Retaining walls are the structures used to support earth,loose stone or other materials which would not be able to stand vertically unsupported.these types of materials when unsupported attain a natural slope the angle which this slope makes with horizontal is known as ANGEL OF REPOSE (varies with type of material). the material retained or supported by retaining walls is called back fill. the pressure of earth on retaining wall is known as earth pressure. the position of the back fill lying above the horizontal plane and the elevation of the top of the wall is called surcharge. the inclination to the horizontal is called surcharge angle β (beeta).