JPH0776844A - Method of settling open caisson - Google Patents

Abstract

PURPOSE:To reduce the construction period and cost required for a deep vertical shaft and solve high hydraulic pressure counter-measures and all other problems, by safely settling an open caisson at a high hydraulic pressure condition. CONSTITUTION:In a method of settling an open caisson having a hollow space 34 in the caisson frame body 24, a number of groove holes 12 having a larger width than the thickness of caisson frame body 24 are formed up to a specified installation depth of the caisson and mud 20 is charged in the groove holes 12. The caisson frame body 24 having a plurality of hollow spaces 34 vertically connected is constructed. One lot of open caisson is settled while discharging the mud 20 in the groove holes 12 from the hollow spaces 34. The ground within the space surrounded by the caisson frame body 24 is excavated in the water. This work is repeated to settle the caisson while always penetrating the blades of caisson into the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sunk open caisson, and more particularly to roads, railways, sewers, underground discharge channels,
The present invention relates to a method for laying an open caisson for constructing a deep shaft such as a deep water pipe, an energy storage deep underground tank, etc.

[0002]

2. Description of the Related Art In general, when constructing a shaft, the open caisson method is effective because the mechanical equipment is relatively simple and the construction cost is low.

In the open caisson method, a caisson frame made of reinforced concrete is used to construct a cylindrical caisson, and the caisson is sunk into the ground while excavating the inside of the caisson to reach a predetermined depth.

The open caisson method is effective for constructing a shallow shaft, but
When constructing a deep shaft with a depth of 40 meters or more, heaving, boiling, blistering, piping, etc. are likely to occur due to high water pressure, which makes construction difficult.

Therefore, when constructing a deep shaft with a depth of 40 meters or more, a continuous underground wall construction method or a pneumatic caisson construction method has been adopted as a measure against high water pressure.

In the continuous underground wall construction method, the excavation groove is filled with a stabilizing liquid to prevent the wall surface from collapsing, and the excavation machine is used to excavate the slot hole. Slime treatment, reinforced cage construction, concrete placing, etc. The process was repeated to build underground continuous walls every 3 to 7 meters, and to support the continuous walls by constructing support works along the continuous walls.

In the pneumatic caisson method,
The work chamber with a slab structure at the bottom is designed to sink the soil and reach it to reach a predetermined support layer.In order to remove water that enters the work chamber, compressed air is supplied to the work chamber. I was trying to supply.

[0008]

In the case of the above-mentioned conventional continuous underground wall construction method, a rebar cage is built and concrete is laid every 3 to 7 meters of excavation to construct a unit element of the continuous wall. In addition, there is a problem that it is necessary to form a support work to support the work, which requires a long construction period and may require several years in some cases.

Further, due to the infiltration of high-pressure groundwater from the lower end of the continuous wall, heaving, boiling, or blistering,
There is a high risk of piping and the like, and as a countermeasure against this, it is necessary to make the rooting length considerably large, which causes a problem of cost increase.

Further, when the pneumatic caisson method is used, groundwater can be safely conquered, but it is work under pressure, and if the pressure increases, it takes a lot of time to pressurize and depressurize for health management. There was a problem that the actual work time became extremely short, the work efficiency decreased, and the construction period took a long time.

Further, not only at a large depth but also at the time of constructing a shallow shaft or the like, there is a similar problem in the sandy ground having a large hydraulic conductivity.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to enable an open caisson to be safely submerged under a high water pressure condition so that a deep shaft and a hydraulic conductivity can be obtained. It is to provide a method for laying open caisson that can solve all the problems such as shortening the construction period, cost reduction, and measures against high water pressure required for large sandy ground.

[0013]

According to the first invention,
A method of sinking an open caisson having a hollow portion inside the body, wherein a large number of slots having a width slightly larger than the thickness of the body of the open caisson are formed up to a predetermined open caisson installation depth at the sinking position of the open caisson. And, after filling the slot with mud, a step of constructing a caisson skeleton having a plurality of vertically communicating hollow portions,
The step of constantly depositing one lot of open caisson while discharging the mud in the groove from the hollow portion and the step of underwater excavating the ground in the space surrounded by the caisson skeleton are repeated. The feature is that it is submerged while rooting the part.

The second aspect of the invention is characterized in that the specific gravity of the mud is at least 1.3 or more.

The third aspect of the invention is characterized in that, in the step of sinking the open caisson, the mud is retained in the hollow portion to act as a load.

According to a fourth aspect of the present invention, in the step of sinking the open caisson, a pressing force acts on the open caisson by using an anchor member fixed on the ground deeper than a predetermined installation depth of the open caisson as a reaction force. Is characterized by.

A fifth aspect of the invention is characterized in that the groove holes are formed discontinuously in a plane.

The sixth invention is characterized in that the discontinuous portion of the groove hole is excavated by jetting high-pressure water.

[0019]

In the first aspect of the present invention, mud is filled in a large number of slots formed up to the installation depth of the open caisson, and the open caisson for one lot is sunk while discharging the mud, thereby vertically moving. A caisson skeleton with a plurality of communicating hollow parts can be laid down so that it floats in the mud, and can be laid down while adjusting the discharge amount of the mud to balance the weight, enabling stable caisson skeleton laying. Become.

In addition, when the open caisson is sunk, the ground sand content around the caisson wall may collapse and the wedge phenomenon may increase the sinking frictional resistance. However, the mud filled in the slot serves as a lubricant. It becomes possible to reduce the frictional resistance due to sinking.

Further, advance the caisson blade penetration,
After that, by performing underwater excavation of the ground in the space surrounded by the caisson frame, it is possible to efficiently perform internal excavation without having to worry about the effect on the surroundings of the caisson frame, thus shortening the construction period. It will be possible.

Further, by advancing the caisson blade intrusion first, it is not necessary to excavate under the blade in underwater excavation, and it is possible to efficiently perform the digging. In addition, the surroundings of the blade are not overexposed, and the collapse and loosening of the ground can be prevented.

In the second aspect of the present invention, by setting the specific gravity of the mud to be at least 1.3 or more, the caisson skeleton can be gently sunk and stable deposition can be performed.

According to the third aspect of the invention, the mud is retained in the hollow portion to act as a load, so that the buoyancy can be easily adjusted when the open caisson is sunk, and a small pressing force is applied. With this, it is possible to sunk the open caisson while controlling the attitude. Further, if the caisson own weight is dominant in the total settlement resistance, there is an effect of reducing the apparent unit volume own weight of the caisson body, and it becomes possible to facilitate the sinking.

In the fourth invention, by using the anchor member as a reaction force, it becomes possible to exert a sufficient pressing force against the open caisson.

According to the fifth aspect of the present invention, the groove holes are formed discontinuously in a plane, so that the groove holes can be formed easily and the construction period can be shortened as compared with the case where the groove holes are formed continuously. Can be realized.

According to the sixth aspect of the present invention, the discontinuous portion can be made large by excavating the discontinuous portion of the groove hole by jetting high-pressure water. It is possible to prevent collapse due to water pressure difference and perform stable construction.

[0028]

Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 9 are views showing a method of sinking an open caisson according to an embodiment of the present invention.

First, as shown in FIG. 1, a guide wall 10 for excavating a slot is installed at a position where an open caisson is to be sunk. The guide wall 10 serves as a guide for trench excavation of a slot for digging an open caisson, and has a width slightly larger than the thickness of the skeleton of the open caisson. Further, in this embodiment, a circular open caisson is used, and the guide wall 10 is also arranged in a circular shape along the shape of the open caisson.

Next, as shown in FIG. 2, along the guide wall 10 installed at the sunk position of the open caisson,
A large number of slots 12 for digging open caissons are formed by excavation. In this case, prior to excavation of the slot 12, a steel sheet pile 14 is driven on the outer peripheral side of the guide wall 10 to form a protective edge cut wall to prevent deformation of the ground.

The slot 12 is formed by trench excavation. As shown in FIG. 7, three continuous excavations 16A, 16B, 16C are formed as one element, and each slot 12 is formed. The elements are formed so as to be discontinuous in a plane. Therefore, it is not necessary to process end portions such as a gable stopper between the elements, and the work period can be shortened. The ground 18 at the discontinuous portion is set to a thickness that does not easily collapse due to the water pressure difference in the adjacent slot 12.

Further, the width of each groove 12 is set to be slightly larger than the thickness of the body of the open caisson according to the width of the guide wall 10, and the depth of each groove 12 is excavated to a predetermined open caisson installation depth. It is formed. For example,
The excavation depth of the slot 12 is set to 50 m or more. In this way, by excavating the slot 12 in advance to a predetermined open caisson installation depth, the caisson frame can be submerged without excavating under the caisson blade when the open caisson is submerged, which shortens the construction period and reduces the cost. Down is possible.

When the excavation depth is up to about 50 m, the guide hole is not required by excavating the groove hole by using the multi-axis auger, and the construction period and the construction cost can be further shortened. It becomes possible (see FIG. 10).

After the excavation of the slot 12, the excavated mud in each slot 12 is replaced with the mud 20. The mud 20 is prepared by mixing the excavated soil or adjusting the blending components so that the specific gravity is at least 1.3 or more, preferably 1.4 or more. In this way, by substituting the mud soil 20 having a specific gravity of 1.3 or more, the caisson skeleton can be stably deposited. Further, the specific gravity of the mud 20 is appropriately determined in consideration of the relationship with the specific gravity of the caisson frame to be sunk.

Then, as shown in FIG. 3, a caisson blade 22 is installed on the slot 12, and a caisson frame 24 is constructed on the caisson blade 22 and connected. In this case, prior to the installation of the caisson blade 22, the ground inside the protective edge cut wall formed by the steel sheet pile 14 is open-drilled in the air for about 3 m. Further, since the upper portion of each slot 12 requires a large blade edge supporting force at the initial stage of the caisson blade edge 22 sunk, the blade edge supporting force is increased by sand-displacing the supporting portion 26. ing. Therefore, when the caisson blade 22 is placed on the slot 12 and is sunk, the supporting portion 2
The caisson blade 22 is surely supported by 6 and a stable sinking is possible. In addition, the support portion 26 is not limited to the above sand replacement, and for example, it is also possible to mix a muddy water solidifying material in the upper part of the slot 12 to enhance the strength, and further, if necessary, muddy water for each depth. It is also possible to change the composition of the solidifying material so that the optimum state of deposition can be obtained.

Further, between the groove hole 12 and the steel sheet pile 14,
The anchor member 28 is fixed to the ground deeper than a predetermined open caisson installation depth, the anchor member 28 is connected to the caisson blade 22 via a hydraulic jack 30, and the anchor member 28 is pushed to the caisson blade 22 as a reaction force. I try to apply pressure. Therefore, it is possible to apply a sufficient pressure input to the caisson blade 22. The anchor member 28 is composed of a ground anchor 31 and an anchor steel rod 32.

Further, as shown in FIGS. 8 and 9, the caisson skeleton 24 has a plurality of hollow portions 3 which are vertically communicated with each other.
4 has a diameter of 30 meters in this embodiment,
The wall thickness is set to about 2 to 3 meters. The caisson skeleton 24 is built in advance in a factory or on site. Then, the sludge discharge pipe 36 is inserted into the hollow portion 34, and the lower end of the sludge discharge pipe 36 is exposed from the lower part of the caisson blade 22. Also, the sludge pipe 36
The buoyancy adjusting valve 3 is provided at an appropriate position in the hollow portion 34.
8 is attached. Further, the ratio of the hollow portion 34 to the caisson body 24 is about 44%, and the mud soil 20
It is designed so that the specific gravity can be balanced. Further, a blade fitting 40 is attached to the lower end of the caisson blade 22, and a dowel streak 42 is previously attached above the blade fitting 40.

Next, as shown in FIG. 4, the caisson blade 22 installed on the groove 12 is pressed by the hydraulic jack 30 to be press-fitted into the groove 12 and connected to the caisson 22. The caisson frame 24 for one lot is sunk.
Further, when the caisson skeleton body 24 is press-fitted, the caisson skeleton body 24 is laid down in the slot 12 so as to float in the water while discharging the mud 20 from the lower end of the mud discharge pipe 36. In this case, if necessary, the valve 38 for adjusting the buoyancy provided in the mud discharge pipe 36 is opened and closed to fill the mud 20 in the hollow portion 34 of the caisson body 24, and the buoyancy is adjusted and balanced while in a suitable state. I'm trying to sink it. It is also possible to balance while filling the hollow portion 34 with a water load or concrete.

Further, the caisson blade 22 can be broken down by the weight of the caisson frame 24 in the discontinuous ground 18 left between the slots 12, and the discontinuous ground 18 is It effectively acts as a blade edge supporting force. Further, when the distance between the grounds 18 in the discontinuous portion is large and the caisson body 24 cannot be cut down by its own weight, a pipe 45 for supplying high-pressure water is inserted into the hollow portion 34 of the caisson body 24. It is also possible that the lower end of the pipe is exposed to the caisson blade 22 and high pressure water is jetted from the lower end of the pipe 45 to excavate the ground 18 in the discontinuous portion while sinking.

Further, when the mud material which has been replaced in advance is subjected to an overload and a caisson pressure input and becomes a compaction state, and the caisson skeleton body 24 does not smoothly press-fit, a high-pressure hydraulic injection provided in the hollow portion is injected. Fluidize again by
It can also be made easier to deposit.

Next, the muddy water 46 is supplied onto the ground surrounded by the caisson frame 24 to excavate the ground surrounded by the caisson frame 24 underwater. In this case, since the caisson blade 22 is submerged prior to the excavation of the ground in the space surrounded by the caisson frame 24, it is not necessary to excavate the lower part of the caisson blade 22 during underwater excavation, and the caving is easy. Therefore, it can contribute to shortening the construction period. And caisson body 24
The construction of the caisson skeleton 24 for one lot and the underwater excavation of the ground in the internal space surrounded by the caisson skeleton 24 are alternately repeated to reach the predetermined open caisson installation depth shown in FIG. 24 is sunk. In this case, the caisson skeleton 24 having a length of 1 to 2 lots is advanced while being press-fitted prior to the internal excavation depth.

Then, as shown in FIG. 5, with the fresh water 46 stretched, the bottom of the floor is leveled, and after the slime treatment, the rebar is assembled on the bottom, and the underwater concrete is placed, and the base of the bottom board is placed. 48 is formed. In this case, since the gbelber 42 is attached to the caisson blade 22 in advance, the bottom base portion 48 and the caisson blade 22 are surely integrated. Further, a back-filling material 50 is filled around the caisson body 24 and sealed.

Then, as shown in FIG. 6, after drainage treatment of the muddy water 46 is performed, the reinforcing bars are assembled in the air on the bottom plate foundation portion 48 formed in water, and concrete is poured to form the bottom plate 52.
To form. After that, the hydraulic jack 30 and other equipment are removed, the steel sheet pile is pulled out, and further, the hollow portion 34 of the caisson frame 24 is filled with concrete and solidified, whereby the vertical shaft is completed. When the lift force from the bottom of the vertical shaft is large, it is possible to form the bottom plate base portion 48, the bottom plate 52 and the like with heavy concrete to increase the overall weight to counter the lift force.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the gist of the present invention.

For example, the caisson body has a circular shape with a diameter of 30 meters and a wall thickness of 2 to 3 meters.
Not limited to this example, it is needless to say that various shapes such as a rectangular shape and an elliptical shape and various sizes can be adopted.

Further, in the above-mentioned embodiment, the groove holes are formed discontinuously in the plane, but it is needless to say that the groove holes may be formed continuously depending on the ground and other circumstances.

Further, in the above embodiment, the anchor member 2 is used.
Although 8 is provided on the outside of the caisson frame 24, the present invention is not limited to this example, and by using the inside of the hollow portion 34 formed in the caisson frame 24 to install the anchor member, it can be used as a permanent anchor. It can be advantageous.

[0049]

As described above, according to the first aspect of the present invention, a plurality of hollow portions are formed by sinking open caisson while discharging mud in a large number of slots formed up to the installation depth of the open caisson. The caisson skeleton skeleton can be sunk while floating in the mud, and can be sunk while adjusting the discharge amount of the mud to balance the weight, and the caisson skeleton can be stably sunk.

In addition, when the open caisson is sunk, the mud filled in the slots can act as a lubricant to reduce the settlement frictional resistance.

Furthermore, advance the caisson blade penetration,
After that, by excavating the ground in the space surrounded by the caisson skeleton underwater, it is possible to efficiently perform internal excavation without worrying about the effect on the surroundings of the caisson skeleton and shorten the construction period. There is an effect.

Further, by advancing the caisson blade intrusion, it is not necessary to dig under the blade for underwater excavation, and it is possible to economically and efficiently perform the digging. There is no effect of digging and there is an effect that the collapse and loosening of the ground can be prevented.

According to the second aspect of the present invention, by setting the specific gravity of the mud to be at least 1.3 or more, there is an effect that the caisson skeleton can be gently sunk and stable deposition can be performed.

In the third aspect of the invention, the mud is retained in the hollow portion and acts as a load, so that the buoyancy can be easily adjusted when the open caisson is sunk, and a small pressing force is applied. The effect is that the open caisson can be sunk while controlling the attitude. Further, if the caisson own weight is dominant in the total settlement resistance, there is an effect of reducing the apparent unit volume own weight of the caisson body, and it becomes possible to facilitate the sinking.

According to the fourth aspect of the invention, by using the anchor member as a reaction force, it is possible to exert a sufficient pressing force against the open caisson.

According to the fifth aspect of the present invention, the groove holes are formed discontinuously in a plane, so that the groove holes can be formed more easily than in the case where the groove holes are continuously formed, and the construction period can be improved. There is an effect that it can be shortened.

In the sixth aspect of the invention, the discontinuous portion can be made large by excavating the discontinuous portion of the groove hole by jetting high-pressure water, and the water pressure of the discontinuous portion at the time of forming the groove hole can be increased. There is an effect that it can be prevented from collapsing and can be stably constructed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a guide wall installation state in an open caisson sinking method according to an embodiment.

2 is a cross-sectional view showing a state in which a slot is excavated from the state of FIG. 1 and filled with mud.

FIG. 3 is a cross-sectional view showing a state in which an anchor is installed and a caisson blade mouth is sunk from the state of FIG.

FIG. 4 is a cross-sectional view showing a state in which caisson deposition and underwater excavation are repeated from the state of FIG.

FIG. 5 is a cross-sectional view showing a state in which caisson deposition and underwater excavation are completed from the state of FIG. 4 to form a bottom base portion in water.

6 is a cross-sectional view showing a state in which muddy water is drained from the state of FIG. 5 to form a bottom plate in the air.

FIG. 7 is a cross-sectional view showing an excavated state of the slot of FIG.

8 is a cross-sectional view showing the caisson blade of FIG.

FIG. 9 is a plan view of a caisson body.

FIG. 10 is a plan view showing a state in which a groove hole has been excavated using a multi-axis auger.

[Explanation of symbols]

 12 Groove 20 Mud 22 Caisson blade 24 Caisson frame 28 Anchor member 34 Hollow part 36 Drainage pipe 46 Muddy water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoaki Sato 1-7-1, Kyobashi, Chuo-ku, Tokyo Toda Construction Co., Ltd.

Claims (6)

[Claims] 1. A method of sinking an open caisson having a hollow portion inside a body, wherein a slot having a width slightly larger than the thickness of the body of the open caisson is provided at a predetermined position of the open caisson. After forming a large number to the depth and filling the groove with mud, constructing a caisson skeleton having a plurality of vertically communicating hollow portions, while discharging the mud in the groove from the hollow portion. It is characterized in that the process of digging one lot of open caisson and the process of excavating the ground in the space surrounded by the caisson frame underwater are repeated to constantly dig in the root of the blade. How to lay open caisson. 2. The method for laying open caisson according to claim 1, wherein the specific gravity of the mud is at least 1.3 or more. 3. The method according to claim 1, wherein, in the step of digging the open caisson, the mud is retained in the hollow portion to act as a load. 4. In the step of sinking the open caisson, an anchor member fixed to the ground deeper than a predetermined open caisson installation depth applies a pressing force to the open caisson as a reaction force. How to lay down the described open caisson. 5. The method of depositing an open caisson as claimed in claim 1, wherein the slots are formed discontinuously in a plane. 6. The method according to claim 1, wherein the discontinuous portion of the slot is excavated by jetting high-pressure water.