Damage Characteristics of Reinforced Concrete Components in Near-field of Blast Holes under Drilling and Blasting Conditions

Revealing the failure mechanisms of reinforced concrete beams and columns under drilling and blasting conditions is essential for achieving precise blasting demolition design and accurate assessment of blasting effects. Based on an actual deep foundation pit support beam blasting demolition project, this research investigated the dynamic strain characteristics of the hole wall, near-field zone, and the mid-to-far zones under single-hole blasting conditions through field blasting tests and strain measurements. Through explosion dynamics theory, the study calculated borehole wall pressure, damage factors, and damage zoning characteristics. Results demonstrate that under combined blast stress waves and quasi-static gas effects, reinforced concrete support beams exhibit first compression and then pull′ strain characteristics in borehole walls and near-field concrete, with measured strain curves closely aligning with numerical simulation results at both tensile and compressive peaks. The damage distribution in reinforced concrete beams subjected to blasting exhibited a nonlinear attenuation pattern, characterized by rapid decay in the near-field region and gradual reduction to zero in the far-field region. Both numerical simulations and theoretical calculations demonstrated good agreement in the extent of the crushing and fracture zones, with approximately 10% absolute deviation between the two methods. The theoretical and numerical models developed in this study effectively analyze blast-induced damage zoning, with findings offering valuable references for assessing damage characteristics and affected areas in reinforced concrete components during demolition blasting.