Abstract:
A novel piling system in the USA will resupport a condominium building in Brookline, MA. This structure was built in 1909 and is supported on timber piles. The structure has settled up to 9.0 inches into the 1970s and has continued to this day. There are indications that the settlement has accelerated at localized sections. Test pits have shown the top of the timber piles to be cracked and the overall number of piles to be insufficient to support the existing structure with an adequate factor of safety. The city of Brookline directed the condo association to remedy this situation due to increasing safety concerns.
A conventional drilled micropile system along with extensive grade beams were developed to support the structure. This piling solution proved to be very expensive and time consuming due to the relatively long depth of the piles. The Expander Body piles were introduced to the project as a way to reduce both.An extensive pile load test was performed to demonstrate the ability of this system to provide the required design capacity. Subsequently, Hub provided a proposal which reduced the cost of the pilings by 40% and the schedule by about 50%. The key to these reductions is the much shorter length of the piles: 30 feet vs 70 feet. This also reduced the volume of drill spoils that the project would be required to manage and dispose.
The Expander Body pile utilized here consists of a drilled pile with a folded steel section at the bottom that is expanded with cement grout injected under pressure. A total of 233 piles will be installed with design capacities of 60 and 80 tons. The installation of production piles began on November 1, 2018 and will be completed on January 31, 2019.