大布苏湖岸泥林地下潜流破坏成因

摘要

针对大布苏湖东岸发生的土体坍塌与泥林的成因,开展地下潜流来源及破坏机制研究.结果表明:土壤中上层大于下层的盐分分布排除了降水入渗补给地下水的可能性;同位素分析结果证实,大布苏湖水来自于地下水的补给,地下潜流来自于周边河流的渗漏.渗漏水通过黄土层下伏的粉砂层向大布苏湖中排泄,这成为泥林不断扩张的原因之一:粉砂层之上黄土中的风尘颗粒不断地被潜流带到湖泊,在黄土层下部形成孔洞,逐渐发展并最终形成塌陷.此外,冻融作用也进一步加剧了渗透破坏程度.地下潜流、细颗粒流失与冻融作用是造成土体破坏的主要原因,防止细颗粒流失与冻融作用发生是预防土体进一步破坏的关键因素.%To explore the causes for the loess collapse and the mud forest formation in the eastern bank of Dabusu Lake,the source and failure mechanisms for subsurface flow were studied.The results show that,according to the salt content of topsoil larger than that of subsoil,precipitation infiltration cannot recharge the underground water.Isotopic analysis results indicate that Dabusu Lake is mainly recharged by groundwater,and subsurface flow comes from the seepage of surrounding rivers.Leak water of rivers discharges towards Dabusu Lake through the silt layer beneath the loess layer,which is one of the reasons for the development of mud forest.The dust particles of loess above the silt layer are taken into the lake by subsurface flow,forming cavities on the bottom of the loess layer and finally resulting in collapses.Besides,the freeze-thaw action also aggravates the seepage failure.Subsurface flow,fine particle loss,and freeze-thaw action are the main reasons for loess failure,and avoiding fine particle loss,and freeze-thaw action is the key to preventing the development of loess failure.