高填明洞土压力卸载模型试验和数值模拟研究

发布时间：2018-06-19 04:20

本文选题：高填明洞 + 土压力　；参考：《兰州交通大学》2015年硕士论文

【摘要】：明洞作为采用明挖法修筑的隧道结构的一种,在由山、原、川三大地貌类型构成主体的黄土高原被广泛使用。交通的迅速发展促进了城市化进程的加快,也使得城市用地日趋紧张,削山造地、深沟回填成为了创造城市用地的一大主要途径。因而,针对于明洞回填的工程也逐渐增多,回填高度也逐渐增大,而由于多数明洞设计之初大都未考虑明洞上方高回填情况,不断增大的明洞回填土压力成为了影响明洞正常安全使用的重要不利因素之一。高填方明洞土压力问题属于高填结构物土压力问题范畴,而目前对于高填结构物土压力的研究则主要集中在涵洞(管)方面,对于高填明洞研究较少。回填过程中不断增大的土压力将对明洞结构安全产生极其不利的影响,导致明洞结构病害的产生。基于以上问题的出现,本文围绕明洞回填过程中采取何种措施达到减小明洞所受土压力及确定卸载后明洞顶土压力两方面问题开展了研究。首先,根据不同卸载设置条件下的的室内模型试验,得到回填过程中明洞土压力变化规律;然后,建立有限元分析模型,对影响卸载作用下明洞土压力影响因素进行了探究;最后,根据室内试验和有限元分析结果,依据岩土力学理论,对加筋卸载作用下的明洞顶土压力进行了理论计算公式推导。主要结论如下:(1)通过对不同卸载设置条件下的高填明洞土压力模型试验的土压力、土体沉降实测得到:无论设置卸载措施与否,明洞回填过程中,洞顶、洞脚土压力随填土高度都呈非线性变化;减小明洞内外土柱沉降差绝对值而有利于明洞顶土压力的减小,且设置方式不同,卸载效率不同;在设置低压实度孔的条件下,土工格栅的铺设有利于进一步减小明洞洞顶土压力,但由于格栅变形空间有限,多层减载效果不明显;增大明洞两侧填土压缩模量对提高低压实土和土工格栅组合卸载措施的卸载率有积极作用;填土高度不大时,明洞顶土压力可近似采用土柱法γH计算,填土高度增大,土柱法不再适用。(2)建立有限元分析模型,分析结果表明:明洞回填过程中,明洞顶产生土拱效应有利于明洞顶土压力的减小;各因素分析中,低压实度孔的设置对于减小明洞内外土柱沉降差绝对值影响最大,因而对明洞顶土压力大小影响也最为显著。(3)参照室内模型试验、有限元分析结果,建立边坡存在条件下的加筋卸载高填明洞顶土压力计算模型,以等沉面高度Hc为界,推导得到了不同填土高度下的明洞顶土压力计算公式,为高填土明洞及其减载结构设计及施工提供理论参考。
[Abstract]:As one of the tunnel structures constructed by the method of open excavation, the Ming Cave is widely used in the Loess Plateau, which is composed of three main geomorphological types: mountain, original and Sichuan. The rapid development of transportation accelerates the process of urbanization and makes urban land use more and more tense. Cutting mountains and making land, deep ditch backfill has become one of the main ways to create urban land. As a result, the number of backfill projects for the Ming Cave is increasing gradually, and the backfill height is also gradually increasing. However, most of the design of the Ming Cave does not consider the high backfill situation above the Ming Cave at the beginning of the design. The increasing backfill pressure has become one of the important unfavorable factors affecting the safe use of the tunnel. The earth pressure problem of high filling open tunnel belongs to the category of high fill structure soil pressure, but at present, the study of high fill structure earth pressure is mainly focused on culvert (pipe), but the research on high fill open tunnel is less. The increasing earth pressure in the backfill process will have an extremely adverse effect on the structural safety of the open tunnel, resulting in the occurrence of the structural diseases of the open tunnel. Based on the above problems, this paper focuses on two aspects: what measures should be taken to reduce the earth pressure of the open tunnel and how to determine the earth pressure of the roof of the open tunnel after unloading. Firstly, according to the indoor model tests under different unloading conditions, the variation law of soil pressure in the open tunnel during backfilling is obtained, and then, the finite element analysis model is established to explore the influencing factors of the soil pressure in the open tunnel under the action of unloading. Finally, according to the results of laboratory tests and finite element analysis, and based on the theory of geotechnical mechanics, the theoretical calculation formula for the earth pressure of the open roof under the action of reinforcement and unloading is derived. The main conclusions are as follows: (1) through the soil pressure of the model test of the high filling tunnel under different unloading conditions, the settlement of the soil is measured: no matter whether the unloading measures are set up or not, the roof of the tunnel in the course of backfilling is obtained. The soil pressure at the bottom of the tunnel varies nonlinear with the height of the fill, and reducing the absolute value of the settlement difference between the soil column inside and outside the tunnel is beneficial to the reduction of the soil pressure at the top of the tunnel, and the setting way is different, and the unloading efficiency is different. Under the condition of setting the hole with low compaction degree, The laying of geogrid is conducive to further reducing the earth pressure at the top of the tunnel, but the effect of multi-layer load reduction is not obvious because of the limited deformation space of the grid. Increasing the compression modulus of the filling on both sides of the open tunnel has a positive effect on increasing the unloading rate of the combined unloading measures of low-pressure solid soil and geogrid, and when the filling height is small, the earth pressure of the roof of the tunnel can be calculated approximately by using the soil column method 纬 H, and the height of the fill will increase. Soil column method is no longer applicable. (2) the finite element analysis model is established. The results show that the soil arch effect at the top of the open tunnel is beneficial to the reduction of the earth pressure of the open roof in the course of the backfilling of the open tunnel, and in the analysis of various factors, The setting of low compaction hole has the greatest influence on reducing the absolute value of settlement difference of soil column inside and outside the open tunnel, so it also has the most significant effect on the soil pressure of the roof of the open tunnel. (3) referring to the results of indoor model test and finite element analysis, In this paper, a calculation model of the earth pressure at the top of a reinforced and unloading high filling tunnel is established under the condition of slope existence. Taking the equal settlement height HC as the boundary, the formula for calculating the earth pressure of the open top of the tunnel with different filling heights is derived. It provides a theoretical reference for the design and construction of high-fill open tunnel and its load-reducing structure.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU432

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