The technique of soil nailing began to evolve in the early 1970’s. Major research programs in Germany in the mid to late 70’s and in France in the late 80’s advanced this method of construction. It has been successfully utilized worldwide for excavation support and slope stabilization and its use continues to grow rapidly.
Applying the principles of systematic rock anchoring to soil seems to be obvious, but the requirements for soil nailing are higher. The many years of experience gained with pressure-grouted anchors have resulted in a certain level of standards; however, the stability of the supported soil mass must be verified for all stages.
Soil nails are used for stabilizing slopes and excavations. They find an efficient application in granular soils of medium to high density with sufficient internal friction, so that a good load transfer along the soil nail is possible, and only slight creep movements occur in the supported soil mass. The soil nails are installed as the excavation progresses from top to bottom. The surface of the cut is usually stabilized by shotcrete and rebar mats.
Since the soil nails are loaded only by ground movement, a certain outward deflection of the top of the stabilized wall must be expected. The theoretical pivot of the wall is at the bottom of the excavation. Calculations assume the maximum tensile force in the earth mass to occur at a distance from the wall equal to 1/3 to 1/2 of the wall height. There, parallel to the wall, the interface between the unstable soil and the retaining stable ground must be assumed. This location is also the area of the highest bending for the soil nails. The anchoring length of the soil nails must extend into stable ground.
DSI has been a pioneer in the use of soil nails to reinforce existing ground. Today, DSI is widely recognized as the principal worldwide source for soil nails meeting the most demanding performance requirements.