| Under the situation that urban land is getting tighter and tighter,the development of urban three-dimensional space,especially underground space,is imminent.In 2013,Jinan Municipal Government established the "one horizontal and two vertical" H-shaped urban development strategy,and the construction of R1,R2 and R3 lines started on a large scale,and the subsequent six lines will be fully started within the year.The explosive growth of deep foundation pits and ultra-deep foundation pits has led to a large number of design and construction problems.In particular,the selection of support solutions,protection of springs,precipitation and the impact of construction on the surrounding environment are more prominent issues.Jinan city is located in the northern edge of the mountainous area in central Lu.The overall topography is low in the north and high in the south,with rolling mountainous areas in the south;sloping plains in front of the mountains in the middle;and alluvial plains in the north.Due to the special geological structure and other factors,Jinan has achieved the reputation of "Spring City".Therefore,for the complex geological conditions and the unique spring culture in Jinan,the reasonable selection of foundation pit support is crucial,which is an important guiding significance for the rail transit construction projects to be carried out later.Relying on major livelihood projects in Jinan,this paper studies the deformation characteristics of foundation pits and the optimization of support schemes in Jinan for different geological subdivisions and groundwater distribution in Jinan.The following are the main research results.(1)Through data collection and preliminary research,the hydrogeological and engineering geological conditions within the rail transit planning area of Jinan City were summarized.And on this basis,the whole area is divided into five types of geotechnical structures,the Quaternary soil(Zone I),gabbro(Zone II),Quaternary soil + gabbro(Zone III),Quaternary soil + gabbro(Zone IV),and Quaternary soil + gabbro + gabbro combination(Zone V).The hydrogeological units can be roughly divided into the groundwater system of Mingshui spring area,the groundwater system of Jinan spring area,and the groundwater system of Jixi.(2)There area unit varied types of open cut foundation support for R1,R2 and R3 lines in Jinan,like bored piles,underground diaphragm walls,ready-made stacked piles,ready-made sq.piles,slope unleash + anchor cables,etc.Among them,bored piles area unit primarily used,followed by underground diaphragm walls.in keeping with the division principle of Jinan stratum,the inspiration pit enclosure structure utilized in every space of open cut foundation pit is totally different.The deformation characteristics of the inspiration pits in several engineering earth science zones divided in Chapter a pair of area unit studied,and therefore the surface settlement distribution patterns of station foundation pits in several earth science zones area unit analyzed,and therefore the relationship between the most surface settlement and excavation depth,the placement and influence vary of the most surface settlement,the placement of the most lateral shift of the enclosure structure,the connection between the most lateral shift of the enclosure structure and therefore the depth,and therefore the relationship between the lateral shift of the enclosure structure and therefore the surface settlement area unit given.The relevant laws area unit given.(3)The principles and steps of the physical element theory are systematically described.The shortcomings of the hierarchical analysis method are improved,the index scale method is adopted,and the evaluation index system for different geological zones in Jinan is established based on the statistical data in Chapter 2 and Chapter 3 from the actual situation in Jinan.Based on the improved hierarchical analysis method,a material element analysis model suitable for Jinan area was constructed.(4)A typical station pit of Jinan rail transit is selected,and the evaluation index system established in Chapter 4 is used to make a comprehensive ranking analysis of each index weight,and the optimal scheme of this pit support is derived by the material element model.Combined with the reliability principle,the scheme is verified by reliability calculation. |
