ABSTRACT
This research intends to use the ultrasonic properties of the rocks to classify weathering grade of sandstones and to correlate their physical and mechanical properties. Sandstone specimens were collected from Nam Phong (NP) and Phra Wihan (PW) Formations, Khorat Group, Northeast Thailand. Three weathering grades were categorized as fresh (I), slightly weathered (II) and moderately weathered (III). Petrofabric of both NP and PW sandstones at each degree of weathering were observed. Physical properties and uniaxial compressive strength tests were also conducted in the laboratory. Both ultrasonic compressional (Vp) and shear (Vs) wave velocities of the rocks were measured. The results of the research indicated that the ultrasonic wave velocities decrease as increasing of degree of weathering and porosity. On the contrary, the wave velocities increase as increasing percentage of quartz, density and uniaxial compressive strength.
