| Researching the hydraulic erosion characteristics of the slope protected by 3D-geomat under the condition of rainfall has important theoretical significance to reveal hydrodynamic characteristics and scouring erosion characteristics of overland flow on the slope protected by 3D-geomat, also has sense for practical application and optimization design that 3D-geomat plays a role in slope protection. Taking advantage of the method included simulating rainfall experiment indoor and theory analysis, choosing five grade (12°,18°,24°,30°,38°) and three rainfall intensity (1.0 mm/min,1.5mm/min,2.0mm/min) according to actual engineering, this paper researches the influence of the characteristics of overland flow on the slope protected by 3D-geomat such as hydrodynamic parameter, sand content and erosion amount to rainfall intensity and gradient and the relationship between the hydrodynamic parameters and the erosion.1. Slope flow velocity was evaluated by potassium permanganate tracer method: At the beginning of the simulating rainfall experiment, the slope flow velocity is the largest, as the test continuing, the flow rate decreases rapidly, late experiment period the flow rate gradually stabilizes and fluctuates up and down in a fixed value. The flow velocity increased gradually along the slope, the maximum velocity appears in the slope toe, the mean velocity of the whole slope is about 0.1 m/s. Analyzing the correlation between control variables which choose the rainfall intensity, slope, distance from the top as and the mean velocity of slope, the results show that the mean velocity of slope were significantly associated with rainfall intensity and distance from the top that the effect slope to the average flow velocity is not obvious. Overland flow average water depth and discharge per unit width has the power function relationship,h= 0.2516q0.824, R2=0.9061.2. This article used the concept of flow Reynolds number, and used wash bump height to instead of section depth to determine the type of overland flow, overland flow was the turbulent flow (the upper part exists transition flow), the Froude number of overland flow in each section of on average the Froude number change between 0.9344～1.5745,12～38°slope showed that the test range from 12°to 38°,the flow pattern of whole overland flow belongs to the category of the rapids. The relationship between drag coefficient and slope length show diminishing power function, relational expression is f = aL-b, drag coefficient has increasing trend with the slope increasing. The relationship between Reynolds number and the Froude number is power function, and the relationship between resistance coefficient and Reynolds number is power function, the Froude number and Resistance coefficient are related.3. Determining of runoff erosion and sediment content by pycnometer method: with the increase of rainfall intensity and slope, in the early, the greater slope surface sediment concentration was, after a certain period of time (15 min), the sediment concentration under different slope and rainfall intensity was basic stability and close, almost overlapping. Cumulative erosion increases with the increase of rainfall intensity, and the rainfall erosion accounts was more than 60% of the whole test process in early 15 min of the testing.4. 3D-geomat pad exist critical slope, cumulative erosion increases with the increasing of slope within a certain slope, after reaching a certain degree (30°) erosion fall instead. The critical slope of this test was the range from 24°to 38°.5. There is a power function of Reynolds number between erosion and sediment concentration. The relationship between Froude number and erosion is complex, within a certain range, cumulative erosion increases with the increase of the Froude number, after reaching a certain degree, declines with the increase of the Froude number. |
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