JPH0611984B2 - 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. 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 object of the present invention is to contribute to the reduction of the floating force of the coating block mainly due to the jet flow in the mound of the root fixing portion among the forces acting on the coating block arranged on the rubble mound, and the block body. By providing a through-hole having a peculiar shape in a part of the above, it is to provide a novel covered block that can exert an excellent effect in suppressing the floating force of the block and preventing the rubble stone from being sucked out.

[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 re-examining the above, and earnestly pursuing the optimum shape of the covered block for many years without depending only on the weight of the concrete block, the size of the cross-sectional area of water flow in the hole between the upper and lower surfaces of the block body A structure in which a tapered through hole is formed so as to become smaller as it goes upward, and a structure in which recesses that match between adjacent blocks are provided on the outer surfaces of the two pairs of opposing side walls of the main body, With the structure in which the notched portions that are obliquely cut off are formed at the four corners of the block body, 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 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 are arranged so as to project from the positions of the four corners at positions slightly shifted in the same peripheral direction. Also,
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. On the outer side surfaces of the opposite side walls 1c, 1c and 1d, 1d of the main body 1, the block B as a group is formed as a rubble mound 10.
When laid on the upper surface of the same, recesses 4a, 4a and 4b, 4b of the same shape are provided at mutually matching positions between adjacent blocks B, B.

As is well known, when an underwater structure 11 such as a breakwater by a concrete caisson is installed on the upper surface of the rubble mound 10 as shown in FIG. 5, the rubble mound 10 has a high porosity and permeability unlike the seabed ground. Therefore, at the time of the spill, a water level difference ΔH occurs inside and outside the levee body, and a water flow as shown by the arrow in the rubble mound 10 occurs. Therefore, the pore water pressure in the rubble mound suddenly increases. As a result, the levitation force due to the jet flow may act on the block B4 of the root solidification part, and conversely, when the wave is coming up, the pore water pressure increases from the offshore side to the inside of the slope of the rubble mound 10, The levitation force acts on the lower surface of the covering block 10.

As a means for coping with the above problem, in the coated 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, a tapered through hole is formed between the upper and lower surfaces 1a and 1b of the block B. 4 is provided 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 made slower at the lower surface portion than at the upper surface portion. It is constructed so that the stones can be reliably prevented from being sucked out.

In addition, as a means for supporting the above-mentioned effects, when a large number of covered blocks B are laid side by side on the rubble mound 10 as shown in FIG. The recessed portions 4 are formed on the outer side surfaces of the opposing side walls of
a, 4b are provided so that water also flows from the recessed portions 4a, 4b. By providing the tapered through hole 4 and the recessed portions 4a, 4b together, it is possible to reduce the pore water pressure in the rubble mound 10. It is designed to reduce the rise more reliably, prevent the covered block from floating due to the jet flow in the rubble mound, and ensure the stability of the block.

As a result of the experiment, the taper of the through hole 4 provided in the covering block is preferably such that the ratio of the water cross-sectional areas A1 and A2 of the upper and lower end surfaces is 1: 3 or less and the taper angle is 30 ° or less. , If the ratio is set to 1: 2, theoretically, the jet velocity will be reduced to 1/2 at the lower end, and the levitation force acting on the rubble will be 1
Since it can be reduced to / 4, it is effective in preventing the dumping of rubble stones.

Further, on the outer side surface of the covering block B, the above-mentioned recessed portion 4 is formed.
In addition to a and 4b, notches 4c formed by obliquely cutting off the four corners of the block body 1 are provided as shown in FIG. In any case, these through holes 4 and recessed portions 4a,
When a large number of covered blocks B are arranged side by side on the rubble mound 10, the holes 4b and the cutouts 4c are preferably arranged so that the holes are scattered as evenly as possible as a whole.

〔The invention's effect〕

As described above, when the covering block (including the root block) of the present invention is installed and used on the surface of the rubble mound that is the basis of a breakwater, etc., it has a tapered through hole in the central portion of the covering block and a concave side wall. The cutouts, cutouts, etc. are arranged in a substantially evenly distributed state, and the block itself has appropriate permeability, so the increase in the pore water pressure of the rubble mound is suppressed to a very small state. Since a local jet does not occur, there is no possibility that the rubble stone will be sucked out from the gap between the coated blocks. In addition, in the usual case, a rectangular block was installed around the levee body of the caisson breakwater as a foundation work, and it was unavoidable that the block easily floated or fell due to the jet flow from the rubble mound. However, if the coated block of the present invention is installed in the root fixing portion, these weak points can be eliminated 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.
Figure is a bottom view, Figure 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, etc., and Figure 5 is a cross-sectional view showing the state of jet flow in the rubble mound, FIG. 6 is a sectional view of an essential part showing a usage state of the coated block according to the present invention. B, B1, B2, B3, B4 ... Coated block, 1 ... Block body, 1a ... Top surface, 1b ... Bottom surface, 1c, 1d ... Opposing side wall, 2 ... Spoiler section, 3 ... Skirt section, 3a ... spike part, 4 ... tapered through hole, 4a, 4b ... concave part 4c ... notch part, 10 ... rubble mound, 11 ... underwater structure,

Claims (1)

[Claims] 1. Between the upper and lower surfaces 1a, 1b of the block body 1,
The ratio of the cross-sectional area of water in the upper and lower ends of the tapered through-hole is 1:
3 or less, and the taper angle is 30 ° or less, the two outer wall surfaces of the pair of opposing side walls 1c, 1c and 1d, 1d of the block body 1 are located between the adjacent blocks B, B respectively. The recesses 4a, 4a and 4b, 4b that are aligned with each other, and are cut off diagonally at the four corners of the block body 1.
A concrete covered block characterized in that c is formed.