What are geotechnical investigations?
Good soil information is precious. It can lead to significant savings and firm foundations designs because the parameter designs are well defined. If the information is comprehensive, the structure built will be more economical, and it will be stronger. The objective of geotechnical investigations is to build a good building at a low price, and not to build a cheap building. These site investigations can cost up to two percent of the total project cost, but they are imperative at the end of the day.
Qualified geotechnical engineers do geotechnical investigations. These professionals have valuable knowledgeon the physical characteristics of any type of soil around the site of a proposed structure. Geotechnical investigations should also be carried out when measuring thermal capacity of soils and backfill materials that are essential for belowground transmission lines, gas and oil pipelines, solar thermal warehousing facilities and radioactive waste disposal. The geotechnical investigation includes surface exploration and also the subsurface geographic expedition of a site. Geophysical methods have always been used to get critical data about sites.
Geotechnical investigation procedures
Surface exploration can be done in several ways. These include geologic mapping, photogrammetry, and geographical methods. It can also be done by a geotechnical professional who walks around the site to carefully discover the physical stipulations of the site. To get the information concerning the soil conditions that are below the surface, underground exploration is compulsory. There are several ways of detecting the soils under the surface, getting samples and determining the physical properties. These include trenching, test pits, in situ and boring tests.
There are two types of borings: Large diameter and small diameter.
- The large diameter borings are not commonly used because they are not very safe, and they are quite expensive. They are however used to allow the professionals to manually and visually examine the rock and soil stratigraphy in situ.
- Small diameter borings are the most prevalent in the market. They are frequently used because they allow the professionals to examine the rocks or soil cuttings or to recover samples at depth and to conduct in place soil tests. The samples are extracted using soil samplers.
Types of soil samples
There are two types of soil samples: disturbed and undisturbed. The undisturbed soil samples are not always completely disturbed.
- The disturbed samples refer to the soils that the structure has been changed such that the tests of the morphologic properties of the sample are not representative of in situ conditions. In this type of samples, only the morphology of the soil particles can be determined accurately.
- Undisturbed soil samples are the ones where the stipulation of the soil in the sample are close to the pre-condition of the soil in situ such that it allows tests of morphological properties be used when approximating the features of the home soil in situ.
During offshore soil connections, the professionals have to deal with some difficult variables. When the waters are shallow, this can be done perfectly off a barge. When the waters are too deep, a ship is needed. Deep-water samplers are usually the Kullenberg type. There are some seabed samplers too, and these can push the sampling tube into the soil.
The soil samples can be acquiredeasily suing a variety of common samplers. Some of these samplers only provide disturbed samples, and other can provide undisturbed samples.
- Hand or machine using auger: this type of sampler contains a short cylinder that has a cutting hedge attached to a handle and a rod. It also has a duplication of downward and rotation force that makes it advanced. This sampler obtains the disturbed samples.
- Trial pit samplers: these are quite small machines or hand excavated tranches that are used to detect the groundwater levels and also take disturbed samples.
- Shovel samplers: using this type of sampler, the sample can be acquired by digging out everything from the site. This sampler gives disturbed samples.
- Spit spoon/ SPT sampler: this is mostly used in the known test procedure for the standard penetration test. It is also used in the Slit Barrel thieving/sampling of Soils. Most of the times, it is used for the non -cohesive soils, and the samples collected are disturbed.
- Continuous Flight Auger: this type of sampler uses an auger in place of corkscrew. The corkscrew is placed into the surface then lifted up. Some soil is left on the surfaces of the screw auger, and it is kept for investigation. The samples obtained by this sampler are disturbed.
- Modified Californian Sampler: this works like the SPT Sampler. It has a large surface area, and it is mostly lined on metal tubes for keeping the samples. The samples of soil obtained from this sampler are disturbed because of the large area of the sampler.
- Piston samplers: These types of samplers contain thin walled metal tubes that have a piston on the end. They are pushed into a borehole bottom, and the piston remains at the control surface of the ground. The tubes are supposed to slide past the piston. The samples of soil obtained from these samplers are undisturbed.
- Shelby Tube Sampler. This is mostly used during the Standard Practice for Geotechnical Purposes. The samples of soil obtained from this sampler are considered to be undisturbed.
- Pitcher Barrel : The method has a lot of similarities to the piston sampler, but it does not have a piston. It has pressure relief holes that are located close to the front surface of the sampler, and these are used to prevent the pressure from air or waterabove the soil from building up.
Several investigation tests could be done on soils to determine its properties. These soil properties are believed to be intrinsic to the constitution of the soil matrix, and this means that they may not altered by the sample disturbance. Several other properties mostly depend on the structure of the soil and its composition. These soils can be adequately tested on samples that are considered undisturbed. Some of the soil tests measure the direct features of the soil, and others measure the index properties that provide valuable knowledge concerning the soil without measuring the property directly.
You need a company with undoubted reputation for your geotechnical needs. Tempsand and South East soil testing are the most promising companies in this field. They are able to do geotechnical investigations and determine geotechnical engineering needs for your soil. Their senior staffs have been in this field for long. They bring to us vast experience that they have obtained while working in local government projects. They ensure proper investigations are done before embarking in any of your home projects. All you need is to contact them in any of your future projects. You can be assured of one thing, all your soil need will be covered and quality soil investigations are guaranteed.