Civil Engineering PE

Answer: D - Cantilever, tied-back and soil nailing are all types of retaining wall systems. Retaining walls systems are used to hold back the earth and maintain a difference of ground surface elevations. Generally, the cost to construct a retaining wall system is usually higher than the cost to form a new slope. As such, a retaining wall system should be used only when it is cost-effective, and the retained soil height should be kept as low as feasibly possible.