Research On The Control Technology Of Small Clear Distance Cross Tunnel Blasting Vibration

Compared with ZhongChuan intercity station and the north marshalling yard in Lanzhou,relying on the diversion adjacent tunnel project of BeiHuan tunnel which is constructingupper pass HongShan ding tunnel which is existing, the thesis carries out a systematic studyon the blasting construction technology and control measures in the small interval tunnel fromthe aspects of the theoretical analysis, the monitoring of blasting vibration and numericalsimulation. In order to ensure the successful construction of BeiHuan tunnel, the study is usedto provide the basic data and technical theory for the design, construction and providing auseful reference for tunnel construction under the other similar geological conditions.The main research contents and outcomes were gained：(1)According to the monitoring data of the blasting vibration and the dynamic strain ofconcrete during the tunnel blasting vibration, the proper safety vibration velocity for theproject control standards is determined based the relationship between the vibration velocityand dynamic strain. Based on the allowable increment of tensile stress of concrete in theadjacent construction, the proper safety vibration velocity is7.0cm/s.(2)According to the blasting safety regulations and the small spacing tunnel constructionresearch data, the monitoring scope of the blasting vibration is on distance intersection±20mby methods of Sadauskas formula. Considering the safety of existing during tunnel blastingvibration, the total synthesis of speed from three directions is treated as the control velocitystandards of blasting vibration. The maximum velocity of the existing tunnel is5.89cm/sduring the blasting construction of the BeiHuan tunnel scope, which is less than the controlvelocity standards.(3)Through literature and field data analysis, the blasting vibration intensity is mainlycontrolled by the geological conditions, the blasting distance, the charge quantity and theblasting conditions (blasting position, free surface conditions).On the basis of Sadauskasformula, the blasting vibration formula which is applicable to the blasting of the existingtunnel is fitted and the cut blasting is treated as the key during the blasting. The cut blastingshould be mainly monitored.(4)After Fourier transform, though the spectrum analysis and frequency distributionanalysis of the blasting vibration wave, the typical tunnel blasting vibration signal spectrumcan be get and the distribution of the main frequency of vibration wave can be determined.Based on the blasting safety regulations, the main vibration frequency as the criterion ofcontrol of blasting vibration should be away from the structure of its frequency in order toavoid the damage caused by the resonance effect. (5)According to the factors which can influence the blasting vibration intensity, theoriginal blasting scheme is adjusted during the cut blasting through small spacing affectedarea. The influence of blasting vibration can be reduce the minimum by modifying the drillingdesign, control the charge quantity, increasing the initiation times, reducing excavationfootage and selection reasonable method of initiation interval of detonator.(6)According to the analysis software-ANSYS, the three-dimensional model wasestablished. Through the numerical simulation, the maximum vibration velocity of theexisting tunnel speed is lower than the velocity control standards during the step cut blasting.The increment of stress and tensile stress of the existing tunnel cross section lining also meetthe requirements of specification. The results show that the lining structure of the existingtunnel is safe and reliable during the blasting.(7)The dynamic response of the existing tunnel was simulated by ANSYS finite elementsoftware during the blasting of before and after the cross section of BeiHuan tunnel. From theaspects of the vibration velocity, stress and the increment of the stress, the maximumvibration of the existing tunnel is less than7cm/s which is the safe vibration velocity and thesafety coefficient of the compressive and tensile stress also meet the safety requirements aswell as the increment of the stress.