2021 CHESTNUT ST 2016-01-01 MF Import

Beehtal Corpontfon Terracon July 24, 1997 Page � Tower Foundation: As presently planned, lhe proposed monopole tower will be supported on a single drilled shaR foundation system. A straight shaft at least 24 inches in diameter, drilled a minimum of 20 feet into natural soils is recommended. For axial compression, the drilled shaft may be designed tor a maximum end bearing n�cosure ot 48,000 psf(pounds per square foot). Skin fiction of 330 psf can be used in desig�iing (or either uplift or compressfon loads. These values include a factor oi safety of at least ?.J. For lateral load and overtuming design, passive earth pressures can be de'.ermined based on an equivalent fluid densfty of 410 psf/ft for soils along the shaft above the gr�und water level. For calculation of lateral deflection, a coefficient of subgrade reaction, indepenient of shaft diameter, ot 15 ts( (tons per square foot) may be used for the analysfs. The soil moC ulus for the subgrade soils increases linearly with depth by an amount equal to the coelficient of subgrade reaction for each foot of depth. Laterai load design parameters are valid for maximum soil strain of five percent acting over a distance of one shaR diameter. The passive pressure, soil modulus and coefficient of subgrade reaction are ultimate values; therefore, appropriate factors of safety should be applied in the shaft design. Drilling to design depth should be possible with conventional single flight power augers. The hole will probably remain open without stabilizing measures. However, concrete should be placed immediately after completion of drilling and cleanfng. Due to potentia� sloughing and raveling, foundation concrete quantities may exceed calculated geometric volumes. Concrete with slump in the range of 4 to 6 inches is recommended. Free-fall concrete placement in drilled shafts will not be acceptable. The use of a bottom-dump hopper, or a tremie pipe disch�rging near the bottom ot the hole where concrete segregation will be minimized, is recomme�ded. The shaft bearing surface must be cleaned prior to concrete placement. A representative o(the geotechnical engineer should examine the bearing surface and shaft configuration. Equipment Support: As presently planned, the proposed ancillary equipment will be supported on a concrete slab-on-grade. We understand that the on-grade slab will measure about 10 feet by 12 feet. Equipment loads are expected to be about 3,200 pounds. To reduce potential differential movement of the equipment slab, the natural subgrade soils should be compacted to a firm and unyielding condition and 4 to 6 inches of crushed rock should be placed to support the slab. The upper 12 inches of the natural soils and any new fill placed for slab support should be compacted to a minimum of 95 percent of the maximum density defined by ASTM D1557.