SYMPOSIA PAPER Published: 01 January 1970

Predicting Modulus of Deformation Using Rock Quality Indexes


Field and laboratory test data from twelve construction sites show that the Velocity Index and the Rock Quality Designation (RQD) are indexes of in situ rock quality. The Velocity Index is the square of the ratio of the field seismic or sonic velocity to the laboratory sonic velocity. The RQD is a modification of core recovery measurements and can be correlated with the field static modulus of deformation. The Velocity Index has a similar, but poorer, correlation with the modulus of deformation because field dynamic tests involve a much larger volume of rock than field static tests. These correlations can be used to estimate the in situ modulus of deformation from core observations and geophysical testing.

Author Information

Coon, RF
A. A. Mathews, Inc., Arcadia, Calif.
Merritt, AH
H. G. Acres, Ltd., Niagara Falls, Ontario, Canada
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Developed by Committee: D18
Pages: 154–173
DOI: 10.1520/STP29146S
ISBN-EB: 978-0-8031-4590-0
ISBN-13: 978-0-8031-0047-3