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D4341-03 – Standard Test Method Technical Guide
📐 Specimen Preparation and Scope
ASTM D4341-03 defines the method for evaluating the creep behavior of intact cylindrical hard rock core specimens under uniaxial compression. “Hard rock” is specifically defined as material with a maximum failure strain of less than 2%. This test is vital for designing permanent underground structures like waste repositories and tunnels.
Proper preparation per Practice D4543 is mandatory. Cores must have machined flat ends to ensure uniform stress distribution. Practices D5079 apply to sample preservation and transport. Moisture content follows Test Method D2216.
⚠️ Intact vs. In-Situ: Laboratory values typically do not reflect large-scale in situ properties (Annex A1). Parameters must be applied with professional judgment in engineering applications.
⚙️ Testing Procedure for Creep
The test places the prepared specimen in a loading frame verified per Practices E4. If elevated temperatures are required, the assembly is heated uniformly. Axial load is then applied rapidly and sustained constant. Axial deformation is monitored continuously as a function of elapsed time to construct the creep curve.
| 🟦 Standard | 📏 Title | 🎯 Application in D4341-03 |
|---|---|---|
| D 4543 | Preparing Rock Core Specimens | Specimen dimensional tolerances |
| D 5079 | Preserving and Transporting Rock Core | Sample integrity |
| E 4 | Force Verification of Testing Machines | Load frame calibration |
| D 6026 | Using Significant Digits in Geotechnical Data | Data calculation guidelines |
| 📐 Parameter | ⚡ Specification | 📏 Reference |
|---|---|---|
| Rock Type | Hard Rock (failure strain < 2%) | Section 1.1 |
| Specimen | Intact Cylindrical Core | Section 1.1 |
| Loading | Uniaxial Compression, Sustained | Section 3.1 |
| Temperature | Ambient or Elevated | Section 3.1 |
| Measured | Strain vs. Elapsed Time | Section 3.1 |
💡 Data Tip: Log data at a high rate immediately after loading to capture the instantaneous elastic and primary creep phases. Adhere to Practice D6026 for rounding significant digits.
📊 Significance and Data Calculation
The creep test is significant for evaluating time-dependent deformation under sustained loads. The standard requires values to conform to significant digit guidelines in Practice D6026. The precision of the test method depends on competent personnel and suitable equipment, with agencies meeting Practice D3740 considered generally capable of competent and objective testing.
❓ Frequently Asked Questions
🔍 What qualifies as a “hard rock” for D4341-03?
An intact cylindrical core specimen with a maximum axial strain at failure of less than 2%.
💡 How should specimens be prepared?
Per Practice D4543, which dictates specific length-to-diameter ratios and end flatness tolerances to ensure uniform loading.
⚡ What is the primary purpose of this creep test?
To provide quantitative creep parameters for the stability analysis of long-term underground structures subjected to constant loads.
📌 How is precision defined in this standard?
Precision depends on personnel competence and equipment suitability. Agencies meeting Practice D3740 are considered capable of competent testing.