SOIL MECHANICS OF THE STRUCTURE, ENGINEERING PROPERTIES AND BEHAVIOR UNDER LOADING BRINGING CHANGES IN DIFFERENT WEATHER CONDITIONS MUST HAVE PROPER STUDY., BEFORE DESIGN OF STRUCTURE

The angle of repose of a soil is not the same as its angle of internal friction and the angle of repose is determined by the unstable layers at the surface of the slope, loosely tipped, where as internal friction includes not only intergranular friction but also interlocking. The angle of repose, however, is approximately equal to the angle of internal friction of sand in a loose state. The angle of internal friction for dense sands varies from 35 degree and 46 degree and for loose sands between 28 degree and 34 degree. That for dense well graded gravel may be as much as 50 degree. Some Engineers consider that in all formulae of soil pressure the angle of internal friction should be used and not the angle of repose. If a mass of earth (clay, sand, gravel or any such material) is left exposed to weather for sometimes its sides will slip and will gradually attain a stable slope without tending to slide. The angle between the horizontal and this slope is termed the natural angle of repose for that particular material. The limiting angle of a plane (surface of any material) to the horizontal on which plane rests a block, which is just on the point of sliding considered as the angle of friction. This angle depends upon the value of the co-efficient of friction between the two surfaces, ie the plane and the block. The tangent of the angle of the friction is known as the co-efficient of the friction or the co-efficient of the sliding friction. Most slips occur in cohesive soils due to increase in moisture content. For granular soils, the resistance in sliding is dependent upon the angle of internal friction. For sands a very small movement only is required to change the soil from at rest state to the active state. The natural, strangest and ultimate form of earth slopes is a concave curve in which the flattest portion is at the bottom. In constructing slopes the reverse of this  form is most often made , which invites slips. Straight or conclave slopes continue to slip until the natural form is attained. Therefore in cutting concave slopes should be formed to avoid slips. A number of methods are employed for testing soils which requires special laboratory equipments, and the bearing capacity of the soil depends upon the physical characteristics of the soil particles, ie size, shape, cohesive properties, frictional resistance and the power to retain moisture etc. The critical factor in the settlement of a structure is not the amount of settlement but the differential settlement between the different parts of a structure itself. Excessive pressure is Comparatively uncommon cause of settlement. Investigation of all layers under a foundation should be made as even thin layers are weak in shear can cause settlement. It is therefore necessary to design the structure as per the load bearing properties of the soil. Keeping in view the position of angle of repose and the co-efficient of friction it is necessary to place a building structure on the natural ground and avoid filling for the placement of the structure:--.Er Fateh Chand Guleria, Director RTI welfare Association registered number HPCD, 3552 , Bilaspur Himachal pradesh phone number, 9459334377