A method of measuring seismic waves from explosions in rocks
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METHODS
AND
DEVICES
A M E T H O D OF M E A S U R I N G S E I S M I C WAVES FROM E X P L O S I O N S IN ROCKS V. N. K o s t y u c h e n k o
and
A. G. F o m i c h e v
The study of seismic waves due to blasting in rocks can yield answers to a number of questions involving rock breaking and cruzhing, the efficiency of various types of explosives, etc. In turn, such a study cannot be undertaken without suitable methods of measurement. In developing such a method we must consider a number of questions, beginning with the characteristic features of the physical process and ending with the constructive and technological features of the measurement process. This combined approach will be used in this article. The characteristic features of seismic waves due to blasting in rocks are as follows: sudden arrival (rise time less than 1 msec); comparatively small displacement (a few millimeters); and high acceleration (of the order of 103 g). The latter feature complicates the development of a method of wave recording, especially near the explosion. For the same reason, we cannot use ordinary seismic apparatus. For example, in the well-known VIB devices ['1] the pendulum attachment elements are damaged and the parasitic vibrations exceed the useful signal. The method developed at the Institute of Physics of the Earth of the Academy of Sciences of the USSR is based on an inductive velocity pickup (IVP) designed by Yu. F. Solov'ev. The use of special amplifiers with high output currents, while permitting recording on standard oscillographs (N-t05, N-115, N-117) convenient for field work, leads to a marked reduction in the signal output power from the pickup (so that it can be made small in size), facilitatt'5 regulation of the channel sensitivities, and finally, made it possible to use high-frequency galvanometers giving a fairly broad frequency band in the measurement channel The high sensitivity of the measuring system means that it can also be used to monitor the state of the solid rock or the quality of the setting-up of transducers in boreholes. One method of monitoring, based on recording waves z from the impact of steel spheres, is given below. [z/:, :/ //, / / / / / / ' / \t\\\\\\~
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Fig. 1. Diagram of IDS-3 pickup,
F Fig. 2. Diagram of instrument for calibrating pickups.
Institute of Physics of the Earth, Academy of Sciences of the USSR, Moscow. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaeinykh, No. 3, pp. 105-110, May-June, 1974. Original article submitred April 23, 1973. 9 1975 Plenum Publishing Corporation, 227 West 17thStreet, New York, iV. Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $15.00.
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Fig. 3. Oscillograms obtained by m
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