LANDSLIDE IN OKETA

As a result of the appearance of large cracks in a slope on one of the motorways in Spain in a type of colluvial clay material which threatened to produce a landslide of 650000 cubic metres, a small heel was built at the foot of the rocky material. Based on data from laboratory tests and boreholes, it was decided to increase the heel with materials brought to the site that would reinstate the area as a whole with the passive earth pressure removed by the excavation and thus achieve a safety factor of 1.4. It proved necessary to raise the downgrade and modify the groundplan of the left carriageway of the motorway and build both walls in reinforced earth between both carriageways and between one of these and the heel itself. A control system of three dip needles was installed for subsequent monitoring of the solution adopted. (TRRL)