On occasion we oversee geoprobe investigations. Geoprobes developed as a less costly means of collecting soil samples for geotechnical and environmental purposes. Under the right geology circumstances they are a great approach for getting sub surface information. Essentially they are a hollow tube pushed into the ground and then pulled out with a sample of soil inside the tube. The wonders of hydraulics and extremely tough alloys do the trick.
Truck mounted geoprobe
Pushing the probe into the ground
Small tractor like rig. These types of rigs are great on steep slopes or inside buildings
Samples are collected in plastic tubes that can either be hauled back to the office or cut open at the site for sending off for chemical analyses.
On a recent project we probed through an upper unit of sand and gravel (fill) down into Bellingham Glacial Marine Drift. The Bellingham Drift was deposited towards the late stages of the last glacial period when the Puget ice lobe retreated out of the Puget low lands. The mass of up to 6,000 feet of glacial ice had pressed the local earth surface downward. As the ice retreated the sea flooded over the land that had been pressed down by the ice such that the ice lobe was for a time floating on inland sea. The melting ice rained a steady load of finely ground rock silt and clay onto the sea floor below as well occasional pebbles, cobbles and boulders. This phenomenon was most pronounced in the Bellingham area as the ice had been thicker here than areas to the south and the glacial ice lingered longer in this area; hence, the name Bellingham Drift.
Where the drift has remained saturated it is very soft - a bit stiffer than tooth paste. A bit of a challenge for constructing big heavy buildings but pretty good at preventing the movement of contaminants as long as it is the silt/clay variety of the drift.
Geoprobe core samples of soft Bellingham Drift
I have a habit of making balls out of the extra sample material.
More skilled geos might shape figures