Acta Montanistica Slovaca (Sep 2000)
Monitoring of drilling process with the application of acoustic signal
Abstract
Monitoring of rock disintegration process at drilling, scanning of input quantities: thrust F, revolution n and the course of some output quantities: the drilling rate v and the power input P are needed for the control of this process. We can calculate the specific volume work of rock disintegration w and ϕ - quotient of drilling rate v and the specific volume work of disintegration w from the presented quantities.Works on an expertimental stand showed that the correlation relationships between the input and output quantities can be found by scanning the accompanying sound of the drilling proces.Research of the rock disintegration with small-diameter diamond drill tools and different rock types is done at the Institute of Geotechnics. The aim of this research is the possibility of monitoring and controlling the rock disintegration process with the application of acoustic signal. The acoustic vibrations accompanying the drilling process are recorded by a microphone placed in a defined position in the acoustic space. The drilling device (drilling stand), the drilling tool and the rock are the source of sound. Two basic sound states exist in the drilling stand research : the noise at no-load running and the noise at the rotary drilling of rock. Suitable quantities for optimizing the rock disintegration process are searched by the study of the acoustic signal. The dominant frequencies that characterize the disintegration process for the given rock and tool are searched by the analysis of the acoustic signal. The analysis of dominant frequencies indicates the possibility of determining an optimal regime for the maximal drilling rate. Extreme of the specific disintegration energy is determinated by the dispersion of the dominant frequency.The scanned acoustic signal is processed by the Fourier transformation. The Fourier transformation facilitates the distribution of the general non-harmonic periodic process into harmonic components. The harmonic components can be used for the characterization of the rock disintegration process. The components of the acoustic signal by the classical monitoring and scanning of the acoustic signal can be found and specified, characterizing satisfactorily the disintegration process. The specification of the new quantities in the dependence on the thrust F and revolution n, derived from the acoustic signal by the Fourier transformation (as they enable the control of the rock disintegration process at drilling without the classical monitoring, i.e. without the scanning of thrust F and revolution n) is the aim of the research in the presence.The samples of andesite, granite, limestone and sandstone were drilled by the impregnated diamond bit with the diameter of 46 mm. The results from the drilling process in the Ruskov andesite by impregnated diamond bit in an interval of the thrust F from 5 082 to 10 286 N and the revolution from 0 to 17,8 s-1 on the drilling stand at the Institute of Geotechnics are presented in this paper.
