Abstract
Roots play a major role in reinforcing and stabilizing soil. The pullout mechanical characteristics of soil reinforcement and slope protection of the root systems of dominant shrub species (Pyracantha and Geranium) were estimated by in-situ pullout tests in a karst area, in which roots were pulled out from soil to reliably test the pulling force. The goals of this study were to discover the pullout mechanical properties of roots in karst areas and to try to analyse the impact of the root system on landslide control. The F–s curves were multipeak curves with a noticeable main peak and main double peaks. The curves showed a linear increasing trend at the initial stage of drawing and decreased rapidly after reaching the peak. The F–s curves of root systems inserted into rock cracks showed secondary fluctuations in the later stage of drawing, and rock cracks stimulated the tensile efficiency of the root system more effectively. Field in situ pullout results indicate that tree roots fail progressively rather than simultaneously. The maximum pulling force had a linear relationship with the increase in soil thickness and a disproportionate increasing trend with the increasing number of broken roots. The displacement of the maximum peak was different between the two tree species and was concentrated at 5–15 cm and 5–25 cm for Pyracantha and Geranium, respectively. The maximum pulling force of Geranium was 1.29 times that of Pyracantha, and the root system of Geranium had strong pullout resistance. We concluded that the peak distribution of the F–s curves was affected by broken roots and rock cracks, while soil thickness and the number of broken roots had positive effects on the maximum pulling force, all of which is helpful in understanding the effect of root pullout mechanical properties on landslides in karst areas.
Highlights
The F–s curves of the two tree species were divided into two categories according to
The F–s curvesofofthe thepeaks, two tree weremultipeak divided into two with categories according to the characteristics andspecies they were curves a noticeable main the characteristics of the peaks, and they were multipeak curves with a noticeable main peak and main double peaks
The curves a similar trend in thedropped early stage of pulling: the pulling force increased linearly with had displacement and sharply in an the pulling pattern force increased with displacement and dropped sharply in an undulating after the linearly maximum peak appeared
Summary
Accepted: 9 March 2022As a representative area of the karst plateau in China, Guizhou Province is known as the karst province in China. Due to the interaction of natural environments (rainfall and geological geomorphology of carbonate rocks) with man-made disturbances and damage, this area suffers from severe soil erosion, large-area bare bedrock and degradation in land productivity [1]. Soil loss is the main factor causing karst rocky desertification, considered one of the most serious ecological, geological and environmental problems in Southwest. Long-term karstification forms the surface and underground double layer space structure in the karst region, in which the surface is rugged complex terrain, and the underground is a large underground river system. Under the interaction of natural factors (rainfall and geological geomorphology) and human activities, the surface presents a rocky desertification landscape with a shallow soil layer, discontinuous regolith and even large areas of bare rock. Landslides are more likely to occur in karst areas due to the complex heterogeneity of underground space (Figure 1). Landslides are a pervasive natural hazard in alpine regions [3] that threaten the built and natural environment [4]
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