Study on the Reasonable Spacing of the Excavation Face of Shallow-buried and Super-closed Upper and Lower Overlapped Tunnels
Research purposes:The upper and lower double layered tunnels of Jigongzui in Chongqing are closely overlapped in parallel,causing mutual disturbance during the construction.In view of the disturbance effect of the construction of the upper tunnel on the lower tunnel,the numerical simulation method was adopted to study the reasonable distance between the excavation surfaces of the upper and lower tunnels,so as to reduce the mutual influence of the close tunnel construction,and achieve the purpose of shortening the total construction period of the tunnel.Research conclusions:(1)Along the longitudinal plane of the tunnel,when the horizontal clear distance between the excavation surface of the upper and lower tunnels is 0 span,the upper tunnel has the greatest disturbance to the lower tunnel,which is the most unfavorable clear distance.(2)When the distance between the excavation surfaces of the two tunnels is more than 50 m,with the increase of the distance,the disturbance of the upper tunnel to the lower tunnel is significantly reduced.(3)When the distance between the excavation faces of the two tunnels is within 50 m,with the change of the distance,the disturbance effect of the upper tunnel on the lower tunnel does not change significantly.(4)When the distance between the upper and lower tunnel excavation faces is 125 to 150 meters,the vertical displacement value of the lower tunnel is stable at about 13 mm.(5)The above research results can provide a reference for the design and construction of similar projects in the future.
tunnel engineeringsurrounding rock disturbancedeformation reinforcementnumerical simulation
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