A field method for the determination of rock-mass modulus

A field test for measuring rock modulus was developed and performed at the site of Darlington Generating Station in shaly limestone. The new method yields a value consistent with the rock-mass modulus evaluated from extensometer measurements in the tunnels.A complementary laboratory program to study the effect of specimen size on the elastic parameter was also performed by using compressional and shear wave velocity measurements. It was shown that beyond a threshold value of size, the Poisson's ratio increases, whereas both dynamic shear modulus and Young's modulus decrease with increasing volume of specimen towards the field value of static modulus. Key words: rock-mass modulus, field tests, shear wave velocity, size effect.