Masters Degrees (Civil Engineering)

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Browsing Masters Degrees (Civil Engineering) by browse.metadata.advisor "Basson, GR"

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    Hydraulic evaluation of the automatic TOPS Gate mounted on a low crested weir
    (2022-11) Rae, John; Basson, GR; Bosman, DE; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Abstract This study provides an independent review Of a large automatic TOPS Gate, developed by AmanziFIow Projects. The hßraulic evaluation done by means Of a 1:20 physical model Of the prototype TOPS Gate, based on the Froude model scale laws. The prototy* gate was designed for a proposed Limpopo River abstraction works case study, consisting Of a 630 m long barrage spanning the large, sediment laden river. According to the case study requirements, the dimensions Of each gate and supporting piers (as one Of a series across the river) were 20 m Wide by 10 m high, to be installed on a 3 m high ogee weir, Which Will be the largest application Of the TOPS Gate to date. The model test results illustrated that the prototype Offered versatile water management capabilities, effectively maintaining a normal operating level Of 7.6 m above the ogee weir crest level (10.6 m deep above the bed), before and after floods. The maximum discharge capacity Of the TOPS Gate (Of the above referred size) was found to be 805 m"'s (unit discharge Of 40.25 rn3/s per metre length), While the siphon operated TOPS Gate was capable Of discharging floods in excess Of 984 rn3/s (unit discharge Of 49.2 rn3/s per metre length). NO negative pressure, fuctuations or vibrations were observed at the maximum discharge capacity Of the TOPS Gate. The prototype completely scoured sediment deposits Of hand packed coarse sand (DSO I .4 mm), Within the drawdown region. However, only local occurred with the coarse gravel deposits (DSO 24 mm). Furthermore, the model gate successfully passed floating debris Of length equal to the effective gate Width Of 17 m . Debris blockages that did occur were removed via opening the manual release valve enabling partial opening Of the gate to dislodged the debris. Additionally, the safety review Of the TOPS Gate concluded that the prototype opened appropriately, minimising the risk Of downstream flooding, by ensuring that the Outflow did not significantly exceed the inflow, i.e. the gate did not cause sudden or pulsed releases ahead Of a flood *ak- It was found that tailwater levels higher than 40% Of the upstream water depth significantly reduced the discharge capacity Of the TOPS Gate, Which resulted in overtopping. The problem could be overcome by adding more buoyancy on the downstream side Of the gate. However, tailwater levels less than 40% Of the maximum upstrearn water level, had little effect on the operation and discharge capacfty Of the TOPS Gate.