ASTM D2321 Standard Practice for Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity-Flow Applications

Get Certified ASTM D2321 for Uncompromising Quality and Project Success 

Technicians verify that buried thermoplastic pipe installations satisfy the trench, bedding, and compaction requirements recommended by ASTM D2321 before putting them into service. Embedment soil classification, density of backfill, and pipe deflection are verified in accredited laboratories and through field inspection to document conformance to the project specification. This helps prevent pipe collapse, excessive deflection, and early failure in a buried sewer system. 

The scope of ASTM D2166 includes: 

• Material type: Flexible thermoplastic pipe (PVC, HDPE, PP) for sewers and gravity drainage. 
• Purpose: Instructions for installing pipes underground as part of a stable soil-pipe system. 
• Properties measured: Embedment soil classification, backfill lift thickness, compaction density, and pipe deflection. 
• Method: Identify appropriate soil class field testing procedures, such as compaction tests and deflection tests. 
• Result: Include compaction density (percent of maximum dry density), pipe deflection (percent), and soil classification in the results. 
• Test Limitations: ASTM D2321 does not specify product performance criteria such as minimum pipe stiffness, maximum service deflection, or long-term strength. 
• Environmental conditions: Where applicable, the practice considers native soil conditions, groundwater, and traffic loading over the pipe. 
• Applications: Sewer installation, storm drain, or other underground gravity flow pipelines. 

What are the Uses of ASTM D2321?

The ASTM D2321 verification process helps project teams ensure the soil support they achieve during a thermoplastic pipe installation supports long-term performance. Engineers then use the results to assess the installation and determine whether the pipe-soil system will withstand the stresses of burial and traffic loading. 

This standard-

• Classifies embedment soil to determine the type of bedding and backfill to use.
• Checks the compaction density of backfill around the pipeline area.
• Evaluates pipe deflections post-installation to ensure sufficient soil support.
• Supports comparisons of trench and bedding conditions in a project.
• Helps in the quality control of sewer and drainage pipeline construction.
• Helps to avoid over-compaction or under-compaction of backfill.
• Helps to select installation methods for different native soil conditions. 

Which materials can be tested under ASTM D2321?

ASTM D2321 is used to specify flexible thermoplastic pipe, which is composed of PVC, HDPE, PP, and other materials, for sewers and other gravity-flow systems. Provided an appropriate soil type for embedment is used, the practice informs installation in a variety of native soil and groundwater conditions. Before beginning a project, the analyst needs to decide ahead of time what kind of pipe is to be repaired, what condition the trench is in, and what type of soil is to be used for embedment.

Why is ASTM D2321 Important? 

The controlled trench, bedding, and compaction recommendations in ASTM D2321 are applicable to the installation of thermoplastic pipe. If the soil in which a pipe is buried is not adequate, or the compaction is improper, the pipe may bend or even collapse, causing the pipe to fail prematurely. The results help engineers to ensure that the soil-pipe interaction required for satisfactory long-term performance is present.

Other referenced ASTM documents include ASTM B557, E8/E8M, E34, E716, E1251, E3061, G47, B660, B661, B918, E29, E55, E88, E122, and E177.

ASTM D2321 Testing Process and Data Collection

Inspectors inspect representative sections of the trench and determine the type of embedment soil used for the project. These crews then clear and prepare the trench and bedding, install the pipe, and backfill around the pipe in controlled lifts. The compaction density is checked at periodic intervals with a nuclear density gauge or sand cone test, and pipe deflection is measured after backfill is placed. The field results are compared to the ASTM D2321 recommendations for the ordered soil class and the data entered into the project compliance report.

Common Challenges and Troubleshooting

If the pipe design requires a larger trench width, crews tend to limit the trench width to avoid lateral pipe deflection from excessive trench width when bedding and compaction do not support the additional load. Unstable or wet native soils can also compact during backfilling, and crews handle this by removing unsuitable soils and replacing them with soils that are suitable for embedding. Adequate compaction is required around the pipe to prevent damaging the pipe wall, and inadequate compaction can leave the pipe unsupported. Monitoring of compaction equipment and periodic testing of compaction density correct these problems. These challenges are minimized throughout a project by trained staff and regular inspections.

• The inspector returns the grade of the soil in which a pipe is embedded, the soil in the area where it is bedded, haunched, and backfilled.
• Analysts record compaction density as a percentage of the maximum dry density obtained from either the standard or modified Proctor reference values.
• The inspector records pipe deflection as a percentage of the pipe diameter after backfill has been placed.
• The report does not rate the overall performance of the pipeline, but compares field conditions to the ASTM D2321 recommendations and records whether conditions are adequate for soil support. 

Speed: The time needed to verify will vary based on the amount of pipeline installed and the number of trench sections to be density and deflection tested.

Cost: Saving money due to the cost of verification before backfilling is complete; ensuring soil support is adequate before spending costly amounts of time on excavation and repairs later on.

Confidentiality: Matestlab keeps the process confidential and only discloses results to respective stakeholders.

Link to ASTM D2321