JPH0684611B2 - Method of discharging gravel in a reservoir - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for discharging gravel and bottom mud accumulated in a reservoir for hydroelectric power generation.

In the conventional dam, in order to prevent the abrasion of the water wheel and the penstock by the sediment, the surface flow of the reservoir is mainly flowed to the headrace, and the sediment is deposited in the reservoir. Therefore, the sediment gradually accumulates in the reservoir, the effective storage amount of which decreases, leading to the deterioration of various functions such as power generation capacity, flood control capacity and water resource holding capacity. It has caused various problems such as riverbed degradation and coastal retreat due to the sediment supply cutoff.

In addition, the remains of animals and plants and organic matter such as spoilage are also deposited at the bottom of the reservoir, and dissolved oxygen is insufficient at the bottom of the lake, so natural purification is not performed and the reservoir is eutrophic, causing, for example, malodorous tap water. It causes a lot of blue-green algae and is a problem as drinking water pollution.

If there is no water retention due to the above dams, organic matter such as sediments and remains of animals and plants and putrefaction will flow to the downstream, soils and gravel will be effectively used as construction materials, and organic matter will be purified naturally in a river rich in dissolved oxygen. Therefore, it can be used as an optimal organic fertilizer for agriculture and forestry, or as a nutrient source for plankton, which is a food for seafood.

(Prior art) Therefore, a sand removal gate was installed on the dam, a sand removal pipe was installed on the shore of the reservoir, and these valves were opened to flush the sand with water during a flood. There are some problems,
Not getting enough results. That is, a large amount of water is required to discharge sand by running water, and effective sand removal cannot be performed without flowing the water until the reservoir is emptied.

Therefore, in order to return the reservoir to its original full state, it is necessary to store water at the inflow during the flood attenuation period, so it is not possible to apply it to anything other than small and medium-sized reservoirs. In addition, this results in waste of the hydraulic power that can be used for power generation, and this method cannot be used for dams for water supply such as tap water and agricultural water.

(Problems to be Solved by the Invention) As described above, there is no effective method for discharging sediment in a reservoir, and therefore, the present invention proposes a novel method capable of reliably discharging sediment. The purpose is to

(Means for Solving the Problem) The inventor does not preferentially take in surface water as in the conventional method, but conversely preferentially uses sediment or gravel flowing into a reservoir as a pressure-type introduction pipe. It was found that the sediment can be surely discharged if it is made to flow in, and the present invention has been completed.

That is, the present invention guides running water containing sand and gravel to a main surge tank from a water pipe having an intake port at the bottom of the reservoir, while precipitating sand in the intake water at the bottom of the main surge tank.
Water is guided to the turbine for power generation via the penstock connected to the upper part of the main surge tank, and then to the water in the main surge tank and in the sub-surge tank communicating with the bottom of the main surge tank via the sand discharge pipe. It is characterized by applying pressure fluctuations during operation, fluctuations in generator load, and vibrations caused by water shocks at the start and stop of turbine operation, liquefying the sediment at the bottom of the main surge tank and pouring it into the sand discharge pipe. The method of draining gravel in the reservoir and the sieve installed in the middle of the main surge tank with an inclination to screen rocks from the intake water, and this sieve is vibrated by the vibration of the water in the main surge tanks. It is a method of discharging gravel in a reservoir characterized by leading to a rock discharge pipe connected to a main surge tank.

Next, the present invention will be described in detail with reference to FIG.

In the figure, 1 is a pressure type water conduit, and its intake 2 is installed at the bottom of a reservoir 3, preferably near the start of sedimentation (streamline of the river), as shown in FIG. The intake 2 is provided with a detachable fence 4 for removing driftwood and boulders that may clog the water conduit 1. The fence 4 has a structure that allows easy passage of earth and sand and gravel. Further, the water conduits laid in the lake bottom may be connected by flexible mechanical joints, and may be lined as described in Japanese Patent Application No. 63-135409. In this way, the intake position can be moved to a place with a large amount of sediment and the sediment can be effectively sucked. In addition, if it is desired to extend the intake further upstream, the intake will be pulled up to the shore so that extension pipes can be connected. Also, connect a number of perforated tubes suitable for sucking bottom mud. In this way, sediment and bottom mud are positively sucked and discharged without depositing.

Next, the water intake from the water conduit 1 is introduced into the main surge tank 7 installed upstream of the penstock 6 that guides the running water to the power generation turbine 5. Here, the sediment and gravel in the intake water are separated from the water.

That is, the gravel having a particle size of more than 10 mm is sieved by the sieve 8 in the main surge tank 7 and moved to the rock discharge pipe 9 connected to the main surge tank 7. A surge tank 10 and a sluice valve 11 are installed at the tip of the rock discharge pipe 9, and the rock is stored therein.

Gravel with a particle size of 10 mm or less passes through the sieve 8 and settles on the bottom of the main surge tank 7. The bottom of the main surge tank 7 communicates with the sub-surge tank 13 through the sand discharging pipe 12, and the sluice valve 14 is installed at the tip of the sand discharging pipe 12.

On the other hand, when the hydraulic power generation is started with running water guided from the penstock 6 to the power generation turbine 5, and the sluice valves 11 and 14 are closed during this operation, pulsation occurs and each surge tank 7,10
And the water level in 13 vibrates up and down.

The present invention is characterized in that the vibration is utilized to efficiently separate the gravel from the intake water, and the separated gravel is sent to a predetermined place.

First, the sieve 8 is fixed to the inner wall of the main surge tank 7 via the spring 15, and the vibration is also given to the sieve 8 by the above-mentioned vibration to roll the rock having a grain size of 10 mm or more on the sieve 8.
The rock is surely sent to the rock discharge pipe 9.

On the other hand, gravel with a particle size of 10 mm or less passes through the sieve 8 without causing clogging of the sieve 8 and settles on the bottom of the main surge tank 7.

The pulsation that occurs during operation of the water turbine described above is
The water surfaces of and 13 are vibrated up and down to increase or decrease the capacity of the upper spaces 7a, 10a and 13a. Then, the sub surge tank 13
The water in the sand discharge pipe 12 flows back and forth with a capacity equal to the increase / decrease of the space 13a, and the vibration of this water liquefies the sand that has settled at the bottom of the main surge tank 7, so that the sand discharge pipe 12 is horizontal. Even so, it flows along its inner wall as if it were a liquid. At the bottom of the main surge tank 7, the boundary between the settling sand 16 and the settling sand 17 becomes horizontal, and this horizontal surface rises with the increase in the settling sand. When the horizontal surface reaches just below the sieve 8, the sluice valve 14 is opened and the settling sand 16 To release. Further, since the sand discharging pipe 12 can function as a spillway, when a flood is expected and it is necessary to lower the dam water level, the sluice valve 14 is opened to discharge sand together with sand.

Since the gravel with a particle size of 10 mm or more is difficult to liquefy, the rock discharge pipe 9 must have a larger gradient than the sand discharge pipe 12, but the fluid inside the pipe corresponding to the increase or decrease of the space 10a of the surge tank 10 must be corrected. There is repeated flow in the opposite direction, which aids in the rolling or sliding of the rock, allowing it to roll at a smaller gradient compared to the absence of this repeated flow.

Then, the rock may be filled in the rock discharge pipe 9, or the sluice valve 11 may be opened to discharge the rock when the dam water level is adjusted during a flood.

(Operation) In the present invention, the pulsation generated during the operation of the water turbine for power generation is utilized, and the pulsation occurs due to the following (1) to (3).

Note (1) The running water collides with the runner of the running turbine, and the reaction force causes a pressure fluctuation.

(2) Pressure fluctuations occur due to the vortex flow in the central part of the water turbine draft pipe.

(3) Pressure fluctuations due to fluctuations in the load of hydropower generation and water impact (water hammer) at the start and stop of power generation.

The pulsation peculiar to this penstock causes the water in the sand discharge pipe to vibrate, and the sand between the bottom of the main surge tank and the inside of the sand discharge pipe is liquefied to perform advantageous sand discharge.

Here, liquefaction of sand means that excessive shear water pressure accumulates between sand particles when a shearing force whose direction is reversed many times in a non-drained state is accumulated, and the decrease in shear resistance between sand particles asymptotically approaches zero. A phenomenon that takes on the characteristics of a liquid.

The particle size of gravel that tends to cause liquefaction has an average particle size D ₅₀ of 0.075.
It is said that the uniformity coefficient is less than 10 at ~ 2.0 mm. Therefore, to make the maximum particle size 5 to 10 mm, open the sieve with 9.
It is suitable to be 5 mm or less. If gravel with a particle size of 10 mm or more is mixed in the settling sand, the liquefaction will be hindered as the mixing ratio increases, so sieving by sieving is necessary.

When this invention is carried out, abrasion of the inner surfaces of pipes such as water pipes, sand discharge pipes, and rock discharge pipes becomes a problem, but the inventor first applied the inner surface of these pipes to Japanese Patent Application No. 63-135409. Lining with the "line pipe provided with a laminated lining including an adhesive layer and its construction method" proposed in the specification of the specification is advantageous because it can expect the following effects in addition to solving this problem.

That is, (i) the service life of each tube can be extended semipermanently (maintenance-free).

(Ii) If the lining becomes worn, only the lining tube can be replaced in a short time.

(Iii) If the water pipes laid on the bottom of the lake are connected by a flexible mechanical joint and lined, the dam lake can be replaced in a short time without emptying it if the lining tube is worn. This is because the intake tube can be pulled up to the shore of the lake, and after draining, the abrasion tube can be pulled out and the new chives can be run.

(Iv) When soft rubber is used for the lining layer, the liquid-impregnated reinforcing cloth layer and the lining layer interposed between the rubber layer and the pipe vibrate due to the force of water, and the gravel on the surface Facilitates flow, sliding or rolling.

(V) Each layer of the above lining has a function of relieving an impulsive pulse pressure applied to the tube wall.

(Effects of the Invention) According to the present invention, the sediment and gravel flowing into the reservoir are preferentially guided into the water conduit, and the dam's three functions (power generation, water utilization, flood control) are not easily reduced and discharged easily. Therefore, various problems caused by dam sedimentation can be solved. If the bottom mud is also discharged, the remains of the flora and fauna flowing down the river and organic matter such as spoilage will be discharged downstream without being blocked by the dam lake, thus solving the problem of eutrophication in the dam lake. At the bottom of the lake where dissolved oxygen is deficient, anaerobic bacteria generate gas that gives off foul odors such as hydrogen sulfide and mercaptans, and they turn into water and become dead lakes. Fermentation, carbon in the organic matter becomes carbon dioxide gas and escapes to the atmosphere, and hydrogen becomes water. Nitrogen and phosphorus can be important plant nutrients such as nitrates and phosphates.

Also, with conventional technology, the gravel as it is deposited on the dam can be sent to the gravel collection site far downstream from the hydroelectric power plant by using the potential energy of the gravel with almost no power. These can be effectively used as construction materials.

[Brief description of drawings]

FIG. 1 is a schematic diagram near the upstream of a penstock for explaining the sand removal method, and FIG. 2 is a sectional view of a reservoir showing the arrangement of water conduits. 1 ... Water pipe, 2 ... Intake port, 3 ... Reservoir, 4 ... Fence, 5 ... Power turbine, 6 ... Hydraulic iron pipe, 7 ... Main surge tank, 8 ... Sieve, 9 ... Rock discharge pipe, 10 …… Surge tank 11,14 …… Silver valve, 12 …… Sand drainage pipe 13 …… Secondary surge tank, 15 …… Spring 16 …… Sand settling, 17 …… Standing water

Claims (2)

[Claims] 1. From a water conduit with an intake at the bottom of the reservoir,
The running water containing gravel is guided to the main surge tank, and the sand in the intake water is allowed to settle at the bottom of this main surge tank, while the intake water is introduced to the turbine for power generation via the penstock connected to the top of the main surge tank, and then the main Water in the surge tank and in the sub-surge tank that communicates with the bottom of the main surge tank through the sand removal pipe, pressure fluctuations during turbine operation, generator load fluctuations, and water shocks when starting and stopping the turbine operation. A method for discharging gravel in a reservoir, which is characterized by applying the resulting vibration to liquefy the settled sand at the bottom of the main surge tank and pour it into a sand discharge pipe. 2. The method according to claim 1, further comprising sieving rocks from the water intake with a sieve installed at an intermediate portion of the main surge tank, and the sieve is shaken by the vibration of water in the main surge tank. A method for discharging gravel in a reservoir, characterized by vibrating and guiding rock to a rock discharge pipe connected to a main surge tank.