Study On Coal-rock Interface Identification Method Under The Mine Based On Dielectric Properties

Unmaned working face mining technology is an effective and safe wayof exploitation,which can effectively reduce the accidents and ensure the safe mining.In order to achieve this goal,the intelligent identification of coal rock interface should be solved at first which is the key problem restricting the intelligent coal mining equipment.Coal-rock interface refers to the interface betweencoal layer and rock layer.The mining machine should cut along with the coal rock interface and adjust the height of cutting drum immediately to avoid over/under cutting when the coal rock interface changes.The topic has been a hot research at home and abroad.Though many scholars have put forward many rep resentative research methds,a final solution has not been formed.At present,the following problems exist:1)Lack of coal-rock identification method suitable for different geology.Due to the changeable and complicated coal seam conditions in China,the coal and rock types of different coal mines vary widely.Even in the same coal mine,the interface between coal and rock is irregular,and faults and gangue may also occur in the coal mined.2)Lack of the study of the characteristics of the coal rock itself or similar methods.The properties of different types of coal and rock will change due to changes in water,compactness,granularity,and the types of minerals they contain.We need to study the characteristics of coal and rock,and discuss the method of coal-rock interface identification with better applicability and reliability.Based on the above considerations and analysis,we conducted a study on the interface identification of coal-rock:First of all,we study the variation trend of the coal-rock dielectric property when the physical properties,the types and content of inorganic minerals change.Secondly,according to the different dielectric characteristics of coal-rock,a coal content estimation model is proposed based on Bruggeman’s theory.Finally,using Comsol Mutiphysics simulation software,an improved image reconstruction algorithm is proposed,and a visual identification model of coal rock interface is proposed.Through physical test,theoretical verification and simulation,it can be obtained:(1)In this test,within 10KHz~30MHz frequency,the physical properties(including water content,compactness,and particle size)of bituminous coal,anthracite and rock were changed,or the content of inorganic minerals(including kaolinite,calcite,q uartz and brown iron)were changed,the dielectric constant of coal was always different.(2)Based on the Bruggeman theory,we proposed the coal content estimation model.In the detection range of 10 KHz~30 MHz,the relative error of the theoretical coal content value and the actual value is smaller,with an average of less than 4.10%.In the high frequency range,the accuracy of theoretical coal content is relatively high,and within 500 KHz~30 MHz,the average can be controlled at about 2.6%.(3)Using the Comsol Mutiphysics simulation software and the improved image reconstruction algorithm,we propose a visual identification model of coal and rock interface.It can effectively identify the stratification of coal and rock,and it can also identify the gangue in the coal seam.This method can be applied to coal mines with complicated geological conditions.In general,the dielectric property based identification method of coal and rock has the characteristics of simplicity and wide applicability,which provides a new identification method for the underground unmanned mining.