4027 4TH ST SE 2018-01-01 MF Import

lanuary l4, 2003 HWA Proiect No. 2002-146-21 4.3.2 Allowabie .A:ial CapaciHes Deposits of soft to medium stitisilt and clay are anticipated below about Elevation -45 ft, as discussed in Section 3.3.1. In our opinion, the most economical pile system will be achieved by using piles with tip elevations no deeper than appro�timately Elevation —35ft (i.e hanging the piles up in the medium dense to dense sand layer). Because a soft silt and clay layer was encountered below the pile tip (approx. El —45), it is cruciat that the piles aze not driven deeper than recommended, or capacities will be reduced. Additionally, estimated settfements of pile caps will also be greater than those estimated in the following report section, if piles extend deeper than about Elevation —45 ft. Allowable axial pile capacities were developed for 14 and l6 inch octagonal pre-cast concrete piles and 10 diameter tip (18" diametet butt) timber piles, using the subsurface data available, our experience in similaz subsurface conditions and pile driving records Gom previous construction at the WPCF. Recommcnded allowable axial pile capacities aze presented in'fable 1. Piles should be spaced no closer than three pile diameters center-to-center. Nu reduction for group et%cts would be required for piles at this spacing or greater. The piles have bern designed to take the full downdrag load as if the piles were suirounded with fill up to elevation 16 feet (the bottom of the structurally supported floor slab). Pile capaciNes presented on Table 1 include the effects of downdrag. 4.3.3 Response uader Laterat Loading We used the LPILE (Reese and Wang, 1989) computer program to analyze the behavior of timber and pre-cast conacte piles under a range of lateral loads. Our analyses indicate that lateral deflection of the piles is not a controlling factor in design. The results of our analyses (deflecrion with depth and bending moment with depth) aze presented in Appendix C. The legend for the figures in Appendix C indicates the lateral load in kips for euch of the scenarios. 4.3.4 ConstrucNoa ConsideraHons and Geotechnical Monitoring Installation of driven piles may be impacted by the possible presence of tree stumps or other obstructions. To drive the piles, it may be necessary to use pre-drilling, "spudding" with a heavy H-section, or other methods. Provisions should be made in the contract documents for dealing with potential obstructions during pile driving. Ail pile installntion operations should be observed by an engineer from HWA. Piles should be driven using an approved top-impact hammer. Jetting of piles should not be allo�ved. Selection of an appropriate hammer will depend on the pile types and sections selected for use on the project, the contractor's methods, and other factors. Where =00?I36 ¢poe- final LO HWA GEOSCIENCES INC �. �` � ��