密贴下穿既有结构的地下工程微沉降主动控制技术研究

Study on the Micro-settlement Active Control Technology of the Existing Structures in Close-attached Undercrossing Engineering

本文较全面地介绍地铁站下穿既有站采用的"平顶直墙CRD+复合式主动支顶"工艺,包括其设计思路、顶撑平台设计、施工关键技术、沉降机理分析等。该工法在传统平顶直墙暗挖工法基础上,综合考虑开挖横断面施工步序及纵向施工步骤,将隧道的开挖过程中不同时空效应带来的复杂受力转换与顶撑技术有机结合,创造性地提出"与开挖隧道横、纵向时空效应相结合的复合式主动支顶工艺",以此来解决既有站沉降控制技术难题。采用本工艺施工后,实现了全过程的主动沉降控制,既有站测点中最大沉降值2.9 mm。本文经理论论证及实践修正后,提出密贴式下穿既有线施工的设计及施工关键技术方针。该技术对采用预顶撑工艺的下穿既有线工程具有较强的技术指导意义。

The method, called ＂flat-roofed straight wall CRD ＋ composite active supporting＂, and used in the construction of the subway station undercrossing the existing station, was comprehensively introduced in this paper, including the design ideas, top-bracing platform design, key construction technology and settlement mechanism analysis, etc. Based on the bur- ied-excavation method of traditional flat-roofed straight wall, when considering the excavation cross-section construction pro- cedures and longitudinal construction steps, and combining the complex stress conversion with top-bracing technology brought by different time and space effects in the tunnel excavation, we creatively proposed ＂a composite active supporting technology that combined the horizontal and vertical spatial and temporal effects of the excavation tunnel＂ to solve the settle- ment control technique problems of the existing station. An active settlement control during the whole process was achieved and the maximum settlement value of the existing station was 2.9 mm when applying the technology. Furthermore, the key technological guidelines for design and construction of close-attached undercrossing the existing railway engineering was sug- gested by a theoretical demonstration and a practical amendment, which could provide a strong technical guiding signifi- cance for undercrossing the existing railway project with pre-supporting technique.