Earth Retention – Retaining Walls, Soil Nail Walls, Rock Nails, and Support of Excavation
Earth Retention Systems are used when soil or rock is excavated to construct a temporary or permanent retaining wall. The uses are widespread and include cuts to level property for building, landscaping, road construction, building excavations, utility excavations or to stabilize slopes. The construction technique used varies with the material being retained, the height of the excavation and the intended use. The facing can be steel, wood or concrete. For permanent walls the face can be shotcrete sculpted to match surrounding or native materials. TerraFirm can provide a complete system that includes engineering.
Tied Back Retaining walls are a system that uses vertical members with rock or soil anchors. The anchors are preloaded against the beams or sheets with sufficient force to counteract the soil pressures. The anchors generally founded beyond the “active wedge” of material being retained. The systems can be permanent or temporary with a variety of facing options.
Soil Nail Walls utilize closely spaced steel bars set in cement grout to reinforce the soil. The system is passive, meaning the bars are not preloaded and some relaxation of the soil is required to activate the system. The wall is constructed from the top down in 4 to 6 foot lifts. With applicable conditions soil nailing requires less time than most other systems and is very cost competitive.
Rock Nails are used to reinforce unstable or unraveling rock faces. Frequently rockfall netting is pinned to the face to trap any falling material. In rocks subject to weathering, such as shale, steel reinforcement can be nailed to the face and covered with shotcrete.
Support of excavation is the process of using one of the above referenced techniques for an excavation such as a basement, parking garage, utility or bridge abutment. Frequently the support of excavation projects are complicated by old foundations, below grade utilities, overhead utilities and unknown fill from prior construction projects.