风雪复合侵蚀路基孔隙特征的微细观试验研究

MICRO-MESOSCOPIC EXPERIMENTAL STUDY OF POROSITY CHARACTERISTICS OF EMBANKMENT SUBJECTED TO WIND AND SNOW EROSION

风雪复合侵蚀作用是自然环境中的风、融雪和温度共同作用的结果。以内蒙古那—苏省际大通道锡林郭勒盟桑根达来段的风沙土填方路段为例,考虑不设边坡防护的裸边坡为最不利情况,利用光学显微镜测试技术,并结合数字图像相关方法,通过定义土体孔隙面积比率,对土体侵蚀前后孔隙分布特征进行定量分析,分析路基填料经历冻融风蚀复合侵蚀作用后,各测试层的影响深度,以及各测试层孔隙面积比率与融雪下渗引起的冻融侵蚀和风蚀之间的关系。测试结果表明,路基坡肩处受到复合侵蚀的影响最大,复合侵蚀影响深度约为1/6倍路基模型高度。在经受3次冻融风蚀后较未侵蚀时,坡肩处的孔隙面积比率增加了50.1%,且自坡肩向坡脚处逐渐减小,在坡脚处孔隙面积比率仅增加了30.7%。相同循环次数下,风蚀对路基坡肩的结构损伤大于融雪下渗引起的冻融损伤。

Wind and snow erosion is due to the combined effect from the action of wind blowing,snow melting and temperature varying. The unprotected embankment filled with Aeolian sandy soil of the Inner Mongolia-Sue provincial highway located in the section of Sanggendalai in Xilingol League was studied in wind tunnel test. The characteristics of the soil porosity were analyzed using the optical microscope combined with the digital image method. The pore area ratio was defined and the quantitative analysis of porosity characteristics was conducted before and after the wind-snow erosion. The affected depths by the wind-snow erosion from the slope surface at the different testing layers were obtained. The relationships between the pore area ratio of each tested layer and the freeze-thaw erosion from the melt snow infiltration and the wind erosion were established. The measured results showed that the shoulder was most seriously affected,and the effect of wind-snow erosion decreased from the shoulder to the toe of the embankment. The maximum influenced depth at the embankment shoulder was found to be about 1/6 times of the model height. The pore area ratio at the embankment shoulder increased by 50.1%while the pore area ratio at the embankment toe increased only 30.7%after three cycles of wind-snow erosion. For the same erosion cycles,the structure damage due to the wind erosion on the embankment soil was shown more severe than the one due to the freeze-thaw erosion.