Research On Ground Settlement Of Metro Station Construction By Pile-Beam-Arch (PBA) Method

With the increasement of vehicle and buildings, the underground rail transit is becoming the most popular public transportation. Metro station is the hinge of underground rail transit. Because of the large span, shallow depth and poor geology of metro station, PBA method, as a new method for metro station construction, could reduce the settlement of ground effectively, and further keep buildings safety in it is construction process.Based on the aforementioned situation, this paper takes SongJiang Road metro station as engineering background, uses MIDAS-GTS to establish numerical model for analysis of the general rule of ground settlement in PBA method. And then, based on the general rule, the influence of construction parameters on ground settlement of PBA method is studied. Several main concluded aspects are listed as follows:1. Obvious stages of ground surface settlement can be observed during construction process. Pilot tunnel construction is the main reason for ground surface settlement. After the excavation of the rest soil, ground surface settlement reduces because of the weight loss of metro station.2. The construction sequence of pilot tunnel is one influence factor of plastic area. Plastic area is lager around the later construction pilot tunnel. The development of plastic area can be contained after the establishment of pile-column-beam system established.3. Due to the different construction sequence of pilot tunnel, the ground settlement and ground surface settlement trough develop differently. Among all the possible sequences, the excavation sequence upper to lower, middle to edge would cause the least ground surface settlement.4. The forecast result of settlement and settlement trough width based on the stochastic medium theory is larger than the numerical results. For this reason, the forecast result is safety. And compare with the maximum settlement of each sequence, the maximum forecast result is 2.3% to 9.3% larger than numerical result, for which the forecast result has a certain accuracy.5. When the interval of column is lower than 20m, the ground settlement is increasing with the development of interval. The maximum ground surface settlement is almost linear with column interval.6. When the sectional area of column is smaller than 2.5mx2.5m, the ground settlement is reducing with the increasement of sectional area, the maximum ground surface settlement is nonlinear with sectional area. When sectional area arrives 1.5mx1.5m, the maximum ground surface settlement tends to be stable. Sectional area is no more the main reason for influent ground surface settlement.