Soil Nailing Systems
Soil nailing systems are utilized to support top-down excavation methods in certain soil conditions, and are most effective in very dense granular soils and cohesive soils. SNS can be designed and utilized in both temporary and permanent applications.
The excavation progresses in vertical increments of approximately five (5) feet. The exposed soil is then covered by a layer of shotcrete having an approximate thickness of four (4) to eight (8) inches, depending upon design requirements. In conjunction with each tier of shotcrete, a row of soil nails is drilled into place on a horizontal spacing ranging from four (4) to six (6) feet. Once the shotcrete and soil nails are installed at each level, the above process is repeated in subsequent vertical increments until design subgrade elevation is reached.
Soil nailing systems are advantageous in many circumstances. First, where construction schedules are critical, the general excavation can begin immediately prior to and in tandem with the soil nailing operation, thereby reducing the overall project schedule. Second, soil nailing can be performed within soils that are too dense to be penetrated with conventional driven earth support systems. Finally, soil nailing is also beneficial at sites where rock is at or above subgrade elevation, where additional “toe” would otherwise be required for conventional earth support systems.
Typical Applications for Soil Nailing Systems
Temporary and Permanent Earth Support