Analysis Of Blasting Vibration Response And Research Of Reinforcement For Small Spacing Tunnel

The exploitation and the utilization of underground sPace have become more andmore important with the rapid development of China’s national economy and theincrease of the volume of traffic. Meanwhile, an increasing number of road works areconstructed or will be constructed. Therefore, traffic engineering and geotechnicalengineering are thriving.Constructing new tunnels beside the existing tunnels can improve the caPacity oftransport and reduce the investment. However, it can result in problems that the distancebetween new tunnels and existing tunnels are relatively small due to the influence of thegeologic conditions. The blasting stress wave that generated by the double-trackblasting excavation have an affect on the safety of the structure and operation of theexisting tunnels. It has realistic significance to the construction of transportation and theutilization of underground sPace in China that how to ensure the safe operation ofexisting tunnels and the excavation of new tunnels.This Paper bases on XiaoPiaogou’s tunnel works, and targets the effects of newtunnel’s blasting vibration response on the lining of the existing tunnel. UsingANSYS/LS-DYNA finite element methods software and the specific conditions ofXiaoPiaogou’s tunnels, mainly research the following7aspects:1．To determine the rational arrangement of monitoring points in existing tunnelsduring blast working of the newly built tunnels. The numerical analysis indicates thatthe Particle vibration velocity on the blasting side of the existing tunnel is much largerthan the back blasting side, the maximum velocity appears at the key node3of theexisting line blasting side (1.2m height from the ground), therefore the monitoringpoints should be arranged at the position which is1.2m height from the ground. 2．To analyze the iMPact on existing tunnel’s generated by the blasting vibrationresponse of new tunnels under different12conditions, then determine the rationalamount of explosive charges in different sPace, and thus guide blast working of theXi-kang Er-xian Xiao-piaogou tunnels. To control blasting vibration response of theexisting line and to ensure the safety of the operating of the existing tunnels.3．The analysis of the measured data and numerical simulation results indicates thatwith the decrease of the distance L between new tunnels and existing tunnels, thevariation trend of measured peak Particle vibration velocity of the existing lines and ofthe numerical analysis results is basically consistent. The peak Particle vibrationvelocity is gradually increasing with the continuously reduce of the distance L undersame blasting quantity; and the smaller the distance L is, the greater the increase is.4．The effects of clear distance between the two tunnels and of the blasting quantityon the blasting vibration response of the existing tunnel is great during the blastworking of new tunnels which the clear distance between existing tunnels is relativelysmall. Clear sPacing between the two tunnels can not be changed, therefore, how tocontrol blasting quantity effectively in the construction of the new tunnels is the key toreduce the blasting vibration response of the existing tunnel and ensure its safeoperation.5．Rational conclusions of numerical experiments can provide a theoreticalreference for the choice of the new tunnels’ blasting program, especially for theoptimization of blasting quantity, during the blast working of new tunnels which theclear distance between existing tunnels is relatively small. It also can be used to guidethe blast work of a new tunnel under the small clear sPace conditions, it makes up thedisadvantage of poor predictability and lag of the monitoring methods used inmeasuring the blasting vibration intensity of in realistic engineering, and achieves activecontrol of the detriment of blasting vibration effects.6．Numerical simulation analysis shows that the vibration velocity, the maximalprinciPal tensile stress and maximal compressive stress become larger gradually withthe decrease of the distance of the steel-arch’s reinforcement sPacing, or in other words,with the increasing of the modulus of elasticity of the existing tunnel lining according toequivalent calculated. 7．Steel arch’s equivalent numerical simulation analysis shows that, when theelastic modulus of the lining of the existing tunnel is less than a certain value,strengthening the steel arch tunnel can improve the effect of antiknock, and when theexisting tunnel’s elastic modulus is larger than a certain value, then strengthening thesteel arch contribute little to the antiknock effect, and in some conditions, thedisplacement even increase.