Study On Rock Mass And Structural Vibrations Caused By Tunnel Blasting Excavation

Tunnel construction is an important part of high-speed railway and urban underground traffic.Tunnel blasting is one of the main methods for tunnel construction.In the process of tunnel blasting,blasting vibration has an impact on the surrounding environment.In order to reduce the vibration effect of blasting,a lot of researchers have done a lot of research on the prediction of blasting vibration velocity,and the extended blasting vibration prediction formula containing many factors is obtained.However,a large number of field blasting vibration tests show that there are many factors affecting the vibration propagation because of the complicated blasting environment in the tunnel,and the existing vibration prediction formulas have the limitations of low accuracy and small application range.In addition,the blasting sensitive factors such as surface buildings,underground structures and unstable surrounding rock in tunnel holes are widely used,and the vibration characteristics of these surface buildings,underground structures and surrounding rock in the blasting vibration field are different.Thus higher requirements for the accuracy of blasting vibration control are put forward.In this paper,a series of blasting tests have been carried out through the water diversion project of Qiandao Lake and the Zizhi city traffic tunnel project in Hangzhou,and the following research contents have been carried out:1.The blasting vibration velocity and acceleration of the top of pile foundation and the superstructure of pile foundation are monitored through the shaft blasting test.The different vibration characteristics of the pile top,the wall foot of the retaining wall and the top of the wall are analyzed in the time and frequency domain,and the vibration damping effect is simulated by the numerical model.The research shows that the vibration of the pile foundation is mainly vertical vibration when the shaft blasting is blasting,the vibration speed of the cutting dynamite is the largest,the secondary hole is auxiliary and the blasting vibration of the surrounding hole is the smallest.When adjusting the loading quantity,the auxiliary charge quantity and the surrounding charge to control the pile foundation blasting vibration,it should be reduced as much as possible under the premise of ensuring the cutting effect.When the wall height increases and the lateral stiffness decreases,the main frequency of the vibration will gradually decrease,and the main frequency of the vibration should be controlled at a higher level to avoid the structural resonance.The peak vibration velocity of the wall structure is generated by the composite wave superimposed by the vibration waves of the surrounding holes and auxiliary holes,and the total explosive charge of the blasting structure should be reduced.With the increase of scaled distance,the vibration velocity of pile top and wall decays rapidly,and the wall top has vibration amplification effect,and the vibration speed maintains at a higher level.2.By fitting the measured data,the fitting formulas of blasting vibration speed,blasting vibration acceleration and blasting vibration main frequency with charge amount and detonating distance are obtained,and the corresponding site coefficient and attenuation coefficient of wall measuring point,wall foot measuring point,pile top measuring point,ground measuring point and hole measuring point are obtained.The probability of the main frequency of blasting vibration under different site conditions is calculated.The study shows that the main frequency of the ground surface vibration is lower than 100Hz,the main frequency of the vibration in the tunnel is generally higher than that of the 200Hz,and the main frequency distribution of the blasting vibration of the surface structures,such as the top of the pile,the foot of the wall and the top of the wall,is more dispersed.3.The detailed numerical model of blasting vibration analysis and the numerical model of blasting far field vibration analysis are established to analyze the propagation and attenuation laws of the vibration waves in the near and far fields of the tunnel blasting.A numerical analysis model for tunnel internal vibration are established to analyze the characteristic of blasting vibration in tunnel vault and the side wall and the bottom.The vibration model of rock mass with fault geological structure is established,and the influence of the elastic modulus and fault width of the geological fault on the vibration wave propagation and surface vibration in the surrounding rock is analyzed.