STUDY OF HIGH-PRECISION MEASUREMENT OF THIRD-ORDER ELASTIC MODULUS FOR ROCK
(1. Institute of Crustal Dynamics of China Earthquake Administration，Beijing 100085，China；
2. College of Civil Engineering and Architecture，Harbin Engineering University，Harbin，Heilongjiang 150001，China)
Abstract：Based on the acoustoelastic theory of rock，velocity variation of longitudinal and transverse ultrasonic waves propagating along the thickness direction of plate rock samples under biaxial loading condition is measured by the pulse echo method to investigate the third-order elastic modulus for rock. The test results indicate that sensors of transversal wave and longitudinal wave are set at the relative surface of the central portion of rock specimen to measure the transversal wave and longitudinal wave at the same position，which not only can weaken the biaxial loading end effect，but also overcome the influence of rock anisotropy on the measured results. Furthermore，time difference between multi-echo signals is measured by pulse-echo method to overcome the influence of couplant and measured circuit on the travel-time difference of echo signals. The pulse-echo method can implement the high-precision measurement of third-order elastic modulus for rock，which provides technical support for the measurement of in-situ crustal stresses.
THURSTON R N，BRUGGER K. Third-order elastic constants and the velocity of small amplitude elastic waves in homogeneously stressed media[J]. Physical Review，1964，(6A)：1 604-1 610.
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2010, Vol. 29 
