Cracking and Construction Blasting

Studies of blast-induced cracking of residential structures have concluded that peak particle velocity is the best index of damage. These investigations are compared to show how differences in target structures, crack location, wall covering, recorded motion, gage location and shot characteristics affect thresholds of cracking. Some 1,400 time histories of construction and surface coal mining blasts in Illinois are compared to differentiate typical mining and construction blasts. The difference between free and restrained response is investigated, and an analytical model for each type of response is presented and developed with experimental data. These models are employed to show the importance of the frequency of the excitation motions, local strains and material properties.