ARCHIVED REPORTS_1992-1993 - Laserfiche WebLink

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k%J KLEINFELDER File No._204W-bl January 7, 1993 We recommend that all foundation excavations on th'' project be observed by a representative of our firm prior to placement of reinforcing steel 'i the excavations. The purpose of the observations is to confirm that the soils actually encOLintered in the foundation ex.;avations are the same as those on which our recommendations are based, and to observe for any extremely loose pockets of soil. Lateral EMMM Resistance to lateral forces can be provided either by friction between the base of the foundations and the soil or by passive pressure of the sides of the foundations against the soil. The recommended coefficient of friction is 0.4. The recommended passive soil pressure is an equivalent fluid pressure of 350 psf per foot of depth. Active pressures for use in the design of retaining walls can be based on an active pressure of 35 pounds per square foot (psf)/ft. of depth. If walls are considered rigid and not free to deflect, an at-rest pressure of 60 psf/ft. should be considered. Floor Slabs We recommend that floor slabs be underlain by a minimum of 6 inches of recompacted existing soil or by Engineered Fill. The recommended minimum degree of compaction is 90 percent of the maximum dry density as determined by the ASTM D-1557 test procedure, at a moisture content near optimum. In our opinion, a capillary moisture break, such as provided by a layer of gravel or coarse sand beneath floor slabs, can be omitted in areas not to receive moisture-sensitive floor coverings due to the sandy nature of the near-surface soils. In areas to receive moisture-sensitive floor coverings, we recommend that the subgrade soils be covered by a moistureproofing membrane such as "Moiststop," or equivalent, to act as a vapor barrier. Care should be exercised to avoid tearing, ripping, or displacing the membrane during construction. If the membrane becomes tom or dismrbed, it should be removed and patched, or completely replaced. The membrane should be covered with approximately 1 inch of moist sand to protect it during construction and to aid in curing the concrete. For floor slabs that will not contain heavy storage or equipment loads, we recommend that the floor slabs be a minimum of 4 inches in thickness and be reinforced with at least wire mesh placed at midpoint in the slabs. For floor slabs that will contain heavy loads, thicker on the order of 5 to 6 inches may be required. The actual floor slab thickness and reinforcing design should be provided by the structural engineer. Site Preparation and Grad ng Site preparation should include the stripping and removal of all concrete and asphalt pavement, vegetation and debris from the areas of construction. The stripped vegetation and debris should not be incorporated in any of the structural fills. The actual depth of stripping should be determined in the field by a representative of our firm. Voids left by the removal Copyright 1993 MeinfeLder, Inc. Page 6 of 11