Study On Schemes Of The Expanded Metro Station Under Shield Running Tunnel

Because of the increasingly tense, certain locations may not have conditions for the construction of the station in advance in the future metro construction. But in order to facilitate passenger’s travel, where the locations have the conditions opened to traffic but no conditions for the construction of the metro station need to open to traffic operations first. Start the expand construction of the metro station until the time is ripe. Therefore, the future metro line constrction may encounter many suituations that start the expand construction of the metro station under the conditon of traffic operation.On the basis of previous studies of our research group, this paper make further research against the problem of the metro station expansion under shield running tunnel under the conditons of traffic operation.In this article,some special place where the station can not be built in time will be reserved for the expansion construction condition.The side platform area and shield running tunnel are listed as the first phase project, the main station platform area is listed as the second phase project. After the completition of the first phase project,then train traffic operations are permitted. Start the construction of the second phase project without disrupting train operations until the time is ripe.This article discusses three themes respectively, the inner diameter of shield of the three program are 7 meters、8.1 meters and 11.3 meters. Numerical simulation analysis is made via using FLAC3D finite difference software and engineering economic analysis is made in this article. This article will provide technical references for the design and construction of the follow-up similar project. The results show that:(1) To the scheme which shield inner diameter is 7 meters and the scheme which shield inner diameter is 8.1 meters,d position of the fourth ring segment (see Figure A of Table 4-5 in the text) is bend axis control section in retain shield segment structure of the station driving range.Its internal forces eccentricity gradually increase in the tube sheet removal construction and station enlarging excavation construction construction.This increase is about 20 percent more than the condition of interval shield only. But the corresponding axial force is minimum.(2) To the scheme which shield inner diameter is 11.3 meters,e position of the fourth ring segmentsee (see Figure A of Table 4-12 in the text) is bend axis control section in retain shield segment structure of the station driving range.Its moment remains maximum and moment value increases gradually in the construction of segment removal and the construction of station extension.(3) In the three schemes, the shear control section is a point of retain shield segment in the location of column(see Figure B of Table 4-6 in the text). When construction is completed, the shear force of this point is the maximum and corresponding axial force is the minimum.Shear failure prone to accur in this location. The shearing carrying capacity of the section can be improved by reducing the stirrups spacing in the actual design and construction.(4) After removing the shield segment, internal forces of remaining tube sheet structure readjusted. Line structure’s bearing role increased.Its internal force is abaot 15 percent to 20 percent of the total forces of the tube sheet and the liner. Because tensile stress occurs in some parts of the lining structure,The inforcements and stirrups of lining structure should be matched in accordance with the requirements of the component capacity in design and construction.(5) The cost of steel works take the largest share in the total cost, about 35% to 40%,the cost of concrete works after reinforced project, the cost of other projects (such as scaffold engineering, waterproofing engineering) after concrete and the cost of earthworks and grouting engineering occupies the minist partition of the total cost.In general, the cost of the scheme which shield inner diameter is 11.3 meters is highest, the cost of the scheme which shield inner diameter is 7 meters is second by the cost of the scheme which shield inner diameter is 11.3 meters, reduced by 41 percent. The cost of the scheme which shield inner diameter is 8.1 meters is lowest and it is 4 percent lower than the cost of the scheme which shield inner diameter is 7 meters. In addition, the cost of side platform scheme which shield inner diameter of 7 meters,8.1 meters is higher than the cost of island platform scheme.Therefore, from the perspective of project cost, the island platform scheme which shield inner diameter of 8.1 meters is best.