Innovative Insitu Testing Methods for Solar Farm Foundations

Mar 4, 2022 | Soil & Site Investigation

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 profileBoreholes – Drilled (Auger) or Driven (Windowless push tube sampling)
Compact self-propelled stable rig with rubber tracks carried in a van or 4wd ute / TrailerAny depth required for the solar farm piling and building foundations
Non destructive (almost) – suitable in cultivated fieldsObtain undisturbed or disturbed samples
Fast executionDrilled or driven depending on soil composition/ stiffness
GPS located and time stamped resultsCore 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.

FH is now routinely using the LWD with very good feedback and useful engineering data. The equipment is an easy to use Zorn LWD.

Laszlo Petho

Pavements Manager, Fulton Hogan

Insitutek imports, sells and services, unique geotech equipment that has proved of great benefit to those who use it. It has a particularly beneficial role to play for those compacting soil in infrastructure projects.

David Palmer

Earthmover and Civil Contractor

Our Plate Load equipment is getting a lot of use. We’re very happy with it. 🙂

Mary Flux

Director & Engineering Geologist, WANT Geotechnics

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