Study On Deformation Characteristics And Design Parameters Of Deep Foundation Pit Supported By SMW Piles In Nansha Soft Soil

In the coastal areas of China,deep soft soil is widely distributed,urban construction is active,and there are many deep and large foundation pits,so the design requirements of foundation pits are constantly improving.SMW construction method pile has been widely used and achieved good results because of its advantages of safety,stability,green and low cost.However,the stability of SMW construction method pile supporting structure is affected by the physical and mechanical properties of soft soil,the engineering characteristics of cement soil and the deformation characteristics of construction method pile.Therefore,the above research can provide theoretical reference for the design of SMW construction method pile.Based on Guangzhou Nansha Qingsheng complex project,this paper studies the deformation characteristics and design parameters of SMW piles in soft soil areas by means of indoor,in-situ test,numerical simulation,field monitoring and theoretical analysis.The main research work is as follows:(1)The basic physical properties of Nansha soft soil,such as liquid plastic limit,organic matter and particle composition,are obtained through laboratory soil tests;Through in-situ mechanical test,the range and variation law of strength,deformation and state parameters of soft soil are obtained,and the linear relationship between parameters,depth and parameters is established.(2)Through the mix proportion test of cement soil and the grip strength test of cement soil and profile steel,the variation range and law of unconfined compressive strength,flexural strength,shear strength,deformation parameters,permeability parameters and grip strength of cement soil are analyzed.The results show that the performance of cement soil obtained by 95% cement +5% lime is better.The strength and grip strength of cement soil are proportional to the content and age,and inversely proportional to the water cement ratio,There is an obvious linear relationship between different parameters.(3)PLAXIS 3D is used to carry out three-dimensional numerical analysis of deformation of deep foundation pit supported by SMW method piles in Nansha deep soft soil,revealing the space-time development law of stress deformation of the support structure: the deformation of the support structure is fast in the initial stage of excavation,and gradually stable in the later stage.The deformation at the inner corner of the foundation pit is relatively small,while the deformation in the middle is relatively large.(4)Based on the measured and simulated results of deep foundation pit deformation,a BP neural network prediction model for the proportional coefficient m of horizontal resistance coefficient is established.The m value suitable for different soft soil layers in Nansha is obtained,and its applicability is verified in combination with practical projects.