水侵城市土质路基地面塌陷机理的研究

发布时间：2018-02-05 17:05

本文关键词： 城市道路地面塌陷地下空洞塌陷机理水侵蚀　出处：《中国矿业大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来，我国城市道路中发生了多起地面塌陷安全事故，该事故具有突发性、隐蔽性的特点。地陷会吞噬来往的人员和车辆，同时还会影响上部结构的安全，造成人员的伤亡和财产的损失。这已引起社会各界的广泛关注。本文以城市土质地层为研究背景，综合运用相似理论、伯努利原理、ANSYS有限元等理论和方法，研究了城市道路下伏空洞与管线渗漏侵蚀之间的关系，了解渗流水的流量、管线断裂间距、冲蚀时间等因素与地下空洞发展扩张的几何形状、尺寸之间的关系，并且探讨了道路塌陷的力学机理和影响因素的作用规律，为以后防治此类灾害提供理论基础和依据。主要进行了以下工作：首先，通过物理相似试验，使用半结构模型的试验方法，在流量约为230ml/s的情况下，分别研究了排水管线和给水管线在断裂之后流水侵蚀路基致地下空洞的规律。认为排水管线一般会在地下形成一个较扁平的椭球形空洞，其侵蚀速度最快的时候有近1.7m/h；另一方面，给水管线断裂之后由于巨大的压力，往往会出现大面积地表积水的现象。之后，为了解地面塌陷的力学机理，，结合ANSYS有限元技术，分析了地面塌陷时其地表的沉降量、应力和塑性区分布的情况。主要结论如下：在其他因素不变的情况下，随着地下空洞的长度的增加，地表的沉降量增加，地表形成的沉陷漏斗也越深，最终在某一长度的时候发生的整体的塌陷；在数值模拟中，地下空洞埋深为3m、长度约为15m时出现整体塌陷；本文还认为地面塌陷的主要破坏形式为剪切破坏，整体会呈现一个圆柱形剪切破坏塌陷面；城市道路塌陷前的征兆表现为地表的位移迅速的发展和地表裂缝产生。再后，运用数值模拟和正交试验的方法，在已知地下空洞（3m埋深）在某一临界跨度时会发生整体地面塌陷的情况下，研究了各主要影响因数的对该临界埋深的影响。主要结论：影响城市道路塌陷临界长度的因素中，折减系数的影响最大，其次为宽长比，最后为高长比；在短边长度一定的时候，可以认为越是扁平狭长的地下空洞越是容易出现地面塌陷。最后，对比了有硬化层和无硬化层地层条件地面塌陷的情况，得出的主要结论：硬化层的作用在于提高了整个地层的刚度，使得整个路面结构在不利荷载条件下更加的平整，行车过程中体验更加舒适，但是同时也增加了土层的承受的荷载值，因此路基在下伏空洞的情况更容易被压坏土基，在事实上更容易导致地面塌陷的发生。
[Abstract]:In recent years, there have been many ground collapse safety accidents on urban roads in China, which have the characteristics of sudden and concealment. The ground subsidence will engulf people and vehicles, and will also affect the safety of superstructure. Causing casualties and property losses, which has caused widespread concern from all walks of life. In this paper, based on the urban soil strata as the research background, using the similarity theory, Bernoulli principle and ANSYS finite element theory and other theories and methods, the relationship between the underground voids and pipeline leakage erosion in urban roads is studied. The relationship between seepage water flow, pipeline fracture spacing, erosion time and the geometry and size of underground cavity expansion is investigated. The mechanical mechanism of road collapse and the action law of influencing factors are discussed, which provides the theoretical basis and basis for the prevention and control of such disasters in the future. The main work is as follows: First of all, through the physical similarity test, using the semi-structural model test method, at the flow rate of about 230 ml / s. The regularity of income's erosion of subgrade cavities caused by the breakage of drainage pipeline and feed pipe line is studied respectively. It is considered that drainage pipeline will generally form a flat ellipsoidal cavity in the underground. The highest rate of erosion was about 1.7 m / h; On the other hand, because of the huge pressure after the water supply line breaks, there often appears the phenomenon of massive surface water accumulation. Then, in order to understand the mechanical mechanism of the ground collapse, combined with the ANSYS finite element technique, the surface subsidence of the ground collapse is analyzed. The main conclusions are as follows: with the increase of the length of the underground cavity, the settlement of the surface increases, and the subsidence funnel is deeper. The collapse of the whole at a certain length; In the numerical simulation, when the buried depth of the underground cavity is 3 m and the length is about 15 m, the whole collapse occurs. It is also considered that the main failure form of the ground collapse is shear failure, and the whole will present a cylindrical shear failure collapse surface. The signs of urban road collapse are the rapid development of surface displacement and the formation of surface cracks. After that, numerical simulation and orthogonal test are used, when the underground cavity is known to be buried at 3 m depth, the whole ground collapses will occur at a critical span. The main conclusions are as follows: among the factors affecting the critical length of urban road collapse, the reduction coefficient is the most important, followed by the ratio of width to length, and finally, the ratio of height to length; When the length of the short side is fixed, it can be considered that the more flat and narrow the underground cavity is, the more likely it is to collapse on the ground. Finally, the paper compares the ground collapse between the hardened layer and the non-hardened layer, and draws the main conclusion: the role of the hardened layer is to improve the stiffness of the whole stratum. Make the whole pavement structure in the adverse load conditions more flat, traffic experience more comfortable, but at the same time also increased the load value of the soil. Therefore, the cavities in the subgrade are more likely to be crushed, and in fact, the ground collapses are more likely to occur.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.16

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