The Various Visual And Manual Soil Testing Methods

Many soil testing methods can be used to determine the quality of the soil. This blog post will discuss two common methods: visual and manual. Visual testing is a quick and easy way to get an idea of the general condition of the soil. Manual testing is more detailed and can help identify specific issues with the soil. Both of these methods are important for contractors who are excavating land for a construction project.

Visual Tests

Visual tests are an important part of soil testing and can provide valuable insight into the condition of the soil. Visual tests involve examining a sample of soil’s appearance and physical characteristics. They can identify problems with soil texture, colour, compaction, drainage, surface crusting, salinity levels, nutrient levels, pH and more.

To conduct a visual test, collecting a soil sample from the area of interest is important. The sample should be taken in an area representative of the rest of the soil in that location. A shovel or garden trowel can take a sample of about one pint. The surface layer should be scraped away, and the sample should be placed in a clean, dry container.

Visual testing involves looking at the soil and the area around the excavation site for signs of instability. The competent person might do visual tests such as the following:

• Observe the soil as it is excavated. Soil that remains in large clumps when excavated may be cohesive. Soil that breaks up easily is granular.
• Examine the particle sizes of excavated soil to determine how they hold together.
• Look for cracks or fissures in the faces of the excavation.
• Look for layers of different soil types and the angle of the layers in the face of the excavation that may indicate instability.
• Look for water seeping from the sides of the excavation.
• Look for signs of previously disturbed soil from other construction or excavation work. Consider vibration from construction activity or highway traffic that may affect the stability of the excavation.

Manual Tests

Manual testing involves evaluating a soil sample from the excavation to determine qualities such as cohesiveness, granularity, and unconfined compressive strength. Soil can be tested either on-site or off-site but should be tested as soon as possible to preserve its natural moisture.

Manual soil test methods are widely used to determine soil samples’ physical and chemical properties. These tests indicate a soil sample’s composition, fertility, pH, and other aspects. Manual tests can be done on-site with basic tools such as trowels and spoons or in a laboratory using specialized equipment.

Manual Test Examples

Plasticity test: This is sometimes called the “pencil test.” Shape a moist soil sample into a ball and try to roll it into threads about 1/8-inch in diameter. Cohesive soil will roll into 1/8-inch threads without crumbling.

• Dry strength test: Hold a dry soil sample in your hand. If the soil is dry and crumbles on its own or with moderate pressure into individual grains or fine powder, it’s granular. If the soil breaks into clumps that are hard to break into smaller clumps, it may be clay combined with gravel, sand, or silt.
• Thumb penetration test: This test roughly estimates the unconfined compressive strength of a sample. Press your thumb into the soil sample. If the sample resists hard pressure, it may be type A soil. If it’s easy to penetrate, the sample may be type C.
• Pocket penetrometers: offer more accurate estimates of unconfined compressive strength. These instruments estimate the unconfined compressive strength of saturated cohesive soils. When pushed into the sample, an indicator sleeve displays an estimate in tons per square foot or kilograms per square centimetre.