NEAR FAILURE OF THE ALL AMERICAN CANAL IN SOUTHERN CALIFORNIA DUE TO A 7.2 MAGNITUDE EARTHQUAKE IN APRIL, 2010

摘要

On Easter Sunday, 2010, a 7.2 magnitude earthquake struck northern Mexico nearMexicali. The All-American Canal, which diverts Colorado River water from theImperial Reservoir and delivers irrigation water throughout the Imperial Valley, washeavily damaged. The canal parallels the California/Mexico border and the siphoncarries water across the New River in southern California only 22 miles from theearthquake epicenter. The earthquake damaged the concrete canal lining, separatedvertical and horizontal joints at the inlet of the siphon and wasteway, liquefied materialsin the New River channel, and opened up wide cracks and fissures in the 40-foot-highembankment fill and riverbank supporting the canal, gate structure, siphon and wasteway.Concentrated seepage was observed exiting near the toe of the embankment fill betweenthe siphon and the wasteway. Many aftershocks occurred, but the seepage remainedsteady for another week after the April 4~(th) main shock. Eight days after the initialearthquake, the quantity of seepage suddenly increased approximately ten fold. Thatevening a significant aftershock of 4.8 magnitude occurred, and the seepage increasedeven more causing internal erosion of embankment materials to begin in earnest. Thispaper discusses the incident, what mitigation actions were taken that night to save thesiphon structure, follow-up investigations and continuing engineering studies.