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� . <br /> . GEOTECHNICAL ENGINEERING STUDY <br /> Told Development <br /> � May 8, 1990 E-4888 <br /> Page 5 <br /> . • Estimated post-construction differential = ]/2 inch across <br /> settlement huilding width <br /> • A one-third increase in the above allowable bearing pressures can be used when considering <br /> short term transitory wind or seismic loads. <br /> � s;. <br /> �;;,# <br /> teral loads can also be resisted by friction between the [oundation and the supporting +`"���`°� <br /> compacted 611 subgrade or by passive earth pressure acting on the buried portions of the "F <br /> . foundations. For the latter, the foundations must be poured "neat" against the existing soil '.:� <br /> or bacY.filled with a compacted GII meeting the requirements of structural fill: <br /> �?� <br /> . � Passive pressuro = 300 pcf equivalent fluid weight '��� <br /> .�.,. <br /> • Coef�cient of friction = 035 =�� <br /> . � <br /> Reteinin¢ and Foundation Wallc +� <br /> �� <br /> � Retaining and foundation walls should be designed to resist lateral earth pressures imposed <br /> by the soils retaincd by these structures. Walls that are designed to yield can be designed � <br /> �p <br /> to resist the lateral earth pressures imposed by an equivalent fluid with a unit weight of � <br /> , thirry-five (35) p.�f If walls are to be restrained at the top from free movement, a uniform <br /> surcharge of one hundred ]00 psf should be added over the full wall height. These values " <br /> aze based on horizontal backfill and that surcharges due to backtill slopes, hydrostatic <br /> , pressures, traf�c, structural loads or other surcharge loads will not act on the wall. If suc3� <br /> surchazges are to apply, they should be added to the above design lateral press�re. For <br /> calculating the base resistance to sliding, we recommend using a passive presssre equivalent <br /> � to that exened by a fluid having a density of three hundred 300 pcf and a friction coefficient ' <br /> of 0.35. The wall pressures apply only for a maximum wall height of eight feet. The above �5 <br /> recommended lateral pressures should be re-evaluated by ECI if higher walls are anticipated. �E <br /> � The w�alls should be backfilled with a suitable free-draining material. The free-draining �� <br /> "sr <br /> b ckfill�shoulddconsi tdof�structuralhfill.n A18typical wall backfilledetail is provided as Plat 3e <br /> 1 <br /> &lab•on-Grade Floors <br /> � Slab-on-grade floors should be supported on structural fill. Any fill or native soils disturbed <br /> by construction aaivity should either be rernmpacted or excavated and replaced with <br /> M compacted structural fill or crushed rock. To avoid moisture build-up on the subgrade, the <br /> slab should be provided with a capillary break consisting of a minimum of four inches of <br /> free-draining sand and gravel. In areas where moisture is undesirable, a vapor barrier, such <br /> ' as a 6 mil plastic membrane, be placed over the capillary break beneath the slab to reduce <br /> � Enrth Consultents, Inc. � <br /> ' �� <br />`- <br />