SPT Testing vs. CPT Testing
Standard Penetration Test (SPT) is a low-cost and straightforward testing procedure widely used in the geotechnical examination to determine the relative density and angle of shearing resistance of cohesionless soils and also the strength of stiff cohesive soils.
If you’ve been following the CPT University, you likely already know that Cone Penetration Testing isn’t the only method of testing soil.
Mud rotary drilling, for example, has come up in the past along with one of the best-known soil testing procedures out there: the Standard Penetration Test (SPT). Like Cone Penetration Testing, SPT Testing is widely used. But can it outperform CPT Testing? Read on to find out.
What is SPT Testing?
SPT Testing uses a thick sample tube to determine the relative density of granular deposits, typically sand and gravel.
The sample tube is placed at the bottom of a borehole and struck with a heavy slide hammer repeatedly. The number of hammer strikes is important; the test operator must track how many strikes it takes to drive the sample tube 6 inches into the soil.
The test is completed when the sample tube reaches 18 inches deep.
As you might imagine, a test that requires only a sample tube and a hammer offers a few notable benefits, namely that it is simple and inexpensive to perform.
It is also the best solution for testing soil in areas that are difficult to access with vehicles. In other words, if you need to perform a soil test quickly, easily and at minimal cost, SPT Testing is hard to beat.
SPT Testing does have its drawbacks, though. Most notably, it’s inaccurate compared to more advanced methods, especially when sampling coarse sands or clay. As such, it’s rare to encounter a scenario in which SPT Testing is preferable to Cone Penetration Testing.
Not only is CPT far more accurate than the standard penetration test, it also manages to be relatively inexpensive compared to other testing methods. CPT is also a fast, safe and versatile option.
For example, Vertek’s S4 CPT Push System is a robust, affordable push system that is compatible with any commercial skid steer, meaning it is capable of providing superior soil testing almost anywhere SPT Testing can be performed.
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