Geotechnical engineering and testing involve gathering and collecting information about the physical properties of foundations and soil earthworks that are to be used for different structures or even for repairing distress to structures and earthworks as a result of subsurface conditions. Basically, the investigation is aimed at understanding the features of the underneath work site. The specialists that perform this type of investigation are engineering geologists, geotechnical technicians, and geotechnical engineers.
Geotechnical engineering and testing are integral aspects of planning and construction, whether it’s for a building, an infrastructure, or any other project that involves different structural types. Examples include beach nourishment, land reclamation, excavation pit, bridges, road, foundations and many more. Geotechnical engineering and testing are all about understanding subsurface conditions.
Often referred to as site investigation, it is also used in measuring the thermal resistivity of backfill materials or soil that is used in underground transmission lines, gas or oil pipelines, solar thermal storage facilities, and radioactive waste disposal. The investigation may also include geophysical methods involved in obtaining data for use on different sites, collecting soil samples, and carrying out various tests on the retrieved soil samples.
The importance of these investigations cannot be overemphasized, especially before constructing buildings. Whether it’s your house you’re building, a multiplex, a warehouse, a shopping mall, an industrial shade, or any other type of building, it always requires geotechnical engineering and testing. Today, there are several industries across different parts of the world that perform geotechnical engineering and testing using different machines. Surface exploration may include photogrammetry, geophysical methods, and geologic mapping, and in some cases, it may simply involve geotechnical professionals walking to different parts of the site to physically examine the site and its physical conditions.
Types of Geotechnical Engineering and Testing
As mentioned earlier, geotechnical engineering and testing is mostly carried out by laboratory testing, site characterization, and professionally interpreting the data. After following these procedures, the design and construction can be carried out with ease.
The tests that are carried out belong to 4 different categories. These are trenching, in situ testing, boring, and test pits. We’ll go through these categories below:
1.   Test Pits
As the name suggests, it involves digging a pit, either with the aid of an excavator or manually, to have a proper view of the subsurface conditions. The pit is dug to the desired depth for proper analysis. This testing is mostly used for shallow foundations.
2.   Trenching
This shares some similarities to test pits, but for trenching, it involves digging elongated pits, and this is over a distance. The aim is to show the changes in subsurface conditions over different parts of the site. Trenching also enhances the identification and characterization of sedimentary changes across different parts of the site and over a long distance. Different soil samples can be used for extracting the samples in the test pits for visual identification and lab analysis.
3.   Boring
Borings are mostly employed by utilizing a drill crew or a drill rig, and the diameter often varies. It also makes it easier to assess density through standard penetration testing. The aim is to physically remove rock and soil samples for testing and assessment. This type of geotechnical engineering and testing allows for observing extracted materials and for assessing the field density. For the tests mentioned earlier, the samples are only evaluated after they are taken to the lab. Boring on the other hand makes it possible to use piezometers to assess and test groundwater tables and seasonal fluctuations.
4.   In Situ Testing
This type of geotechnical engineering and testing involves the use of different penetration tests, among which includes
- Standard Penetration Tests (SPT) involving penetration by percussion-based investigation techniques, drilling, various static direct push, and sonic vibratory drilling methods
- Cone Penetrometer Testing (CPT)
The advantage of in situ testing over the other types of testing we’ve mentioned earlier is that it offers a more accurate assessment of the subsurface conditions. With this, it becomes a lot easier to obtain a more informed geotechnical design and data analysis.
It is important to always specify the right test for the right situation and also to use multiple tools in order to develop a more accurate assessment and data for the subsurface strata. Reducing uncertainties can also be done by having a proper understanding of the different testing methods, as well as the advantages of each testing method.
Frequently Asked Questions
Here are answers to some frequently asked questions:
What are the geotechnical testing types?
The testing methods are basically used in obtaining information about the physical properties of rock, soil, and substrate in a construction site.
The types of soil tests used for building construction are:
- Compaction test
- Dry density of soil
- Specific gravity of soil
- Atterberg limits tests
- Moisture content test
What is geotechnical testing used for in construction?
Geotechnical testing is carried out to assess subsurface materials and conditions and also to determine the chemical and physical properties of materials. It is also carried out in evaluating soil and slope deposits and in assessing different risks posed by design foundation and site conditions. These tests are mostly carried out before commencing construction projects.
Who uses geotechnical testing?
The main people that use these testing are geotechnical engineers, and the main tests that are used are tests like cone penetration test (CPT), which is used in estimating the end bearing resistance and the amount of skin available in the subsurface. The different types of foundations include caissons, drilled shafts, earth-stabilized columns, piers, and piles. In addition to geotechnical engineers, geotechnical technicians and engineering geologists are also specialists that use geotechnical engineering and testing frequently.
Why is geotechnical testing performed?
There are so many reasons why geotechnical testing is performed. As mentioned earlier, geotechnical testing is performed by geotechnical technicians, engineering geologists, and geotechnical engineers. The aim is to have a detailed understanding of the different characteristics of underneath work sites. These are mainly the existing physical properties of these sites.
