小净距三洞并行公铁隧道近接施工及爆破振动影响研究

Research on the Influence of Approaching Excavation and Blasting Vibration of Small Interval Three-hole Parallel Highway Tunnels and Railway Tunnels

依托甬舟公路孙家湾1号隧道与甬舟铁路牛皮岭下隧道并行段,通过数值计算,对三洞并行隧道中间铁路隧道先行情况下,公路隧道施工顺序、二衬施作时机及工法步距开展研究,并探究了公路隧道爆破对中间铁路隧道二衬的影响,对孙家湾1号隧道的安全净距及在不同工况下的振速进行研究。主要研究结论为:(1)塑性区集中在开挖范围中下部及公路右线与铁路隧道中夹岩处,中间铁路隧道受公路隧道开挖扰动影响左右拱腰产生较大水平变形;(2)小净距三洞并行隧道中间铁路隧道先行,宜采用公路左线-公路右线的开挖顺序,铁路隧道二衬施作完后再施工公路隧道,采用CD法施工,并设置公路左右线步距为50 m;(3)对不同围岩级别、开挖进尺、工法的9种工况爆破施工对中间铁路隧道二衬影响进行探究,得出各工况下振速传播路径、最大部位、振速数值是否满足要求,并对爆破施工提出针对性意见;(4)Ⅳ级围岩、采用CD法施工,孙家湾1号隧道爆破施工极限安全净距为11.5 m,净距小于11.5 m时建议采用机械开挖。

Relying on the parallel section of the Sunjiawan No.1 Yongzhou Highway Tunnel and the Niupilingxia Yongzhou Railway Tunnel,the construction sequence of the highway tunnel,the construction time of the secondary lining and the construction method with the middle railway tunnel excavated first of the three parallel tunnels are studied and determined through numerical calculation.The impact of highway tunnel blasting on the secondary lining of the middle railway tunnel is explored,and the safety clearance of the Sunjiawan No.1 Tunnel and the vibration speed under different working conditions are studied.Main research conclusions:(1)The plastic zone is concentrated in the middle and lower part of the excavation area and the rock between the right line of the highway and the railway tunnel.The middle railway tunnel produces large horizontal deformation on the left and right arches due to the excavation disturbance of the highway tunnel.(2)With the middle railway tunnel operated first of the small clear distance three-hole parallel tunnels,the excavation sequence of the left line to the right line of the highway should be adopted.The highway tunnel should be constructed after the secondary lining of the railway tunnel is completed.The CD method is used for construction and the step distance of the left and right lines of the highway is set to 50 m.(3)The impact of blasting construction on the secondary lining of middle railway tunnel in nine conditions with different surrounding rock levels,excavation footage and construction methods is explored.The vibration velocity propagation path,the maximum position and whether vibration velocity value meets the requirements under different working conditions are determined,and targeted opinions on blasting construction are put forward.(4)Concerning the surrounding rock of gradeⅣwith CD method,the maximum safety clearance of Sunjiawan No.1 Tunnel blasting construction is 11.5m,and mechanical excavation is recommended when the safety clearance is less than 11.5 m.