Key Point of Bridge Damage Caused by Glacial Debris Flows along International Karakorum Highway, Pakistan

Glacial debris flows along International Karakorum Highway (KKH) connecting northern Pakistan with China, are always causing so extreme threats to a majority of bridges built along KKH. So the improvement project of KKH has been being carried out by China Road & Bridge Corporation in 2008. However it is necessary to collect the detailed data about the damages to bridges and obtain the most dangerous key position. The series of field investigations from 2008 to 2011 demonstrate that the damages are classified into four categories: deposition under bridge, abrasive erosion, impact on piers or abutment and collapse due to buoyancy. Statistics indicate deposition under bridge is the most dominant damage whereas the most serious damage is the impact on piers or abutments. Therefore a case study on key point is made for the typical bridge subjected to impact from Ghulkin glacial debris flow. Finally prevention measures are given.