Technicaland Economic Analysis Of Qingdao Underground Excavation Metro Station Based On Comparison Of Design Scheme And Construction Method

With the rapid development of China's economy and the accelerating urbanization process,the urban rail transit industry has developed rapidly in the past decade.By the end of 2017,34 cities in China had opened rail transit and put into operationm,165 rail transit lines were opened with the operating mileage of 5033 Km.The subway accounted for77.2% and the other including light rail,monorail,city express,tram and maglev train accounted for 22.8%.In the construction of subway projects,the subsurface excavation method is favored by people due to its strong adaptability to complex construction sites and less environmental impacts.However,the engineering cost of the subway project is too high.The construction of the underground excavation project is closely related to geological conditions and the design method determined by the environmental conditions.The unsuitable construction method will lengthen the construction period and increase the engineering cost,the worse was the loss of life and property duo to he engineering risk accident.Therefore,the study based on geological hydrology,structural type under environmental conditions,design method and construction process is of great significance to the subway excavation project.This paper takes Qingdao Subway Junfeng Road and Zaoshan Road Mined Underground Metro Station project as an example,The main work has done as follows:(1)According to environmental condition of the different geology,the hydrological condition,the Ground Traffic,the laying pipeline and the Situation of Surrounding buildings,to analyze The structural design scheme of Mined Underground Metro Station.the Junfeng Road subway station is 6.5-17 m in buried depth.It is mainly located in the light weathered granite strata.the site of water abundance is Poor and the water is less.the structure form are wholly-covered waterproofing of single arch long span double layer structure.using both side heading method.the Zaoshan Road subway station is 13.5~22m in buried depth.The surrounding rock is better overal,fracture development is local.the groundwater is rich.using theType of restricted discharge and part Waterproof and structure of circular archvertical side wall,due to arch covering Construction method.Mined Underground Metro Station located in different geology,hydrology,surroundingenvironment,station structure selection,excavation and support forms,structure waterproof and drainage mode and project investment are different to varying degrees.(2)According to different geological conditions and structures,the paper analyzes the construction scheme of mined underground metro station from construction method and construction sequence.The two stations have different structural types and construction methods:Junfeng road station adopts the method of double sidewall tunnel construction,the whole section adopts grille steel frame,shotcrete and system anchor initial support,and adopts the profile steel as temporary next door support.There are as many as 9 tunnel excavation,the process is relatively complex,which has certain influence on the construction period;The section construction on the station of Zaoshan road adopts the method of double sidewall tunnel excavation,adopting the grille steel frame,shotcrete and system anchor initial support,the lower section adopts the slope excavation of the middle groove and adopts the fully bonded anchorage side slope support.There are 3 guide holes in the upper part of the station,and the lower part of the step pull-out groove excavation,with relatively few procedures,which is conducive to the site construction organization and ensures the construction period.At the same time,the paper gives some suggestions to guarantee the construction period.(3)This paper discusses in detail two different construction conversion modes in the case.The train of thought and the way of force transformation are clarified,and gives the detailed construction steps to ensure the engineering safety of the major risk point.The construction transition from horizontal tunnel to main structure excavation is one of the most important risk points in the underground excavation project of the station.The construction transfer place is often blasting construction,repeatedly disturbing the surrounding rock,and the improper transformation may cause greater settlement and even risk events.(4)The paper detailed analyzed the construction method,initial support,secondary lining,construction monitoring,station decoration,and other engineering costs of station 's main structure of Junfeng Road and Zaoshan Road underground station,conclusion as below,The initial support,temporary support and auxiliary measures for the construction of Mined Underground Metro Station are the key to cost.Choosing accurate and reasonableinitial support parameters,optimizing construction procedures,and reducing auxiliary works can reduce the cost.The station of arch-cover method is superior to the station of Two Side-wall Pilot Tunnel in terms of cost and construction period.And through these aspects of cost personnel intervention in the initial design stage,the design changes were reduced in the construction stage,the construction safety guarantee system was established,and the investigation work of demolition and land acquisition was completed,Relevant suggestions were provided to reduce the cost of the subway project.It is hoped that the research content of this paper can provide reference for the subway construction in Qingdao and other cities.