Abstract: Aeolian activity is one of the most important threats to the safe operation of the transport lines in sandy areas. The Qiaha Bridge,located in Cele County,South Xinjiang,Northwest China,is one important transport node in G315 National Highway. It was built in a gobi desert in the northern slope of Kunlun Mountains and south fringe of the Taklimakan Desert. Though there were very frequent aeolian activities,the elder Qiaha Bridge operated safely in past several decades,but the newly-built Qiaha Bridge was seriously damaged by sand disaster. A field investigation and theoretical analysis concerned with sand disaster of new Qiaha Bridge were conducted in 2011. The sand disaster in the form of sheet-like sand deposition was resulted from the disturbance of sand particles' motion in air flow by morphological changes on the ground surface due to engineering construction,so airflow reduction triggered that most of sand particles were deposited from air flow and further piled up. Actually the sand disaster occurrence is closely related to some details of bridge construction such as stepped road transverse section,unsuitable road safety guardrail,and windtight bridge guardrails. According to the cause of sand disaster, we put forward a series of sand-controlling countermeasures suitable to local conditions. Firstly,some sand source controlling measures such as sand prevention,guide and stabilization should be constructed in the windward side of Qiaha Bridge. Secondly,some microenvironment rehabilitation measures including cross-section grade elimination,wind-gathering board on road shoulder,and displacement of w-beam guardrail with cable guardrail should be settled in order to reduce the wind resistance and increase sand transport capability of wind flow. Thirdly,some hidden troubles of sand disaster such as reed fences original settled at subgrade slope toe and sand deposit around it should be removed.

Key words: sand deposition on road, road cross-section, safety guardrail, sand-controlling countermeasures