摘要:
截止2016年底,大成桥疏干区在地下水位恢复过程中共发生了17起岩溶塌陷,文章结合地下水动态监测、水文地质钻探成果以及现场调查资料等,研究地下水恢复特征及其对岩溶塌陷的作用机制,为研究区塌陷的预警防治提供科学依据.结果表明:研究区岩溶塌陷集中在河流两岸阶地和麻枣冲沟中;岩溶塌陷发生顺序为先补给区后径流区,与地下水恢复动态过程密切相关;区内地下水恢复过程可分为4个阶段,不同阶段岩溶塌陷机理可分为渗流潜蚀-气爆效应,负压吸蚀效应,软化增荷-挤压-吸蚀效应和软化-崩解效应等4种力学效应组合,不同力学效应作用下的致塌模式有所不同.其中地下水位在基岩面附近4~5m 范围波动更容易引发岩溶塌陷.目前补给区地下水位标高63.95~71.8 m,高于基岩面5~6 m;径流区为42.8~57.7 m,位于基岩面以下4~17 m,因此须密切观测研究区地下水位变化.
Abstract:
By the end of 2016,17 sinkholes have occurred in Dachengqiao drainage area during groundwater level restoration process.Based on previous research results,through monitoring of groundwater level dy-namic characteristics,hydrogeological and engineering geological drilling and field investigation,this paper studied the characteristics of groundwater restoration and its mechanism on sinkhole formation,which has provided scientific basis for early warning and prevention of ground subsidence in the study area.The results show that,(1)sinkholes are mainly distributed at river terraces and Mazao gully.Sinkholes firstly occurred at recharge area and then runoff area,which has a close relationship with the groundwater dynamic change.(2) The groundwater restoration process can be divided into four stages.The formation mechanisms of the sink-holes can be summarized as the creep seepage and air burst effect,suction effect,soften and suction effect and soften and degradation effect based on these four stages.The collapse patterns are the combination of gravitation-,erosion-,vacuum cavitation-and burst-collapse.It is found that the groundwater level fluctuata-tion in the range of 4-5 m to the surface of bedrock may cause sinkhole more easily.Currently,the ground-water level in the recharge area is 63.95-71.80 m,which is 5-6 m above the bedrock surface,and the groundwater level in the runoff area is 42.8-57.7 m which is 4-17 m below the bedrock surface.There-fore,it is necessary to closely observe the changes of groundwater level.
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