| Karst is a very complex and undesirable geological body,its existence is hidden and uncertain,and it is often difficult to find and find out.For civil engineering,karst development is often one of the unfavorable factors,and karst areas are also frequent areas of geological disaster accidents.At this stage,the high-density resistivity method is widely used in karst exploration projects in Southwest China.However,due to the complex topography and geomorphology of this area,the uneven thickness of the Quaternary overburden,and irregular karst development locations,high density The difficulty of electrical exploration has increased sharply,and its inversion results are complex and changeable.In the actual exploration process,the different choices of various parameters will also have a greater impact on the resolution of detection and mapping.The effect of the detection resolution is still needs improvement.This paper comprehensively considers the device type,karst type,scale effect,electrode arrangement influence,interference influence and inversion parameters and other factors,carries out the high-density electrical method forward and inversion numerical simulation study,and combines the karst detection engineering examples to carry out the application effect analysis.The factors affecting the reliability and accuracy of detecting various types of karsts by the high-density electrical method are summarized,providing effective reference suggestions for future high-resolution detection in karst areas.The main research results are as follows:(1)The Wenner ? device has relatively better resolution for cave inversion under low-resistance caves,shallow horizontal corrosion cracks,or high random noise;the Wenner ? device has high resolution for semi-filled caves,unfilled caves,and deep buried caves.The inversion resolution is relatively better when the barrier cave or overburden is thick;the Wenner ? device has relatively better resolution when detecting fully-filled karst caves;the dipole-dipole device has a relatively better resolution for shallow or fractured karst detection The highest,but its detection depth is relatively shallow;although the pole-pole device has a large detection depth range,its overall accuracy will be slightly lower than other devices;the overall performance of the dipole-pole device is relatively good and stable.(2)For fully-filled caves,the lower the resistivity of anomalous bodies of the same scale,the larger the volume effect after the inversion of the six devices,and the smaller the scale,the more obvious;for semi-filled caves,only the Wenner ? device is The semi-filled morphology of the body has better resolution;for unfilled caves,the higher the resistivity of the anomalous body is of the same scale,the higher the resolution of the inversion of the six devices,and the smaller the volume effect of the anomaly;For fissures,the resolution of the six devices for low-resistance inversion is relatively high;for the solution groove,the dipole-dipole and pole-dipole devices have relatively good inversion resolution for their morphology.The resolution of using six devices to detect caves and trenches is higher than that of corrosion cracks;the resolution of detecting low-resistance anomalies is higher than that of high-resistance anomalies.When the resistivity of karst anomaly is too low or too high,it is easier to form false anomalies around it.(3)The increase in the thickness of the covering layer or the increase in the buried depth of anomalous bodies has a greater impact on the inversion of high-resistance anomalies than on low-resistance.(4)Three-dimensional detection has better resolution for the inversion of the shape and scale of anomalous objects,while two-dimensional detection has better resolution in the depth range.In the two-dimensional detection method,as the electrode distance increases,the resolution of low-resistance anomalies decreases more than that of highresistance anomalies,especially for deep low-resistance anomalies.In actual engineering,the cost performance is higher when the electrode distance of 3-5 meters is selected.(5)The influence of random noise on high-resistance karst is higher than that of low-resistance,the influence on dissolution fissures is higher than that on caves,and the influence on deep layers is higher than that on shallow layers.Part of the apparent resistivity caused by the power failure of the electrode appears to be a maximum value,which has a greater impact on the inversion of the entire profile.Although the correct position of the abnormal body can be restored by removing the abnormal value,its resolution will be reduced,and the electrode will be powered off.The more,the lower the resolution.(6)When the random noise is small,a relatively small damping coefficient is set,and the resolution of the inversion is relatively high;on the contrary,a relatively large damping coefficient should be set.When the damping coefficient changes,the inversion resolution of the low-resistance anomaly is more stable than that of the high-resistance;the inversion resolution of the shallow anomaly is more stable than that of the deep.Using the lowest damping coefficient or Rubst constraint may reduce the overall resolution,but it is helpful to distinguish the morphological scale and depth range of anomalous objects.Comprehensive numerical simulation research results,applied to high-density electrical method to detect karst engineering examples,the interpretation results are more consistent with the drilling verification and existing geological data,indicating that the numerical simulation research results of the thesis and the summary of the exploration parameters and inversion parameters selection The method has good practical feasibility and provides effective reference suggestions for high-resolution exploration in karst areas in the future. |
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