1010 N BROADWAY EVCC 2018-01-01 MF Import

PROPOSED LIBERTY HALL,EVERETT COMMUNITY COLLEGE Everett,Washington ▪ Depending of the actual building loads, column footings may be supported on four to five drilled aggregate piers placed on about a four-foot center-to-center spacing in both directions. • Perimeter footings may be supported on drilled aggregate piers placed at a spacing of 7 to 8 feet center-to-center. ▪ If needed for floor slab support, the drilled aggregate piers may be placed on a 7- to 8-foot center to-center spacing in both directions. Up to two feet of crushed gravel will be placed over the top of the drilled piers under the floor slab. Drilled aggregate piers would likely be drilled at a level about 1 to 2 feet below the building floor slab depending on the thickness of the crushed gravel layer. The crushed gravel layer could be incorporated into the recommended capillary break layer. As discussed above, a minimum 2 foot thick layer of structural fill consisting of gravel borrow per WSDOT Standard Specification Section 9-03.14(1)with the exception that the fines content be less than 5 percent may be needed between the drilled aggregate piers and the foundations. This layer of structural fill will help transfer loads from the foundations and slab-on-grade to the drilled aggregate piers and will help reduce differential settlement. Foundation Settlement We estimate that the post-construction settlement of footings founded as recommended above will be less than 1 inch. Differential settlement between comparably loaded column footings or along a 25-foot section of continuous wall footing should be less than 1/2 inch. We expect most of the footing settlements will occur as loads are applied. Loose or disturbed soils not removed from footing excavations prior to placing concrete will result in additional settlement. Mat foundations may be designed using a modulus of subgrade reaction of 50 pounds per cubic inch bearing on dense to very dense native glacial soils, properly constructed structural fill pads,or aggregate piers as described above. Lateral Resistance Lateral loads can be resisted by passive resistance on the sides of the footings and by friction on the base of the footings. Passive resistance should be evaluated using an equivalent fluid density of 350 pounds per cubic foot (pcf) where footings are poured neat against native soil or are surrounded by structural fill compacted to at least 95 percent of MDD, as recommended. Resistance to passive pressure should be calculated from the bottom of adjacent floor slabs and paving or below a depth of 1 foot where the adjacent area is unpaved, as appropriate. Frictional resistance can be evaluated using 0.4 for the coefficient of base friction against footings. The above values incorporate a factor of safety of about 1.5. If soils adjacent to footings are disturbed during construction, the disturbed soils must be recompacted,otherwise the lateral passive resistance value must be reduced. Page 14 I June 10,2010 i GeoEngineers,Inc. File No.5836.010-0D