Study On Damage Characteristics Of Sandstone After Peak Based On CT Image

Based on the different confining pressures of sandstone loading tests,the articleobtains the CT images of sandstone after the sandstone peaks.Then the damagecharacteristics of the sandstone after the peak were studied through the CT image.Currently,the CT technology for studying the damage characteristics of the sandstoneafter the peak provides a very effective technical means.But the CT images of the rockafter the peak were not fully utilized in the CT image analysis.Based on digital imageprocessing technology,the paper reduces the noise of the sandstone CT images afterpeak,does the pseudo-color image enhancement and edge detection to give a clearpicture of internal damage of the sandstone after peaks.And then the paper analyzed thedistribution of internal damage cranny in the sandstone after peaks.Based on the research of some experts,this paper analyzed the mechanicalparameters of the sandstone after the peak.At the same time,regarding the damagemechanics and micromechanics as the theoretical basis,the paper established an idealmathematical damage model of sandstone in post-peak,then the paper defined thedamage.The paper obtained the CT number and variance through the CT images ofsandstone in post-peaks,and derived the relationship between damage variable of therock in post-peak and CT number from the CT number definition.The paper obtainedthe damage variables in different confining pressure.From the beginning to the limit ofthe pressure,the volume of the specimen is reducing,so that the average density of thesandstone after the peak actually increases.Then the average number of such CT scanimages will also increase,and this actually will be offset the reduced number of CTwhich due to micro-cracks,and so the damage is not great.But the specimen damagesseriously,such as cracks widens,the volume of the sandstone increases,the densitydecreases after the peak.So that all these matters make the average number of CT scanimages begin to become smaller.Relatively to the average CT number of initial CT scanimages,the CT number decreasing amplitude is large.But the degree of damage increases.This fully shows that after the peak the specimen has been completely broken,loses their ability to supporting.So study on the extent of damage and damage evolutionprocess can be quantified.In the end,based on the fractal theory and fractal model,the paper obtained thefractal dimension of the sandstone after peaks.And in accordance with the relevantfractal dimension,the paper describes the distribution of the cracks after thepeak.According to the self-definition of rock damage theory,the paper establishes therelationship between the damage and the fractal dimension,and uses the fractaldimension to quantitatively describe the sandstone damage after the peak.It found that,with the load increasing,the fracture distribution fractal dimension of the sandstone afterpeak is growing.New cracks gradually produce and the original fissures become largerinside the sandstone,and so the number of fractures in the statistics region is more andmore.Finally the study revealed the fracture distribution,fractal distribution and damageevolution of the sandstone after peak,and it is consistent with previous studies.