The ripples from the 9.0-magnitude earthquake and ensuing tsunami that leveled the Tohoku region of Japan on March 11, 2011, are still being felt in civil engineering, notably in the updating of standards.
When COPRI’s Task Committee on the Seismic Design of Bulkheads met last week in San Diego, Japan factored into the conversation.
When COPRI’s Standards Committee meets next week in Seattle to work on ASCE/COPRI 61.19–Seismic Design of Piers and Wharves Standard, Japan will factor into the conversation.
“The lessons that we’ve learned and continue to learn are finding their way into ASCE/COPRI standards for seismic analysis of ports,” said Steve Dickenson, Ph.D., P.E., D.PE, M.ASCE, who recently joined professor and chair of the civil engineering department at Clemson University James Martin, Ph.D., M.ASCE, in leading a research team to Japan in conjunction with Japan’s Port and Airport Research Institute to observe the affected ports and harbors four years after the event.
“Our efforts with PARI are really paying dividends. It’s a very fruitful professional exchange. Our working relationship with PARI has been one of the most fulfilling and rewarding of my professional career.”
Dickenson began working with PARI (then the Port and Harbor Research Institute, PHRI) in the early 1990’s. Efforts intensified in 1995 after the 6.9-magnitude Hyogo-ken Nambu Earthquake in Kobe, Japan. He returned in June 2011, leading one of two ASCE-sponsored post-earthquake reconnaissance teams that partnered with Dr. Takahiro Sugano and his colleagues of PARI.
Dickenson and Martin’s return trip this summer, almost exactly four years later, was all about updating the lessons learned.
“Our goals were really to see how the rebuilding and reconstruction had gone and then glean whatever lessons we could; find out what PARI learned from this big event,” Dickenson said.
What they found was the picture of resiliency. Many of the most vital berths in the earthquake-damaged ports reopened in late 2012, while many of the others are being rebuilt stronger than before.
“I think the first thing that amazed both Jimmy Martin and myself was the overall resiliency of their port system and the speed with which they rebuilt,” Dickenson said. “They definitely fast-tracked the repair of certain key berths. Obviously, they prioritized where they put their resources in rebuilding.”
Maybe most impressive was the town of Onagawa, a fishing port of about 6,000 on the east coast of Japan. It suffered extraordinary tsunami damage in 2011. Four years later, the town has essentially moved uphill, reconfigured with rebuilding occurring on elevated grades of deep fills and further up native slopes. The waterfront portions of the harbor are largely rebuilt, and reconstruction of buildings and supporting infrastructure and utilities underway.
“To go to that area and look down from the adjacent hills and see what they’re doing is quite amazing,” Dickenson said. “The amount of work that they’ve done really is stunning.”
Dickenson and his ports-recon team took special note in 2011 of the earthquake damage due to seismic shaking. This effort was complemented by COPRI’s other port recon team led by Marc Percher, P.E., M. ASCE, which also focused on tsunami damage to port
facilities. The use of soil improvement to mitigate liquefaction hazards and the seismic performance of waterfront structures taught valuable lessons.
“We’ve learned a lot from our colleagues at PARI about how ground-treatment methods have been enhanced and how they’re being used at port and harbor facilities,” Dickenson said. “The engineers at PARI are coming up with rather innovative pile-supported structures as well.”
With respect to soil improvement, the waterfront structures supported with backfill that had been densified or cemented with various forms of grout – so as to avoid liquefaction – held up much better under the seismic loads generated by the earthquake than those that weren’t.
Dickenson estimates that research on the 2011 Tohoku earthquake and tsunami involving engineering seismology, coastal and port engineering, lifelines engineering, and national resilience to natural hazards will continue another decade at least. PARI will soon release its comprehensive report on the impacts of the earthquake and tsunami, providing an essential resource for on-going applied research addressing the seismic performance of ports.
“This clearly was one of the biggest events of our lifetime,” Dickenson said. “For earthquake engineers, tasked with trying to model, simulate, and estimate what the seismic performance of what a structure will be, we learn a tremendous amount from case studies. There’s no better laboratory than the field.”