JPS6135030B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floating mooring device in shallow water.

If a floating body is moored in shallow water and against large wave heights, the mooring line will easily become strained and generate a large impact force, creating the risk of breakage. There was a limit to what was possible.

The concept of conventional floating body mooring will be explained below with reference to the drawings. When the floating body 1 is stationary, an initial tension T ₀ due to the weight of the mooring line 2 is acting on the mooring line 2 (FIG. 1). Note that 5 indicates a basic sinker. Next, the floating body 1 moves by x ₁ from the resting position A to the average position B by the steady horizontal force F ₁ (tidal current force, drifting force due to small waves, and blowing force). At this time, a new tension T ₁ corresponding to F ₁ is applied to the mooring line 2 (Fig. 2). Furthermore, due to the particle motion of the wave having the designed maximum wave height, the floating body 1 fluctuates by ±x ₂ around the average position B. A horizontal force F ₂ due to wave particle motion acts on the floating body 1, and a corresponding tension T ₂ is applied to the mooring line 2 (third
figure).

This relationship is illustrated in FIG. 4. In the figure, F indicates horizontal force, x indicates horizontal movement distance, and T indicates mooring line tension.

The point of mooring design is to change the maximum movement position C to the allowable large movement position D (as shown by the broken line in Figure 3, the mooring line 2 is tensed, and as shown in Figure 4, the horizontal force F is
and the position where the mooring line tension T becomes infinite) to avoid generation of impact force due to tension in the mooring line 2. That is, the idea is to avoid the force caused by waves by moving the floating body 1.

This movement of the floating body 1 is caused by slack in the initially set mooring line 2. Furthermore, the weight of the mooring line 2 acts as a resistance force against the movement of the floating body 1.

However, with the above mooring method, the movable horizontal distance x ₀ (distance from the stationary position A to the maximum allowable movement position D) cannot be made large, so it is difficult to avoid the movement of the floating body 1 due to particle movement of waves with large wave heights. The mooring line 2 is easily strained and generates a large impact force.

For this reason, a mooring method can be considered in which the slack of the mooring line 2 is increased (FIG. 5) in order to increase the movable horizontal distance _x0 .

FIG. 6 is a diagram of the mooring characteristic curve, and as is clear from this figure, mooring method A allows a larger movable horizontal distance x ₀ than mooring method D described above. but,
Since the rising slope of the characteristic curve is gentle, the horizontal movement distance x ₁ is large for a steady horizontal force F ₁ of the same magnitude, and the distance x ₃ to the maximum allowable movement position D does not remain very large. In other words, in a loose mooring, the mooring line 2 stands almost vertically under the floating body 1 when it is stationary, so there is almost no resistance against the horizontal force F, and the mooring line moves horizontally. There's only so much distance left to travel before you get nervous. As described above, it has been extremely difficult to moor floating bodies in shallow water.

The present invention is an attempt to solve the above-mentioned problems, and is a method for mooring a floating body in shallow water to avoid the generation of a large impact force by allowing the movement of the floating body due to waves of large wave height to escape without straining the mooring line. The purpose is to provide equipment.

Therefore, the shallow water depth floating body mooring device of the present invention is a floating body moored on the ocean by a plurality of cables, the cables are composed of a mooring line and an auxiliary mooring line, and one end of the mooring liner is attached to the floating body. , the other end is attached to the foundation sinker, and the mooring is loose with a large amount of slack when the floating body is stationary, and the intermediate sinker is fixed to the rising point of the mooring line.
The auxiliary mooring line is stretched between the intermediate sinker and the floating body, and is characterized by having greater elasticity than at least the mooring line.

Below, a floating body mooring device at shallow water depth as an embodiment of the present invention will be explained with reference to the drawings. This is the mooring line. The intermediate sinker 4 is provided at the rising point of the mooring line 2 on the offshore side, and the auxiliary mooring line 3 is stretched almost in a straight line between the intermediate sinker 4 and the floating body 1. The mooring line 2 is made of a material with low elasticity, such as a steel chain, and the auxiliary mooring line 3 is made of a material with high elasticity, such as a nylon rope.

With this configuration, when a steady horizontal force F ₁ acts on the floating body 1, the intermediate sinker 4 that is on the bottom
temporarily plays the role of a foundation sinker, and the auxiliary mooring line 3 mainly provides resistance to prevent the floating body 1 from moving significantly horizontally (in the initial state, the auxiliary mooring line 3 is taut, and the mooring line 2 is loose). ). After the length of the auxiliary mooring line 3 becomes the same as the length of the mooring line 2, the mooring line 2 begins to resist the steady horizontal force _F1 . Auxiliary mooring line 3
does not extend beyond the length of the mooring line 2 (the length between the intermediate sinker 4 and the floating body 1), so no further tension is applied. If the difference in length between the mooring line 2 and the auxiliary mooring line 3, that is, the extension of the auxiliary mooring line 3, is designed to be within the elastic limit of the auxiliary mooring line 3, no matter how large the force is applied to the mooring line, the auxiliary mooring will continue. Line 3 will not creep or break.

Next, when a horizontal force F ₂ due to particle movement of a larger wave is added to the steady horizontal force F ₁ , the intermediate sinker 4 lifts from the water bottom, exerts the effect of increasing the weight of the mooring line 2, and resists the horizontal force. To reduce the horizontal movement of the floating body 1.

This function is illustrated in FIG. 8. In the figure, (a) shows the case of loose mooring using only the mooring line 2, and (b) shows the case where intermediate sinker 4 is added to (a). C shows the case where the auxiliary mooring line 3 is added to B (characteristic curve of the present invention), O to P is the part where the auxiliary mooring line 3 is effective, and P is the lifting point of the intermediate sinker 4. It shows. As is clear from this figure, the horizontal movement distance x ₁ of the floating body 1 due to the steady horizontal force F ₁ is greatly reduced, and the distance x ₃ to the maximum allowable movement position can be increased.

As described above, the shallow water mooring device of the present invention has the advantage that generation of a large impact force can be avoided and the floating body can be stably moored for a long period of time.

[Brief explanation of the drawing]

1 to 3 are side views showing the state in which the floating body moves horizontally in a conventional mooring method, FIG. 4 is a mooring characteristic curve diagram, and FIG. 5 is a side view showing another conventional mooring method. FIG. 6 is a mooring characteristic curve diagram thereof, FIG. 7 is a side view showing a mooring method using a mooring device as an embodiment of the present invention, and FIG. 8 is a mooring characteristic curve diagram thereof. 1...Floating body, 2...Mooring line, 3...Auxiliary mooring line, 4...Intermediate sinker, 5...Foundation sinker, F...Horizontal force, T...Mooring line tension, x...
...Horizontal movement distance.

Claims (1)

[Claims] 1. In a floating body moored at sea by multiple lines, the cables consist of a mooring line and an auxiliary mooring line, one end of which is attached to the floating body, the other end is attached to the foundation sinker, and the mooring line is attached to the floating body at one end, and the other end is attached to the foundation sinker. Sometimes the mooring is loose with a lot of slack, and an intermediate sinker is fixed at the rising point of the mooring line.
A floating body mooring device at shallow water depth, wherein the auxiliary mooring line is stretched between the intermediate sinker and the floating body and has at least greater elasticity than the mooring line.