Can buildings stand against earthquake fault rupture?
There are thousands of fault lines in Australia, mainly distributed in Western Australia, central Australia and the east coast. Construction near or on fault lines presents a significant risk to buildings.
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It is an old belief that we cannot build structures on the borders of tectonic plates known as fault lines. Active faults can break through the ground surface and generate a widespread ruptures. The 2008 Sichuan earthquake in China, where about 70,000 died, showed the vulnerability especially where piles rest against fault ruptures.
Most design codes do not allow building construction in the vicinity of fault lines, and usually have a setback zone to avoid ruptures cross the structure. Although this might be the best option, it is not always feasible due to population growth and dramatically increasing land use. Moreover, the experience over two decades has proven that this criteria is not always sufficient since finding the exact location of fault outcrop is often difficult.
Pile foundations are widely used to construct high-rise building sitting on soil deposits. Although these can transfer the massive loads of a superstructure to the ground, their performance in a fault rupture can be catastrophic, such in 1999 when the basketball stadium in Denizevler, Turkey collapsed during the Kocaeli earthquake.
The buildings, sitting on conventional pile structures, were subjected to a fault rupture and suffered from tilting and foundation failure.
The problem with common pile foundations is 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 on the static tectonic plate. This creates structural distress, causing the building to tilt, foundations to fail, and even shear off.
Now a team of researchers at UTS, led by myself and PhD candidate Habib Rasouli, have recently found an inexpensive solution to protect buildings. Our team has proposed a new foundation where a sand cushion is placed between the building and concrete piles. That forms a gap between the base of the building and concrete piles. During fault rupture, the piles can separate from the base of the building or slide without dragging the building down.
We have developed an advanced three-dimensional computer model to evaluate the performance of this system. Our findings show that buildings sitting on this novel foundation could be safeguarded against fault rupture, and safely located on or near active fault lines.
Response by: Associate Professor Behzad Fatahi, University of Technology Sydney (UTS)
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