Hydro-Power Stations: 4 Facts You Shouldn’t Miss

This is a case study for the performance of the Jilebrak Hydro-power station in Xinjiang Uighur Autonomous Region.

Q1: Why knowing the Hydro-Power Stations is important ?

1. If you also have a Hydro-Power Stations to build in the high latitude like the Haba River, you may also confront the same problems as follows.

√ Haba River Hydro-Power Overviews：

The Haba River Basin is located between 86℃~87℃ east longitude and 48°-49° north latitude.

It is the second largest Hydro-Power Station of the Erzis River.

The total length of the mainstream is 214.1km, the basin area is 7224 km²,  the natural drop is 2155m.

The annual average flow rate of the Haba River is 68.39m³/s, and the annual average runoff is 21.58×108m³.

2. If you also have to build Hydro-Power Stations with the same flood standard of 100 years.

The flood standard of  the Hydro-Power Stations design is once in 100 years, and the flood peak flow rate is 1188m³/s. The verified flood standard is once in 2000, and the flood peak flow rate is 2165 m³/s.

3. If you also have a Stations to be built in Seismic-prone areas.

The peak seismic acceleration in the engineering area is 0.05g, and the characteristic period of the seismic dynamic response spectrum is 0.4 s.

4. If your Hydro-Power Stations also locates in areas with complex geological conditions

The geological conditions of the station is quartz porphyry and oblique granite, weathering strata, which are exposed in the dam site area.

The Hydro-Power Stations site area is in the Crandi trough fold belt in the western section of the Altai fold system.

The two sides of the station site are steep, and the inverted piles of rock collapse form at the foot of the bank slope in the dam area continue to develop upstream and downstream on the shoulder of the left dam, with a thickness of about 3-8 meters.

The left bank is fine-grained oblique granite and hard rock. There are fewer cracks and more complete rock mass, most of which are massive structures.

The height of the right bank slope is 195m, and the natural slope is 35°~42°. It is a natural gentle slope and stable.

On the right bank is quartz porphyry, medium-hard rock. There are more cracks, more small structures, and small faults in the rock mass, most of which are mosaic fracture structures.

The right bedrock has a weathered layer with a thickness of 6-15m. Most of them are muddy lithotripsy, with a soft structure and poor properties.

The fractures in the rock mass interrupt layer is developed, compressive torsion, and slight staggers can be seen at the intersection.

Q2: What are the components of the hydro-power station?

Diversion tunnel

The maximum discharge of the diversion tunnel is 797.2m³/s. The gate hole between the hydro-power station and the tunnel is 6m×8m. The total length is 434.3m. The utilization section length is 556.7m.

Deep-hole spillway hole

Deep-hole spillway tunnel: design discharge 579m³/s, check discharge 614m³/s, Chengmen tunnel type 4.5m×7.5m, 6m×8m. The hole has a length of 510m.

The main factory building

The main factory building is 64.7×21.0×44.7m. A total of four hydroelectric generator sets are arranged in the main engine room. ( 2×30MW+2×50MW)

Hydro-Power Stations generation hole

One hole and four machines in the power generation hole, with a water diversion flow rate of 162.0m³/s, a hole diameter of 8.0~6.2m, and a whole length of 396m.

Surface hole spillway hole

Surface hole spillway hole design discharge 776m³/s, check discharge 1080m3/s, Chengmen cave type 8m×10m, full length 331m.

Concrete slab rock-fill dam

Concrete slab rock-fill dam top elevation 756.3m, dam length 446.0m, maximum dam height 140.3m. The upper slope is 1:1.5, and the downstream average dam slope is 1:1.7.

The top elevation of the cofferdam

The top elevation of the cofferdam in the upper reaches is 676.0m.

Q3: What are the designed structures of the panel dam for a hydro-power station?

Structural design of dam top

The top of the dam adopts a fiber-mixed concrete pavement. The upstream side is equipped with an “L” reinforced concrete mixed polypropylene fiber wave-proof wall. Set up a settlement joint at the bottom of the wave-proof wall and the panel and an expansion joint every 12m along the wall. The wall is staggered with the panel. The seam is wrapped with water-stopping materials.

The slope of the upstream dam is 1:1.5, and the slope of the downstream dam is 1:1.3. The downstream slope is equipped with a zigzag highway. Polypropylene fiber concrete is used on highways. The downstream dam slope protection adopts large stones to be adjusted and packed by manual in cooperation with machinery. The diameter of the stone is 0.50~0.80m.

Polypropylene fiber concrete panel design

Thickness: The top thickness of the panel is 0.3m. The bottom thickness of the fiber-concrete panel is 0.75m

Width: The width of the panel of the pressure area of the riverbed is 12m (24 pieces). The width of the pull area panel of the slope is 6m (14 pieces on the left bank and 10 pieces on the right bank).

Design of polypropylene fiber concrete toe plate

We adopt a horizontal toe plate. A layer of bidirectional concrete embedded steel bar is arranged 15cm from the top surface of the toe plate, with a steel content of 0.4%.

Anchor bars are arranged in the toe plate to anchor the toe plate on the bedrock.

Polypropylene fiber panel seam and waterproof design

The panel is sewn with two waterproof walls. The bottom copper sheet and the top filler stop water.

The surrounding D-seam three-story waterproof protective wall. In turn, GB packing, GB waterproof strip, and waterproof copper sheet. 25mm thick solid pine board filled with asphalt and fiber in the seam. Plastic cloth belts, asphalt fiber sand gaskets, and cushions are laid under the copper sheet in turn.

The permanent deformation joints are set up at the change of topography and geological conditions, the turn of the toe plate, and the middle of the long straight toe plate. The deformation joint is staggered with the panel joint. A copper sheet is set in the seam to stop water, and a closed structure is formed with the surrounding seam water stopper. The steel bars on both sides of the joint are broken.

The seam of the wave-proof wall and polyethylene fiber panel is equipped with a bottom copper waterproof sheet and a top flexible filler waterproof material.

Set up a deformation joint of the wave-proof wall every other 12 meters in the direction of the length of the wave-proof wall. Stagger deformation joint with the panel joint. Install a rubber water stopper in the seam. Fill the seam with asphalt polyethylene fiber sand-board. The seam adopts a width of 20mm.

Q4: What efforts have been made to strengthen hydro-power stations?

The following are the design highlights.

Anti-crack and waterproof

Polyethylene fiber concrete in contact with rocks is made of sulfate-resistant cement. The toe plate, consolidation grouting, curtain grouting, and fault polyethylene fiber concrete plugs of the panel dam are made of high sulfate resistance cement.

Corrosion-persistence

Block.

Ensure that the grouting entering the curtain can capture the strong oxidation zone of the rock mass. Curtain grout is made of cement that is resistant to sulfates. A row of epoxy resin-like chemical grouting is added to the middle of the grouting under the toe plate of the strong pyrite oxidation belt.

Separation.

Fault zones, joint dense zones, and parts with high pyrite content need to be deeply replaced. Spray a polyethylene emulsion mortar thicker than 3 cm on the base surface of the column and the outer surface of the column.

Resistance.

It adopts corrosion-resistant cement material and treats the contact surfaces of polypropylene fiber concrete and bedrock in various buildings with high sulphuric acid cement.

Row.

During the construction, drain the water at the bottom of the dam foundation and check the water quality.

Prevent frostbite

1. During construction, the panel concrete adopts a suitable concrete ratio, mixed with additives such as air initiators and polypropylene fibers. Improve the impermeability and frost resistance label of panel concrete. The indicators used in the design are C30, F300, and W12.

2. The surface of the panel is coated with elastic polyurethane so that the polypropylene fiber concrete panel has a certain anti-ice drawing ability.

3. Strengthen the rolling of the dam. No construction is carried out in winter. When the weather is warm, the dam surface is infiltrated with water to increase settlement during the construction period.

4. Increase the content of panel steel bars and polyethylene fibers. Add surface temperature bars in the water surface change area and above. Set up a double-layer two-way steel mesh. Increase the density of polypropylene fiber.

5. Improve the connection between surface waterproof belt and panel concrete. In the project, materials with strong bonding force are selected as the perfusion binder for expansion bolts. Provide more reliable anchorage. SK primer is poured into the anchor hole of the expansion bolt, and the expansion bolt is smoothed out of the nut part.

To Summarize

The rock-fill dam in Jilebrak Hydro-Power Stations is the highest dam with the highest latitude. It is a typical case. All the main piles of stones are blasting materials.

This project absorbs successful experience, combines topographic and geological conditions. The group considered the actual situation of the project in terms of dam zoning, seam water, panel frost resistance measures, etc. It will provide an immense reference for the design of similar projects in the future.