Study Of The Zones Influenced By The Construction Of Twin Parallel Tunnels With Small Spacing

This paper mainly had analyzed the impact of the construction of two small spacing parallel tunnels.Comparison and selection of criteria for judging the influence of two tunnels on parallel adjacent construction was obtained.Based on this criterion,The safety coefficient contour obtained by the strength reduction method was used to establish the influence area of the two spacing parallel tunnels.Based on the strength reduction method,using FLAC3 D finite difference software to establish numerical analysis models.Through the study,the basic conclusions were as follows:1.Studied on the stability of tunnel excavation under different buried depths: The safety factor of tunnel was decreased with the increase of buried depth in the calculated conditions.The decrease was reduced as the depth of the buried depth increased.“Small amplitude depth”(The slope of the curve is less than-1%)of the tunnel with small hole diameter was less than the tunnel with large diameter.2.Studied on the stability of tunnel excavation under different tunnel distance: When the two tunnel were juxtaposed,the safety factor of the tunnel increased with the increase of the tunnel distance.When the tunnel distance reached a certain value,the safety factor of the tunnel stoped increases,and tended to the safety factor of a single tunnel.With the increase of tunnel distance,the safety factor of the two tunnels were increasing when the new-built was above the existing tunnel.While the new-built was under the existing tunnel,the safety factor of the two tunnel increased first and then decreased with the increase of tunnel distance.3.The influence of the relative scale of the two tunnels on the stability of the tunnel was analyzed:When the buried depth of the existing tunnel was deep,the new-built was above the existing tunnel,the safety coefficient of tunnel was the largest when the relative scale was =1.00,the second was 0.74,and the minimum was 1.35.When the two tunnel were juxtaposed,the safety factor of the tunnel was maximal when the relative scale was 1.00,the relative scales that were 0.74 and 1.35 were the lowest and the two were basically equal.While the new-built was under the existing tunnel,the safety coefficient of tunnel was the largest when the relative scale was 1.00,the second was 1.35,and the minimum was 0.74.When the buried depth of the existing tunnel was shallow,the new-built was above the existing tunnel,the safety coefficient of tunnel was the largest when the relative scale was 0.74,the second was 1.00,and the minimum was 1.35.When the two tunnel were juxtaposed,the safety factor of the tunnel was maximal when the relative scale was 1.00,the relative scales that were 0.74 and 1.35 were the lowest and the two were basically equal.While the new-built was under the existing tunnel,the safety coefficient of tunnel was the largest when the relative scale was 1.00,the second was 1.35,and the minimum was 0.74.4.The tunnel safety factor curve was fitted by MATLAB and the tunnel location of safety factor =1 was solved.Then MATLAB was applied to curve fitting of the positions of these locations.A subsection unified diagram for the near connection of three kinds of relative scales(beta =1.35,1,0.74)in the middle layer of the stratum,which was suitable for the range of calculation working conditions,was obtained.And getting a subsection unified diagram for two kinds of depths(H=45m?25m)in the middle layer of the stratum,which was suitable for the range of calculation working conditions.And getting another subsection unified diagram for three kinds of relative scales(beta =1.35,1,0.74)in the different layer of the stratum.