What
Happens? Port and Harbor Facilities Are Damaged
Excerpts
From "The REAL Dirt on Liquefaction"
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What
Happens? Port and Harbor Facilities Are Damaged
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Excerpts
From "The REAL Dirt on Liquefaction"
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| What Happens? |
Ports and harbors are often built on artificial fill. In the Bay Area, this fill has typically been placed over Bay mud, which amplifies earthquake shaking. Ports consist of bulk storage facilities and warehouses, cranes to move large containers (typically on rails), and rail and other facilities that serve to connect the port to the land-side transportation system. Liquefaction can cause large areas to sink below the water surface. Rails can buckle, become misaligned, and rotate. Pavement surfaces also buckle, often in ways similar to roadways and airport runways. |
| Why Does This Happen? | Lateral spreading is a major problem with ports and harbors because the liquefied layer or material above the liquefied layer, even if virtually a flat-lying surface, can move toward the waterfront. Additional damage occurs due to ground oscillation and differential settlement, as described in Part I. |
| How Vulnerable Were Our Ports in the Loma Prieta Earthquake? |
The Port of Oakland handles 95% of the container cargo that travels under the Golden Gate Bridge, as well as some break-bulk, bulk liquid, and bulk dry cargo (personal comm., G. Joseph, Port of Oakland, September 2000). Damage to port facilities in 1989 was due primarily to liquefaction of the hydraulic fill. The most extensive damage was to the 7th Street Terminal, although the Howard, APL and Matson Terminals were also affected. Yard areas settled up to one foot relative to the pile-supported crane rails (EERI, 1990, pp.97-103; Kayen and others, 1998, pp.B69-B71). |
| How Vulnerable Was the Port in the Kobe, Japan Earthquake? |
The Port of Kobe, Japan is one of the largest in the world, and handles over ten times the cargo of Oakland. Kobe's port suffered major damage as a result of the 1995 Kobe (Hyogo-Ken Nanbu) earthquake. The three main facilities consisted of perimeter quay walls filled with granular hydraulic fill on sea-bottom clay. As a result of the earthquake, large sections of wharf and warehousing areas sank and were covered with water. "Approximately 50 cranes [had] significant structural damage, … primarily due to the rails spreading and settling. …Even if the design had conformed to the current practice, severe damage may have occurred. But it would have been less" (EERI, 1995b, pp.71-72). Damage to the Port resulted in increased business at ports in Yokohama, Osaka and South Korea, in spite of the billions funneled into recovery. After three years, 10% - 15% of the business had not returned to Kobe (personal comm., G. Selvaduray, 2000). |
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| 1995
Kobe Earthquake - Example of damage to port facilities Source - Kobe Geotechnical Collection, Earthquake Engineering Research Center, University of California, Berkeley |
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| How Does the Port of Oakland View Its Vulnerability to Future Earthquakes? | The Port of Oakland conducted studies of its vulnerability after both the 1989 Loma Prieta earthquake and the 1995 Kobe earthquake. The Port of Oakland experienced about 0.3 g peak ground acceleration during the 1989 earthquake, while the Port of Kobe experienced approximately 0.8 g, a significantly higher amount (Kayen and others, 1998, p.B61; EERI, 1995b, p.69). The Port of Oakland's studies show that, in comparison to Kobe, the soils in Oakland are muddier and less sandy. In addition, the Port of Oakland uses pilings, ranging from 20 to 100 feet in depth, rather than caissons - with the pilings considered a sounder approach. The 29 deep water berths in Oakland are 35-45 feet deep in comparison to Kobe where they are greater than 100 feet deep (personal comm., Mark O'Brien, Port of Oakland, 1995). The Port is in the process of analyzing the existing soil conditions for many of its existing berth embankments and local backlands at a cost of approximately $850,000. The evaluation will include the current seismic capacity of the embankments and local backlands, as well as what increasing level of soil improvements would be necessary to withstand increasing levels of seismic activity. Although these studies are not just for liquefaction, liquefaction is an integral component of the hazard assessment (T. LaBasco, Port of Oakland, 2000). The Port has a fundamental priority to remain in business and operational. It is concerned about permanent loss of business following a Bay Area earthquake to Seattle, Long Beach and Vancouver. |
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1989
Loma Prieta Earthquake - Port of Oakland 7th Street Marine Terminal
Source - R. Kayen, U.S. Geological Survey and Loma Prieta Collection, Earthquake Engineering Research Center, University of California, Berkeley |
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