Research On Security Control Of Shield Tunnel Close Under-crossing The Exist Overlap Tunnel

At present,with the inerease of our country's urban metro network construction and the wider use of technology of shield, more and more adjacent shield tunnel construction are taken up close to the existing MTR lines.lt has been an urgen tnd key issues to researeh effeets of the shield tunnel close to the existing MTR lines, and, accordingly put forward the corresponding targeted controlling measures.This paper is based on the project that the shiled tunnel of yanda section of Shenzhen Metro No.2 line under-crossing No.l line. Analyse and research on the construction security of shield tunnel close crossing the existed line in upper-soft and bottom-hard geological condition. This paper Includes contents as follows:(1) numerical simulation about shield close crossing the existed line;(2) monitor and measure the whole crossing process, including electronic tachometer automatic monitoring in the tunnel,static level automatic monitoring and the artificial monitoring. Compare and analyse the difference between the monitoring data and the numerical analysis data.(3) Reasonable choice of the tunneling parameters is the critical part of success. Through the practical selection of the tunneling parameters in the construction, this paper puts forward the reasonable shield parameters in geological conditions of this construction.Through the experience of construction security control getting from the shield tunnel close under-crossing the existed line in upper-soft and bottom-hard geological condition, it can provide important reference for similar construction project.