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This experimental study determines the effects of pore pressure on the compressive strengths and elasticity of six ornamental stones. An approach to determine the pore pressure in low porosity rocks is presented. Rectangular rock specimens (50 × 50 × 100 mm 3 ) under dry and wet conditions were axially loaded under different rates from 0.001-10 MPa/s using a polyaxial load frame. The confining pressures ranged from 0 to 12 MPa. Wet granite, marl, marble, Phra Wihan sandstone, Phu Phan sandstone, and siltstone specimens have an average water content of 0.14%, 2.7%, 0.09%, 2.05%, 4.9%, and 1.5%, respectively. Compressive shear failure was observed in specimens under slow loading rate while extension failure was found in specimens under high loading rate. The strength values of the wet specimens were lower than those of the dry ones, particularly under the high confining pressure and loading rates.The strength values obtained from the dry testing were used to quantitatively calibrate the loading rate effect from the wet strengths, and hence the effect of pore pressure could be calculated. The pore pressures notably reduced the compressive strength and elastic modulus, and slightly increased Poisson's ratio of the rocks tested.

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