Safety analysis of Sormeh underground mine to improve sublevel stoping stability

In underground mines,sublevel stoping is used among a variety of different methods for mining an orebody,which creates large underground openings.In this case,the stability of these openings is affected by a number of factors,including the geometrical characteristics of the rock and mining-induced stresses.In this study,a sensitivity analysis was conducted with the numerical,squat pillar,and Mathews stability methods using the Taguchi technique to properly understand the influence of geometric parameters and stress on stope stability according to Sormeh underground mine data.The results show a full factorial analysis is more reliable since stope stability is a complex process.Furthermore,the numerical results indicate that overburden stress has the most impact on stope stability,followed by stope height.However,the results obtained with Mathews and squat pillar methods show that stope height has the greatest impact,followed by overburden stress and span.It appears that these methods overestimate the impact of stope height.Therefore,it is highly recommended that Mathews and squat pillar methods should not be used in high stope that is divided with several sill pillars.Nonetheless,Mathews method cannot accurately predict how the sill pillar impacts the stope stability.In addition,numerical analysis shows that all geometric parameters affect the roof safety factor,whereas the sill pillar has no significant influence on the safety factor of the hanging wall,which is primarily determined by the stope height–span ratio.

Ergonomic assessment of drivers in MF285 and MF399 tractors during clutching using algometer

Tractor as one of the most widely used agricultural machinery should be considered from different aspects.The frequent application of clutch and brake pedals and also the steering wheel within farms,along with the unfavorable working conditions,cause negative effects on the occupational health of the tractor drivers.Thus,in this research,the imposed forces on three engaged muscles including:Gastrocnemius,Trapezius and Quadrate’s lumborum of the tractor drivers during clutching have been studied.In this regard,algometer device was used to determine the applied forces on selective muscles of drivers during clutching of MF285 and MF399 tractors.The experiments were performed employing sample of 30 drivers and were conducted on two Iranian frequently used tractors including:MF285 and MF399 models.The results showed that the clutching forces for MF285 and MF399 tractors were 340 N and 290 N,respectively.The knee angle of the drivers of the two tractors was statistically different at the one percent level of significance.The reduction of pain threshold after 30 and 60 s clutching and also 60 s rest after clutching in MF285 tractor,for all three muscles,were more than those of MF399 tractor.The impact of clutching on the average decreases of pain threshold,for all drivers and all clutching periods,during and after clutching,in the Quadratus lumborum muscle was more than the other two muscles,in both tractors.In order to reduce the clutching force for MF285 tractor some modifications is suggested.In this regard the force transfer joint between the pedal and the clutch release linkage may be replaced with one made of cast iron.