Technical Study On Observational Method Applied To Shield Tunnel Undergonging Railway

The fundamental characteristics of tunnel engineering technology are the complexity of geological environment and difficulty to acquire data of geology, surrounding ground and design-load parameter accurately. The particularity of tunnel engineering determined many links such as reconnaissance and repetition in design and construction. Information construction could feedback information timely based on the practical monitoring condition during construction process, building the judgment rule of ground in ultimate stabilization time, ultimate distortion and so on, it could avoid magnitude accident availability, achieving the safety and economic of tunnel engineering.This article is on the base of the 9th Shanghai railway shield tunnel which pierces under the Nanxinhuan railway. This article detailed expounds basic theory of information construction and designs detailed field test scheme link with engineering characteristic. The test item is related to A and B type test including the displacement of earth's surface and stratum, dynamic stress of stratum caused by train vibration, concrete iron stress test and concrete strain in duct piece of lining, soil pressure at the back of duct piece of lining. In the process of construction, at the base of down line field testing and passing safely, this article studies on the monitored data and construction parameter and optimizes the shield driving parameter further which is taken for the basis of the up-line driving. During the up-line driving, field test will continue to go on and the information will be fed back for directing construction. Then the information construction method will exist from beginning to end and the trunk railway and environment around will be guaranteed. Finally, this article summarizes the successful points and shortcoming of foundation stabilization and construction down and up-line shield driving pierces under railway, then draws correlated conclusion. Finally, the sum-up was carried out towards the foundation reinforcement and the success and shortage of up or down track two times pass through railway in construction, and the contrast analysis was also carried out with 2D FEM model calculation, the correlative conclusion was gotat last.The research shows that foundation stabilization and optimizing the shield driving parameter combining with field test technique can make the shield tunnel pierce under trunk railway safely and smoothly. The result of field test shows that surface subsidence has be controlled at about lcm and the safety stock of stress in cross direction acts on the duct piece of lining is much higher. The effective analysis could be able to achieve towards ground surface settlement using plane calculation module with simple stress release, but homogeneous continuous structure which consider uniform reduction coefficient was not fit for structure inner force's calculation.