Discussion On Regularity Of Microstructure Of Malan Loess In Different Latitude

As we all know,the macroscopic mechanical properties of soil are controlled by its microstructure.To find out the influence mechanism of the loess microstructure on its macroscopic mechanical properties,the correlation between the microstructure and mechanical properties must be studied firstly,The microstructure images of the loess were obtained by electron microscopy and the microstructures were obtained using IPP After extracting the parameters,the microstructure characteristics of the Malan loess in different latitudes were studied from both qualitative and quantitative aspects.Finally,the correlation between the microstructure parameters and mechanical parameters of the Malan loess was discussed.The following conclusions are obtained:The microstructure characteristics of Malan loess showed regular changes with decreasing latitude.The shape of the particles transitions from rhomboid and semi-rhombic to rounded and semi-rounded;the arrangement of soil particles gradually changes from the arrangement of scaffolds to mosaic arrangement and dispersion;the contact between the particles is from direct point contact and direct surface cementation Gradually transformed into indirect point cementation and indirect surface cementation;the proportion of large pores in the soil gradually decreased,and the proportion of small and medium micropores gradually increased;the pore shape in the soil gradually changed from mainly polygonal large pores and bagged pores to It is mainly composed of triangular pores and circular pores;the connectivity of pores in soil gradually transitions from interpenetrating pores and connected pores to intergranular pores and intragranular pores in low latitudes;the attachment method of cement in soil is composed of patchy cement,Film-like cement gradually transitions to interstitial cement and aggregate cement;the cement type of loess gradually changes from patchy cement,contact cement to interstitial cement,semi-aggregate cement and agglomerate cement;microstructure type mainly consists of Stent arrangement direct point contact structure,stent arrangement direct surface contact structure,stent arrangement spot-shaped cement structure,stent arrangement Contact cement structure gradual transition to plaque cemented mosaic arrangement structure,mosaic arrangement structure cemented surface,like cement dispersing aggregate distribution half structure,aggregate-like dispersion profile bonding structure.Based on the changes in latitude,three types of microstructure models,namely scaffolds,mosaics,and dispersed distributions,were established,and it was believed that the change in cement content was the key to the coexistence of multiple microstructures in the soil.Quantitative results of loess microstructures indicate that as latitude decreases,the pore area ratio gradually decreases,the number and area ratio of large pores gradually decrease,and the number and area ratio of small and medium pores gradually increase;the number and area ratio of circular pores gradually increase,irregular pores The number and area ratio of slender pores and slender pores gradually decrease,and small pores are mostly circular pores.The mesopores are mainly irregular pores and elongated pores;the circularity parameter of pores in the soil body gradually increases with latitude;The elongation 0.2-0.8 part becomes more uniform in number and area,and the pores are generally elongated,which also shows that the shape difference between the pores gradually decreases;and through the fractal dimension parameter,it can be seen that the regularity of the pore profile increases.The correlation analysis results of the microstructure parameters and mechanical parameters of the loess show that the microstructure parameters such as particle grading,average particle size and particle roundness of the soil are closely related to the shear strength parameters of the loess.The pore area ratio and pore shape of the soil The microstructure parameters are closely related to the compression coefficient of the soil.