Experimental investigation of the creep behaviour of remoulded loess under different levels of compactness.

Hao Tang,Dongpo Wang,Jinzhi Luo,Shengwen Qi,Zhao Duan,Yougui Song

doi:10.1371/journal.pone.0262456

Abstract

Generally, a loess high fill project will undergo a time-dependent deformation and settlement process for a long time after the initial fill. Understanding the creeping behaviour of compacted loess is an important part of determining the stability of a compacted loess foundation. To study the creep behaviour of remoulded loess under different levels of compactness, we performed triaxial shear and triaxial creep tests using Q2 loess specimens obtained from the new district of Yan’an city. Based on laboratory test results, the triaxial shear and creep characteristics of remoulded loess under different levels compactness are summarised. The regularity of instantaneous strain, creep strain, total accumulated strain and initial shear modulus were analysed and the relationship between the compactness and long-term strength of remoulded loess is provided. It was found that the remoulded loess becomes harder and its long-term strength increases with an increase in compactness. Furthermore, we propose a new creep model (HD), based on the hardening-damage mechanism, and have derived one-dimensional (1D) and three-dimensional (3D) creep equations based on this new creep model. This new creep model is flexible enough to fit the typical creep test curves of remoulded loess, while perfectly describing the tertiary creep stage. Finally, the sensitivity of the HD creep model parameters was analysed; the results indicate that the parameters denoted as α, γ, and β significantly affect the morphological changes and various stage characteristics are represented by the creep curve.

Highlights

Loess is widely distributed all over the world, including North and South America and some areas of Europe, but is especially common throughout Asia
The purpose of this study is to explore the creep characteristics of remoulded loess under different levels of compactness
(6) Under low deviatoric stress and finite creep time, only primary creep and secondary creep occurred (Fig 6(A) and 6(B)), and the secondary creep stage lasted for a longer duration; when the deviatoric stress exceeded the yield stress, after the former two stages, the tertiary creep stage eventually occurred as time went on, leading to the occurrence of creep failure (Fig 6(C)). (7) The axial compression and radial expansion deformation of samples with low levels of compactness were more obvious than those with high levels of compactness (Fig 5(B)). (8) With the increase in compactness, the failure surface of the sample became smoother and straighter; these results indicated that the remoulded loess became hard and brittle after compaction

Summary

Introduction

Loess is widely distributed all over the world, including North and South America and some areas of Europe, but is especially common throughout Asia. Some largescale loess movement projects are required, such as excavating a mountain to build a city in Yan’an for the Yan’an city new district construction project [2]. Creep behavior of remolded loess under different levels of compactness in-depth understanding of the mechanical properties of compacted loess is very important for safety in loess engineering. Creep is an important mechanical property of the long-term deformation response of compacted loess. Likewise, understanding the creep properties of loess and determining its long-term strength is significant in the design and stability evaluation of loess engineering [7, 8]

Objectives

Methods

Results

Conclusion