Study On Anisotropy Of Interfacial Natural Loess Based On Quantitative Description Of Microstructure

Loess is widely distributed in western China.It is a special soil with layered distribution and strong anisotropy.With the gradual promotion of the "one belt and one road" strategy,the continuous strengthening of engineering activities leads to the frequent occurrence of geological disasters.However,the basic theoretical research on the anisotropy of the loess stratum is very limited,so it becomes particularly urgent to explore the variation rules of the anisotropy of the loess stratum and its causes.This paper containing natural loess interface in Yanan area as the research object,focusing on its hydraulic and mechanical characteristics of research,combining macroscopic mechanical index and micro structure parameters,from the perspective of microstructure of the interface of natural loess explains the mechanics of anisotropic characteristics,study the content of this article mainly from the following four aspects:(1)According to the previous field investigation,the loess section in Yanan new town has the characteristics of large thickness and complete stratigraphic sequence.By referring to relevant literature and combining expert judgment,we determined that the research target was natural loess with interface(Wucheng loess(Q1)),in which the upper layer was S18 and the lower layer was L19.The basic physical property parameters of interfacial natural loess were tested,and the microstructure of fracture surfaces in different directions was observed by scanning electron microscopy(SEM).(2)Transient dehumidification and moisture absorption system(TRIM)was used to study the unsaturated soil water characteristics of interfacial natural loess from aspects of matric suction,stress absorption and unsaturated permeability.At the same time,the anisotropy of saturated permeability of interfacial natural loess was studied based on saturated permeability test.(3)The change rule of mechanical anisotropy of interfacial natural loess was studied by conventional triaxial test(UU),and the change rule of stress-strain curve,peak strength ratio,volume strain and shear strength index was analyzed by controlling water content and confining pressure as variables.(4)Through PCAS software to extract the soil microstructure parameters of different direction ESEM images from particle and pore shape and arrangement of the elements characteristics of containing interface microstructure anisotropy of natural loess is analyzed,and the micro structure parameters and the combination of shear strength parameters,from the perspective of microstructure against shear strength parameters are explained.