Point Load Testing

What is Point Load Testing?

Point Load Testing (PLT) is an index test used to determine the strength of rock material. The test involves compressing a rock sample between two conical steel platens until it fails. The load required to fracture the specimen is then used to calculate the Point Load Strength Index ($I_{s(50)}$). This index provides a valuable indicator of the unaxial compressive strength (UCS) of the rock, which is particularly useful in the early stages of site investigation and for characterising rock masses.

Purpose and Applications of Point Load Testing

The primary purpose of Point Load Testing is to provide a quick and economical assessment of rock strength. Its applications are diverse and include:

• Classifying rock material based on its strength.
• Providing preliminary data for geotechnical design of foundations, slopes, and underground excavations.
• Assessing the variability of rock strength across a site.
• Estimating Uniaxial Compressive Strength (UCS) when core samples for laboratory testing are limited or unavailable.
• Quality control during quarrying and mining operations.
• Assessing the degree of rock weathering or alteration.

The Point Load Test Procedure

The Point Load Test is typically performed in accordance with established standards such as AS 4133.4.1 or ISRM suggested methods. The general procedure involves:

1. Sample Preparation: Rock samples can be tested in various forms, including drill core (diametral and axial tests), cut blocks, or irregular lumps. Samples are selected to be representative of the rock mass.
2. Measurement: Key dimensions of the specimen are accurately measured before testing.
3. Loading: The specimen is placed between the portable Point Load Tester's conical platens. The load is applied steadily until the specimen fails, typically within 10 to 60 seconds.
4. Recording: The failure load (P) and the distance between the platen contact points (D) are recorded. For core samples, the diameter is used. For other shapes, an equivalent core diameter (\\(D_e\\)) is calculated.

Standards & Equipment

Advantages of Point Load Testing

Point Load Testing offers several distinct advantages:

• Portability: The testing apparatus is lightweight and portable, allowing for on-site testing in the field, reducing delays and costs associated with transporting samples to a laboratory.
• Cost-Effective: It is a relatively inexpensive test compared to laboratory Uniaxial Compressive Strength (UCS) testing.
• Rapid Results: The test can be performed quickly, providing immediate strength data for site characterisation.
• Versatile Sample Types: It can be performed on irregular rock lumps and cores that may not be suitable for standard UCS testing.
• UCS Estimation: Provides a reliable method for estimating UCS, especially useful for preliminary design or when extensive lab testing is not feasible.

How Atlas Engineering and Technology Group Can Assist

At Atlas Engineering and Technology Group, our geotechnical professionals are highly experienced in conducting Point Load Tests in Sydney and surrounding regions. We adhere to Australian Standards (e.g., AS 4133.4.1) and international best practices to ensure the highest quality results.

We provide:

• On-site testing capabilities for rapid assessment.
• Detailed analysis and interpretation of \\(I_{s(50)}\\) values.
• Correlation of Point Load Test results with other geotechnical parameters.
• Clear and concise reporting to support your project's design and construction phases.
• Expert advice on the implications of test results for your specific project.

Deliverables

• NATA-endorsed PDF report (Is, Is₅₀, UCS correlation graphs)
• Excel data sheet with raw and normalised results
• High-resolution failure mode photographs