适应宽变幅流量量测的径流站量水堰过流能力试验研究OA

The runoff and confluence processes in many gullies of Northwest China are characterized by very small base flows under normal conditions,but by rapid flood responses during the rainy season,featuring high flow peaks,large flow variations,and considerable sediment loads.For runoff observation stations built on such gullies,flow-measuring weirs must be capable of adapting to wide fluctuations in flow magnitude and the influences of sediment-laden water.In this study,a newly constructed compound-section flow-measuring weir at a runoff station in a gully of Northwest China was selected as the research object.A 1∶32 physical model was established to carry out flow capacity tests and analyze the stage-flow relationships across a large flow range of 4～1 000 m³/s.The test results were verified using an electromagnetic flowmeter to ensure measurement accuracy.The results indicate that during high-flow conditions,the entire cross-section of the weir conveys flow,and the relationship between measured flow and flow depth follows a quadratic function.The measured water level agrees well with the designed stage,and the fitting accuracy is satisfactory.Under low-flow conditions,water passes only through the measuring trough of the compound section,where the stage-flow relationship still maintains a quadratic pattern,but the rate of flow increase is significantly reduced.A distinct inflection occurs as the flow transitions from the triangular section to the rectangular section.Near the two boundary transition points of the weir,the stage-flow relationship becomes less stable due to complex hydraulic interactions and local energy losses.Furthermore,the influence of sediment concentration on the flow capacity and flow coefficient was analyzed.When the sediment concentration is below 60 kg/m³,the flow coefficient of sediment-laden flow is nearly identical to that of clear water.As sediment concentration increases from 60 to 200 kg/m³,the flow coefficient decreases gradually with rising sediment content.However,when the sediment concentration exceeds 200 kg/m³,changes in the rheological properties of the sediment-laden flow lead to reduced turbulence intensity and energy dissipation,resulting in a subsequent increase in the flow coefficient with higher sediment concentration.Based on statistical regression analysis,empirical relationships between the flow coefficient of sediment-laden flow and discharge under different sediment concentrations were established.These relationships were further validated through flow measurements during the 2024 flood season.The findings provide a reliable scientific basis for the design and hydraulic calibration of flow-measuring weirs at runoff observation stations in similar environments.