More recently, the soil is improved by introducing locally separated reinforcing elements. These include: the placing of metallic strips Into the soil (reinforced earth), the Introduction of steel rods or grouted needle piles (soil nailing) or the use of geosynthetic.
Geosynthetics were first used in connection with erosion cootrol applications and were intended to be an alternative for granular soil filters. (Barrett, 1966). Synthetic reinforcement is being increasingly used for temporary and permanent structures to improve the shear strength of soil. The fact that an increasing number of structures must be built on poor soils, has speeded up the development of soil reinforcement techniques. The basic principle of soil reinforcement, as described by Jewell (1982), is that when an oriented reinforcement is included, a higher shear strength is developed in the soil. Credit for early work in the use of geosynthetics should be given to life ICI fabrics in England. Their work and others such as Cheile Linz In Austria and Du pont_and_Micafl in the States has continued. Today many manufactures are involved in the production, sales, and distribution of geosythetics. McGown and others (1988) expected that sales of geosythetics may reach one billion square meters by the end of 1990.