Screening guide for rapid assessment of liquefaction hazard at highway bridge sites

ABSTRACT

Liquefaction-induced ground and foundation displacement has been a major cause of earthquake damage to bridges. For example, during the great Alaskan earthquake of March 27, 1964, liquefaction-induced lateral ground displacement inflicted structural distress to 266 railway and highway bridges, collapsing about 20 and damaging many others beyond repair. This destruction primarily at river crossings, disrupted the surface transportation system in southern Alaska for many months after the earthquake. Numerous other occurrences of bridge damage or collapse have occurred around the world as a consequence of liquefaction. These types of deposits and terrain are highly vulnerable to liquefactionand lateral spread. Because of the high potential for bridge damage and consequent disruption to transportation systems evaluation of liquefaction hazard is a major part of any assessment of seismic hazard to highway systems As an aid to seismic hazard assessment this report provides a "screening guide" for systematic evaluation of liquefaction hazard at bridge sites and a guide for prioritizing sites for further investigation or mitigation. This guide is intended for use by highway engineers with experience in geotechnical engineering practice, but not necessarily specialized knowledge in seismic hazard evaluation. Only sites with significant hazard need tobe evaluated with the more sophisticated and time consuming-procedures. If there is clear evidence that liquefaction or damaging ground displacement are very unlikely, the site is classed as "low liquefaction hazard and and low priority for further investigation" and the evaluation is complete, or unclear, the site is classed as having possible liquefaction hazard and the screening proceeds to the next step. If the available site information is insufficient to complete a liquefaction hazard analysis, then simplified seismic, geologic and hidrologic criteria are used to prioritize the bridge site for further investigation (AU)