Analysis of the Reinforcement Effect of a Shallow Buried Large Section Rectangular Pipe Jacking Tunnel over an Existing Tunnel in Complex Strata
With the development of urban underground transportation and frequent construction in the vicinity of underground structures,effective isolation and protection measures are important for the safety of underground structures.Taking the pipe jacking project at an underground hub station of the Fuzhou Binhai Express Line as an example,the finite element software PLAXIS was used to establish a numerical model of shallow buried large section pipe jacking across existing lines in complex underground spaces.The influence of the construction of shallow buried large section pipe jacking on the surrounding environment under the combined effect of pipe isolation and MJS ground reinforcement was analyzed.The calculation results show that:① The pipe curtain reinforcement can effectively reduce the surface settlement in the area,and the control effect of"mouth"shaped fully enclosed pipe curtain on surface settlement can reach 87％,only the upper and lower rows of pipe curtain can reduce 34.9％compared with the case without pipe curtain;②The maximum value of arch bottom uplift is about 2.9 mm when pipe curtain+MJS reinforcement,when only MJS reinforcement is used,the maximum arch bottom uplift is 3.2 mm,and without any reinforcement,the maximum arch bottom uplift is 3.9 mm;③ The existing subway tunnel,with the reinforcement of the pipe curtain and MJS,ultimately controls a maximum uplift of 2.36 mm.The results of the study can be used as a reference for surface settlement control of shield and pipe jacking construction and isolation and protection measures for adjacent underground structures in coastal silty clayey ground.
existing tunnelsabove crossingpipe curtain isolationMJS reinforcementnumerical model
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