JP5983435B2 - Gravity breakwater - Google Patents

Description

  The present invention relates to a gravity breakwater formed by a caisson made of concrete, for example, and more particularly to a gravity breakwater having a structure that is tough against waves having large energy such as a tsunami.

  A breakwater using a concrete caisson, widely known as a gravity breakwater, is a structure that resists loads acting on energy such as waves by filling the caisson with gravel and water. In general, stabilization is achieved by the frictional force generated between the ground where the caisson is installed and the mound built on the ground due to the gravity.

By the way, the gravitational breakwaters as described above are usually used for loads associated with energy such as waves (including storm surges) caused by typhoons and developed low pressures, or tsunamis caused by earthquakes, which are likely to occur during the service period. Is designed to be safe.
However, when a load with energy more than expected is applied, sliding failure may occur due to insufficient frictional force between the caisson and the ground or mound.
In fact, in the Great East Japan Earthquake that occurred in 2011, a tsunami larger than expected occurred, and a load exceeding the expected level was applied to the caisson. Occurred and destroyed so that the function of the breakwater was lost in an instant, and suffered enormous damage, resulting in a situation where the function as a breakwater could not be guaranteed at all.

  For this reason, when a load associated with energy such as tsunami assumed in the conventional design is applied, even if a certain amount of damage is caused, avoid breakage that suddenly loses the function as a breakwater, and slightly enhance the function of the breakwater However, there is a demand for a persistent breakwater structure that can be maintained.

In response to this, as shown in FIG. 5, in the gravity type breakwater 11, a backfill stone is placed on the rear surface side (inside of the harbor) of a heavy structure 14 such as a caisson disposed on a mound 13 formed on the ground 12. A reinforcing structure 15 for reinforcing a breakwater has been proposed in which a reinforcing base 15 formed in an inclined surface shape is stacked to thereby suppress the movement of the heavy structure 14.
However, according to this reinforcing structure, although it can resist a larger load depending on the weight of the reinforcing table 15, the type of failure in the case of the breakwater 11 having this reinforcing structure is represented by sliding failure. Once destruction begins, it becomes destruction that loses function in an instant. That is, when a heavy load is applied to the heavy structure by a tsunami or the like and the reinforcement base that should receive this load is broken without being able to withstand the load, the heavy structure slides and is swept away at once, Because it loses its function instantly, it is hard to say that it has a tenacious structure.
In addition, the method of stacking backfill stones inside the port to form the reinforcement stand 15 reduces the effective area of the port and changes the depth of water at various locations within the port. There is a high possibility that it will need to be changed, which may cause problems such as many restrictions on the use of port facilities.

Moreover, as a proposal of a tenacious structure, the method of utilizing the steel building materials which have high toughness, such as a steel pipe pile and a steel sheet pile other than the above-mentioned thing exists.
For example, Patent Document 1 describes a revetment structure in which a cell is formed using a steel pipe sheet pile or the like, and a filling soil is filled in the cell. The technique of this Patent Document 1 can realize a very useful and tenacious structure when constructing a new structure related to a revetment structure, but cannot be applied to the structure of a heavyweight breakwater using a caisson. .

Patent Document 2 describes a revetment structure in which a wall-like structure composed of a steel sheet pile or a steel pipe sheet pile is placed on the front side and the rear side of a caisson, and the wall-like structure is connected to the caisson. Yes.
However, although this revetment structure has no problem in terms of structural stability, the technology of Patent Document 2 described above is a revetment structure, and the front side of the caisson is a sea or a river, while the rear side is a land. Therefore, since the installation work can be performed relatively easily by accessing from the land on the revetment side, simplification of the installation work is not essential. On the other hand, in the case of a breakwater installed in the sea area sandwiched between the front side and the rear side, the installation work is very large and difficult in the first place, compared to the above revetment structure, and the cost is also very high. A big burden. In addition, since the basic concept of the tenacious structure is completely different from the breakwater facing the sea on both the front side and the back side, this technology cannot be used for the breakwater as it is.

JP 2003-253644 A Japanese Patent Laid-Open No. 9-13343

  The technical problem of the present invention is to provide a gravitational breakwater having a tenacious structure that does not lose all functions in an instant even if a load accompanying a large energy such as an unexpected tsunami is applied, and a construction method thereof. It is in.

  In view of the above, as a result of earnest research to find a tenacious structure in a breakwater equipped with a heavy structure such as caisson, the present inventors have found that a steel sheet pile in which the front side and the rear side of the heavy structure are placed on the ground It has been found that it is effective to support by a wall-like support structure formed by a steel pipe sheet pile or the like so that the support structure directly receives the horizontal force from the heavy structure.

On the other hand, a support structure that supports the weight structure is protruded from the mound in the immediate vicinity of the weight structure placed on the mound formed on the ground, and the protruding portion is When placed on the ground in direct contact with the heavy structure, the heavy structure is easily affected by changes in the ground properties associated with the placement of the support structure, and the ground and mound may loosen. Conceivable.
Doing so may cause the installation of heavy structures to become unstable or make it easier to slide, so in the case of a breakwater with a structure that allows the support structure to directly receive the horizontal force from the heavy structure, It was found that it is important to minimize the influence of changes in ground properties due to the placement of structures locally and minimally.

Furthermore, when the rear surface side and / or the front surface side of the heavy structure is supported by the wall-shaped support structure, the support structure is placed on the mound or ground so that the wall surface faces the rear surface or front surface of the heavy structure. If installed, the water flow through the mound may be completely obstructed.
For example, when the support structure is installed only on the rear side, the water flow that has penetrated into the mound is blocked by the support structure, so that the pore water pressure in the mound increases excessively and the ground strength in the mound decreases. In addition, there is a risk of causing a lifting force higher than expected in the heavy structure to impair the stability of the heavy structure.
Therefore, it was found that it is necessary to suppress as much as possible the influence of the water flow penetrating the mound on the mound and the heavy structure.

The present invention has been completed based on the above findings.
That is, in order to solve the above-described problem, the gravity breakwater of the present invention includes a heavyweight structure for wave protection disposed on the ground or a mound provided on the ground, and a front side of the heavyweight structure. A wall-like support structure extending in the vertical direction, which is disposed on at least one side of the rear surface side and receives the force in the horizontal direction from the weight structure to support the weight structure; The support structure extends in the front-rear direction of the heavy structure, one end abuts on the heavy structure, and the upper end side is upward from the ground or mound on which the heavy structure is disposed. It is characterized by being placed on the ground in a protruding state.

In the present invention, the heavy structure is formed in a rectangular parallelepiped shape, and the support structure is extended in a direction orthogonal to the front surface and / or the rear surface of the heavy structure. be able to.
Furthermore, in the present invention, the support structure may be brought into contact with the heavy structure in an unconnected state.
In the present invention, it is preferable that the support structures are respectively disposed at positions on at least both ends in the width direction on the front surface and / or the rear surface of the heavy structure.

Furthermore, in the present invention, the height of the protruding portion from the ground or mound in the support structure is lower than the height in the vertical direction of the weight structure in a state of being disposed on the ground or mound. can do.
Further, in the present invention, the support structure is formed of a plurality of steel pipe sheet piles or steel sheet piles, and the adjacent steel pipe sheet piles or steel sheet piles are fixed so that their mutual positions are immobile. Accordingly, it is preferable that in-plane shear deformation hardly occurs in the support structure.

According to the present invention, the supporting structure that supports the heavy structure is configured so as to extend in the front-rear direction of the heavy structure, one end abuts the heavy structure, and the heavy structure is arranged. By placing on the ground with the upper end protruding upward from the installed ground or mound, the horizontal force from the heavy structure can be directly received to prevent breakage of the breakwater.
In addition, since the heavy structure is extended in the front-rear direction, the influence of changes in the ground properties of the mound immediately adjacent to the heavy structure and the ground due to the placement of the support structure is minimized locally. Thus, sliding and sinking of the heavy structure due to the placement of the support structure can be suppressed. Furthermore, since the support structure does not hinder the water flow that has penetrated into the mound, the pore water pressure in the mound does not increase, thereby reducing the ground strength in the mound or raising the pressure above the expected for heavy structures. Can be prevented and the stability of the heavy structure can be secured.

  Therefore, even if a load accompanying large energy such as an unexpected tsunami acts and the heavy structure moves, the support structure can prevent complete breakage of the breakwater due to the heavy structure sliding or sinking. Thus, it is possible to obtain a gravitational breakwater having a tenacious structure that does not lose all the breakwater functions in an instant.

It is sectional drawing which shows typically one Embodiment of the gravity type breakwater which concerns on this invention. It is the same top view. It is a schematic diagram explaining the water flow from the flow field which generate | occur | produces in the clearance gap between heavy weight structures. It is sectional drawing which shows typically embodiment different from FIG. 1 of the gravity type breakwater which concerns on this invention. It is sectional drawing which shows typically an example of the reinforcement structure of the conventional weight type breakwater.

1 and 2 show an embodiment of a gravity breakwater according to the present invention. A breakwater 1 according to this embodiment is disposed on a mound 3 formed on a ground 2 in the sea. A weight structure 4 for preventing waves and a wall-like support structure 5 extending in the vertical direction are provided on the rear surface side of the weight structure 4.
In the present invention, the front side of the heavy structure is basically the direction opposite to the land (in the case of a port, the outside of the port), and the rear side of the heavy structure is basically the land. It points to the opposite direction (in the case of a port, the inner side of the port). Moreover, the breakwater in this invention points out the thing by which the front side and rear surface side of a heavyweight structure face the sea, and also contains what is called a wave breakwater notionally.

The weight structure 4 is, for example, a caisson formed in a concrete box shape and filled with crushed stone or the like, or a stacked block formed of concrete. It resists by receiving the received load.
In this embodiment, a concrete caisson formed in a substantially rectangular parallelepiped shape is used, and is placed on the mound 3 with a part of the upper end side protruding upward from the sea surface S. Further, as shown in FIG. 2, the breakwater 1 has a configuration in which a plurality of caissons as the heavy structure 4 are arranged side by side in a state where gaps 6 having a predetermined interval are provided.
Further, the mound 3 is formed by pulverizing stones or the like up to a predetermined height on the ground 2 in the sea, and the upper end portion is a flat surface on which the heavy structure is stably placed. Be able to.

The support structure 5 has a function of receiving the horizontal force from the heavy structure 4 and supporting the heavy structure 4, and has a series of wall-like configurations extending in one direction as a whole. Yes.
The support structure 5 of this embodiment is formed of a plurality of steel pipe sheet piles, and the adjacent steel pipe sheet piles are joined together, for example, by connecting parts such as welding or joints or the head part of the steel pipe sheet piles, such as concrete. The adjacent steel pipe sheet piles are connected to each other so that their positions are fixed, and in-plane shear deformation in the support structure 5 is possible. It has a structure that can be suppressed.

Further, the support structures 5 are respectively disposed in the rear side of the weight structure 4 at positions on both end sides in the lateral width direction in a non-connected state with the weight structure 4.
Each of these support structures 5 extends in the front-rear direction of the heavy structure 4, that is, in the direction perpendicular to the rear surface of the heavy structure 4 in this embodiment. Each support structure 5 is in a state where one end side is in contact with the heavy structure 4 in an unconnected state, and the upper end side protrudes upward from the mound 3 on which the heavy structure 4 is disposed. It is placed on the ground 2 with a loading amount.
Accordingly, these support structures 5 are extended so as to be substantially parallel to each other, and their respective wall surfaces (surfaces along the extending direction of the support structure 5 (the front-rear direction of the heavy structure 4)). However, it is the state extended in the direction in alignment with the side surface of a heavy weight structure.

Here, the reason why the support structure 5 is extended in the front-rear direction of the heavy structure 4 is, as a first reason, the change in the ground properties of the mound 3 and the ground 2 caused by the placement of the support structure 5. This is to suppress as much as possible the influence of the above on the heavy structure 4.
As already mentioned, when the support structure is placed in the immediate vicinity of the heavy structure, the ground and ground properties of the mound and the ground due to the placement of the support structure may change, and the ground and mound may loosen. It is done. Doing so makes the installation of heavy structures on the mound or the ground unstable and makes it easier to slide.Therefore, the heavy structures are affected by changes in the ground properties due to the placement of the support structure. It is necessary to suppress as much as possible.
Therefore, in the present invention, the support structure is extended in the front-rear direction of the heavy structure, and is placed on the mound or the ground so that one end side thereof is brought into contact with the heavy structure in an unconnected state. By doing so, the change of the ground property accompanying the placement of the support structure is accommodated in a very small range in the immediate vicinity of the heavy structure. Thereby, the influence on the heavy structure is suppressed as much as possible by minimizing the influence of the change in the ground property locally and to the minimum.

The second reason for extending the support structure 5 in the front-rear direction of the heavy structure 4 is that the water flow that has penetrated into the mound 3 due to a tsunami or the like may affect the mound 3 or the heavy structure 4. This is to suppress as much as possible.
When the heavy structure is supported by the wall-shaped support structure, in order to improve the support force for the heavy structure, for example, the support structure with the wall surface of the support structure facing the rear surface of the heavy structure. Can be placed on the mound.
However, when the support structure is placed on the mound or the like with the wall surface facing the rear surface of the heavy structure in this way, for example, the water flow that has permeated into the mound from the front side of the heavy structure has a wall shape. Since it will be interrupted | blocked by the said support structure formed, there exists a possibility that the pore water pressure in a mound may rise excessively.
Then, this excessive rise in pore water pressure loosens the mound and ground, and it is highly possible that the strength of these grounds will decrease, and further upward pressure will occur in the heavy structure due to the upward water pressure. There is also a possibility that the stability of heavy structures is greatly impaired.
Therefore, in the present invention, in order to prevent such an excessive increase in the pore water pressure in the mound, the supporting structure is extended in the front-rear direction of the weight structure, and the water flow that has permeated into the mound. The water flow is allowed to pass through without leaving any influence on the mound or the like.

Furthermore, in this embodiment, the support structures 5 are arranged at the positions on both ends in the lateral width direction on the rear surface of the heavy structure 4 so that the horizontal load of the heavy structure 4 is balanced. This is for receiving and preventing the weight structure 4 from sliding.
Moreover, it is for suppressing the influence of the water flow by the rapid flow field formed in the clearance gap 6 between the adjacent heavy structures 4 and 4. FIG. This point will be described in detail. In the gravity breakwater as in the present invention, it is common to arrange a plurality of heavy structures at regular intervals. In the case of such a gravity breakwater, When waves and tsunamis come near, a rapid flow field is formed in the gap between adjacent heavy structures.
For example, as shown in FIG. 4, when a tsunami or the like comes from the front side of the heavy structure 4, the gap 6 between the heavy structures 4, 4 has a rear side direction (indicated by a white arrow in FIG. 3). Direction) flow field. And since the water flow from this flow field tends to flow so that it may spread near the rear surface side of each heavy structure 4,4 as the arrow in FIG. 3, the rear surface of each heavy structure 4,4 The side mound 3 and the ground 2 may be scoured. Conversely, even in the case of a pulling wave, an abrupt flow field in the direction from the rear side to the front side of the heavy structure is formed in the gap between the adjacent heavy structures, and the water flow flows to each heavy structure. Since it flows so as to expand near the front side, the mound and ground on the front side of each heavy structure may still be scoured.
In this way, when the mounds and the ground before and after the heavy structure are scoured, the supporting force on the heavy structure is reduced and the heavy structure is likely to be swept away. It may happen that you lose your function in an instant.

  Therefore, in this embodiment, by arranging the support structures 5 at positions on both ends in the width direction on the rear surface of the weight structure 4, as shown in FIG. The water flow from the rapid flow field formed in the gap 6 between the objects 4 and 4 is prevented from flowing into the vicinity of the rear surface of the heavy structure 4, and the mound 3 and the ground 2 near the rear surface of the heavy structure 4 and in the vicinity thereof. Is prevented from being scoured and the occurrence of sliding destruction can be suppressed.

In this embodiment, the support structure 5 is brought into contact with the heavy structure 4 in an unconnected state in order to simplify the installation work and reduce the installation cost.
That is, in the prior art, a heavy structure such as a caisson is connected to a wall-like structure that supports the heavy structure, so that the configuration of this point is complicated and the installation work is very troublesome. There were drawbacks. In addition, as in the present invention, in the case of a breakwater installed in a sea area sandwiched between the front and both sides of the front side and the rear side, the front side is the sea and river, while the rear side is land-based compared to the seawall structure Since the installation work is very large and difficult in the first place, the work for connecting the heavy structure and the wall-like structure as described above is very burdensome both in terms of labor and cost.

Therefore, in the embodiment, by omitting the connection work between the heavy structure 4 and the support structure 5 and simplifying the configuration of the entire breakwater, while ensuring the performance as a breakwater, The construction can be performed very easily as compared with a configuration requiring a simple connection.
As a result, it is possible to save the labor of construction work as compared with the prior art, and it is possible to reduce construction costs accordingly.

By the way, the height of the protruding portion 5 a protruding from the mound 3 in the support structure 5, that is, the height of the upper end of the placed support structure 5 is the height of the weight structure 4 placed on the mound 3. It is lower than this. In the case of what is shown in FIG. 1, the protrusion height of the protrusion part 5a of the support structure 5 is less than or equal to half the height of the heavy structure 4, and therefore the support structure 5 is located in the sea as a whole. Yes.
As described above, the projecting height of the projecting portion 5a of the support structure 5 is lower than the height of the weight structure 4 placed on the mound 3 because the support structure is mainly formed from the weight structure. This is because a structure that can support the horizontal load and obtain the effect of suppressing horizontal displacement such as sliding of the heavy structure and that can ensure at least the effect is sufficient.

The length of the support structure 5 in the extending direction (the longitudinal direction of the heavy structure) is the required performance for the gravity breakwater 1, the rigidity of the support structure 5, the operation in the harbor (including the route), etc. It is set appropriately according to
In the case of this embodiment, the length of the support structure 5 in the extending direction is a length that can be accommodated in the mound 3.

In constructing a breakwater having the above-described structure, first, a mound 3 having a predetermined height is formed on the ground 2, and a heavy structure 4 is placed and disposed on the mound 3. The mound 3 and the heavy structure 4 at this time may be newly established, but may be an existing mound and heavy structure. Therefore, the already built breakwater mound and heavy structure are used. can do.
Thereafter, the support structure 5 extending in the front-rear direction of the weight structure 4 on the rear surface side of the weight structure 4, more specifically in the direction orthogonal to the rear surface of the weight structure 4, One end side is in contact with the heavy structure 4 in a non-connected state, and is placed in the vertical direction on the ground 2 with the upper end side protruding upward from the mound 3 on which the heavy structure 4 is disposed. As a result, the breakwater 1 having a tenacious structure is completed.

At this time, when the tsunami or the like approaches, the support structure 5 directly receives the horizontal force from the heavy structure 4 and supports the heavy structure 4. Can be destructed without losing it in an instant.
Further, since the support structure 5 extends in the front-rear direction of the heavy structure 4, changes in the ground properties of the mound 3 and the ground 2 immediately adjacent to the heavy structure 4 due to the placement of the support structure 5. Thus, it is possible to suppress the sliding and sinking of the heavy structure 4 due to the change in the ground properties due to the placement of the support structure 5.
Furthermore, since the support structure 5 does not hinder the water flow that has penetrated into the mound 3, the pore water pressure in the mound 3 does not increase, thereby reducing the ground strength in the mound 3, It is possible to prevent the occurrence of lifting pressure higher than expected and to ensure the stability of the heavy structure 4.
As a result, even if a heavy energy load such as an unexpected tsunami acts on the heavy structure 4 and the heavy structure 4 moves, the support structure 5 slides or sinks the heavy structure 4. Since the complete breakage of the breakwater due to the damage is suppressed, it is possible to obtain a gravitational breakwater with a tenacious structure that does not lose all the breakwater functions in an instant.

In the above embodiment, the support structure 5 is disposed only on the rear surface side of the heavy structure 4, but the support structure may be disposed on the front surface side of the heavy structure.
Furthermore, as shown in FIG. 4, the support structure may be disposed on both the front side and the back side of the heavy structure. In this way, when the support structure is provided on both the front side and the rear side of the heavy structure, the effect of the present invention is exhibited even in the case of a tsunami or the like. Useful. In addition, about each structure of the ground structure and mound in FIG. 4, and the weight structure which forms a gravity-type breakwater, and a support structure, it is substantially the same as the said embodiment fundamentally, and the same In order to achieve the effect, the same reference numerals are given and detailed description is omitted.

Moreover, in the said embodiment, although the said support structure 5 is laid in the ground 2 in the state which penetrated the mound 3, the length of the extending direction (front-back direction of a heavy structure) of a support structure is demonstrated. Depending on the size of the sheath, part or all of it may be directly placed on the ground outside the mound. In addition, about the said support structure, when the length of the extending direction of a support structure cannot fully be ensured by the operational problem of a port, by raising the rigidity of this support structure itself, it is desired. The performance of the breakwater may be ensured.
Furthermore, in the above embodiment, the heavy structure 4 is placed on the mound 3 formed on the ground 2. However, depending on various conditions such as the shape of the ground surface and the ground properties, the heavy structure is You may make it mount directly on.

Moreover, in the said embodiment, although the said support structure 5 is set as the structure contacted | abutted with the said heavy structure 4 in the unconnected state, a support structure and a heavy structure are not necessarily in an unconnected state. It is not necessary and may be connected to each other.
Further, the height of the protruding portion 5a protruding from the ground 2 or the mound 3 in the support structure 5 is the same as that of the weight structure in the state of being disposed on the ground or the mound as in the above embodiment. The height does not need to be less than half of the height in the vertical direction, and does not necessarily need to be lower than the height in the vertical direction of the heavy structure, and can be set appropriately.
Further, when placing the support structure 5 on the ground 2, unlike a normal steel pipe pile or the like, it is not always necessary to root the lower end side of the support structure to the support layer of the ground, and the depth of rooting Alternatively, the amount of penetration can be arbitrarily set within a range that does not hinder, according to various conditions such as the surrounding environment.

  Furthermore, in the said embodiment, although the support structure 5 is made into the thing of the structure formed in the wall shape using the several steel pipe sheet pile, as a support structure, rigidity is fundamentally high and it is in-plane. Any wall structure can be used as long as shearing is unlikely to occur. For example, a wall formed using a steel sheet pile or the like may be used.

1 Breakwater 2 Ground 3 Mound 4 Heavy Structure 5 Support Structure 6 Clearance

Claims (6)

A weight structure for wave protection disposed on the ground or a mound provided on the ground, and a weight structure disposed on at least one of the front side and the rear side of the weight structure. A wall-like support structure extending in the vertical direction that supports the weight structure by receiving a horizontal force from the object,
The support structure extends in the front-rear direction of the heavy structure, one end abuts on the heavy structure, and the upper end side is upward from the ground or mound on which the heavy structure is disposed. Gravity-type breakwater that is placed on the ground in a protruding state.   The weight structure is formed in a rectangular parallelepiped shape, and the support structure extends in a direction orthogonal to the front surface and / or the rear surface of the weight structure. Gravity breakwater as described in.   3. The gravity breakwater according to claim 1, wherein the support structures are respectively arranged at positions on at least both ends in the width direction on the front surface and / or the rear surface of the heavy structure. .   The gravity type breakwater according to any one of claims 1 to 3, wherein the support structure is brought into contact with the heavy structure in an unconnected state.   The height of the protruding portion from the ground or mound in the support structure is lower than the height in the vertical direction of the heavy structure in a state of being disposed on the ground or mound. The gravity type breakwater according to claim 4.   The said support structure is formed with several steel pipe sheet piles or steel sheet piles, and the adjacent steel pipe sheet piles or steel sheet piles are being fixed so that a mutual position may not be fixed. The gravity type breakwater according to claim 5.

Images