Experimental investigation of forces along anchors subjected to dynamic loading under tension and compression in field tests

Full-scale field tests of dynamic rockfall have been performed on a flexible SPIDER Avalanche System to study the dynamic force distribution along the foundations under dynamic loading. Therefore, an anchor to measure dynamic tensile forces and a pile to measure dynamic compressive forces were each equipped with strain gauges. Furthermore, a static pull loading test with load steps of one-minute duration was performed on the anchor to highlight the difference between dynamic and static loading. Effective kinetic energies applied on the net of the SPIDER Avalanche System range from 25 to 492 kJ with impact velocities between 17 and 25 m/s. The results show that the dynamic forces close to the pile- and anchor head are higher and that they are decreasing with increasing distance of pile and anchor. However, the dynamic tensile force distribution is non-linear over the length of the anchor, whereas the dynamic compressive force distribution is linear along the pile length. The comparison of static and dynamic tensile forces shows that dynamic tensile forces are depleted within a shorter distance of the anchor compared to the static tensile forces. Dynamic tensile forces present 25% less in value than the static tensile forces.