Hollow Stem Auger
The hollow stem auger is recognized as a versatile, fast and effective tool for advancing the bore hole. Once the depth is achieved, the center stem of the auger is quickly removed which allows for work inside the auger using coring tools, soil sampling equipment or environmental monitor well installations.
With wire line drilling, a barrel of core can be removed from the bottom of the hole without removing the rod string. When the driller wants to remove the core, an overshot is lowered on the end of a wire line. The overshot attaches to the back of the core barrel inner tube and the wire line is pulled back and the inner tube disengages itself from the barrel.
Rotary Wash Drilling
This method uses typical drilling techniques and tooling to advance the hole by removing the cuttings with water or bentonite based drill mud. Drill rods or casing may be washed into place and used to undertake SPT’s or push tubes
Cone Penetration Testing
The cone penetration test, or CPT in short, is a soil testing method which will provide a great deal of high quality information.
The method was developed in Holland during the twenties mainly to avoid settlements and to build better foundations. The method builds on the principle of measuring the thrust used to press down a probe into the soil with constant speed. Later, a system with dual rods was developed which would also measure the force on the cone tip itself, and local friction. In the late seventies, probes with electrical sensors were taken into use. This led to the advantage that the resistance could be measured at the cone tip and there were also possibilities to register additional parameters.
Today, it’s common to measure, in addition to the cone resistance and the sleeve friction, also the generated pore pressure which develops in the soil when the probe is pressed down the so called CPTU.
There are many reasons for the wide spread use of the CPT method. The most important being the in-situ measurement, it measures the soil properties in its right environment, in the soil as it is, where it is.
CPT is a fast method and therefore cost effective. It also gives a good over-view of the soil topographic, because of the continuous measures. Because there are no cuttings, as when drilling, CPT is used for many environmentally sensitive sites.