Pfc Gbm Brittle Rock

PFC GBM Brittle Rock

Use this skill to design, explain, or implement PFC2D grain-based brittle-rock models (GBM / equivalent crystal model) from the bundled GBM + prefabricated-crack biaxial-compression case. The core route is: mineral-seeded particle pack -> Voronoi/rblock grain geometry -> mineral geometry export -> fine particle refill by mineral regions -> biaxial consolidation -> prefabricated crack cut -> per-mineral LPBM + smooth-joint grain-boundary assignment -> biaxial loading with fracture, AE-like, and energy histories.

Parent Skill Relationship

pfc-gbm-brittle-rock is a child skill of pfc-workflow. It owns the GBM specimen-construction and brittle-rock mechanism portion, not the full project lifecycle.

Use these handoffs:

• Parent pfc-workflow: owns full planning, calibration campaign control, solve management, V&V, and delivery.
• Sibling pfc-basics: basic domain, ball, wall, geometry, group, and range setup.
• Sibling pfc-cad-import: geometry import/export, geometry ranges, wall import, and rblock/geometry conversion details.
• Sibling pfc-mineral-heterogeneity: image/mineral fraction intake, mineral phase logic, and per-mineral parameter assignment.
• Sibling pfc-contact-models: linearpbond, smoothjoint, CMAT ordering, bond methods, and contact-property audits.
• Sibling pfc-servo-calibration: biaxial confining pressure, wall-servo gains, and stress convergence.
• Sibling pfc-fish: fracture tracking, callbacks, histories, and reusable FISH refactoring.
• Sibling pfc-ae-energy: AE/energy/source-mechanism post-processing if fracture or energy histories are used as AE proxies.
• Sibling pfc-postprocessing: stress-strain, crack-count, energy, and field plots.

Relationship with existing brittle-rock family skills:

• pfc-brittle-rock-bpm: use for standard BPM limits and baseline brittle-rock theory.
• pfc-equivalent-crystal-model: use for chapter-level equivalent-crystal explanation and Hoek-Brown validation narrative.
• pfc-flat-joint-brittle-rock: use when the task is FJM/FJM3D rather than GBM/smooth-joint grain boundaries.

When To Use

Use through pfc-workflow when the task asks to:

• build or explain a GBM / equivalent crystal model in PFC2D
• model brittle rock with mineral grains and grain-boundary interfaces
• convert mineral-seeded particles into Voronoi/rblock grain regions
• assign quartz, feldspar, and mica-style groups to a fine particle specimen
• use smoothjoint contacts to represent grain boundaries
• add a prefabricated slit/fracture before biaxial compression
• monitor tension/shear cracks by linearpbond and smoothjoint source
• compare GBM against standard BPM for brittle-rock compression/tension behavior

Required Inputs

Ask for these if missing:

• PFC version and whether the target is PFC2D.
• Specimen width/height and particle radius range.
• Mineral groups and target proportions or the source case proportions.
• Prefabricated crack angle, length, and aperture.
• Biaxial confining stress and loading rate.
• Mineral contact parameters and smooth-joint grain-boundary parameters.
• Required outputs: stress-strain, crack counts, energy terms, AE-like event increments, fractures, or fields.

Migrated Source Case

The bundled canonical case is scripts/canonical/gbm-prefabricated-crack-biaxial/.

Stages:

1. stage_01_initial_particle_pack.dat: coarse mineral-seeded particle pack.
2. stage_02_voronoi_rblock_geometry.dat: convert particle centers to Voronoi/rblock geometry.
3. stage_03_export_mineral_geometry.dat: assign rblocks back to mineral groups and export geometry sets.
4. stage_04_refill_particles_by_mineral_geometry.dat: fine particle refill and mineral group assignment by geometry.
5. stage_05_biaxial_confining_servo.dat: biaxial confining stress servo.
6. stage_06_prefabricated_crack_cut.dat: create slit geometry and delete balls inside it.
7. stage_07_gbm_contact_assignment.dat: assign per-mineral LPBM contacts and smooth-joint grain-boundary contacts.
8. stage_08_trim_specimen.dat: trim outer particles and save ready state.
9. stage_09_biaxial_loading_monitoring.dat: load in biaxial compression and record mechanics/fracture/energy histories.
10. fracture_tracking.p2fis: bond-break callback, fracture creation, and fragment updates.

Large/generated source files such as save states and project metadata are intentionally not bundled.

Documentation-Backed Rules

PFC command families checked through pfc-mcp are summarized in references/pfc-doc-notes.md:

• ball distribute, ball group, wall generate, wall import
• geometry set, geometry polygon create, geometry range selection
• rblock construct, rblock export, rblock delete
• contact cmat, contact model, contact method, contact property
• smoothjoint as a version-sensitive contact model term
• fracture create, fragment compute, fish callback event bond_break
• history, fish history, model energy mechanical on

Working Rules

• Do not use GBM as a 3D solution; this migrated case is PFC2D.
• Keep the coarse mineral-seed construction separate from fine particle refill.
• Keep mineral-body contacts (linearpbond) separate from grain-boundary contacts (smoothjoint).
• Treat the provided contact parameters as source-case seeds, not universal granite constants.
• Route detailed smooth-joint syntax and CMAT inheritance audits to pfc-contact-models.
• Route biaxial servo stability to pfc-servo-calibration.
• Route fracture callback refactoring to pfc-fish.

Output Contract

A complete handoff back to pfc-workflow should include:

• GBM stage list and copied command files
• mineral group names and proportions
• grain-boundary model and smooth-joint parameters
• prefabricated crack angle, length, aperture, and geometry selection rule
• confining stress, loading velocity, and stop criterion
• fracture/energy/history output list
• validation plan against stress-strain, crack mode, crack path, and brittle-rock expectations

Local Contents

• references/overview.md: scope, model boundary, and stage route.
• references/formulas.md: brittle-rock BPM, GBM, smooth-joint, biaxial, crack and energy formulas.
• references/source-code-complete-pfc6.md: full staged code migration notes.
• references/pfc-doc-notes.md: PFC documentation notes for GBM-related commands.
• references/gbm-prefabricated-crack-case.md: source case parameters and outputs.
• examples/README.md: materialization and validation guidance.
• scripts/canonical/gbm-prefabricated-crack-biaxial/: migrated public-safe .dat and .p2fis templates.
• scripts/canonical/manifest.json: script inventory.