main geometric definitions and notations that will be used. The value n=3 is to be considered for household waste. The following limit state designs are to be considered: * Serviceability limit state (SLS) to verify that the maximum allowable deformation in the leachate barrier system is not exceeded. It ensures that the system will continue to perform appropriately even after localized and global settlements. * Ultimate limit state (ULS) to address the failure of the reinforced soil layer, either by insufficient geosynthetic tensile strength or low interaction properties between the geosynthetic and the soil. It must be verified that none of these limit states are to be reached either during construction or during the expected service life of the cell. SLS The maximum admissible deflection for the lining system is first determined. A value of 3% is used in the literature for an 80-mil (2-mm) high-density polyethylene (HDPE) geomembrane used as a primary lining system (Seeger and Müller 1996). The other components of the leachate barrier system may influence this value. The stress distribution on the reinforcement geosynthetic is considered uniform and vertical without considering any contribution from the circumference of the soil cylinder, as shown in Equation 1. (1) where: σ: stress on the reinforcement geosynthetic FSGsup, FSQsup: factors of safety The residual stiffness of the reinforcement geosynthetic during the service life of the structure (Equation 2) must be greater than: (2) where: εmax: maximum allowable elongation in the reinforcement geosynthetic to ensure that the barrier system remains fully functional The strength increase in the reinforcement geosynthetic will cause the geosynthetic deformation in the anchoring zones and will increase the deflection in the cavity. The stiffness of the reinforcement geosynthetic must then be overdesigned to take it into account and remain within the allowed deformations. ULS The ULS design regarding the minimum required strength of the reinforcement geosynthetic shall consider the longterm behavior of the product and its www.GeosyntheticsMagazine.com 25 γwaste: unit weight of the waste n: arching effect factor (n=3 for municipal solid waste) D: diameter of the cavity γpb: unit weight of the primary leachate barrier system Hpb: thickness of the primary leachate barrier system γsb: unit weight of the secondary leachate barrier system Hsb: thickness of the secondary leachate barrier system γll: unit weight of the leveling layer (above the reinforcement geosynthetic layer) Hll: thickness of the leveling layer (above the geosynthetic layer) P: permanent loads Q: temporary loads Localized differential settlements are difficult to anticipate. The BRGM guide suggests taking them into account by considering a cavity with a diameter of 3-6 feet (1-2 m) within the waste mass.http://www.GeosyntheticsMagazine.com