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in the compacted fill. In design computations, the upper 12 inches of passive resistance should be <br /> neglected if the soil is not covered by floor slabs or pavement. If future plans call for the removal of the <br /> soil providing resistance,the passive resistance should not be considered. <br /> An allowable coefficient of friction between concrete and soil of 0.35, applied to vertical dead <br /> loads only, may be used to calculate the resistance to sliding at the base of the foundation elements <br /> bearing on undisturbed native soil or well-compacted granular fill. However, if passive and frictional <br /> resistance are considered together, one-half of the recommended passive soil resistance value should be <br /> used because larger strains are required to mobilize the passive soil resistance as compared to frictional <br /> resistance. A safety factor of about 1.5 is included in the base friction design value. We do not <br /> recommend increasing the coefficient of friction to resist seismic or wind loads. <br /> 3.9 CONCRETE SLABS-ON-GRADE <br /> A conventional concrete slab-on-grade will be used as the interior floor of Building 40-58 and <br /> will support uniform loads of up to 500 psf. Preliminary discussion with the design team included a <br /> 12-inch thick interior concrete floor slab atop a 6-inch layer of compacted Crushed Surfacing. This <br /> concrete slab section should perform satisfactorily based upon previous Boeing experience. However, <br /> slab construction should only proceed after all grading and site filling operations are complete in <br /> adjacent area and settlements due to filling have taken place: up to about 2 inches of settlement could <br /> occur as a result of site earthwork operations, and settlement across the site is expected to be non-uniform <br /> due to a variable thickness of existing fill,variable compressibility within that fill, and a varying thickness <br /> of new fill needed to raise site grades to the proposed uniform subgrade elevation. We expect that the <br /> settlements will be primarily elastic in nature and will occur during and shortly after fill placement. <br /> However, there is the potential for minor additional settlement to occur following the completion of <br /> earthwork(on the order of one to two weeks); we recommend that a settlement monitoring program be <br /> implemented during site filling in order to estimate actual settlements and settlement rates. These data <br /> will be useful for construction scheduling of the slab-on-grade. Landau Associates would be pleased to <br /> assist with development of a settlement monitoring program. <br /> The subgrade for the tunnel floor may consist of existing 1968 fill or glacial till. In all of these <br /> cases, we recommend that the slab section geometry include a moisture membrane and capillary- <br /> break/membrane-protection drainage layer above the slab subgrade, as described in the following <br /> paragraphs. <br /> In all areas where concrete slabs-on-grade will be constructed(main factory floor, autoclave area <br /> floor, aprons, and tunnel floor), a minimum of 6 inches of structural fill compacted to 95 percent of its <br /> maximum dry density (see Section 3.4) should be placed atop compacted and proof-rolled subgrade <br /> 5/16/14 P:\1423\002\O10\FileRm\R\Draft Bldg 40-58 Report\Bldg 40-58_draft rpt.docx INTERIM DRAFT <br /> 3-8 <br />