Experimental Study On Point Load Strength And Failure Factors Of Rocks

This paper took the common coarse sand,fine sandstone,siltstone,sandstone,sand mudstone and carbonaceous mudstone of coal seam roof and floor as the research object, used theoretical analysis and experiments research, and researched point load strength and failure factors of rocks.First, a series of steps and methods of portable point loading instrument was introduced. Structure of instrument,system and schematic were described. The main interface of software was given via the programming language.Next, failure factors of point load strength were analyzed. The shape and size effect of irregular rocks of six kinds of lithology were revised. Meanwhile, modifier formulas of the shape and size effect of irregular rocks were obtained.Finally, point load strength of irregular rocks of six kinds of lithology were statistically analyzed. It can be concluded that the histograms of coarse sand、sandstone and sand mudstone were normal state, while the histograms of fine sandstone,siltstone and carbonaceous mudstone were abnormal state of partial type, shuangfeng type and reduction gear, respectively. Strength values of six kinds of lithology were basically satisfied the normal distribution law. To a certain extent, the rationality of using the irregular rocks to precede point load tests was verified.In conclusion, there are certain relationships between point load strength of irregular rocks and failure load area,aspect ratio and loading point space. Point load strength of irregular rocks and failure load area is a linear relationship. The different failure load area is basically not influence on size and shape effect of point load test. Processing the way of irregular specimens was given. The aspect ratio is always from0.8to1.3and the loading point space is from30to50mm.