The Process Soil Testing

April, 30 2021

What is soil testing?

Generally, soil testing is performed to test the bearing capacity. The process reveals the physical and engineering properties of soil to help determine the type of foundation to be laid for construction. To ensure you understand the process, it’s wise to hire ground engineering consultants to guide you on all aspects of soil testing.

Importance of soil testing for construction

a. Allows you to determine the suitability of your soil and its ability to accommodate your construction.

b. Tests your soil for compaction, contamination, strength, organics, density, and sand content and how they can impact your construction.

c. Ensures you can obtain precise results while observing the soil’s development throughout the construction project and guarantees maximum safety and quality.

d. Allows you to collect and gather technical and safety data reports to support license applications and planning permissions.

The Soil Testing Process

The soil testing process first begins with sampling and preparation. Your provider uses sampling equipment such as extruder kits, sample tubes, or soil lathes to collect soil samples from different depths. For tests requiring standard cylindrical specimens like triaxial, sheer, and unconfined compression, specimen trimmers are used, allowing the precise trimming of soil samples. If more tests are required, crushing of soils is minimized or avoided. After sampling and preparation, various tests are conducted in a laboratory or the field. These tests include:

1) Site Investigation:

Preliminary Site Assessment: Before any soil is touched, engineers conduct a preliminary assessment of the construction site. They gather historical data about the area, such as previous land use, geological maps, and reports of nearby geological events. This helps in forming an initial understanding of the potential geological challenges.

Geological Surveys: Geologists may conduct surveys to determine the soil’s composition, rock layers, and any potential geological anomalies. This phase often includes identifying the location of groundwater tables and assessing the risk of soil erosion or landslides.

Topographic Surveys: Topographic surveys are conducted to map the surface features of the site, such as hills, valleys, and slopes. These surveys help engineers assess the site’s suitability for construction and the impact of topography on drainage and foundation design.


2) Sampling:

Depth-Specific Sampling: Soil samples are collected from multiple locations across the construction site, and samples are taken at various depths. Augers, drilling rigs, or excavators are used to extract soil cores. These samples provide a vertical profile of the soil composition and properties.

Undisturbed Samples: Special care is taken when collecting undisturbed soil samples, which preserve the soil’s natural structure and moisture content. These samples are crucial for accurate laboratory testing.


3) Laboratory Testing:

Moisture content test: Moisture testing is the most critical soil test and is usually determined by the oven-drying method, which is the most accurate and standard method. It involves placing a weighed sample of soil in the oven and drying it at 110+5oC. The soil is taken out after 24 hours, and the difference between the two weights is the moisture content of the soil.

Specific gravity test soil: This test is commonly determined by the density bottle method or pycnometer method, which determines the unit weight of soil solids to that of water. The value should range between 2.65 and 2.85.

Atterberg limits test: This measures the critical water content of a fine-grained soil, and it provides three limits for calculation – Liquid limit, plastic limit, and shrinkage limit.

Dry density test on soil: This is the weight of soil particles in a given sample, and it’s classified into dense, medium dense, and loose.


4) Analysis and Interpretation:

Bearing Capacity Analysis: Engineers analyze the laboratory test results to determine the soil’s bearing capacity, which is the maximum load it can support without failure. This information is crucial for foundation design.

Settlement Analysis: Settlement potential is evaluated to predict how much the soil will compress under the weight of the structure. Engineers use this data to ensure that post-construction settlement remains within acceptable limits.

Liquefaction Assessment: In seismic-prone areas, engineers assess the soil’s vulnerability to liquefaction during an earthquake. This involves evaluating the soil’s cohesion and the presence of loose, water-saturated layers.


5) Reporting:

Comprehensive Soil Report: A detailed soil report is generated, presenting all findings from the laboratory tests and analyses. This report includes soil profiles, recommendations for foundation types, bearing capacity values, settlement predictions, and any specific construction considerations based on the soil’s properties.


6) Design and Construction:

Foundation Design: Armed with the soil report, engineers proceed to design the most appropriate foundation system, whether it’s shallow foundations, deep foundations, or specialized systems like piles or caissons.

Construction Execution: During construction, the soil recommendations and design specifications outlined in the soil report are followed meticulously to ensure the structure’s stability and longevity.


In conclusion, the soil testing process is a comprehensive and meticulous endeavor that involves extensive investigation, sampling, laboratory analysis, and interpretation. It provides essential data for engineers and builders to make informed decisions and design foundations that can withstand the unique challenges presented by the soil beneath each construction site.

Contact G3Soilworks and maximize the productivity and profitability of your projects in Southern California by working with our expert geotechnical and geological experience. As ground engineering consultants, you can trust us to guide you accordingly.

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