Complex Environment, The Construction Of The Mechanical Behavior Of Large Cross Section Cross Parts Of The Group Of Hole-hole Piles And Key Technologies

Gongtibeilu Station of Beijing Metro Line 10 which have complex environment,multi-chamber cross and multi-cavern effect obviously is separated island platform station. Construction mechanical behavior and key technologies of caven-PBA method applied to cross position of group large section tunnels have been studied in the thesis, with the methods of theoretical analysis,numerical simulation and field test. The main results are as follows:1. For the metro station in complex environment, the whole caven-PBA construction method is proposed, which combines the down straight method and top-down method of secondary lining. The interaction mechanism of piles,beams and arches in caven-PBA method is studied, and the corresponding construction measure which effectively reduce the formation of displacement is given. Specifically as follows:(1) The construction order of main tunnel and the arch buckle of connect tunnel direct influence their stiffness, and cause lack of co-ordination of deformation, stress concentration in the interface, especially tensile stress and a higher degree of shear stress concentration. So in the construction the time difference of main tunnel and the arch buckle of connect tunnel must as short as possible.(2) As the changes in stiffness, the stress-strain values, in the depth changes region of guide tunnel and geometric turning point region of all the guide tunnels the of connect tunnel, is relatively high, and the peak stress-strain appear the intersection of the main tunnel and the connect guide tunnel, especially the corner.(3) The top beams,piles,primary support ring beam of the intersection and the folded beam is constructed before the main arch completed, the stress of the top beam and pile is lower, but stress concentration is still appear in the intersection. The ring beam bear the all directions load before the additional beam completed and the connect tunnel opened, but the geometry is more bigger, the ring beam could delivery the load to the top beams and piles, and ensure the continuity of load transfer.(4) As the folded beam and primary support ring beam construct contemporarily, and from the geometry structural point, the folded beam and primary support ring beam, as arch bridge structure, are co-stressing, and the stress concentration is not obvious after the folded beam constructed. From all direction stress distribution, the regions of the high stress appear in the horizontal section the Partial middle tilt section and the corner of the two section intersection of the folded beam.2. The new integrated construction technology which based on the situation of limited hole space,deep large-size (h>8m,D>20cm) gravel strata and deep-pile is proposed in the metro station constructed by whole caven-PBA construction method, and the technology solve initially the deep-pile construction problem in deep large-size gravel strata.3. The bidirectional arch buckle integrated technology which means the primary and secondary tunnels adopt the caven-PBA method at the same time in cross position of group large section tunnels is proposed, and additional beam elements solve initially the construction problem of cross position of underground complex cavern.