Field and numerical modelling studies for an efficient placement of roof bolts as breaker line support

Depending upon the site conditions, field studies of roof bolt-based breaker line support (RBBLS) found that its positions need to vary from 0.5 to 2m out-bye side from the goaf edge for a better performance. This variation is done to adjust the extent of spalling/loosening of sides of the surrounding natural supports. As per the studied site conditions of different mechanised depillaring operations, a detailed parametric investigation is conducted on the simulated models to estimate rock load height (RLH) for a given site conditions. Results of the static (elastic) simulation study are used for an estimation length of a bolt in the RBBLS. But the field measurements found that the bolts were subjected to dynamic loading during caving of the roof strata. Accordingly, the support resistance of the RBBLS is estimated considering the dynamic effect of caving, derived from the field measurements. On the basis of these investigations, empirical formulations are attempted among the relevant geo-mining parameters for the design of a RBBLS. •Field studies in mechanised depillaring panels showed that a RBBLS works efficiently under the shadow of stable natural supports.•Rock load height is estimated by numerical modelling for designing RBBLS.•Field validation for the RBBLS design suggested incorporation of dynamic loading due to caving of the roof strata.•An empirical formulation is attempted to design the RBBLS for a given site conditions.