Application of Shear Wave Velocity to Rock Rippability Estimates Based on Poisson's Ratios Determined from Laboratory and Field Measurements

Being able to accurately identify the rippability of rock materials is essential for many civil engineering projects that involve rock excavation. The current procedure for rock rippability estimations using geophysics is solely based on the P-wave velocity of the rock. However, with the increased use of multichannel analysis of surface waves (MASW) for performing pseudo 2D V, surveys, the need for V, rippability charts continues to increase. This study develops new rippability charts based on rock V. To do so, Poisson's ratios of different rock formations are first determined using downhole measurements and laboratory testing on rock core samples. The results are then compared to examine the limitations of laboratory testing as a common practice for rock Poisson's ratio estimation. It was observed that in situ Poisson's ratios of rock formations are often underestimated using laboratory measurements. This is because laboratory testing is conducted on a small sample of intact rock, which is not a true representative of the in situ rock conditions. The results clearly indicate the need to account for such underestimation in the rock Poisson's ratio when using laboratory measurements. Finally, using the Poisson's ratios from downhole measurements, updated rock rippability ranges are determined based on V-s. These charts can be used along with any field methods that measure V, of subsurface materials to estimate rock rippability.