地下水位变化对透-阻型岩溶塌陷影响的分析  

Analysis of seepage effect on the formation of sinkhole in unconfined aquifer-aquitard system caused by groundwater changes

作　　者：陶小虎[1] 赵坚[1] Xiaoming Wang Ming Ye Roger Benito Pacheco Castro 

机构地区：[1]河海大学水利水电学院,南京210098 [2]Geophysical Fluid Dynamics Institute,Florida State University

出　　处：《中国岩溶》2017年第6期777-785,共9页Carsologica Sinica

基　　金：国家自然科学基金项目(51279045);江苏省普通高校研究生科研创新项目(CXZZ12_0246)

摘　　要：文章从一维地下水运动和渗透力学的角度,分析比较潜水位上升与承压水位下降对岩溶地区透—阻型盖层中阻水层渗透稳定性的影响,重点讨论了承压水位下降速度(降速)与下降深度(降深)对阻水层中渗透坡降的影响,结果表明:地下水位变化(潜水位上升或承压水位下降)产生的非稳定渗流不利于岩溶洞穴开口上方阻水层的稳定,承压水位的下降对岩溶开口附近处阻水层中渗透力的影响远大于潜水位的变化;在承压层水位最大降深确定的条件下,承压水位下降速度愈快,岩溶开口附近处阻水层中向下渗透力愈大。因此,在覆盖型岩溶地区抽取地下水时,为了减缓或避免覆盖型塌陷的发生,应同时控制好最大降深和最大开采速度。Cover-collapse sinkholes are an extremely complex process that often cause unpredictable geolog- ical disaster. They occur abruptly and can lead to catastrophic damages such as human death and injury, property damage, losses of soil and water and environmental problems, as well as may cause secondary disaster. Groundwater is one of the crucial triggering factors for sinkhole development and collapse. To have a better understanding of the mechanical effect of groundwater on sinkhole formation, the force exerted by the groundwater on the soil particles in saturated zone with porous medium was analysed. In this case, the entire hydraulic force acting on the soil particle by groundwater depends on the seepage force or the value of hy- draulic gradient which causes the velocity of groundwater movement. A 1D groundwater flow model was simply established, where the unconfined aquifer-aquitard system overlies the confined aquifer, in order to study the hydraulic gradient distribution in the confining unit. The differences between the effects of the phreatic level arising and piezometric level lowering were compared. Moreover, the effects of drawdown rate and drawdown of piezometric level in confined aquifer on the confining unit were mainly discussed. The re- suits show that groundwater movement with variation of the water table or piezometric level in karst area will erode and disintegrate the soil, resulting in the formation of soil cavity and upward propagation of the e- rosion. The unsteady seepage due to groundwater level fluctuations goes against the stability of the confining layer above the karst opening; the impact of seepage force resulting from piezometric level lowering is greater than that of the phreatic level arising; the size of the soil cavity formed is related to the degree of the decline of piezometrie level which is also influenced by the decline rate; under the conditions with the same piezomet- ric level declines in the confined aquifer, the higher the drawdown rate is, the larger the maximum hydrau

关 键 词：透—阻型 岩溶塌陷 渗透力 一维地下水流 潜水位上升 承压水位下降 降速 

分 类 号：P642.26[天文地球—工程地质学] P641[天文地球—地质矿产勘探]