【作者】 魏龙海；

【导师】 王明年；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2009， 博士

【摘要】 近年来,随着我国社会经济的发展,城市人口快速增加,越来越多的城市开始规划和修建地铁。由于我国幅员辽阔,不同地区地质情况差异很大,一些新建地铁在施工期间遇到了非常复杂的地质条件,如成都地铁1、2号线沿线广泛分布的卵石地层等。卵石地层一般由粘性土或砂卵石、粗砂、卵石等组成,偶遇巨石块,大多数砂卵石地层结构松散,分布不匀,具有强烈的离散特性,与砂土、黏土等的工程性质有着本质区别。目前,在该地层中应用明挖、盾构及浅埋暗挖等施工方法修建的地下工程案例很少,几乎没有现成的经验可供借鉴。随着成都地铁工程的全面展开,如何安全经济的在卵石地层中进行地铁建设是一个亟待解决的问题。据此,本文针对成都地铁1、2号线建设期间遇到的几个重点问题：卵石地层深基坑土压力大小及分布规律、盾构隧道开挖面稳定性、暗挖法施工时的合理预支护措施及工法等进行了系统的研究,其工作具体体现在以下几个方面：1.建立三轴数值试验模型,对模型中颗粒单元的性质进行多组试样的参数比较研究,分析细观参数对材料宏观物理力学特性的影响规律,并据此对成都地铁1、2号线沿线密实、中密及稍密卵石土体的宏观参数和模型细观参数的关系进行标定；然后通过理论分析和数值计算相结合,验证应用颗粒离散元模拟基坑围护桩等支护结构的可行性,并标定支护结构的宏观物理力学参数与其数值模型细观参数之间的关系。2.针对卵石土体本身结构具有强烈的离散特性的特点,利用颗粒离散元数值方法,对墙体平动、绕墙顶转动及绕墙底转动三种变位模式下卵石地层基坑土压力的大小及分布规律进行了研究,通过将数值模拟结果与经典土压力的计算结果进行比较,确定了平动模式下卵石土基坑土压力的修正计算方法；依托成都市历史上埋置最深(28.5m)、规模最大(占地面积约48000m2)的天府广场深基坑工程,探明了卵石地层基坑破坏、坍塌的演化过程。利用本文的卵石地层基坑土压力修正计算方法,分析了不同支护条件下基坑施工安全性,确定了天府广场深基坑合理的开挖及支护方案。3.根据成都地铁1号线区间盾构隧道的施工情况,对支护压力较小时,卵石地层盾构开挖面坍塌破坏过程及坍塌破坏时前方土体应力分布演变情况进行了模拟分析,明确了盾构施工开挖面变形与破坏的机理,提出了卵石地层盾构隧道开挖面破坏坍塌模式。探讨了卵石地层中盾构开挖面支护压力大小对隧道围岩变形及压力影响规律,并将此影响分为三个阶段,即影响不敏感阶段、影响敏感阶段、破坏失效阶段；据此,对目前盾构隧道开挖面极限支护压力的计算模型进行了发展,建立了适用于卵石地层盾构隧道开挖面极限支护压力的三维计算模型。在此过程中,还通过挡板下移数值模拟试验,探讨了松动土压力大小与挡板位移量的关系,针对太沙基松动土压力计算值与数值模拟结果差值偏大的情况,修正了上覆土压力的计算公式。最后利用本文的三维计算模型,对成都地铁1号线ZDK13+630处采取带压进舱换刀的舱内极限压力进行了分析。4.结合成都地铁1号线天府广场北端暗挖隧道试验段,利用颗粒离散元数值方法,对卵石地层浅埋暗挖隧道破坏、坍塌的机理进行了分析。探明了管棚、小导管及正面锚杆(管)等预支护措施在卵石地层中的作用效果,给出了合理的预支护方法及其参数；分析了CD法和台阶法对隧道施工安全性的影响,得出了卵石地层浅埋暗挖隧道的合理开挖工法。更多还原

【Abstract】 In recent years, with China’s social and economic development, the urban population increasing rapidly, so more and more cities began to plan and build the subway. However, because China has a vast territory, the geological conditions are great difference in different regions, some new metro encountered to the very complexed geological conditions during the construction, such as the cobble stratum which is widely distributed along Chengdu Subway line 1 and 2. Generally speaking, the cobble stratum consisting of the cohesive soil, pebble soil, coarse sand, gravel and so on, and occasional consisting of the giant stones. Most the structure of cobble stratum are loose, and theirs distribution were not even. The engineering properties of the cobble stratum is essential different from the sand or the cohesive soil, it has strongly discrete character. At present, the underground engineering which are builded by the open cut method, shield-driven and mining excavation method in cobble stratum is seldom, and there is no exsisting experience can be referenced. With the comprehensively launches of Chengdu subway project, building the subway safely and economically in cobble stratum is the key problem which is needed to be solved. Hereby, according to the several key problems needed to be solved which encountered during building Chengdu Subway line 1 and 2, the earth pressure distribution of cobble stratum,the tunnel face stability and the construction projects were studied in this dissertation. which embodies in 4 ways as follows:1. Through establishing the triaxial numerical test model, studied the parameters of the particles by many samples test and analysed the influence law of meso parameter to the characteristics of materials macromechanics. And according to the law, calibrated the meso parameters and macro parameters of the dense, medium dense and slightly dense sandy pebble soil in chengdu subway line 1 and 2. And the feasibility of which using the granular discrete element to simulate the foundation pit enclosure piles was discussed by the theoretical analysis and numerical method, and then calibrated the macro physical and mechanical parameters and meso parameters of the supporting structure.2. According to the discrete character of cobble stratum, using granular discrete element numerical method, studied the earth pressure distribution of cobble stratum foundation pit when the wall move with basic modes-translation(T), rotation about base(RB), rotation about top(RT), and the correction calculation method of earth pressure of cobble stratum foundation pit based on the translational wall-movement modes’has been determined by compared the compute results with the classical theory. And then,according to the tianfu-square foundation pit which was the most depth(28.5 m) and the largest scale (area is about 48000m2) in chengdu history, the failure and collapse evolution process were proved. And finally, using the correction calculation method of earth pressure of cobble stratum foundation pit which was proposed in this paper, analysed the construction safety of foundation in several different support condition and dicided the reasonable construction and supporting scheme of tianfu-square foundation pit.3. According to the construction situation of shield tunnel in Chengdu subway line 1, the face collapse and failure process of cobble stratum shield and the stress distribution evolution of the soil during the excavation surface collapsing were simulated and analysed, and he deformation and failure mechanism of the shield excavation surface was made clear, the collapse and failure modes of cobble stratum shield tunnel excavation face was put forward.And then the influence law of surrounding rock deformation and stress by the varying support pressure of excavation surface in cobble stratum shield tunnel was discussed, The relation between face support pressure and soil deformation indicates that the influence of support pressure can be figured as three stages,that is insensitive stage, sensitive stage and failure stage. Hereby, the 2-dimension mode of shield tunnel face limit support pressure was improved and the 3-dimension calculation model of limit support pressure which is suitable for cobble stratum shield tunnel face was established. In the process, By the numerical simulation test of baffle move, discussed the relationship between loosening earth pressure and baffle displacement. According to the large difference of results by terzaghi theory and numerical computation, modified the terzaghi calculation formula. Finally, the limit pressure in shield module at ZDK13+630 in chengdu Subway line 1 was analysed by the 3-dimension limit support pressure calculation mode which is established in this dissertation.4. According to the construction condition of the shallow bury subsurface excavation test section in chengdu subway line 1, the failure and collapse mechanism of shallow bury subsurface excavation in cobble stratum were analysed by particle discrete element method. The action effect of the advance support such as pipe roof, small pipe and front anchor in cobble stratum shallow bury subsurface excavation tunnel was proved, and the reasonable pre-supporting method and its parameters were given. And then the effection of working security by CD method and bench method in the cobble stratum shallow bury subsurface excavation tunnel was analysed, the results showed that the bench method have some advantages in the cobble stratum shallow bury subsurface excavation tunnel at construction dewatering condition.更多还原