高密度电法对不同溶洞探测效果模拟

Simulation Study on Detection Effect of Different Karst Caves by High Density Resistivity Method

在高密度电法勘探中,不同性质的溶洞其反演电阻率特征有差异,往往会导致实际勘探出现困难。根据实际地质情况建立了三个溶洞模型:充水型溶洞、充泥型溶洞及未充填型溶洞。对三个溶洞模型进行数值模拟,对比了不同模型的地电响应特征;然后对每个溶洞模型表面增加一层破碎状溶壳,分析了溶壳对溶洞正反演结果的影响;最后将实际资料与数值模型结果对比分析,进而解释了实际资料中溶洞异常特征产生的原因。结果表明:充填型溶洞在反演结果中的反应比未充填型溶洞灵敏很多,破碎状溶壳对未充填型溶洞探测效果的影响远大于充填型溶洞,破碎状溶壳包围的空洞在反演结果中表现的异常形态不明显,在野外实际探测中很难准确探测。

In high-density electrical prospecting,Karst caves may show different electricity resistivity characteristics due to the nature of cave fillings,which often leads to difficulties in actual exploration.Based on the measured data,three Karst cave models were established,including water-filled Karst cave,mud-filled Karst cave and unfilled Karst cave.Three Karst cave models were numerically simulated and the electrical response characteristics of different models were compared.Then,a layer of broken shell was added to the surface of each Karst cave model,and the influence of the shell on the results of Karst cave was analyzed.Finally,the actual data and numerical model results were compared and analyzed,and the causes of the abnormal characteristics of the Karst cave in the actual data were explained.The results show that the reaction of filled Karst cave in inversion results is much more sensitive than that of unfilled Karst cave,and the effect of broken shell on the prospecting of unfilled karst cave is much greater than that of filled karst cave,the abnormal shape of the cave surrounded by the broken shell is not obvious in the inversion results,therefore,it is difficult to detect accurately in practice.