排水管道内不同粒径沉积颗粒物冲刷率的分析与计算
Analysis and calculation on the scouring rate of deposited particles with different sizes in drainage pipe
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摘要: 为探究和量化在水流冲刷下，排水管道中不同粒径颗粒物冲刷沉积的过程，本文模拟排水管道内沉积颗粒的冲刷过程.冲刷过程中，粒径较小的悬移质颗粒（小于0.1 mm），在管道沿线取样测得水流中悬浮固体质量浓度（SS）；粒径较大的推移质颗粒（0.1—2 mm），测得管道沿线不同位置沉积的颗粒质量.并建立两个数学模型分别计算排水管道内两类颗粒物的冲刷率.研究发现，悬移质颗粒，以水流中SS为依据，可计算出输送通量和冲刷率；推移质颗粒，以管道不同位置沉积下来的颗粒质量为依据，拟合出了管道中的沉积分布函数，是以e为底数的指数函数，可计算出冲刷量和冲刷率.模型计算出的冲刷率呈现出规律性：悬移质颗粒被冲刷成悬浮状态，随水流迁移过程中部分会再次沉积，使得悬移质颗粒的冲刷率从管道前段至中后段逐步降低，如初始沉积质量为100 g的0.045 mm悬移质颗粒，在0.30 m·s-1的冲刷流速下，计算出管道前段冲刷率为78.94%，最终在管道后段降至13.89%；对于两类颗粒而言，颗粒物粒径越小，冲刷流速越大，初始沉积质量越小，冲刷率越高.Abstract: To explore and quantify the scouring and depositing process of particles with different sizes in drainage pipes, the scouring process of the deposited particles in the drainage pipe was simulated. In the scouring process, for the suspended particles with a smaller size less than 0.1 mm, the mass concentration of suspended solids (SS) in the water flow was measured by sampling along the pipeline. For the bedload particles with a larger size from 0.1 mm to 2 mm, the particle amount deposited at different positions along the pipeline was measured. And then two calculation models were established to calculate the scouring rate of the two kinds of particles in the drainage pipe, respectively. It was found that the transport flux and scouring rate of suspended particles could be calculated based on the SS concentration in the water flow. While the calculation of the bedload particles was based on the particle amount deposited at different positions of the pipe. The deposition distribution function in the pipe could be fitted, and it was an exponential function with e as the base, that could be used to calculate the scouring amount and scouring rate. The scouring rate calculated by the two models showed the following regularity:the suspended particles were scoured into a suspended state, and then part of them were deposited again during the migration process with water, so the scouring rate of suspended particles decreased gradually from the front section to the middle and back section of the pipe. For example, with an initial deposition quality of 100 g and a particle size of 0.045 mm, at an scouring flow rate of 0.30 m·s-1, the scouring rate at the front section of the pipe was calculated to be 78.94%, and finally it dropped to 13.89% at the back section of the pipe. For the two particles, the smaller the particle size, the greater the scouring velocity, the less the initial deposition quality and the higher the scouring rate.
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Key words:
- drainage pipe /
- suspended particles /
- bedload particles /
- calculation model /
- scouring rate
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