Application Of High-density Resistivity Method In Concealed Karst Exploration

China is the country with the widest distribution of karst landforms.When carrying out basic engineering construction,it is bound to cross the karst area.When there is concealed karst,it is easy to cause accidents.Therefore,it is necessary to survey the distribution and development of karst in the whole working area.Although drilling can explore the karst in the working area,the vertical and horizontal development of the karst can not be made clear.Therefore,a reasonable and accurate exploration method should be used to determine the underground concealed karst in karst areas,so as to provide relevant guidance for the engineering construction in karst areas.At present,as a part of electrical exploration,highdensity resistivity method has been a mature geophysical exploration method.Due to its advantages of automatic data collection,diversified measurement modes and high production efficiency,it has been widely used in concealed karst exploration in karst areas.Firstly,this paper summarizes the engineering geological characteristics,the development conditions and laws of karst,the morphology and engineering classification of karst landform,the engineering geological characteristics of carbonate rock and the geophysical characteristics of common rock and soil media in karst area by looking up and reading the previous research results.Then,based on the basic principle of THE DC resistivity method,the various device types of the high-density electrical method and their respective characteristics and device coefficients are analyzed and summarized,and the finite-difference method forward simulation and least square inversion simulation of the high-density electrical method are studied according to the previous data.Based on the low-resistivity karst cave model established and two-dimensional forward inversion simulation by high-density electric method,the resistivity response characteristics of six devices of high-density electric method are analyzed and studied,from which the best device for detecting concealed karst by high-density electric method is selected.By comparing the results of numerical simulation of the six device,can be concluded that: in the detection of similar low resistance of abnormal body,wenner-Shi Lun bell device and tertiary device detection effect,is better than wenner alpha device,wenner beta device,wenner gamma device and dipole device,and comprehensive consideration to factors such as resolution and signal strength and depth of exploration,tertiary device is the best of the detection of concealed karst detection method.Based on the establishment of a variety of concealed karst combination models,the resistivity response characteristics of the three-stage device of the high density electric method were analyzed and studied by two-dimensional forward inversion simulation.Through the analysis of forward modeling results,it can be concluded that,when the high-density electric method is used to detect hidden karst,the abnormal resolution in the horizontal direction detected by the three-stage device is higher than that in the vertical direction detected by the method.The abnormal resolution cannot well display the shape of the abnormal body,but the display of the abnormal position and width is very accurate.Through the analysis of the inversion results,it can be concluded that the high-density electric method is very sensitive in detecting the hidden karst,and can well display the shape,position and size of the abnormal body,with good detection effect,and can be well applied to detecting the hidden karst in the karst area.Finally,an engineering example,in the guangxi xinfa aluminum electric co.,LTD.,tailings field of engineering,using the high density resistivity method to detect hidden karst of the test zone,to the raw data collected seismic data inversion processing,combined with the measured apparent resistivity profile and inversion of apparent resistivity section to the scene of the abnormal reasons for analysis and interpretation,marking out the measurement zone of the karst development area.Combined with the disclosure of borehole,the validity of high density electric method in detecting hidden karst is verified.