阿拉善额济纳地区公路盐胀病害成因分析

Analysis of desert highway expansion caused by the excessive salt content in Ejina of Alxa Area,Inner Mongolian

阿拉善额济纳地区位于内蒙古自治区西北寒旱区,其境内哈温段与达来呼布至策克口岸省道S315部分路段在路面横向上不间断出现类似"天然减速带"的病害现象,严重处路面横向凸起高度约10cm,对行车安全构成极大危险。对病害路段基层、路基不同深度试样及路基坡面试样的化学成分进行了分析。结果表明,试样中氯离子质量分数与硫酸根离子质量分数之比小于0.3,硫酸盐盐渍化明显,为典型的硫酸盐渍土,盐渍化程度与路面横向凸起幅度相吻合,凸起幅度愈大,平均含盐量愈高,受日照持续时间长、强度大的路基西坡面路基土含盐量明显大于东坡面含盐量,氯离子质量分数远小于硫酸根离子质量分数,氯盐对硫酸钠盐渍土膨胀的抑制作用并不明显,可见阿拉善额济纳地区特殊的气候环境条件与工程地质条件使得路基土逐渐硫酸盐渍化并发生盐胀,是额济纳地区已建公路产生横向凸起病害的重要原因。

The present article is inclined to bring about an analysis of the desert highway expansion phenomenon caused by the excessive chloride content and sulfate ion content in Ejina of Alxa Area,Inner Mongolian,which is located in the northwest area of the Autonomous Region.Since the local climate is cold-dry for most of the year,the highway defects,like the ＇natural deceleration strips＂ tends to come about continuously in the Hami-Ondor Letu section and some sections of the Regional-level highway S315 from Dalaihubu to Ceke Port in the area of Ejina of Alxa.The transversal convex sometimes tends to be as high as 10 cm at some sections of the roadway,thus turning to be prone to serious risks for the traffic and transportation.The chloride content and sulfate ion content in some places may result in a rate of less than 0.3 due to the typical sulfate salt soil and sulfate salinity,which can be found via the chemical analysis and testing of the samples from the local soil base at the different depths of the subgrade and slopes at the defect sections.In some places,the salinity degree may coincide with the convex heights.The salt content of the west sub-grade slope has been found noticeably higher than the salt content of eastern subgrade slope with longer and stronger sunshine time and greater intensity,which helps to reduce the chloride content remarkably than the sulfate ion content and make the concentration of chloride and sulfate ions less than 0.3,far less than the optimal concentration of the expansive inhibition of chloride on the sulfate salty soil（the ratio of chloride and sulfate ion can be found between 4 and6）.Thus,the special climate conditions,the hydrological features,the geological and engineering geo-conditions of the area tend to accelerate the gradual sulfate salinity with the expansion of the gradually formulated sodium salt crystals.Thus,the transverse convex defects of the highways tend to come about in the Ejina Area.