JP2021188323A - Method for reinforcing existing caisson foundation - Google Patents

Abstract

To provide a method for reinforcing an existing caisson foundation that can reinforce a caisson foundation without securing a dry working space and by reducing water pressure acting on and using a simple temporary structure.SOLUTION: A method for reinforcing an existing caisson foundation F1 by a steel plate comprises a step of excavating in a cofferdam 3 that installs a cofferdam (cofferdam body 3) and excavates sediment at the upper part of the caisson foundation F1 in the cofferdam 3, and a step of press-fitting a reinforcing steel plate that press-fits a reinforcing steel plate for reinforcing the caisson foundation F1, to the foundation around the existing caisson foundation F1. In the step of excavating in a cofferdam, sediment in the cofferdam 3 is excavated and removed without discharging water in the cofferdam 3 to the water bottom and while leaving water as it is.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for reinforcing an existing caisson foundation in which a caisson foundation having a portion having a cross-sectional shape or a different dimension from that of an existing bridge pier is reinforced with a steel plate.

As the tightness of large-scale earthquakes has been pointed out, it is required to retrofit the foundations of existing bridges in order to improve the seismic performance of existing bridges. However, the foundations of existing bridges often exist in soil and underwater that are buried in riverbeds and have overburdens. For this reason, when implementing seismic retrofitting of existing foundations, it is necessary to first install temporary structures such as earth retaining and temporary deadlines, and then expose the existing foundations to secure a dry work space around them. There is. After that, various seismic retrofitting works such as concrete winding, steel plate winding, and additional piles are generally performed.

Steel sheet piles, liner plates, steel panels, etc. are usually used as temporary structures, and such temporary structures take into consideration the soil pressure resistance and water pressure resistance required to secure a dry space inside. It is designed to be.

As a method for seismic reinforcement of the foundation of an existing bridge using such a temporary structure, for example, in Patent Document 1, a plurality of steel plate members 1a are applied to the outer periphery of the bridge pier 3 proposed by the applicant of the present application. A steel plate block 1 is formed by joining the joint ends, and a pressing plate 5 and a press-fitting device 2 provided with a hydraulic jack 11 whose upper end can be fixed to a tension transmission rod 12 are mounted on the steel plate block 1. After the steel plate block 1 is press-fitted into the ground by a predetermined amount by installing and extending the hydraulic jack 11, the press-fitting device 2 is disassembled and removed, and the next steel plate block 1 is added on the press-fitted steel plate block 1 and then. The press-fitting device 2 is assembled and installed on the steel plate block 1, and the steel plate block 1 is press-fitted into the ground by extending the hydraulic jack 11, and the steel plate block 1 is put into the ground by repeating this construction process. A method for reinforcing a columnar structure to be press-fitted is disclosed (see claim 1, paragraphs [0020] to [0033] of the specification, FIGS. 5 to 9 of the drawing, etc.).

The method for reinforcing a columnar structure described in Patent Document 1 has an advantage that the underground buried portion can be reinforced by press fitting without securing a working space for winding a steel plate with respect to the columnar structure. However, although the method for reinforcing a columnar structure described in Patent Document 1 can be applied to a columnar structure having a straight cross section and not changing from the pier to the foundation, the cross section has a portion having a large cross section unlike the pier. When applying to an existing caisson foundation, it is necessary to install earth retaining and temporary deadlines, expose the upper end of the existing caisson foundation to be reinforced, check it, and correct the construction base surface to carry out reinforcement work. was there.

Therefore, the temporary structure such as the temporary deadline used when the method for reinforcing the columnar structure described in Patent Document 1 is applied to the caisson foundation shall be designed in consideration of the water level, the water pressure of the overburden and the earth pressure. Was needed. In particular, when the water depth and the soil cover are deep, there is a problem that the temporary structure becomes large-scale, the construction period is long, the temporary construction cost is high, and the economic efficiency is deteriorated.

Further, the method for reinforcing a columnar structure described in Patent Document 1 is a reinforcing method in which a reinforcing steel plate is joined and press-fitted on the outer periphery of an existing foundation to be reinforced, the gap between the existing foundation and the reinforcing steel plate is cleaned, and a filler is filled. Therefore, when applied to a caisson foundation whose cross-sectional shape expands at the bottom, there are the following problems. That is, in the pier portion above the caisson foundation with a small cross-sectional shape, the gap between the reinforced steel plate and the pier becomes large, which makes it difficult to control the eccentricity of the reinforced steel plate, makes it difficult to clean the gap, and the filler. There is a problem that a large amount is required and it cannot be filled by a normal filling method.

Further, as a reinforcement method for the caisson foundation as a reinforcement target, in the seismic reinforcement structure of the existing caisson foundation proposed by the applicants of the present application in Patent Document 2, a certain distance from the caisson is provided on the ground around the existing caisson foundation 11. An underground wall 12a is provided so as to surround the caisson, and an improved body is created by ground improvement for the entire ground surrounded by the caisson and the ground wall. A seismic reinforcing structure of an existing caisson foundation in which a caisson foundation is fixed and integrated is disclosed (claim 3, claim 3, paragraphs [0022] to [0026] of the specification, drawings of the scope of the patent claim of Patent Document 2). 1 to 3 etc.).

However, in the seismic reinforcement structure of the caisson foundation of Patent Document 2, a steel sheet pile is installed and the ground is improved between the caisson foundation and the caisson foundation by using a high-pressure injection stirrer. In terms of installation, it is the same as the conventional reinforcement method described above, and the above-mentioned problems such as the problem that the temporary structure becomes large scale, the construction period is long, the temporary construction cost increases, and the economic efficiency deteriorates. It was not something that could be resolved.

Japanese Unexamined Patent Publication No. 2002-4301 Japanese Unexamined Patent Publication No. 2005-299188

Therefore, the present invention has been devised in view of the above-mentioned problems, and an object thereof is to use a simple temporary structure by reducing the water pressure acting without securing a dry working space. The purpose is to provide a method for reinforcing an existing caisson foundation that can reinforce the caisson foundation.

The method for reinforcing the existing caisson foundation according to claim 1 is a method for reinforcing the existing caisson foundation by reinforcing the existing caisson foundation with a steel plate, and a temporary deadline is set to excavate the earth and sand above the caisson foundation in the temporary deadline. The temporary deadline excavation process and the reinforcing steel plate press-fitting process of press-fitting the reinforcing steel plate to reinforce the caisson foundation into the ground around the existing caisson foundation are provided. It is characterized by excavating and draining the water in the temporary deadline without draining it to the bottom of the water.

The method for reinforcing the existing caisson foundation according to claim 2 is the guide member for installing a guide member for guiding the press-fitting of the reinforcing steel plate before the step for press-fitting the reinforcing steel plate in the method for reinforcing the existing caisson foundation according to claim 1. It has an installation step, and the reinforcing steel sheet press-fitting step is characterized in that the reinforcing steel sheet is press-fitted while guiding the press-fitting direction of the reinforcing steel sheet with the guide member.

The method for reinforcing the existing caisson foundation according to claim 3 is the method for reinforcing the existing caisson foundation according to claim 2. In the reinforcing steel plate press-fitting process, at least the weight of the temporary structure such as the temporary deadline is used as the press-fitting reaction force. Then, the reinforcing steel plate is press-fitted.

The method for reinforcing the existing caisson foundation according to claim 4 is the method for reinforcing the existing caisson foundation according to claim 2 or 3. It is characterized by press-fitting while adding a Yatco steel plate, which is a temporary structure of.

The fifth aspect of the present invention is the method for reinforcing an existing caisson foundation according to any one of claims 1 to 4, wherein the temporary deadline, which is a temporary structure, is assembled and press-fitted with a press-fitting device to install the temporary deadline. It is characterized by.

According to the inventions according to claims 1 to 5, by not draining water to the bottom of the water in the excavation step in the temporary deadline, the water pressure acting on the temporary deadline from the outside can be reduced to make a cheap and simple temporary deadline. .. Therefore, the temporary cost can be reduced and the total cost of the caisson foundation reinforcement work can be reduced.

In particular, according to the second aspect of the present invention, the problem that the gap between the reinforced steel plate and the pier becomes large and it becomes difficult to control the eccentricity of the reinforced steel plate is solved, and the gap between the reinforced steel plate and the pier is narrowed for reinforcement at the time of press fitting. The steel plate can be properly guided to prevent the eccentricity of the reinforcing steel plate.

In particular, according to the invention of claim 3, when the reaction force at the time of press-fitting is insufficient only by obtaining from the existing pier, it is omitted to secure other reaction force means such as driving an earth anchor or the like into the water bottom. , Or the work period for securing other reaction force means can be shortened. Therefore, as a result, the construction period of the entire construction can be shortened and the construction cost can be reduced.

In particular, according to the invention of claim 4, it is possible to easily reinforce even when the position where the steel plate is to be reinforced is deep.

In particular, according to the invention of claim 5, the time for setting the temporary deadline can be shortened and the construction cost can be reduced.

FIG. 1 is a diagram showing a state before construction of a caisson foundation to be reinforced by the method for reinforcing an existing caisson foundation according to the present embodiment. FIG. 2 is a process explanatory diagram showing a temporary deadline assembly / press-fitting process of the method for reinforcing the existing caisson foundation as described above. FIG. 3 is a process explanatory view showing the excavation process in the temporary deadline of the method for reinforcing the existing caisson foundation as described above. FIG. 4 is a process explanatory view showing a guide member installation process of the method for reinforcing the existing caisson foundation as described above. FIG. 5 is a process explanatory view showing a reinforcing steel plate assembly process of the same method for reinforcing the existing caisson foundation. FIG. 6 is a process explanatory view showing a reinforcing steel plate press-fitting process of the same method for reinforcing the existing caisson foundation. FIG. 7 is a diagram showing a completed state after construction of the same method for reinforcing the existing caisson foundation.

Hereinafter, an embodiment of the method for reinforcing an existing caisson foundation according to the present invention will be described in detail with reference to the drawings.

A method of reinforcing an existing caisson foundation according to an embodiment of the present invention will be described with reference to FIGS. 1 to 7. In the present embodiment, the foundation of the pier P1 of the existing bridge over the river is a caisson foundation F1 having a portion having a thicker horizontal cross-sectional dimension than the pier P1 and a steel plate around the caisson foundation. The case where the seismic reinforcement is performed by installing the above will be described as an example.

(Before construction)
First, with reference to FIG. 1, the state before the construction of the structure to be the target of the seismic retrofitting work will be described. FIG. 1 is a diagram showing a state before construction of a caisson foundation to be reinforced by the method for reinforcing an existing caisson foundation according to the present embodiment. As shown in FIG. 1, reference numeral B1 is an existing bridge B1 to be seismically strengthened, and reference numeral P1 is an existing bridge pier P1. Further, the reference numeral F1 is the existing caisson foundation F1 of the existing pier P1. This existing caisson foundation F1 is a caisson foundation whose horizontal cross-sectional dimension is larger and thicker than that of the pier P1, and is constructed by laying a caisson (box body) made of reinforced concrete by an open caisson method or the like.

(1. Temporary deadline assembly / press-fitting process)
As shown in FIG. 2, in the method of reinforcing the existing caisson foundation according to the present embodiment, a temporary deadline assembly / press-fitting step of assembling a temporary deadline which is a temporary structure and press-fitting with a press-fitting device is performed. FIG. 2 is a process explanatory view showing a temporary deadline assembly / press-fitting process of a method for reinforcing an existing caisson foundation according to the present embodiment.

First, on the water surface of a river, a plurality of temporary cut-off members 2 made of arcuate steel materials in a plan view are joined and assembled with bolts or the like to construct a cylindrical temporary cut-off body 3. Then, the temporary cutoff body 3 is settled under the surface of the river by its own weight, the temporary cutoff material 2 is assembled on the water or in the water above the temporary cutoff body 3, and the temporary cutoff body 3 is added. By repeating the expansion and subsidence of the temporary cutoff body 3 in this way, the lower end of the temporary cutoff body 3 is implanted on the river bottom (water bottom) to construct a cylindrical temporary cutoff body 3 that reaches the water bottom from above the water surface. As shown in FIG. 2, the lowermost stage of the temporary cutoff body 3 is provided with a cutting edge having a triangular cross-section and a sharp lower end for reducing resistance at the time of ground press fitting.

After that, a press-fitting device 1 composed of a plurality of hydraulic jacks is installed on the existing pier P1 above the water surface by fixing it with an anchor or the like and obtaining a reaction force from the existing pier P1. Then, the temporary cutoff body 3 is press-fitted into the ground of the riverbed (water bottom) by the press-fitting device 1 via the pressure steel material 4 bridged over the upper end of the cylindrical temporary cut-off body 3. As shown in FIG. 2, the depth at which the temporary cutoff body 3 is press-fitted is a depth slightly deeper than the upper surface of the existing caisson foundation F1.

The timing of installing the press-fitting device 1 may be during the construction of the temporary deadline 3 or in the preliminary preparation stage before the construction. In short, the press-fitting device 1 may be constructed at any timing as long as it is constructed before the temporary cutoff body 3 is press-fitted into the ground.

Further, although a cylindrical shape is exemplified as the temporary cutoff body, the temporary cutoff body is not limited to the cylindrical shape, and the horizontal cross section has an oval shape, an elliptical shape, a rectangular shape, etc., and a predetermined space is secured around the existing caisson foundation F1. Any shape can be used.

(2. Drilling process in the temporary deadline)
Next, as shown in FIG. 3, in the method of reinforcing the existing caisson foundation according to the present embodiment, the earth and sand above the existing caisson foundation F1 and inside the temporary deadline 3 assembled and press-fitted in the previous step are temporarily removed. An excavation step in the temporary deadline is performed to excavate and drain the soil while leaving the water inside the deadline 3 without draining it to the bottom of the water. FIG. 3 is a process explanatory view showing an excavation process in a temporary deadline of a method for reinforcing an existing caisson foundation according to the present embodiment.

In this step, the diver dives into the water inside the temporary deadline 3, and the upper surface of the caisson foundation F1 exposes the overburden ground above the existing caisson foundation F1 below the water surface and the earth and sand deposited on it. Excavate until After that, the excavated earth and sand are discharged to the outside of the temporary deadline 3 by using a suction pump, a dredging bucket, a backhoe, and the like. In this way, the top end (upper surface) of the existing caisson foundation F1 to be reinforced is exposed and confirmed, and the construction base surface is corrected.

In the conventional caisson foundation reinforcement method, as described in the background technology, water inside the temporary deadline 3 is pumped up by a pump or the like to create a dry work space, and excavation / soil removal is performed. Therefore, it is considered that the work efficiency of this process itself is lower than that in the past in that the diver dives.

However, the temporary deadline 3 constructed in the pre-temporary deadline assembly / press-fitting process does not need to at least counter the water pressure acting from the outside by not draining water in this step. However, in order to secure a work space on the water in the post-process, a part of the water in the temporary deadline may be drained. Nevertheless, it is clear that the water pressure acting on the temporary deadline 3 from the outside can be reduced.

Further, in the conventional temporary cut-off method, since the reinforcement work is performed in a dry work space, it is necessary to press-fit the steel sheet pile and the temporary cut-off body to a position deeper than the lowermost portion of the caisson foundation F1 to be reinforced. On the other hand, the depth of press-fitting in this step is such that the upper surface of the caisson foundation F1 is exposed, and the temporary cut-off body 3 has a thin material thickness that can withstand only the earth pressure at that depth. A simple and inexpensive temporary deadline 3 made of a steel plate, a steel material, or the like can be obtained. Therefore, it is possible to reduce the cost of the temporary structure to be removed when the construction is completed and reduce the cost of the entire construction.

(3. Guide member installation process)
Next, as shown in FIG. 4, in the method of reinforcing the existing caisson foundation according to the present embodiment, a guide member installation step of installing a guide member for guiding the press-fitting of the reinforcing steel plate in the subsequent process is performed. FIG. 4 is a process explanatory view showing a guide member installation process of the method for reinforcing the existing caisson foundation according to the present embodiment.

In this step, a cylindrical guide member 5 having a horizontal cross section having an outer circumference of substantially the same diameter (approximately the same size) as the cross section of the existing caisson foundation F1 is assembled by bolt joining or the like, settled by its own weight, and the guide member 5 is placed on the upper stage thereof. And repeat these steps to install the guide member 5 above the existing caisson foundation F1. Of course, the guide member 5 is not limited to a cylindrical shape, and it goes without saying that the guide member 5 may have a shape corresponding to the cross-sectional shape of the caisson foundation F1.

This cylindrical guide member 5 has a large gap between the reinforcing steel plate 6 to be press-fitted and the existing pier P1, and the eccentricity control of the reinforcing steel plate 6 becomes difficult. It has a function of narrowing the gap and guiding the reinforcing steel plate 6 at the time of press fitting.

(4. Reinforcing steel sheet assembly process)
Next, as shown in FIG. 5, in the method for reinforcing the existing caisson foundation according to the present embodiment, a reinforcing steel plate assembly step for assembling the reinforcing steel plate 6 to be installed and reinforced on the outer periphery of the existing caisson foundation F1 is performed. FIG. 5 is a process explanatory view showing a reinforcing steel plate assembly process of the method for reinforcing the existing caisson foundation according to the present embodiment.

In this step, the bracket scaffolding 8 is attached to the uppermost stage of the temporary cutoff body 3, and a working scaffolding for assembling the reinforcing steel plate 6 is constructed on the water surface. This is because the reinforced steel plate 6 is a steel plate for main installation that is not removed to reinforce the existing caisson foundation F1, and therefore needs to be joined by complete penetration welding or the like, which is difficult to join in water.

In this step, steel plates having an arc-shaped or semi-circular cross section are joined and assembled, and the reinforcing steel plate 6 is sunk by its own weight, and an arc-shaped or semi-circular steel plate is assembled and expanded on the upper stage. By repeating this assembly and subsidence, the inner diameter (cross-sectional area) of the existing caisson foundation F1 is slightly larger than the horizontal cross section, and the main installation of seismic reinforcement with a predetermined height within the range necessary for structural calculation of the existing caisson foundation F1 is reinforced. Assemble the steel plate 6.

(5. Reinforcing steel plate press-fitting process)
Next, as shown in FIG. 6, in the method of reinforcing the existing caisson foundation according to the present embodiment, the press-fitting device 1 is used, and the guide member installed in the front guide member installation step guides the press-fitting direction while pre-reinforcing the existing caisson foundation. A reinforcing steel plate press-fitting step is performed in which the reinforcing steel plate 6 assembled in the steel plate assembly step is press-fitted into the ground around the existing caisson foundation F1. FIG. 6 is a process explanatory view showing a reinforcing steel plate press-fitting process of the method for reinforcing the existing caisson foundation according to the present embodiment.

In this step, since a certain press-fitting device 1 on the water surface is used to press-fit into a predetermined ground at the bottom of the water, it is necessary to increase the distance (height) from the press-fitting device 1 to the top end (upper surface) of the existing caisson foundation F1. be. Therefore, in this step, a Yatco steel plate 7 which is a temporary cylindrical body having an outer circumference substantially the same diameter (same size) as the reinforcing steel plate 6 is press-fitted above the main reinforcing steel plate 6.

At this time, as shown in FIG. 6, since it is necessary to press-fit the reinforcing steel plate 6 to a predetermined depth into the ground around the strong existing caisson foundation F1, the pressure is much higher than the pressure at which the temporary cutoff body 3 is press-fitted. High pressure is required. Therefore, although it depends on the strength of the ground, the press-fitting reaction force at the time of press-fitting becomes large, and it is assumed that the press-fitting reaction force obtained from the existing pier P1 via the anchor is not sufficient.

Therefore, in the method for reinforcing the existing caisson foundation according to the present embodiment, the temporary cut-off body 3 which is a temporary structure and the press-fitting device 1 are joined by using a steel material such as a Gevin rod, and the weight of the temporary cut-off body 3 and the temporary cut-off body 3 are joined. The frictional force between 3 and the ground may also be used as a press-fit reaction force to press the reinforcing steel plate 6 into the ground of the riverbed to a predetermined depth required for seismic reinforcement. By doing so, it is not necessary to drive an earth anchor or the like from the pontoon to the bottom of the water to obtain a reaction force as in the conventional reinforcement method described in Patent Document 1.

However, an earth anchor or the like may be driven into the bottom of the water to obtain a reaction force from the bottom of the water. Even when the reaction force is obtained from the earth anchor and press-fitted, by obtaining the reaction force from the temporary deadline 3 which is a temporary structure, the depth of driving the earth anchor into the water bottom can be made shallow, and as a result, the construction period. Can be shortened and the construction cost can be reduced.

(6. Filler filling process)
Next, in the method for reinforcing the existing caisson foundation according to the present embodiment, the filler that fills the gap between the reinforcing steel plate 6 that has been press-fitted in the pre-reinforcing steel plate press-fitting step and installed at a predetermined position and the existing caisson foundation F1. Perform the filling process.

In this step, the gap between the reinforcing steel plate 6 and the existing caisson foundation F1 is cleaned by washing off the earth and sand using a water jet or the like, and then filled with a cement-based time-curing material such as mortar to cure and reinforce the filler. The steel plate 6 is integrated with the existing caisson foundation F1 to reinforce it. Of course, the filler to be filled is not limited to the cement-based time-curing material, and may be another filler capable of integrating the reinforcing steel plate 6 such as an epoxy-based resin into the existing caisson foundation F1.

(7. Temporary structure removal process)
Next, in the method for reinforcing the existing caisson foundation according to the present embodiment, a temporary structure removal step for removing the temporary structure temporarily installed at the time of the reinforcement work is performed.

Specifically, the temporary structure such as the Yatco steel plate 7, the guide member 5, the temporary cutoff body 3, and the bracket scaffolding 8 are disassembled and removed by underwater work. In addition, the earth and sand discharged in the excavation process in the temporary deadline is backfilled as an overburden above the caisson foundation F1, and all the steps of the method for reinforcing the existing caisson foundation are completed. When this step is completed, the state shown in FIG. 7 is obtained. FIG. 7 is a diagram showing a completed state after construction of the method for reinforcing the existing caisson foundation according to the present embodiment.

According to the method for reinforcing the existing caisson foundation according to the present embodiment described above, the water pressure acting on the temporary deadline 3 is applied from the outside by not draining the water in the temporary deadline 3 to the bottom of the water in the temporary deadline excavation process. It can be reduced to a cheap and simple temporary deadline. Therefore, in the method of reinforcing the existing caisson foundation according to the present embodiment, the temporary construction cost can be reduced and the cost of the reinforcement work of the caisson foundation F1 can also be reduced.

Further, according to the method for reinforcing the existing caisson foundation according to the present embodiment, the gap between the existing pier P1 and the reinforcing steel plate 6 is narrowed by interposing the guide member 5, and the reinforcing steel plate 6 at the time of press fitting is appropriately guided. It is possible to prevent the eccentricity of the reinforcing steel plate 6. Therefore, in the method for reinforcing the existing caisson foundation according to the present embodiment, the time for eccentricity control of the reinforcing steel plate 6 can be shortened and the press-fitting work can be smoothly performed, and in this respect as well, the cost of the caisson foundation reinforcement work is reduced. can do.

In particular, according to the method for reinforcing the existing caisson foundation according to the present embodiment, at least the weight of the temporary cutoff body 3 is used, so that the reaction force at the time of press-fitting the reinforcing steel plate 6 is insufficient only by taking from the existing pier P1. , It is possible to omit driving the earth anchor or the like into the bottom of the water to secure other reaction force means, or to shorten the work period for securing other reaction force means. Therefore, the method for reinforcing the existing caisson foundation according to the present embodiment can shorten the construction period and reduce the construction cost as a result.

In particular, according to the method for reinforcing the existing caisson foundation according to the present embodiment, a Yatco steel plate 7 which is a temporary cylindrical body having an outer circumference substantially the same diameter (same size) as the reinforcing steel plate 6 is added above the reinforcing steel plate 6. Since it is press-fitted while being press-fitted, it is possible to easily reinforce even when the position of the existing caisson foundation F1 to be reinforced by the reinforcing steel plate 6 is deep.

In particular, according to the method for reinforcing the existing caisson foundation according to the present embodiment, the temporary deadline is assembled and press-fitted with the press-fitting device to install the temporary deadline, so that the time for setting the temporary deadline is shortened and the construction cost is reduced. can do.

The method for reinforcing the existing caisson foundation according to the embodiment of the present invention has been described in detail above, but the above-mentioned or illustrated embodiments all show one embodiment embodied in carrying out the present invention. Not too much. Therefore, the technical scope of the present invention should not be construed in a limited manner by these.

In particular, as a method of setting a temporary deadline, a case of press-fitting after assembling the temporary deadline has been described as an example, but as in the conventional case, a temporary deadline may be set by driving a steel sheet pile with a vibro hammer or the like. The present invention can be applied regardless of the specific installation method of the deadline.

1: Press-fitting device 2: Temporary cut-off material 3: Temporary cut-off body 4: Pressure steel material 5: Guide member 6: Reinforcing steel plate 7: Yatco steel plate 8: Bracket scaffolding B1: Existing bridge P1: Existing bridge pier F1: Existing caisson foundation

The method for reinforcing the existing cason foundation according to claim 1 is a method for reinforcing the existing cason foundation with a steel plate, and a temporary deadline is set to excavate the earth and sand above the cason foundation in the temporary deadline. In the temporary deadline excavation process, the earth and sand in the temporary deadline are removed. the with the water in the provisional deadline drilling to discharge soil while of stripping without pulling up the sea bed, the prior reinforcing steel stuffing step, the guide member installation step of installing a guide member for guiding the press-fitting of the reinforcing steel The reinforcing steel plate press-fitting step is characterized in that the reinforcing steel plate is press-fitted while guiding the press-fitting direction of the reinforcing steel plate with the guide member.

Method for reinforcing existing caisson foundation according to claim 2 is the method for reinforcing existing caisson foundation according to claim 1, in the reinforcing steel stuffing step, at least its own weight of temporarily installed the temporary structures during reinforcement work It is characterized in that the reinforcing steel plate is press-fitted by using it as a press-fit reaction force.

The method for reinforcing the existing caisson foundation according to claim 3 is the method for reinforcing the existing caisson foundation according to claim 1 or 2. It is characterized by press-fitting while adding a Yatco steel plate, which is a temporary structure of.

According to claim 4 , in the method for reinforcing an existing caisson foundation according to any one of claims 1 to 3 , the temporary deadline, which is a temporary structure, is assembled and press-fitted with a press-fitting device to install the temporary deadline. It is characterized by.

According to the inventions according to claims 1 to 4 , by not draining water to the bottom of the water in the excavation step in the temporary deadline, the water pressure acting on the temporary deadline from the outside can be reduced to make a cheap and simple temporary deadline. .. Therefore, the temporary cost can be reduced and the total cost of the caisson foundation reinforcement work can be reduced.
Further, according to the inventions according to claims 1 to 4, the problem that the gap between the reinforcing steel plate and the pier becomes large and it becomes difficult to control the eccentricity of the reinforcing steel plate is solved, and the gap between the reinforcing steel plate and the pier is narrowed at the time of press fitting. It is possible to properly guide the reinforcing steel plate of the above and prevent the eccentricity of the reinforcing steel plate.

In particular, according to the invention of claim 2 , when the reaction force at the time of press-fitting is insufficient only by obtaining from the existing pier, it is omitted to secure other reaction force means such as driving an earth anchor or the like into the water bottom. , Or the work period for securing other reaction force means can be shortened. Therefore, as a result, the construction period of the entire construction can be shortened and the construction cost can be reduced.

In particular, according to the third aspect of the present invention, it is possible to easily reinforce even when the position where the steel plate is to be reinforced is deep.

In particular, according to the invention of claim 4 , the time for setting the temporary deadline can be shortened and the construction cost can be reduced.

Claims (5)

It is a method of reinforcing the existing caisson foundation by reinforcing the existing caisson foundation with steel plates.
An excavation process in the temporary deadline to set up a temporary deadline and excavate the earth and sand above the caisson foundation in the temporary deadline.
It is equipped with a reinforcing steel plate press-fitting process in which a reinforcing steel plate that reinforces the caisson foundation is press-fitted into the ground around the existing caisson foundation.
In the temporary deadline excavation step, a method for reinforcing an existing caisson foundation is characterized in that the earth and sand in the temporary deadline is excavated and discharged while the water in the temporary deadline is not drained to the bottom of the water. Prior to the reinforcing steel plate press-fitting process, there is a guide member installation step of installing a guide member for guiding the press-fitting of the reinforcing steel sheet.
The method for reinforcing an existing caisson foundation according to claim 1, wherein in the reinforcing steel plate press-fitting step, the reinforcing steel plate is press-fitted while guiding the press-fitting direction of the reinforcing steel plate with the guide member. The method for reinforcing an existing caisson foundation according to claim 2, wherein in the reinforcing steel plate press-fitting step, the reinforcing steel plate is press-fitted by using at least its own weight of a temporary structure such as a temporary cutoff as a press-fitting reaction force. The existing caisson according to claim 2 or 3, wherein in the reinforcing steel plate press-fitting step, a Yatco steel plate, which is a temporary structure having substantially the same size as the reinforcing steel plate, is press-fitted above the reinforcing steel plate. How to reinforce the foundation. The method for reinforcing an existing caisson foundation according to any one of claims 1 to 4, wherein the temporary deadline, which is a temporary structure, is assembled and press-fitted by a press-fitting device to install the temporary deadline.

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