(441h) Discrete Modeling of Void Porosity in Rock Cutting

Lin, J. S., And Department of Civil and Environmental Engineering, University of Pittsburgh
Mendoza, J. A., University of Pittsburgh
Gamwo, I. K., US Department of Energy

numerical study on the mechanical behavior of rock during cutting is
investigated using the discrete element method. The rock is represented by a
dense packing of circular or spherical particles that are bonded together at
their contact points. Such packing arrangement may lead to a wide range of
porosity depending on the rock being modeled. Very low void porosity rock, say
3%, requires unrealistic computational time to simulate the rock cutting. We
have created rock samples of different void porosity, such as 15%, 10% and 8%
for mechanical tests. Discrete element method uniaxial tests conducted on these
samples gave results consistent with the current understanding as to how the
strength and modulus would increase with the reduction of the void porosity. Scratch
tests were then carried out on these samples. We further carried out tests on a
different set of samples generated with a fixed 16% void ratio but other microproperties
were recalibrated to give the correct bond modulus and bond strength
corresponding to samples of low void porosity samples. The results of the
cutting tests based on the fixed void porosity were found to be essentially the
same as those that void porosity were not explicitly modeled.  Details of this
important finding will be presented in the meeting.