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

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.

Effects of Irrigation Projects on the Classification of Yellow River Terrace Landslides and their Failure Modes: A Case Study of Heitai Terrace

“…Distant from the platform's edge, the sinkholes are observed to be evolving into cracks (Figure 11d). Moreover, spring activity persists at the foot of the slope, and our previous research confirmed that the loss of soluble material via the spring is positively correlated with slope deformation (Figure 11f) [35].…”

“…It is worth noting that local small-scale failure occurred near the phreatic line of some landslides, with a high probability of extension into the surrounding area; multi-stage cracks had developed in the sidewalls and crowns of the failure areas, and springs continued to discharge outwards (Figure 3a). Previous studies have confirmed that the soil strength in the spring discharge path is markedly reduced owing to changes in soil properties, and soil deformation is related to the total amount of soluble material lost from the soil interior via spring water [35,37]. In addition, both land use and spring discharge have significant impacts on groundwater [21,59,60], causing an increase in hydraulic gradient and positive pore water pressure owing to the differential rise in groundwater caused by the crop planting structure, which may also contribute to the failure at this site.…”

“…In fact, approximately 28% of the landslides that occurred in the early phases of the Heitai were shallow landslides unrelated to groundwater [16], and such landslides still exist today. In addition, wind-deposited loess, which has a sub-stable structure [14,27,28], is extremely water-sensitive [27,29], leading to soil strength attenuation caused by changes in soil properties after long periods of intense soil-water interaction [27,[30][31][32][33][34][35][36][37], which in turn contribute significantly to landslides [37]. Therefore, understanding the key triggering factors for slope failure in the context of irrigation engineering, combined with attempts to develop a classification scheme for loessrelated landslides and a summary of damage patterns for Yellow River terrace landslides, is timely.…”

Impact of Water Level Fluctuations on Landslide Deformation at Longyangxia Reservoir, Qinghai Province, China

“…The two most common multitemporal technologies are permanent scatterer interferometric synthetic aperture radar (PS-InSAR) [24,25], which is dominated by permanent scatterers, and small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) [26,27], which is dominated by distributed scatterers. The application of these technologies has achieved outstanding results in the study of land subsidence and landslide movement [28][29][30][31][32][33][34]. Remote sensing has also become a conventional method in the monitoring of land surface water [35].…”

Editorial for the Special Issue “Water-Induced Landslides: Prediction and Control”

“…On the other hand, Xue et al [15] documented the influence of soaking time and salt concentration on the behavior of some samples taken from a soil subjected to water irrigation. The problem of the soluble salt loss and its effect on irrigation-induced landslides was also studied by Zhang et al [16].…”