高密度电法探测层状地质体正反演数值模拟

Forward and inverse numerical simulation of high density electrical exploration of stratified geological bodies

为了确定滑坡等层状地质体在测深工作中的电性特征和展布规律,采用高密度电法温纳装置进行数值模拟,通过分别建立5 m厚的高阻、低阻两种层状地质体在10 m、15 m、20 m、25 m、30 m、35 m不同埋深下的数值模型,经过正、反演计算后与数值模型进行对比,分析反演后高阻模型探测深度为AB/7,低阻模型探测深度为AB/8;随着异常地质体埋深逐渐增大,异常影响范围会逐渐变宽,高阻地层反演后的极大值较模型逐渐减小,低阻地层反演后的极小值较模型逐渐增大。通过低电阻背景下的工程实例,确定探测深度为AB/6,并有效确定了滑坡体的滑动面位置,经钻探验证后结果可靠,滑坡体的平均厚度为7.4 m左右。研究结果表明,温纳装置的有效探测深度在AB/8~AB/6左右,布设电极距时不宜大于异常地层的厚度,剖面线长度应尽量足够的长,以保证足够的探测深度,会使勘探结果更满足实际情况。

In order to determine the electrical characteristics and distribution rules of layered geological bodies such as landslides in sounding work,a high-density electrical Wenner device is used for numerical simulation.Numerical models of two kinds of layered geological bodies with high and low resistivity of 5 m thickness are established respectively under different burial depths of 10 m,15 m,20 m,25 m,30 m and 35 m.After forward and inverse calculation,the detection depth of the high resistance model is AB/7,and the detection depth of the low resistance model is AB/8.With the increasing of the buried depth of the abnormal geological body,the influence range of the anomaly will gradually widen.The maximum value of the inversion of the high resistivity stratum will gradually decrease compared with the model,and the minimum value of the inversion of the low resistivity stratum will gradually increase.Through the engineering example under the background of low resistance,the detection depth is determined to be AB/6,and the position of the slide surface is effectively determined.After drilling verification,the results are reliable,and the average thickness of the slide is about 7.4 m.The results show that the effective detection depth of Wenner device is about AB/8-AB/6,the electrode spacing should not be greater than the thickness of abnormal strata,and the section line length should be as long as possible to ensure sufficient detection depth,which will make the exploration results more meet the actual situation.