The drill monitoring is a technique for predicting the risks at face by analyzing the mechanical quantities measured at hydraulic rock drill in the excavation of tunnels or rock mass for underground structures. Since drill monitoring can be conducted on realtime- basis when excavating blast holes or rock bolt holes in tunnel excavation, it enables fast and quantitative prediction and evaluation of tunnel face. Though a number of studies have been conducted on the drilling data, the selection of drilling parameters and numerical quantification of mechanical quantities for the evaluation of the ground characteristics have not been established yet. In this study, drilling tests were conducted with rock specimens to identify drilling parameters and the correlation between the drilling data which was analyzed with the data obtained in the test drilling. The average values of the drilling parameters were calculated using the average values of the sections of the drilling data, and the drilling mechanism was verified by correlation analysis between the drilling parameters.
The drill monitoring which is a survey technique using drilling parameters can improve the work efficiency and safety by predicting and evaluating the state of the ground ahead of tunnel face. This technique measures and analyzes various drilling parameters, including instantaneous advance speed, torque pressure, percussion pressure, feed pressure, rotation speed, and number of percussion, which are measured with hydraulic sensors and data recorder installed on hydraulic rock drill of jumbo drill, during drilling process (Pfister, 1985; Peck and Vynne, 1993; Schunnesson, 1996; Toda corporation, 2005; Mituisumitomo corporation, 2005). The drilling parameters obtained in drill monitoring contain quantitative data of the ground, including weathering, fracturing (Barr, 1984; Scoble and Peck, 1987), hardness (Schunnesson and Sturk, 1997) of rock mass and different rock type boundaries (Schunnesson and Holme, 1997). A number of studies have been conducted to improve the efficiency in tunnel excavation by analyzing the correlation between drilling parameters and rock, rock mass and ground. Kahraman (2000) proposed drillability index which can predict penetration rate from the rock characteristics. Thuro (1997, 2003) proposed the concept of drillability using drilling parameters to classify rocks by the easiness of drilling, and proposed excavatability concept to define the relationship between the destruction work and specific consumption of explosive using drilling rate. In Korea, N. Y. Kim et al. (2001) studied on drilling parameters, however, the studies are at preliminary application step and the drilling data obtaining and analyzing system has not been developed yet. According to the reference survey, the preceding studies on drilling parameters have following problems, though they can provide ground data promptly and quantitatively. In drill monitoring, the reaction of the ground condition to the drilling is not monitored directly but the 1428 mechanical quantities of the hydraulic rock drills are measured.