Long term strength and safety in steep soil slopes reinforced by polymer materials

A rational method is described for the selection of material properties and design safety factors for steep reinforced slopes. The proposed method clearly separates the forces required for equilibrium, which depend on soil mechanics, and the forces made available by the inclusion of reinforcement layers. Accepted limit state concepts in geotechnical engineering are adopted for the calculation of the required forces for design. For the calculation of the available forces, emphasis is first placed on the importance of the design time and the design temperature for the polymer reinforcement. Secondly a distinction is made between the reference properties of the material supplied by the manufacturer and the expected properties of the reinforcement in the ground, at the end of the design life, when it has been subject to mechanical damage and the soil environment. The need for extrapolation of data to determine the long-term properties is the third main theme. The focus is on the calculation of the allowable force in the reinforcement available to maintain equilibrium. The latest data on polymer reinforcement materials are examined in the paper. The number and position of the required safety margins for the proposed method are described, and magnitudes for them are suggested wherever possible, based on existing knowledge.