黄土地铁隧道近距离下穿既有地铁构筑物变形与力学行为研究

发布时间：2018-03-13 22:18

本文选题：黄土地铁　切入点：下穿构筑物　出处：《长安大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着城市地下空间的不断开发,地下交通线网的不断完善,地铁线路之间的立体交叉将会成为很常见的工程。近接工程施工条件复杂、既有地铁线路安全控制要求严格。因此,城市地铁近距离下穿既有地铁构筑物具有施工难度高、施工技术复杂、安全风险大等特点。对于西安黄土地区,由于黄土受外界各种荷载的影响其性质会发生变化,产生较大变形,这会对新建地铁隧道下穿既有地铁构筑物的施工产生较大影响,对既有地铁构筑物的安全稳定构成威胁。这也是西安地铁穿越工程面临的一大难题。鉴于此,本文依托西安地铁5号线下穿地铁2号线实体工程,通过现场调查、数值计算,研究黄土地层因新建地铁隧道的施工,既有地铁构筑物的变形和力学行为,得出如下主要结论:(1)新建隧道的施工对既有地铁结构会造成一定程度的影响,当新建地铁结构采用浅埋暗挖法施工时,既有地铁结构以沉降变形为主;既有地铁结构表现为整体沉降,在实际工程中,监测基点的选择将直接影响监控量测所得结果的准确性与可靠性。(2)既有隧道对地层具有一定的加固作用,且随着深度的增加,既有隧道对地层变形的影响效果越明显。由于既有隧道两侧土体有背离既有隧道运动的趋势,在既有隧道两侧,地层会出现一定的松弛带,再远处会有一定宽度的压密带。(3)既有地铁结构受力是波浪形的,新建地铁隧道轴线两侧一定范围内,既有结构仰拱受拉,拱顶受压,再远处受力相反。结构受力最大值出现在新建地铁隧道轴线所在断面,且结构的安全性取决于所受最大拉应力。(4)参考结构受力分区结果,同时以国内既有类似工程、西安现有的近接工程,以及国内相关规范和地方标准为基础,确定既有地铁结构沉降控制标准及分区指标,并对结构沉降变形进行分区,分为危险区、报警区、预警区和安全区。(5)当下穿净距为0.1D时,新建隧道下穿既有线按沉降控制一般的施工方法进行施工是不可靠的,而当下穿净距不小于0.2D时,采用相应的预加固措施可确保安全。所以,在实际工程中,若无法避免的要采用非常小的净距下穿既有地铁构筑物时,需要采用可有效控制变形的开挖方法,需要采用加固刚度大、加固范围广的预加固措施,以确保既有线的安全。
[Abstract]:With the continuous development of urban underground space and the continuous improvement of underground traffic network, the intersection between subway lines will become a very common project. It is difficult to construct, the construction technology is complex, and the safety risk is great. For Xi'an loess area, the nature of loess will change due to the influence of various external loads. This will have a great impact on the construction of the new subway tunnel under the existing subway structure and pose a threat to the safety and stability of the existing subway structure. This is also a major problem facing the Xi'an subway crossing project. In this paper, the deformation and mechanical behavior of the existing subway structures due to the construction of the new subway tunnel are studied by the field investigation and numerical calculation based on the entity project of Xi'an Subway Line 5 passing through Metro Line 2. The main conclusions are as follows: (1) the construction of the new tunnel will have a certain degree of influence on the existing subway structure. When the new subway structure is constructed by shallow underground excavation, the settlement deformation of the existing subway structure is the main one. The existing subway structure is characterized by integral settlement. In the actual engineering, the selection of monitoring basis points will directly affect the accuracy and reliability of the results obtained from the monitoring measurements. (2) the existing tunnels have a certain reinforcement effect on the strata, and with the increase of depth, the existing tunnels have a certain reinforcement effect on the strata, and with the increase of the depth, The effect of the existing tunnel on the formation deformation is more obvious. Due to the tendency of the soil on both sides of the existing tunnel deviating from the movement of the existing tunnel, there will be a certain relaxation zone on both sides of the existing tunnel. Further away, there will be a certain width of compaction belt. (3) the force on the subway structure is wavy. In a certain range on both sides of the axis of the new subway tunnel, the inverted arch of the existing structure is pulled and the arch roof is compressed. The maximum stress of the structure appears in the section of the axis of the new subway tunnel, and the safety of the structure depends on the maximum tensile stress. Based on the existing adjacent engineering in Xi'an, as well as the relevant domestic and local standards, the settlement control standards and zoning indexes of existing subway structures are determined, and the settlement and deformation of the structures are divided into dangerous areas and warning areas. When the net distance between the warning zone and the safety zone is 0.1D, it is not reliable to construct the existing railway under the new tunnel according to the general settlement control method, while the current penetration distance is not less than 0.2D. The safety can be ensured by adopting the corresponding pre-reinforcement measures. Therefore, in practical engineering, if it is unavoidable to use a very small net distance to penetrate the existing subway structure, it is necessary to adopt the excavation method which can effectively control the deformation. In order to ensure the safety of the existing railway line, it is necessary to adopt pre-reinforcement measures with high stiffness and wide range of reinforcement.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U231.3;U455.4

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