A discrete element model for rock pressure sensitivity and stress-driven contact stiffness evolution

Area of Science:

• Geotechnical Engineering
• Rock Mechanics
• Computational Modeling

Background:

• Deep underground engineering expansion necessitates understanding rock mechanical behavior under high in-situ stress.
• Traditional discrete element models struggle with tangent modulus evolution and over-linearize compaction stages.

Purpose of the Study:

• To develop a robust discrete element model capable of accurately simulating rock mechanical behavior under varying confining pressures.
• To address limitations in traditional models regarding stiffness assumptions and tangent modulus evolution.

Main Methods:

• Integrated triaxial test data (granite, slate, sandstone) to establish an exponential relationship between tangent modulus and mean stress.
• Developed a variable stiffness parallel bond model with real-time stiffness mapping and adaptive updating.
• Implemented a multi-confining-pressure calibration strategy using parameter selection and interpolation verification.

Main Results:

• The variable stiffness model accurately reproduced full stress-strain curves for carbonaceous slate across a wide confining pressure range.
• Achieved small relative errors in peak strength prediction.
• Successfully captured pressure-sensitive responses like compaction stage shortening, peak strength enhancement, and brittle-ductile transition.

Conclusions:

• The proposed variable stiffness parallel bond model offers a high-fidelity numerical tool for predicting rock behavior in deep environments.
• The model overcomes limitations of traditional discrete element methods in simulating complex rock deformation under high stress.