2400 33RD ST GEOTECHNICAL INVESTIGATION 2018-01-02 MF Import

SC 130 Milbor-Pita StSsow W_ hammer as compared to steel piles of similar diameter and should be handled and driven accordingly. Prior to construction, but following selection of the pile hammer, cushion and driving system, Milbor-Pita should be consulted to determine final driving resistance field criteria using an appropriate dynamic pile driving analysis. Bearing graphs should be generated that incorporate the contractor -proposed hammer/cushion system into the analysis. Typically, penetration resistance at the end of initial driving (EOID) is lower than during re -striking. However, it is not practical to re -strike every new pile after installation to estimate ultimate capacity. Therefore, a minimum penetration resistance should be established for the EOID condition during production pile driving that is based on the results of pile driving analyzer data. We recommend against using a pre -established chart to determine pile driving criteria. W_- recommend a minimum of 2 indicator (or test) piles be driven at each end of the building footprint to assess pile performance under actual field and driving conditions. The indicator piles should be located so that they may also serve as production piles. The indicator piles should be re-evaluated based on the penetration resistance during re -striking. We recommend monitoring the dynamic behavior of the indicator piles with a dynamic pile driving analyzer (PDA) during initial driving and re -striking. The design recommendations may be revised, if necessary, based on results of the PDA evaluation. In addition, the PDA data can be utilized to refine appropriate pile driving criteria for EOID conditions, thus reducing the number of piles requiring re -striking. A minimum of 5 percent of production piles should be re -struck. Pile lengths may need to be adjusted in the field based on conditions encountered during driving. Variable pile lengths should be anticipated, and provisions should be included in the contract documents to facilitate adjustment in payments to the contractor based on actual lengths of piles installed. We recommend that production piles be ordered after driving indicator piles if possible. It may be desirable to issue a separate contract for indicator piles, and perform tests prior to requesting bids for the foundation construction contract. We recommend using fixed leads during pile driving to reduce the potential for pile misalignment. Fixed leads may also facilitate installation of battered piles, if these become necessary. Geotedu ical, Tunnel and Fnvirmaenlel Fngineas 3080 125a Ave NE Pho (425) 969.5779 nellcwe, WA 98005 Page 14 Fax (425)861-0677