Characteristics of Microstructural Changes of Malan Loess in Yan’an Area during Creep Test

Abstract

The shortage of land resources on the Loess Plateau has long been a thorny problem. Many high-fill projects are carried out, accompanied by a series of geological hazards, which threaten the ecological environment and personal safety. The creep characteristics of loess are an essential part of loess landslide research. The microstructural changes are closely related to creep behavior. By conducting triaxial creep experiments on Malan loess from the Yan’an area in China, scanning electron microscope (SEM) experiments on loess in different creep stages were carried out. Using qualitative and quantitative analyses of the microstructural characteristics of intact loess and remodeled loess during creep, the microstructural parameters were compared, and finally, the microscopic mechanisms during creep were analyzed. The qualitative analysis of remodeled loess during creep returned significantly higher results than it did for intact loess. During the creep process, among the microstructural parameters of loess change, the change in pore and particle size and shape were the most obvious, while the complexity of other microstructural parameters and orientation changed little. During the creep process of loess, the soil skeleton changed continuously, but the loess microstructure featured different changes at different levels of deviator stress.

The Influence of Overburden Stress and Molding Water Content on the Microstructure of Remolded Loess

“…Moreover, as overburd pressure surpasses yield stress, the displacement of skeletal particles in remold loess triggers the disintegration and recombination of aggregates, leading to a p gressive reduction in bracket pores. When the overburden stress exceeds the yield stress, the framework particles of the remolded loess undergo movements such as rotation, displacement, sliding, and fragmentation, causing the transition from point-to-point or point-to-face contacts to face-to-face contacts [24]. Under the influence of the applied stress, weakly bonded skeleton granules are separated, and clay aggregates and clusters are fragmented and re-aggregated into new clusters.…”

“…During the drying process, the roughness of pore surfaces increases. Li et al [24] performed creep tests on remolded loess and observed changes in the microstructural parameters of the soil during creep deformation. The most significant variations were observed in pore and grain size (pore diameter, grain diameter) and shape (roundness), while other microstructural parameters such as circularity, contour fractal dimension, and probability entropy remained relatively unchanged.…”

Effects of Acidic/Alkaline Contamination on the Physical and Mechanical Properties of Silty Clay

“…Compared to reconstituted soil, the most remarkable characteristics of undisturbed soil is that it maintains its natural structure, which is related to the grain composition of the soil in addition to the stress history and sedimentary environment. In order to avoid the influence of naturally-occurring structural differences among the soil samples on the test results, the silty clay was remolded [37,38]. Considering that a soil sample soaked in an acidic solution could be damaged, a large dry density standard was adopted in the remolding process.…”

Modification and Stabilization of Collapsible Loess Using Diammonium Phosphate Solution

“…Loess, widely distributed in the Loess Plateau in Western China [1,2], forms as winddeposited sediment under the arid and semi-arid climatic conditions of the Quaternary period [3][4][5]. Grain-size analysis indicates that the grain-size fraction of loess ranges from 0.02 to 0.05 mm.…”