Abstract
Abstract The climate is a significant factor affecting the collapsing gully in weathered granite areas, and most of the surface layers of the collapsed area comprise granite residual soil. Granite residual soil has complex disintegration characteristics under different initial water content conditions. Besides, its disintegration characteristic is an essential factor for collapsing gully. Therefore, disintegration tests, triaxial shear tests, nuclear magnetic resonance tests, and hydraulic conductivity tests are conducted under torridity and rainstorm conditions in order to study the disintegration characteristics of granite residual soil. The results of disintegration test showed that the initial disintegration rate of granite residual soil increased rapidly with the decrease in water content, while the relationship between disintegration rate and water content in the later stage of disintegration is unclear. When soaked, the maximum decrease in cohesion was 44.48%, the hydraulic conductivity became six times larger, and the amplitude of the T 2 curve increased by about 40%, which reduced the strength of the soil and provided better access for rainwater infiltration to deeper stratum. The results show that the microstructure of granite residual soil would be damaged and the disintegration would occur after a rainstorm at low water content. Micropores would be formed inside the sample after soaking, resulting in destroying the continuity of the material.
Highlights
Collapsing gully called benggang by local people is a serious soil erosion in the granite-weathered area of southern China; it damages the local landform and even causes disasters [1,2,3]
The unsaturated strength characteristics of graniteweathered soils under different initial moisture content conditions have been explored by some researchers [10,11,12]; the samples were directly tested without the soaking process, that is, the damage caused by rapid infiltration might be ignored
In the early stage of disintegration, the disintegration rate could reach the maximum value of about 0.45%/s when the moisture content of the sample was 0.6%, the average disintegration rate was less than 0.085%/s and the disintegration rate varied greatly
Summary
Collapsing gully called benggang by local people is a serious soil erosion in the granite-weathered area of southern China; it damages the local landform and even causes disasters [1,2,3]. The unsaturated strength characteristics of graniteweathered soils under different initial moisture content conditions have been explored by some researchers [10,11,12]; the samples were directly tested without the soaking process, that is, the damage caused by rapid infiltration might be ignored. The changes in the tensile strength of remolded soils with different water contents before and after soaking were studied by Cernuda et al [18], revealing that the pore air pressure caused by rapid infiltration could destroy the microstructure of the soil. These studies lack comparative and relationships among mechanical analysis, microscopic analysis, and undisturbed soils In most of those studies, the pore air pressure and disintegration tests of materials were only measured while the changes in strength characteristics, microscopic characteristics, and hydraulic conductivity of dry soils after soaking were ignored. The disintegration rules of granite residual soil are analyzed from three aspects, that is, disintegration rate, strength characteristics, and micro characteristics
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