Retaining structure in reinforced soil at the port

Edilgrid® for reinforced soil at the port of Al-Hoceima

Woven polyester geogrids with PVC coating, Edilgrid®, supported the reinforced slopes protecting the port infrastructure.

Background

The port of Al Hoceima was undergoing rapid expansion, confirmed by the presence of numerous hotels and administrative buildings. Around the area, the coast was rocky, with high, articulated stretches alternating with sections of lower inclination. One of these lower-inclination stretches lay close to the port structures. From a geotechnical standpoint, the slope consisted, from top to bottom, of highly altered marly schists (an area subject to erosion), intermediate fractured limestone layers, and further fractured schists.

The hillside measured about 50 meters in height, with an average inclination of 40 degrees. The area was under monitoring because it was subject to surface erosion caused by rainfall and falling rocks onto the road below. The slope also showed deep sliding, with the sliding surface confined within the altered schist layer. In addition to these erosion and sliding phenomena, the edge of the mountain was gradually receding, risking damage to or collapse of the buildings on the ridge and a negative impact on the commercial buildings in the area.

The solution

To counter the deep slide affecting the slope, engineers built a piling wall with drilled piles 1,500 mm in diameter, arranged in three rows in a staggered pattern. Upstream and downstream of the piling wall, two reinforced soil structures were built, 7.00 m and 11.50 m high respectively, with a 63-degree incline and 50 cm layer spacing.

The Edilgrid® geogrids used had a tensile strength between 55 and 150 kN/m. Besides contributing to the overall stability of the slope by blocking the surface sliding planes (the piling wall intercepted the deep ones), the top of both reinforced soil structures hosted the new local road.

Completing the works

In the following phase, benched terracing supported by Berlin walls reshaped the uphill slope above the higher reinforced soil structure, completing the safety works for the port area.