« PreviousContinue »
H = 0.6AP + W where
A = are a of gate leaf, at outside edges of gate seats,
P = water pressure at centerline of gate, and
W = weight of moving parts (gate leaf, stem, piston, etc.).
D. Canal Outlet Works
25. General. - The outlet works for the Meeker Irrigation Canal is located at the right abutment of the dam and passes under the dam embankment from the upstream edge to the downstream edge on a centerline normal to the dam (fig. 18). A drop inlet carries the water to a conduit founded on a shale formation at about elevation 2670. The conduit passes under a dam section to a stilling well which dissipates the energy of the flowing water and raises it to the level of the irrigation canal. The drop-inlet intake structure, constructed of reinforced concrete, is provided with four openings on the vertical sides and one opening on the top of the structure, each protected with a metal trashrack (sec. 26). The vertical portion of the structure is connected by means of a vertical bend to a 5. 5-foot-diameter horizontal pressure conduit 208 feet long having an invert elevation of 2671.0.
The pressure conduit extends from the intake structure, station 2+60, to the emergency gate chamber, station 4+68, and was constructed in sections each of which is provided with a cutoff collar. The gate chamber houses a 4- by 4-foot high-pressure, hydraulically operated emergency slide gate. An 8-foot 2-inch diameter horseshoe conduit, extending from the emergency gate chamber to the control house at the downstream edge of the embankment, accommodates a 56-inch inside-diameter steel pipe and a walkway which provides access to the gate chamber. The 56-inch steel pipe terminates at the control house with a 4- by 4-foot high-pressure, hydraulically operated control slide gate. In addition to housing the control gate and providing access, the control house at the downstream end of the conduit houses ventilating equipment, sump pump, and gate hoists . Water released through the outlet works flows through the regulating gate into a side-entry stilling well which discharges into the canal. The stilling well is a vertical shaft of octagonal shape with a discharge lip at elevation 2700.00. With the canal water surface at elevation 2705.0, the canal outlet works is designed to discharge 300 secondfeet when the reservoir water surface is at elevation 2720.0 and 690 second-feet when the water surface is at elevation 2773.0 (top of flood control pool). Discharge curves are shown on figure 19 .
Design criteria used in the design of various canal outlet works structures are given in appendix F.
26. Intake Structure. - The intake structure is a drop inlet of reinforced concrete design with the lip of the inlet located at dead storage level, elevation 2710.00. A box-shaped trashrack structure built monolithically with the drop inlet has four 7.5- by 7.5-foot openings on the vertical sides of the structure and one 7.5- by 7.66-foot horizontal opening on the top. These openings are provided with metal trashracks. The vertical shaft of the intake structure is about 28 feet long and has a bellmouth entrance. This shaft connects by means of a 6-foot-radius 90° bend to a 5.5-foot-diameter pressure conduit.
(a) Loadings.— In the design of the intake structure the following loadings were considered:
(1) Water load equal to 40 feet of differential head on the trashracks.
(2) Saturated earth fill load.
(3) Dead load of the concrete.
(4) Water load inside the shaft.
(b) Design Considerations.— Since the intake structure is uniformly backfilled to elevation 2706.0, there are no appreciable forces acting on the intake structure to produce sliding or overturning. For conditions of uneven settlement, the base pressure