COMPUTATIONAL STUDY USING DISCRETE ELEMENT METHOD FOR STRESS-STRAIN RESPONSE OF GEOMATERIALS

Resumo

Relevant geomaterials, like soils, concretes or rocks, exhibit similar constitutive response
when considering their yield strength dependencies or dilatancy processes. The continuous description
of these geomaterials encounters limitations when large-scale slip and opening of a large amount of
fractures. Discrete-based methods represent the material as an assemblage of independent elements
interacting with one another and can be reproduce the discrete nature of the discontinuities, which are
represented as the boundary of each element. In this case, for each particle, the interaction law is used
in conjunction with the momentum balance principle so as to specify a set of governing equations to
describe its interactions and motion. By solving these equations, we obtain the final state of rest of
these particles. The constitutive stress-strain response is obtained in an uniaxial compression
experiment were a sample of geomaterial is slowly compressed by a piston until failure occurs. The
peak stress at which failure of the sample occurs is known as Unconfined Compressive Strength
(UCS). This work studies these responses in geomaterials samples using Discrete Element Method
(DEM). In our numeric simulation, a set of particles is placed between two piston walls which are
compressed at constant speed. Then, we monitor the position and forces for construct a curve by each
sample. Interactions incorporate translational and rotational degrees of freedom to rotate relative to
each other when in frictional contact. Analytical relationship between the microphysical parameters
and the macroscopic properties can be obtained by conducting a series of computational simulations to
tune the microphysical parameters until desired macroscopic properties. To simulate elastic-brittle
failure of material, a Mohr-Coulomb criterion is employed. These data are used to measure some
elastic properties of the particle model such as Young’s modulus, wall forces, broken bond and the
UCS himself. Results shows that possible obtain significant values for different geomaterials such as
some specific concretes and rocks.