Why laboratory testing is needed
Field descriptions provide valuable information, but many soil properties cannot be determined reliably by visual observation alone. Laboratory testing allows selected properties to be measured using a defined procedure and related back to a known sample depth.
Water content
Water content measures the amount of water in the sample relative to the dry soil mass. It is a basic result that is often considered alongside soil consistency, unit weight and other laboratory observations.
Unit weight
Unit weight describes the weight per unit volume of a specimen. The usefulness of the result depends on how the specimen was recovered, preserved and prepared, because disturbance can affect the measured condition.
Atterberg limits
Liquid limit and plastic limit are used to describe the plasticity characteristics of fine-grained soil. Together with particle-size information, they are commonly used in soil classification systems and in engineering interpretation of clayey and silty materials.
Sieve analysis
Sieve analysis determines particle-size distribution over the size range covered by the selected sieves. The result identifies the proportions of coarse fractions and supports soil classification.
Unconfined compression
For suitable cohesive specimens, the unconfined compression test measures compressive strength under the specified procedure. Sample quality is important, so not every recovered sample will be suitable for this test.
Compaction and CBR testing
Compaction and California Bearing Ratio testing are commonly associated with earthwork and pavement-related material evaluation. These tests have different sample-quantity and preparation requirements from routine borehole sample testing and should be scoped separately when required.
How to choose the test schedule
The test program should follow the project specification and the engineering questions that need to be answered. Soil type, sample condition, sample quantity and depth distribution all influence which tests are meaningful. Test selection should match the project requirements rather than applying every available test to every sample.