JPH0611983B2 - 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 such as a breakwater as shown in FIG. An excellent acting force acts on each of the upper blocks in the following state depending on the arrangement position.

That is, the sliding force in the horizontal direction due to the wave action acts on the block B1 arranged at the bottom of the rubble mound 10 as shown by the dotted line arrow, and the block B at the slope and the shoulder part.
In many cases, an overturning force due to an eccentric lift force acts on B2 and B3, and an upward levitation force due to a jet flow in the mound acts on the block B4 at the root fixing portion.

In this case, the factors that greatly affect the stability of the block are mainly the physical weight of the block per unit area in water and the coefficient of friction of the bottom surface of the block against the rubble mound from the physical viewpoint. 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.

The purpose of the present invention is, among the forces acting on the coated block disposed on the rubble mound, mainly contributes to the improvement of the stability against the sliding force in the horizontal direction due to the pulling wave, etc. To provide a covering block with a structure that improves the familiarity with the surface of the rubble mound and arranges the streamline of the water flow that acts on the block to a smooth linear shape, thereby enabling a firm and immovable installation on the rubble mound. It is in.

[Structure of Invention]

(Means for Solving Problems) The coated block according to the present invention has been developed to achieve the above-mentioned object, and the characteristic of the coated block is fundamental from the viewpoint of hydrodynamics based on coastal hydraulics. As a result of earnestly investigating the optimum shape of the covered block for many years without depending only on the weight of the concrete block, a structure in which a skirt portion protruding downward is formed on the peripheral portion of the lower surface of the block body, With the structure in which the spike portions are provided at positions slightly displaced from the four corners of the lower surface of the skirt portion, the above-mentioned conventional problems have been successfully solved all at once.

(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. The main body 1 is provided with a spoiler portion 2 formed by a pair of convex portions 2a, 2a having a trapezoidal cross section, which are arranged in parallel at a pair of opposite ends and extend to the other opposite ends. The lower surface 1b of the skirt portion 3 is formed with a skirt portion 3 protruding downward along the peripheral edge thereof.
Each of the four spikes 3 protruding downward on the lower surface
As shown in FIG. 3, a is arranged so as to project from the positions of the four corners at positions slightly shifted in the same peripheral direction. 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 so that the cross-sectional area of water in the hole becomes smaller as it goes upward. In addition, two sets of opposing side walls 1c, 1c and 1 of the main body 1
On the outer surface of d, 1d, when the block B is laid on the upper surface of the rubble mound 10 as a group, the recesses 4a, 4a of the same shape are formed at the mutually matching positions between the adjacent blocks B, B. And 4b, 4b are provided.

Generally, in consideration of improving the stability of the coated block B against sliding, the magnitude of the hydraulic force (drag) 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) When the lift of the coated block B is taken into consideration The sliding resistance R of is expressed by the following equation.

R: Resistance force W: Weight in air of block μ: Coefficient of friction L: Lift force γ _c : Unit volume weight of block γ _ω : Unit volume weight of fluid (seawater) Therefore, sliding from the above equations (1) and (2) The stability condition of the block for is expressed as

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 the buoyancy and the lift force due to the seawater are subtracted, and therefore the lift coefficient C _L of the spoiler portion 2 on the upper surface of the coated block B is The reduction is also an important factor for improving the stability of the block against sliding, but in this section, mainly in the part related to the improvement of the drag coefficient C _D and the friction coefficient μ of (2) and (3). The structure and its effects will be explained.

That is, considering the relationship between the rubble mound 10 and the covered block B installed on the upper surface of the rubble mound 10 with respect to an example in which a normal rectangular block is installed (FIG. 5), the installation posture of the block B is equal to that of the rubble mound 10. 5 (a), (b), and (c) are larger depending on the state, but in the case of FIGS. 5 (b) and (c), the projected area for running water is larger than that in FIG. 5 (a). Therefore, the drag D due to the flow increases and the block B
Is slippery, especially in the case of FIG. 5 (c), not only it sways like a seesaw, but also the underwater weight decreases due to the rapid increase in the lift L as the angle of attack increases, so it is even easier to slide. There is also a risk of falling.

On the other hand, in the coated block B according to the present invention, the main body 1
Since the skirt portion 3 projecting downward is formed on the peripheral portion of the lower surface, and the spike portions 3a are respectively provided at positions slightly deviated from the four corners on the lower surface of the skirt portion 3 in the same peripheral direction, the rubble mound 10 When the covering block B is installed on the upper side as shown in FIG. 6, since the concave portion 3b surrounded by the skirt portion 3 is formed on the bottom surface of the covering block B like a bowl bottom of the bowl, the concave and convex portions are formed. Even in a large number of places, it is well-suited to the rubble mound 10, and the surrounding skirt part 3 is installed in a state of properly abutting the upper surface of the rubble mound 10 as shown in FIG. 6 (a). Even if the skirt portion 3 is supported on a portion of the rubble material and is supported at a slight angle, the force of the waves often shifts to the state shown in FIG. , On the upper surface of rubble mound 10 A very high probability of being installed in the boss was attitude.

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, since the spike portion 3a is provided on the lower surface of the skirt portion 3, when the covering block B is installed, each spike portion 3a protrudes into the rubble mound 10 as shown in FIG. Since a friction coefficient can be obtained and an anchoring effect such as anchoring can be expected, strong stability can be secured by using the skirt portion 3 together. In particular, the positions of the spikes 3a are arranged at positions slightly deviated from the four corners of the lower surface of the skirt 3 in the same peripheral direction as shown in FIG.
When arranged as a colony, the spike part 3 of each block
Since the a's are arranged adjacent to each other in a dispersed position without being matched with each other, the a's are surely rushed into the rubble mounds 10 existing around the spike portions 3a to exert a more effective locking effect. be able to.

〔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.
If applied to the rubble mound surface, the skirt provided at the bottom of the block body and the spikes protruding from the four corners of the bottom of the skirt slightly offset in the same peripheral direction during the construction of the coated block At the same time, the water flow acting on the block is prevented from flowing into the bottom of the block, and moreover, it is possible to securely lock the rubble mound and to install the covering block firmly and immovably in a stable state. In combination with the fact that a small block can counter a large wave force, it exerts a remarkable use effect.

[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.
The figure is a bottom view, and FIG. 4 is a cross-sectional view showing the direction of the force acting on the block installed on the rubble mound that is the foundation of the breakwater, FIG. 5 (a), FIG. 5 (b) and FIG. 5 (c). ) Is a cross-sectional view showing a posture when a normal rectangular block is installed on a rubble mound, and FIGS. 6 (a), 6 (b) and 6 (c) are rubble mounds of the coated block of the present invention. It is a sectional view showing a posture when installed above. B, B1, B2, B3, B4 ... Coated block, 1 ... Block body, 2 ... Spoiler part, 3 ... Skirt part, 3a ... Spike part, 3b ... Recessed part, 4 ... Tapered penetration Hole, 10 ... Rubble mound,

Claims (1)

[Claims] 1. A skirt portion (3) projecting downward is formed on a peripheral portion of a lower surface of a block body (1), and a spike portion (3a) is projectingly provided under the skirt portion (3) and the spike portion (3a).
Are provided at positions slightly deviated from the four corners of the lower surface of the skirt portion 3 in the same peripheral direction, respectively.