7100 HARDESON RD 2016-01-01 MF Import

Fisher 8 Sons, Inc. August 19, 1997 Augercast Concrete Piers Augercast piers should be piers should be installed subsurface conditions. JN 97282 Page 4 installed with continuous flight, hollow-stem auger equipment. The by an experienced contractor who is familiar with the anticipated An allowable compressive capaciry of 45 tons can be attained by installing a 16-inch-diameter, augercast concrete pier at least 10 feet into dense native strata. For transient loading, such as wind or seismic loads, the allowable pier capacity may be increased by one-third. We can provide design criteria for diHerent pier diameters and embedment lengths, if greater capacities are required. The minimum center-to-center pier spacing should be three times the pier diameter. Based on our test boring infortnaGon, we estimate that pier lengths of about 25 to 30 feet would be required to achieve adequate penetration into the bearing soil. We estimate that the total settlement of singie piers installed as described above will be on the order of one-half inch. Most of this settiement should occur during the construction phase as the dead loads are applied. The remaining post-construction settlement would be reatized as the live- loads are applied. We estimate that differential settlements over any portion of the structures should be less than about one-quarter inch. We recommend reinforcing each pier its entire length. This typically consists of a rebar cage extending at least a portion of the pier's length, with a full-length center bar. Each pier can be assumed to have a point of fixity at 10 feet below the ground surface for the computation of lateral load resistance. The Ioose soil against the piers can be assumed to have a design passive eaRh resistance of 350 pounds per cubic foot (pc� acting on lwo times the pier diameter. Passive earth pressures on the grade beams will also provide some lateral resistance. If structural fill is placed against the outside of the grade beams, the design passive earth pressure from the fili can be assumed to be equal to that pressure exerted by an equivalent fluid with a density of 350 pcf. Seismic Considerations The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1994 Unifortn Building Code (UBC). In accordance with Tabie 16-J of the 1994 UBC, the site soil profile is best represented by Profile Type S2. The existing fill and native soils beneath the proposed building are not subject to seismic liquefaction. Slabs-on-Grade The building floors may be constructed as slabs-on-grade atop one foot of structural fill or the existing fill if the fill can be compacted the structurai fill requirements. The subgrade soii must be in a firtn, non-yielding condition at the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced with seiect, imported, structural flll. All slabs-on-grade should be underlain by a capillary break or drainage layer consisUng of a minimum 4-inch thickness of coarse, free-draining, structural fill with a gradaGon similar to that discussed later in Pertnanent Foundation and Retainina Walls. In areas where the passage of OEOTECH CONSULTAN7'S, INC•