The possibility of overturning and sliding of the surrounding building shall be considered during excavation. The minimum factor safety against overturning of the structure as a whole shall be 1.5. Stability against overturning shall be provided by the dead load of the building, the allowable uplift capacity of piling, anchors, weight of the soil directly overlying footing provided that such soil can't be excavated without recourse to major modification of the building, or by any combination of these factors.
The minimum factor of safety against sliding of the structure under lateral load shall be 1.5. Resistance to lateral loads shall be provided by friction between the foundation and the underlying soil, passive earth pressure, batter piles or by plumb piles, subject to the following:
- The resistance to lateral loads due to passive earth pressure shall not be taken into consideration where the abutting soil could be removed inadvertently by excavation.
- In case of pile supported structures, frictional resistance between the foundation and the underlying soil shall be discounted.
- The available resistance to friction between the foundation and the underlying soil shall be predicted on an assumed friction factor of 0.5. A greater value of the co-efficient of friction may be used subject to verification by analysis and test.
The faces of cut and fill slopes shall be prepared and maintained to control erosion. The control may consist of effective planting. The protection for slopes shall be installed as soon as practicable. Where cut slopes are not subjected to erosion due to erosion resistant character of the materials, such protection may be omitted.
Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to control erosion.