3003 W CASINO RD BLDG 45-12 2016-10-20

777X Static Test Building I 5 Allowable Bearing Pressure and Settlement As discussed above,the glacial till bearing layer under the western half of the building is up to 10 feet below the proposed footing grades. Because the density and nature of the native soil or fill above the glacial till can be highly variable, a conservative approach is to completely remove the native soil and fill material above the glacial till within the footing bearing zone and backfill with compacted structural fill. An alternative to this approach is to overexcavate to 2 feet below the footing bearing elevation and backfill with compacted structural fill below the base of the footings. The latter approach has more risk for differential settlement, but has been used successfully on many projects after considering the risks and costs. This approach should not be used near boring HC-9 where high levels of organic soils were observed. Our recommended allowable soil bearing pressures are shown in Table 2. Table 2 - Allowable Bearing Pressures for Building Foundations Soil Unit Allowable Bearing Pressure (kips per square foot) Very dense,silty sand(Glacial Till) 10 Imported Structural Fill over Glacial Till 4 2 Feet of Imported Structural Fill over Medium dense, silty sand (Native 3a Soils and Fill)over Glacial Till a. Organic soils must be excavated and replaced before footing construction. Allowable bearing pressures are for dead and long-term live loads and may be increased by one-third for wind or seismic loads. Footings should be founded outside of an imaginary 1 horizontal to 1 vertical (1HAV) plane projected upward from the bottom edge of adjacent footings or utility trenches. We expect the bearing soil to generally behave elastically,with settlement occurring as the building loads are applied or shortly thereafter. We expect that settlement of individual footings will be less than 1 inch. Differential settlement is expected to be 1/4 to 1/2 inch over a 50-foot length or between isolated footings,whichever is the shorter distance. Size and Embedment We recommend that exterior footings be embedded a minimum of 24 inches below the lowest adjacent grade or base of slab elevation. Interior footings should be embedded a minimum of 12 inches below the base of the slab. Continuous footings should have a minimum width of 3 feet. Foundation Resistance to Lateral Loads Shallow foundation resistance to lateral loads occurs from passive soil resistance against the side(s)of the footing and frictional resistance along the base of the footing. Our recommend design values include a factor of safety of 1.5 and are shown in Table 3. The passive pressures are in terms of equivalent fluid densities for level ground conditions and should be applied using a triangular pressure distribution, ignoring the passive resistance within 2 feet of the adjacent ground surface. These values are appropriate for concrete footings poured directly against the soil. AM ALAI 19106-01 HAff0TOWMA May 29,2015