JP3643260B2 - Lightweight concrete caisson - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a lightweight concrete caisson used for a breakwater such as a harbor, a revetment, a quay and a construction method using the same.
[0002]
[Prior art]
In general, when constructing a breakwater, revetment, or quay, a concrete caisson as shown in FIG. 5 is used. For example, a box-like structure is sunk to the support mound and filled with sand and resists waves and the like due to the weight of the box itself.
[0003]
Such a concrete caisson is formed in a box shape in which an outer wall 11 is provided at the upper edge of the floor board 10 and the inside of the outer wall 11 is partitioned by a partition wall 12 in a lattice shape.
In the manufacturing method, after the floor board 10 is first constructed, an outer wall 11 and a reinforcing bar (not shown) for the partition wall 12 are assembled and installed, and concrete is placed inside the outer wall 11 and the partition wall 12. It will be completed. In this method, as in the case of construction of a normal concrete structure, a series of operations of dismantling the formwork and support after the concrete curing were repeated to obtain a structure with a predetermined height.
[0004]
Such a concrete caisson is generally produced on land or on the floating dock 13 shown in FIG. The completed concrete caisson is then transported by floating the sea to a predetermined installation position, adding water to the filling sand container, increasing the weight, and laying on the bottom of the sea. I try to replace it.
[0005]
By the way, in the above-mentioned conventional concrete caisson, since the whole is formed with normal concrete, specific gravity becomes considerably heavy. If the water depth at the caisson is deep, the height of the caisson will inevitably increase. In this case, when the concrete caisson is floated on the sea and moved to a predetermined position, the draft becomes deep and it becomes impossible to tow without floating, or the floor board 10 is in contact with the seabed in a place where the water depth is shallow even if it floats. There is a risk of it. In addition, in order to increase buoyancy, there are cases where the width of the caisson has to be increased more than necessary for stability against waves after completion.
[0006]
Therefore, it is desirable to reduce the weight of the concrete caisson as much as possible and to make it possible to tow and install even when the caisson height is high or the water depth is shallow by making the draft shallow.
[0007]
Specifically, as shown in FIG. 6, when manufacturing a concrete caisson on the floating dock 13, the height of the outer wall 11 and the partition wall 12 is made lower than the total height actually required to reduce the weight. It is possible to plan. This reduces the weight of the concrete caisson so that it can be moved even in shallow waters. However, in such a method, when it is sunk to a position where it should be originally installed, the height of the outer wall 11 is too low and the water is submerged under the sea surface 16.
[0008]
Therefore, as shown in FIG. 8, the outer wall or bulkhead is raised halfway by land or floating dock, and in that state, a concrete caisson is placed on the temporary mound 15 that is pulled out to the sea and installed on the seabed 14. The connecting outer wall 11a and the partition wall 12a are connected. Depending on the case, it will be added on the top sea until it reaches a predetermined height like the outer wall 11b and the partition wall 12a (FIG. 9). The finished product is towed to the main mound 17, the floor board 10 is settled, and the filling sand 18 formed between the partition walls 12 is packed.
[0009]
Further, in order to reduce the construction work at sea where the working conditions are extremely inferior, as shown in FIG. 11, the width necessary for stabilizing the wave after completion, which is the original purpose (shown in FIG. 11A). In many cases, the width of the caisson is widened and the volume is increased to increase buoyancy and shallow drafts. FIG. 11 (b) shows an example of the width determined by the draft at the time of floating, which is wider than the width necessary for stability against waves that are originally required.
[0010]
[Problems to be solved by the invention]
However, when the above-described conventional concrete caisson is employed, it is inevitable that the construction period is extended and the cost is increased because the construction is complicated. In particular, the addition work at sea, which is inferior to the working environment, is difficult, and from the standpoint of quality after completion, initial defects such as bean plates, flaps, and cold joints that occur on the concrete surface are likely to occur. In addition, the use of lightweight concrete is conceivable, but because lightweight concrete using conventional lightweight aggregates has high water absorption, there are problems in durability such as freeze-thaw resistance and workability such as pumpability. Hiring is difficult.
[0011]
Furthermore, conventional lightweight concrete using lightweight aggregates is weak in tensile strength and shear strength, so that it is difficult to adopt even when the ground on which the caisson is ground is soft and uneven settlement is expected.
[0012]
[Means for Solving the Problems]
The present invention is a lightweight concrete caisson and a construction method using this lightweight concrete caisson, and is configured as follows in order to solve the technical problems described above. That is, it is a caisson that is provided with an inside sand receiving portion 3 formed by a floor board 1 and an outer wall 2 standing upright from the floor board 1 and a partition wall 7 connecting the outer walls, and should be installed on the sea floor 4. In addition, all or part of the floorboard 1 outer wall 2 and partition wall 7 are made of low water absorption and high durability light weight concrete whose specific gravity can be adjusted, and the draft when floating in water is configured to be shallower than when ordinary concrete is used. did.
[0013]
The low water absorption and high durability lightweight concrete, those that use high-performance lightweight aggregate you a pearl rock as the main raw material, can be used. In this lightweight aggregate, the raw materials are finely pulverized, mixed and granulated, and the internal pores are made into independent pores in the baking and manufacturing process after drying. As a result, the water absorption rate is as small as 5% or less as compared with the conventional lightweight aggregate, and the compressive strength of the aggregate is 1000N to 1500N, which can provide a high strength as compared with the conventional lightweight aggregate.
[0014]
In addition, by making the low water absorption and high durability lightweight concrete fluid and forming a lightweight concrete caisson in a state where it is difficult to separate, the height of one lot in production, which was conventionally limited to 3 m or less, can be extended. The construction period can be shortened and the construction cost can be reduced.
In order to fluidize low water absorption and high durability lightweight concrete, an admixture is added to disperse the cement to ensure fluidity and prevent the aggregate from separating. As the admixture, for example, a separation-reducing type such as a high-performance AE water reducing agent (Takemoto Oil HP70 or the like) can be used.
[0015]
When producing such low-water-absorbing and highly durable lightweight concrete using such high-performance lightweight aggregates as coarse aggregates, two types of coarse aggregate specific gravity of 0.85 and 1.2 are prepared. By appropriately combining natural sand, it is possible to adjust to a desired specific gravity in the range of 1.2 to 1.8 in terms of the specific gravity of the concrete that has been kneaded.
[0016]
Further, the reinforcing fiber reinforcing layer 5 can be formed around the outer wall 2. Examples of the reinforcing fibers used in the reinforcing fiber reinforcing layer 5 include glass fibers, carbon fibers, stainless steel fibers, and steel fibers. These reinforcing fibers are kneaded with concrete to form a reinforcing fiber reinforcing layer 5 around the outer wall 2.
[0017]
The construction method using this lightweight concrete caisson includes an inside sand containing portion 3 formed from a floor board 1 by an outer wall 2 erected at the same height as the completed height and a partition wall 7 connecting the outer walls. Equipped, constructing a lightweight concrete caisson in which all or part of the floorboard 1, outer wall 2 and partition wall 7 are made of low water absorption and high durability lightweight concrete, and float the entire lightweight concrete caisson to a predetermined installation position, After injecting seawater and laying it down and landing on the bottom of the sea, it will be completed with sand inside.
[0018]
As described above, all or part of the floorboard, outer wall, and partition walls are made of low water absorption and high durability lightweight concrete adjusted to the desired specific gravity, so that the draft is as shallow as necessary when floating in water. be able to. Therefore, even if the height of the wall is constructed on the floating dock, the concrete caisson will not settle during towing. For this reason, it is not necessary to add an outer wall or a bulkhead on the sea as in the past, and a concrete caisson can be completed on land or on a floating dock.
[0019]
Further, in order to reduce construction work at sea where the working conditions are extremely inferior, as shown in FIG. 11 (b), the width necessary for stability against the wave after completion, which is the original purpose (FIG. 11 (a)). ) The caisson width can be reduced by adjusting the specific gravity of the concrete caisson even in the case where the caisson is widened and the volume is increased to increase the buoyancy and shallow the draft.
[0020]
Furthermore, even when the ground where the caisson bottoms is soft and uneven settlement is expected, by forming a reinforcing fiber reinforcement layer around the outer wall, the tensile strength and shear strength, which are disadvantages of lightweight concrete, can be reduced. I can deal with it. In order to provide the reinforcing fiber reinforcing layer, a fiber-reinforced precast embedded formwork can be used.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the construction method of the concrete caisson using the lightweight concrete caisson and the lightweight concrete of the present invention will be described in more detail with respect to the embodiment shown in FIGS. In addition, the same code | symbol is attached | subjected to the part same as description in a prior art, and the description is abbreviate | omitted.
[0022]
FIG. 1 shows the entire concrete caisson, in which a rectangular outer wall 2 is erected over four sides from a floor board 1. And since the inside of the outer wall 2 is reinforced by the partition 7 in a lattice shape, it is divided into a large number of spaces. In this figure, the partition 7 is formed in 3 columns and 5 rows, and 15 hollow filled sand accommodating portions 3 are formed.
[0023]
The filling container 3 is filled with filling sand to increase the weight of the concrete caisson so that it does not slide or fall against external forces such as waves. A reinforcing fiber reinforcing layer 5 is formed over the entire outer periphery of the outer wall 2. Specifically, the reinforcing fiber reinforcing layer 5 is a precast concrete frame, which increases the tensile resistance of caisson.
[0024]
The floor board 1, the outer wall 2 and the partition wall 7 are made of low water absorption, high durability and lightweight concrete. An example of the low water absorption and high durability lightweight concrete used here is as follows. Specific gravity of 1 is obtained when a specific gravity of 1.2 is used for a light coarse aggregate, and a mixture of natural sand and lightweight fine aggregate is used for a fine aggregate. 5 and compressive strength of 49.1 N / mm 2.
[0025]
Therefore, the concrete caisson as a whole is lighter than conventional ordinary concrete and has a shallow draft when the caisson is floating. For this reason, the outer wall 2 and the partition wall 7 can often be formed at a desired height (the same height as the total height after completion of construction) on the land or the floating dock from the beginning of manufacture.
[0026]
In this way, if it is not necessary to perform addition after production on land or a floating dock, it is possible to reduce work in a poor environment at sea. Along with this, it is possible to reduce the construction cost, shorten the construction period, and improve the construction safety.
[0027]
Moreover, since it is not necessary to increase the width of the caisson in consideration of the draft, the construction cost can be reduced and the construction period can be shortened.
FIG. 2 shows the production on the floating dock 13, and the completed concrete caisson is towed to the set position as shown in FIG. And after pouring seawater into the filling sand accommodating part and sinking it to the main mound, sand is thrown in to a predetermined weight and completed.
[0028]
In addition, since the lightweight concrete is a low water absorption type, the concrete caisson itself has low water absorption, and durability is improved.
[0029]
【The invention's effect】
According to the present invention, all or part of the floorboard, outer wall, and partition walls are made of low water absorption and high durability lightweight concrete, and the specific gravity is lighter than the conventional one, so that it can float in many cases even when the water depth is shallow. Become. Therefore, it is not necessary to increase the width of the caisson in order to add an outer wall and a partition wall at sea, or to make the draft shallower, and it can be manufactured at a necessary height from the beginning.
[0030]
For this reason, construction is easy, and the construction period can be shortened and the cost can be reduced. Furthermore, excellent quality and strength can be obtained with less occurrence of bean plate and surface flutter, which are initial defects.
[Brief description of the drawings]
FIG. 1 is a perspective view of a lightweight concrete caisson according to an embodiment of the present invention.
FIG. 2 shows a state in which a lightweight concrete caisson according to an embodiment of the present invention is manufactured on a floating dock.
FIG. 3 is a cross-sectional view showing a state in which a lightweight concrete caisson according to an embodiment of the present invention is moved on water.
FIG. 4 is a cross-sectional view showing a state in which a lightweight concrete caisson according to an embodiment of the present invention is installed on a water bottom.
FIG. 5 is a perspective view showing a conventional ordinary concrete caisson.
FIG. 6 is a cross-sectional view showing a state where a conventional ordinary concrete caisson is manufactured on a floating dock.
FIG. 7 is a cross-sectional view showing an initial state of a manufacturing process of a conventional ordinary concrete caisson.
FIG. 8 is a cross-sectional view showing an intermediate state of a conventional ordinary concrete caisson manufacturing process.
FIG. 9 is a cross-sectional view showing a late state of a manufacturing process of a conventional ordinary concrete caisson.
FIG. 10 is a cross-sectional view showing a state in which a conventional ordinary concrete caisson is installed on the bottom of the water.
11A is a diagram showing a conventional example of caisson width when determined by waves or the like. FIG. 11B is a diagram showing a conventional example in which the width of a cross section is determined by draft when floating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Floor board 2 Outer wall 3 Filled sand accommodating part 4 Seabed 5 Reinforcement fiber reinforcement layer 6 Filled sand 7 Bulkhead 13 Floating dock 14 Seabed 16 Sea level 17 Mound

Claims (2)

A caisson to be installed on the bottom of the water, provided with a filling sand containing portion formed by a floor plate and an outer wall erected from the floor plate, and a partition wall connecting the outer walls;
A reinforcing fiber reinforcement layer is formed around the outer wall,
The floor plate, all or a portion of the outer wall and the partition wall, made by combining a water absorption rate of 5% or less lightweight aggregate and natural sand as appropriate is incorporated as aggregate, and a specific gravity of at kneading up 1.2 A lightweight concrete caisson made of low-water-absorbing and highly-durable lightweight concrete with a thickness of ˜1.8, so that the draft when floating in water is shallow. The light-weight aggregate is obtained by mixing and granulating pearlite after finely pulverizing pearlite, and mixing it as an aggregate with internal pores as independent pores in a baking and manufacturing process after drying. Lightweight concrete caisson.

Images