8.3.2 Soil Nailing The rods are usually inserted or drilled at a slope from the horizontal of about 15,but near the upper part of the wall the slope may be larger(20 to 25)to avoid underground utilities. The latest soil nail insertion technique consists in using a compressed-air driver that fires (or launches)the nail at high velocity into the soil. Rod spacing varies between 1 and 4 m2 of the wall surface area depending on factors such as type of retained wall, wall height,available space behind the wall for rod penetration,rod diameter,and design caution.8.3.2 Soil Nailing ❖ The rods are usually inserted or drilled at a slope from the horizontal of about 15º, but near the upper part of the wall the slope may be larger (20º to 25º) to avoid underground utilities. ❖ The latest soil nail insertion technique consists in using a compressed-air driver that fires (or launches) the nail at high velocity into the soil. ❖ Rod spacing varies between 1 and 4 m2 of the wall surface area depending on factors such as type of retained wall, wall height, available space behind the wall for rod penetration, rod diameter, and design caution