Effect of backfill materials on construction cost of cantilever retaining walls

Retaining walls were constructed to ensure stability of soil layers at different levels on the two sides. Retaining walls are designed to have enough resistance against lateral earth pressure. The most important factor affecting the lateral earth pressure is the type of soil behind and in front of the wall. Lateral earth pressure values change depending on the density, strength parameters of the soil and existence ground water table. As for growing lateral earth pressure, dimensions and costs of the wall increase in order to bear to the excessive stress. Therefore, especially in the design of retaining walls with a large amount of backfill, the quality of the backfill should also be taken into consideration and the ground characteristics accepted in the project should be established in the field. In this study, thirty soils from various classes (ML, SM, SP, SW, GP, GW) different from each other were placed behind the wall as backfill. For each soil, ISTCAD v.6.6 software was used to analyze reinforced concrete cantilever retaining wall for first and fourth degree seismic zone conditions. After stability analyses, static and dynamic calculations were made for structural design of the walls. As a result of these solutions, cost analyses for concrete, reinforcing steel and formwork have been made. Approximately 80% the project cost difference between loose and dense soil conditions was calculated. It was observed that dense GW backfill soil gave the best suitable wall dimensions at both first and fourth seismic zones.