡体的圆弧面,其中极限平衡法和理想弹塑性强度折减法计算出的滑面位置几乎是相同的,流变强度折减法计算出的边坡潜在滑动面在坡顶处更靠近边坡临空面,在滑面最低处更靠近模型底部。通过分析理想弹塑性强度折减法和流变强度折减法计算出的边坡滑动带可以发现,使用流变强度折减法计算出的不同边坡模型的潜在滑动带始终处于理想弹塑性强度折减法计算出的边坡潜在滑动带内部,说明流变强度折减法计算出的潜在滑动带宽度小于理想弹塑性强度折减法计算出的边坡潜在滑动带宽度。(2)三种方法计算出的安全系数中,考虑流变的强度折减法计算出的安全系数最小,极限平衡法的计算所得安全系数最大,理想弹塑性强度折减法计算得出的边坡安全系数大小处于两者中间。极限平衡法与理想弹塑性强度折减法计算出的边坡安全系数较为接近,相对差值约为1%-2%,流变强度折减法计算得出的安全系数与另外两种方法计算所得安全系数差值较大,相对差值约为5%-11%,说明流变特性对边坡稳定性的影响较大。(3)考虑流变的强度折减法和理想弹塑性强度折减法计算出的边坡位移中,在折减系数小于流变强度折减法计算出的安全系数时,流变强度折减法计算出的边坡位移值较大,且二者边坡位移差值稳定,不随折减系数的增加而变化。当折减系数大于安全系数时,流变强度折减法计算所得边坡位移明显大于理想弹塑性强度折减法计算所得边坡位移,且二者差值随着折减系数的增加逐渐增大。因此进行边坡位移监测的过程中,在设定边坡位移预警值时应考虑边坡土体的流变性质。
[Abstract]:Loess is widely and deeply distributed in the central and western regions of China. Because of the overdevelopment of the forest in the loess region in history and the effect of long-term soil erosion, a large number of loess slopes have been formed in the loess region of the central and western regions today. It seriously restricts the development of infrastructure construction in the western region. Rheological property is one of the main mechanical properties of loess materials. Engineering examples have shown that many loess slopes in nature show obvious rheological phenomena before instability, that is, the slope instability is related to the rheological properties of slope soil. Therefore, how to consider the rheological properties of slope soil in slope stability analysis is of great significance to the development of slope engineering. In this paper, the influence of loess rheological characteristics on slope stability is mainly studied. At the same time, the slope stability analysis method considering loess rheological property is compared with the traditional ideal elastic-plastic strength reduction method and limit equilibrium method. By analyzing the difference of the potential sliding surface location, the safety factor and the displacement of the slope calculated by the three methods, the similarities and differences of the three methods are obtained. Through the calculation and analysis of the slope models with different slope heights and different slope feet, the following conclusions are drawn: (1) the position of the sliding surface calculated by the three slope stability analysis methods is a circular arc through the whole slope body through the foot of the slope. The position of the slip surface calculated by the limit equilibrium method and the ideal elastic-plastic strength reduction method is almost the same, and the potential sliding surface of the slope calculated by the rheological strength reduction method is closer to the empty surface of the slope at the top of the slope. It is closer to the bottom of the model at the lowest point of the sliding surface. By analyzing the slip zone calculated by the ideal elastic-plastic strength reduction method and rheological strength reduction method, it can be found that, The potential slip zone of different slope models calculated by rheological strength reduction method is always inside the slope potential slip zone calculated by ideal elastic-plastic strength reduction method. It shows that the width of potential slip band calculated by rheological strength reduction method is smaller than that calculated by ideal elastic-plastic strength reduction method. (2) among the safety factors calculated by the three methods, The safety factor calculated by the strength reduction method of rheology is the smallest, the safety factor by the limit equilibrium method is the largest, and the safety factor of the slope calculated by the ideal elastic-plastic strength reduction method is in the middle of the two. The limit equilibrium method is close to the slope safety factor calculated by the ideal elastic-plastic strength reduction method, and the relative difference is about 1-2. The difference between the safety coefficient calculated by the rheological strength reduction method and that obtained by the other two methods is quite large, and the relative difference is about 5- 11. It shows that the rheological characteristics have a great influence on the slope stability. (3) in the slope displacement calculated by the strength reduction method and the ideal elastic-plastic strength reduction method, when the reduction coefficient is less than the safety factor calculated by the rheological strength reduction method, The value of slope displacement calculated by rheological strength reduction method is large and the difference of slope displacement between them is stable and does not change with the increase of reduction coefficient. When the reduction coefficient is greater than the safety factor, the slope displacement calculated by rheological strength reduction method is obviously larger than that calculated by the ideal elastic-plastic strength reduction method, and the difference between the two values increases gradually with the increase of the reduction coefficient. Therefore, in the process of slope displacement monitoring, the rheological properties of slope soil should be considered when setting the early warning value of slope displacement.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444

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