JPH02252822A - Fill process of enclosed caisson - Google Patents

Abstract

PURPOSE:To prevent the internal pressure in a caisson from abrupt increase by enlarging a drain port and the bore of a drain pipe communicating thereto. CONSTITUTION:A caisson body 1 is formed of a top plate 2, a plurality of partition walls 3 and partitioned cells 4. The partitioned cells 4, 4 communicate to each other through a plurality of flow ports 5 opened. On the top plate 2 are provided pouring ports 6, 6, pouring pipes 7, 7 and a drain port 8 having the sectional area about 5 times that of pouring port 6 at the four corners. Next, each drain port 8 is connected to a drain pipe 9 erected vertically with the same bore as the drain port 8 and the end bent horizontally to be opened to the atmosphere. Thus, a abrupt contraction loss in the drain port portion can be reduced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used to construct a closed caisson installed at the bottom of the water with filler sand by water conveyance when constructing breakwaters, sea walls, etc. Regarding the filling method.

(Prior technology) Conventionally, water is injected into a hollow closed caisson and installed at a predetermined position on the water bottom, and filling sand is mixed with water into the caisson, made into a slurry, and pumped into the caisson. There is a known method of filling the tank by letting it settle and draining the excess water.

Generally, a caisson installed in a predetermined position needs to be filled as soon as possible to prevent it from being moved by waves or the like. For this reason, in order to increase the work efficiency, it is necessary to use a large pump to carry out filling work by conveying water into a closed caisson as described above. However, when filling rapidly with a large pump, the internal pressure of the caisson gradually increases as the amount of sand filling increases, and at the end of filling, the internal pressure suddenly rises and exceeds the allowable withstand pressure of the caisson. happen. For this reason, conventionally, a pressure relief pipe of a certain length was erected on the top plate or upper cover of the caisson, with the lower end released into the caisson and the upper end released outside.When the pressure inside the caisson exceeded a certain pressure, the water inside would overflow. A method is adopted to prevent the internal pressure from increasing any further.

(Problems to be Solved by the Invention) In the conventional method as described above, a large pressure relief pipe with a diameter of 1 m or more must be installed in addition to the slurry inlet and surplus water outlet. The problem was that the pressure relief pipe had to be removed and the opening in the top plate closed, requiring a lot of expense, labor, and time to install and remove the pressure relief pipe.

In view of the above-mentioned problems, the present invention is a method for filling a closed caisson, which prevents a sudden increase in pressure inside the caisson and enables efficient filling work by water conveyance without requiring any special management work or equipment. The purpose is to provide

(Means for Achieving the Object) A feature of the present invention for solving the above-mentioned conventional problems and achieving the intended purpose is that water is conveyed through a slurry inlet opened in the top plate of a closed caisson. A method for filling a closed type caisson in which filling sand is injected into the caisson, the filling sand is allowed to settle and separate within the caisson, and the conveyed water after the application sand amount M is discharged from the drainage port of the top plate while filling the caisson. In this method, the diameter of the drain port and the drain pipe connected to the drain port are set to a large diameter that has a small sudden loss in water pressure when flowing from inside the caisson into the drain port and the drain pipe, and the drain pipe is installed on or on the caisson. The idea is to open it to the atmosphere at a nearby location and create an open channel.

(Function) In general, the internal pressure at the final stage of sand filling in a closed caisson due to water conveyance is as follows: (1) Friction loss occurring in the flow path formed inside the caisson (2) The topmost communication port in the partition wall of the caisson Orifice loss when flowing (3) Rapid contraction loss when flowing from inside a wide caisson to a small outlet (4) Friction loss in the drain pipe when surplus water discharged from the caisson is sent back to the slurry forming part (5) Residual velocity head (6) The actual head of the water outlet for raising the water head to the water outlet at the tip of the drain pipe.Each of the factors (1) to (6) has a great influence.

In the present invention, since the diameters of the drain port and drain pipe are made large, the sudden contraction loss of the drain port mentioned in (3) above is reduced, and the drain pipe is made into an open channel at a position close to the caisson. The friction loss in the drainage pipe in the previous stage (4) is almost eliminated, and the actual head of the water outlet in the previous stage (6) is the same as the height of the drain pipe rising from the caisson, and is always constant, thereby reducing the overall pressure loss. This prevents a sudden increase in the internal pressure of the caisson at the end of filling.

(Example) Next, an example of implementation of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 denotes a caisson body which is filled by the method of the present invention.The upper surface of this caisson body 1 is closed by a top plate 2, and the inside has a large number of partition walls 3, 3...
A large number of compartments 4°4... are formed. Further, each partition wall 3 has a plurality of communication ports 5.5 opened at the top and center thereof, and the adjacent partitions 4.4 are communicated with each other.

The top plate 2 is provided with injection ports 6.6 at two locations in the center thereof for injecting slurry, and a slurry of sand and water is injected from the injection ports 6.6 through an injection pipe 7.7. ~
It is supplied at a flow rate of 41/S.

Discharge ports 8, 8, . . . for discharging surplus water are provided at the four corners of the top plate 2, respectively. The discharge port 8 is formed so that its cross-sectional area is about five times as large as the injection port 6.

A drain pipe 9 is connected to each discharge port 8, and the water is discharged through this drain pipe 9. This drain pipe 9 is
It is formed to have the same large diameter as the injection port 6, stands up vertically from the top plate 2, has its tip bent horizontally, and is exposed to the atmosphere at a position removed from the top of the caisson body 1. The water discharged from the tip of the drain pipe 9 is received in, for example, a water tank 10 and is returned via a pump 11 and a return pipe 12.

When filling the caisson constructed in this way, the injection port 6
The injected slurry passes from the compartment 4 where the inlet 6 is located, passes through the communication port 5 of the partition wall, passes through the adjacent compartment, and reaches the drain port 8. During this time, the filler sand 13 is sedimented and separated in each compartment 4, and the remaining water is drained from the drain port 8 through the drain pipe 9.

At this time, the diameter of the drain port 6 and the drain pipe 9 is approximately five times that of the inlet 5, and the number thereof is twice as large, so that the flow velocity at the rising portion 9a of the drain pipe 9 is approximately 5 times that of the inlet 5.
The flow velocity is 1710, that is, 0.4 to 0°2 n/s,
In the horizontal part 9b of the drain pipe 9, the water is discharged as an open channel with the upper part of the pipe open.

In this way, the filling sand 13 is accumulated one after another, and when the final stage of filling is reached and only the communication port 5 at the top of the partition wall 3 is opened, from the inlet 6 to the drain port as shown in FIG. A flow path a leading to 8 is formed.

At this time, the cross-sectional area of the flow path a that is formed gradually decreases, so the friction loss of the flow path within the geison increases, and the cross-sectional area of the flow path is narrowed at each of the uppermost flow ports 5 through which it passes. As a result, the distribution flow orifice loss increases.

However, since the drain port and drain pipe have a sufficiently large diameter, there is almost no sudden shrinkage loss at the drain port, and the horizontal part of the drain pipe is an open channel, so friction within the drain pipe is caused. There is almost no loss, and since the drainage port is open to the atmosphere near the caisson, the actual head is always a constant small value, and these factors combine to cause the caisson internal pressure to rise rapidly even at the end of sand filling. Filling is done without increasing the pressure.

(Effects of the Invention) As described above, in the method of filling a closed caisson according to the present invention, the diameter of the drain port and the drain pipe are made large, the drain pipe is opened to the atmosphere near the caisson, and the spill water is discharged as an open channel. By discharging water, the sudden contraction loss at the drain port is small, and even at the end of filling with filling sand, the pressure rise in the actual head of the drain pipe discharge is small, and the friction loss in the drain pipe is taken into account. This reduces fluctuations in the internal pressure of the caisson and simplifies work management.

[Brief explanation of drawings]

Fig. 1 is a 41 cross-sectional view of a caisson part showing an embodiment of the present invention, Fig. 2 is a cross-sectional view of a caisson in the final stage of filling with sand,
FIG. 3 is a cross-sectional view showing the state of the flow path. 1...Caisson body, 2...Top plate, 3
... Bulkhead, 4... Separate room, 5...
- Distribution port, 6... Inlet, 7... Injection pipe, 8... Drain port, 9... Drain pipe, 1
0... Water tank, 11... Pump, 12.
...Return pipe, 13...Filled sand. Figure 3

Claims (1)

[Claims] Filling sand is injected by water conveyance through a slurry inlet opened in the top plate of a closed type caisson, the filler sand is sedimented and separated within the caisson, and the conveyed water after separating the filler sand is transferred to the top plate. In a method of filling a closed caisson while discharging water from the drain port, the diameter of the drain port and the drain pipe connected to the drain port are suddenly reduced due to the pressure of water flowing from inside the caisson into the drain port and drain pipe. A method for filling a closed type caisson, characterized in that the drain pipe has a small large diameter, and the drain pipe is opened to the atmosphere at or near the caisson to form an open channel.