Dynamic Deformation Modulus of Weak Rock Measured from Laboratory and Field Tests

Abbas J. Al-Taie

Abbas J. Al-Taie, Assistant professor College of Engineering, AL-Nahrain University, Baghdad-Iraq

Keywords: Weak Rock, shear modulus, Young’s modulus, Poisson’s ratio, ultrasonic velocity, crosshole

Abstract

This paper compares the dynamic deformation modulus of weak rock measured from laboratory and field tests which were carried out as part of the site investigation works for a major project, west of Iraq. The objective of the survey was to obtain the compressional (Vp) and shear (Vs) seismic wave velocities for computation of dynamic properties of the rock material (shear modulus, Young’s modulus, and Poisson’s ratio) interposed between the investigated boreholes. Laboratory ultrasonic velocity tests were conducted on unconfined core rock specimens using TICO ultrasonic velocity equipment. Field measurements comprised seismic geophysical methods including crosshole technique were used to determine the (Vp) and (Vs). In addition, empirical relationships were used for estimating the unit weight of rock mass employing the results of the seismic wave velocities. The dynamic insitu stiffness measurements were determined and compared with the laboratory values from the ultrasonic tests for estimating rock mass stiffness from the seismic wave velocities.