Abstract: To achieve the safe and efficient demolition of reinforced concrete support beams in deep excavations,field vibration monitoring and analysis were conducted for a blasting demolition project.This study systematically revealed the factors influencing the vibration velocity of support beams under drilling and blasting.A predictive model for the peak blasting vibration velocity was derived based on dimensional analysis,considering the cross-section size effect of the support beams.The model’s accuracy was validated using field-measured data.The results indicate that the cross-sectional size of the support beam has a significant amplifying effect on the peak blast vibration velocity.The improved prediction model,which accounts for the cross-section size effect,demonstrates higher accuracy.The relative errors between the predicted and measured peak particle vibration velocities in the tangential,radial,and vertical directions were reduced by 25.33%,18.27%,and 9.22%,respectively,compared to the traditional Sadovski formula.The research results can provide a theoretical basis for the prediction and control of vibration of blasting and demolition of support beams in deep foundation pits.