拱北隧道开挖与支护方式分析研究

发布时间：2018-02-28 09:35

本文关键词： 超浅埋超大断面软土隧道 ANSYS 三次衬砌　出处：《武汉工程大学》2014年硕士论文　论文类型：学位论文

【摘要】：研究以某穿越软土地层超大断面、超浅埋双层公路隧道为例，系统的研究了该地层下隧道的开挖支护形式，对开挖过程中的临时支护、初期支护及二次衬砌进行了数值模拟，同时对三次衬砌的强度和稳定性进行了分析，分析对比了两种中板连接形式的优劣。首先对超浅埋、超大断面的隧道的发展以及研究现状进行了分析，对现有隧道围岩计算理论进行了分析归纳，然后系统的介绍了拱北隧道的开挖支护方法，包括超前支护，冷冻法，注浆工法等。对隧道所采用的临时支护、初期支护、二次衬砌及三次衬砌进行了介绍。利用ANSYS有限元程序建立平面模型对隧道开挖支护的全过程进行了模拟分析，对开挖过程中土体的应力场和位移场进行了分析，对临时支撑、初期支护和二次衬砌的内力进行分析，并对该种地质情况下的超前支护与初期支护的改进措施进行了初步的探讨，得出结论：（1）隧道开挖时是做了型钢临时支撑，由分析计算可知，竖向支撑的轴力是由上到下越来越来大，且竖向临时支撑的轴力较横向临时支撑大，故应采用的竖向支撑要比横向支撑强度，刚度大。（2）水平临时支撑与竖向临时支撑都要承受一定的弯矩，特别是横向与竖向支撑的连接节点处弯矩较大，所以施工时必须重视该节点的连接精度、连接强度与刚度，，以防止支撑在受弯时节点张开影响施工时的安全。（3）随着隧道台阶的开挖进行，土体的塑性区也在向深部发展。第四台阶的开挖后，隧道拱顶围岩除竖向支撑的支撑点附近外，均进入受拉区，且受拉区的影响的区域变大，故在隧道施工中应密切关注第四台阶的开挖，提前做好防范措施。利用ANSYS对施工期间和运营期间的三次衬砌的强度进行了分析检算，对中板与边墙的连接形式进行了研究分析，同时对三次衬砌的施工及设计提出了建议。最后对该隧道的设计与施工进行了总结，并对城市超浅埋大断面隧道的设计及研究提出了建议：对于穿越城市密集建筑及政治敏感区的隧道，若不能封闭地面交通，采用双层暗挖隧道结构是可行的。由于受到地面交通的影响，加之隧道本身的开挖跨度大、埋深小、地质条件差，由隧道开挖引起的地层损失可能引起地表沉陷甚至冒顶，故隧道开挖前采取强有力的超前支护措施是必要的。超前管幕法的使用可以最大限度的减少地面沉降，并减低地面交通对隧道开挖的影响，可以推广使用。同时配合冷冻法和洞内注浆加固，可保施工期间的安全。同时也指出了有待进一步研究的问题：研究采用数值分析是基于设计施工提出的，能基本反映隧道在施工过程中力学动态，可为类似隧道工程的设计与施工提供参考。
[Abstract]:Taking a super-large section and super-shallow double-layer highway tunnel through soft soil as an example, this paper systematically studies the excavation support form of the tunnel under the stratum, and simulates the temporary support, the initial support and the secondary lining during the excavation process. At the same time, the strength and stability of the third lining are analyzed, and the advantages and disadvantages of the two kinds of medium plate connection are analyzed and compared. First of all, the development and research status of super-shallow buried tunnel and super-section tunnel are analyzed, and the calculation theory of surrounding rock of existing tunnel is analyzed and summarized. Then, the excavation and support methods of Gongbei tunnel are introduced systematically, including advance support. Freezing method, grouting method and so on. This paper introduces the temporary support, initial support, secondary lining and third lining used in tunnel. The whole process of tunnel excavation support is simulated and analyzed by using ANSYS finite element program to establish plane model. The stress field and displacement field of soil during excavation are analyzed, and the internal forces of temporary bracing, initial support and secondary lining are analyzed. The improvement measures of advance support and initial support under this kind of geological condition are discussed preliminarily, and the conclusion is drawn:. The axial force of vertical bracing is more and more large from top to bottom, and the axial force of vertical temporary bracing is larger than that of lateral temporary bracing. Therefore, the vertical support should be used than the transverse support strength, stiffness. 2) both horizontal temporary support and vertical temporary support have to bear some bending moment, especially the moment at the connection joint of horizontal and vertical support is large, so we must pay attention to the connection precision, connection strength and stiffness of the joint during construction. To prevent the support in the bending of the joint opening to affect the safety of construction. 3) with the excavation of the tunnel steps, the plastic zone of the soil is also developing to the deep. After the excavation of the 4th steps, the surrounding rock of the tunnel arch all enter the tensile zone except near the supporting point of vertical support, and the area affected by the tensile zone becomes larger. Therefore, the excavation of 4th steps should be paid close attention to in tunnel construction, and preventive measures should be taken in advance. This paper analyzes and calculates the strength of the third lining during construction and operation by using ANSYS, studies and analyzes the connection form between the plate and the side wall, and puts forward some suggestions for the construction and design of the third lining. Finally, the paper summarizes the design and construction of the tunnel, and puts forward some suggestions on the design and study of the super-shallow tunnel with large section: if the ground traffic can not be closed for the tunnel that passes through the dense buildings and politically sensitive areas of the city, It is feasible to adopt double-layer tunneling structure. Due to the influence of ground traffic, the tunnel itself has a large span of excavation, small buried depth and poor geological conditions, the ground loss caused by tunnel excavation may cause ground subsidence or even topping. Therefore, it is necessary to take strong advance support measures before tunnel excavation. The use of advanced pipe curtain method can minimize land subsidence and reduce the influence of ground traffic on tunnel excavation. It can be popularized and combined with freezing method and grouting in the hole, which can guarantee the safety during construction. At the same time, the problems that need further research are also pointed out. The numerical analysis is based on the design and construction, which can basically reflect the dynamics of the tunnel in the construction process, and can provide a reference for the design and construction of similar tunnel engineering.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455

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