TOWER FOUNDATION
The foundation dimensions are recommended for each type of tower, according to the nominal load and height of the tower in question. Foundations are calculated according to the Sulzberger method for several different characteristics of bearing, non-aggressive and stable soil.
Soil characteristics are established according to the abovementioned Regulation for Overhead Power-lines obtained by geo-mechanical tests used in designing transmission lines over many years of experience for:
- gravel and gravel-sand soils, sandstone, flysch, etc.
free of groundwater, σdop = 250 kN/m2
with groundwater, σdop = 200 kN/m2
- clay and clay-sand soils
free of groundwater, σdop = 150 kN/m2
with groundwater, σdop = 120 kN/m2
- for foundations on solid rock the strength capacity, σdop > 500 kN/m2 the minimum dimensions are conditioned by the geometry of the foundation, tower structure and method used in making the foundations.
The foundation is made for simple structure as a not-reinforced concrete block without shoe, into which is placed the foundation part of the structure. To insure simpler installation in cases of deep foundations, the construction of foundation extensions is proposed, in this case it is possible to use smaller profiles than the dimensions of tower main legs. It is required to use concrete, pressure strength class C20/25, that does not lose strength by ageing.
By standard the foundation is made with crown d = 20 cm over the ground. If required (flood water, increased security height of the conductor, construction on inclined plateau, etc.) the structure is made with appropriate heightening of the foundations.
For soils of lower/poorer characteristics and conditions, deviating from the defaulted ones, as also for different technology used (e.g. shallow foundations), the adequate foundations shall be recalculated. In this case it is also necessary to take into consideration the standard length of the foundation part of the structure (L) characteristic for each tower, or consult the manufacturer of the structure for possible manufacturing of customised foundation section (e.g. for anchoring screws).
