JPH0313628A - Sinking method for open caisson and device thereof - Google Patents

Abstract

PURPOSE:To prevent over-sinking and economically sink a caisson body by pressing the lower face of a reaction plate to the ground to obtain the reaction force from the ground, sinking the caisson body, then introducing pre-stress via lowering steel wires. CONSTITUTION:Center haul jacks 33 are operated, and a reaction plate 2 in a caisson body 1 is located on the soft ground 6 via hoisting PC steel wires 3. Center haul jacks 45 are operated, the upper sections of lowering PC steel wires 4 are pulled downward, the lower face of the reaction plate 2 is pressed to the surface of the soft ground 6 to obtain the reaction force, and the caisson body 1 is sunk to the preset depth. Lowering steel wires 4 are cut in the middle, and cut lower end sections are fixed to the caisson body 1 with a fixing agent. Upper sections of lowering steel wires 4 are pulled upward by center haul jacks 45 to introduce the required pre-stress to the caisson body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an open caisson sinking method and an apparatus therefor.

<Conventional technology> Generally, if there is a risk of transient subsidence occurring when an open caisson is sunk on the seabed, the island construction method is often adopted.

However, if building an island is not possible due to construction conditions, a fixed type of temporary overflow prevention cover may be installed and submerged to block the inside of the caisson from above and below.

However, when the overflow prevention lid is of a fixed type, it is difficult to adjust the balance between the reaction force due to the internal pressure generated within the overflow prevention lid and the subsidence load.

Therefore, there is a construction method that uses a reaction plate with a movable over-sag prevention lid to gradually cause the building frame to sink.

The reaction plate in this construction method consists of the reaction plate main body and a sealing material attached to its periphery, and the tensile material is fixed to the frame.
A center hole jack installed on the top of the reaction plate moves the reaction plate up and down along the inner surface of the building frame to balance its own weight and reaction force.

<Problems to be Solved by the Present Invention> The conventional submersion techniques described above have the following problems.

(a) The seal around the reaction plate's periphery is not reliable, and the pressure inside the reaction plate becomes considerably large, so compressed air leaks from the seal and the balance between its own weight and reaction force becomes inadequate, resulting in overload. Prone to sexual harassment.

<Exposure> When sinking the caisson into the seabed, there is a risk that seawater will gush out along with compressed air from the seal around the periphery, causing the jack installed on the top of the reaction plate to be submerged, making it impossible to sink the caisson. There is.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an open caisson sinking method and equipment that can reliably prevent the caisson from overheating. With the goal.

<Configuration of the Present Invention> An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, an open caisson frame 1 having a circular cross section will be described as an example.

<A> Reaction force plate (Figs. 1 to 3) The reaction force plate 2 is a plate disposed in the open caisson frame 1 in the horizontal direction.

The shape of the reaction force plate 2 is, for example, formed into a disk shape having an outer diameter slightly smaller than the inner diameter of the caisson frame 1, as shown in FIG.

An opening 21 is formed in the center of the reaction plate 2, and from the periphery of the opening 21 to the vicinity of the top of the caisson frame 1,
The pipe body 22 is raised to secure a working space and the like.

<Opening> PC steel wire for pulling (Figs. 1 to 3) P for pulling
The C steel wire 3 is arranged in the longitudinal direction within the caisson frame 1.

The lower end of this pulling PC steel wire 3 is passed through the peripheral edge of the reaction plate 2 and fixed by a fixing portion 31 on the lower surface of the reaction plate 2.

On the other hand, a bracket 32 is attached near the top end of the inner peripheral surface of the caisson frame 1, and a center hole jack 33 is installed on the upper surface of this bracket 32.

The upper part of the pulling PC steel wire 3 is held by this center hole jack 33.

The number of the pulling PC steel wires 3 and center hole jacks 33 to be attached is appropriately selected depending on the weight of the reaction force plate 2 to enable the reaction force plate 2 to be raised and lowered.

<C> PCf14 wire for pulling down (Figs. 1 to 3) The PC steel wire 4 for pulling down is covered with a sheath 41 and buried in the vertical direction inside the caisson frame 1, and the lower end is extended upward by a U-shaped sheath 42. It is folded back and exposed in the hollow part of the caisson frame 1, and the upper end of the exposed part is passed through the peripheral edge of the reaction plate 2 and fixed by the fixing part 43 on the upper surface of the reaction plate 2.

Note that a reinforcing material 44 such as H steel is provided inside the U-shaped sheath 42.
bury it.

On the other hand, a center hole jack 45 is installed at the top of the caisson frame 1, and the upper part of the PC steel n4 for pulling down is
It is gripped by this center hole jack 45.

The required number of lowering PCM glands 4 and center hole jacks 45 are installed so that they can sufficiently withstand the reaction force when the caisson frame 1 is submerged.

<2> Cutting device (Fig. 4) A space pocket 5 is secured in advance around the lowering PC [ff14] in the caisson body 1, and the thermite agent 51 and ignition electric bridge 52 are set therein. (.

In addition, an injection hole 53 for injecting a fixing agent is provided around the lower end of the portion of the pulling-down PC steel wire 4 to be cut.

<Action of the present invention> Next, the effects of the present invention will be described.

<A> Securing the reaction force during submersion Activate the center hole jack 33 and raise the
The reaction plate 2 in the caisson frame 1 is positioned on the soft ground 6 via the C steel wire 3.

Next, the center hole jack 45 is activated, the upper part of the PC steel wire 4 for pulling down is pulled upward, and the lower surface of the reaction plate 2 is pressed against the surface of the soft ground 6, so that the reaction force can be taken from the ground. can.

The reaction force taken from the ground can be transmitted to the caisson frame 1 via the reaction force plate 2) and the PC steel wire 4 for pulling down.

As the caisson frame 1 sinks, earth and sand pushed up from the openings 21 of the reaction plate 2 are discharged by the Talam shell packet 7 and the like, and are sunk to a predetermined depth in the foundation ground layer 8.

<Exit> Introduction of prestress After the caisson frame 1 is sunk to a predetermined depth, the thermite agent 51 is heated by the ignition electric bridge 52, and the lowering PC steel wire 4 is cut midway.

Next, a fixing agent such as grout is injected through the injection hole 53,
The cut lower end of the PCjIII wire 4 for pulling down is fixed in the caisson frame 1.

Then, the upper part of the PC steel wire 4 for pulling down is pulled upward by the center hole jack 45 to create tension, thereby introducing a predetermined prestress into the caisson frame 1.

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

<B> In the conventional construction method using a movable reaction force plate, the sealing around the periphery is not reliable, and the pressure inside the reaction force plate becomes considerably large, so compressed air leaks from the sealing part, resulting in its own weight and reaction force. The balance between the two is insufficient, and excessive subsidence is likely to occur.

In contrast, in the present invention, the reaction force for sinking the caisson can be taken directly from the ground by pressing the lower surface of the reaction plate against the ground.

Therefore, the weight of the caisson can be supported by a wide area of excavated ground.

Therefore, a stable reaction force can be obtained and excessive sinking can be reliably prevented.

<Exposure> In the conventional construction method using a movable reaction plate, when the vessel is submerged on the seabed, seawater is ejected along with compressed air from the seal around the periphery, causing the jack installed on the top of the reaction plate to be submerged. Problems may occur, making it impossible to sink the caisson.

In contrast, in the present invention, the center hole jack is attached to the top end of the caisson.

Therefore, the jack is not submerged in water, and the caisson sinking work can proceed smoothly.

<C> Since the reaction force is taken directly from the ground, there is no need to seal the periphery of the reaction plate.

Also, depending on the degree of softness of the excavated ground that takes the reaction force, 1
The reaction plate can have a simple cross-shaped structure.

Therefore, the structure of the entire device is simple and economical.

(2) If a large horizontal load acts on the caisson after it is sunk, prestress can be introduced into the caisson frame using the PC steel wire used during the sunken caisson.

Therefore, it is possible to construct a strong structure that can sufficiently withstand large horizontal loads.

Figure 3: Enlarged explanatory diagram of main parts Figure 4: Explanatory diagram of how to introduce nibrest stress

[Brief explanation of the drawing]

Part 1l: Explanatory diagram of one embodiment of the present invention Figure 2: Horizontal cross section of caisson

Claims (5)

[Claims] (1) A vertically movable reaction plate arranged horizontally inside the open caisson, a lifting PC steel wire whose lower end is fixed to the reaction plate and placed vertically inside the caisson, and a lifting PC steel wire arranged vertically inside the caisson. A center hole jack that grips the upper part of the PC steel wire and installs it near the top of the caisson, and a center hole jack that is buried vertically within the caisson frame, exposes the lower end inside the caisson, folds it upwards, and connects the upper end of the exposed part to the center hole jack. This open caisson is characterized by consisting of a pull-down PC steel wire whose part is fixed to the reaction plate, and a center hole jack that grips the upper part of the pull-down PC steel wire and is installed near the top of the caisson. Submersion equipment. (2) In the open caisson sinking device according to claim 1, the reaction plate has an opening in its center, and the tube body extends from the periphery of the opening to the vicinity of the top of the caisson. An open caisson sinking device constructed by setting up and configuring. (3) In the sinking method using the open caisson sinking device set forth in claims 1 and 2, the reaction plate in the caisson is positioned on the ground, and the lowering PC
An open caisson sinking method in which the upper part of the steel wire is pulled upward by a center hole jack and the lower surface of the reaction plate is pressed against the ground to absorb the reaction force in the ground while sinking the caisson. (4) In the open caisson sinking device according to claims 1 to 3, a melting agent for melting and cutting the lowering PC steel wire is placed around the middle of the lowering PC steel wire in the caisson frame. An open caisson burying device with an injection hole for injecting a fixing agent around the lower end of the planned cutting part of the PC steel wire for pulling down. (5) In the sinking method using the open caisson sinking device set forth in claim 4, after sinking the caisson to a predetermined depth, the lowering PC steel wire is cut in the middle by the melting agent, and then: Inject fixing agent through the injection hole to fix the cut lower end of the PC steel wire for pulling down inside the caisson frame, and
An open caisson installation method in which the upper part of the C steel wire is pulled upward by a center hole jack to create tension and introduce prestress into the caisson frame.