Hera landfill capping

Italy, Ravenna (RA)
Drainage geocomposites and geomats for landill capping

Problem:
with the end of life of the non-hazardous waste landfill owned by HERA located in Ravenna came the problem of final closure of the perimeter embankments using geosynthetic materials.
The geosynthetic solution for the embankment was approved by the Province of Ravenna for the safety of the embankment. The works involved included:

1. Evaluating the type of drainage geosynthetics in order to obtain a basic equivalence compared to a layer of natural materials
2. Evaluating the equivalence of synthetic geocomposites to be used in alterative to the waterproof sheath
3. Evaluating the overall stability of the cover package adopted In terms of the thickness of the covering top soil indicated in Italian Legislative Decree 36/2003 (> 1.00 m), which is aimed at promoting the grown of ground cover plants for environmental cleanup and suitable for providing adequate thermal protection to the barriers below, a soil thickness of 30 cm was chosen based on the following considerations:

• a thickness of 30 cm is adequate for the growth of grassy plants with limited root systems;
• the water erosion protection function is guaranteed by the greencovering; 3) the thermal barrier mainly addresses the layers of minerals which are replaced by geomembranes and/or bentonite geocomposites.

Solution:
in terms of the average slope of the landfill embankments, the average thickness of top soil cover, and the friction angles between the various geosynthetics of the capping and the geosynthetics-soil, in order to guarantee the stability of the embankment, SintexMat®R35/20, a three-dimensional geomat for erosion control, was employed.
Considering the thickness of the granular soil for replacement (50 cm) and the slope of the embankment (30°), SintexDrain® GNG5, drainage geocomposite, was used as both a biogas captation layer and precipitation drainage layer.
Statistical and seismic analysis were performed according to the Ling and Leshchinsky (1997) approach, which can be considered among the most complete calculations for these works based on the limit equilibrium. For the hydraulic parts, Darcy’s law was used.