Optimization Analysis of Treatment Scheme for Metro Tunnel Base Waterlogged Collapsible Loess Formation

Abstract

Objective To study the optimization measures for treating waterlogged collapsible loess stratum, it is necessary to investigate the deformation characteristics of tunnel structures after loess collapse by waterlogging. Method The foundation treatment for the waterlogged collapsible loess tunnels is introduced. Taking a shield metro tunnel crossing through waterlogged collapsible loess stratum as example, the method of three-axis mixing pile is adopted as the foundation treatment method. By establishing a numerical calculation model using MIDAS GTS software， the influence of waterlogged deformation of loess foundation on the vertical displacement of various metro tunnel structure parts and the internal force of lining structure is analyzed under different treatment depths and treatment widths. The treatment scheme is optimized based on the changing trends of tunnel parts vertical displacement and lining structure internal force, the construction economy and relevant requirements. Under conditions of three treatment widths and seven treatment depths, variation laws of vertical displacement, bending moment, and principal stress at the tunnel arch waist, vault, and invert are analyzed for the most suitable treatment recommendation. Result & Conclusion The greater the treatment depth, the smaller the vertical displacement of tunnel structure parts and the larger the lining structure internal force; the larger the treatment width, the smaller the vertical displacement and the internal force mentioned above. In this case study engineering, the optimal treatment depth is 7 m, and the optimal treatment width is 16 m.

Keywords

• metro
• tunnel
• waterlogged collapsible loess stratum
• treatment scheme