Near the provinces border between Navara and GuipCzcoa, near the town of Leitza, the North Pyrenean Fault affects the Northern Autoroute (Pamplona - San Sebastian). The freeway in this area has been built by excavation with 40 metre slopes on the right-hand side, and 6-7 metres ones on the left. Briefly, the geological structure consists in an overlap of chalco-dolomite rocks from the Jurassic era over a series of cretaceous limonite and limestone across the prop level of the Keuper clays. The tectonic structure is transversal to the path of the freeway with which it forms a 45 angle and slopes southwards. Basically, the slope was excavated with a 1H: 1V inclinations in the lower half corresponding to the section of Triassic clays, and 1H: 2V in the upper half corresponding to the Jurassic Dolomites. Between both slopes, an intermediary 4-metre wide hard shoulder has been built. Following a first series of tests which failed with regards to the stabilization measures with agunite base, bolts, downspouts, berm ditches, light surfacing, etc., the final stabilization process was done by reconstructing a slope similar to the initial slope, and by providing environmental restoration with an implantation of green gunite using the Fibrater system. (A)
Samenvatting