苏坡店沟“7·10”泥石流破坏都汶公路毛家湾大桥机理

Abstract

The catastrophic debris flows on July 10，2013 resulted in huge destruction to Dujiangyan － Wenchuan highway ( G213) in Sichuan Province of China． The highways were seriously destructed and blocked in 16 sites， which were induced by 7collapsed bridges and base，2 of 7 destructed were scoured by debris flow． Based on field investigation and analysis，the parameters were calculated，which were the density of 1． 88 g /cm3，the velocity of 9． 3 m/s，the peak flow of 232． 5 m3 /s，and yield stress of debris flows1of 13． 3 kPa． The debris flows scoured the foundation of the bridge down the steep gully seriously，the pier lost its stability and the bridge collapsed． The calculation indicates that: the soil below the pier is scoured away by the debris flow leading to the pier overhanging， and the lateral length reaches 1． 65 m; on the other hand，the water in debris flows should run into the foundation soil，which reduces the soil’s strength． The pier failed when the maximum pressure( 545 kPa) of the foundation exceeding the allowable bearing capacity，then the bridge destroyed． By the analysis of the failure model and mechanism of Maojiawan Bridge，it suggests that debris flow drainage channel; clearance under the bridge and special protective projects should be carried out for highway protection and traffic security．