Ämmässuo landfill, Finland case study
Opened in 1987, the municipal landfill Ämmässuo in Finland extends over 50 ha, making it one of the largest in all of Scandinavia.
Two test fields were set up to find a suitable solution for the surface sealing system and future slope reinforcement The structure of these fields consists of a mineral gas-drain layer, a mineral sealing layer, a geosynthetic clay liner, a protection geotextile, a polyester geogrid with low creep characteristics, a mineral drain layer as well as a cover soil layer. The slope lengths vary from 75 m to 120 m and the slope angles from 8° to 18° (V:H 1:17…1:3). The angle of friction between individual geosynthetic materials and mineral layers was investigated in shear tests before the installation took place. Prior to installing the sealing system, calculations were performed on the basis of analytical models and an FEM program. In order to verify these calculations and obtain further information, one slope that had been reinforced with Secugrid® geogrid was monitored with settlement and elongation instrumentation.
Furthermore, moisture measurements were made in various depths to determine the moisture content of the mineral seal. The Ämmässuo landfill operating authorities decided to use NAUE geosynthetic materials for both test fields, supplied by our local sales partner OY Via Pipe AB. The Niska & Nyssönen Oy company was awarded the contract for installing the cover. To optimise transportation costs the roll length for the Secugrid® 200/40 R6 geogrid wasd 70 m for this project. A downhill overlap of Secugrid® geogrids to cover the 140 m long slope areas was not permissible. The solution: an hidden anchor trench at the midpoint. The first published results came from a short-term measurement (six months). These are to be viewed as preliminary for the selected Secugrid® reinforcement. On the basis of set tlement and elongation measurements that have been made to date, the selected safety factor for the slope calculation can be described as sufficient.
Future measurements and findings from the field tests, laboratory examinations and other evaluations will put the effectivenes of Secugrid® and the sealing system with Bentofix®, Carbofol® and Secutex® to the test.