Helical Probe Tests: Initial Test Calibration
Helical test probes of different sizes suitable for shallow (1.8-m) in-situ soil exploration and compaction control were developed and tested in different soils alongside traditional in-situ tests, including Standard Penetration tests (SPT), cone penetration tests (CPT), dilatometer tests (DMT), and in-situ density tests. The helical probe test (HPT) is a quick and economical test, which can be performed by a single person in less than 10 min, making it very attractive for construction field testing on geotechnical projects. The torque necessary to insert the probe is used as a measure of soil characteristics. Preliminary studies indicate that the HPT test correlates well with the SPT test and the correlation is not sensitive to the soil type (particle size); the HPT test correlates well with the CPT test, but the correlation is sensitive to the soil type; and the HPT/SPT and HPT/CPT correlations are consistent with existing data on SPT/CPT correlations. After site calibration, the HPT torque can be used to estimate relative compaction and in-situ density of compacted soils.