WorldWide Drilling Resource

38 JANUARY 2023 WorldWide Drilling Resource® Four Types of Geotechnical Testing Adapted from Information by Vertek An essential part of planning and constructing projects - including foundations, roads, bridges, excavation pits, land reclamation, beach nourishment, and more - is knowing subsurface conditions. Testing is carried out by geotechnical engineers, geotechnical technicians, or engineering geologists to understand physical properties and other characteristics beneath a work site. The nature and extent of these investigations depend on the structure’s type and size, along with expected ground conditions. Testing is conducted by site characterization, laboratory testing, and professional interpretation of data. Tests generally fall into four categories: test pits, trenching, boring, and in situ testing. Test Pits - Much like it sounds, a pit is dug either manually or with an excavator to reveal subsurface conditions to the depth desired. Generally, this method is used for siting shallow foundations. Trenching - Trenching is similar to test pits, except in this case, the pit is elongated over some distance to establish how subsurface conditions change over various parts of the work site. This technique allows for identification of different sedimentary changes over a longer distance. Generally, soil samples from test pits and trenching are taken to a lab to be evaluated. Boring - Borings, usually deployed by a drill rig and crew, can vary in diameter and provide an opportunity to evaluate density through Standard Penetration Testing (SPT) to physically remove soil or rock samples for assessment and testing. Borings provide the advantage of assessing field density and allowing close observation of materials extracted. They also offer the opportunity to set piezometers on-site to assess seasonal fluctuations in the groundwater table. In Situ Testing - These methods include penetration tests such as SPT, which penetrate via drilling; percussion-based investigation techniques; sonic vibratory drilling methods; and various static, direct-push Cone Penetration Testing (CPT). In situ testing provides advantages of generating a more accurate assessment of subsurface conditions, allowing enhanced data analysis and informed geotechnical design. The right test should be specified for the right situation and multiple techniques may be employed depending on the site. Understanding different testing methods and benefits of each can significantly reduce uncertainties about future construction. A drilling company conducts CPT. C&G

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