Optimum operating conditions of a multi-hammer drilling machine assessed using a linear percussion test

To minimize social cost and to avoid existing obstacles (e.g., buildings, buried pipes, rivers, and ocean), cable and electricity tunnels are constructed mainly using trenchless technology. We have developed a new method for micro-tunnel excavation using a multihammer drilling machine and identified the optimum operating conditions of the system. A linear percussion testing system was constructed to acquire rock drilling data. The tests were conducted under various air pressures and RPMs consistent with field conditions. Three classes of rock specimens in terms of strength (i.e., hard, medium, and moderate rock) were tested. The test results yielded the optimum operating conditions of the multi-hammer drilling machine according to rock strength.