Innovative Insitu Testing Methods for Solar Farm Foundations
Whether we are involved in the site selection phase or the detailed design and specification phase of a solar farm, it’s essential we understand clearly the underlying ground conditions.
Are there soft soils or fill materials? Is there shallow rock and where is it?
Not understanding the ground conditions well can result in increases in the construction cost per MW, fundamentally impacting the solar farm’s feasibility and profitability.
Typically solar panels (and tracking systems) are mounted on shallow (e.g. 3-5m) driven piles. Pile driving rates depend on the soil type and conditions.
These piles resist lateral and vertical wind loads and accommodate ground movements. To remain stable through-out the solar farm life, we need to understand the effects of wetting (including saturation from flooding) and drying on the strength, stiffness, and structure of the soil surrounding the piles.
Long trenching works are also required for underground cabling.
Here we present two innovative tools often used to establish insitu ground conditions at solar farm sites; the PANDA® Instrumented DCP and the GRIZZLY® Dynamic Penetration Super Heavy (DPSH).
PANDA® Instrumented DCP
The PANDA® is suited to site investigation and captures the cone resistance vs depth profile, in real time.
| Portable small equipment – all in a suitcase |
| For deeper or repetitive tests, a one person operated electric automatic hammer is available |
| Non destructive (almost) – suitable in cultivated fields |
| GPS located and time stamped results |
| Automated data capture with results viewable on site during the test |
| Cone resistance (MPa) vs depth with continuous strength profile |
| High integrity output (correlates well with CPT) |
| Correlates with pile driving |
GRIZZLY® Dynamic Probing Super Heavy (DPSH)
Applicable uses of the GRIZZLY® for solar farms include site investigation, geotechnical auger drilling, and soil sampling (windowless push tube sampling). The GRIZZLY® captures the cone resistance vs depth profile, in real time.
| DPSH – Strength vs Depth profile | Boreholes – Drilled (Auger) or Driven (Windowless push tube sampling) |
| Compact self-propelled stable rig with rubber tracks carried in a van or 4wd ute / Trailer | Any depth required for the solar farm piling and building foundations |
| Non destructive (almost) – suitable in cultivated fields | Obtain undisturbed or disturbed samples |
| Fast execution | Drilled or driven depending on soil composition/ stiffness |
| GPS located and time stamped results | Core samples can be retained for further analysis (e.g. environmental) |
| Automated data capture with results viewable on site during the test | |
| Cone Resistance (MPa / N10 / N20) vs depth with continuous strength profile | |
| High integrity output (correlates well with CPT) | |
| Correlates with pile driving |
On a side note, you maybe interested in an upcoming Australian Geomechanics Society (AGS) QLD presentation on Solar Farm Foundations by Dr. Richard Kelly – Chief Technical Principal for Geotechnical Engineering & General Manager for Technical Excellence, SMEC.
We are using the PANDITO DCP for Level 1 site supervision, it’s very portable and we find it handy for flying into sites.
FH is now routinely using the LWD with very good feedback and useful engineering data. The equipment is an easy to use Zorn LWD.
The ZFG 3000 is an excellent tool and should be included in any professional contractors equipment list of assets. This tool should have a similar impact on the construction industry as the laser level. The ability to accurately and reliably measure this aspect of ground condition will improve the quality of the work and remove doubt as to the progress of the project.
I bought my ZFG 3000 and on the same day less than two hours later, it had paid for itself. Using this instrument, I was able to demonstrate scientifically, repeatably and independently the quality of the work that we had completed for our client. Ending the disagreement and creating an improved working relationship. Most jobs are not as confrontational as this was however, most jobs are built to a standard. The contractor can now measure as required, to know on site, at the time of testing if this standard is being achieved.
I strongly recommend the ZFG 3000 Deflectometer to any earthmoving, civil construction contractor. Good luck with your projects.
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