When designing and specifying the assumptions for free-field solar installations, data concerning the soil and other local conditions is of utmost importance.
It allows for the optimization of construction works, avoiding down-time, reduction of performance during operation or quick installation damaging.
Investigation includes: geological, hydro-geological and soil conditions, soil chemistry conditions, morphological, hydraulic, climatic and sociological conditions in the location.
The survey is concluded by specification of conditions for an enterprise performing construction works from the perspective of location of solar panels and design of the installation, taking into account the access roads, drainage or ground surface.
The values specified and deposition depth provide additional knowledge, supplementary to exploratory drilling, allowing for the development of the first concepts of the type and depth of foundations for the solar panels.
Bore hole detection
Considerations are based on the fact that the parameters determining the load-bearing capacity of the steel piles derive from varying soil structures and their respective different force-bearing capacities. It is, therefore, advisable to pay special attention to the examination of the uppermost 2 to 4 meters of the soil stratum.
With measuring methods taken from the evaluation of founding depths for noise barriers and adapted to the prerequisites of solar power plants, it is possible to reliably calculate the necessary founding depths for all kinds of steel piles, if the following parameters are known:
- The engineering properties of the ground
- The dimensions and measurements of the pile
- Forces and momenta operating on the piles
In addition the vertical application of force and its transmission into the soil have to be examined, drawing on information about the contact stress between piles and surrounding soil. Usually, the pile seat depths calculated from tilting torques and horizontally operating forces are sufficient for the piles to also bear vertically afflicted loads. On rare occasions (very light soils), however, it is necessary to increase the pile seat depth in order to effectively transmit vertical stress.
The evaluation system is computerized and homologated according ZTVE LSW88/03. It is based on the norms for permitted encumbrance to the site (DIN/EN 1054).
Trial pile driving
In these trials a steel pile is usually driven into the soil that needs to be examined. Next, force is applied to the pile horizontally and vertically in order to measure its reaction above the ground (deformation). Finally, the profile is usually pulled from the ground, whereby the strength applied is registered.
This method thus procures information about deformations and the influence of different forces occurring at a recently inserted steel pile. However, it only provides limited information about the actual soil structure and soil-mechanical qualities. Ideally, the trial shows that the pile driven into the ground is, in this condition, able to withstand the stress afflicted by the super-structure, which leads to the conclusion that the same conditions apply after construction of the supporting structures.
Ecotec offers determination of these basic design conditions in several subsequent steps. After completion of each step, it is possible to assess the entire project, adapting it properly to the entire concept. The steps are the following: