The objective of this topic is to establish the relationship between the static and the dynamic behaviors of Phu Kradung Formation Sandstone at different applied axial stress levels. Monotonic compressive strength and deformation modulus under confining pressures 0, 6, 12, 20, 30 MPa were determined. For the unconfined compression, electrical gauges were used to measure the axial and lateral deformations, but mechanical gauge and oil volume change were used instead in confined compression measurements. The ultrasonic waves were step measured on the rock at hydrostatic stress fields and at applied compression stress level at 50 and 75 percentages of their strength under that confining stress series. Oriented core specimens, with cross lamination perpendicular (0°) and parallel (90°) to the direction axial load application, were prepared to enable the anisotropic observation. The ratio of ultrasonic wave velocities at each state stress level is determined. The mathematic empirical between ultrasonic wave velocities and the rock strength, and their dynamic and static elastic modulus are established. This enable the use of ultrasonic measurement on prediction their rock strength and deformation characteristic. Results indicate that the ultrasonic wave velocities, the static elastic modulus (Es) and dynamic elastic modulus(Ed) tend to increase with increasing the applied stresses. A mathematic correlation of elastic modulus to confining stresses of each stress level is also attempted. The effects of cross lamination to these results are also discussed. Though the wave velocities give good correlation to deformation modulus, only dry condition is concerned. Therefore, further research should be investigated on saturation condition.

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