土体构型对花岗岩红壤细沟发育形态的影响

Influence of Soil Configuration on the Morphology of the Rill Development in Granitic Red Soil

为探究花岗岩红壤细沟形态特殊变化的原因,解释土体构型影响细沟形态发育的机理。设计单一红土层(H)、单一砂土层(S)、上红下砂层状土层(HS)3种土体构型、不同径流量(低径流量3 L/min、高径流量6 L/min)和不同坡度(中坡20°、陡坡40°)的室内模拟细沟冲刷试验。结果表明:H处理下,细沟形态更多向“V”形和“U”形发育;S处理下,细沟沟道发育过程中短暂形成上窄下宽的深宽梯形断面后,完全崩塌;HS处理下,细沟形态能发育为梯形断面,且能继续扩大发育。与H和S相比,HS陡坡(40°)处理下沟岸崩塌更加频繁且单次大质量崩塌更多。HS陡坡(40°)处理下沟岸崩塌发生21次,其中,单次崩塌量>1 kg的占比为63%。HS与H和S相比,雷诺数(Re)和弗罗德数(Fr)的波动更剧烈,更有利于梯形断面形成。与H、S相比,HS沟壁崩塌发生时,上层红土层含水量最低为0.31 cm^(3)/cm^(3),抗剪强度最高为178 kPa;而下层砂土层含水量较高(0.33 cm^(3)/cm^(3)),抗剪强度最小为54 kPa。上红下砂土层的土体构型是花岗岩红壤细沟沟道形态发育为上窄下宽深宽梯形断面的龛沟重要原因,陡坡和高径流量更有利于细沟内特殊形态的形成和发育,龛沟作为崩岗发育的初始阶段。该结果可为防治崩岗初期发育提供理论依据。

In order to investigate the reasons for the special variation in the fine furrow morphology of the granitic red soil the rill and to explain how soil configuration influences the development of the rill morphology.we designed three soil configurations(H,S,and HS)with different runoff rates.Three soil configurations,namely,a singlered soil layer(H),single sandy soil layer(S)and upper red and lower sandy laminated soil layer(HS),were designed to simulate indoor fine furrow scouring experiments with different runoff rates(low runoff rate 3 L/min,high runoff rate 6 L/min)and different slopes(medium slope 20°,steep slope 40°).The results showed that:under the H treatment,the gully morphology developed more towards"V"and"U";under the S treatment,the gully formed a deep and wide trapezoidal cross-section with a narrow top and a wide bottom for a short period of time during the process of the rill development,and then collapsed;under the HS treatment,the gully morphology was able to develop into a trapezoidal section and could continue to expand and develop.Compared with H and S,21 gully bank failures occurred in the HS steep slope(40°)treatment,of which 63%had single failures of>1 kg.The HS steep slope(40°)treatment had more frequent gully bank failures.The fluctuations of Re and Fr were more drastic than those in the H and S treatments,which is more favourable to the formation of trapezoidal sections.the upper red layer of HS had the lowest water content of 0.31 cm^(3)/cm^(3) and the highest shear strength of 178 kPa at the time of HS the rill collapse compared to H and S.The lower sand soil layer of HS had a higher water content of 0.33 cm^(3)/cm^(3) and the lowest shear strength of 54 kPa.The soil configuration of upper red and lower sandy laminated soil layer was the niche the ephemercil gully where the rill morphology of the granitic red soil rill developed into an upper-narrower and lower-deeper and wider trapezoidal profile steep slopes and high runoff volume are more favourable to the formation and development of specific patterns in the rill,and the niche furrows are the initial stage of the development of the Benggang.The results could provide a theoretical basis for the prevention and control of the initial development of the Benggang.