【作者】 刘玉平；

【导师】 赵文； 陈晨；

【作者基本信息】 东北大学 ， 建筑与土木工程（专业学位）， 2021， 硕士

【摘要】 横向洞盖法综合了洞桩法和管幕工法的优点,能够有效控制地铁车站暗挖施工时周边土体的位移,其显著特点就是在先行导洞内将管幕密排横向顶进车站顶板上方的土体中,然后在棚盖体系的支护下进行后续的开挖施工。先行导洞是顶管施工的起点,起着为顶管顶进提供后座反力的作用,是重要的承载结构,其安全与稳定至关重要。本文以沈阳地铁4号线市府大路站为工程背景,以横向洞盖法的先行导洞为研究对象,采用数值模拟等手段研究在砂土地层隧道内顶管对隧道结构受力特性的影响。主要工作和研究成果如下:利用Midas GTS NX有限元分析软件,就顶管作业隧道在开挖阶段与顶管阶段的位移场与应力场规律进行对比分析,得到顶进反力的主要影响范围在竖直方向上为整个后背高度,在水平方向上约为5倍荷载作用宽度。在主要影响范围内,后背土体水平位移与土压力的空间分布形态相似,在竖直方向上的分布形态介于“U”型和“V”型之间,在水平方向上的分布形态为“V”型。采用单一变量法详细研究了顶进反力的大小、作用位置、作用范围、初支的厚度与弹性模量以及后背土体的加固范围与加固程度等因素对隧道结构稳定性的影响规律,为设计和施工提供参考。研究表明:当土体达到被动极限状态后,土体水平位移会急剧增大,此后土压力仍将继续增大,但增大的速率会明显减慢。荷载作用在中部位置结构的应力和变形最大,上部次之,下部最小;增加初支厚度和弹性模量可以显著提高结构的承载能力,但当厚度或弹性模量达到一定数值后,继续增大厚度和弹性模量将无明显作用,即存在一个临界的初支厚度和弹性模量;同理,加固后背土体可以提高土体承载能力,有效控制土体的变形,而且加固土的范围和刚度也都存在明显的临界值。在分析极限状态下后背土体反力分布特点的基础上,提出了两种适用于砂土地层隧道内顶管后背土体反力的计算方法,并给出了允许顶力的计算公式。更多还原

【Abstract】 The Transverse hole cover method combines the advantages of the Pile-Beam Arch(PBA)Method and the Pipe Proofing Method,which can effectively control the displacement of surrounding soil during the underground excavation construction of subway station.Its remarkable feature is that the pipe curtain is pushed into the soil above the station roof in a close row in the pilot tunnel,and then the subsequent excavation construction is carried out under the support of shed cover system.Advance pilot tunnel is the starting point of pipe jacking construction,which plays the role of providing back reaction for pipe jacking.It is an important bearing structure,and its safety and stability are very important.In this paper,taking Shenyang Metro Line 4 Shifudalu station as the engineering background,taking the leading pilot tunnel of the transverse hole cover method as the research object,the influence of pipe jacking on the mechanical characteristics of tunnel structure in sandy soil layer is studied by means of numerical simulation.The main work and research results are as follows:By using Midas GTS NX finite element analysis software,the displacement field and stress field law of pipe jacking tunnel in excavation and pipe jacking stage are compared and analyzed.The results show that the main influence range of jacking reaction is the whole back height in vertical direction and about 5 times of load width in horizontal direction.In the main influence range,the spatial distribution of horizontal displacement and earth pressure of the back soil is similar.The vertical distribution is between U-type and V-type,and the distribution form in horizontal direction is V-type.The influence of the size,position,range of action,thickness and elastic modulus of the initial support,and the reinforcement range and reinforcement degree of the back soil on the mechanical characteristics of the tunnel structure are studied in detail by the single variable method,which provides reference for the design and construction.The results show that when the soil reaches the passive limit state,the horizontal displacement of the soil will increase sharply,and then the soil pressure will continue to increase,but the increasing rate will be significantly reduced.When the load acts on the middle position,the stress and deformation of the structure are the largest,followed by the upper position,and the smallest in the lower position.The increase of initial support thickness and elastic modulus can significantly improve the bearing capacity of the structure,but when the thickness or elastic modulus reaches a certain value,there is no obvious effect when the thickness and elastic modulus continue to increase,that is,there is a critical initial support thickness and elastic modulus;In the same way,the reinforcement of the back soil can improve the bearing capacity of the soil and effectively control the deformation of the soil,and there are obvious critical values for the range and rigidity of the reinforced soil.Based on the analysis of the distribution characteristics of the back soil reaction in the limit state,two calculation methods of the back soil reaction are proposed,which are suitable for pipe jacking in the sand layer tunnel,and the calculation formula of the allowable jacking force is given.更多还原