Risk management and Flexible Foundation Design for the electricity tower construction in the Swiss Alps

Summary

Abstract

The construction of electricity towers for a new 380 kV transmission line in the Swiss Alps of Valais presented complex challenges requiring proactive risk management and design flexibility. The line followed steep elevations in the Alps, where most of the towers were located. The project faced critical risks including a constrained construction window in the summer months (May to September), aggressive sulphate-rich ground which necessitated the highest possible corrosion protection, heterogeneous ground conditions and elevations across the line, hard rock formations overlain by significantly weathered and variable depth materials as well as logistical and accessibility constraints limiting transportation and equipment mobilization. An integrated risk management approach was implemented early in the project, involving collaboration among the Contractor, Designer and Supplier. This approach included tailored foundation designs for each tower, taking into account loadings, ground conditions and elevations, with additional safety factors in accordance with SIA (Swiss codes). The foundation solution employed corrosion-resistant TITAN INOX self-drilling grouted micropile, adaptable to the varying subsurface conditions, optimizing drilling techniques to reach targeted depths despite complex rock and weathered material strata and corrosion protection applicable in any condition. Furthermore, logistical planning accounted for helicopter transport of machinery and materials to overcome accessibility limitations. Further flexibility was embedded through on-site revisions, including foundation type adjustments and detailed topographic mapping to address unforeseen ground conditions. This case study highlights the vital role of thorough risk evaluation and adaptable engineering solutions in rock engineering projects. It demonstrates how a combination of early risk identification, flexible foundation design, and coordinated project management can ensure the successful completion of critical infrastructure in challenging mountainous environments, guaranteeing the durability of the structures and the reliability of electricity supply to the country of Switzerland.