Evaluating the Effect of Different Stress Path Regimes on Borehole Deformation Using Convergence Measuring Device

A laboratory study was conducted to investigate the borehole deformation of poorly cemented sandstone rocks with Uniaxial Compressive Strength (UCS) less than 10 MPa under different stress path regimes by using a convergence measuring device (CMD). Synthetic thick-walled hollow cylinders (TWHCs) comprised of sand grains, Portland cement and water were prepared for this study. A series of mechanical tests including uniaxial and triaxial compression tests were performed to examine the physical properties of the artificial sandstones. A vertical displacement loading rate of 0.07 mm/min and confining pressure at a rate of 0.2 MPa/min were applied for the experiments. The CMD was deployed inside the TWHC specimen to measure the borehole deformation. Five different stress paths were applied to the specimens to investigate the effect of stress paths, and three different cement agent contents (10%, 12% and 14%) were considered to study the effect of cement content on the borehole failure. The effect of the cement content on the borehole failure was found to be more significant than the effect of change in stress path regimes.