【作者】 李宁；

【导师】 赵法锁；

【作者基本信息】 长安大学 ， 岩土工程， 2010， 硕士

【摘要】 地面沉降是国内外都十分关注的一种复杂环境地质问题,是指自然和人为因素作用下,由于地壳表层土体压缩而导致区域性地面标高降低的现象。它是一种缓发型灾害,不易被人们觉察,具有持续时间长、影响范围广、成因机制复杂和防治难度大、易发性、累进性、不可逆等特点,对人民生活、社会经济及可持续发展构成严重的威胁。西安作为举世闻名的世界四大古都之一,也出现了严重的地面沉降灾害,自上世纪70年代至上世纪末,地面沉降愈演愈烈,由此给西安地区造成了巨大的经济损失。因此正确认识西安地面沉降形成规律,并对其机理进行研究,对人民生活和经济发展具有十分深远的意义。本文在介绍了西安地区地质背景的前提下,首先对西安地区地面沉降形成过程作了详细的论述,指出过量抽汲地下水是地面沉降主要原因。其次从自然因素和人为因素两方面分别对西安地面沉降形成机理进行了较深入的分析。(1)自然因素主要是针对区域构造、地震、土体自重、黄土湿陷性等因素的影响进行分析,最终得出自然因素并非引起西安地面沉降的主导因素；(2)人为因素针对西安地区抽汲地下深层承压水和城市建设所引发的地面沉降进行了分析,其中重点对抽水引起的深层承压含水层垂直沉降和水平变形作了详细的分析,并阐明了沉降漏斗形成的机理；论文同时提出城市建设已成为现今地面沉降问题不容忽视的因素。在第五章,论文以Biot三维固结理论为基础,采用FLAC2D软件对西安地区地质技工学校处的地面沉降进行了二维数值模拟与土体—渗流耦合计算。通过分析模拟的计算结果,发现模拟结果与实际监测的结果是基本吻合的,这表明了地面垂直沉降和水平位移的特征和机理分析的正确性,同时也证实了数值模拟模型和编制的程序命令的合理性和正确性。最后,针对本次论文并结合目前对西安地面沉降的研究提出了结论和建议。更多还原

【Abstract】 Land subsidence is one kind of complex environmental and geological problems which has attracted attention from home and abroad. It is a phenomenon that regional ground elevation is lowered by the compression and deformation of soil mass in the veneer of crust under both natural and man-made factors. It is a slow onset disasters, which is difficult for people to detect. And it is also has many characteristics, such as long duration, wide range of influence, complex genetic mechanisms, difficult to control, easy onset, progressive, irreversible, etc. So the land subsidence has been threatening people’s life, socio-economic and sustainable development seriously. There has been serious land subsidence in Xi’an, which is one of the four famous ancient capitals of the world, since the 70s of last century, Xi’an area suffered enormous economic losses due to the land subsidence. Therefore, it has very far-reaching significance to study the law and mechanism of the development of land subsidence for both people’s life and the economic sustainable development.This paper describes the geological background of Xi’an area, with which as a prerequi-site, firstly, it discusses the development process of land subsidence in Xi’an in detail, pointing at that excessive pumping of groundwater is the main reason for land subsidence.Secondly, based on the comprehensive consideration of natural factors and human facto-rs, mechanism of the land subsidence in Xi’an is analyzed in-depth. As follows:(1) Natural Factors The paper analyzes from some aspects, such as regional tectonics, earthquakes, soil weight, collapsible loess, and so on. From which we came to the conclusion that natural factors are not the dominant factor of land subsidence in Xi’an area.(2) Human Factors In this part, the paper studies from both pumping pressure deep underground water and urban construction’s influences. This article focused on the mechanism of the deep confined aquifer’s vertical displacement and horizontal deformation, which is caused by pumping. And it also explained the formation mechanism of the ground subsidence conical depression. In the final part of this section, the author indicates that modern urban construction can not be ignored for impacting on land subsidence.In Chapter V, on the basis of the Biot consolidation theory, the paper selects the land subsidence which is near the Geological Technical School in Xi’an city, and uses FLAC2D software to make two-dimensional numerical simulation and soil-seepage coupling calcula-tion. By analyzing the simulation results, the author finds that the simulation results are generally consistent with the monitoring results. On the one hand, it shows that the analysis of the characteristics and mechanism of ground’s vertical settlement and horizontal displacement is correct. On the other hand, it confirms the rationality and correctness of the numerical simulation model and the code orders.Some conclusions and proposals are put forward in the end of this paper, which is combined with the current study on the land subsidence.更多还原