Evaluation of the unconfined compressive strength of rocks using nail guns

•An equation relating the variables of gasnailers to UCS was established for rocks.•The established relationship is applicable to any commercial gasnailers.•The reliability and capacity of the gasnailers are very high to estimate the UCS of rocks.•Gasnailers should be used in mainly in situ rock strength evaluations.

The penetration depth is one of the major index parameters for indirect determination of the unconfined compressive strength (UCS) of rock. That is, the weaker the rock, the deeper the nail penetration should be, and vice versa. However, the penetration depth depends on the strength of material, the impact energy and nail diameters of nail guns. In order for an empirical equation relating the penetration depth to the UCS to be widely used, the equation should be related to all varieties of gasnailers.The scope of this investigation is to develop an empirical equation relating the nail penetration depth (h) obtained through nail guns of different energy levels (e) and nail diameters (d) to UCS. In this context, a series of gasnailers with different energy levels and nail diameters were performed on 65 rock blocks. The results of laboratory conducted unconfined compressive test were correlated with nail penetration depth (h), nail gun energy (e) and nail diameter (d) and an empirical equation was established using multiple regression analysis. It covers a relatively wide range of energy levels and nail diameters for commercial gasnailers. The proposed equation can be used to estimate the UCS of intact rocks, thus providing the technical features needed for using commercial gasnailers.