Assessment of Effects of Quarry Blasting on Nearby Residential Structures in Ogun State

Quarry blasting activities near residential communities in Ogun State, South West Nigeria, generate ground vibrations and airblast overpressure that can cause structural damage and community nuisance. This study assesses the effects of quarry blasting operations on residential structures near two quarry sites in Sagamu and Ijebu-Ode LGAs. Ground vibration measurements using triaxial geophones were recorded at 30, 60, 100, and 200 metre distances from blast sites during 20 production blasts at each quarry. Peak Particle Velocity and air overpressure values were recorded and compared against the USBM RI 8507 damage criteria for residential structures. Structural inspection of 45 buildings within 200 metres of quarry boundaries was conducted before and after six months of monitoring. Crack monitoring pins were installed in six buildings for precise settlement and movement tracking. Results indicate that PPV values at 30 metres exceed the 12.7 mm/s residential structure guideline in 65 percent of recorded blasts. At 100 metres, 23 percent of blasts exceed guidelines. New hairline cracks were recorded in 4 buildings within 60 metres of blast sites over the monitoring period. The study concludes that current blasting practices at both quarries exceed safe vibration limits for residential structures and recommends revised blast design with reduced instantaneous charge weights and adoption of electronic detonators for improved timing precision.

Keywords: quarry blasting, ground vibration, residential structures, Ogun State, blast damage criteria