Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. Abstract A large number of types of retaining devices are currently available but their limitations, recommendations and guidelines are scattered in the technical literature. A synthesis study has been made in which different technologies have been investigated to develop guidelines for the use of the different types of retaining devices. For this purpose, an extensive literature review has

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... been performed and a new classification has been proposed. An electronic database with 207 selected cases from the technical literature and INDOT archives has been created. The database stores the following information: (1) Type of Retaining Device; (2) Geometry (3) Soil conditions; (4) Experience and Performance; (5) Construction; (6) Durability; (7) Economy; and (8) Special considerations. The information stored has been analyzed through a number of correlations. Two design flowcharts have been developed to identify the most cost-effective solutions based on the height of the wall, cost, and soil conditions: one for Fill Walls, and another one for Cut Walls. The conclusions and recommendations obtained are in agreement with guidelines from the Federal Highway Administration (FHWA), and with specifications from the Indiana Department of Transportation. The following is recommended for implementation: (1) Use the flowcharts developed as a preliminary decision-making tool to decide the optimum type of wall for a given project; and (2) the recommendations are based on up-to-date information. It is expected that with time design trends and wall typologies may become obsolete and new technologies may become available. It is recommended that the database and flowcharts be updated every five years. The flowcharts and additional notes provide general recommendations based on limited information. The flowcharts are not intended to cover all possible cases; they should be used for preliminary design and to facilitate engineering decisions. Site-specific conditions or project constraints may require a different solution than that provided by the charts. 17.