研究目的:研究重庆轻轨新郑区间浅埋、上软下硬地层、软弱夹层岩柱等不良条件下小净距隧道掘进和爆破减振技术,保证围岩与支护结构的稳定性、光爆良好效果和地下管线安全.研究结论:(1)洞口回填松软土层浅埋地段采用超前大管棚支护,并对Ⅲ、Ⅳ、Ⅴ、Ⅵ四种围岩段,采用正三台阶、正二台阶预留核心土、正二台阶及全断面开挖方式,配合采用光爆技术,适合浅埋不良地质条件下双隧道净距仅5.8 m情况下小净距隧道修建;(2)小净距隧道爆破中掏槽孔爆破产生的振动强度最大,通过对不同地质段采取预裂光面爆破和预留光爆层爆破两种方法,掏槽眼分别采取五梅花中空直眼掏槽及斜眼掏槽方法,实测地面测点振速1.8 cm/s,相邻洞内边墙衬砌振速11.02 cm/s,爆破振速满足规程要求,且确保了光爆效果,减振爆破技术可行.%Research purposes: The research was done on the driving and damping blast technologies for construction of shallow small clear - distance tunnel of light rail transit in Xinzheng, Chongqing under the favorable geological conditions of soft and hard mixed strata and the weak rock pillar to guarantee the stabilities of the wall rock and supporting structure and the safety of underground pipelines and achieve the good smooth blasting effect.Research conclusions: ( 1 ) The large pipe roof construction was adopted to the shallow area with filling soft soil around the tunnel portal.The positive tri - bench method, the positive bi - bench method with remaining the core soil, the positive bi -bench method and full wall excavation method were used along with smooth blasting respectively to the wall rocks of Grade Ⅲ, Ⅳ, Ⅴ and Ⅵ.These construction technologies were available for construction of the shallow tunnel with clear - distance of less than 5.8 m between two tunnels under favorable geological conditions.(2) The vibration caused by the blasting in the cuthole was big when blasting for small clear- distence tunnel.When the explosion was conducted to the areas of the different geological conditions with two smooth blasting methods (presplitting smooth blasting and remaining the smooth surface layer in advance), and the straight and inclined holing methods were used,the vibration velocity of the ground measured spot was 1.8 cm/s and the vibration velocity of the side wall lining of the adjacent tunnel was 11.02 cm/s.These vibration velocities met the code requirements, obtaning good blasting effect.It showed the damping blast was feasible.
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