| In order to research the effects of different width of scouring flumes on characteristics of slope scouring erosion, this study used the colluvial deposits of collapsing hill as the research object, and through the simulated scouring in laboratory, adopted double factor experiment design, and set up five different width of scouring flumes (10,20,30,40,50 cm) and four different discharge per unit width (1.2×10-2, 2.4×10-2,3.6×10-2,4.8×10-2 m2/min) combined with field investigation. This study intended to research the characteristics of colluvial deposits sediment and runoff yield and eroded sediment particles, hydrodynamics mechanism of slope erosion and the microtopography characteristics of slope surface, disclose the effects of scouring flumes width on colluvial deposits of collapsing hill, and provide reference for the selection of different width of scouring flumes under laboratory conditions. Main results were as followed:(1) The width of scouring flumes had effects on initial runoff time when the discharge per unit width was 1.2×10-2,2.4×10-2 m2/min, while had no effects when the discharge per unit width was 3.6×10-2,4.8×10-2 m2/min. The width of scouring flumes had significant effects on the runoff rate and sediment yield rate when the discharge per unit width was 1.2×10-2,2.4×10-2,3.6×10-2m2/min (P<0.05), while had no significant effects when the discharge per unit width was 4.8×10-2 m2/min; When the discharge per unit width was constant, the trends of runoff rate under different width of scouring flumes over time was identical, the trends of sediment yield rate and sediment concentration over time under different width of scouring flumes was different only when the discharge per unit width was 1.2×10-2 m2/min. When the discharge per unit width was constant, the differences of cumulative runoff yield under different width of scouring flumes was not significant, and that of the cumulative sediment yield and the average sediment concentration was significant (P<0.05) while the discharge per unit width was 1.2×10-2,2.4×10-2,3.6×10-2 m2/min; when the discharge per unit width was 4.8×10-2 m2/min, the width of scouring flumes had no significant effects on the cumulative sediment yield and the average sediment concentration.(2) With the increase of discharge per unit width, eroded sediment particles in coarse graining. Gravel concentration and sediment yield rate had a close positive correlation. When the discharge per unit width was 1.2×10-2 m2/min, eroded sediment particles was given priority to clay and coarse sand, the trends of clay and coarse sand content over time were different under different width of scouring flumes. The enrichment ratio of gravel and coarse sand particles were less than 1 and that of fine sand, coarse powder, fine powder and clay were greater than 1. Runoff preferentially carry fine particulate matter. When the discharge per unit width was 4.8x10-2 m2/min, eroded sediment particles was given priority to coarse sand and gravel, the trends of different particles grade over time were identical under different width of scouring flumes. The enrichment ratio of gravel and coarse sand particles were close to 1, close to the tested soil. The enrichment ratio of fine sand, coarse powder, fine powder and clay were greater than 1. The greater the discharge per unit width, the greater the mean weight diameter (MWD) of eroded sediment particles. When the discharge per unit width was constant, the mean weight diameter(MWD) of eroded sediment particles under different width of scouring flumes had a close relationship with sediment yield rate.(3) With the increase of discharge per unit width, flow velocity, water depth, Reynolds number were significantly increased, the trends of the Froude number, resistance coefficient and roughness coefficient under different width of scouring flumes were different over discharge per unit width. When the discharge per unit width was 3.6×10-2,4.8×10-2 m2/min, flow velocity, water depth, Reynolds number increased with the increase of scouring flumes width, while had a change of polynomial and fluctuation when the discharge per unit width was 1.2×10-2,2.4×10-2 m2/min. When the discharge per unit width was 1.2×10-2 m2/min, the changes of Froude number, resistance coefficient and roughness coefficient over width of scouring flumes were different from other discharge per unit width. Sediment yield rate was closely related to flow regime but had no significant relationship with flow pattern. Discharge per unit width had highly significant effects with all the hydraulic parameters (P<0.01), the width of scouring flumes had highly significant effects with water depth (P<0.01), had significant effects with the Reynolds number (P<0.05), had no significant effects with other hydraulic parameters. Sediment transport rate was not related to roughness coefficient but highly related to all the other hydraulic parameters (P<0.01). All the kinetic parameters significantly increased with the increase of discharge per unit width, when the width of scouring flumes was 10 cm, all the kinetic parameters were smaller. The trends of hydrodynamic shear stress and stream power with the increase of scouring flumes width were unanimous, when the discharge per unit width were 1.2×10-2,2.4×10-2,3.6×10-2 m2/min, hydrodynamic shear stress and stream power increased first and then decreased with the increase of scouring flumes width, while increased with the increase of scouring flumes width all the way when the discharge per unit width was 4.8×10-2 m2/min. The width of scouring flumes had no significant effects on unit stream power and cross-sectional unit energy. The discharge per unit width had highly significant effects with all the kinetic parameters (P<0.01), the width of scouring flumes had highly significant effects with hydrodynamic shear stress, stream power and cross-sectional unit energy (P<0.01), and had no significant effects with unit stream power. Sediment transport rate was highly related to all the kinetic parameters (P<0.01).(4) When the discharge per unit width were 1.2×10-2,2.4×10-2m2/min, the width of scouring flumes had significant effects with rill occurrence time (P<0.05), while had no significant effects with rill occurrence time when the discharge per unit width were 3.6×10-2,4.8×10-2 m2/min. When the discharge per unit width was constant, rill density decreased with the increase of scouring flumes width, average rill width had different changes with the increase of scouring flumes width, average rill depth increased first and then decreased with the increase of scouring flumes width, the width and depth ratio of rill under different width of scouring flumes had no significant differences. When the width of scouring flumes was constant, rill density and average rill width had different trends with the change of the discharge per unit width, average rill depth increased with the increase of the discharge per unit width, the width and depth ratio of rill decreased with the increase of the discharge per unit width. The average differences of sediment yield of slope erosion with oven dry method and scanning method were between 1%～4%, and the measure precision was high. The roughness of soil surface was increased after the scouring experiments, and the amplifications was between 0.15-0.98. The resolution ratio of 3D laser scanner had no significant effects with the measurements of sediment yield of slope erosion, but had significant effects with the measurements of roughness of soil surface. We could analyze the change of slope soil thickness in the process of scouring erosion through the superposition of scanning DEM that before and after scouring erosion, and intuitively understand the status of the slope rill, and can also obtain the erosion intensity level at different positions of the slope surface. |
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