摘要: |
Tests were conducted on a 1:25-scale model of the Walter Bouldin Lock, located at the southern end of the Coosa River, and on a 1:15-scale model of the lock culvert valve that will be used on a series of five locks proposed for the Coosa River Waterway.
The lock model was built to study the filling and emptying system, which consisted of a bottom longitudinal flood culvert system. Culverts in each lock wall are connected to a crossover culvert with a horizontal splitter wall dividing flow to upstream and downstream tuning forks where equal divisions lead into the two longitudinal floor culverts in each end of the lock chamber. With the type 22 (recommended) design and a 1-mln valve opening time, the lock chamber filled In IS.5 min and emptied in 17.2 min. Due to differences in
friction losses, the prototype can be expected to fill and empty about 18 percent faster than the model (12.7 min and 14.1 min, respectively). The unsymmetrical baffling around the floor culvert manifolds was the key to energy dissipation and control that resulted in fast filling times and low hawser forces and only minor movement of a full tow with this high-lift system. The filling and emptying system developed is particularly desirable for high-lift locks in that it is insensitive to misoperation; that is, dangerous surges in the lock chamber cannot be created by fast operation of the valves, nonsynchronous operation of the valves, or intermittent stopping of the valves during the opening cycle.
The reverse tainter valve(s) that controls the flow entering and leaving ail the locks proposed for the Coosa River Waterway is considered a vertically framed valve because the 18-ln.-deep T-beams separate the skin plate from the main horizontal girders. This provided a 12-in.-deep passage for flow circulation between the upstream face of the skin plate and the girders. The average horizontal and vertical forces exerted on the trunnions ranged up to 1,500 kips and 580 kips, respectively, with a lift of 130 ft. These loads were expected with this very high lift. However, the magnitudes and frequencies of forces exerted on the hoist mechanism were determined to be excessive. The average hydraulic forces reversed in direction from downpull to uplift between gate openings of 55 to 65 percent for the different designs tested with lifts up to 130 ft. Modifications to the valve were ineffective in significantly reducing the dynamic loads on the hoist mechanism. A significant change in the structural design concept may be in order for lock culvert valves subjected to lifts as high as 130 ft.
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