Numerical modeling of fracturing in permeable rocks via a micromechanical continuum model

Abstract

Summary The paper presents a micromechanical approach to describe the failure of low‐permeability brittle rocks as a multiscale fracturing process based on a poroelastic microcrack‐damage model. Failure is formulated deep down at the fine pore scale as a material degradation phenomenon driven by microcrack growth that also impacts upon hydromechanical properties. A set of damage tensors describes the effect of dual‐scale porosities (nanopores and microcracks) on both the hydraulic and poroelastic rock properties. Essentially, the multiscale model reconstructs the coupling effect of hydromechanical forces at the continuum level from the ground up through the upscaling of multiphase interactions at the fundamental structural level of the material. As a result, many macroscopic characteristics emerge naturally such as friction angle, fracture properties, and most importantly, Biot's coefficient taking on a tensorial form that is generally anisotropic. The model is validated within the framework of finite elements to illustrate various baseline constitutive features such as the effect of microcrack growth on the nonlinear stress‐strain response and the induced anisotropy in the context of lab experimental tests and boundary value problems. Heterogeneities of the rock samples were incorporated by choosing material properties to be stochastic following Weibull and lognormal distributions. Numerical results appropriately replicated typical experimental observations where fracture localization and propagation are shown to be a multiscale phenomenon emerging from microcrack growth and coalescence at the microscale, with concomitant enhancement in fluid conductivity.

Efficient co‐solution of time step size and independent state in simulations of fluid‐driven fracture propagation with embedded meshes

“…7,8 In order to further improve their resolution and accuracy, both the phase-field and CDM methods rely on adaptive meshing technology. 9,10 In the other class of approaches, fractures are represented explicitly by a sharp lower-dimensional interface within the domain. Examples include fitted methods (e.g., zero-thickness interface methods, [11][12][13] ) and embedded methods (e.g., the generalized/extended finite element method, G/XFEM [14][15][16][17] ).…”

“…In the first category, fractures are modeled by diffusive bands such as the normalized indicators of the phase‐field method 5,6 and the damage field of the continuum damage models (CDMs) 7,8 . In order to further improve their resolution and accuracy, both the phase‐field and CDM methods rely on adaptive meshing technology 9,10 . In the other class of approaches, fractures are represented explicitly by a sharp lower‐dimensional interface within the domain.…”

Applications of high‐resolution borehole image rapid synthesis method for the refined detection of in‐suit rock mass structural features during deep‐buried geotechnical engineering

“…At present, geological exploration and data analysis are the main way to obtain the in-suit structural features of underground rock mass, and digital panoramic borehole camera technique is one of the important ways in geotechnical engineering. [4][5][6] The obtained camera video or panoramic images by using the borehole camera technique, which is a key approach to the direct detection of in-suit rock mass structures, have accurately recorded the structural features of deep-buried rock mass in the hole, [7][8][9] such as fault, joint and fracture zone, which are important parts for rock mass. Therefore, how to obtain the high-resolution panoramic image of rock mass rapidly and effectively inside the borehole has been an important significance for geotechnical engineering and underground engineering construction.…”