Soil nailing has become a popular method to shore exca-vations and to build retaining walls due to its versatility and cost effectiveness. Generally broken into two cat-egories, temporary and permanent ground retention systems, soil nailing has evolved into many variations. A range of dif-ferent means and methods have emerged, giving the construc-tion industry an incredibly adaptable shoring system. The im-portance of a well-seasoned soil-nail team, however, cannot be understated for the success of any project.
Temporary soil nailing is the system that utilizes the nail for a limited time during construction process for ground support. Once the permanent structure is in place, the nails are essentially aban-doned. By contrast, permanent soil nails remain in service for the life of the wall. The shotcrete application required during the shor-ing process can also be temporary or permanent, but not necessar-ily the same as the nail. Hence, a temporary facing may be con-structed with permanent nails or vice versa.
Typically, in basement construction, soil nailing is used as a temporary shoring system and is installed concurrently with the excavation for the basement walls. After the basement has been excavated and the soil nail system is in place, either a mat slab or footings are poured and a permanent cast-in-place con-crete or shotcrete wall is installed. If a shotcrete wall is cho-sen, it can be installed with many different finishes to fit the use of the structure. Typically, shotcrete basement walls are fin-ished with wood or rubber floats to create a sand finish. In tem-porary soil nailed walls, the structural floors and walls are in-stalled; the soil nailing retention system is no longer needed to support the walls. In some cases, the wall is installed in a top down manner concurrent with the soil nail anchor installation, in both temporary and permanent shoring systems.
In the past, the highway departments often utilized the per-manent soil nail wall system with shotcrete lagging, covered with a cast-in-place or precast facing to give the completed wall a cast-in-place look. Now, however, permanent soil nailed walls are being used extensively along West Coast highways and freeways.
Although materials, equipment, and methods vary greatly, soil nail retaining wall construction involves variations of the following very basic steps: