315国道策勒恰哈桥段风沙灾害成因初步分析与治理对策

Causes and thoughts of comprehensive control of blown sand disaster at Qiaha Bridge of National Highway 315,in Cele County,Xinjiang,Northwest China

风沙活动是沙区交通线路安全运行的重要威胁。315国道策勒恰哈新桥建成以来,桥(路)面积沙严重,道路通行状况恶化,严重影响交通安全。实地调查发现,该区风沙灾害主要形式是路面片状积沙。根据路况和周边环境条件,结合风沙运动理论,认为沙害主要成因是工程建设大幅改变地表形态和结构,使过境风沙流被强烈扰动而形成滞留积沙,其中台阶式道路横断面、公路波形护栏和不透风桥栏是诱发沙害的关键工程建设因素。最后提出了因地制宜的沙害治理思路,具体措施包括阻-导-固结合的沙源控制、原有路边阻沙堆积隐患的清理、横断面改造以及公路护栏改造。

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.