JPH03262828A - Construction method for stabilizing marine structure - Google Patents

Abstract

PURPOSE:To enhance stability of a structure by installing the structure to the lower part of which nets are integrally fitted, on a primary rubble-mound which has been constructed on the bottom of the sea, and extending the nets around the structure, by constructing secondary rubble-mounds thereon. CONSTITUTION:A primary rubble-mound 1 is constructed on the bottom of the sea, and thereon, a structure 3 to the lower part of which nets 2 are integrally fitted is installed, and the nets 2 are extended around the lower part of the structure 3. And on the extended nets 2, secondary rubble-mounds 4 are constructed. As occasion demands, mats 5 are previously fitted to the peripheral parts of the nets 2, and when the secondary rubble-mounds 4 are constructed, the peripheral lower end parts thereof are positioned on the upper surface of the mats 5. Thus, sliding resistance against external forces can be inexpensively increased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for stabilizing a gravity-type marine structure for preventing sliding and stabilizing the marine structure.

<Problems with conventional technology> When constructing marine structures such as gravity breakwaters, it is important to prevent the structures from sliding due to external forces such as waves and earthquakes.
This is an important point in design and construction.

Therefore, conventionally, in order to obtain sliding resistance against external forces, the structure itself required a large weight.

In particular, in the case of submerged gravity-type structures, buoyancy acts on the entire volume of the structure, making it difficult to ensure the weight of the structure required for sliding resistance.

<Objective of the present invention> The present invention was made to solve the above-mentioned problems, and provides a method for stabilizing offshore structures that can ensure sufficient sliding resistance against external forces such as waves and earthquakes. The purpose is to provide.

<Means for solving the problem> That is, the present invention constructs a primary rubble mound on the seabed, installs a structure with a net integrally attached to the lower part of the primary rubble mound, and connects the net to the structure. This is a method of stabilizing offshore structures that is characterized by expanding the net around the bottom and building a secondary rubble mound on top of this expanded net.

In addition, in the above method for stabilizing offshore structures, a mat is attached in advance to the periphery of the developed net, and when constructing the secondary rubble mound, the lower end of the periphery of the secondary rubble mound is , is a method of stabilizing marine structures that is characterized by placing it on the top surface of a mat.

<Description of the present invention> The present invention will be explained in detail below.

<A> Installation of structure First, a primary rubble mound 1 is constructed on the seabed, and a structure 3 with a net 2 integrally attached to the lower part is installed on top of this primary rubble mound 1.

The net 2 has enough flexibility to fit the unevenness between the rubble stones,
It must also be made of a material (such as thin steel wire) that is strong enough to resist external forces such as wave force.

When attaching this net 2 to the lower part of the structure 3, when constructing the structure 3, the edge of the net 2 is embedded in the structure 3 in advance, or by fixing metal fittings and bolts, etc. Possible methods include attaching it to the outside surface of the

<Exposure> Deploying the net and constructing the secondary rubble mound Next, the net 2 is deployed on the surface of the primary rubble mound 1 and the seabed ground.

Then, stack rubble stones on top of this unfolded net 2,
A secondary rubble mound 4 is constructed to a predetermined height.

<C> Attaching the mat In addition to the above-mentioned construction method, as shown in FIG. 4, a mat 5 or a sheet is integrally attached to the peripheral edge of the unfolded net 2 in advance.

When constructing the secondary rubble mound 4, the lower end of the periphery of the secondary rubble mound 4 is constructed so as to be located on the upper surface of the mat 5 and the like.

<Action of the present invention> Next, the operation of the present invention will be explained.

<A> Transmission of rubble weight by the net (Figure 3) When an external force such as wave force a acts on the structure 3, the structure 3 tends to slide.

Against this wave force a, the weight of the structure 3 acts as a sliding resistance force through friction between the structure 3 and the group of rubble stones, and keeps the structure 3 stable.

In the present invention, a flexible net 2 integrated with a structure 3 is buried inside a group of rubble stones, and the uneven portions of the group of rubble stones and the net 2 are buried.
By meshing, a part of the force d of the own weight C of the rubble group can be transmitted to the structure 3 via the net 2.

Therefore, the effective weight of the structure 3 increases, and the sliding resistance e of the structure 3 increases.

<Exposure> Effect due to phase difference Generally, when the largest horizontal wave force a acts on the structure 3, the upward wave force f is dangerous for the stability of the structure 3.
acts.

However, since there is a phase difference between the wave forces acting on the structure 3 and the group of rubble, if the width of the secondary rubble mound 4 is sufficiently wide, while the upward force is acting on the structure 3, the group of rubble will A downward wave force acts on the structure 3, and an effective force is transmitted for the sliding stability of the structure 3.

<C> Function of the mat By installing the mat 5 or sheet outside the lower edge of the periphery of the secondary rubble mound 4 as shown in Fig. 4, it is possible to add a function as a scour prevention work. .

Mat 5 includes water-permeable prefabricated gravel mats, hand-woven synthetic fiber mats, asphalt mats, etc.
Both are suitable for construction.

In general, scour prevention work is carried out regardless of the increase in stability of the structure 3, so the cost of laying the net + mat is partially absorbed by the cost of the scour prevention work that should be carried out. There is no need for a significant cost increase.

<Effects of the Present Invention> Since the present invention has been described above, the following effects can be expected.

(a) In the construction of offshore structures, conventionally, the structure itself required a large weight in order to obtain sliding resistance against external forces.

In contrast, in the present invention, since the sliding resistance of the rubble is transmitted to the structure by the net, it is possible to ensure sufficient sliding resistance against external forces such as waves and earthquakes, and to stabilize the structure. can.

<Exposure> The present invention is particularly effective in preventing sliding of submerged gravity-type structures in which buoyancy acts on the entire volume of the structure.

<C> Since there is a phase difference between the wave forces acting on the structure and the group of rubble, when upward wave force acts on the structure, which is dangerous for the stability of the structure, downward wave force acts on the group of rubble. However, effective force transmission is performed for the sliding stability of the structure.

(2) By installing a mat or sheet attached to the periphery of the developed net outside the lower end of the periphery of the secondary rubble mound, a scour prevention function can be added.

Therefore, it can also serve as a scour prevention work, and a significant increase in construction costs can be suppressed.

[Brief explanation of drawings]

Figure 1.2 Figure 1 Explanation of the construction method of the present invention Figure 3 Explanatory diagram showing the effect

Claims (2)

[Claims] (1) Build a primary rubble mound on the seabed, install a structure with a net integrally attached to the bottom of the primary rubble mound, deploy the net around the bottom of the structure, and A stabilization method for offshore structures that consists of constructing a secondary rubble mound on top. (2) In the method for stabilizing offshore structures as set forth in claim 1, a mat or sheet is attached in advance to the peripheral edge of the developed net, and when constructing the secondary rubble mound, , a method for stabilizing offshore structures, characterized by positioning the lower edge of the periphery of the secondary rubble mound on the top surface of a mat or sheet.