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D1587 – Standard Test Method Technical Guide
ASTM D1587/D1587M-15 establishes the standard practice for thin-walled tube sampling of fine-grained soils to recover intact samples for geotechnical laboratory testing. This method ensures minimal disturbance, allowing accurate determination of engineering properties such as strength, compressibility, and permeability. Below are key specifications and procedures based on the standard.
📐 Sampler Tube Specifications and Materials
Thin-walled tubes must meet the specifications in Section 6.3 of the standard. They are manufactured from electric-resistance-welded or seamless carbon or alloy steel tubing conforming to Specification A513/A513M. The tubes feature a sharp cutting edge with bevel angles typically ranging from 10° to 15° to facilitate clean penetration. The table below lists standard tube dimensions:
| 🟦 Nominal Diameter | 📏 Wall Thickness | 📐 Cutting Edge Angle | 🎯 Material Requirement |
|---|---|---|---|
| 2 in. [50 mm] | 0.035 in. [0.9 mm] | 10° to 15° | A513/A513M |
| 3 in. [75 mm] | 0.045 in. [1.2 mm] | 10° to 15° | A513/A513M |
⚙️ Sampling Procedure and Quality Evaluation
The sampling process begins with advancing a clean borehole to the target depth using rotary drilling or hollow-stem augers per Practices D1452, D6151, or D5783. The thin-walled tube is then pushed into the soil continuously at a steady rate of 1 to 2 ft/min [0.3 to 0.6 m/min] to minimize disturbance. After full penetration, the tube is rotated one to two turns to shear the sample at the base and retrieved carefully. Sample quality is assessed through recovery ratio and visual inspection for defects such as cracks or voids. The following table summarizes key quality criteria:
| 📋 Quality Parameter | ⚡ Specified Criteria | 🎯 Acceptance Threshold |
|---|---|---|
| Recovery Ratio | >95% | Suitable for advanced testing |
| Visual Disturbance | No fissures, voids, or separation | Accept for general testing |
| Tube Condition | No significant dents or bending | Replace if damaged |
✔️ Best Practice: Maintain a penetration rate of 1–2 ft/min [0.3–0.6 m/min] to avoid plugging or disturbance. A recovery ratio below 90% may indicate sampling issues.
📊 Sample Preservation and Handling
Once retrieved, samples must be preserved to retain in-situ moisture content and structure. Both ends of the tube are sealed with protective caps or moisture-proof wax. Samples should be stored in a temperature-controlled environment, protected from sunlight and freezing. Careful transportation minimizes vibration and impact. Practice D4220 offers detailed guidelines for preservation and transport.
⚠️ Limitation: This method is not suitable for soils containing coarse sand, gravel, or cementation. Use split barrel samplers (D1586) or rotary coring (D3550) for such conditions.
❓ Frequently Asked Questions
🔍 Q: What is the primary purpose of thin-walled tube sampling?
A: To obtain high-quality intact samples of fine-grained soils for laboratory tests of strength, compressibility, permeability, and density.
💡 Q: How is sample quality evaluated after retrieval?
A: Mainly through recovery ratio (length of sample obtained relative to tube penetration) and visual inspection for disturbance. A ratio >95% with no visible defects indicates high quality.
⚡ Q: Can this method be used for sandy or gravelly soils?
A: No, it is limited to fine-grained soils that can be penetrated by the thin-walled tube. For coarser soils, use split barrel samplers (D1586) or other devices.
📌 Q: What are the key referenced standards?
A: Important companion standards include D4220 for sample preservation, D1452 for rotary drilling, and D6151 for hollow-stem augers.