Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6092-21 – Standard Test Method Technical Guide
📐 Scope and Application
ASTM D6092-21, Standard Practice for Specifying Standard Sizes of Stone for Erosion Control, establishes a uniform framework for defining stone size designations and mass gradations. This practice is specifically intended for riprap, spalls, and bedding materials used in slope protection of dam embankments, streambank erosion control, and bridge pier and abutment protection. The values stated in inch-pound units are regarded as the standard.
The practice explicitly excludes materials used for outer harbor structures such as breakwalls and revetments, where armor stone or cover stone typically ranges between 5 and 25 tons. As emphasized in Section 1.4, this practice serves as an organized collection of options and does not recommend a specific course of action. It cannot replace education or experience and must be applied with professional judgment considering the unique aspects of each project.
🪨 Classification and Terminology of Stone Materials
The terminology section of D6092-21 provides critical classifications for materials based on particle size distribution and mass. The following table summarizes the primary stone types defined within the standard’s scope.
| 🟦 Stone Type | 📏 Designation / Size Range | 🔬 Sieve / Mass Limits |
|---|---|---|
| Riprap | Mass less than 3000 lb (1400 kg) | Sized and graded per specified class |
| Bedding Stone (Spalls) | Minus 6½ in. (163 mm) | Ranges to No. 16 (1.18 mm) |
| Filter Stone | Minus 2.0 in. (50 mm) | Ranges to No. 100 (150 µm) |
💡 Understanding Gradation: According to Section 3.2.2, gradation is defined as the proportions by mass of stones distributed within specified ranges between maximum and minimum limits. Proper gradation is essential for achieving the designed stability and hydraulic performance of the erosion control layer.
📏 Standard Sizes and Placement Specifications
D6092-21 emphasizes a systematic approach to specifying stone sizes through maximum mass thresholds and defined gradation envelopes. The practice references ASTM D5519 for particle size analysis of riprap materials and ASTM E11 for woven wire test sieve cloth standards. These standardized test methods ensure consistency in material specification and acceptance.
For composite layered systems, the standard provides typical thickness guidelines for the filter and bedding layers that are placed prior to the riprap. These layers are designed to prevent soil erosion from beneath the stone armor while permitting adequate drainage.
| ⚙️ Layer Type | 🎯 Typical Thickness (in.) | 📐 Typical Thickness (mm) |
|---|---|---|
| Filter Layer | 8 to 10 in. | 200 to 250 mm |
| Bedding Layer | 6 to 8 in. | 150 to 200 mm |
| Riprap Layer | Variable (per design) | Variable (per design) |
🔍 Professional Integration: When specifying stone under D6092, practitioners should also consult ASTM D4992 (Practice for Evaluation of Rock to be Used for Erosion Control) to verify the stone’s durability, hardness, and resistance to weathering and freeze-thaw cycles. These standards are complementary.
⚠️ Standard vs. Standard of Care: As stated in Section 1.4, this ASTM standard is not intended to represent or replace the standard of care for professional services. The unique aspects of each project site, including hydraulic forces and soil conditions, must be carefully evaluated by a qualified professional engineer.
❓ Frequently Asked Questions
🔍 What is the maximum mass for a stone to be classified as riprap under D6092?
According to Section 3.2.4, riprap materials are generally less than 3000 lb (1400 kg) in individual mass. Stones larger than this threshold are typically classified as armor stone or cover stone and fall outside the scope of this practice.
💡 What are the recommended thicknesses for filter and bedding layers?
Section 3.2.1.1 specifies that the filter layer is typically placed to a thickness of 8 to 10 in. (200 to 250 mm), while the bedding layer (spalls) is typically placed to a thickness of 6 to 8 in. (150 to 200 mm) prior to riprap installation.
⚡ How is particle size analysis conducted for riprap materials per this standard?
The standard directly references ASTM D5519 (Test Methods for Particle Size Analysis of Natural and Man-Made Riprap Materials) for this purpose. Sieve cloth used during testing must conform to ASTM E11 specifications.
📌 Does this practice apply to stones used in coastal breakwaters and harbor structures?
No. Section 1.1 explicitly excludes outer harbor structures such as breakwalls and revetments where individual stone sizes typically range between 5 and 25 tons, or where dimension stone requires cut specifications for laid-up structures.