Effect of Soluble Salt Loss via Spring Water on Irrigation-Induced Landslide Deformation

Zonglin Zhang,Shufen Zhao,Xingmin Meng,Runqiang Zeng,Jianhua Ma,Yi Zhang,Yunqi Yao

doi:10.3390/w12102889

Abstract

Landslide exposes the previously blocked groundwater discharge. High concentrations of soluble salt form salt sinters that can be observed near discharge passages. Based on existing laboratory investigation results of soil leaching and shearing reported in the literature, the effect of the soluble salt loss via spring water on irrigation-induced landslide deformation was studied under large-scale conditions. During our field investigation of landslides in the Heitai terrace of the Yellow River’s upper reaches in Gansu Province, China, 35 spring outlets were found, and the Heitai terrace was divided into five subareas, based on the difference in spring flow. Deformation data for the terrace were obtained by small baseline subset technology (SBAS-InSAR). These data were analyzed in combination with the amount of soluble salt loss, to explore the correlation between the deformation of the landslide and the soluble salt loss in the loess irrigation area. The results showed that the cumulative deformation and the loss of soluble salt were increasing continuously in the terrace. Although the increasing intensity of each subarea was different, the changing intensity of the two during the corresponding monitoring period was highly consistent. The statistical analysis revealed a strong positive correlation between the accumulated loss of soluble salt via spring water and the accumulated displacement of the terrace edge (p < 0.01). After the slope k between the two was tested by the Grubbs test and t-test, the k was no abnormality (α = 0.05) and difference (Sig > 0.05), further providing the basis for confirming the existence of this positive correlation. When the loss of soluble salt in rock and soil increased gradually, the accumulated deformation of the terrace edge also increased continuously. The findings of this study are of great significance for understanding the formation mechanism of landslides and the identifying landslide revival in irrigation areas of the Loess Plateau.

Highlights

The area covered by loess in China is approximately 631,000 km2, which accounts for 6.6% of the country’s total area [1]
SBAS-interferometric synthetic aperture radar (InSAR) technology was used to Subsidence and deformation were very common in the Loess irrigation area
The shear strength can be used as an important evaluation index of landslide stability, which is closely related to factors, such as the soluble salt content or pore salt solution concentration in rock and soil

Summary

Introduction

The area covered by loess in China is approximately 631,000 km , which accounts for 6.6% of the country’s total area [1]. Several scholars have reported that rising groundwater levels aggravate the saturated area of loess and that the matrix suction inside a slope decreases under saturated water conditions [3,4]. Water 2020, 12, 2889 loess to soften and liquefy, thereby inducing a landslide’s deformation and instability [2,5,6,7,8,9,10,11] This is one of the reasons for the alteration of the stability of a landslide on the edge of the corresponding terrace, which can transform from a stable state under natural conditions to an unstable state under irrigation conditions

Methods

Results

Discussion

Conclusion