JPS63171921A - Deformed closed caisson work - Google Patents

Abstract

PURPOSE:To shorten the period of operation in ocean by a method in which a caisson is temporarily installed by leaving a buoyancy, a solidifying agent is injected to completely install it, and filling sand is packed into the caisson. CONSTITUTION:A closed caisson A is towed by turning its side as bottom and sea water is introduced into the caisson A from the compartment B of the bottom by adjusting the operation of valves through, which sea water is intro duced and air is discharged in such a way as to erect it for temporary installa tion by leaving its buoyancy. A solidifying agent d2 is injected into the bottom- upped space C, baggy covers C1 and C2 are closely covered on the undulatory surface of the rubble-mound, and the caisson A is completely installed by remov ing the buoyancy. Filling sand is sent through a pipe (a) into the caisson A. The caisson A can thus be exactly performed by greatly shortening the operat ing period in sea area since the partial leveling of rubble-mound is suffice and sand-filling operation can be quickly performed.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a caisson construction method used for, for example, port structures such as breakwaters and seawalls, and in particular, the invention relates to a caisson construction method used for port structures such as breakwaters and seawalls, and in particular, the construction method used in construction of large caissons that are planned under deep water. Concerning a closed irregular caisson construction method in which the cross section of the caisson body is made asymmetrical as necessary so that the center of gravity is at the optimum position for the load conditions, the entire caisson is sealed, and the bottom plate is raised. It is something.

``Conventional technology and its problems'' In recent years, many gravity-type port facilities have been planned in deep-water areas due to the highly effective use of ocean space. These construction costs are enormous, so it is necessary to reduce them. Therefore, if the top of the rubble mound, which is a large part of the construction cost, is lowered by a considerable amount, the caisson becomes huge and many problems arise.

The main problems are: insufficient support capacity of the rubble mound against the caisson end bearing pressure due to increased caisson weight and design wave height; problems during launching due to increased water intake; installation problems due to increased weight; There is a difficulty in leveling rubble mounds under deep water.

Currently, a raised-bottom caisson construction method has been developed that creates an interlock between the caisson and the rubble mound by raising the bottom of the caisson and filling the raised-bottom space with underwater concrete. This construction method increases the sliding resistance, which prevents an increase in the weight of the caisson, reduces end-bearing pressure, and eliminates the need to level the rubble at the raised bottom. However, in the case of giant caissons used for seawalls, etc., their effectiveness alone does not provide a fundamental solution, and problems also remain with the construction method.

This calls for the development of a new giant caisson construction method that is suitable for deep water.

The basic stability considerations for a caisson-type hybrid embankment, which is a gravity-type structure, are the sliding and overturning of the caisson embankment body, and the supporting capacity of the rubble mound against the bearing pressure at the caisson end. In general, the safety factor for the stability of a giant caisson is the smallest, which is the supporting force of the end bearing pressure of the caisson, followed by sliding, and there is more margin than others to prevent overturning. The problem of the bearing capacity of the caisson end bearing pressure can be solved by widening the caisson bottom plate, but
This would have little effect on preventing rubble mounds from becoming gigantic.
There is little point in using a huge caisson.

Since conventional large caisson is a floating body when towed,
Its cross section (cross section viewed from the side) is symmetrical, and its horizontal center of gravity is fixed at the center. Theoretically, the sliding resistance force is expressed as the product of the vertical force on the bottom of the caisson and the sliding resistance coefficient, and is unrelated to the position of the center of gravity of the caisson embankment, but other overturning and supporting forces are largely controlled. Ru.

That is, the closer the horizontal center of gravity of the embankment body is to the opposite side to the direction of the horizontal external force, the greater the overturning resistance moment becomes, and the more equal the reaction force distribution on the bottom of the caisson becomes.

``Means for Solving the Problems'' Therefore, in the present invention, the shape of the cross section of the caisson is downward sloped, and the upper part is shaped with respect to the bottom part so that the horizontal center of gravity position is the optimum position for the design load condition. This is a relative horizontal movement. Here, the optimal center of gravity position of the caisson embankment varies depending on the design conditions and is not constant. For example, the main horizontal external forces that act on a tsunami seawall are the wave force and seismic force caused by the tsunami. Generally, wave force is much larger, but in this case it is also necessary to consider seismic force in the direction opposite to the wave force, so the optimal center of gravity position will not be constant.

Furthermore, the present invention incorporates the advantage of the raised bottom caisson, which is increased sliding resistance, to rationally pursue stability of the caisson embankment. In other words, by locating the optimal center of gravity of the caisson embankment and increasing the sliding resistance force, the excess weight of the embankment can be significantly reduced.Furthermore, by equalizing the reaction force distribution on the bottom of the caisson, the end bearing pressure of the caisson can be significantly reduced. This is what we aim to do.

By the way, for a caisson that floats on its own blade, it must be stable so that it does not capsize or tilt. However, the caisson of the present invention is very unstable in its normal state due to its asymmetrical cross-section. In addition, the structural members of a caisson include diagonal members, which are difficult to manufacture because they are huge.

Therefore, in the present invention, the caisson is manufactured with one side wall as the bottom surface. This allows all members of the caisson to be replaced with vertical and horizontal members, making manufacturing easier. In the caisson of the present invention, the top plate is added as one piece from the beginning, and when the manufacturing is completed, it is in a sealed state.
The caisson is launched and towed with the sidewalls at the bottom. The shape of the cross section in this state is a symmetrical rectangular cross section with a constant height and length in the normal state. By the way, the maximum area of this is the bottom plate, and the minimum area is the top plate. Therefore, when the caisson is floating, its cross-sectional area is symmetrical, and since it is in a sealed state, it is in an extremely stable state.

The problem of launching a caisson due to an increase in water intake due to its large size was solved by making the cross section of the caisson wider downward and launching it with one side wall of the caisson as the bottom. Ru. In other words, the amount of water intake is determined by the weight per unit weight of the floating body, but when launched with the side wall of the caisson as the bottom, it is determined by the height at that time, that is, the length in normal conditions. In the dimensional specifications of a caisson, among the width, length, and height, length is a small element that is restricted by design conditions. Therefore, the length of the caisson can be determined based on the amount of water intake. However, it must also be stable in the direction of the caisson embankment. The largest horizontal external force in the direction of the levee body is the seismic force. It is sufficient if at least each individual caisson is stable against this seismic force. Since the caisson of the present invention extends downward, the center of gravity is low and the shape is most stable against earthquake forces. In addition, the caisson of the present invention has its top plate integrated from the beginning, a new intermediate floor slab, and partitions into separate compartments by these and vertical and horizontal bulkheads. This is structurally very strong, allows each member constituting the caisson to be made thinner, and further reduces the weight of the caisson.

As mentioned above, the caisson construction method of the present invention is for launching and towing a caisson in a sealed state with one side wall serving as the bottom surface. Therefore, the caisson must be installed in its normal state, and filling work must be performed with the top plate in place. As a countermeasure to these problems, filling piping with airtight lids and air-release valves will be installed in the upper and lower directions of each compartment. Two of these pipes are always placed in each branch, and each branch has openings at the top and bottom. Furthermore, seawater introduction valves are installed at appropriate positions in the bottom compartments, and water flow valves are installed between the compartments in the lateral direction (towards the embankment body) of the bottom, if necessary. That is, the space inside the caisson partitioned by the vertical partition wall can be independently sealed as necessary.

Further, the caisson of the present invention has a raised bottom space formed in its bottom surface, and has a bag-shaped cover made of a flexible material attached to the raised bottom space and a solidifying material injection pipe communicated with the inside of the bag-shaped cover. It is something to be equipped with.

The installation work of the present invention begins by first setting the side wall to the normal state with the bottom surface. The process involves manipulating and adjusting the seawater inlet valve, water flow valve, and air release valve of the caisson to introduce seawater from a compartment at the bottom of the caisson, occupying a predetermined internal space (chamber) with seawater, and then opening the caisson. Turn it over and stand it upright,
It controls the correct posture. The speed at which the caisson rises is proportional to the speed at which seawater is introduced, and this adjustment is made by adjusting the air bleed valve. Next, temporary installation work will be carried out. The process leaves a designated space,
By occupying the other space with seawater, the caisson is installed with its buoyancy remaining. This is because when installing a huge raised bottom caisson, the raised bottom part is not attached to the floor, so the part that is attached to the floor is a part of the bottom surface. Therefore, even if the caisson is not filled, the lack of supporting capacity is inevitable, just as the lack of allowable supporting capacity of the rubble mound against the end bearing pressure of a huge caisson becomes a problem. This causes uneven subsidence. For this reason, the installation of the giant raised-bottom caisson was an important step, and the temporary installation was an important step, leaving buoyancy in the caisson so that the supporting capacity of the rubble mound would not be insufficient. Next, the actual installation will be carried out. The process involves injecting the consolidating material into the raised bottom space, fitting the bag-like cover closely to the unevenness of the surface of the rubble mound, making the caisson fit into the rubble mound, and adding the consolidating material. After waiting for the caisson to harden, the buoyancy was removed by filling the entire interior space of the caisson with water, and the main installation was completed.

Next, perform filling work. In this system, sand and seawater are pumped by a pump ship or the like through filling pipes with sealed lids installed in advance in the caissons. Two of these pipes are always arranged in each compartment, and when one of them is used as a pressure feed pipe for filling sand, the other serves as a drain pipe. Then, each compartment in the lower layer is filled in order.

"Example" Hereinafter, an example of a tsunami seawall according to the present invention will be described with reference to the drawings. 1 to 4 are structural explanatory views of a caisson suitable for use in carrying out the construction method according to the present invention.

1 is a cross-sectional view, FIG. 2 is a longitudinal sectional view of the front wall, FIG. 3 is a plan view, and FIG. 4 is a bottom view.

In the figure, the symbol (A) is a sealed deformed caisson made of reinforced concrete, and the symbol (IA) is the caisson body. Further, reference numeral (1) is the front wall, (2) is the rear wall, (3) is the side wall, (4) is the bottom plate, and (5) is the top plate. A typical caisson is open at the top and has a rectangular cross section. In contrast, the cross section of the caisson of the present invention is trapezoidal, as seen in FIG. The front wall, which receives tsunami wave pressure, has a small inclination, while the rear wall has a large inclination, and its horizontal center of gravity is largely biased toward the front wall.

In this case, the front wall and the rear wall do not necessarily have to be straight walls, and may be, for example, front walls for returning waves, or may have a stepped shape.

In the figure, code (6) is the intermediate floor slab, (7) is the longitudinal bulkhead, (
8) is the transverse bulkhead, and (B) is the compartment within the caisson body partitioned by these. Code (9) is the front edge wall of the raised garden;
(10) is a raised bottom edge wall, (11) is a raised bottom vertical bulkhead made of steel plate, (12) is a raised bottom bulkhead, and (C) is a bottom slab and raised yard front edge wall or rear edge wall and raised bottom vertical and horizontal bulkheads. It is a raised bottom space surrounded by. Reference numeral (a) indicates a filling pipe, and a seal M (both not shown) in which an air vent valve is incorporated is attached to the top end of the pipe. Also, this filling piping (
Two a) are arranged in the vertical direction of each compartment, and each compartment has an opening at the top and bottom, respectively. The symbol (bl) is the injection pipe for the solidifying material injected into the small compartment (D), and the symbol (b,) is the injection pipe into the raised bottom space (C), and these injection pipes are buried in the wall in advance. ing. Although not shown in the drawings, seawater inlet valves are installed at the bottom of each compartment at the bottom of the side wall when the caisson is manufactured. In this embodiment, there are three locations. Water valves will be installed between the compartments in the horizontal direction (towards the embankment body) at the bottom. If seawater inlet valves are installed on the bottom slab of each compartment at the bottom, water flow valves are not required.

FIG. 5 is a three-dimensional view of the caisson of the present invention with one side wall as the bottom surface, and the caisson is manufactured in this state. In this state, all members can be replaced with vertical or horizontal members, making it easy to manufacture.

As seen in Figures 1 and 5, in front of the raised bottom space,
Inside the rear edge wall, a plurality of small compartments (D) with openings at the bottom are formed by vertical and horizontal partition walls with raised bottoms.

This is a further development of the functions of the conventional raised-bottom caissons.

The features of conventional raised-bottom caissons are that they increase sliding resistance by creating an interlock between the caisson and the rubble, and that there is no need to level the rubble mound at the raised bottom. However, the main leveling of the rubble mound portion corresponding to the peripheral wall portion of the raised bottom portion still remains. Currently, it is extremely difficult to manually level rubble mounds under deep water, so the development of mechanized leveling is underway, but the accuracy of leveling is an obstacle. Therefore, in order to be able to install a caisson even if the surface leveling accuracy of the rubble mound is low, we added a function that allows the height and levelness of the caisson to be freely adjusted to the function of the raised bottom caisson. The surface leveling is completely mechanized leveling.

Figure 6 is an enlarged view of the bottom of the caisson. In the figure, the symbol (b,) is the injection pipe for the consolidation material in the small compartment, (b,) is the injection pipe for the consolidation material in the raised bottom space (C), and (cl) is the injection pipe for the consolidation material in the small compartment (D
) is a bag-like cover, (C3) is a cover for the raised bottom space, (
d,) is the underwater concrete of the small cell, and (E) is the rubble mound. The covers for the raised bottom and small compartments are made of flexible material to prevent concrete from spilling out underwater. A method for adjusting the height and horizontality of the caisson is to push up the caisson by injecting a consolidating material into at least one of each of the small compartments and inflating and protruding the bag-like cover from the small compartment. It is. In this step, the height and levelness of the caisson are adjusted while controlling the injection pressure and amount of consolidation material. Figure 6 shows underwater concrete being poured into the small compartment (D) and pushing up part of the rear edge wall of the caisson. Further, the cover of the raised bottom space is folded into the raised bottom space.

7 to 9 are explanatory diagrams of the process of installing a caisson when carrying out the construction method according to the present invention.

The installation of the present invention begins by first bringing the side wall to the normal position with the bottom surface. The seawater introduction routes in this embodiment are, first, three routes: a compartment at the bottom of the side wall, which becomes the bottom surface when the caisson is towed.

This leads through a water valve to a compartment at the bottom of the side wall on the opposite top surface. Further, each of the compartments at the bottom communicates with the compartments at the top through filling piping. That is, there are four routes each for the front wall side, the middle route, and the rear wall side, so there are 12 routes in the end. The method of inverting the caisson and standing it up in its normal state is to occupy a predetermined internal space of the caisson with seawater; the process involves first opening three seawater inlet valves at the bottom; Open the water valve and
Open only the air bleed valves (3 locations) in the compartment on the side wall, which is the towing special top surface, and introduce seawater. Adjust the introduction speed with the air bleed valve.

When all the compartments at the bottom are filled with water, close the air bleed valve and stop introducing seawater. At this point, the caisson is already in an upright position. That is, when seawater occupies a certain space inside the caisson, the caisson as a floating body is configured in advance so that it becomes a partition of the occupied space by inverting and standing up. A seawater sensor is used to check whether the bottom compartment is full of water. Next, since the buoyancy on the front wall of the caisson is large, we installed air bleed valves on the front wall (4 locations).
Open it, introduce seawater into the compartment on the front wall side, properly control the posture of the caisson, and close the air bleed valve. FIG. 7 is a cross-sectional view of the caisson showing this state. In the figure, the symbol (B +) is an empty compartment, and the symbol (B,) is a compartment into which seawater has been introduced.

Next, temporary installation work will be carried out. In this process, seawater is allowed to occupy a predetermined space and subside to about 50 cm above the caisson landing position on the rubble mound. FIG. 8 is a cross-sectional view showing this state.

The seawater introduction process involves opening the air vent valves (four locations each) on the front and rear walls, introducing seawater into each compartment, and allowing the caisson to sink while accurately controlling its posture. Mark the caisson height scale on the caisson wall surface in advance, check the sinking depth, and close the air release valve. Then check the landing position,
Align the caisson, open the air bleed valves (4 locations) in the middle compartment, introduce seawater, and gently place the vessel on the floor.

In this case, the caisson is temporarily installed while leaving a predetermined space and allowing other spaces to be occupied by seawater, leaving buoyancy in the caisson.

Next, the main installation work will be carried out. The process first confirms the inclination of the top of the caisson, determines the relative heights of the small compartments at the four corners of the caisson among the small compartments, and sets the heights of these to level the caisson. Then, underwater concrete is injected into the small compartment that is insufficient in height through the cement injection pipe, and the bag-like cover is expanded and protruded from the small compartment to push up the caisson and keep it horizontal.
Subsequently, underwater concrete will be poured into the remaining small compartments.

In this case, check the injection pressure to avoid pushing up the caisson by applying too much injection pressure. Next, underwater concrete is poured into the raised bottom space in the same way. FIG. 9 is a cross-sectional view showing this state. In the figure, the symbol (d
1) is the underwater concrete in the small compartment, and (d,) is the underwater concrete in the raised bottom space.

Next, perform filling work. During the filling process, sand and seawater are pumped through the filling piping using a pump ship, etc. Two filling pipes are arranged in each compartment, one of which serves as a drain pipe. In this case, sand with a high silt content will pollute the ocean, so inexpensive sea sand with a low silt content is suitable as the filling material. FIG. 1O is a cross-sectional view of the casing in a state in which filling is completed. In the figure, the symbol (B3
) is an enclosed branch room.

``Effects of the Invention'' In the closed deformed caisson construction method according to the present invention, the cross-sectional shape of the caisson is slanted downward to lower the vertical center of gravity, and the horizontal center of gravity is located at the optimal position for the design load conditions. This is a configuration in which the top is graphically moved horizontally relative to the bottom. As a result, the stability of overturning, which is a stable element of the caisson, is increased, and the end bearing pressure of the caisson is also reduced by equalizing the distribution of reaction force on the bottom of the caisson.

Furthermore, the present invention incorporates the function of a raised bottom caisson to increase the sliding resistance, so the stability of both the overturning and sliding of the stabilizing elements of the caisson is increased, and as a result, the excess weight of the embankment can be greatly reduced. As a result, the end bearing pressure of the caisson can be further reduced significantly.

On the other hand, the caisson used in the construction method of the present invention is unstable as a floating body because its cross-sectional area is asymmetric in its normal state. Also, its water intake is as large as that of a conventional caisson. Furthermore, the caisson's structural members include diagonal members, and because it is a huge caisson, it is difficult to manufacture.

Therefore, in the caisson of the present invention, the top plate is added from the beginning, a new intermediate floor plate is added, the internal space of the caisson body is partitioned into separate rooms, and the bottom of the caisson body is raised to provide the functions of a raised-bottom caisson. It uses a closed caisson. The construction, launching, and towing of this vessel is carried out with one side wall as the bottom. This allows all main members to be replaced with vertical and horizontal members, making manufacturing easier.

In addition, in terms of structural mechanics, the caisson is divided into separate compartments, making it extremely strong and allowing each member to be made even thinner.
゛The weight reduction of the caisson is promoted. In addition, the cross-sectional area in this state is symmetrical, and since it is in a sealed state, the stability as a floating body is extremely high. Furthermore, the amount of water intake is proportional to the length of the caisson in this state, but since the caisson of the present invention has a low center of gravity, the length of the caisson can be easily adjusted.

The installation of the caisson of the present invention begins with the construction being in its normal state, and the method involves filling a predetermined internal space with seawater and inverting the caisson as a floating body to stand it upright. That is, the intermediate floor slab that constitutes the compartment at the bottom of the caisson is constructed not only to reinforce the outer wall but also to serve as a division of the occupied space for the caisson to stand up. The rate at which the caisson rises or sinks is determined by the rate at which seawater is introduced, and this is precisely regulated by the caisson's air release valve.

It is also easy to temporarily install the caisson while maintaining the necessary buoyancy by suspending the introduction of seawater to ensure a predetermined level of water intake, and by leaving a predetermined internal space. In this way, the function of a closed caisson that allows the installation of a giant caisson to be controlled freely made it possible to incorporate the functions of a raised-bottom caisson into the giant caisson. Furthermore, by further developing the function of the raised-bottom caisson and adding the ability to adjust the height and levelness of the caisson, leveling of rubble mounds under deep water, which is extremely difficult to do manually, can now be done completely mechanized. The main leveling only needs to be done on the part of the caisson that corresponds to the small compartment. In addition, in the conventional caisson construction method, sandstone, etc., is poured into the caisson using a boat to fill the lining, and then concrete is poured for the lining cap (top plate).

On the other hand, in the caisson filling of the present invention, two filling pipes are installed in each compartment, and when one is used as a pressure feeding pipe for filling sand, the other functions as a drain pipe, so that the pump ship This allows for rapid construction of filling.

This significantly shortens the construction period for the middle filling.

Offshore construction in deep water areas is subject to severe weather and sea conditions, and the days suitable for construction work are limited. For this reason, it is essential to carry out rapid construction using construction methods that are highly resistant to waves. On the other hand, the caisson of the present invention is the most stable floating body, the caisson can be installed reliably, leveling of the rubble mound is completely mechanized and only needs to be done partially, and the filling can be completed quickly. It is a quick construction. In this way, on-site marine operations have been significantly shortened. As mentioned above, the closed deformed caisson construction method according to the present invention is a complete construction method that solves all the main problems of the current caisson-type giant hybrid embankment, including the stability problem at the time of completion.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention; FIG. 1 is a cross-sectional view of the caisson, FIG. 2 is a vertical cross-sectional view of the caisson, FIG. 3 is a plan view of the caisson, and FIG. 4 is a bottom view of the caisson. FIG. 5 is a perspective view of the caisson, FIG. 6 is an enlarged partial sectional view of the installed caisson, and FIGS. 7 to 10 are process diagrams each showing the process sequence of the present invention in cross section. A: Caisson, lA: Caisson body, B: Branch, C: Raised bottom space, D: Small compartment, a... Piping for filling,
b,, b,...Injection pipe for consolidation material, CI+C1
...Bag-like cover, l...Front wall, 2...
... Rear wall, 3 ... Side wall, 4 ... Bottom slab, 5 ... Suzaka, 6 ... Middle floor slab, 7
...Vertical bulkhead, 8...Transverse bulkhead. Applicant Kimitaka Kondo Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] The cross-sectional shape of the caisson body expands downward, and the top part is graphically moved horizontally relative to the bottom part so that the horizontal center of gravity is at the optimum position for the design load conditions. The space is divided into separate rooms with intermediate floor slabs and vertical and horizontal bulkheads, and filling pipes with airtight lids and built-in air release valves are installed in the vertical direction of each room, and a seawater inlet valve is installed in the bottom room. At the same time, a bag-like cover made of a flexible material is attached to a raised bottom space formed on the bottom and a small compartment with an opening at the bottom located around the raised bottom space, and each of these bag-like covers communicates with each other. The caisson is launched and towed with the side wall facing the bottom, and during installation, a seawater inlet valve and an air bleed valve are used. By operating and adjusting the caisson, seawater is introduced from the compartment at the bottom of the caisson, the seawater occupies a predetermined internal space, and the caisson is inverted and erected in its normal state. A process of temporarily installing the caisson with buoyancy remaining by leaving the remaining space occupied by seawater, and injecting a consolidating material into the raised bottom space to fit a bag-shaped cover to match the irregularities of the rubble mound. A sealed deformed caisson construction method that includes the main installation process of removing the buoyancy of the caisson after it is brought into close contact with the caisson, and the process of pumping filling sand through filling piping.