Techique Of Deformation Control Of Deep Excavation Sharing Structural Wall With A Substructure

With the continuous development of underground space and the complexity of the environment in which the project is located,the excavation of the deep foundation pit excavation and slope protection and safety protection work are facing great challenges.When a new foundation pit and surrounding the existing project wall,that part of the existing underground structure as the foundation pit,it is meaningful for the settlement control and protection to the deformation of the existing wall construction,improper control will lead to cracks or collapse and other accidents,in order to ensure both the excavation and the safety of the structure,it is necessary to carry out in the complex environment and existing research control construction technology of deep foundation pit deformation of underground structures is the wall.Based on the case of the Anxin deep foundation pit in Shenzhen area,this study clarified the engineering characteristics and difficulties of the foundation pit.The layout of the struts is optimized and control measures to ensure the safe construction of the project are proposed.The specific research contents are as follows.(1)The site conditions and surrounding environment and other factors of the project are analyzed comprehensively.The characteristics and difficulties of the deep foundation pit engineering are clarified,which are the large excavation depth,the high deformation control requirement,the deformation control of the structural wall shared by the foundation pit and the underground structure and the interactions between the foundation pit and underground structure.(2)The support scheme of annular internal support combined with local reinforcement is proposed based on the overall consideration of deformation control and excavation efficiency.The finite difference method is used to simulate the construction process of the deep foundation pit in Shenzhen.The deformation characteristics and environmental effects of the deep foundation pit construction in Shenzhen are obtained.Moreover,the construction scheme is optimized.The results show that the optimal annular support and support scheme is the most suitable support scheme for the Anxing foundation pit.(3)The reinforcement measures such as reinforcing bar connection are proposed for connection between the new struts and old substructures of common wall.Moreover,the deformation control measures such as deep grouting curtain and additional recharge wells are proposed to protect the surrounding pipelines and metro and other infrastructures.(4)The safety of the pit during construction is ensured through in-site monitoring.The monitoring results show that the deformation of each monitoring point is relatively small.The wall deformation of the south bank of China CITIC Bank is well controlled.All the measured data are in the allowable range and the supporting structure of the foundation pit is in a steady state.The monitoring points of shield tunnels have some individual points exceeding 3mm or even 4mm.However,most of them are in the range of about 2mm.The impact of the tunnels is insignificant and the subway lines are in a relatively safe state.