Soil Atterberg limits of different weathering profiles of the collapsing gullies in the hilly granitic region of southern China

Abstract

Abstract. Collapsing gullies are one of the most serious soil erosion problems in the tropical and subtropical areas of southern China. However, few studies have been performed on the relationship of soil Atterberg limits with soil profiles of the collapsing gullies. Soil Atterberg limits, which include plastic limit and liquid limit, have been proposed as indicators for soil vulnerability to degradation. Here, the soil Atterberg limits within different weathering profiles and their relationships with soil physicochemical properties were investigated by characterizing four collapsing gullies in four counties in the hilly granitic region of southern China. The results showed that with the fall of weathering degree, there was a sharp decrease in plastic limit, liquid limit, plasticity index, soil organic matter, cation exchange capacity and free iron oxide. Additionally, there was a gradual increase in liquidity index, a sharp increase in particle density and bulk density followed by a slight decline, a decrease in the finer soil particles, a noticeable decline in the clay contents, and a considerable increase in the gravel and sand contents. The plastic limit varied from 19.43 to 35.93 % in TC, 19.51 to 33.82 % in GX, 19.32 to 35.58 % in AX and 18.91 to 36.56 % in WH, while the liquid limit varied from 30.91 to 62.68 % in TC, 30.89 to 57.70 % in GX, 32.48 to 65.71 % in AX and 30.77 to 62.70 % in WH, respectively. The soil Atterberg limits in the sandy soil layers and detritus layers were lower than those in the surface layers and red soil layers, which results in higher vulnerability of the sandy soil layers and detritus layers to erosion and finally the formation of the collapsing gully. The regression analyses showed that soil Atterberg limits had significant and positive correlation with SOM, clay content, cationic exchange capacity and Fe d , significant and negative correlation with sand content and no obvious correlation with other properties. The results of this study revealed that soil Atterberg limits are an informative indicator to reflect the weathering degree of different weathering profiles of the collapsing gullies in the hilly granitic region.

Assessment of geotechnical and physico-chemical properties of age-long greywater-contaminated soils in basement complex areas, southwest Nigeria

“…Positive correlation between PL and PI agrees with Larney et al (1988) and Tsegaye et al (2017). However, our results of negative correlations between CEC and ALs, CEC and PI are in contrast with positive correlation between soil ALs and CEC reported by Deng et al (2017). Soil resistivity exhibits strong positive correlations with OM (1.000**), soil resistivity and shear strength (1.000**), and positive correlation at 5% level exists between soil resistivity and CBR (0.634*).…”

“…Negative correlation between % sand and MC is in line with similar results by Senjobi and Ogunkunle (2011) and Olorunfemi et al (2016). The strong negative correlation between % sand and ALs agrees with similar results by Deng et al (2017) and Igwe et al (2013), while correlation between % sand and PI (− 1.000**) is in line with similar result by Roy and Bhalla (2017) who reported that increase in sand content results in decreased PI.…”

Effects of pH-Induced Changes in Soil Physical Characteristics on the Development of Soil Water Erosion

“…Considering the results as indicated by black dots in Figure 3, the LL and I P in particular increased with increasing pH from 2.0 to 6.0 and then decreased as pH increased further to 10.0 in Figure 3. As LL, PL, and I P depend primarily on soil texture, which is related to the particle-size distribution [7,28], the changes in LL, PL, and I P with pH resulted from changes in soil particle size. As shown in Figure 4, the proportion of soil particles with sizes less than 0.01 mm decreased as pH decreased from 6.0 to 2.0.…”

“…This issue has been frequently reported in Southeast Asian countries with tropical climates [3][4][5], where squalls with high rain intensity are a major contributor to the erosion caused by water [6]. The physical characteristics of soils such as attraction force among soil particles, Atterberg limits, which include the liquid limit (LL) and plastic limit (PL) and indicate the soil's vulnerability to degradation, and soil particle size also contribute to the erosion [7,8]. For example, low-LL soils easily transform into viscous liquids with increasing water content and are easily transported by rainwater, making them susceptible to soil water erosion.…”

Degradation Characteristics of Soil-Quality-Related Physical and Chemical Properties Affected by Collapsing Gully: The Case of Subtropical Hilly Region, China

“…For a better understanding of the high-steep slope of a collapsing wall and the mechanism of collapsing erosion, the engineering characteristics and preferential flows have also been investigated for the profile of the collapsing wall. Some researchers analyzed the spatial variations of shear strength and hydraulic properties in collapsing gullies and evaluated their effects on the collapsing erosion mechanism [14,[18][19][20]. Additionally, researchers have also investigated the variations of chemical composition and physical properties with soil depth in the collapsing gullies and found that the contents of gravel and sand increase while the amount of sesquioxides decreases with an increase of soil depth [21,22].…”