Experimental Research On Structure And Compression Deformation Characteristics Of Malan Loess

Malan loess is a natural foundation and filling material for engineering construction in Loess area.Its compressive deformation directly affects the stability and safety of infrastructure such as buildings and highways,and loess distributes widely in China.Because of its different material composition and sedimentary environment,the physical and mechanical properties of Malan loess in different areas are obviously different.Therefore,Malan loess knot is studied.The influence of structure and particle composition on compressive properties is of great significance.The confined compression tests of Malan loess in situ and remolded samples and Yan'an Malan loess samples with different moisture content and dry density were carried out by using high pressure consolidation apparatus.The microstructure of Malan loess in different areas and the micro-morphology of loess samples after compression deformation under various working conditions were observed by scanning electron microscopy.The physical indexes and compressibility indexes of Malan loess were established.Functional relations between scales.The structural parameters of Malan loess under various pressures are calculated through lateral confined compression tests and according to the definition of structural parameters.The results show that the structural parameters of Malan loess show two types of "strengthening" and "weakening" with the increase of pressure.Microscopic tests show that the basic structural units of Malan loess,the contact,arrangement and cementation of particles with their grains are found.Particle composition and clay content are highly correlated.Compressibility of Malan loess with different grain fabrics is different,which is mainly caused by different clay content.With the increase of clay content,the compression index and compressibility of Malan loess increase;the compression modulus of loess decreases with the increase of clay content,and decreases sharply at about 20% of clay content;and the deformation of loess sample increases relatively with the increase of clay content.Large deformation takes a relatively long time to reach stability.The skeleton void ratio of Malan loess with different clay content is expressed by the void ratio between silts.Under the same pressure,the skeleton void ratio increases with the increase of clay content,while the larger the pressure,the smaller the influence of clay content on the skeleton void ratio.Gregory proposed logarithmic function model to fit e-logp compression curves of Malan loess with different dry density,moisture content and different regions.Compression index and structural yield pressure were estimated according to fitting parameters,and the relationship between compressibility index and basic physical index of Malan loess was analyzed.The results show that the compressibility index of Malan loess is linearly correlated with water content,the compressibility index increases with the increase of water content,and the yield pressure decreases with the increase of water content;the compressibility index of Malan loess is quadratically correlated with dry density,and the compressibility index decreases with the increase of dry density,and the change rate decreases gradually;the yield pressure increases with the increase of dry density,and increases with the increase of dry density.The rate also increases gradually.Compression index is quadratic correlated with each index.Compression index increases with the increase of clay content,inhomogeneity coefficient and liquid-plastic limit,and decreases with the increase of median particle size.Yield pressure is linear correlated with each physical index.Compression resistance of Malan loess decreases with the increase of clay content,inhomogeneity coefficient and liquid-plastic limit,and increases with the increase of median particle size.Microscopic photographs of samples after compression show that different moisture content and dry density make the compactness of loess aggregates change with different degree of compactness.The difference of compressibility of Malan loess in different areas is mainly due to the difference of clay content,its basic structural units are different,and the location of clay particles after compression damage is also different.