ASTM D2850 Standard Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils

Get Certified ASTM D2850 Triaxial Compression Testing

ASTM D2850 testing helps geotechnical engineers, contractors, laboratories, and other professionals evaluate the undrained strength of cohesive soils. Analysts prepare representative specimens and place them in a calibrated triaxial compression testing system. Technicians apply the specified confining pressure and perform the axial loading under undrained conditions. The laboratory documents the stresses applied to the specimen, deformation, and the specimen’s response, and determines applicable strength parameters based on the test data.

• Cohesive Soils: Technicians evaluate cohesive soil specimens under controlled triaxial loading conditions.
• Undrained Testing: The test prevents drainage during the shear stage to evaluate soil behavior under undrained conditions.
• Confining Pressure: The apparatus applies controlled pressure around the cylindrical specimen before axial loading.
• Axial Loading: Technicians apply axial load to the specimen under the specified test conditions.
• Shear Strength: Engineers use the measured stress response to determine the soil’s undrained shear strength.
• Soil Comparison: Laboratories can compare the strength behavior of suitable cohesive soil specimens under the specified test conditions.

What are the uses of ASTM D2850 testing?

ASTM D2850 provides geotechnical information that can be used to improve engineering understanding of the strength behavior of cohesive soils when loaded undrained. Results help in characterizing soils, analyzing structural properties, and making design decisions. The method-

• Determines the undrained shear strength of cohesive soil.
• Evaluates soil response under controlled triaxial compression.
• Supports foundation and embankment design.
• Helps engineers assess cohesive soil for slope and stability analysis.
• Provides data for geotechnical site investigations.
• Supports comparison of soil samples from different locations or depths.
• Helps engineers evaluate soil behavior under short-term loading conditions.

Which materials can be tested according to ASTM D2850?

ASTM D2850 is for cohesive soil specimens that comply with the specifications of the test method. The soil parameters, condition of the samples, their dimensions and conditions of the tests should be verified in the laboratory before testing.

• Cohesive Soils: Evaluates suitable cohesive soil specimens under unconsolidated-undrained conditions.
• Undisturbed Soil Samples: Can provide strength information when representative undisturbed specimens are available and suitable for testing.
• Remolded Soil Specimens: Applicable prepared soil specimens can be evaluated when the test requirements permit their use.
• Laboratory-Prepared Specimens: Technicians can prepare specimens according to the applicable requirements for controlled soil evaluation.

Why is ASTM D2850 testing important?

In cohesive soils, strength can vary with drainage and loading. The ASTM D2850 standard offers a standardized approach for measuring soil resistance in a controlled environment where soil is not drained during the shear phase. The results aid engineers in understanding the undrained response of cohesive soil and in providing strength data for geotechnical analysis. The data can be useful for engineers in designing foundations, checking slopes, evaluating embankments, and other short-term loading applications.

ASTM D2850 Testing Process and Data Collection

Technicians first identify the soil sample and prepare a representative cylindrical specimen. They measure the specimen dimensions and inspect its condition before mounting it in the triaxial cell. The laboratory then applies the specified confining pressure without allowing consolidation.

The apparatus applies axial loading while maintaining undrained conditions. Technicians monitor axial deformation and the applied stress throughout the test and record the specimen response. Engineers analyze the collected data to determine the applicable undrained shear strength and other required test results.

Common Challenges and Troubleshooting

Specimen disturbance, incorrect dimensions, inadequate sealing, leakage, pressure-control errors, loading conditions, and equipment calibration can affect ASTM D2850 results. Handle soil samples carefully and disturb them as little as possible during specimen preparation and mounting. The specimen testing system needs to be checked before loading in the laboratory. The technician checks the pressure indicator, checks the seals and connections, and verifies that the other miscellaneous equipment is working correctly. 

• ASTM D2850 provides undrained shear strength results based on the specimen response under undrained conditions.
• Laboratories report confining pressure in kPa or MPa and axial stress in kPa or MPa.
• Laboratories report axial strain as a percentage (%) and specimen height and diameter in mm.
• The report includes the soil identification, specimen condition, test pressure, loading conditions, and failure response.
• Consistent specimen preparation, accurate pressure control, proper drainage conditions, and calibrated testing equipment help laboratories produce reliable and comparable results.
• Engineers use the results to compare cohesive soil strength, evaluate undrained behavior, and support geotechnical design and analysis. They should interpret the results together with specimen condition, soil characteristics, confining pressure, and other applicable test conditions.

Link to ASTM D2850