Prediction of Reaming Performance of Vertical Raises Using Rock Properties and Operational Parameters

Abstract

ABSTRACT: Raise Boring Machines (RBMs) as the fast and safe operation of drilling excavation of vertical and/or inclined shafts are used in the mining and construction projects for different purposes. Proper selection and accurate performance prediction of these machines are very important issues affecting the cost estimation and planning of the projects. However, reliable models for predicting performance of these machines have been quite limited. This study aims to develop empirical performance prediction models for vertical reaming operations (unit penetration rate and specific energy parameters) by using physical-mechanical properties of rock samples, operational parameters of pilot hole drilling and reaming. Field performance data of the pilot hole drilling and reaming operations, as well as rock samples, are collected in different raise excavation projects in Turkey. The evaluation indicates that weight on bit of pilot hole drilling with the rotational speed of reaming and static elasticity modulus of the rocks could be used to predict the field specific energy. Consumed reamerhead torque and indirect tensile strength and dynamic elasticity modulus of rocks could be used to predict the unit penetration rate. 1. INTRODUCTION Raise Boring Machine (RBM) has now become the most preferred machine for drilling / excavation of inclined and vertical shafts in mining and tunnelling projects. RBMs excavate a circular hole between two levels of underground or between an underground level and surface without using explosives and provides improved personnel safety over the drill and blast method as well as a significant reduction in labor requirement. However, the capital investment is higher and higher level of operator training is required (Wake 2000). RBM uses a small diameter drill rod, around 230-350 mm, to drill a pilot hole down to the required depth. Once the pilot hole has been drilled, the pilot drill bit is removed and replaced with a large diameter reamerhead. The reamerhead is then pulled back up to the upper level by enlarging the hole diameter. In the pilot drilling, the cuttings (muck) are removed from the hole with the aid of flushing. However, in the reaming stage, the muck falls by gravity to the bottom of the hole in where it is continuously removed.