Point Load Test
The Point Load Test is a simple and widely used method for estimating the strength of rock samples. Here's a concise explanation of the test:
Purpose
- To quickly estimate the strength of rock specimens
- To provide an index value that correlates with uniaxial compressive strength
- To assess rock strength in the field or laboratory with minimal sample preparation
Key aspects
1.Equipment:
- Point load tester with conical platens
- Vernier caliper or measuring tape
- Calculator or chart for strength index calculation
2.Sample types:
- Core samples (diametral or axial test)
- Irregular lump samples
- Block samples
3.Test procedure:
- Measure and record sample dimensions
- Place sample between the conical platens
- Apply load gradually until the sample fails
- Record the failure load
4.Calculations:
- Point Load Strength Index (Is) = P / De² Where: P = Failure load, De = Equivalent core diameter
- Size-corrected Point Load Strength Index (Is(50))
- Correlation to Uniaxial Compressive Strength (UCS)
5.Advantages:
- Quick and simple to perform
- Minimal sample preparation required
- Portable equipment allows for field testing
- Can test irregular samples
6.Limitations:
- Less accurate than direct UCS testing
- Results can be affected by sample anisotropy and discontinuities
7.Applications:
- Rock mass classification
- Preliminary strength assessment
- Quality control in quarrying and mining