Safety Evaluation Of The Sixaerial Crossing Structure Of A Pipeline In Northwest

A section of a pipeline in Northwest adopting spiral welded steel pipe with outsideanti-corrosion insulation layer has been put into production operation for many years. Thepipeline is located at longdong loess plateau with complex terrain and poor geologicalcondition for class II weight of collapsible loess region. Gully is caused by the water and rainerosion and the ditch slope is instability.Moreover, the loess cave is more and collapse of soilis serious. The pipeline uses the cross ditch when passing a big gully in which the cross1,cross2and cross3,4is span around for suspension type and across5, across6across isrsuspension cable type.The six span structure in the pipeline were put into use since the last century by the year70, served for more than30years. In2001years, the relevant units carried on the fieldinvestigation and comprehensive improvement of the above two cable span structure. Surveyfound much problem,such as tower corrosion, derrick and steel beam tilt, armrest wirecorrosion, embrittlement, damage and wind cable corrosion is serious, such as individualbroken wire damage and failure mode.The project ‘s research object is the suspension cable span structure and suspensioncable span structure. Through scientific and effective field detection technology and finiteelement analysis method in the laboratory and the overall safety evaluation technology of sixcrossing tower, anchor pier structure, main cable, cable, wind cable and so on maincomponents were studied. The results show that: the six span structure basically meet allkinds of standards which can continue to use. But for the pipeline safe operation for a longtime, it is suggested that replacement of over1,2,3,4,5, and6across the structure of themain cable.The foundation J3surrounding soils of cross1and cross2should be consolidated.The cable anchor pier MD3MD4of cross3and4foundation should be rectified and reformed because it can not meet the requirements. Wind cable structure should be added for cross5on account of the horizontal displacement of the main cable becoming larger by enduring ahorizontal wind load condition.Also it is necessary to strengthen the routine maintenance andto fill anti-corrosion paint to each spanning structure and to tighten loose bolts.