Performance characteristics of a small scale rotary boring machine instrumented with large drag picks

Abstract

Performance characteristics of a small scale rotary boring machine instrumented with six very large drag picks in six sedimentary rock types are reported. Performance trends were in reasonable agreement with those obtained from previous studies on tunnel boring machines (TBM) and rotary diamond drilling equipment. The performance of the rotary boring machine was constrained by the centre and gauge cutters. Poorly designed centre and gauge cutters attract disproportionately high tool forces and specific energy requirements. Bulk density and uniaxial compressive strength (UCS) correlated highly with penetration rates in the six rock types tested. UCS is the most widely used parameter for predicting the performance of TBMs and drilling rigs; however, it may not be the most significant rock property available for predicting drillability in soft-medium strength rock types. Diamond and percussion drilling studies were undertaken in the same rocks types and confirmed previous suggestions that it might be possible to predict the requirements and performance of a TBM from the behaviour of a drilling rig during a site investigation.