| With the increase of car ownership year by year,the problem of parking is becoming more and more prominent,especially in the dense building areas,the problem of parking is becoming more and more obvious.In order to solve the problem of difficult parking,a new type of under-ground parking garage,Dome shaft parking garage,is proposed in this paper.As a new type of underground parking garage,a lot of previous research work is still needed,so it is of great in-novation and significance to study the influence of various factors on land subsidence and to de-termine its reasonable excavation step.On the basis of the existing similar prediction formula of land subsidence,the factors such as underground depth,diameter of three-dimensional parking section,height of three-dimensional parking section,type of support,physical and mechanical properties of strata and so on are com-prehensively considered.The prediction formulas of ground settlement of hemispheres and cyl-inders are deduced respectively,and on this basis,the prediction formulas of ground settlement of domed underground parking garage are obtained.The influence error under different support conditions is corrected by introducing the support reduction coefficient,and the calculation re-sults are more accurate.Through the simulation study of the settlement of the domed underground parking garage,it is determined that the influence on the ground settlement is the least when the concrete support is used in the entry and exit section and the anchor mesh spray support is used in the three-dimensional parking section.The analysis shows that the change of soil layer thickness has the most obvious influence on the land subsidence,followed by the magnitude of the ground load and the diameter of the entry and exit passage,and it is given that the optimal combination of the least influence factors of the land subsidence is A1B4C4D1E1F1G4H1.According to the re-sults of numerical simulation.The curve relationship between the relative land subsidence x and the influencing factor variable y is drawn,and the functional relationship between x and y is fit-ted.After further transformation,the relationship between the influencing factors and the land subsidence is obtained.It has a certain guiding significance for the design of underground park-ing garage.Through the simulation study on the reasonable excavation step of the domed underground parking garage,and the comparative analysis of the ground settlement and the uneven settlement,it can be concluded that the reasonable excavation step under the most unfavorable and optimal conditions is 0.5m and 2.0m respectively.The reasonable excavation steps under the conditions of different soil layer thickness,diameter of entry and exit passage,ground load and ground load position are further determined:when the thickness of soil layer is 15m,20m,25m and 30m,the reasonable excavation steps are 2.0m,2.0m,1.0m and 0.5m,respectively,and when the diame-ters of the entry and exit passage are 5.5m,6.0m,6.5m and 7.0m,the reasonable excavation steps are 2.0m,2.0m,1.0m and 0.5m,respectively.When the ground load is 1.0×105Pa,1.5× 105Pa,2.0× 105Pa and 2.5 × 105Pa.The reasonable excavation steps are 2.0m,1.5m,1.0m and 0.5m,re-spectively.When the ground load position(that is,the distance to the center of the underground parking garage)is 20m,30m,32m and 39m,the reasonable excavation step distance is 2.0m,1.5m,1.0m and 0.5m,respectively.On this basis,the reasonable excavation step under different conditions can be conservatively estimated,which provides a theoretical basis for the construc-tion of the access section of the vault underground parking garage. |
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