Effect of reinforcement type on the design reinforcement length of mechanically stabilized earth walls

This paper presents the results of a parametric study conducted to investigate the effect of different reinforcement types on required minimum reinforcement length and governing design criteria of mechanically stabilized earth walls. There are several reinforcement types with varying properties used in these walls. The reinforcement should be long enough to satisfy both external and internal stability criteria. The minimum reinforcement length criteria vary throughout the world; however most specifications and guidelines require that minimum length should be equal to 70% of wall height. A natural rock formation behind the wall or manmade shoring system may cause limitations on the reinforcement length. The focus of this paper is to investigate the required minimum reinforcement length and the criteria governing the design length for four different reinforcement types; geogrids, geotextiles, metal strips, and metal bar mats. Effect of different parameters on the required minimum reinforcement length and the governing design criteria were investigated for these four reinforcement types. The parameters considered included wall height, surcharge, reinforcement vertical spacing, reinforced soil properties, backfill/retained soil properties, and foundation soil properties. The results indicate that, depending on the parameters involved, the reinforcement type can affect both the required reinforcement length and the governing design criteria. The study also shows that reinforcement lengths shorter than 70% of wall height, as low as 50%, are possible in some cases. Among the four reinforcement types considered, the metal strips usually require the longest lengths; however, it is possible to reduce the required minimum reinforcement lengths of the metal strips by increasing the coverage ratio.