4102 RUCKER AVE SAFEWAY FUELING STATION 2016-01-01 MF Import

GEOTECHNICAL ENGINEERING STUDY Inform, Inc May 9, 20U2 E-8493-5 Page 7 If loose soils are encountered at construction subgrade elevations, they should either be overexcavated and replaced with structural fill or compacted in-place to the requirements of structural fill. Existing fill soil may be considered for support of the foundations, or slab, provided the existing fill can be compacted in-place to the requirements of structural f�ll. Alternatively, the footings may be extended through the existing fill and loose soil to the underlying medium dense to dense native soil. As previously discussed, the existing fill observed at the boring locations extended to a depth of approximately three feet. For frost protection, exterior foundation elements should be placed at a minimum depth of eighteen (18) inches below final exterior grade. Interior spread foundations can be placed at a minimum depth of twelve (12) inches below the top of slab, except in unheated areas, where interior foundation elements should be founded at a minimum depth of eighteen (18) inches. With foundation support obtained as described, for design, an allowable soil bearing capacity of two thousand five hundred (2,500) pounds per square foot (psf) can be used for competent native soil, or newly placed or re-compacted structural fill. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty-four (24) inches, respectively. Loading of this magnitude would be provided with a theoretical factor-of-safety in excess of three against shear failure. For short-term dynamic loading conditions, a one-third increase in the above allowable bearing capacity can be used. With structural loading as expected, total settlement of about one inch is anticipated with differential movement of about one-half inch. Most of the anticipated settlements should occur during construction as dead loads are applied. Horizontal loads can be resisted by friction between the base of the foundation and the supporting soil and by passive soil pressure acting on the face of the buried portion of the foundation. For the latter, the foundation must be poured "neat" against competent native soils or backfilled with structural fill. For frictional capacity, a coefficient of 0.40 cen be used. For passive earth pressure, the available resistance can be computed using an equivalent fluid pressure of three hundred fitty (350) pounds per cubic foot (pcf1. These lateral resistance values are allowable values, a factor-of-safety of 1.5 has been included. As movement of the foundation element is required to mobilize full passive rnsistance, the passive resistance should be neglected if such movement is not ,ic�eptable. f mth C�nwullnnh. InC.