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Geotechnical Engineering Report 9 May 25,2017 <br /> Central Everett CHC,Everett,Washington RGI Project No.2017-094 <br /> 5.3.3 HELICAL ANCHORS <br /> As an alternative to micro piles, helical anchors can be used. A helical pile is an <br /> extendable deep foundation system with helical bearing plated welded to a central shaft. <br /> Load is transferred from the shaft to the soil through these bearing plates. RGI <br /> recommends that either square shaft or round shaft lead sections be used. The first <br /> section of lead section contains helical plates. The lead section can consists of either one <br /> or up to four helices. Additional helices can be added, if required, with the use of helical <br /> extensions. The design capacities listed in Table 6 can be used in design. The design <br /> capacities assume 6-to 8-inch diameter helix. <br /> Table 6 Helical Pile Capacities (kips) <br /> Pile Type Shaft Diameter(inches) . Compression Uplift Lateral. <br /> Helical 1.5 15 20 2 <br /> The helical piles can be installed either using a machine or hand-hold tool. The above <br /> capacity can be reached with a torque of approximately 1,000 foot-pounds. A <br /> geotechnical engineer needs to observe the pile installation and verify the capacity during <br /> construction. <br /> 5.3.4 DEEP FOUNDATION SETTLEMENTS <br /> With deep foundations designed in accordance with the recommendations in this section, <br /> maximum total and differential post-construction settlements of 1 inch and 1/2 inch, <br /> respectively, should be expected. <br /> 5.4 SLAB-ON-GRADE CONSTRUCTION <br /> If new slabs are needed, they can be supported on the medium native soil or new <br /> structural fill. Immediately below the floor slab, RGI recommends placing a 4-inch-thick <br /> capillary break layer of clean, free-draining pea gravel, washed rock, or crushed rock that <br /> has less than 5 percent passing the U.S. No. 200 sieve. This material will reduce the <br /> potential for upward capillary movement of water through the underlying soil and <br /> subsequent wetting of the floor slab. Where moisture by vapor transmission is <br /> undesirable, an 8- to 10-millimeter-thick plastic membrane should be placed on a 4-inch- <br /> thick layer of clean gravel or rock. <br /> For the anticipated floor slab loading, we estimate post-construction floor settlements of <br /> %- to 'A-inch. For thickness design of the slab subjected to point loading from storage <br /> racks, RGI recommends using a subgrade modulus (Ks) of 150 pounds per square inch per <br /> inch of deflection. <br /> kill <br /> R LEYGROUP <br />