Optimization And Application Of Calculation Formula For Traditional Safety Coefficient Of Pillars

The lead-zinc mining area of a county in Hunan Province(hereinafter referred to as the lead-zinc mining area)has been mined by the open field method.It has been more than 40 years since the formation of a large number of gobs with a wide range and overlapping layers.Based on the area bearing theory,the safety factor calculation method of the pillar is analyzed.The stability of 1365 pillars in the mine is analyzed.It is found that the safety factor of 38.83% of the pillars is less than 1,and should be in a collapsed state.The column can still support the empty area for a certain period of time.This engineering practice does not match the calculation results.This paper deduces the calculation method of pillar safety factor based on Platts theory,and carries out engineering calculation.Finally,through numerical simulation method,the two theoretical calculation methods are compared and verified,and the pillar stress and ore body depth are studied in depth.The relationship between the pillar spans is as follows:(1)Based on laboratory experiments,the rock mechanics parameters of the ore and limestone samples in each mining area of the lead-zinc mine are measured.The empirical calculations are used to calculate the rock mass mechanical parameters of the ore body and the limestone body.(2)Based on the area bearing theory,the stability of 1365 pillars in lead-zinc mine area is analyzed,and compared with the actual situation on site,it is found that the safety factor of the pillar calculated by this method is not in line with the actual situation;The calculation method of the overlying load of the pillar is derived theoretically.The calculation formula of the safety factor of the pillar based on Platts theory is deduced based on the Bieniawski pillar bearing strength formula,and the safety factor calculation is carried out for engineering practice.The comparison between the two theoretical calculation results is made.(3)By establishing a numerical model for the second mining area in the V-mining area of the lead-zinc mining area,and calculating the safety factor of the 16 pillars in the empty area,compared with the results calculated by the two theoretical calculations,the results calculated based on Platts theory More consistent,the calculation results based on the area bearing theory is too small.(4)Through the orthogonal experiment,the sensitivity analysis of the key factors affecting the stability of the pillar is carried out.It can be seen that the order of the factors affecting the safety factor of the pillar in the lead-zinc mine is the depth of the pillar burial,the cross-sectional area of the pillar,and the pillar bearing.The cross-sectional area of the rock pillar and the height of the pillar.(5)By establishing a standard empty zone model with various spans and buried depths,and numerical calculation,the maximum principal stress of the pillar under different conditions is obtained,and the maximum principal stress of the pillar and the buried depth of the pillar are analyzed.The relationship between the spans of the zones.Based on this,the functional relationship between the average stress of the pillar and the buried depth of the pillar and the span of the empty zone is fitted by Matlab software.