复杂条件下管幕—冻结地层预处理技术研究

发布时间：2018-01-08 01:25

本文关键词：复杂条件下管幕—冻结地层预处理技术研究　出处：《北京交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：摘要：本文介绍了超浅埋、大断面、近海、不利地层及复杂周边环境条件下隧道开挖的特点和通常采取的工程措施,着重分析了超前地层预处理技术的作用和特点。对比分析了常见的地层预处理方法的优缺点和适用性,重点研究了管幕-冻结综合预处理地层技术相关的理论和应用。针对管幕-冻结综合地层预处理技术,将理论分析与现场实测数据结合,以拱北隧道冻结法施工为工程实例,采用FLAC3D进行数值模拟,对顶管顶进过程对地层的扰动、顶管施工的相互影响、管幕形成以后对于地层稳定性的作用、冻结施工过程中的冻结温度场的变化、冻胀融沉引起的地表位移、冻胀角敏感性及冻结壁厚度的影响等进行详细的分析。研究了管幕法和冻结法的作用机理,分析管幕和冻结圈分别在地层预处理过程中发挥的作用,研究管幕-冻结预处理地层技术的综合作用。得出了如下结论： (1)只有成环的顶管帷幕才能有效地综合控制围岩的变形。 (2)单个顶管顶进对于隧道围岩的扰动较小；后顶进顶管对于先顶进顶管的扰动较小。 (3)采用冻结法预处理地层时,地层位移可以分为三个阶段：冻结膨胀阶段；开挖支护阶段；冻土融化阶段。开挖支护阶段的地层位移绝对值比另外两阶段小。冻土融化阶段的地层位移绝对值为三个阶段最大。 (4)随着冻胀率的增大,冻结过程中土体的位移随之增加,土体中产生的附加压应力也随之增大。冻结壁的厚度的增加对于控制地表沉降的作用明显。冻胀率过大时,不适宜采用冻结法。冻结壁的最佳厚度为2.5m左右。 (5)管幕法和冻结法结合可以相互弥补不足。冻结法可以利用冻结圈将单个顶管联接成一个整体,改善顶管帷幕的受力性能,使其充分发挥加固围岩,减小变形的作用,同时可以封堵地下水；而顶管法既可以形成冻结圈的骨架,使其更好发挥临时支护的作用,又可以减小冻结过程中的土体膨胀和融化过程中土体的位移,减小地层扰动。
[Abstract]:Abstract: this paper introduces the characteristics of tunnel excavation under ultra-shallow burial, large cross-section, offshore, unfavorable strata and complex surrounding environment and the usual engineering measures. The function and characteristics of advanced formation preprocessing technology are emphatically analyzed, and the advantages and disadvantages and applicability of common formation preprocessing methods are compared and analyzed. The theory and application of integrated preconditioning of pipe curtain and freezing are studied in this paper. In view of the pipe curtain freezing comprehensive stratum pretreatment technology, combining the theoretical analysis with the field measured data, taking the freezing method construction of the Gongbei tunnel as an engineering example, the numerical simulation is carried out by FLAC3D. The disturbance of the jacking process to the formation, the interaction of pipe jacking construction, the effect of pipe curtain formation on the formation stability, the change of freezing temperature field during freezing construction, the surface displacement caused by frost heave and thawing subsidence. The effects of frost heaving angle sensitivity and freezing wall thickness are analyzed in detail. The mechanism of tube curtain method and freezing method are studied, and the roles of tube curtain and freezing ring in the formation pretreatment process are analyzed respectively. The comprehensive effect of tube-freezing pretreatment stratigraphic technology is studied. The following conclusions are obtained: Only the annular pipe jacking curtain can effectively control the deformation of surrounding rock. 2) the disturbance of single jacking pipe to tunnel surrounding rock is small, and that of back jacking pipe to first jacking pipe is small. 3) when the strata are pretreated by freezing method, the strata displacement can be divided into three stages: freezing expansion stage; Excavation and support stage; The absolute value of stratum displacement in excavation and support stage is smaller than that in the other two stages, and the absolute value of stratum displacement in frozen soil thawing stage is the largest in three stages. 4) with the increase of frost heaving rate, the displacement of soil increases during the freezing process. The additional compressive stress in the soil increases with it. The increase of the thickness of the freezing wall plays an important role in controlling the surface settlement. When the frost heaving rate is too large. The optimum thickness of freezing wall is about 2.5 m. The combination of pipe curtain method and freezing method can make up for each other. Freezing method can be used to connect a single pipe jacking into a whole, improve the mechanical performance of pipe jacking curtain, so that it can make full use of the surrounding rock reinforcement. The effect of deformation can be reduced, and the groundwater can be blocked at the same time. The pipe-jacking method can not only form the skeleton of the freezing circle, make it play the role of temporary support better, but also reduce the displacement of soil in the process of freezing and melting, and reduce the disturbance of stratum.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.49

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