Many people may not be aware that increased demands for land use and population in megacities are forcing increased amounts of construction to occur near active fault lines.
The construction industry is facing significant challenges and risks when operating near/on Australia’s thousands of fault lines – located mainly in Western Australia, Central Australia and along the East Coast.
Historical field observations show how, for example, the 2004 Indian Ocean earthquake and tsunami killed more than 200,000 people in 14 countries when a 1600 kilometre long fault ruptured for about 15 metres.
The 2008 Sichuan earthquake (which occurred in China, and left approximately 70,000 dead), the 1999 Chi-Chi earthquake (occurred in Taiwan, and left over 2000 dead) and the Düzce-Bolu earthquake (in Turkey, and left over 500 dead) show the vulnerability of surface structures – especially those resting on piles – to fault rupture incidents.
However, researchers at the University of Technology Sydney have found an innovative and inexpensive solution to protect buildings against fault rupture.
Led by Associate Professor Behzad Fatahi and supported by Habib Rasouli, PhD Candidate at the Centre for Built Infrastructure Research, the research contests the idea that construction should not occur in regions where fault rupture is a major threat to buildings.
The innovative foundation system allows for the construction of high-rise buildings on or near active fault lines. The researchers have also developed an advanced three-dimensional computer model which can be used to evaluate the performance of this new foundation to protect a high-rise building against fault rupture.
Dr Fatahi said design codes are strict about not allowing building construction near fault lines and usually impose a setback zone from the fault trace to avoid ruptures of structures.
“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,” he said.
Then there is the problem of determining the exact location of a fault outcrop. Engineering experience has proven that this cannot always safeguard buildings, as in the 1999 Kocaeli earthquake (Turkey) for instance, when a fault rupture incident caused significant destruction in the region.
Dr Fatahi said pile foundations are widely used in engineering practice to construct high-rise building sitting on soil deposits.
“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.”
“When subjected to a fault rupture incident buildings sitting on the conventional pile foundations suffer significantly from tilting, while foundation failure is also observed.”
“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,” Dr Fatahi commented.
Proving the possibility of safeguarding buildings sitting on their novel foundation, the new foundation system is detailed in an online article in ‘Computers and Geotechnics’ and can be found here.