Study On Structural Characteristics Of Lattice Diaphragm Wall In Sandy Gravel Stratum

Foundation pit engineering is an important field of geotechnical engineering.With the rapid development of urban construction,the requirement for the retaining structure of foundation pit is getting higher and higher,and many new structures have emerged.As one of them,lattice diaphragm wall has been widely used in many foundation pit projects because of its unique geometric structure,large overall stiffness,control of soil deformation behind the wall,no need for supporting system in the pit,and it can be used as a permanent structure.As a new and complex retaining structure,the existing design codes and construction experience of retaining structure can not be directly applied to lattice diaphragm wall.There is no detailed and clear reference on the working behavior of foundation pit excavation,the selection of design parameters on the overall structure and so on.To a certain extent,this kind of retaining structure with excellent performance is limited.Application of structure in practical engineering field.Based on the foundation pit engineering of Xiangyang immersed tube tunnel project,this paper designs the lattice diaphragm wall for the retaining structure of the foundation pit excavation near the sewage treatment plant section,carries out numerical simulation by using finite difference software FLAC3D,and studies the working characteristics of typical lattice diaphragm wall during excavation and the deformation trend when changing different design parameters,and combines the test results during actual construction.The main structural characteristics are obtained.The main contents and conclusions are as follows:(1)Because the anti-sliding stability and anti-overturning stability of enclosure structure cannot be checked in numerical simulation software,it is proved that lattice diaphragm wall can be used as cantilever retaining structure by traditional calculation method,and its moment of inertia and equivalent width are deduced by formula,which provides a theoretical calculation method for checking the safety factor of lattice diaphragm wall.(2)Using FLAC3D software to establish a reasonable numerical calculation model of lattice diaphragm wall,this paper systematically analyzed the wall deformation,soil uplift,soil settlement and horizontal displacement behind the wall,earth pressure distribution and structural moment distribution of lattice diaphragm wall in sandy cobble stratum during excavation as enclosure structure.As a semi-gravity retaining structure,the deformation of lattice diaphragm wall is mainly caused by the translation and inclination of the whole structure.The settlement of soil behind the wall is closely related to the lateral deformation of the structure.The soil and the whole structure in the silo deform synergistically,and the bending moment of the structure is the largest at the junction of the front wall and the partition wall and the middle part of the front wall.(3)The sensitivity of design parameters of lattice diaphragm wall is studied by parameter analysis,including the spacing between front and rear walls,the spacing between diaphragm walls,wall thickness,wall depth,width and depth of soil reinforcement in foundation pit.The influence of design parameters on confining lateral deformation of structure,reducing soil settlement behind walls and optimizing bending moment distribution of structure is discussed.Optimizing structural design parameters to provide reliable and feasible design scheme for practical engineering(4)According to the geological prospecting report and construction conditions of the project,appropriate parameters are selected to design the support system,and reasonable monitoring scheme is laid out.The whole project is modeled and analyzed,and the numerical results are compared with the actual engineering monitoring data.The mechanical properties of lattice diaphragm wall are further understood.