SPT results are in-situ field measurements, and not as subject to sample disturbance, and are often the only test results available, therefore the use of correlations has become common practice in many countries. CS1 maint: In certain circumstances, it can be useful to continue driving the sampler beyond the distance specified, adding further drilling rods as necessary.
Weight of hammer used in this test is; Q. If the samples are found to be unacceptably disturbed, it may be necessary to use a different method for measuring strength like the plate test. Campanella, A.