College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.
PeerJ. 2022 Jun 1;10:e13526. doi: 10.7717/peerj.13526. eCollection 2022.
Benggang with steep collapsing walls is one of the worst soil erosion problems in South China. The collapse of walls is the most critical process in Benggang development. This is mainly due to the soil water properties. The soil water characteristic curve (SWCC) is a key indicator for analyzing soil moisture, but the SWCC and its mechanism of influence in collapsing walls remain obscure. A pressure plate meter was used for drying experiments to research the SWCCs of undisturbed soils of five layers (from top to bottom: red soil layer, transition layer I, sand soil layer, transition layer II and detrital layer) of two typical collapsing walls. The van Genuchten (VG) model can be fitted to the SWCCs for different layers (NSE ≥ 0.90). With increasing soil depth, the parameters and first decreased and then increased, the parameters first increased and then decreased, declined as the soil depth increased. These findings illustrate that soil water holding capacity decreases with increasing soil depth. The bottom of the soil is weak in water retention and water can easily reach saturation, resulting in a decline in soil stability, thus promoting soil collapse and finally inducing upper soil collapse. Furthermore, gravel content and particle morphology are factors that should not be neglected for SWCCs. The results of this study provide a theoretical basis for understanding the process of wall collapse in Benggang landforms in South China.
崩岗是华南地区最严重的水土流失问题之一，其具有陡立的崩壁。崩壁的崩塌是崩岗发育的最关键过程。这主要是由于土壤水分特性所致。土壤水分特征曲线（SWCC）是分析土壤水分的关键指标，但崩塌土中 SWCC 及其影响机制仍不清楚。采用压力板仪对 2 个典型崩岗的 5 层原状土（从上到下分别为：红土层、过渡层 I、砂土层、过渡层 II 和碎屑层）进行了干燥试验，研究了其 SWCC。VG 模型可以很好地拟合不同土层的 SWCC（NSE≥0.90）。随着土壤深度的增加，参数 和 先减小后增大，参数 先增大后减小， 随土壤深度的增加而减小。这些发现表明，土壤持水能力随土壤深度的增加而降低。土壤底部保水能力较弱，水分容易达到饱和，导致土壤稳定性下降，从而促进土壤崩塌，最终导致上层土壤崩塌。此外，砾石含量和颗粒形态也是 SWCC 不可忽视的因素。本研究结果为理解华南崩岗地貌的崩壁崩塌过程提供了理论依据。
