Measurements are made to determine the physical characteristics of geological materials. This is done by placing a homogeneous sample in specialized equipment designed to measure that particular property under either controlled or in-situ conditions.
Extracting an intact sample is essential for testing of geological materials in controlled conditions.
The material – rock or soil – is obtained using a set standard of care intended to preserve the in- situ properties (such as structure, water content, or density) that are relevant to the particular tests. This is frequently accomplished through some variety of core drilling machine such as that manufactured by The Testwel Instruments Company.
The advantages of laboratory testing is the ability to measure the particular characteristics of the sample uncontaminated by ambient noise. The disadvantage of laboratory testing is that some physical properties change when removed from their in-situ environment, and extracting a sample is destructive. Particular care must be taken when determining the correct sample dimensions for size-dependent mechanical properties, like strength, where the specimen size strongly influences the characteristic.
Examples of physical characteristics that are measured in a laboratory setting, and the machines used to make those measurements Matest Hoek cells used to measure permeability, the Barrington Instruments MS3 for measuring magnetic susceptibility, and triaxial cells for measuring volumetric elasticity to determine the bulk modulus of a material.