Soil Structure Interactions of Retaining Walls

Structural stiffness of a retaining wall, properties of the foundation soils, and the construction sequence, including order of placement of fill in front and back of the wall, affect movements and hence the development of active and passive earth pressures. Retaining walls considered in this paper are the traditional reinforced concrete type usually constructed along highways and dam spillway structures – the highway wall is a simple cantilever and the spillway wall in an earth dam is a counterfort. Another type of earth retaining structure considered is an unconventional type, which was used during construction of a second large-diameter reinforced concrete siphon alongside an existing siphon of similar proportions for water conveyance on a hydro project. Results of numerical modeling for the highway retaining wall are compared with measured data. For the spillway and the siphon structures, only numerical analyses are included, as these structures were not instrumented. Practical significance of the information included in the paper are: (a) both the structure and the soil on which it is founded form an integrated system that needs to be analyzed as such for meaningful results; (b) interfaces between the soil and structure, where separation and slip can occur, should be included in numerical modeling; and (c) sequence of construction starting with the initial excavation, and construction sequence including placement of the fill in lifts, should be simulated.