Studies On Construction Stability Of Four-line Large Span And Small Spacing Tunnel

This paper is based on the tunnel engineering of the back-turning line of Santunbei Station of Urumqi Metro line 1.By means of numerical simulation and monitoring measurement,the deformation and stress characteristics of surrounding rock and structure under different mid-partition wall support schemes are analyzed,the mid-partition wall support scheme of the triple-arch tunnel is optimized,and the stress and deformation characteristics of the surrounding rock and supporting structure in each characteristic construction stage of the triple-arch tunnel are defined.By comparing and analyzing the effect of different working face distances of side tunnel with small spacing,the construction scheme of small spacing tunnel is optimized,and the stress and deformation characteristics of surrounding rock and supporting structure in each construction stage of small spacing tunnel are defined.Based on the conclusion of numerical simulation analysis,the different construction schemes of connecting section triple arch tunnel and small spacing tunnel are analyzed.The main research contents of the thesis are as follows:(1)In view of the stress and construction safety of the partition wall supporting structure of the triple-arch tunnel,the mixed support scheme of the straight wall and curved wall partitions of the triple-arch tunnel section is optimized as a single-straight wall support scheme.Comparing the stress and deformation of surrounding rock and supporting structure during the construction of two kinds of partition wall support schemes,it is concluded that the single-straight wall partition support scheme is better for the three-arch tunnel.By analyzing the deformation characteristics of surrounding rock,tunnel initial support structure and middle partition wall structure,as well as the stress characteristics of partition wall and initial support during the construction process of optimized straight-wall support scheme,the deformation and stress dangerous points of tunnel support structure in each construction stage are determined,which has certain guiding significance for the construction and monitoring of the Triple-arch tunnel.(2)Aiming at the problem of working face spacing in side tunnel construction with small spacing,the deformation and stress characteristics of surrounding rocks and supporting structures in six different working face spacing construction processes are compared and studied.It is proposed that when the working face spacing of side tunnel is 5 m,the construction scheme with small spacing is optimal.When the spacing of side tunnel working face is 5 m,the stress and deformation characteristics of each stage structure and surrounding rock during the construction of small spacing tunnel are analyzed.The deformation,stress variation trend and peak position of support structure in each construction stage are obtained,and the construction and monitoring key points of each stage of small spacing tunnel are defined.(3)Aiming at the influence of different construction sequence of connecting section on the stress,deformation of the tunnel support structure and surface deformation,after the temporary passage construction of the connecting section is completed,four schemes of priority construction of the Triple-arch tunnel section,priority construction of the small-spacing tunnel section,simultaneous construction of small-spacing tunnel section and Triple-arch tunnel section on the same side and simultaneous construction on the opposite side are compared and analyzedThe conclusion was drawn that the connection section adopts the priority construction of the triple-arch tunnel section.(4)Aiming at the displacement deformation of surface pavement and supporting structure in the back-turning section of Santunbei Station of Urumqi Metro Line 1,based on the simulation results and relevant codes,monitoring points of settlement are laid on site,and the crown displacement law of tunnel support structure and surface displacement are obtained.The field test data and numerical simulation results of arch roof deformation of supporting structure and surface deformation in the back-turning section of Santunbei Station are compared and analyzed.The conclusion that the numerical simulation results of triple arch tunnel and small spacing tunnel are reliable is obtained.