A new foundation system could allow high rises to be built on or near active fault lines, according to new research from the University of Technology Sydney.
The research, led by Associate Professor Behzad Fatahi and supported by PhD Candidate Habib Rasouli at the Centre for Built Infrastructure Research (CBIR), the research argues against industry wisdom that construction shouldn’t occur in regions where fault rupture is a major threat to buildings.
The team has developed a new foundation method that allows for construction of large buildings on or near active fault lines and an advanced three-dimensional computer model to evaluate the performance of the new foundation.
It comes following increasing demand for land use and population in mega cities such as Tokyo.
Australia has thousands of fault lines, distributed mainly in Western Australia, Central Australia and along the east coast, which pose potential risks to construction.
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To overcome the current weaknesses of current foundation methods on fault lines, the team propose including a gap between the base of the building and concrete piles, which is then filled with sand.
During a fault rupture, these piles could then easily separate from the base of the building or slide without dragging the building down, potentially reduce excessive building tilting and foundation failure.
“Design codes are strict about not allowing building construction in the vicinity of fault lines, and usually impose a setback zone from the fault trace to avoid ruptures cross structures,” Fatahi said.
“Although a setback zone might be the best option, it is not always feasible as a safeguard for buildings, due to contemporary increases in population growth and land-use demand. Therefore the ‘business as usual’ view of avoiding construction in the vicinity of an active fault line needs reconsideration.”
Fatahi said there is also difficulty finding the exact location of the fault outcrop.
“Pile foundations are widely used in engineering practice to construct high-rise building sitting on soil deposits,” Fatahi said.
“While this type of foundation could successfully and safely transfer the massive loads of superstructure to the ground, its performance under a fault rupture incident would be unacceptable and catastrophic, as seen in the collapse of a basketball stadium in Denizevler during the Kocaeli earthquake.
“Problems occur in a common pile foundation when the fault outcrops in the middle of the foundation, the moving tectonic plate or block drags the piles down, while the other piles remain within the static tectonic plate. This mechanism causes significant structural distress, building tilting, foundation failure and buildings to shear off.”