Method for determining fracture toughness of rock by core boring

摘要

The disclosed method introduces a pressure effectivity factor h, so as to continuously determine fracture toughness KIC of rock during core boring by using the equation of    KIC=0.346√·hQ/B ; andhere, N is the revolving speed of a coring bit, Q is the pressure supplied to it, L is its drilling speed, B is the width of its bit face, and ε is the number of rows of its face stones. The pressure effectivity factor h is predetermined by using both a core whose fracture toughness is measured by the ISRM (International Society for Rock Mechanics) method and the above constants which are used in boring said core.