Study On Microstructure Extraction,Microstructure Quantitative Analysis And Mechanical Properties Of Sandy Soil In Compression Processes

Land subsidence is one of the most common geological disasters in China.In some areas,the sand layer becomes the main settlement layer of land subsidence.Therefore,studying the mechanism of macro and micro deformation of sand under compression is of great significance to understanding the deformation and failure mechanism and predicting the settlement of sandy soil layer.By designing a micro structure extraction technology under confined compression of sand,this paper realizes the confined compression test of sand,and effectively realizes the consolidation and capture of its microstructure.On this basis,the PCAS software is used to make a quantitative analysis of the extracted microstructures.Three kinds of sand samples with different particle size,gradation and particle shape are studied in this paper,and the following results are obtained:(1)In order to fix,extract and quantify the microstructure of sand soil during compression,this paper designs an extraction technology of microstructure of sand soil in the compression process.It is mainly composed of two parts,apparatus for blue epoxy injection and the improved sand collecting box.In confined compression tests of sand soil,a step motor is used to drive blue epoxy into the compacted sand soil sample,via the preset hose and the bottom side of permeable stone.Thin sections can be made when the epoxy is consolidated,and the microstructure images can be captured by optical microscope.By using the technology,the microstructure of sand soil can be consolidated and captured during compressive processes.(2)Based on confined compression test data,the effects of particle size,gradation and particle shape on compressibility and creep of sand were analyzed.When the particle size is relatively simple,the particle size is positively correlated with the compress of sand and the creep.When the particle size is wide and has certain gradation,the better sand sample with a better gradation has greater compressibility and creep.and the compress of the particle size and grade is mutually influenced and restricted.On the whole,the sand sample with better gradation can get higher compactness,and as the particle size increases,the larger particle size,the more easily broken,and gradually become the main factor to control the compressibility of the sand.Among the three kinds of factors,the particle shape has the greatest influence on the compressibility and creep of the sand.The spherical sand with different particle size is very close to the compressibility and creep,and the value is obviously smaller than that of the non spherical sand sample.Different gradation spherical sand shows similar properties.(3)The microstructure parameters of sand samples were analyzed.When the sand particle size is relatively simple,the sand sample with larger average particle diameter is more easily broken,so the smaller the average shape factor,the greater the compression and creep variables.The average shape coefficient becomes the main controlling factor of sand creep in the sand samples with poor gradation and the particle size in a certain range.The average shape coefficient and the creep variable have good correlation.The larger the average shape coefficient,the smaller the creep variable.Based on the microscopic parameters of particles,the particle breakage rate is proposed.When the sand particle size is relatively simple,this parameter can reflect the degree of sand particle breakage to a certain extent.