Study On Electrical Conduction Characteristic Of Rock-soil Masses In Mines And Its Application To Engineering

Stability of surround rock of a chamber and the analysis of the temperature field of frozen wall while artificial freezing method of shaft sinking technology being adopted in deep alluvium are two key problems of mine excavations in deep mining.This paper studied resistivity characteristics of major rocks and soils in Huaibei and Huainan Coalfield by sampling soils from alluvium and sampling rocks from stratum of coal measures in Huaibei and Huainan Coalfield.Furthermore,data acquisition and data processing of detecting the temperature field of frozen wall were put forward in combination with the technology characteristics of shaft sinking,and technology of detecting strata released zone based on resistivity method was studied in combination with the technology characteristics of mine roadway construction.Research results had been applied to measuring and testing the temperature field of frozen wall in freezing sinking project and the surround rock strata released zone of roadway,and achieved good results.The main research works and results are as follows:(1) Empiricism in corresponding depth with record points in resistivity inversion section of the high density resistivity method limits its application to engineering.According to the basic theory of the point electric field,combined with the characteristics of the latest data acquisition technology of resistivity exploration,the parallel electrical prospecting and cross-hole seismic exploration,data acquisition method of simulating-seismic pole-pole cross-hole DC resistivity CT technology was advanced, and data-processing program was prepared.The data acquisition and processing methods were provided for testing the temperature field of frozen wall by resistivity method.(2) By means of sampling soils in main soils stratums of the alluvium in Zhuji Mine in Huainan Coalfield,first of all,the devices currently used in soil conductivity testing were combined with the technology of high-density resistivity method in the laboratory tests to explore the effect of particle size distribution,water content,density(or compactness) upon the electrical resistivity of soil masses in the normal temperature, and the regression equations of the resistivity,water content and density of different soils were fitted;Secondly,testing methods of resistivity of frozen soil were studied, and according to the features of water content,density of different soil stratums, geotemperature and the design of the temperature of frozen salty water and average temperature of frozen wall in project of shaft sunk by freezing,the relationship between resistivity and temperature of soil under certain water content and density was studied.The temperature-resistivity(t-ρ) regression equations of different soil masses were fitted with much high correlational coefficient,serving as the bases for detecting temperature field of frozen wall by resistivity method.(3) By means of sampling rocks in main rock stratums of coal beating formation in Huaibei and Huainan Coalfield,the relationship between resistivity and stress(or strain) of rock was studied.The coupling material of good performance and high availability between rock and electrode,over-saturated clay was found,and stress-resistivity(σ-ρ) regression equations of different rock masses were fitted with much high correlational coefficient,serving as the bases for detecting stability of surround rock of a chamber by resistivity method.(4) On the basis of research results in the pole-pole cross-hole DC resistivity CT technology,construction technology,data acquisition method and data processing method in testing the temperature field of the frozen wall by resistivity were brought forward.And the technology was used in engineering practice,and has achieved relatively good results.(5) Stability of surround rock of a chamber is an important factor to safety and efficient production of a mine.In order to maintain stability of a chamber and ensure a safe and normal application of the chamber,an economic and rational support pattern must be adopted.Due to the importance of the size and the three-dimensional distribution law in selecting support pattern of the chambers,and with exploration principle of high density resistivity method and construction feature of excavation and support for the chambers,the paper provided the measurement and test technology of surround rock strata released zone with drilling machine for the borehole drilling,anchorage agent for collar sealing,pressurized equipment for grouting cement slurry and high density resistivity method for the data collection.In combination with the regression equation of relationship between resistivity and stress by experiment,the paper studied the relation between surround rock deformation degree and electric conductivity after the excavation and support of the chamber,analyzed the development of surround rock strata released zone of roadway.The technology has been successfully applied to measuring and testing surround rock strata released zones of roadways in mines in Huaibei and Huainan Coalfield.