JPH033007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for excavating a water intake hole for intake of cold seawater from the deep sea in ocean thermodynamic power generation and the like.

Ocean temperature difference power generation works in the deep sea at a depth of about 600 meters.
They take in cold seawater at 7°C and warm seawater near the sea surface at 25-30°C, and use the temperature difference between them to generate electricity, and there are two types: land-based plants and offshore plants. In order to obtain a practically usable power generation amount using the above power generation method, it is necessary to take in a large amount of seawater. For example, to operate a 2500KW x 2 practical plant, warm seawater and cold seawater are
Approximately 50,000m ³ /H of water must be taken in. In this case, it is easy to construct warm seawater intake equipment near the sea surface, but there are various difficulties in creating equipment that can stably intake large amounts of cold seawater, especially in land-based plants.

In general, cold seawater intake equipment in land-based plants can be roughly divided into the pipeline method shown in FIG. 1 and the tunnel method shown in FIG. 2.

In the former case, pipe 1 is transported from land 2 to seabed 3 by floating towing method, submarine towing method, laying ship method, etc.
The water intake port 4 at the tip of the pipe is located on the seabed at a depth of about 600 m. However, the above pipeline method has the disadvantage of durability after installation, and the diameter of pipe 1 is large (for example, the above 2500KW
(For two units, 3mφ x 2 or 4.5mφ x 1) Various problems occur during construction, and they are also easily affected by weather and sea conditions such as waves and currents. In order to avoid this, if the diameter of the pipe 1 is reduced to increase the water intake flow rate, the head loss will increase, the energy used for pump equipment will increase, and the power transmission output will decrease.

In addition, in the latter tunnel method, the tunnel 5 that connects the land 2 and the deep sea is durable and unaffected by weather and sea conditions and can have a large hole diameter, and the vertical shaft 5a and horizontal shaft 5b can be constructed using normal blasting. Construction method, TBM,
It can be easily excavated by RCD etc. but,
Excavation near the water intake 6, which receives high water pressure of 60 kg/cm ² , is performed by a boring device 8 from the sea level 7, and the tunnel 5 is communicated with the deep sea.
This construction has several problems that must be solved in terms of safety and construction technology, and it is considered difficult to develop a practical plant that generates electricity by drawing in cold seawater through a tunnel from land.

In view of the above circumstances, it is an object of the present invention to provide a method for excavating a cold seawater intake hole that allows construction near the intake to be carried out safely and efficiently. We excavate a tunnel hole that reaches close to the bedrock surface that is in contact with deep sea water.
A chamber is constructed at the tip of the tunnel hole,
After drilling from inside this chamber toward the deep sea at a depth equal to or less than that of the chamber, and drilling a large number of water collection holes connecting the chamber and the deep sea with stop valves closed,
A method for excavating a seawater intake hole in the deep sea, characterized by opening the water collection hole.

The method of the present invention will be explained below with reference to the drawings.

3 to 5 are diagrams for explaining an example of the method of the present invention, in which reference numeral 11 denotes a vertical shaft 11a, a horizontal shaft 1
This is a tunnel hole made of 1b. Tunnel hole 11
The tip part 1 is constructed using the normal blasting method, TBM, and RCD.
Excavating so that 1c reaches near the bedrock surface 12 in the deep sea. A chamber 13 of a predetermined length is connected to this tip portion 11c so as to extend parallel to the deep-sea bedrock line 14 at the water depth a.

The tunnel hole 11 and chamber 13 are excavated to a safe point in the rock, so there is no danger of being exposed to a large amount of high-pressure seawater.

After the tunnel hole 11 and the chamber 13 are completed, a large number of water collection holes 15 are formed by boring from the inside of the chamber 13 toward the deep sea.
The above water collection hole 15... is usually 0.3mφ,
200 to 300 pipes are required to take in the seawater required for 5000KW of power generation. Water collection hole 15...
Boring is a well-known technology and has a proven track record in geothermal utilization, oil extraction, etc. Furthermore, since casing excavation is also possible, it is possible to deal with the collapse of water collection holes. Stop valves 16 are attached to these water collection holes 15, and are kept closed by the stop valves 16 until the boring of all the water collection holes is completed. After the construction of the water collection holes 15 is completed, water is injected into the tunnel hole 11 and the chamber 13 from the land area. After the water injection is completed, the valves 16 of the water collection holes 15 are opened by underwater blasting or remote control to communicate the deep sea with the tunnel holes 11.

Next, the operation of the excavation method according to the present invention will be explained.

The above-mentioned large number of water collection holes 15 according to the method of the present invention...
The force applied to water collection hole 1 is 62Kg/cm ² (assuming seawater specific gravity 1.03) when the water pressure is 600m.
If the diameter of 5 is 0.3m, 620t/m ² × (0.3) ² ×π/4
Therefore, it is approximately 44 tons, and water can be stopped using the valve 16. Moreover, even if the amount of water intake increases to accommodate a large amount of power generation, it is only necessary to increase the number of water collection holes 15 provided in the chamber 13.
Construction of the water intake section can be carried out without any difficulty. On the other hand, if water is taken from the entire cross section of the tunnel 5 as shown in Figure 2, the diameter of the water intake that corresponds to 5000KW of power generation will be 4.5m, and the force applied will be approximately 9900t, making construction impossible. Moreover, as the amount of power generated increases, the force due to water pressure increases further. Furthermore, in the present invention, after constructing the tunnel hole 11 and chamber 13 which can be safely constructed and are strong, a large number of thin water collection holes 15 are provided in the chamber 13 using proven technology.
Collapse, blockage, etc. of the water collection hole 15 can also be dealt with. In particular, if the valve 16 can be closed by remote control, various measures can be taken very easily. Also, water collection hole 1
5... opens tunnel 11, chamber 13
This is done after the water has been injected into the water, so there is no spouting of high-pressure seawater, there is no strain on the facility, and the safety is high.

As described above, since the method according to the present invention communicates with the deep sea through a large number of thin water collection holes provided in the chamber, each water collection hole can be closed with a valve, making it extremely safe. This is a method for drilling a cold seawater intake hole that enables the excavation of a water intake section and also allows easy measures against accidents at the water intake section due to collapse or blockage of the water collection hole.

In particular, according to the present invention, a plurality of water collection holes are bored from within the chamber, making this construction relatively easy.
It is possible to reduce construction costs, and since this boring work is performed inside a tunnel, it is possible to reduce weather, tides, and
It is hardly affected by waves and the like, so the boring work can be carried out accurately and according to plan. Furthermore, by boring from inside the chamber in this way, so-called horizontal boring can be performed, so the opening position of the water collection hole relative to the deep sea can be prevented from being located above the position of the chamber.
In addition to being able to secure a water depth equal to or greater than the depth of the shaft, the water collection hole can be opened directly into the bedrock surface in the deep sea without being affected by the shape of the bedrock surface. It has various excellent effects. Further, according to the present invention, boring is carried out from inside the chamber toward the deep sea at a depth equal to or lower than that of the chamber, so that the opening position of the water collection hole to the deep sea is not located above the position of the chamber. By doing so, it is possible to achieve the effect that there is no need to take special measures to prevent the inflow of drifting sand or the like into the chamber or tunnel hole.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of conventional cold seawater intake methods; Figure 1 is a diagram of the pipeline method;
Fig. 2 is a diagram of the tunnel system, and Figs. 3 to 5 are explanatory diagrams of the cold seawater intake method according to the present invention.
3 is a longitudinal sectional view of a water intake hole excavated by the method of the present invention, FIG. 4 is a perspective view of section A in FIG. 3, and FIG. 5 is an enlarged view of section A in FIG. 3. 2...Land, 3...Undersea, 7...Sea surface, 11...
...Tunnel hole, 12...Deep sea bedrock surface, 13...
Chamber, 14...Bedrock line, 15...Water collection hole,
16...Stop valve, a...Water depth (600m).

Claims (1)

[Claims] 1. A tunnel hole is excavated from land, the tip of which reaches close to the bedrock surface in contact with seawater in the deep sea, a chamber is constructed at the tip of the tunnel hole, and a tunnel with a depth equal to or less than that of the chamber is excavated from within this chamber. Drilling of a seawater intake hole in the deep sea, characterized in that the holes are bored into the deep sea, a large number of water collection holes connecting the chamber and the deep sea are closed with stop valves, and then the water collection holes are opened. Method.