If the pandemic has taught us anything, it’s not the importance of sample testing, as one would assume from the title of this blog; but that nothing stays the same. Time changes everything and the geotechnical sector is not an exemption to that rule.
Historically, people would drill with the mentality of ‘that will do’ and worked on estimates rather than accuracies. However, we are now in an industry which has evolved to heavily rely on precision and watertight measurements. Just one way in which you can ensure quality and fastidious practice is through sample testing. There are of course numerous ways in which samples can be taken and examined, and each one is according to the site in question. Today, we will be discussing various in-situ situations that emphasise the importance of sample testing.
Standard Penetration Testing
Globally, standard penetration testing is the most well recognised form of exploration and sample testing used in the drilling trade. The way that standard penetration testing works is by hammering a sample tube (thick walled) into the substrate at the base of a borehole. From here, we calculate an N-value by considering how many hammer blows are required to move the tube a predetermined distance. The reason that standard penetration testing is so widely used is that the density figures are accurate – based on gravel and sand deposits. It is inexpensive, and easy to carry out as a test, which only adds to its popularity.
Cone Penetration Testing
Cone penetration testing is a standard method of testing samples. The process involves placing an instrumented cone through the ground at a controlled pace. This is an image those inside and indeed outside of the drilling industry have commonly seen so will be familiar to many of you. This testing process is carried out in order to determine the individualities of the soil. These characteristics could include: the stratigraphy of the soil, static and dynamic pore pressure, and the relative density of the soil. Much like standard penetration testing, cone penetration testing is an easy test to conduct and inexpensive. Furthermore, it does offer the benefit of real time testing.
U100 testing is useful in situations where the ground is very soft, such as if it is comprised of clay, gravel, silt, or sand. Typically, the system is made up of a steel body tube, a spacing ring, a core catcher, and a hardened drive shoe. A PVC plastic liner is often used in order to keep disturbance to a minimum. The tube is driven straight into the ground to get the sample. This method is used when you don’t want the ground to be undisturbed, hence the “u”.
Piston test sampling is for cohesive soil and is one of one of the methods that can be used within an open borehole. The benefits of piston sampling is the ease of sampling and quick profiling results. Additionally, sample testing can be carried out below the groundwater table.
As you can see, the importance of sample testing cannot be ignored. The methods above are certainly not exhaustive, and our experts here at Borehole Solutions do offer other options. Our sample testing ensures quality and accuracy. For more information, please click here to get in touch with one of our experts.