The days when drilling projects revolved around rough estimates and an attitude of “that will do” are finished. Today, the need for accurate and precise measurements is paramount. A method that geotechnical site investigation companies can use, to ensure high quality and fastidious practice, is sample testing. There are numerous methods available to collect and examine samples, and each is dependent on the site in question.
Standard Penetration Testing (SPT)
Across the globe, standard penetration testing (SPT) is the most common form of exploration and sampling test used within the drilling industry. SPT involves hammering a thick-walled sample tube into the substrate at the base of the borehole. Following this, we can calculate the N-value by considering how many hammer blows were needed to move the tube a predetermined distance.
The main reason that SPT is one of the favourited techniques is the accuracy of the resulting density figures from both sand and gravel deposits. This form of sample testing is also inexpensive and easy to perform, whilst resulting in precise data.
Cone Penetration Testing (CPT)
One of the standard sample testing methods is known as cone penetration testing (CPT). The process involves inserting an instrumented cone at a controlled rate, downwards through the ground. CPT is used to determine the characteristics of the soil, such as the relative density, the dynamic and static pore pressure, as well as the stratigraphy of the soil. Similar to standard penetration testing, CPT is also easy conduct and is a cost-effective technique, with the addition of providing real-time testing.
Piston sampling is a method used for the more cohesive soil-types and is one of the techniques available to use for open boreholes. It is used to sample clays, silts and sands. The benefits of piston sampling include its easy operation as well as its quick profiling results. In addition, this method can be used to carry out sample testing below the groundwater table.
The U100 sample testing system is useful in situations where soft ground is involved, such as gravel, silt, sand or clay. The system usually comprises of a steel body tube, core catcher, spacing ring, and a hardened drive shoe. A PVC plastic liner is often used in conjunction to ensure the samples from weak soils are disturbed at a minimum level. U100 sampling can be carried out at depths between 30 and 40 metres below the surface!
At Borehole Solutions, we can also offer UT100 testing, which is a similar method to that described above. However, the UT100 sampling tube offers a thinner profile in comparison to the U100 system.
Vane Shear Testing
Vane shear testing is a prominent method used in the UK due to the geology mainly comprising of clay-type formations. The purpose of this method is to provide an estimate of the shear undrained strength of the sample. Vane shear testing involves inserting the vane into the ground and rotating it, resulting in recording the torque needed to cause soil failure. This is then converted into a shear strength reading. The vane shear test provides reliable data in an efficient matter, whilst the equipment is highly portable and easy to operate.
Sample testing helps to ensure the quality of both the site being investigated as well as the samples collected. For this reason alone, it is of vital importance to carry out as a lack of testing can lead to serious consequences! At Borehole Solutions, we offer accurate testing services with our expert drilling team. If you would like to find out more, then get in touch with us today!