露天矿排土场平台-边坡系统侵蚀形态及径流产沙特征

露天矿排土场平台径流汇集量大且急促,常导致边坡发生强烈沟蚀。排土场平台-边坡系统集中来水条件下的侵蚀过程研究仍十分薄弱。本研究以平台-边坡系统为对象,采用野外放水冲刷试验方法,研究不同放水流量(48、60、72、84 L·min^-1)下系统径流、产沙及侵蚀形态演变规律。结果表明: 48 L·min^-1流量时,平台-边坡系统以细沟侵蚀为主,60～84 L·min^-1流量下系统发育形成切沟。平台、边坡流速随放水历时呈突变-波动-稳定变化趋势,平台流速小于边坡径流流速,减幅为8.3%～67.1%,边坡流速为边坡上/下部最大,较中部增加18.5%～44.6%。平台和边坡产沙率随放水历时呈现突变-波动-稳定3个阶段,边坡产沙率高达平台的17.4倍;平台上细沟侵蚀产沙量占比高达86.6%～95.1%,60～84 L·min^-1流量下边坡切沟侵蚀产沙量占比高达69.2%～86.6%。平台侵蚀沟宽深比大于边坡,边坡宽深比为边坡上部最小,边坡中/下部最大,是边坡上部的1.36～1.93倍,侵蚀沟沿平台至坡脚总体上呈“宽浅-窄深-宽浅”式发展;48 L·min^-1流量下侵蚀主要集中在平台与边坡中部,侵蚀体积占比分别为29.9%、26.8%;60～84 L·min^-1流量时,侵蚀集中在边坡上部,占总侵蚀体积的36.1%～44.7%。结果可为陕北露天矿排土场平台-边坡系统沟蚀防治及侵蚀产沙模型的建立和修正提供参考。

Erosion morphology and the characteristics of runoff and sediment yielding in platform-slope system of opencast coal mine

In the open pit, runoff from the platform is large discharge and rapid afflux, which often results in serious gully erosion of dump slope. The study of erosion process under catchment conditions of the platform-slope system is still backward. In this study, field scouring experiments were conducted to investigate runoff characteristics and sediment yield processes of the platform-slope system under different flow discharges (48, 60, 72 and 84 L·min^-1). Our results showed that rill erosion dominated the platform-slope system under the flow discharge of 48 L·min^-1, and gully was formed under 60-84 L·min^-1. The flow velocity of the platform and the slope showed an abrupting-fluctuating-stable trend with the duration of discharge. The flow velocity of the platform was smaller than that of the slope, with the magnitude of reduction at 8.3%-67.1%. The highest flow velocity appeared on the up-slop/down-slope, being 18.5%-44.6% higher than that of the middle-slope. In general, the sediment yield rate of the platform and the slope varied with the duration of discharge, with the sediment yield rate of the slope being 17.4 times as that of the platform. The ratio of gully width to depth showed substantial difference between the platform and slope. The platform generally had the largest ratio than the slope. For the slope, the largest ratio appeared on the middle-slop/down-slope, being 1.36-1.93 times as that of the up-slope. The morphology of rill and gully along the platform to down-slope presented in the form of “wide and shallow-narrow and deep-wide and shallow”. Rill erosion mainly concentrated in the platform and the middle slope under the flow discharge of 48 L·min^-1, contributed 29.9% and 26.8% of the total erosion volume, respectively. When the flow discharge increased to 60-84 L·min^-1, the largest average across-section areas (1083.25-1737.86 cm²) formed on the up-slope accounted for 36.1%-44.7% of the total erosion volume. Our results provided evidence for modelling soil and water erosion of the platform-slope system in opencast coal mine.