SOIL NAILING FOR STABILITY OF THE SLOPES

Abstract

Soil nailing is a soil stabilization technique which is used as a remedial measure in order to treat the unstable natural or artificial soil slopes. This technique is also used in order to allow the safe over-steepening of new or existing soil slopes. In this method of slope stabilization, a relatively slender reinforcing element is driven into the soil slope. Reinforcing elements generally used in this technique generally consists of HYSD steel bars or steel hollow tubes depending upon the requirement. The nails used for soil nailing are generally driven into the slope at an angle of 100 to 200 with horizontal plane. Due to the application of surcharge load by various means, the backfill material starts deforming which in turn passively produces the tensile stresses in the nails. The method of installation is different for solid and hollow bars. Solid bars are generally installed into the pre-drilled holes. These bars are grouted into place simultaneously using separate grout line. Hollow bars are drilled and grouted simultaneously with the help of sacrificial drill bit. When bars are inserted into the soil slope by using drilling technique ,then they are fully grouted and are installed at a slight downward inclination. Centralizers are used in order to keep the nails at its exact position. In order to provide the stability a rigid facing usually of pneumatically applied concrete (shotcrete) is applied. In some cases isolated nail head plates can be also used for this purpose. In few cases a flexible reinforcing mesh is held against the soil slope face under the head plates. In case if environmental conditions are not adequate, then rabbit proof wire mesh and environmental erosion control fabrics are used in addition with flexible mesh facing.