Research On Optimization Of Rock Mass Quality Classification Method In Q System

Lead-zinc ore reserves in Huayuan County of Hunan Province are abundant and have been extracted using the chamber-column method,leaving a large number of untreated contiguous goafs.The accumulated goaf volume exceeds 50 million cubic meters.Through the statistical analysis of the results of the survey of the structure parameters of the goafs in a number of mining areas,it was found that a large number of goaf roof spans and exposed areas seriously exceeded thedesign parameters,and the pillars were not standardized.Although there were also partial falling and pillars.cracking deformation and other damage phenomena,but did not produce a large area collapse as a whole.So,the analysis of the stability of the goaf using traditional rock classification and theoretical methods does not meet the actual situation of the field project.In this paper,through the comparison between the measured parameters of the goaf site and the existing rock mass grading methods,the following research work has been carried out based on how to accurately calculate the limit span and exposed area of the goaf:(1)Collecting and compiling field data,indoor rock mechanics experiments were conducted on the main rock body limestone and dolomite,and related rock mechanics parameters were obtained.According to the results of engineering geological survey,rock mass grading was performed using RQD,RMR,and Barton Q system classifications.Based on Barton's extreme span analysis method and Mathews graphical method,the allowable span and exposed area of the roof in the goaf area were calculated.(2)Through statistics on the sample parameters of 1236 goafs in Huayuan lead-zinc mine,and the calculation results of the goaf structural parameters based on the Q system rock mass classification method,due to the statistical limitations of the statistical methods of the classification method,resulting in large-scale goaf The accuracy of the district's judgments has been reduced,and phenomena that do not meet the actual conditions on the site have occurred.(3)The goaf model with different hydraulic radii was built in a hierarchical nesting manner.Using software such as Midas GTS NX,Flac3 D,etc.,175 experimental samples consisting of three factors of different mining depths,different hydraulic radii,and different lithologic conditions were conducted.Finite element numerical simulation analysis,through the analysis of stress,displacement and surrounding rock unit destruction rate,obtained the relationship between different influencing factors and the stability of surrounding rock in the goaf.(4)On the basis of numerical simulation calculations,@Risk software was used to analyze the failure rate of surrounding rock units,and the difference values of the failure probability data were fitted to obtain the new Mathews stability-transition,transition-valley boundary;the Mathews stability for the fitting-Inverse calculation of the transition curve,corrected the formula for calculating the limit span of the Q system.The calculated mathews stability map and the Q-system limit span calculation method are more close to the actual situation of the project,and the evaluation results of the stability of the goaf sample are more accurate.The research results have certain guiding significance for improving the rock mass classification method.