JPH0585687B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an underwater top-shaped foundation block that is installed at locations affected by waves and water currents such as coasts, lakes, and river banks and bottoms. , relates to an underwater foundation construction method using the foundation block.

[Prior art] Wave-dissipating blocks of various shapes and structures have been developed to protect coastlines from wave erosion, but wave-dissipating blocks are constructed directly on the sand layer at the beach's beach without any effective foundation construction methods. Because the sand in contact with the bottom of the wave-dissipating block is gradually removed by waves and water current, the wave-dissipating block may topple over, disappear, or sink within a short period of time after being installed. The original bank protection function due to wave dissipation is lost. Therefore, it is necessary to repair the wave-dissipating block layer by piling it up again every year on top of the washed away block layer, and the burden of material and construction costs is extremely large.

On the other hand, Japanese Patent Application Laid-Open No. 1-280112 discloses a gentle slope revetment construction method using top-shaped foundation blocks. The top-shaped foundation block, which has a cylindrical pivot at the center of the lower end of the inverted truncated cone-shaped body and is buried with the pivot vertically arranged, is excellent in soft ground on land due to its unique shape and installation method. It has a low subsidence property and suppresses uneven subsidence of the ground.

However, the body of the conventional top-shaped foundation block is solid, and when this solid foundation block is installed at the edge of a beach where waves and water currents are intense, it is difficult to prevent the formation of foundation blocks that are laid flat. In the foundation blocks at the front and side edges, the sand around the body is gradually removed and scoured by waves and water currents, and in the worst case, the foundation blocks in those areas may tilt. There is a risk of falling.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to provide an underwater foundation block and an underwater foundation construction method that are resistant to scouring by waves and water currents and can firmly maintain the original laid condition. It is to be.

[Means for Solving the Problems] The underwater foundation block of the present invention will be described below using the reference numerals in the attached drawings. It is of a porous type in which a pivot leg 3 is provided, and a cavity 4 provided in the body 2 and the outer surface 2a of the body are communicated with each other through a large number of through holes 5.

In the underwater foundation construction method of the present invention, the porous foundation block 1 is buried in a sand layer 6 with the pivot leg 3 vertical, and the hollow portion 4 is filled with gravel, crushed stone, etc. to form a permeable filling layer 7.

In another underwater foundation construction method of the present invention, several types of porous foundation blocks of different sizes are prepared, and the number of porous foundation blocks 1 to be laid is gradually increased from the center of the foundation structure toward the front edge and left and right side edges. Reduce size.

In another underwater foundation construction method of the present invention, in addition to the porous foundation block 1, a solid body 12 in the shape of an inverted truncated cone or an inverted truncated pyramid is provided with a cylindrical or prismatic shaft leg 13 at the center of the lower end. Mold basic block 10
The solid type foundation block 10 is placed in the main part of the foundation structure, while the porous type foundation block 1 is placed in the main part of the foundation structure.
are placed at the front edge and left and right side edges of the foundation structure.

[Function] This porous foundation block 1 is laid adjacent to each other in the front, rear, left and right directions. When constructing the foundation structure of a wave-dissipating block or a jetty, the foundation block 1 is laid in a planar shape on a slope 9 from the lower part of the sea surface at the edge of the waves at low tide to the land area at the edge of the waves at high tide. Normally, almost the entire foundation block group from the pivot leg 3 to the head of the body 2 is buried in the inclined surface 6, and structures to be supported, such as wave-dissipating blocks, are installed on the upper surface of the body 2.

A part of the waves hitting the porous foundation block group enters the cavity 4 through the upper surface opening of the cavity 4 or the through hole 5 of the body 2, and its force is diminished as it rises onto the land surface 24. A part of the return water flow from the waves passes through the hole 5 from the cavity 4 and sinks into the surrounding sand layer 6, while flowing back to the sea surface 23 between the bodies 2 and along the upper surface of the body 2, and this process Sand is deposited in the cavity 4. A portion of the sediment in the cavity 4 is replenished into the space around the body 2 by the return water flow.

The weight of the porous foundation block 1 is evenly distributed and applied to the tapered outer surface 2a of the body 2, and as shown in FIG. 1, the distributed force acting in the vertical direction is F, If the angle between the generatrix of the outer surface 2a of the fuselage and the horizontal plane is θ, the outer surface 2a of the fuselage receives a drag force of F cos θ from the sand layer 6. Therefore, if the coefficient of friction on the surface of the body is μ, a frictional force f ₁ =μFcosθ is acting.

Furthermore, since the lateral pressure P from the sand layer 6 is acting on the body 2, it receives a drag force of Pcosθ from the sand layer 6 on the outer surface 2a of the body, and a frictional force f ₂ =μPcosθ acts on it. Since the lateral pressure P from the sand layer 6 is also acting on the vertically arranged shaft leg 3, the side surface of the shaft leg 3 receives a drag force P, and a frictional force q=μP acts on the side surface of the shaft leg 3.

The vertical component (f ₁ +f ₂ ) sin θ of the frictional forces f ₁ and f ₂ suppresses the sinking of the foundation block 1 together with the frictional force q. The pivot leg 3, which is vertically inserted deeply into the sand layer 6, together with the tapered outer surface 2a of the body 2 prevents the foundation block 1 from tilting to one side.

The porous foundation block laid in this way is
It is effective as the basic structure of civil engineering structures and buildings such as wave-dissipating blocks and embankments on the shores of coasts, lakes, marshes, and rivers, and as the basic structure of artificial fish reefs and seaweed cultivation structures on the seabed, lakes, marshes, and river bottoms. used for.

[Embodiment] In the embodiment shown in FIGS. 1 to 3, the fuselage 2
has an inverted truncated cone shape, and the shaft leg 3 integrally molded with the body 2 has a cylindrical shape, and a conical protrusion 10 is connected to the lower end of the shaft leg 3. The angle θ that the taper of the protrusion 7 makes with the horizontal plane between the generatrix of the side surface is the same as that of the outer surface 2a of the body, and the frictional forces f ₁ and f ₂ also act on the side surface of the protrusion 7, so that the base block 1 This increases the resistance to sinking.

The circular head 8 is constituted by a short cylindrical body having the same diameter as the large diameter portion at the upper end of the body 2, and a proximal bent portion of a hanging reinforcing bar 25 is provided protruding from the peripheral wall portion. Basic block 1
An injection hole 26 is provided in the center of the head 8, passing through the body 2 and the pivot leg 3 in the vertical direction to the protrusion 10.

When the foundation block 1 is lowered one by one with a construction machine such as a crane truck while a pressurized water stream mixed with pressurized air is ejected from the lower end opening of the injection hole 26 toward the sand layer 6, the pressurized water stream and air bubbles sand layer 6
is excavated efficiently, and the burying work of the foundation block 1 is performed accurately and efficiently. The injection hole 25 is also used as a passage for the return water flow of the waves.

In the installation mode shown in Figures 2 and 3, porous foundation blocks of the same size are used, and each foundation block 1, 1... is laid adjacent to each other in the front, back, left and right, and a jetty is installed at the beach's edge. It constitutes the basic structure for.

In the installation mode shown in FIG. 4, several types of porous foundation blocks 1, 1, . . . of different sizes are used. The largest foundation block 1 is laid in the center of the foundation structure, and the smallest foundation block 1 is laid at the front edge and left and right edges of the foundation structure, and from the center to the front edge and left and right edges. The basic blocks 1 are arranged so that the size of the basic blocks 1 decreases toward the end.

In the installation mode shown in FIGS. 5 and 6, in addition to the porous foundation block 1, a solid foundation block is provided in which a cylindrical shaft leg 13 is provided at the center of the lower end of a solid body 12 in the shape of an inverted truncated cone. 10 are used together. This solid type foundation block 10 is arranged at the main part of the foundation structure, and the porous type foundation block 1 is arranged at the front edge and left and right side edges of the foundation structure.

The installation mode shown in FIG. 7 uses a porous foundation block 1 in which a one-sided inclined surface 8a is provided on the upper surface of a circular or square head 8 of an inverted truncated cone or inverted truncated pyramid body 2. This foundation block is buried in the gently sloping surface 9 by vertically inserting the shaft leg 3 into the sand layer 6 of the gently sloping surface 9 of the coast, and the one-sided slope 8a is arranged along the gently sloping surface 9. Therefore,
A gently sloping revetment structure that is resistant to scouring by rushing water and returning water can be obtained.

In the case of this gently sloping seawall, a lid 20 is attached to the head 8 as shown in FIGS. If provided, it becomes suitable for walking and sitting.

In the embodiment described above, the through hole 5 penetrating the circumferential wall of the body 2 is formed as a tapered hole whose opening area decreases from the cavity 4 toward the outer surface 2a of the body, and the inflow from the upper surface of the cavity 4 is formed. Since the incoming water encounters resistance when flowing out from the through hole 5, the efficiency with which sand is deposited in the cavity 4 is improved.

In the above embodiment, the front, rear, left, and right foundation blocks 1, 1 are not particularly interconnected, but for example, by welding or restraining horizontal reinforcing bars and longitudinal reinforcing bars to the lifting reinforcing bars 25, 25, Alternatively, adjacent foundation blocks 1, 1 can be connected to each other by, for example, passing a connecting chain around the lifting reinforcing bars 25, 25.

This interconnection is an additional structure suitable for distributing overload loads, but as mentioned above, the basic block 1 of the present invention has self-sustainability and resistance to sinking due to its own shape and structure. , interconnection is a matter unrelated to the gist of the present invention.

Further, the shapes of the body 2, pivot legs 3, and head 8 are not limited to those shown in the drawings, and other shapes such as an ellipse, a quadrangle, a pentagon, a hexagon, and an octagon can be arbitrarily adopted. Assuming that the angle θ that the outer surface 2 of the body 2 makes with respect to the horizontal plane is 45 degrees, the frictional forces f ₁ , f ₂
The vertical component (f ₁ +f ₂ ) sin θ takes the maximum value, but the angle θ is not limited to 45 degrees and can be increased or decreased as appropriate.

As shown in FIG. 10, even in the normal type foundation block 1 which does not have a one-sided slope on the upper surface of the head 8, a drop-lid type or top-lid type lid body 20 is attached, so that the upper surface is on a horizontal surface. The formed lid body 20
A through hole 22 communicating with the cavity 4 of the body 2 can be provided in the body 2 .

Furthermore, in the porous foundation block 1 of the embodiment shown in FIG. Since the entire length from the upper end to the lower end is made up of a series of inclined surfaces, the dispersion and dissipation of wave force at the upper end of the body 2 is better compared to a foundation block with a cylindrical or square cylindrical head. Excellent action.

In the above embodiment, the through holes 5 are provided in an even distribution over the entire side surface of the body 2, but they may be provided unevenly, and the shape, size, and number of the through holes 5 may also be as shown in the drawings. It is not limited and can be changed as appropriate. The same applies to the through hole 22 provided in the lid body 20. Further, the through holes 5 may be provided only in the upper end portion of the body 2 or the head 8, and depending on the number of through holes 5 provided in the body 2 and the total opening area, the cover body 2
When using the cover body 20, the through hole 22 may not be provided.

[Effect of the invention] As described above, the underwater basic block of the present invention has the following effects:
A cylindrical or prismatic shaft leg 3 is provided at the center of the lower end of the inverted truncated cone or inverted truncated pyramid body 2, and a large number of through holes 5 are formed between the cavity 4 provided in the body 2 and the outer surface 2a of the body.
It is a hollow porous type connected with
The force of waves and water currents hitting around the body 2 is reduced in the process of reaching the inside of the cavity 4 from the through hole 5 of the body 2 and the upper surface opening of the cavity 4, so that the scouring effect on the sand layer around the body 2 is reduced. is suppressed. In addition, the cavity 4
During the process of the water flow flowing into the cavity 4 staying in the cavity 4, the sand carried by the water flow is deposited in the settled cavity 4, so a permeable packed layer 7 that is effective in reducing the force of the water flow is naturally formed. This will improve the scouring suppression efficiency.

In the underwater foundation construction method of the present invention, the permeable filling layer 7 is formed by storing gravel, crushed stones, etc. in the cavity 4 at the initial stage of laying the porous foundation block 1. Waves and water currents that hit the body pass through the permeable filling layer 7 in the cavity 4 through the through holes 5 in the body 2.
In the process of penetrating into the world, its power is further reduced, and
Since the sand is retained in the filling layer 7, the sand is deposited efficiently in the cavity 4, and even if some of the sand is washed away by waves, the permeable filling layer 7 is replenished appropriately by this sediment. . In addition, some of the sediment flows out of the through hole 5 with the return water flow and is returned to the area around the body 2, and is deposited around the body 2 to compensate for the loss of sand that has been washed away by the waves. According to the type foundation block 1, scouring is accurately suppressed, and the foundation blocks 1, 1...
The group is stably supported by the sand layer 6 for a long period of time without the risk of tilting or falling, and a solid foundation structure is constructed.

In another underwater foundation construction method of the present invention, when a foundation structure is constructed using the porous foundation blocks 1, 1... group, the porous foundation blocks 1 gradually increase from the center of the foundation structure toward the front edge and left and right side edges. Since the size of the sand layer is set small, the extreme dimensional discontinuity between the foundation structure and the sand layer is alleviated as much as possible, and the scouring phenomenon caused by waves and water currents can be further reduced or eliminated. I can do it.

In yet another underwater foundation construction method of the present invention, in addition to the porous foundation block 1, a cylindrical or prismatic shaft leg 13 is provided at the center of the lower end of a solid body 12 in the shape of an inverted truncated cone or inverted truncated pyramid. Since the solid type foundation block 10 is used in combination and the solid type foundation block 10 is placed in the main part of the foundation structure, the porous type foundation block 1 is placed at the front edge and left and right side edges of the foundation structure. In the main part of the foundation structure, the necessary and sufficient resistance to sinking is ensured by the solid foundation block 10 with no through holes opened on the outer surface 2a of the fuselage, while the front edge and left and right sides of the foundation structure At the edges, scouring is suppressed by the porous foundation blocks 1, and the solid foundation blocks in the main body are protected by the stable, self-supporting rows of porous foundation blocks, preventing subsidence and overturning. It is possible to build a strong underwater foundation structure that will not be washed away.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an underwater porous foundation block according to an embodiment of the present invention. FIG. 2 is a plan view showing the underwater foundation construction method of the present invention using the foundation block, and FIG. 3 is a front view of the foundation block in its installed state. FIG. 4 is a front view showing another underwater foundation construction method of the present invention using several types of porous foundation blocks of different sizes. FIG. 5 is a plan view showing another underwater foundation construction method of the present invention using both a porous foundation block and a solid foundation block;
The figure is a front view of the foundation block in its installed state.
FIG. 7 is a front view of the porous foundation block installed on a gently sloping surface, and FIG. 8 is a longitudinal sectional view of the foundation block equipped with a lid for a gently sloping surface.
FIG. 9 is a longitudinal sectional view of a foundation block fitted with another cover for gently sloping surfaces. FIG. 10 is a longitudinal cross-sectional view of a porous foundation block according to another embodiment of the present invention when the lid is attached, and FIG. 11 is a longitudinal cross-section of a porous foundation block according to still another embodiment of the present invention. It is a diagram. 1... Porous foundation block, 2... Body, 3...
... shaft leg, 4 ... hollow part, 5 ... through hole, 6 ... sand layer, 7 ... permeable packed layer, 8 ... head, 8a ...
Single flow slope, 9... Gentle slope on the coast, 10...
Projection, 11... Solid foundation block, 12... Body, 13... Pivot, 20... Lid body, 21... Single flow slope, 22... Through hole, 23... Sea level, 24
... Land surface, 25 ... Hanging reinforcing bars, 26 ... Pressurized water injection hole.

Claims (1)

[Scope of Claims] 1. A cylindrical or prismatic shaft leg 3 is provided at the center of the lower end of an inverted truncated cone or inverted truncated pyramid body 2, and the body 2
A porous foundation block for underwater use in which a cavity 4 provided in the body is connected to an outer surface 2a of the body through a large number of through holes 5. 2 A cylindrical or prismatic shaft leg 3 is provided at the center of the lower end of the inverted truncated cone or inverted truncated pyramid body 2, and the body 2
A porous foundation block 1 with a large number of through holes 5 communicating between the hollow part 4 provided in the body and the outer surface 2a of the fuselage is buried in a sand layer 6 with the pivot leg 3 vertically, and the hollow part 4 is filled with gravel or crushed stone. An underwater foundation construction method in which a permeable packed layer 7 is formed by accommodating such materials. 3 A cylindrical or prismatic shaft leg 3 is provided at the center of the lower end of the inverted truncated cone or inverted truncated pyramid body 2, and the body 2
When burying the porous foundation block 1, in which the hollow part 4 provided in the structure and the outer surface 2a of the body are connected through a large number of through holes 5, in the sand layer 6 with the pivot legs 3 vertical, it is necessary to An underwater foundation construction method in which the size of the porous foundation block 1 decreases toward the front edge and left and right side edges. 4 A cylindrical or prismatic shaft leg 3 is provided at the center of the lower end of an inverted truncated cone or inverted truncated pyramid body 2, and the body 2
A porous foundation block 1 has a plurality of through holes 5 communicating between a hollow portion 4 provided in the body and an outer surface 2a of the body, and a solid body 12 having a cylindrical or prismatic shape at the center of the lower end of the solid body 12 in the shape of an inverted truncated cone or an inverted truncated pyramid. When burying the porous type foundation block 1 and the solid type foundation block 10 in the sand layer 6 with the axle legs 3 and 13 vertically, the solid type This is an underwater foundation construction method in which the foundation block 10 is placed in the main part of the foundation structure, while the porous foundation blocks 1 are placed at the front edge and left and right side edges.