Double torsion testing machine to determine the subcritical fracture index in rocks

Abstract

This paper discusses the design methodology applied to build a testing machine to determine the subcritical fracture index in a rock, based on double torsion testing in order to characterize naturally fractured formations such as those located in the Colombian Llanos Foothill Basin. These formations have been subjected to cyclic loads over time, causing fractures that trend to spread at subcritical stress intensity values. Similarly, it presents the results of testing conducted on nine specimens of the Tambor Formation from 2 different outcrops to establish the testing traceability in the equipment.