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

Zhenxiao Li,Shuai Yang,Shehu Liu,Yongwei Li,Jiading Wang

doi:10.3390/w14030438

Zhenxiao Li, Shuai Yang + Show 3 more

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https://doi.org/10.3390/w14030438

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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.

Highlights

Loess is widely distributed in semi-arid and arid regions of the world, including China, Russia, USA, UK, France, Germany, Italy, Israel, New Zealand and other countries [1]
Under the conditions of the triaxial creep test, the macroscopic creep characteristics of loess are caused by the change in the internal microstructure of loess
Quantitative analysis shows that in the process of the triaxial creep test, the soil structure of the intact loess gradually becomes compact, the debris material and viscous material on the surface of the particles increase, the soil particles gradually change from mainly granular and massive to mainly agglomerated, the overhead pores in the soil pores decrease and the intergranular pores increase

Summary

Introduction

Loess is widely distributed in semi-arid and arid regions of the world, including China, Russia, USA, UK, France, Germany, Italy, Israel, New Zealand and other countries [1]. Loess is unique Aeolian sediment formed in Quaternary and features special engineering geological properties, such as water sensitivity, collapsibility, and highly developed vertical joints. Loess is a kind of Quaternary sediment formed in arid and semi-arid regions. The region’s unique conditions, such as its dry climate, sparse rainfall, and extensive evaporation, have resulted in loess that is mainly powdery, under-compacted, high in porosity, low in humidity, and rich in soluble salts (reinforcing cohesion), as well as featuring the development of characteristic vertical joints. When loess is subjected to long-term loading, creep deformation increases over time, posing a safety hazard to the environment

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