Research On The Excavation Advance Of Following Hole In Neighborhood Highway Tunnel

This paper takes a certain tunnel in Chongqing’s Qijiang Development Zone as the research background,and studies the combination of theoretical analysis,data compilation,data access,and numerical simulation of Midas GTS NX finite element software to study the construction of the tunnel after the ultra-small clear road tunnel.The impact of the first two holes was built and numerical analysis was conducted.The effects of five blasting distances and five excavation footages on the vibration velocity and stress of the key linings of the first cavities were discussed and analyzed.Then,the theoretical calculations of the surrounding rock release pressures were compared and analyzed,resulting in similarity in the future.The project provides technical support and engineering experience.The research results mainly include the following points:(1)Both the monitoring data and the simulated vibration velocity cloud map show that the horizontal radial vibration velocity is more than 3 times that of the tangential vibration velocity,and the blasting excavation monitoring data is subjected to regression analysis to obtain the vibration velocity attenuation empirical formula and calculated.The maximum allowable single-segment charge for blasting and determine whether the current charge for the blasting program is too large and guide the tunnel construction.(2)In the case of the same footage,the net distance is between 0.5D and 1D,and the amplitude of the vibration value and the stress value are relatively large.Therefore,in the case of 0.5D or ultra-small clear distance,the frequency of monitoring measurement during construction should be increased.(3)The research results show that in order to prevent the excavation image from being too large,lining cracking occurs first.When the distance is 0.5D,the allowable excavation segment is less than 1m;The maximum excavation length is 1.5m for one-time clearance;The maximum excavation length is 2m for the 1.5d interval;When the clearance is greater than 2D,the excavation is based on the actual geological conditions of the site.Images can exceed 3m.(4)At the same net distance,the distribution of stress at each key position has nothing to do with the excavation footage;the distribution of stress at each key position is mainly concentrated at the frontal side of the explosion,and as the net distance increases,the stress distribution gradually shifts to the backbump side.Arch transition.The proportion of the frontal arched side arched waist decreases from 64% at 0.5D to 40% at 2.5D,and the drop is relatively large at 0.5D to 1D,which is 13%.When the net pitch is increased by 0.5D,the left arched The stress was reduced by 4%,4%,and 3% in sequence;the dorsiflexion side arch was increased from 8% at 0.5D to 21% at 2.5D,and the increase was relatively large at 0.5D to 1D,which was 6%.Each increase of 0.5D net distance,followed by 3%,3%,1%.