Ground investigation
Also called Geotechnical desk study, Trial pit, Plate bearing test, Standard Penetration Test, SPT, Site investigation
The process of establishing what the ground on a site is and what it can carry, running from a desk study of historical maps, geological records and previous reports, through trial pits and boreholes, to in-situ tests such as the plate bearing test and the Standard Penetration Test. It is where the allowable bearing pressure used to size crane mats and outrigger pads comes from.
In practice
The four stages answer progressively narrower questions. A geotechnical desk study reviews existing information before anything is dug, and flags risks such as made ground or historical structures. A trial pit is a shallow excavation giving direct sight of the soil profile — quick and cheap, but limited in depth. A plate bearing test loads a rigid plate and measures the settlement, assessing in-situ capacity and stiffness at one specific location. The Standard Penetration Test drives a sampler in a borehole under standard hammer blows and records the count as an N-value, indicating density and strength with depth.
Where this comes from: Standard UK ground investigation practice. This entry merges four inherited definitions — desk study, trial pit, plate bearing test and SPT — because each is a stage of the same process and none carries a distinct commercial link of its own.
Where it matters on site
For a lift, the question is whether any of this covered the ground under your set-up position, at the depth your loading reaches. Investigation is usually commissioned for the permanent works — foundations, deep and localised — and a crane standing between the pile positions may be on ground nobody looked at. Where it was not covered, that is a gap to name in the lift plan rather than a reason to interpolate.