高密度电阻率法单极——偶极装置探测石灰岩地区地下溶洞

Detection of Underground Caverns in Limestone Area by High Density Resistivity Pole-dipole Device

高密度电阻率测深法装置颇多,对称四极测深法是常用的。但在探测的靶区不具备对称四极装置工作的条件下,用单极—偶极装置测深也是很普遍。单极—偶极装置探测非层状地质体的视电阻率异常具有个性,认识它十分必要。探测层状地层结构和形态,测深法的各种装置的异常特征是一致的,资料解释也相近。但对低阻溶洞体,单极—偶极装置测深的异常特征与对称四级装置存在差异,资料解释也不相同。通过实际勘查工作,单极—偶极装置测深获得的低阻洞体异常,钻孔不能定在异常中心部位,而应定在单极一侧的低阻异常梯度带附近。实际探测和钻探结果验证了这一结论。

The high density resistivity sounding method has many arrays,and the symmetrical four-pole sounding is commonly used.However,there is no symmetrical four-pole in the target area,it is common to use pole-dipole devices for sounding.It is necessary to understand the characteristics of apparent resistivity anomalies of non-stratified geological bodies detected by pole-dipole devices.The structure and morphology of laminar formation are detected,the anomalous characteristics of various devices in the sounding method are consistent and data interpretation is similar.But for the low resistance cavern,the anomalous characteristics of the pole-dipole device sounding are different from those of the Schlumberger electrode array,and the data interpretation is different.Through the actual exploration work,the abnormality of the low resistance hole body obtained by the pole-dipole sounding is not fixed at the center of the anomaly,but it should be located near the low resistivity abnormal gradient zone on the pole side.Actual findings and drilling results support this conclusion.