Stability Analysis Of Deep Foundation Pit Construction In Soil And Rock Binary Formation

With the development and progress of the society,the construction of the subway has become the mainstream of the current urban infrastructure.The increase in the construction of the subway has brought about the emergence of a large number of deep foundation pit projects.Among them,Dalian,Qingdao and other coastal cities have developed a soft and hard binary deep foundation pit project.Due to the special occurrence and structurality,the geological parameter uncertainty and stability analysis complexity exist.The selection of support parameters and the risk of caverns have become an urgent problem to be solved.With the support of related topics,this paper studies the stability of the deep foundation pit of the soil and rock binary stratum with the deep foundation pit of Qingdao Metro Line 1 and the deep foundation pit of the South Shuttle Station of Dalian Fish Market.The main contents and results are as follows:(1)Combining the Gaussian Process Machine Learning(GP),the Differential Evolution(DE)and the MC model for the non-deterministic problem of the two-layer foundation pit parameters of soil and rock,the inverse analysis of the stratum parameters of the deep and deep foundation pit of soil and rock.Firstly,orthogonal design is carried out to establish a combination scheme of foundation pit stratum parameters,substituting into a three-dimensional numerical model for simulation analysis,and selecting key parameters by means of sensitivity analysis.The Gaussian Process Machine Learning(GP)is used to realize the nonlinear expression of displacement.Finally,the differential evolution algorithm is used to realize the inversion of foundation pit parameters.The deformation of foundation pit retaining structure under different rock-socket depths of the sling pile is analyzed to obtain the optimal embedded Rock depth.(2)Aiming at the deficiencies of the traditional method for the stability analysis of soil and rock binary pits,the strength reduction method and the weight gain method are applied to the deep foundation pit engineering,and the overall stability analysis of the foundation pit is solved by numerical experiments.And analyze the reasons that affect the different safety factors of the two methods.At the same time,the influence of factors such as groundwater and anchorless support on the safety factor is analyzed.(3)Aiming at the optimization target of the dual-base pit support system of soil and rock,this paper establishes a comprehensive evaluation criterion consisting of displacement index and local safety index,and optimizes the supporting parameters of the soil and rock binary pit of the South Bay of Shuttle Fish Bay in Dalian.According to the factors such as the support section coefficient of the foundation pit steel,the number of support roads,the support horizontal spacing,the final steel support position and the steel support prestress,the calculation results are adopted by the field engineering.(4)Aiming at the special problem of the adjacent caverns of coastal soil and rock near the cave,the model is established to analyze the influence of karst caves at different locations on the stability of deep foundation pit construction,and the soil around the foundation pit is analyzed by means of the Zone State Index evaluation index(ZSI).The state of destruction and expansion of the body.The pre-grouting treatment measures were taken to influence the large-scale cavern area to ensure the smooth construction of the foundation pit.At the same time,the influence of different cavern pressure water pressure on the foundation pit excavation was analyzed.