DEVELOPMENT OF EQUIPMENT FOR STUDYING PORE PRESSURE EFFECTS IN ROCK.

Evidence is presented that pore pressure has a measurable effect on rock strength and must be considered in any carefully conducted laboratory testing program for rock properties. It is not entirely clear, however, to what extent pore pressure affects test results for various rocks nor is it known how significant its effects might be in the design of structures founded in or upon rock. Thus the need for equipment to study pore pressure in rock is recognized. The report discusses the development of such equipment, its construction details, and operation. The pore pressure triaxial compression chamber is designed to accommodate 2 18-inch diameter specimens and operate at pressures up to 10,000 psi. Procedures relative to specimen preparation and saturation are described. Typical results are presented to demonstrate the reliability of the apparatus. The relationship among volumetric strain, pore pressure, and axial and diametric strain is discussed with regard to the mechanism of brittle fracture of rock. Author