Expander Body Piles Re-support Structure-PPT Presentation

PPT Presentation

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The Brookline, Massachusetts condominium building was originally supported by untreated timber piles. Deterioration of the piles caused accelerated settlement, cracked walls, and tilted columns. Load testing confirmed that the existing piles had exceeded their ultimate capacity.<br /><br />The initial recommendation called for 231 conventional drilled micropiles, 70–80 feet long, installed from the first floor under roughly 10 feet of headroom. Hub proposed Expander Body Piles (EBPs) as an alternative. An early load test supported the system’s use, and the final design included 233 piles with capacities of 60 or 80 tons. The 80-ton EBPs were approximately 34 feet long.<br /><br />An Expander Body is a folded steel tube installed at the base of a pile and expanded with pressurized grout. Expansion increases lateral soil pressure around the pile base, improving its capacity. The test pile was loaded to 160 and 180 tons—two and 2.25 times its design load. Net settlement was 0.362 and 0.382 inches, respectively, both below the 0.50-inch code limit.<br /><br />Installation took place in the occupied building’s basement, where headroom ranged from 9 to 12 feet and access was restricted by load-bearing walls. Quality control included recording grout pressure and volume. The 54 gallons used to expand the test pile were replicated within 98% across the production piles.<br /><br />Compared with the conventional micropile plan, EBPs were more than 40 feet shorter, reduced piling costs by about 40%, and cut the schedule by roughly 50%. The project demonstrated that EBPs can be an economical foundation solution in constrained, low-headroom settings and in soils where marine sand overlies marine clay or similarly soft material.

Keywords

Brookline

Massachusetts

condominium

foundation

micropiles

Expander Body Piles

load testing

settlement

grout expansion

low-headroom construction