splicers without welding for each of the compression-only piles and to use mechanical splicers with full fillet welding for piles subject to uplift. This splicing procedure allowed the contractor to splice three pile sections for a 165 ft (50 m) long pipe faster, which resulted in about a 20% decrease in the projected schedule. Dynamic Pile Testing Results: PDA testing was again performed on 16 of the test piles during restrike, which occurred three weeks after the initial driving. Test data for 14 select piles obtained using the PDA were analyzed using CAPWAP, which indicated an ultimate pile compression capacity during initial driving between about 150 and 230 tons (1,335 and 2,046 kN), with an average of about 170 tons (1,512 kN) and an ultimate compression capacity during restrike between 260 and 340 tons (2,313 and 3,025 kN), with an average of about 300 tons (2,670 kN). On average, a 75% increase in compression capacity was observed from pile setup. Criteria Final Driving Resistance, blows/ft (per 0.3 m) Maximum Hammer Energy, kip-ft(N-m) Maximum Driving Stresses, ksi (MPa) Pile Compression Capacity – PDA, tons (kN) Pile Comp. Capacity – CAPWAP, tons (kN) PDA and CAPWAP results summary Static Pile Testing Results: Five axial- compression load tests were performed as part of the test program. The test piles were loaded to or beyond the failure criteria established in the NYC Building Code to force “geotechnical failure” and to assess ultimate pile capacity. The load was subse- quently reduced and maintained at the prescribed proof loads. In addition, two full-scale lateral load tests were performed on the pipe piles up to a test load of 20 tons (178 kN), which was 200% of the design load. After evaluating all of the test results and considering the estimated dragdown loads, the recommended production piles consisted of a 16 in (406 mm) diameter pipe pile with a wall thickness of 0.5 in (13 mm) driven and were to be driven to about 160 ft (49 m) below existing grades to a 92 • DEEP FOUNDATIONS • SEPT/OCT 2018 Footing Design The spread footings for the podium-garage were proportioned assuming an allowable bearing pressure of 3 tsf (287 kPa). Total settlements of these footings were estimated to be less than 0.75 in (19 mm), which were comparable to the estimated pile settlements of less than 0.5 in (13 mm) at a design load of 150 tons (1,335 kN). The estimated resulting differential settlements were estimated to be less than 0.5 in (13 mm). Production Pile Driving The contractor used three pile driving rigs of similar rated energy to install all production piles to the minimum tip elevation El. -155 ft (El. -47.2 m). The contractor installed an average of 7 piles per minimum tip El. -155 ft (El. -47.2 m) to provide the following capacities: • Allowable compressive load = 150 tons (1,335 kN) • Allowable tension load = 50 tons (445 kN) • Allowable lateral load (free-head) = 10 tons (89 kN) Pile ID 1A 3C IP -6 3A 1B Pile Type 16 in (406 mm) diam 16 in (406 mm) diam 16 in (406 mm) diam 14 in (356 mm) diam HP14x89 (HP360x132) Compression Load Tests Summary Pile ID 2B IP -2 Pile Size 14in (356 mm) diam 16in (406 mm) diam Lateral load tests results summary Initial Driving 12 – 30 45 – 73 (61 – 100) 29 – 42 (200 – 290) 110 – 240 (977 – 2,135) 150 – 230 (1,335 – 2,046) At Restrike 36 to >100 55 – 75 (75 – 102) 30 – 40 (207 – 276 240 – 450 (2,135 – 4,005) 260 – 340 (2,315 – 3,025) to complete production pile driving 10 working days ahead of the initial schedule. Lessons Learned and Conclusions The 3514 Surf Avenue foundations were ultimately successful because the project team — developer, design team and contractor — understood the value of performing field tests early in the design and construction process. The developer had an aggressive design and construction schedule and understood the value of performing extensive field tests to accelerate foundation design. Langan saw the value of additional investigations and load tests (beyond the minimum requirements of the NYC Building Code) to justify more aggressive foundation design parameters. In addition, Langan convinced the developer of the value of the extra costs for subsurface investigations and pile tests to provide a more efficient foundation design. A subsurface investigation that met the minimum requirements of the NYC Building Code (100 ft [30 m] below ground) would not have encountered the deeper clay layer and dense sands that influenced the foundation design. By understanding the local geology, the designer was able to tailor the subsurface Test Load tons (kN) 20 (178 kN) 20 (178 kN) Max. Deflection inch (mm) 0.6 4 (16) 0.69 (17.5) rig per day and completed 591 production piles in 36 working days. Of these piles, 142 were designed for uplift and required fillet welding at each splice. The remaining 449 piles were installed using a drive-fit mechanical splicer without welding. By providing multiple rigs and proposing splice alternatives that sped up installation, the contractor avoided delays and managed Pile Length ft (m) 172 (52.4) 161 (49) 162 (49.4) 185 (56.4) 161 (49) Geotech Failure Load tons (kN) 470 (4,181) 425 (3,781) 360 (3,202) 360 (3,202) 325 (2,891) Proof Load tons (kN) 445 (3,959 ) 400 (3,559 ) 350 (3,114 ) 335 (2,980 ) 320 (2,847 )
