Phase field modeling of brittle compressive-shear fractures in rock-like materials: A new driving force and a hybrid formulation

TL;DR

This paper introduces a novel phase field model with a new driving force and hybrid formulation to accurately simulate brittle compressive-shear fractures in rock-like materials, aligning well with experimental results.

Contribution

A new phase field model with a specialized driving force and hybrid formulation for simulating compressive-shear fractures in rocks is developed and validated.

Findings

Numerical results agree with experimental observations.

The model effectively captures the influence of cohesion and internal friction.

The hybrid formulation simplifies implementation and enhances accuracy.

Abstract

Compressive-shear fracture is commonly observed in rock-like materials. However, this fracture type cannot be captured by current phase field models (PFMs), which have been proven an effective tool for modeling fracture initiation, propagation, coalescence, and branching in solids. The existing PFMs also cannot describe the influence of cohesion and internal friction angle on load-displacement curve during compression tests. Therefore, to develop a new phase field model that can simulate well compressive-shear fractures in rock-like materials, we construct a new driving force in the evolution equation of phase field. Strain spectral decomposition is applied and only the compressive part of the strain is used in the new driving force with consideration of the influence of cohesion and internal friction angle. For ease of implementation, a hybrid formulation is established for the phase field modeling. Then, we test the brittle compressive-shear fractures in uniaxial compression tests on intact rock-like specimens as well as those with a single or two parallel inclined flaws. All numerical results are in good agreement with the experimental observation, validating the feasibility and practicability of the proposed PFM for simulating brittle compressive-shear fractures.