ABSTRACT:

It is an important laboratory test which the elastic waves of rock specimens are measured, and in general the velocities of two types elastic waves are used. in this paper, it is tried to develop the simultaneously measured system for P, S wave velocities and electric resistivity of a rock sample and its laboratory equipment. P and S wave are analytically found out from the recorded waves. And on the same time, the electric resistivity of this rock specimen is measured by geo science (GS) method. Furthermore, P, S wave velocities and electric resistivity obtained from this system are compared with these quantities given by the usual measurement methods. As the results, it is confirmed that this measurement system is useful for the various rock specimens.

I.
INTRODUCTION

Recently, it is important to measure the velocity of elastic wave of the rock specimens by the laboratory test. In this test, P and S wave which are two velocities wave are measured. In this study, the development of the equipment, which can measure electric resistivity and P, S wave velocities of the rock specimens at the same time, was presented, and the effectiveness was examined by some rock specimens. Hypocenter of P, S wave is given by the impulse of the high frequency. This impulse is sent to the indirection of the repetition rock specimens and it is got other side. P,S wave are read from the wave recorded by the oscilloscope, and simultaneously, the electric resistivity of the rock specimens is measured by the GS method')· Using this equipment, electric resistivity and P, S wave velocities of various specimens are measured under various wet conditions specimens: These values got from this system and conventional system were compared in order to examine the validity of this equipment. As the result, it was confirmed that this measuring system was useful for various rock specimens.

2
·TEST EQUIPMENT

The developed measuring system of the elastic wave system is shown in Figure 1. This system is composed by;

  1. wave factory,

  2. High speed power umplilier,

  3. AE sensor,

  4. preamplifier,

  5. discriminator,

  6. circuit of the oscilloscope,

  7. simultaneous measurement holder.

The wave factory generated the impulse of 1.OHz frequency, square wave, voltage ± 15V, and it is sent in one side of the rock specimens. One AE sensor is vibrated, and it is received by AE sensor installed inthe other side. The received waveform is amplified in preamplifiersand discriminator, etc., and it is displayed in the oscilloscope. And, the oscilloscope saves displayed waveform for the file, and thevelocity of elastic wave of the rock specimens is calculatedfrom thiswaveform. Figure 2 shows the plane view of simultaneousmeasurement holder among the equipment. This is the sample holder used for conventional electric resistivitymeasuring by GSmethod. The AE sensor is installed for the side, and which is designed in order to enable thesimultaneous measurement ofvelocity of elastic wave and electric resistivity in the rockspecimens.

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