JPH0444511A - Construction of breakwater - Google Patents

Abstract

PURPOSE:To reduce cost by mounting a caisson on a mound formed on the ground of the seabed, and placing a culvert structural body between the mound and the ground of the seabed to miniaturize the caisson. CONSTITUTION:A mound 2 is constructed on the ground l of the seabed, and a box culvert 10 is placed thereon. The box culvert 10 is launched from a floating dock or a quaywall after the manufacture, and it is conveyed upward of the mound 2 to place it thereon. After that, a caisson 3 is floated on the sea in a state of the empties, it is towed upward to the box culvert 10 by a ship, sea-water is poured into a room 3a of the caisson 3 to sink it into the water, and it is placed on the box culvert 10. The room 3a of the caisson 3 is filled with sand and gravel, and concrete is placed on the upper part of them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a breakwater structure built in a harbor to prevent waves from the open sea and maintain calm inside the harbor.

[Conventional technology]

The conventional breakwater structure is shown in Figure 4.

That is, in the same figure, the code °1 is the ground on the ocean floor,
A mound 2 is formed on this ground 1 so as to rise from the ground 1. Mound 2 weighs from several 10 kg to several 1 kg
It is made by piling up stones weighing about 1,000 kg on top of the ground 1, and is made by divers diving into the sea. A caisson 3 is placed on top of the mound 2 made in this way, and when viewed from above, the caisson 3 is formed into a box having several compartments 3a, as shown in FIG. At the same time, the lower part thereof is closed by a bottom part 3b as shown in FIG.

Although there are various methods for installing such a caisson 3, a strategic method will be explained below. First, Caisson 3 is floated in the sea in an empty state and is towed by a boat to the upper part of Mound 2. Then, by pouring seawater into the chamber 3a of the caisson 3, it is gradually submerged into the sea, and is positioned and installed on top of the mound 2. After filling with stones, concrete 4 is poured to a predetermined thickness d on top.

In this way, the breakwater is completed.

[Problem to be solved by the invention]

However, in the conventional breakwater mentioned above, its cross section is appropriately designed to balance the mound 2 and caisson 3, but when the sea depth is large, it is necessary to prevent slipping, overturning, etc. and to stabilize it. Therefore, caisson 3 must be large; for example, the depth from sea level 6 to seabed ground 1 is approximately 25 m, and the target offshore wave height is 8.50 m.
, if its period is 12.5 seconds, one caisson 3
The weight of 6.030 tons, the amount of sand etc. packed into it is 9,160 m', the amount of upper concrete 4 is 99.0
It will not be stable unless it is around m'/m.

As the caisson 3 increases in size as described above, it becomes difficult to manufacture and install the caisson 3, as well as to construct the mound 2, and the cost increases significantly.

In addition, in places where the ground on the seabed is weak, it is necessary to dig deep and replace it with good quality soil, or to improve the ground by injecting cement milk, which further increases costs.

Furthermore, since the caisson 3 is a solid structure filled with sand etc. inside, the oil side of the seawater 7 (arrow At) It> and the land 1IIl
(Arrow B side) and seawater 7 is completely cut off from the oil side.
and that of the gap cannot come and go or exchange with each other. For this reason, the seawater 7 remains in the harbor from the caisson 3 and tends to become dirty, and it takes a long time to purify the seawater, resulting in bad results for fisheries, the environment, and the like.

Therefore, the present invention aims to solve such problems.

[Means to solve the problem]

In order to solve the above problems, the present invention consists of a mound formed on the seabed, a caisson placed above the mound and filled with sand, etc., and a waterway placed between the mound and the caisson. The structure includes a formed culvert structure.

[For production]

According to this breakwater structure, waves on the sea surface are blocked by hitting the caisson, which is filled with sand, etc.
It is possible to prevent waves from directly entering the port and maintain calm in the port. Furthermore, since a culvert structure is placed between the caisson and the mound, the size of the caisson can be significantly reduced compared to conventional ones.

In other words, it has the same effect as if the mound were raised by the height of the culvert structure, and a channel is formed in the culvert structure, allowing seawater on the seabed to pass from the oil side to the gap, which prevents conventional wave waves. This is because the lift force of the caisson during a collision can be reduced to a negligible level. Therefore, by making the caisson smaller, its manufacturing and installation methods become easier than before, and costs can be reduced.

Furthermore, by arranging the culvert structure between the caisson and the mound, it is advantageous in terms of ground bearing capacity.

In other words, in the past, when a horizontal force was applied to a caisson due to waves, the weight of the caisson was biased to one side and applied to the mound, so the mound and the ground needed to have sufficient supporting force to support it. The pressure is reduced, and even if the weight of the caisson shifts to one side, it is the culvert structure that receives it, so the mound or ground that supports the culvert structure has a structure that does not shift to one side. Only the distributional load is applied. Therefore, the load on the ground can be reduced accordingly, and even in places where the ground is relatively weak, it is not necessary to improve the ground, or the extent of the improvement can be reduced.

Furthermore, since the culvert structure is formed with a waterway, the oil side and the seawater in the gap can communicate with each other and can be exchanged. Therefore, the seawater in the port is constantly exchanged with the seawater on the oil side and kept fresh, which can bring about favorable results in terms of fisheries and the environment.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1 to 3 are diagrams showing one embodiment of a breakwater structure according to the present invention. Note that the same reference numerals will be given to the same parts as in the prior art and the detailed explanation will be omitted.

In Figure 1, a mound 2 is formed on the ground 1 on the seabed, and a box culvert 10 is placed on top of this mound 2.
(Culvert treetop body) is installed, and furthermore, a caisson 3 is installed on top of this box culvert 10.

The caisson 3 has the same structure as the conventional one, and is similar to the conventional one in that the chamber 3a is filled with sand or the like, and concrete 4 is poured at the top with a predetermined thickness d.

The box culvert 10 is formed by dividing several waterways 12 into several waterways 12 by several support plates 10c arranged in the vertical direction, as shown in FIG.
c provides strength that can reliably support the caisson 3 on the box culvert 10. As shown in FIG. 3, the oil side of the box culvert 10 (arrow A11
ll) The thickness of the top plate 10a between the length Ll from the end,
The thickness of the top plate 10b between the length L2 (of the gap (arrow B side)) of the partition is thicker.

In such a breakwater structure, first, a mound 2 is created on the ground 1 on the seabed, and a box culvert 10 is installed on top of the mound 2. After manufacturing, this box culvert 10 is launched from a floating dock or quay, transported to the top of the mound 2 by a floating crane or a special ship, and installed on the mound 2.Then, the caisson 3 is floated in the sea in an empty state. (It floats because of the bottom part 3b), is towed and transported by a ship to the top of the box culvert 10, then seawater is poured into the chamber 3a of the caisson 3 to gradually sink it into the sea, and it is positioned on top of the box culvert 10. Crotch! 6. Next, the chamber 3a of the caisson 3 is filled with sand and gravel, and finally, concrete 4 is poured on top to complete the breakwater structure. In addition, the broken line in FIG. 1 shows the outline of the conventional caisson 3, and is shown in comparison with the size of the caisson 3 of the present invention.

According to the breakwater structure of the present invention, waves generated on the sea surface 6 collide with the caisson 3 and are blocked, preventing waves from directly entering the gap (inside the port) from the caisson 3, thereby maintaining calm in the port. can be kept. Furthermore, since the box culvert 10 is arranged between the caisson 3 and the mound 2, the size of the caisson 3 can be significantly reduced compared to the conventional one. The reason is that, as mentioned above, the mound 2 can be considered to be higher by the height of the box culvert 10, and the seawater 7 near the seabed can pass through the channel 12 from the oil side to the gap, and the caisson 3 at the time of wave breakage. This is due to the fact that the uplift force can be reduced to an almost negligible level.

For example, when the wave amplitude is 8.50 m, the period is 12.5 seconds, and the depth from the sea surface 6 to the seabed ground 1 is approximately 25.0 m, we will compare the conventional breakwater structure and the present invention. The table will then look like the one on the next page. In other words, according to the conventional construction method, the size of caisson 3 (per box) is 22
x22x24m and weighs 6030 tons,
The size of the caisson 3 according to the present invention is 15×15×1 in volume.
It will be smaller at 7m and weighs 2100 tons. Looking at this in terms of weight per unit length, the conventional caisson 3 weighs 274 tons.
On/m, it can be seen that the caisson 3 according to the present invention is as light as 140 ton/m.

Furthermore, the amount of sand, etc. (filling) to be filled into the chamber 3a of the caisson 3 is 9160 m' (420 m'/m>) in the past, whereas in the present invention it is 3000 m' (200 m'/m).
Conventionally, the volume of the upper concrete 4 of the caisson 3 is 99.0 m''/m, whereas in the present invention, the volume of the upper concrete 4 of the caisson 3 is as small as 6.
It is small at 7.5m'/m.

By the way, the present invention uses box culvert 1, which was not available in the past.
0 is required, and its size is 15 x 25 volumes per box.
If you add the weight per unit length of this box culvert 10, which is
40=260 (ton/m), and the conventional caisson 3
It seems to be a slight difference because it is 274 ton/m, but the difference between the conventional and the present invention is 42 ton/m.
The difference is 0-200=220 (m'/m), and it can be seen that the weight per unit length of the entire breakwater is significantly reduced.

By achieving the miniaturization of the caisson 3 in this manner, its manufacturing and installation methods become easier and faster than in the past. In particular, it is important that construction work for breakwaters can be carried out quickly in view of sea damage, and the present invention has a great advantage in this respect.

Furthermore, the weight of the breakwater structure as a whole can be significantly reduced, and costs can be reduced.

Also, as shown in Figure 3, when there are no waves and there are no waves, the support reaction force against the caisson 3 of the box culvert 10 shows an equal distribution in the length direction as shown in diagram F, but when waves occur, Due to the wave force from the oil side to the land side of the caisson 3, the support reaction force of the box culvert 10 against the caisson 3 is maximum (approximately 99.1 ton/m") on the land side wall, as shown in diagram S. The top plate 10b on the land side of the box culvert 10 is formed thicker than the top plate 10a on the oil side so as to withstand such a lopsided support reaction force that shows a lopsided distribution map (triangular distribution).

Also, this biased support reaction force is caused by box culvert 10
However, in this case, since the box culvert 10 is interposed to support the mound 2, the support reaction force generated on the mound 2 is equal in the length direction as shown in diagram G. Approximately 20 ton/m2> distribution map is shown, and the supporting reaction force generated on the seabed ground 1 via mound 2 is also equal in the length direction and is approximately 17 ton/m') distribution map (figure omitted). In contrast, in the past, a biased support reaction force of up to 85.8 ton/m" with a triangular distribution was generated directly on the mound 2 and the seabed ground 1.
Large-scale ground improvement was required in areas where the ground on the ocean floor was weak.

However, in the present invention, since the provision of the box culvert 10 does not generate a biased support reaction force on the mound 2 or the seabed ground 1, the load on the seabed ground 1 can be reduced accordingly, and the seabed ground 1 This reduces the need for large-scale ground improvement even in areas where soil is relatively weak.

Furthermore, since a waterway 12 is formed in the box culvert 10, the seawater 7 between the oil side and the land side can come and go and be exchanged with each other. Therefore, the seawater 7 in the port is constantly exchanged with the seawater 7 on the oil side and kept fresh, which can bring about favorable results in terms of fisheries, the environment, and the like.

In the above embodiments, a case where a cubic caisson is used is explained, but the present invention can be applied to a caisson having a cylindrical shape or any other shape.

In addition, the cross section of the entire breakwater structure is determined from the height of the upper end of caisson 3 and the height of box culvert 1, based on the wave height conditions in the port during waves.
It is preferable to consider and determine the opening area of the water channel 12 at 0.0.

〔Effect of the invention〕

As explained above, according to the present invention, the size of the caisson can be significantly reduced compared to the conventional one, and the manufacturing and installation methods thereof are easier than the conventional ones, and costs can be reduced.

In addition, by placing a culvert structure between the caisson and the mound, it is advantageous in terms of ground bearing capacity.
Even in places where the ground is relatively weak, it is not necessary to improve the ground, or the extent of the improvement can be reduced.

Furthermore, since the culvert structure has a water channel, the seawater in the port is constantly exchanged with the seawater on the oil side and kept fresh, which can bring about favorable results in terms of fisheries and the environment.

In particular, the present invention is highly effective in cases where the water depth is large and the wave conditions are severe, so that the caissons of conventional breakwaters have become too large and the supporting capacity of the ground is insufficient.

1... Submarine ground 2... Mound 3... Caisson 10... Box culvert (culvert structure) 12... Water channel

Claims (1)

[Claims] It comprises a mound formed on seabed ground, a caisson placed above the mound and filled with sand, etc., and a culvert structure placed between the mound and the caisson and in which a waterway is formed. A breakwater structure featuring: