JPH0611982B2 - 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. Indeed, 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. 4, when it is used as a rubble mound 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.

An object of the present invention is to significantly reduce or suppress the generation of an eccentric lift due to the elliptic motion of water particles among the forces acting on the coating block arranged on the rubble mound, thereby coating in water. It is an object of the present invention to provide a covered block which prevents displacement and overturning due to insufficient weight of the block, and which can satisfy structural stability and economical efficiency during construction with a small and lightweight block.

[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 spoiler part having a shape with a lift reducing effect is formed on the upper surface of the block body. The exquisite structure has succeeded in solving the above-mentioned conventional problems 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. Besides, on the outer side surfaces of the opposing side walls 1c, 1c and 1d, 1d of the main body 1, this block B is used as a group of rubble mounds 1
When laid on the upper surface of No. 0, 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.

In general, when considering the stability of the coated block B installed on the rubble mound 10, when the horizontal flow velocity V due to waves acts on the block B as shown in FIG.
A lift force L and a drag force D, as shown by arrows, act on the arrow, and the magnitude of the lift force L 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, the cross-sectional shape of the object M and the lift L
As shown in Fig. 6 (a), since the upper surface of an object with a wing-shaped cross section is convex, the velocity of the fluid flowing on the upper surface increases and the pressure decreases. A large lift is generated, and Fig. 6 (b)
In the case of, lift is also likely to occur. Also, FIG. 6 (c) (d)
An object having an angle of attack with respect to the streamline as described above has its lift increased 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, and therefore it is used as one of the auxiliary wings for reducing the lift of an airplane or the like. Further, instead of the spoiler, the same spoiler effect can be expected also in the case of an object in which the intermediate portion of the upper surface is formed in a concave shape as shown in FIG. 6 (f).

The coated block of the present invention is based on the above reasons,
Forming a spoiler portion 2 having a shape that generates a negative lift on the upper surface of the main body 1 to roughen the streamline density on the upper surface of the covering block B to make it difficult to generate a lift, and rely only on the weight of the block. Instead, the stability of the covered block is ensured by means of increasing the downward force of the block in water by improving the lift coefficient. In this case, the shape of the spoiler portion 2 is not limited to the convex portion 2a having a trapezoidal cross section as in the above-described embodiment, but may be formed in a triangular or semicircular cross sectional shape, or a cross sectional shape combining these. ,
The spoiler portion 2 is formed only by the concave portion 2b provided in the intermediate portion of the upper surface of the main body 1, or the convex portion 2a and the concave portion 2b are formed.
It does not matter even if it is a combination type with.

The ratio of the height h of the convex portion 2a forming the spoiler portion 2 to the span is a numerical value depending on the magnitude of the wave force acting on the block B, the shape of the entire block, and the laying form thereof. Is not constant because it changes significantly, but from many test results, it is generally / h = 5 to / h =
Good results were obtained in the range of 30, especially / h =
About 10 shows the most preferable lift coefficient C _L = 0.17.

〔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.
A) If the lift coefficient and the drag coefficient of the coated block are checked beforehand by hydraulic experiments, the limit value of the required weight per block will be calculated from the predicted 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.

Demonstrate a number of excellent usage effects.

[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. The cross-sectional views of the main part, FIG. 6 (a), FIG. 6 (b), FIG. 6 (c), FIG. 6 (d), FIG. 6 (e) and FIG. 6 (f) are generally shown. It is sectional drawing which shows the relationship between the streamline which acts on a simple object, and lift. B, B1, B2, B3, B4 ... Coated block, 1 ... Block body, 2 ... Spoiler part, 2a ... Convex part, 2b ... Concave part, 3 ... Skirt part, 3a ... Spike part , 4 ... Through hole with taper, 10 ... Rubble mound

Claims (1)

[Claims] 1. A spoiler portion formed on a top surface 1a of a block body 1 by convex portions 2a, 2a extending in parallel to a pair of opposite ends and extending to the other opposite ends. 2 is provided, and the ratio of the height h of the spoiler portion 2 to the span is formed to be 1: 5 to 1:30.