Study On The Influence Zone Of Adjacent Construction Of Newly-built Tunnels And Existing Bridges With Spread Foundation

In recent years,with the rapid development of transportation in China,various tunnels,bridges,roads and other structures are adjacent to each other.Some tunnels inevitably pass next to or below other structures.Adjacent construction of tunnels has become the focus of attention in the field of tunnel engineering.This article summarizes relevant researches on adjacent construction at home and abroad,and adopts the methods of investigation,theoretical analysis and numerical calculation,to discuss the influence of the newly built tunnels on the existing bridges with spread foundation.The main research contents and results are as follows:?1?The achievements of previous research are summarized,and identifying factors that influence the adjacent construction of new tunnel and existing bridges with spread foundation.The concept of"bridge foundation-tunnel"relative scale B/D is proposed,and mechanical models are established.?2?The strength reduction method is introduced to explore the mechanical mechanism and the distribution of safety factor of bridge foundation,single tunnel and adjacent construction.This paper points out the general rule of the safety factors of adjacent construction under the condition of different formation parameters and relative scales:As the tunnel is far away from the bridge foundation,the safety factor gradually increases in 0°direction,and the influence between tunnel and bridge gradually decreases.Finally,the safety factor gradually reached a constant value.In the directions of 30°,60°,and 90°,the safety factor first increases and then decreases with the increase of the distance.Finally,it becomes the instability of tunnel itself.?3?Through the analysis of the overall safety factor and its drop when the width of foundation is 0.9d,0.6d and 0.3d respectively,it can be concluded that the drop of safety factor decreases as the R/D increases in all directions.Finally,the overall safety factor is equal to the safety factor of single tunnel,and the drop also tends to zero.It is pointed out that the larger the relative scale B/D is,the greater the impact will be on the adjacent construction in all directions.?4?This paper gives the influence zoning criterion of adjacent construction,and determines the influence zone under the condition of different ground parameters and widths of foundation,based on the distribution characteristics of the safety factor contour field.It is pointed out that the larger the relative scale B/D is,the larger the influence zone will be,and the influence in vertical direction is greater than that in horizontal direction.Moreover,the contour line with safety factor of 1 shows the form of parabola,which can be expressed by the quadratic polynomial of y=a x²+b.?5?The general expression for the boundary of influence zone under the condition of first ground parameters is obtained:y=f?B/D,x?=[-0.0553?B/D?-0.0988]x²+19.152?B/D?-2.441Moreover,a general partition diagram for adjacent construction of new tunnel and existing bridges with spread foundation is made.For practical engineering,we can simply judge whether the tunnel is in the influence zone by vault coordinates?x₀,y₀?.