A longitudinal analysis of collapsibility with predictions over the southeastern Loess Plateau in China

Ziyu Zheng,Xi-An Li,Li Wang

doi:10.1038/s41598-021-02623-2

Abstract

Loess presents very unique collapsible behaviour due to its special under-compactness, weak cementation and porousness. Many environmental issues and geological hazards including subgrade subsidences, slope collapses or failures, building cracking and so on are directly caused by the collapsible deformation of loess. Such collapsible behaviour may also severe accidents due to sinkholes, underground caves or loess gullies. Moreover, with the increasing demand of construction and development in the loess areas, an in-depth research towards effective evaluation of loess collapsibility is urged. Currently no studies have made attempts to explore a rather complete and representative area of Loess Plateau. This paper thus provides a novel approach on spatial modelling over Jin-Shan Loess Plateau as an extension to experimental studies. The in-lab experiment results have shown that shown that the porosity ratio and collapsibility follow a Gaussian distribution and a Gamma distribution respectively for both sampling areas: Yan’an and Lv Liang. This establishes the prior intuition towards spatial modelling which provides insights of potential influential factors on loess collapsibility and further sets a potential direction of the loess studies by considering an extra dimension of spatial correlation. Such modelling allows robust predictions taken into account of longitudinal information as well as structural parameters and basic physical properties. Water contents, dry densities, pressure levels and elevations of samples are determined to be statistically significant factors which affect the loess collapsibility. All regions in Lv Liang area are at risk of high collapsibility with average around 0.03, out of which roughly a third of them are predicted to be at high risk. Clear spatial patterns of higher expected collapsibility in the southwest comparing to the northeast are shown adjusting for influential covariates. On reference guidelines for potential policy makings, county-level regions with the highest expected loess collapsibility are also identified.

Highlights

Loess is widely distributed across the world with the largest proportion sits in China which accounts for 10% of the Earth’s land surface[1,2,3]
The initiation for exploratory study considered the behaviour of collapsibility from a combination of effects of dry density, water content, porosity ratio and press
That is saying that the higher water contents, press levels, porosity ratios and dry densities are, the lower collapsibility coefficients are

Summary

Introduction

Loess is widely distributed across the world with the largest proportion sits in China which accounts for 10% of the Earth’s land surface[1,2,3]. The erosional landforms in loess, such as loess pillar, loess walls, loess towers and loess caves compared with the topography of karst areas are known as loess karst[10] It is one of the typical environmental issues caused by collapsibility directly leading to to subgrade subsidences, slope collapses or failures, building cracking and so on. The loess structural failure occurs as the pore structures gradually collapse under water or other external forces such as tectonic uplift or earthquakes[9,33] Such deformation is related to a combination of factors representing the structural parameters, basic fabric properties and spatial environmental features. These could be reflected on the locations of sampling; the closer the locations are the more similar environmental conditions the loess samples are under

Methods

Results

Conclusion