Open AccessMicro-crack propagation and coalescence during time-dependent deformation of granite based on numerical manifold method
Author(s) -
Xian-yang Yu,
Tao Xu,
Michael Heap,
Patrick Baud,
Zhen Heng
Publication year - 2020
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/570/2/022064
Subject(s) - creep , coalescence (physics) , brittleness , materials science , crack closure , mechanics , overburden pressure , fracture mechanics , geothermal gradient , deformation (meteorology) , cracking , geology , geotechnical engineering , composite material , physics , geophysics , astrobiology
An understanding of influence of micro-cracks on time-dependent deformation in granite is of fundamental importance in many situations, such as nuclear waste storage facilities or the exploitation of geothermal resources. Time-dependent cracking is considered to be the main mechanism of brittle creep in granite. Creep strain rates are strongly influenced by the density of pre-existing defects that also exert a significant influence on rock physical properties. We introduce a new model that combines the subcritical crack growth (SCG) theory and the numerical manifold method (NMM) to link the local damage (using an exponential material softening law) caused by micro-crack propagation and the macroscopic creep deformation typically observed in granite specimens. In this model, each element contains a virtual micro-crack that can propagate sub-critically following Charles’ law. Once the virtual micro-crack length reaches a given value, it will convert to a real micro-crack, which can cut through adjacent elements, open, and slide according to the principle of NMM. We also investigated the influence of virtual micro-crack length, confining pressure and differential stress on creep behaviour. The fact that numerical simulations are in good agreement with experimental results shows that the NMM combined with the SCG theory is a suitable method for modelling the creep behaviour of rocks.