ASTM D2487 Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)

Get Certified ASTM D2487 for Reliable Geotechnical Data 

When engineers use a soil sample in a foundation, embankment, or pavement design, certification ensures the sample has the proper group symbol and group name. Representative samples are sent to accredited laboratories for testing, and a report is produced with details of the classification and the supporting data related to particle size and plasticity. This shields project teams from design mistakes that could result from misclassified soils. 

What is the Scope of the ASTM D2487 Standard? 

ASTM D2487 is a standard practice that outlines a method for soil classification by particle-size characteristics, liquid limit, and plasticity index. It classifies naturally occurring mineral and organo-mineral soils in the laboratory. The classification depends on the amount of gravel, sand, and fines and on the plasticity properties of the fine-grained material. The main testing goal of ASTM D2487 is to establish a group symbol and group name that, in a general sense, relate to a soil’s engineering properties. The standard contains information on particle size analysis, Atterberg limits testing, and classification of plasticity chart.

The scope of ASTM D2166 includes: 

• Material type: Naturally occurring mineral (and organo-mineral) soils. 
• Purpose: Soil particle shape, particle-size distribution, and characteristics of each particle size. 
• Properties measured: Plasticity Index, Particle-size Distribution, Liquid Limit and Plastic Limit. 
• Method: Use appropriate procedure(s) for sieve analysis (Test Method D422) and Atterberg limits (Test Method D4318). 
• Result: Results may contain a group symbol (e.g., GW or CL), the group name, and additional particle-size and plasticity data.
• Test Limitations: ASTM D2487 is a qualitative classification only and should not replace quantitative testing for detailed structural design. 
• Environmental conditions: When a soil contains fines (5-12%), or when the soil is near a boundary on the plasticity chart, use dual or borderline symbols where applicable. 
• Applications: Applications include geotechnical site investigation, foundation design, embankment construction, and soil-aggregate classification. 

What are the Uses of ASTM D2487?

ASTM D2487 testing helps labs assign a uniform classification to soils found in a geotechnical investigation. Engineers then use the classification to compare soil behavior on a site and understand the suitability of soils for a specific application. This standard-

• Differentiates soils into gravel, sand, silt, clay and organic classes based on laboratory data.
• Gives engineering reports a group symbol and group name.
• Evaluates the properties of fine-grained soils that relate to their ability to be formed and molded.
• Helps to compare soil samples throughout a geotechnical investigation.
• Helps to educate staff on the visual-manual requirements of Practice D2488.
• Helps inform design decisions for the foundation, embankment, and pavement.
• Helps in the selection of material for the construction of a site for a specific soil condition 

Which materials can be tested under ASTM D2487?

This standard, ASTM D2487, evaluates the portion of the sample that passes the 3-in. sieve from naturally occurring mineral and organo-mineral soils. (75-mm) sieve. Depending on the sample type, the practice can classify soils from well-graded gravel to highly plastic clay and organic soils. Before starting to classify, an analyst should determine the particle size distribution and the plasticity properties of the fine-grained part.

Why is ASTM D2487 Important? 

ASTM D2487 defines a controlled classification procedure that relates soil group symbols to the probable engineering behavior of soils. Misclassifying soil leads to incorrect foundation, embankment, or pavement design decisions and expensive field problems. The results help the engineer compare soils in a project and to decide if a soil type will behave acceptably in the proposed application.

Other referenced ASTM documents include ASTM C117, C136, C702, D420, D421, D422, D653, D1140, D2216, D2217, D2488, D4083, D4318, D4427, and E11.

ASTM D2487 Testing Process and Data Collection

The analyst takes a representative sample from the soil and prepares it according to Practice D421. Technicians then conduct a sieve analysis test to find the percentage of gravel, sand, and fines, and also conduct Atterberg limits testing on the fine percentage. The operator plots the liquid limit and plasticity index on the plasticity chart and then uses the particle-size distribution to compare to the classification. Analysts record the appropriate group symbol, group name, and supporting information for the classification report.

Common Challenges and Troubleshooting

Particle-size results may be affected by improper sample preparation; therefore, technicians are careful when drying and separating the sample in Practice D421. The Casagrande device is also calibrated before each test, which can help eliminate an issue experienced with liquid limit testing: inconsistent readings. Some soils fall near the limits of a classification on the plasticity chart and require a dual or borderline symbol instead of a single classification; this is addressed by carefully plotting and verifying the liquid limit and plasticity index. These challenges are minimized throughout a testing program with regular equipment calibration and trained personnel.

• The laboratory reports the percentages of gravel, sand, and fines obtained by sieve analysis.
• The analyst records the liquid limit, plastic limit, and plasticity index of the fine-grained fraction.
• The laboratory indicates the group symbol (such as GW, SC, or CH) and the group name.
• A dual or border symbol, indicating a range of 5 to 12 percent fines, is entered on the report instead of a single overall value for the soil. 

Link to ASTM D2487