Predicting Performance of Raise Boring Machines Using Empirical Models

Abstract

Raise boring machines are used for excavation of shafts and other vertical structures in mining and civil engineering fields for material, human transportation and ventilation purposes. 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 to the desired depth, a reamer is attached to the drill rod. The reamer is then pulled back up to the upper level, creating a round shape. This continues operation provides a faster advance rate than other methods. The flexibility in different angles and diameters is a great advantage compared to drill and blast excavation method. RBM creates a shaft with smooth walls which usually does not require lining in an appropriate geology. The hole is more stable than a drilled and blasted method and has better air flow, making it ideal for ventilation shafts. The cutting performance of raise bore machine is mainly dependent on geological features of rock, specification and design of the machine, and operational parameters such as force on cutter and rotary speed. Few studies have been published in the literature related to performance prediction of the raise boring machines. Morris (1969) developed a semi-empirical method of predicting the boring rate and cutter life. In his method button penetration index with the other factors was used to predict the machine performance. Lightfoot (1970) founded a good correlation between the performance of raise drill (Model 480) and the result of Morris (1969). Seiler (1972) developed a boreability index by pressing hydraulically a sphero-conical tungsten carbide insert into a flat rock surface. Then by dividing the load to created depth a boreability index was calculated. Calder (1972) stated the empirical model to predict boring rate from drilling studies. His rotary drilling model relates boring rate to uniaxial compressive strength of the rock, thrust force and hole diameter. Pigott (1985) stated some suggestions for faster and cheaper drilling of shafts in soft to medium strength formations. Nishimatsu et al. (1987) tried to improve the boring capacity of the blind raise boring machine using theoretical concepts. Bilgin (1989) and Bilgin et al. (2014) stated that, penetration index obtained from indentation tests could be used to estimate the RBM performance. Elgenklow (2003) investigated Robbins 34RH and 53RH raise bore machine performance at El Teniente mine in Chile. In this investigation utilization time was obtained 29.8 and 40.3 % for 34RH and 53RH machine, respectively. In the present study, borehole samples obtained from Eti Copper Kure Asikoy underground mine were first tested to define some of the basic physical and mechanical properties, and then cutting experiments using a linear cutting test rigs with chisel, conical, and disc type cutting tools were realized with two different cutting depths at unrelieved cutting mode. The linear cutting tests were performed to find out the cuttability properties of samples and to define the cutting performances of different cutters. The results of laboratory and field studies were used to develop empirical models for predicting penetration rates of raise boring machine. Two empirical models are suggested and verified. & Aydin Shaterpour-Mamaghani mamaghani@itu.edu.tr