Plastic limit bearing calculation of blasting-roof in deep hole mining and its applications

In order to solve the problem that blasting-roof thickness was hard to determine in deep hole mining, the plastic bearing calculation method of blasting-roof was proposed. Aim at typical boundary conditions of blasting-roof, mechanical analysis model of plastic bearing was built. The external work and internal work of blasting-roof under plastic limit state were calculated. Based on virtual work principle, the limit bearing formulas of blasting-roof under various boundary conditions were derived. Taking a VCR stope as the object, the safe blasting-roof thickness was determined as 6m by derived formula (considering safety coefficient). Numerical model of stope was constructed by Surpac-Flac3D technique, while blasting-roof stability was simulated under different thickness. The variation of simulated indexes (stress, plastic zone volume) prove that theoretical calculation is reliable. The plastic bearing calculation method can provide a new way for determining blasting-roof thickness in deep hole mining.