SHALLOW FOUNDATION DESIGN (GENERAL NOTES)

SHALLOW FOUNDATION DESIGN (GENERAL NOTES) 

General 

The foundation covers such type of foundation in which the load transference is preliminary through shear resistance of the bearing strata. Normally this types of foundation is laid up to depth of 3 m.

        1) Pad or spread :- in this types of foundation , which is constructed of masonry or concrete and is isolated, the loads of a structure is transferred to the ground in such a manner that the SBP ( Soil bearing pressure) is not exceeded.

        2) Strip :- This types of foundation provide continuous and longitudinal bearing for loads carried by vertical elements such as continuous wall foundation beam etc.

       Design consideration

1.      If foundations wherever the resultant of the load deviats from the center line by more than 1/6 of its least dimension at the bottom of footing , it shoud be suitable reinforced

2.       For continuous wall foundation reinforcement should be provided at places where change in magnitude of load or variation in ground support.

3.       At sloping ground foundation should have horizontal bearing and stepped and lapped at changes of levels for a distance at least equal to the thickness of foundation or twice the height of step which ever is greater.

4.       Ground beam :- Foundation should also have the ground beam for transfer the load. Ground beam carrying a load bearing wall should be designed .

5.       Dimentions of Foundation               

                             R = W + 30 cm

                        Where  B= width at base in cm                                    W= Width of supported wall in cm

6.       Unreinforced foundation may be of concrete or masonry ( stone or brick ) provided that angular spread of load from the pier or bed plate to the outer edge of the ground bearing is not more than 1 vertical to a horizontal to masonry or 1 vertical to I horizontal for cement concrete and 1 vertical to 213 horizontal for lime concrete. The minimum thickness of the foundation of the edge should not be less than 150 mm. In case the depth to transfer the load to the ground bearing is less than the permissible angle of spread, the foundations should be reinforced.