Yielding elements made of high-strength expanded polystyrene (HS-EPS)

Yielding elements as a part of the shotcrete lining represent the state-of-the-art for tunnelling in overstressed weak ground conditions. They avoid an overstressing of the shotcrete lining during the early curing process. A novel yielding element is introduced, which overcomes existing systems' drawbacks. The innovative system is lightweight and allows for rapid installation. Furthermore, the modular setup of the element permits on-site adaption to react to actual deformation patterns and changing ground conditions. Recent experiences from an application in an alpine base tunnel in overstressed weak ground conditions are presented.