【作者】 张国亮；

【导师】 余志武；

【作者基本信息】 中南大学 ， 土木工程， 2012， 博士

【摘要】 为了解决城市交通拥堵问题,缓解交通压力,适应国民经济发展的需要,城市轨道交通得到快速发展,地铁车站基坑工程也呈现出“大、深、紧、近”等特点。由于深基坑工程事故的多发性及后果的严重性,基坑工程作为一个古老又具有时代特点的结构与岩土工程问题,又逐步引起同行越来越多的关注。本文依托中国铁路工程总公司重点课题——紧邻既有线基坑设计与施工关键技术研究(项目编号：200902),针对深圳地铁5号线民治站和五和站基坑工程纵向全长紧邻既有线铁路或公路的复杂工程背景,综合运用现场试验、室内试验、理论分析和数值模拟等方法,研究了紧邻既有线不对称超载深基坑的稳定性及变形规律,主要研究内容和成果如下：(1)针对民治车站和五和车站纵向全长平行高路堤既有线,存在严重不对称静力超载和机车动载影响的问题,开展了现场列车动载试验,基于动载测试结果,采用动力和等效静力分析方法,研究了动、静载作用下不对称超载基坑围护结构体系的静、动力响应,获得了不同工况下围护结构内力、沉降变形、水平位移、既有线沉降等变化规律,评价了不对称超载基坑围护结构设计方案的合理性和适应性。(2)分别对等效静载、不考虑机车动载、机车运行时速60km/h、80km/h、120km/h等五种工况进行了参数对比研究。机车运行时速为120km/h时,动载影响系数可达到1.2,对围护结构体系受力和变形影响显著。而机车时速低于60km/h时,动载影响系数小于5%,设计验算时机车动载可简化为等效土柱静载作用。(3)为满足既有线路基不均匀沉降变形控制标准和支护结构稳定性的要求,通过现场动载测试及理论分析,明确提出既有线限速60km/h的安全运行标准,确保了基坑开挖施工和既有线运营安全。(4)依托民治站和五和站不对称超载基坑工程,选择典型测试断面,进行了连续墙水平位移和沉降、支撑内力、既有线沉降及水平位移等项目的大量现场监测,获得了不对称超载基坑围护结构体系的受力和变形规律,提出了不对称超载基坑围护结构体系的荷载模式和位移模式。不对称超载作用下,基坑开挖深度达到某一“临界深度”,围护结构体系出现整体扭转趋势,超载侧内力和变形明显大于无超载侧,无超载侧地连墙上部发生指向基坑外侧的水平位移,相应该部位主动土压力转变为被动土压力。(5)针对不对称超载基坑两侧围护结构受力特性的不同及存在向无超载侧整体偏转的变形特点,提出了不对称超载基坑围护结构体系采取非对称性支护的设计方法,以及对超载侧采取主动加固等技术措施,以平衡单侧高路堤不对称超载的影响。更多还原

【Abstract】 In order to reduce traffic pressure and to solve the problem of city traffic jam, so as to adapt to the needs of the development of national economy, urban rail traffic has developed rapidly. And then the station foundation pit engineering becomes some new characteristics, such as more larger, deeper, closer and adjacent. Because of the multiple characteristics and serious consequences of the accidents about deep foundation pit engineering, deep foundation pit engineering, as an old structure and geotechnical engineering problems, has some new characteristics, then it gradually cause more and more attention. This paper is finished based on the major project supported by China Railway Engineering Corporation, named Research on Design and construction Key Technology of Foundation Pit near Existing Rail Line (No.200902). The foundation pit of Minzhi station and Wuhe station in Shenzhen subway No.5line, which longitudinal side of foundation pit parallels the existing railway or road line with high embankment. According to the complex engineering background of the foundation pit, research are carried out by field test, laboratory test, theory and numerical analysis, and the characteristics of the stability and deformation features of the foundation pit close to existing lines is studied. The main research contents and results are as follows:(1) According to the asymmetric overload of deep foundation pit of Minzhi station and Wuhe station, and its stability influenced by vehicle dynamic load induced by the high embankment existing lines, plenty of dynamic load tests are carried out. Based on the dynamic test results, the static or dynamic response of the supporting structure system for foundation pit are studied by the static and dynamic analysis method. The rules of the internal force, settlement and deformation, horizontal displacement of the supporting structure system, and the settlement of existing line under different conditions are obtained. The rationality and adaptability of the design program about supporting structure of deep foundation pit under action of asymmetric overload is evaluated. (2) The parameter study about the stability of supporting structure system of foundation pit under the five conditions, such as the equivalent static load, no locomotive dynamic load and locomotive speed of60km/h,80km/h,120km/h is carried out. when locomotive running speed is120km/h, dynamic load effect coefficient reaches1.2, its effects on the deformation and internal force of supporting structure system of foundation pit is prominent. But when the Locomotive speed is less than60km/h, dynamic load has little influence, and the dynamic load influence coefficient is less than5%. During the design analysis, locomotive dynamic load can be simplified as equivalent soil column static load when the Locomotive speed is less than60km/h.(3) Based on the results of test and theoretical analysis, the safe standards of the60km/h limited speed is put forward to meet the requirement of the settlement deformation standard for the existing line and the stability of supporting structure, and to ensure the safety of the foundation pit excavation construction and the existing line.(4) Relying on the foundation pit project of Minzhi station and Wuhe station, site tests including the displacement and internal force of the diaphragm wall or the braces, and settlement of the existing line. The characteristics of internal force and deformation for supporting structure system of deep foundation pit with asymmetric overload is summarized by the tests of the typical section. Based on the test and theoretical analysis results, the load and displacement model of the retaining structure of the foundation pit with asymmetric overload are proposed. Under action of the asymmetric overload, supporting structure system will appear the overall reverse trend when the foundation pit excavation depth reaches a ritical depth, the internal forces and deformations of the diaphragm wall at overloading side is significantly greater than the results of no overloading side. After the excavation depth reaches a ritical depth, the deformation direction of the upside of the diaphragm wall at no overloading side will point to outside of foundation pit. At the same time, the original active earth pressure in this region of diaphragm wall, which deformation direction pointing to outside of foundation pit, changes to passive earth pressure. (5) Based on the great difference such as the stress of supporting structure and the deformation direction of retaining structure system points to no overloading side of foundation pit, the asymmetric design method of the foundation retaining structure and the technical measuresis, such as take the initiative reinforcement for The overload side, etc, are put forward to balance asymmetric overload induced by high embankment.更多还原