Study of Stress on Fracture Toughness Test Mode I Using Photoelastic Method

Stress condition of rocks generally can be known, but at the point of fracture initiation is often not known with certainty. To study the stress around fracture initiation, it is difficult to do using mathematical calculations so that the necessary methods of alternative solution is photoelastic method. Principal stress can be obtained using photoelastic method in form of deviatoric stress. In this research, photoelastic method is conducted to study the stress on fracture toughness tests mode I (tension). Sample testing conducted at the Laboratory of Geomechanics and Mine Equipment Institute of Technology Bandung involved the physical properties and mechanical properties test to obtain the sample characteristics as input data for numerical modeling using Rocscience 3 version 1.0, such as the natural density, uniaxial compressive strength, Young’s modulus, Poisson’s ratio, and tensile strength. Moreover, fracture toughness tests mode I are conducted on Modified Ring Test (MRT) and Central Straight-Through Crack Brazilian Disk (CSCBD) using photoelastic method. The deviatoric stress can be calculated using colors observed in photoelastic method by following the equation of optical stress. The deviatoric stress obtained from photoelastic method would be compared to numerical method. From this research, it could be concluded that the largest error between results of the stress distribution obtained from numerical method and photoelastic method is 36.17% on Central Straight-Through Crack Brazilian Disk (CSCBD).

ISRM-YSS-2017-016 Study of Stress on Fracture Toughness Test Mode I Using Photoelastic Method.pdf