What
Happens? Highways, Roads, and Airport Runways Buckle
Excerpts
From "The REAL Dirt on Liquefaction"
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What
Happens? Highways, Roads, and Airport Runways Buckle
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Excerpts
From "The REAL Dirt on Liquefaction"
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| What Happens? |
Highways, roads, and airport runways buckle. Pavement surfaces can be made impassable for most vehicles, and may need to be replaced. |
| Why Does This Happen? | Buckling occurs because of lateral spreading, ground oscillation, and differential settlement, as described in Part I. |
| What Were the Road Damage Statistics in the Loma Prieta Earthquake? |
Caltrans repaired approximately 10.5 miles (17 km) of damaged highway surface following the Loma Prieta earthquake at a cost of approximately $5.5 million. Data on costs of repairs to local roads are not readily available. Our review of road damage information from the Loma Prieta earthquake indicates that the percentage of highway road surfaces repaired for strong and very strong shaking intensities (MMI VII and VIII) ranges from 1.4 to almost 12 times greater for areas mapped as having very high liquefaction susceptibility than for areas of higher susceptibility. See Appendix C for more information. |
| Were Airports Affected by Liquefaction in the Loma Prieta Earthquake? |
Oakland International Airport (OAK) operations were affected by the Loma Prieta earthquake, in spite of its location over 40 miles from the fault source for the earthquake. The airport's main 10,000-foot runway, built on hydraulic fill over Bay mud, was severely damaged by liquefaction; 3,000 feet of the runway sustained cracks, some of which were a foot wide and a foot deep. Spreading of the adjacent unpaved ground resulted in cracks up to 3 feet wide. Large sand boils appeared on the runway and adjacent taxiway, a few as wide as 40 feet (EERI, 1990). As a result, OAK was immediately shut down to evaluate runway damage. A shorter 6,212-foot general aviation runway was used to accommodate diverted air traffic for a couple of hours before the main runway was reopened with a usable length of only 7,000 feet. This shorter runway length impacted cargo loads during takeoff. Over the 30 days following the earthquake, 1,500 feet of the 3,000 foot damaged section of the runway was repaired using an emergency repair order for resurfacing and crews already present during the earthquake. An adjacent taxiway was also damaged by liquefaction. Repairs of this taxiway segment and the final 1,500 feet of the main runway were completed six months later, after a competitive bidding process (T. LaBasco, S. Kopacz, and J. Serventi, Port of Oakland, personal comm., September, 2000). Repair costs totaled approximately $6.8 million, including $3.5 million for runway repairs, $2.2 million for taxiway repairs, and $1.1 million for repair of other (non-liquefaction related) damage. FAA funded approximately $5.5 million of the repairs, with the remainder funded by OAK (T. LaBasco and I. Osantowski, Port of Oakland, and J. Rodriguez, FAA, personal comm., September, 2000). Neither the San Francisco International Airport (SFO) nor San Jose International Airport (SJC) were impacted by liquefaction in the Loma Prieta earthquake. |
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| Liquefaction
damage in the 1989 Loma Prieta Earthquake at OAK Source - Geomatrix Consultants |
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Significant damage also occurred to the Alameda Naval Air Station. Substantial liquefaction led to the closure of both the 8,000-foot and 7,200-foot runways. The terminal building had structural damage and was closed. Other damage occurred to piers, railroad tracts on piers, and the water- and gas-distribution system. Power was not disrupted. Helicopter pads also were not damaged and were used during the emergency operation. The two runways were repaired and reopened (one in December 1989 and the second expected in January 1990) (EERI, 1990). However, the facility was closed in 1995 and is now scheduled for reuse. |
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1989
Loma Prieta Earthquake - Alameda Naval Air Station
Source - J. Bray, University of California, Berkeley and U.S. Geological Survey |
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| What Do We Expect Will Happen in Future Earthquakes? | It is usually not cost effective to retrofit roads, or even airport runways. If a future earthquake is more centrally located in the urban portion of the Bay Area, many more road closures and airport problems are expected than occurred as a result of the Loma Prieta earthquake. For example, while 17 of the 142 street and highway closures in the Loma Prieta earthquake, and 10 of the 140 closures in the Northridge earthquake were due to liquefaction, over 40 of the over 1600 closures in a Hayward fault earthquake may be due to liquefaction (Perkins and others, 1997 and Perkins and others, 1998). While 10+ miles of state highway had to be resurfaced after Loma Prieta due to liquefaction, we expect many more miles will need to be repaired after a Hayward fault event. Of more significance, all three commercial airports may be partially closed (Perkins, 2000). The potential problem with the Oakland and San Francisco International Airports is liquefiable fill on Bay Mud. The potential problem with the San Jose International Airport is that the runways cross a series of ancient stream channels. |
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Runway Program at the San Jose
International Airport
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| SJC is currently extending a shorter runway to create a new full-length runway that should be far less vulnerable to damage because the pavement section is sufficient to "bridge" the stream channels shown as particularly hazardous in the adjacent map. Upon completion of this project, the existing full-length runway will be taken out of service and reconfigured in a similar fashion. Both projects should be completed by 2004. (M. Wikowski, SJC, personal comm., 2000) |
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