ANALYSIS OF COMPRESSIVE FRACTURE IN ROCK USING STATISTICAL TECHNIQUES- PART I - A NONLINEAR RULE-BASED MODEL

A new non-linear rule-based model for the fracture in compression of h eterogeneous brittle materials such as rock is presented and used to s tudy crack nucleation and propagation at the grain scale, We have used the model to simulate uniaxial compression tests of rock samples and results underscore the importance of crack interaction in extensile cr acking of rock in compression even at low crack densities. Moreover, t he model produces non-linear stress-strain behavior similar to that ob served in laboratory tests. We have analyzed the stress-strain behavio r and found that in these simulations fracture occurs in the following way,. First, initial damage occurs by random cracking. When approxima tely 15% of the sites are broken, cracks start to interact and coalesc e to form larger cracks which then may propagate a significant fractio n of the array length. Crack extension may be followed by crack nn est and subsequent formation of a damage zone ahead of a clack tip. Final ly, a series of cracks will link and form a fracture that eventually c auses failure. The model shows decreasing compressive strength with in creasing size following a power-law relationship with art exponent tha t is similar to that determined from the study of laboratory, and fiel d-test results. The model can also incorporate heterogeneity in the st rength and geometry of rock fabric, in part II, the model is used to i nvestigate how microscale heterogeneity in these parameters affects ex tensile crack growth in compression. Published by Elsevier Science Ltd .