By B Myles and R J Bridle. This paper was first published in GE’s July/August 1991 issue
Soil Nailing as a means of soil reinforcement has been an acceptable and increasingly used process since the early 1970s. However, traditionally the installation has featured nails which have been established by drilling, placing and grouting, alternatively the nail has been positioned by tip jetting or hammering. Generally soil nails have been placed within 15 degrees the horizontal to facilitate grouting and treated as though they carried tension only. The computations for these horizontal nails have followed the principle applied in the conventional reinforced earth process. Pneumatically fired soil nails can be shot in the ground at any orientation without any additional expense. Because of speed, cost effectiveness and versatility of this air driven machinery, nails can be placed very rapidly and accurately. The increase in strength of the soil is affected by transferring the tensile and shear resistance of the nail to the soil by friction and bearing. The ratio between the tensional and shear contribution of the nail will depend on the orientation, stiffness, size of the nail together with the location, strength and stiffness of the soil.