| Hydraulic performance of filter fabric and rockfill as well as their sediment trapping efficiency are studied in this research. The head-discharge relationship for filter fabric has been developed by first applying the Bernoulli equation to a single opening and then extending the principle to the entire cross-sectional area. An opening coefficient, which varies with hydraulic head, is introduced in the head-discharge equation. The derived filter fabric formula is linked with the orifice equation and the weir equation by this opening coefficient. A series of flume experiments were conducted to verify the developed equation and determine the coefficient of discharge. The same principles were used to develop the equation of flow through rockfill. Tests showed that flow rate was directly proportional to rock diameter and inversely proportional to the length of rockfill. The channel slope also had a slight influence on the flow. Two simplified methods are introduced to estimate the sediment trapping efficiency for rockfill and filter fabric. One is based on the variation of sediment transport capacity, while the other is based on the concept of the potential fall depth. |
