Stable Foundation Reinforcement of Electrical Towers using Micropiles
For more than 20 years, bent or overturned electrical towers have repeatedly caused power blackouts in Germany. In 2005 in Munsterland, for example, 82 electrical towers bent over because they had been exposed to extraordinary ice and snow loads due to extreme weather conditions.
A few years ago, a new standard was implemented for power supply line construction that is designed to significantly improve the stability of electrical towers in Germany. With the help of ice load rehabilitation, the load-bearing capacity of the towers is improved so that they can accommodate higher loads when exposed to wet snow conditions and ice accumulation in winter.
One of the measures for ice load rehabilitation is the foundation reinforcement of existing towers such as the measures that were recently carried out in some areas in Bielefeld. During the rehabilitation of 5 overhead line towers, the existing shallow foundations of the masts were sustainably strengthened using GEWI® Micropiles.
The significant challenge encountered during this rehabilitation project was the fact that the micropiles had to be drilled inside the electrical towers with borehole diameters of 300mm. During this procedure, the system’s real value was demonstrated by its excellent force/borehole diameter ratio.
Furthermore, the GEWI® Micropile system can absorb tensile, compression, and alternating loads. Another important main feature of GEWI® small-diameter bored piles is the flexible length adjustment that can be carried out on site. Furthermore, the proven coarse GEWI® Thread ensures the threadability of the system even in extreme conditions.
The rehabilitation required shorter section lengths for the GEWI® Steel Tendons. The fact that only the borehole is grouted so that there is no spillover is an additional advantage of the GEWI® System. For ice load rehabilitation in Bielefeld, DSI supplied 50 and 63.5mm Ø GEWI® Micropiles that were partly double corrosion protected as small-diameter bored piles. The complete installation was carried out using light-weight and compact drilling equipment that was small enough to fit inside the electrical towers.
The ice load rehabilitation at the 5 towers was successfully completed, and soon, the foundations of additional electrical towers will be reinforced using GEWI® Micropiles.