JPH0611981B2 - Concrete covered block - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial field of application) The present invention is constructed by rubble stones when using rubble stones for the foundation of various coastal and undersea structures such as breakwaters. The present invention relates to a concrete covering block (including a root block) that covers the surface of the rubble mound to protect the rubble mound from the waves.

(Prior Art) Conventionally, in addition to the rectangular block generally referred to as a square block, this type of concrete block has various contrivances for meshing and connecting means between blocks as a group, or a wave block. Some of them have a wave-dissipating function for the purpose of absorbing energy.The shapes of these irregular blocks include, for example, tetrapots and hexapod blocks, X-blocks, hollow triangular blocks, holoscare blocks, and tribers. In fact, more than 100 kinds of products are already on the market.

(Problems to be solved by the invention) However, when the conventional concrete block is used as a covering block on the surface of a rubble mound that is a base of an underwater structure 11 such as a breakwater as shown in FIG. Each block on the mound has a different acting force depending on its arrangement position as follows.

That is, the block B1 placed at the bottom of the rubble mound 10
, The sliding force in the horizontal direction due to the pulling wave acts as shown by the dotted arrow, and the blocks B2 and B3 on the slope and shoulder have a fall force due to the eccentric lift as shown by the arrow. A levitation force upward due to the jet flow in the mound often acts on the block B4 of the root fixing portion.

In this case, the factors that greatly affect the stability of the block are, from a physical point of view, the weight of the block per unit area in water and the coefficient of friction of the bottom surface of the flock against the rubble mound. It is considered that this is a major factor. However, the conventional coated block is a means for counteracting the above-mentioned acting force.
Basically, all of them depend on the weight of the block itself, and the stability of the block is ensured by its own weight, so the size of underwater structures such as breakwaters is becoming larger and larger in recent years. The rubble mound covering block used for this is gradually increasing in size, and the size and weight of each block are dramatically increasing. Therefore, a large amount of construction cost is required for manufacturing and laying the block, and it is lightweight and lightweight. It has become difficult to take full advantage of the original advantages of concrete blocks that are inexpensive and easy to construct.

In order to deal with the above problems, the present invention fundamentally reexamines various characteristics of the coated block from the viewpoint of hydrodynamics based on coastal hydraulics, and as a result of pursuing its optimum shape for many years, Developed by a new technical idea, the coating block placed on the rubble mound, the action force that is expected to occur when a severe wave that cannot be coped with by a commercially available block at all is predicted, For example, the coated block has the function of maintaining firm stability against all the acting forces such as the falling force due to the eccentric lift mentioned above, the sliding force due to the drag wave, and the levitation force due to the jet in the mound. The purpose of the present invention is to realize a light weight and small size structure by the hydrodynamic characteristics without depending only on the own weight of the block.

[Structure of Invention]

(Means for Solving Problems) As a structure for achieving the above object, in the concrete covered block of the present invention, on the upper surface of the block main body,
A spoiler section is provided that is formed in parallel with a pair of opposite ends and extends to the other opposite ends, and has a spoiler section that projects downward on the peripheral edge of the lower surface of the block body. A skirt portion is formed, and on the lower surface of the skirt portion, spike portions that are respectively arranged at positions slightly deviated from the four corners of the lower surface of the skirt portion in the same peripheral direction are projected, and It is characterized in that a tapered through hole is formed in which the cross-sectional area of water passage becomes smaller as it goes upward, and further, recessed portions that match between adjacent blocks are provided on the outer surfaces of the two opposite side walls of the block body. And

(Embodiment) The present invention will be described below in detail with reference to the drawings of the embodiments. FIG. 1 shows an example of the most typical implementation structure of a covering block according to the present invention, which is an upper surface 1a of a block body 1. Of the trapezoidal section 2 which is provided in parallel with a pair of opposite ends and extends to the other opposite ends.
The spoiler part 2 formed by a and 2a is provided,
The lower surface 1b of the main body 1 is formed with a skirt portion 3 projecting downward along the peripheral edge thereof, and each of the lower surfaces of the skirt portion 3 has a spike portion 3a projecting downward, as shown in FIG. It is arranged so as to be slightly displaced from the four corners in the same peripheral direction and is projected. Further, between the upper and lower surfaces 1a and 1b of the main body 1, there are provided a pair of tapered through holes 4 and 4 formed such that the cross-sectional area of water in the hole becomes smaller as it goes upward. In addition, when the block B is laid on the upper surface of the rubble mound 10 as a group on the outer surfaces of the two opposite side walls 1c, 1c and 1d, 1d of the main body 1, the blocks B, B adjacent to each other Recessed portions 4a, 4a and 4b, 4b having the same shape are provided at positions that coincide with each other.

Generally, coated block B installed on rubble mound 10
When the flow velocity v of the horizontal flow due to the wave acts on the block B as shown in FIG. 5, the lift L and the drag D as shown by the arrow act on the block B, and the magnitude of the lift L is considered. Is expressed by the following equation.

w: aerial weight of block g: acceleration of gravity A: flat area of block γ _ω : unit volume weight of sea water γ _c : unit volume weight of concrete C _L : lift coefficient L: lift D: drag And counter this The force is the weight of the block in water Only.

Therefore, as means for ensuring the stability of the block B, (a) ... The specific gravity of concrete or the thickness of the block is increased.

(B) ... The shape of the block is improved to reduce or prevent the lift coefficient C _L.

There are two possible methods.

From the above viewpoint, looking at the relationship between the cross-sectional shape of the object M and the lift, as shown in FIG. 6 (a), an object with a wing-shaped cross section has a convex upper surface. The velocity of the fluid flowing on the upper surface is increased, the pressure is reduced, and a large lift is generated, and the lift is likely to be generated in the case of FIG. 6 (b) as well. Further, as shown in FIGS. 6 (c) and (d), the lift of an object having an angle of attack with respect to the streamline increases in proportion to the angle. It is for this reason that the protrusions on the lower surface of the block B are likely to fall.

On the other hand, when the spoiler S is erected on the upper surface of the wing as shown in FIG. 6 (e), the lift is reduced, so that it is used as one of the auxiliary wings for reducing the lift of an airplane or the like. Also, instead of the spoiler, the middle part of the upper surface is shown in FIG.
The same spoiler effect can be expected also when it is formed in a concave shape as shown in (f).

One of the features of the coated block according to the present invention is that the spoiler portion 2 having a shape having a lift reducing effect is formed on the upper surface of the main body 1 for the above-mentioned reason, and the coated block B
The streamline density on the upper surface is made rough to make it difficult to generate lift,
The point is that the stability of the coated block is improved by means of increasing the underwater weight of the block by improving the lift coefficient without depending only on the own weight of the block.

Next, considering the improvement of the stability of the coated block B against sliding, the magnitude of the hydraulic force (drag force) acting on the block B is expressed as follows.

D: drag force S: projected area in flowing water direction C _D : resistance coefficient V: flow velocity γ _ω : unit volume weight of seawater g: acceleration of gravity ε: shielding coefficient (0.4) In addition, sliding when the lift of the coated block B is considered The resistance R is expressed by the following equation.

R: Resistance W: Weight of air in block μ: Coefficient of friction L: Lift force γ _c : Weight of unit volume of block Therefore, from the above equations (2) and (3), the stability condition of the block against sliding is expressed as follows. Be done.

R> D As described above, the shape characteristic value of the coated block that contributes to stability is obtained by (1) lift coefficient C _L → small (2) drag coefficient C _D → small (3) friction coefficient μ → large.

In this case, the resistance weight of the block in the seawater when the running water by the wave acts depends on the value after subtracting the buoyancy and the lift force by the seawater. Therefore, the lift force by the spoiler part 2 on the upper surface of the coated block B described above is increased. The reduction of the coefficient C _L is also an important factor for improving the stability of the block against sliding, but in this section, the parts mainly related to the improvement of the drag coefficient C _{D of a} few and the friction coefficient μ are described. The structure and its effects will be explained.

That is, the relationship between the rubble mound 10 and the covering block B installed on the upper surface of the rubble mound 10 is examined as to an example in which a normal rectangular block is installed (Fig. 7). Figure 7 (a) (b) depending on the condition
In most cases, the posture is as shown in (c), but in the case of Fig. 7 (b) (c) compared to Fig. 7 (a), the projected area for running water is large, so the drag force D due to the flow increases. As a result, the block B becomes slippery easily. Especially, in the case of FIG. 7 (c), not only does it move like a seesaw, but the lift force L increases as the angle of attack increases.
Since the underwater weight decreases due to the sudden increase in the water content, it becomes even easier to slide, and in some cases there is a risk of falling.

On the other hand, in the covered block B according to the present invention, the skirt portion 3 protruding downward is formed on the peripheral portion of the lower surface of the block body 1, and the skirt portion 3 is slightly displaced from the four corners in the same peripheral direction. Since the spike portions 3a are respectively provided on the ridges 3, when the covering block B is installed on the rubble mound 10 as shown in FIG. 8, the skirt portion 3 is formed on the bottom surface of the covering block B like a bowl bottom. Since the concave part 3b surrounded by is formed, it fits well with the rubble mound 10 even in a place with a lot of irregularities, and the surrounding skirt part 3 is installed in a state where it abuts correctly as shown in Fig. 7 (a). Even if the skirt portion 3 is supported on a part of the rubble material as shown in FIG. 8 (b) and is supported at a slight angle, the force of the wave shifts to the state of FIG. 8 (a). The top surface of the rubble mound 10 Very likely to be installed in a stable posture.

Therefore, in the covered block B of the present invention, the strong water flow from the peripheral portion of the lower surface of the main body 1 is prevented from flowing into the bottom portion of the block B by the skirt portion 3 to suppress the generation of lift and increase the underwater weight of the block. Of course, the friction coefficient μ with the rubble mound 10 can be increased to prevent the block from swaying and sliding, and the stability can be significantly improved. Further, the spike portions 3a arranged on the lower surface of the skirt portion 3 are arranged in the manner shown in FIG.
As shown in (c), it is possible to get into the inside of the rubble mound 10 to obtain a larger friction coefficient and to expect a locking effect like an anchor. It can be secured. In particular, the spikes 3a are arranged at positions slightly displaced from the four corners of the lower surface of the skirt 3 in the same peripheral direction as shown in FIG. 3, so that a large number of blocks B are grouped together. If arranged as, since the spike portions 3a of each block are arranged adjacent to each other in a dispersed position without matching, surely rush into the rubble mound 10 present around each spike portion 3a. Further effective locking effect can be exhibited.

Next, as shown in FIG. 9, when an underwater structure 11 such as a breakwater by a concrete caisson is constructed on the upper surface of the rubble mound 10, the rubble mound 10 has high porosity and permeability unlike the seabed ground. Therefore, at the time of the spill, a water level difference ΔH will occur inside and outside the levee body, and a water flow will occur inside the rubble mound 10 as shown by the arrow, so the pore water pressure in the rubble mound will rise rapidly. In particular, the levitation force due to the jet flow may act on the block B4 of the root block, and conversely, when the wave is coming up, the pore water pressure increases from the offshore side to the slope of the rubble mound 10 and the covered block B4 The levitation force acts on the lower surface of.

As a means for coping with the above-mentioned problem, in the covered block B of the present invention, in order to suppress an increase in pore water pressure generated inside the rubble mound 10 due to waves, the upper and lower surfaces 1 of the block B are covered.
A tapered through hole 4 is provided between a and 1b to reduce the upward force acting on the block B, and the flow velocity of water passing through the inside of the through hole 4 from the lower surface to the upper surface is lower than that of the upper surface. It is also designed to be slow, so that it is possible to reliably prevent the rubble stone from being sucked out. In addition, as a means to support the above-mentioned effects, rubble mound
When a large number of covered blocks B are laid side by side as shown in FIG. 10 on the 10 to maintain a predetermined gap between the blocks, the outer side surfaces of the opposite side walls of the block B are
The recessed portions 4a and 4b are provided at the matching positions between the adjacent blocks, and the water is allowed to flow also from the recessed portions 4a and 4b. The tapered through hole 4 and the recessed portion 4a, By installing 4b together, the rise of pore water pressure in the rubble mound 10 can be reduced more surely, the floating of the coated block due to the jet flow in the mound can be prevented, and the stability of the block can be secured.

The taper provided on the coated block was
It is preferable that the ratio of the water flow cross-sectional areas A1 and A2 on the upper and lower end surfaces is within 1: 3 and the reduction angle is within 30 °. If the ratio is set to 1: 2, theoretically, , The jet velocity can be reduced to 1/2 at the lower end, and the levitation force acting on the rubble can be reduced to 1/4, which is effective in preventing the rubble material from being sucked out.

〔The invention's effect〕

As described above, the present invention provides a rubble mound covering block (including a root block) provided on a foundation such as a breakwater.
When applied to, it exhibits various use effects as listed below.

B) If the lift coefficient, drag coefficient, friction coefficient, etc. of the covered block are investigated in advance by hydraulic experiments, the limit value of the required weight per block is calculated from the predicted calculation value of the flow velocity distribution at the planned installation point. Therefore, the coated block can be easily designed.

(B) The coated block is economical because a block having a small lift coefficient can be used for the same wave height and a light weight can be used.

C) Since the thickness (height) of a light-weight coated block also becomes thinner in proportion to the weight, the depth of water on the top surface of the rubble mound becomes deeper, and therefore the wave pressure strength to the breakwater is weak and the required weight of the breakwater. Is also small, which helps to reduce the total construction cost.

D) The skirt and spikes provided at the bottom of the block main body improve the familiarity with the surface of the rubble mound, and prevent the water flow that acts on the block from flowing into the bottom of the block, ensuring that it is on the rubble mound. It can be locked and the covering block can be installed firmly and immovably and stably.

E) The coated block has tapered through holes, recesses, etc. arranged almost evenly and the block itself has appropriate permeability, increasing the pore water pressure of the rubble mound. Is suppressed to a very small amount, and a local jet flow is not generated, so there is no possibility that the rubble stone will be sucked out from the gap between the coated blocks.

F) In the normal case, around the levee body of the caisson type breakwater,
A rectangular block is installed as a foundation work, and it was unavoidable that the block is likely to float and fall due to the jet phenomenon from the rubble mound, but if the coated block of the present invention is installed in the foundation part, these The weaknesses of can be solved at once.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a concrete embodied structure of a coated block according to the present invention, FIG. 2 is a central longitudinal sectional view thereof, and FIG.
Fig. 4 is a bottom view, Fig. 4 is a cross-sectional view showing the direction of the force acting on the block installed on the rubble mound that forms the basis of the breakwater, etc., and Fig. 5 shows the relationship between the drag force acting on the block and the lift. Sectional view of the main part, FIG. 6 (a), FIG. 6 (b), FIG.
(c), FIG. 6 (d), FIG. 6 (e), and FIG. 6 (f) are cross-sectional views showing the relationship between streamline acting on a general object and lift, FIG.
(a), FIG. 7 (b) and FIG. 7 (c) are sectional views showing the posture when a normal rectangular block is installed on a rubble mound, FIG. 8 (a) and FIG. 8 (b). And FIG. 8 (c) is a sectional view showing the posture when the covering block of the present invention is installed on the rubble mound, FIG. 9 is a sectional view showing the generation state of the jet flow in the rubble mound, and FIG. 10 is the present invention. FIG. 6 is a cross-sectional view of the main parts showing the usage state of the covered block according to FIG. B, B1, B2, B3, B4 …… Coating block, 1 …… Block body, 1a …… Upper surface, 1b …… Lower surface, 1c, 1d …… Opposing side wall, 2 …… Spoiler part, 2a …… Convex part 3 ... Skirt part, 3a ... Spike part, 4 ... Tapered through hole, 4a, 4b ... Recessed part 10 ... Rubble mound, 11 ... Underwater structure,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Hasegawa 2570 Wakaguri, Kurobe City, Toyama Prefecture (72) Inventor Kazuyuki Tsubota 5-23, Okuicho, Toyama City, Toyama Prefecture (56) References 52344 (JP, U) Actual development 57-133622 (JP, U) Actual public 35-29931 (JP, Y1)

Claims (1)

[Claims] 1. A spoiler formed on a top surface 1a of a block body 1 by convex portions 2a, 2a which are arranged in parallel at a pair of opposite ends and extend to the other opposite ends. The block body 1 is provided with a skirt portion 3 projecting downward at the peripheral edge of the lower surface 1b of the block body 1. The lower surface of the skirt portion 3 is slightly displaced from the four corners of the lower surface of the skirt portion 3 in the same peripheral direction. Spikes placed in different positions
3a is projectingly provided, and a tapered through hole 4 is formed between the upper and lower surfaces 1a and 1b of the block body 1 so that the cross-sectional area of water in the hole is increased upward, and two sets of the block body 1 are opposed to each other. Concave cutouts 4a, 4a and 4b, 4b that match the outer surfaces of the side walls 1c, 1c and 1d, 1d between adjacent blocks B, B, respectively.
A concrete coated block characterized by being provided with.