The standard penetration test is an in-situ test that is coming under the category
of penetration tests.
The standard penetration test, commonly known as 'SPT', was developed to
provide geotechnical engineering properties for foundation design purposes. The
test is carried out within a borehole. The results can be used to determine the
relative density, bearing capacity, and settlement of granular soil.
The sampler is 51 mm O.D. (outside diameter) and it is driven into the soil
with a 63.5 kg weight having a free fall of 760 mm. The first 150 mm of soil is
neglected. The next 300 mm of soil constitutes the test. The number of blows for
that 300 mm becomes the N-value.