STUDY ON STRUCTURAL SCHEMES OF METRO STATION CONSTRUCTION BY ENLARGING LARGE-DIAMETER SHIELD TUNNEL

摘要

The problem of shield machine driving through metro station is well solved by enlarging shield tunnel combined with undercutting method, which can play the advantages of shield construction and minimize the impact on environment.This method is realistic to construct metro fast,efficiently, and safely in more complicated urban environment.Taking Jiangtai Station of Beijing Metro line 14 as an experimental project, a new-style scheme for metro station construction was described.The scheme was excavating the metro station based on a large shield tunnel with an outer diameter of 10m.According to the environment and the design requirements of Jiangtai Station,enlarging shield tunnel with pile-beam-arch (PBA) method or cross diagram (CRD) method were proposed.And the structural characteristics and mechanics performance between two schemes were compared.Three-dimensional finite element models were used to simulate the step-by-step construction process of the metro station.Results show that two schemes are all feasible in structural mechanics.The critical condition in construction process is the complete segment rings in an open state with the remainder segments working together with primary linings.The excavation scheme of PBA method is better than CRD method in construction safety and ground surface settlement control.