Sharra landfill reinforced soil slope

Edilgrid® for the embankment of the Sharra landfill

Edilgrid®: woven polyester geogrids with PVC coating for the construction of reinforced soil slopes.

Problem

The Sharra landfill is located about 7 km southeast of central Tirana and about 600 m southwest of the village of Sharra. The Sharra area is separated from Tirana by the hills of Selita and Sharra, about 300 m above sea level. The Sharra hill range also divides the Tirana basin from the Erzen basin, where the landfill is located.

The landfill sits along the right slope of a small valley, at an elevation ranging between 95 and 125 m above sea level. Along the valley floor runs the Sharra river. In total, the landfill covers a surface area of about 65,000 m². Its body rests on layers of silt and clay, which create natural waterproofing.

To complete the perimeter boundary of the waste storage area, over a stretch of about 160 m, engineers planned the construction of an embankment. The embankment has a face inclination of 45° on the landfill side.

Solution

Engineers built the missing section of the perimeter embankment using reinforced soil technology. They used woven polyester Edilgrid® geogrids with PVC coating, with a tensile strength between 35 and 80 kN/m. Given the modest face inclination of 45 degrees, welded steel mesh shuttering was not required.

Engineers built the face with a simple fold-back of the geogrids. For each reinforcement layer, they calculated the required fold-back length.

At the base of the embankment, engineers built a treatment layer of granular material. This layer serves a dual purpose. On one hand, it creates a level laying surface for the first geogrid. On the other, it acts as a drainage layer, capable of intercepting any rising groundwater and surface infiltration.

The maximum height of the structure is 7.30 m. For sizing the embankment, engineers took into account the possibility of heavy vehicles passing over it, as well as the seismic acceleration of the area. The reinforcements have a maximum length of 7.00 m, spaced 80 cm apart.

Engineers paid particular attention to calculating the overall stability of the structure. The soil in front of the embankment, toward the inside of the landfill, in fact has an average inclination of 17°. This required an increase in the anchoring length of the geogrids, beyond what was strictly necessary for the structure’s internal stability. The goal was to also intercept the deep sliding surfaces, known as base sliding surfaces.