Correlation between shear strength and soil physicochemical properties of different weathering profiles of the non-eroded and collapsing gully soils in southern China

Abstract

Collapsing gully erosion is a specific form of soil erosion that is widely distributed in the hilly granitic region of tropical and subtropical southern China and resulted in extremely rapid water and soil loss. The aim of this study was to investigate the correlations between soil physicochemical and shear properties and the clay mineralogical of different profiles of the non-eroded soils (without soil erosion) and collapsing gully soils in Changting County, Fujian Province, southeastern China. A total of 32 sampling soils collected from four pedons of non-eroded and collapsing gully soils were subjected to conventional soil analyses for physicochemical properties. The soil shear strength of collected soils was measured using a triaxial shear apparatus according to the unconsolidated-undrained (UU) method. The clay mineralogical of different profiles soils was examined with an X-ray diffraction (XRD) analysis. The results showed that non-eroded soils had superior physicochemical characteristics. The cohesive force of the non-eroded soils was generally greater than that of collapsing gully soils. The XRD patterns of the clay fraction indicated that kaolinite, illite, hydroxy-interlayered vermiculite (HIV), and gibbsite were the dominant clay minerals in the studied soils. Pearson’s correlation analysis showed that the cohesive force of the studied soils had significant and positive correlations with CEC, exchangeable Al3+ + H+, Fed, Ald, and Fet; the correlation coefficients (R value) for cohesive force were greater than those of internal friction angle. The stepwise multiple linear regression analyses indicated that exchangeable Al3+ + H+ and Ald were the dominant factors affecting cohesive force. Compared with collapsing gully soils, non-eroded soils had superior physicochemical and shear properties, indicating that non-eroded soils were better able to resist soil erosion. The findings obtained in the present study were of fundamental significance in understanding the correlation between shear strength and the soil physicochemical properties in the non-eroded soils and collapsing gully soils of tropical and subtropical China.