The Correlation Among Dry Density, Grain Size And Magnetic Susceptibility Of Loess

Loess accounts for 9.3% of the world's land area and 6.3% of the Chinese land area as a special kind of sediment.It is studied range from its physical properties simply to mechanical properties and magnetic properties and the relationship between the two different indexes,and the study has never been stopped and develop constantly.As the basic physical property of loess,density affects the other physical properties,mechanical properties and engineering properties.Grain size,another physical property,is regarded as a substitution index of climate measurement which has been relatively mature,and it is of great significance for the identification of material sources,transporting medium and power,sedimentary environments and their changes.The magnetic susceptibility of loess is a basic magnetic property,which is found to be well correlated with the oxygen isotope in the deep sea.Therefore,it is widely used in the sedimentary environment and as a substitute index study for climate change.The density and grain size of loess are closely related to engineering construction.The parameters are determined by the soil teats,whose process is so complex and the period is too long that there is a certain lag behind the progress of construction.Therefore,it is necessary to choose a more convenient substitute index to reflect the density and grain size quickly,and to meet the requirements of rapid engineering construction that become double needs of scientific research and engineering practice and also the requirements of the development of engineering geology and rock magnetism of two fields at the same time.Last,it can lay a foundation for the connection between academic research and engineering application.Aimed at the lag of the measurement of density and particle size,strengthened the research on the relationship between each other,and provided some reference for future related studies,magnetic susceptibility can be expected as a substitute index of density and particle size to make the measurement simply and quickly in the future.The study object of this paper is the loess from Dahuyu Village loess section,and the loess is made as undisturbed samples and remolded samples with different dry density,and then grain size and magnetic susceptibility are determined,the relationship between the three index is discussed,and the conclusions is verified preliminarily.The preliminary understandings are as followed:(1)it can be seen from the experimental data that the magnetic susceptibility(volumeic magnetic susceptibility and frequency magnetic susceptibility)of the red clay is higher than that of the loess,whether the specimens is remolded or undisturbed which is consistent with the previous research.That is,the red clay is deposited in warm and wet period,and the formation of soil is very strong so the fine magnetic minerals are more,which leads to higher magnetic susceptibility.(2)From the relation between two indexes,dry density and median particle size decreases,dry density and volumeic magnetic susceptibility,frequency magnetic susceptibility both increase whether the remolded specimens are red clay or loess.The correlation analysis showed that there is a negative correlation between dry density and median particle size,and a positive correlation between dry density and magnetic susceptibility(including volumeic magnetic susceptibility and frequency magnetic susceptibility).(3)From the experimental data shows that either loess or clay,the curve of dry density and median particle grain is an increase,and the curve of dry density and magnetic susceptibility(volumeic magnetic susceptibility and frequency magnetic susceptibility)is also an increase in the three loess section.The correlation analysis shows that there is a negative correlation between dry density and median particle size,and a positive correlation between dry density and magnetic susceptibility(including volumeic magnetic susceptibility and frequency magnetic susceptibility).Compared and analyzed the data of the validation samples and the original experimental samples,it is found that the two conclusions are basically consistent which reflects the conclusion has a certain rationality.(4)It can be seen that the increase of dry density in loess section is not only accompanied by the reduction of pore size,but also the decrease of particle size through the analysis,and the latter contribution may be more pronounced.(5)From the relationship curve between the magnetic susceptibility and the grain size,the results of the remolded samples and the undisturbed samples are consistent with the previous conclusions,that is,the relationship between magnetic susceptibility and grain size is a negative correlation.(6)The results of the measurement of dry density by the wax-sealing method and 3D laser scanning method show that the data of latter is more stable than the former,and test procedures of the latter are more concise,and the error effect is smaller,so the latter is chose as the research method.