Experimental Study On Microstructure Of Malan Loess In Yan'an

The physical indexes of Malan loess at different depth were obtained through field survey,field sampling and indoor geotechnical tests.Samples used to observe and analyze loess structure were got using pore-filling method.The microstructure of Malan loess were discussed depend on scanning electron microscope and data image processing system.Qualitative and quantitative analysis were carried out.On the qualitative analysis of the microstructure of loess,a large number of literature studies were carried out.According to the structural characteristics of Malan loess in Yan'an new disrict,the grain morphology,the contact form and arrangement of particles,the size classification of pore,the genetic classification of pore,the classification of pore connectivity,the form of the cement and the type of loess cement of were discusses,as well as these characteristics' change with depth.On quantitative research on Malan loess pore,the parameters of the Malan loess were obtained using digital image analysis system.And,pore area rate,the area and number of different pores,pore size distribution,pore shape distribution,and pore morphology characteristics were analyzed,as well as these characteristics' change with depth.The qualitative and quantitative analyze is of Malan loess in Yan'an new district shows that most loess particles were dominated by angular particles,semi-angular particles,semi-circular particles,rounded particles and particles with clay coating.Five samples in this study were considered as porous soil,both according to void ratio and pore area ratio.In addition,scaffold pores in Malan loess were large pores,a few are medium pores.Most mosaic pores are mesopores.The number of pores within the loess cement is very large.Most of them have a stable structure,small volume.A few of them are small pore,with different shapes.Most intragranular pores are small pores,few are micro pores.With the increase of depth,the number of unstable pores,like many large and meso scaffold pores were squeezed into smaller pores due to overlying soil pressure.So the area of scaffold pores significantly reduced to 62%,while the area of mosaic pores and intragranular pores increased with depth increasingly.Simultaneously,the connectivity of pore decreased as well.The number of micro pores,small pores,meso pores and macro pores decreased significantly.The difference in number mainly due to the significant reduction of round pores,indicating that round pores tend to be small.In terms of area,elongated and irregular pore had predominance in the area of micro pores,small pores,meso pores and macro pores.The cumulative frequency curve of elongation accorded with the S-shaped curve,and its frequency obeyed the Gaussian distribution.It should be mentioned that the pore surface in Malan loess tended to be elongated.And,contact cementation in Malan loess was relatively common,while breccia cementation and basal cementation were comparatively uncommon to be seen.