Determination of Young’s modulus of the rock mass from geophysical well logs

Geophysical logging of site investigation boreholes can provide a wide range of useful geotechnical information ranging from the formation density (gamma/gamma log) to the dynamic elastic moduli (full wave train sonic log). In this paper, the use of Young’s modulus as a measure of the deformation characteristics of the rock mass is examined. A comparison is made between the dynamic value obtained from geophysical borehole logging and the static value obtained directly from the laboratory testing of samples collected from the borehole. The data are obtained from a number of BGS boreholes. It is shown that although the prediction of the static value of Young’s modulus from the dynamic value is dependent on a knowledge of the borehole lithology, the use of the dynamic elastic moduli can yield considerable useful engineering information in the assessment of the deformation properties of the rock mass.