Integrating Acoustic Measurements and Microstructural Analysis on the Bebertal Sandstone to Predict the State of Stress Before Deformation

Abstract

This case study presents an experimental investigation of predicting the state of stress before deformation by integrating acoustic measurements and microstructural analysis on dry Bebertal sandstone. Three dry cubic Bebertal sandstone goes through two different stress path with three different maximum differential and hydrostatic stress under true triaxial stress at room temperature. Acoustic measurements were measured while conducting the deviatoric and hydrostatic stress method. The aim was to determine whether the hydrostatic stress can create the same stress before deformation. After all three samples went through deviatoric stress, three deformed samples based on the acoustic measurement shows different stress points when deformed. Hydrostatic stress was applied to the samples after deviatoric stress. Unfortunately, the hydrostatic method was unable to predict the state of stress before deformation. The deformed samples are then digitized to map out cracks spread throughout the samples. There was a correlation between maximum differential stress with number of cracks where the higher the maximum differential, the higher the number of cracks residing in the sample.