A Study On The Distance Effect Of Subway Shield Tunnels With Small-Spacing

With the advancement of the urban subway construction process,the city subway line is increasing.But the shallow underground space of city is limited,shield tunnels with small-spacing has become the inevitable choice of city metro tunnels.At present,the research of tunnels with small-spacing focused on mountain tunnels which net distance is greater than 1 times of the hole diameter,the part of the metro tunnels which net distance is less than 1 times of the hole diameter is less.The latter two tunnels influence each other even more significant compared to the former,structure stress and deformation is more complicated.When the net distance is less than 1 times of the hole diameter,it is necessary to study the interaction law of the two tunnels with different net distance,which can provide important reference value for subway construction.Based on Shen Zhen metro line 7th SunGang~HongHu running shield tunnels with small-spacing engineering,integrated using the methods of model experiment and numerical calculation,studied the following aspects:(1)Through 3 kinds of net distance tunnel model tests of two tunnels overlapped or parallel,the research analyzes the effect of the left line(existing)tunnel by the right line(new)tunnel excavation when under different net distance conditions,include the change of lining displacement,internal force(bending moment and axial force)of the left line(existing)tunnel.(2)By 5 kinds of net distance numerical calculation of two tunnels overlapped or parallel,analyzed the effect of the left line tunnel by the right line tunnel excavation with different spacing.Which include the changes of internal forces and displacement of tunnel lining,and the distribution regularity of surface subsidence and plastic zone of surrounding rock.(3)By comparing with the result of model test and numerical calculation,they mutual support and complement,summarize the influence law of the left line by the right line tunnel excavation with different spacing when the net distance less than 1 times of the hole diameter.In general,when the net distance is less than 1 hole diameter,the effect of right-line tunnel excavation on the left line tunnel will gradually decrease as the net distance increases.The left-line tunnel lining near the right side of the tunnel is significantly affected.Due to the small clearance distance between the two tunnels,the plastic zone of the rock surrounding the tunnels is broken,especially the rock mass between the tunnels.And the plastic zone is connected.The necessary reinforcement for both is the necessary work in the engineering practice.