How do you perform the main types of soil tests?

1 Field tests

Field tests are conducted on site to obtain quick and approximate results of the soil conditions. These tests are particularly useful for preliminary investigations, quality control, or emergency situations. Visual inspection involves observing the soil color, texture, structure, and consistency by eye or with simple tools like a pocket knife or a penetrometer. This can help identify the soil type, moisture level, and presence of organic matter or contaminants. Additionally, the moisture content and density can be measured by using a portable device that heats and weighs the sample, or by using a hand-held moisture meter that measures the electrical resistance of the soil. An in-situ vane shear test can also be used to measure the shear strength of soft or cohesive soils by inserting a four-bladed vane into the ground and rotating it at a constant rate. The torque required to cause failure is recorded and converted into shear strength.

2 Laboratory tests

Laboratory tests are conducted in a controlled environment to obtain accurate and reliable results of the soil properties. They are useful for detailed investigations, design, or verification purposes. Some of the most common laboratory tests include sieve analysis, Atterberg limits, consolidation test, and triaxial test. Sieve analysis can help classify the soil and estimate its permeability and compaction characteristics. Atterberg limits measure the moisture content at which the soil changes from one state to another and can help define the consistency and behavior of fine-grained soils under different moisture conditions. Consolidation test measures the settlement and compression of the soil under a given load over time, while triaxial test measures the strength and deformation of the soil under different combinations of axial and lateral stresses. All these tests can help estimate settlement and bearing capacity of the soil, as well as determine stress-strain relationship, failure envelope, and shear strength parameters of the soil.

3 Geophysical tests

Geophysical tests are non-invasive methods that use physical phenomena, such as sound, electricity, or magnetism, to explore the subsurface features of the soil. These tests are useful for mapping the soil layers, detecting anomalies, or locating utilities. Seismic refraction involves generating a seismic wave by hitting the ground with a hammer or an explosive and recording the arrival time of the wave at different distances with geophones. This can help determine the thickness and stiffness of the soil layers and identify the bedrock or groundwater level. Electrical resistivity involves inserting electrodes into the ground and applying a voltage between them while measuring the current and potential difference. This can help identify soil type, moisture content, salinity, and presence of cavities or metallic objects. Ground penetrating radar uses the emission and reflection of electromagnetic waves to create an image of subsurface structures of the soil. This involves moving a radar antenna along the ground and recording the amplitude and time of reflected waves. It can help detect boundaries, fractures, voids, or pipes in the soil.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?