Gregg Drilling & Testing, Inc. uses a piston-type sampler to obtain relatively undisturbed soil samples without generating any soil cuttings, Figure SS. Two different types of samplers (12 and 18 inch) are used depending on the soil type and density.
The soil sampler is initially pushed in a "closed" position to the desired sampling interval using our hydraulic rig. Keeping the sampler closed minimizes the potential of cross contamination caused by sloughing. The inner tip of the sampler is then retracted 12 inches (or 18 inches if using the longer sampler) leaving a hollow soil sampler with two inner 1¼ inch diameter by 6 inch or four 3 inch long soil sample tubes. If using the 18 inch sampler, two 1½ inch diameter by 6 inch long tubes will be exposed. The hollow sampler is then pushed in a locked "open" position to collect a soil sample. The filled sampler and push rods are then retrieved to the ground surface. Because the soil enters the sampler at a constant rate, the opportunity for 100% recovery is increased. For environmental analysis, the soil sample tube ends are sealed with Teflon and plastic caps. Often, a longer "split tube" can be used for geotechnical sampling. For a detailed reference on direct push soil sampling, refer to Robertson et al, 1998. | 
