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D4879-08 – Standard Test Method Technical Guide
The ASTM D4879-08 standard guide provides a comprehensive framework for geotechnical mapping of large underground openings in rock, covering both civil and mining applications. It emphasizes characterization and documentation of rock mass conditions at the excavation surface, with a focus on timely data collection before construction activities alter surface features.
📐 Scope and Key Requirements
This guide applies to new or existing excavations that are large enough to be accessible, whether regular or irregular in section. Mapping relies on direct observations and measurements; geophysical methods are excluded. The detail level must fit the intended use, supporting design, stability analysis, confirmation of predictions, maintenance, and record-keeping.
| 📐 Parameter | 🎯 Requirement |
|---|---|
| Excavation Type | Large underground openings in rock for civil or mining |
| Mapping Surface | Direct observations and measurements at excavation surface |
| Timing | During or after excavation; ideally before surface modification |
| Units | Inch-pound units standard; SI for information only |
| Data Rounding | Per Practice D6026 for significant digits and rounding |
| Mapped Materials | Rock mass; soil/soil-like materials per applicable ASTM standards |
💡 Best Practice: Complete mapping prior to any construction activity that may obscure surfaces, ensuring capture of critical geologic features for accurate characterization.
⚙️ Mapping Procedures and Data Collection
Mapping procedures should collect sufficient information to define uncertainty and enable consistent interpretation. Key tasks include documenting rock mass conditions at the surface, such as joint patterns, fractures, and faults. The guide does not replace detailed survey of excavation geometry but complements it. All observed and calculated values must follow D6026 guidelines.
| 📏 Application | ⚡ Purpose |
|---|---|
| Design | Establish data base for structural design |
| Stability Analysis | Support assessments of excavation stability |
| Confirmation | Validate geotechnical predictions |
| Maintenance | Assist in monitoring and maintenance programs |
| Permanent Record | Provide documentation for future reference |
⚠️ Safety Note: This standard does not address all safety concerns. Users must implement appropriate safety and health practices and comply with regulatory limitations prior to use.
❓ Frequently Asked Questions
🔍 When should geotechnical mapping be performed?
Mapping should be completed during or after excavation but before construction activity modifies or obscures the surface condition, especially for critical geologic features.
💡 What are the unit standards in D4879-08?
Inch-pound units are regarded as standard, with SI units provided for information only. All values must conform to Practice D6026 for significant digits and rounding.
⚡ Does this guide cover geophysical measurements?
No, geophysical measurements are not included in this guide. Mapping is based on observations and measurements at the excavation surface.
📌 Who is the target audience for this guide?
This guide is intended for engineers, geologists, and contractors involved in civil and mining underground excavations, providing organized information for use with professional judgment.