Sand Gallery Support Design And Numerical Simulation Using FLAC3D

With the advancement of technology,various forms of support have emerged in the field of foundation pit engineering.However,the theoretical development of foundation pit engineering lags behind practical engineering applications.Relying solely on practical application experience cannot meet the challenges brought by the rapid development of foundation pits in terms of difficulty,depth,and scale.Common foundation pit engineering types usually have excavation depths less than the long or short sides of the foundation pit,and the selection of supporting forms for foundation pits with excavation depths far greater than the long or short sides is limited.Based on previous research and practical experience in an abandoned production sand gallery detection well project,this article proposes the use of a support-type retaining structure for protection and explores its effectiveness.After researching the theory of foundation pit support and considering the engineering situation,the author proposed a support scheme of 29m-long Larsen steel sheet piles with six steel pipe supports to meet safety and engineering needs.The stability of the foundation pit was verified by using Lizheng deep excavation software for preliminary design of the support structure.FLAC3 D finite difference software was then used to simulate the entire process of foundation excavation and support.Finally,the results from both Lizheng deep excavation software and FLAC3 D were analyzed and summarized to further analyze the deformation of the soil-steel sheet pile and changes in supporting axial forces.The following conclusions can be drawn from the above study: In the existing theory of excavation support,the equivalent beam method yields results that are too large and cannot reflect the changes in support axial force caused by excavation,nor can it calculate the deformation of the supporting structure;the horizontal displacement of steel sheet piles exhibits a combination of cantilever and parabolic forms,with the maximum pile top displacement occurring at the initial stage of excavation.As excavation proceeds,the maximum displacement occurs at the excavation face and when excavated to the base,the maximum displacement occurs at 0.9 times the length of the pile;The vertical displacement of the soil is closely related to the deformation of the steel sheet pile.When the deformation of the steel sheet pile is a combination of cantilever and parabolic forms,the surface settlement form is mostly parabolic,with the maximum settlement at the pile back and decreasing as the distance from the excavation face increases;as the excavation depth increases,the X-direction displacement of the soil also increases,reaching a peak value when excavated to the base;the support axial force near the excavation face is the largest,with larger values closer to the excavation face.The trends in the calculation results of the two software packages are similar,with only numerical differences,so both results should be considered in designing excavation support along with local experience.