JPH0468408B2 - - Google Patents

Description

[Detailed Description of the Invention] <> Industrial Application Field The present invention relates to a structure such as a caisson that stores ballast water inside and is used so as not to be destroyed by freezing of the ballast water. This relates to structures in frozen waters.

＜＞ Conventional technology Marine structures, etc. in the sea area of cold regions are prone to freezing of ballast water inside structures such as caissons, destruction of the structures due to expansion of ice, and other harmful stresses that may cause damage to the structures. may work.

Conventionally, in order to avoid the effects of freezing of internal ballast water on structures, the ballast water inside the structure was heated to avoid freezing.

<> Problems to be solved by the present invention Conventionally, in order to avoid freezing of ballast water in structures, a method of heating ballast water has been used, but in icy areas of cold regions, ballast water is heated to a constant temperature. It takes a huge amount of money to keep it that way.

Furthermore, maintenance work on the structures themselves, heating devices, etc. in cold regions is extremely difficult.

The present invention was made in view of the above points, and an object of the present invention is to provide a structure in a frozen water area that is not affected by freezing of ballast water.

<> Means for Solving the Problems The present invention provides a space above the expected water surface position of the ballast water inside the structure, and a taper that extends upward from the expected water surface position to the wall surface above the expected water surface position. By providing an inclined surface and forming the wall surface below the inclined surface to be thinner than the lowest part of the inclined surface,
The structure was designed so that it would not be affected by freezing of ballast water.

<> Example Next, an example of the present invention will be described based on the drawings.

The structure in a frozen water area according to the present invention is a structure 1 having a hollow portion into which ballast water W is put.

(b) Structure Structure 1 is a hollow box made of concrete or steel, or a cylindrical tank.

The interior height is such that a space can be left at the top and the ballast water W can be poured into the interior. (1st
(Figure) In addition, the inner wall above the vicinity of the water surface of the ballast water W to be injected (the height at which freezing is expected) is sloped so as to widen toward the top, forming an inclined surface 11.

The lower wall surface of the inclined surface 11 is formed to be thinner than the lowest part of the inclined surface 11, and the inclined surface 1
1. An inclined protrusion 13 is provided at the lower part of the structure.

It is also conceivable that the inside of the structure 1 is divided into a plurality of parts by partition walls.

However, in this case as well, the upper part of the inner wall of each partitioned room must be sloped in the same way as above.

Next, the functions and effects when using the above structure in frozen waters will be explained.

(a) Actions and effects provided on the inclined surface (Figures 2 and 3)
As described above, the structure 1 has an inclined surface 11 formed by slanting the inner wall above the vicinity of the water surface of the injected ballast water W (the height at which freezing is expected).

In general, it is thought that in structures in icy areas, the force exerted by frozen ice floes makes the inner walls vertical.

Therefore, in addition to destruction due to internal pressure under the ice floe, localized loads due to expansion of the ice itself are considered.

The structure of the structure 1 used in the present invention is designed to prevent internal pressure and local loads within the structure.

That is, as shown in FIG. 2, when an ice floe forms near the surface of the ballast water W as expected, a force F and an internal pressure P are generated that act perpendicularly to the inner wall of the structure 1.

However, the inner wall of the structure 1 above the water surface of the ballast water W (the height at which freezing is expected) is tapered to form a sloped surface 11 that is open at the top, so the inclination angle of the sloped surface 11 is This causes the ice floe to slide upwards.

Therefore, stress acting on the walls of the structure 1 can be prevented.

Furthermore, as the ice floe lifts upward, the internal pressure P under the ice wall is also relaxed.

Then, an inclined protrusion 13 is provided at the lower part of the inclined surface 11.
will be established.

Therefore, the side wall 12 is not made thicker than necessary;
A slope 1 with a sufficient slope necessary to prevent the above-mentioned ice wall from freezing without unnecessarily increasing the weight of the structure.
1 can be obtained.

(b) Specific example Next, we will discuss the inclination angle of the inclined surface 11 using a specific example.

The target is a concrete caisson with a length and width of 400 cm and a wall thickness of 40 cm, which will be used at an outside temperature (winter average) of -30°C.

Since the freezing strength t of the ice and the concrete whose surface is coated is 0.2 (Kg/cm ² ), the thickness H of the ice is: H = 0.3 x (t x | -30℃ | x 24) = 0.375 t(cm)...
…(1) becomes.

Furthermore, the internal pressure P in the caisson is P=1/240×t (Kg/cm ² )...(2) For the ice floe to float, the internal pressure P must be greater than the freezing force T that freezes on the wall of the structure. is one of the conditions.

Therefore, assuming that T≦P, this inclined surface 11
Let's calculate the angle of

If the angle of inclination between the vertical plane and the inclined plane of the side wall 12 of the structure 1 is θ, the freezing force T is as follows: T=H/cosθ×4×l×t=0.375/cosθ×400×4×0.2×t=120 ×t/cosθ...(3)

Moreover, the internal pressure F is F=l ² ×1/240×t×cosθ=400 ² /240×t×cosθ (4).

(l is the horizontal length of the caisson) Since T≦P is assumed, 120×t/cosθ≦400 ² /240×t×cosθ 0.18≦cos ² θ ……(5) ∴θ≦64 …… (6) From the above calculations, the angle of inclination in relation to the freezing force is smaller than 64 degrees.

On the other hand, the force F exerted by the ice floe horizontally compressing structure 1
The conditions for an ice floe to slide when the force exceeds the static friction force are as follows.

F・sinθ≧μ・cosθ……(7) (Here μ is the coefficient of static friction 0.6.) Therefore, the angle θ of the inclined surface is ∴tanθ≧0.6 θ≧31 …(8) becomes.

From the above equations (6) and (8), the side wall 12 of structure 1
The preferred angle of inclination between the vertical plane and the inclined plane is 31≦θ≦64.

Suppose that the inclined protruding portion 13 is not provided at the lower part of the inclined surface 11 and a side wall 12 is provided that continues vertically from the lowest part of the inclined surface 11 as shown in FIG. The structure becomes very thick and the weight of the structure increases, making it difficult to install the structure.

Therefore, by providing the inclined protrusion 13, the side wall 12 can be formed to have an appropriate thickness, and the weight of the structure will not be increased unnecessarily.

(c) Structure providing space at the top Seawater is injected into the structure 1 as ballast water W, and the structure 1 is configured to have an internal height that can secure a certain space A at the top.
(Figure 1) Generally, when ballast water is injected into the entire internal space of a structure such as a caisson, the internal pressure increases due to freezing of the ballast water, causing internal volumetric expansion and stress to the structure.

Therefore, in the structure of the present invention, the internal height of the structure is determined in advance so that a space A corresponding to the volume expansion due to freezing is secured within the structure 1.

Here, we specifically show the internal pressure due to coagulation of seawater, etc.

The internal pressure due to solidification of seawater is calculated to be 30 kg/cm ² in a 12 x 15 x 17 m concrete caisson over a period of about 100 hours at -20°C.

In addition, a steel circular tank (L = 90cm, R = 70cm,
t=0.5), assuming -30℃ and 10 hours, 45
A pressure of Kg/cm ² is calculated.

Here, the coefficient of volumetric expansion due to solidification of seawater is 1.084
Considering this, if seawater is injected as ballast water, even if all the seawater freezes, the volume will only increase by a little less than 10%.

Therefore, increase the internal volume of structure 1 by 10%,
Alternatively, by injecting only 90% of the ballast water W (seawater), the influence on the structure due to volumetric expansion of seawater can be prevented.

In fact, in the case of the circular tank mentioned above, it has been confirmed through experiments that if a space is secured at the top, the internal pressure can be reduced to a value less than 1 kg/cm ² .

(iv) Other Examples (Figure 4) It has been confirmed that, generally, when seawater freezes, the seawater below the ice floe permeates and seeps out onto the ice floe.

It is believed that the same phenomenon occurs in the frozen water structure of the present invention, which reduces the internal pressure within the structure.

Therefore, it is possible to increase the salt concentration of the ballast water W by introducing rock salt or the like into the ballast water W, thereby increasing the water permeability of the ice floe.

It is also conceivable to install a heating pipe P in order to more actively reduce the internal pressure under the ice floe.

That is, as shown in FIG. 5, a heating pipe P having a built-in heating coil etc. is installed inside the structure 1, and surrounding ballast water W
By heating the ballast water W, the ballast water W is drained onto the ice floe I, and the internal pressure below the ice floe I is reduced.

The purpose of heating here is not to prevent the ballast water W from freezing, but rather to reduce the internal pressure under the ice floe, so the cost of heating can be kept much lower than the overall heating cost. I can do it.

Note that even when the inside of the structure 1 is divided into a plurality of tanks by a partition wall or the like, the water pressure of the ballast water is configured to be common to all the tanks by, for example, opening windows in the partition wall or the like.

<> Effects of the Invention Since the present invention has been described above, the following effects can be expected.

(b) The internal height was set to provide a certain amount of space at the top of the structure, and the top of the structure was widened by tapering the inner wall of the structure at the expected freezing height.

Therefore, even if the internal pressure within the structure or the expansion of the ice floe occurs, the ice floe will move upward, so the structure is designed so that it will not be affected by the freezing of ballast water.

Therefore, there is no need to prevent freezing, and there is no need to heat the entire ballast water, resulting in significant cost savings.

(b) An inclined protrusion was provided on the side wall of the structure to form an inclined surface.

Therefore, even when the angle of inclination of the inclined surface with respect to the vertical direction is large, the side wall below the inclined surface does not become thicker, and the side wall can be provided with an appropriate wall thickness.

Therefore, the structure can be constructed without unnecessarily increasing the weight of the structure.

[Brief explanation of the drawing]

Figure 1: Perspective view of the structure of the present invention, Figure 2: Illustration of ice floe sliding on an inclined surface, Figure 3: Illustration of slope angle and wall thickness of side walls, Figure 4: Other implementations. An explanatory diagram of an example. 1: Structure, 11: Slope.

Claims (1)

[Scope of Claims] 1. A space is provided above the predicted water surface position of the ballast water to be accommodated, a protrusion is provided on the inner surface of the side wall, and the protrusion has a tapered slope that widens from below to above. A structure in a frozen body of water, characterized in that the structure is configured to form a surface, and the predicted water surface position is located between an upper end and a lower end of the slope.