A CPT Q&A session with GEI Consultants
Where do you perform your CPT work?
We perform CPT’s on earthen dams/embankments, river sediment depths, USCOE projects from Ft. Peck Montana to New York, RR alignments, bridge embankments, and Power plants. A little of everything you can imagine from Water, RR bridges, Landfills, stability of tail basins for the mines. We also oversee other companies performing CPT. We just worked in Asantana, Kazahkstan overseeing a new energy exposition 2016 project for both SPT’s and CPT. Also have overseen CPT testing in Doha, Qatar.
When did CPT first become of interest to GEI Consultants and why?
We have over 30 years of CPT testing experience. In the late 80’s we purchased a 30T CPT truck and traveled around the US performing CPT on challenging geo-technical projects. In the mid-90’s we sold our truck and started to perform CPT testing behind drill rigs. At the time we had a fleet of 18 drill rigs from track mounted, ATV, truck mounted, Barge mounted, etc. We get involved with delicate soils all the time.
In some cases even when continuous SPT sampling you can’t always detect small seams that we're interested in. This is where CPT comes into the picture on a lot of projects. One larger failure project was the TVA tailing basin project in Kingston, TN. We used CPT with continuous sampling for the root cause investigation.
What is the primary type of equipment GEI has outfitted with CPT capabilities and what has been the result?
We have two complete Vertek Hogentogler systems with 5T, 10T tension cones, conductivity module, seismic, pore pressure, and temp. We have had great success pushing through challenging soils throughout the United States. We’ve worked with MN DOT helping them complete backlog when their equipment was fully utilized.
Our typical production behind a drill rig is ~500 linear feet per day pushing 20’ soundings, and ~600 linear feet per day pushing 100’ soundings. We have had great seismic data and have compared it with both Downhole and Crosshole seismic data collected at the same location at Nuclear and Coal plants. We’ve performed CPT on any type of soil or location imaginable. Key is to know the gear and the limitations.