JP4837618B2 - Caisson press-in method - Google Patents

Description

  The present invention relates to a caisson press-in method for forming a foundation of a structure such as a bridge pier or a shield shaft.

The caisson method is a technique for forming the foundations of large towers, piers, etc. by sinking hollow cylindrical caissons made of precast concrete members or constructed at the installation position in the bottom of the water or the ground. For example, a press-fitting caisson method in which a caisson is press-fitted by taking a reaction force from the ground is described in Patent Documents 1 and 2 listed below.
JP 2000-204563 A Japanese Patent Laid-Open No. 8-177055

  As shown in Patent Document 1, the press-fitting caisson method, as shown in FIG. 12, connects the gripper rod 2 to the ground anchor 1 driven into the ground, and constructs a cylindrical caisson housing 3 having a blade edge, The reaction force girder 5 is placed on the upper surface of the caisson housing 3 via the pressure bearing plate 4, and the gripper rod 2 is pulled by the press-fit jack 6 attached to the reaction force girder 5 while excavating the inner ground of the caisson housing 3. The ground anchor 1 takes the reaction force and overcomes the cutting edge resistance and the peripheral friction force to press-fit (sink) the caisson housing 3 into the ground.

  After the caisson housing 3 is press-fitted for a predetermined length, the next caisson housing 3 is constructed on the top of the caisson housing 3 that has been press-fitted, and the caisson housing 3 is press-fitted into the ground in the same manner as described above. The caisson housing 3 is press-fitted to a predetermined depth by repeating this operation a plurality of times.

  Simultaneously with the press-fitting of the caisson housing 3, the ground inside the caisson housing 3 is excavated with an excavating machine, for example, a clamshell bucket.

  In such press-fitting of the caisson housing 3, when the caisson housing 3 is press-fitted into an extremely soft ground having an N value close to 0, the ground supporting force is insufficient, and there is a risk of over-sinking or self-sinking. As a countermeasure, conventionally, the N value has been increased by improving the ground.

Although it is not a press-in caisson method, there is the following patent document as a caisson settlement control method that can arbitrarily control the settlement of a frame even in soft ground or the like.
JP 2004-44242 A JP 2001-164578 A

  Patent Document 3 discloses a pneumatic caisson method in which an expansion / contraction mat body that can be expanded / contracted outward is installed on the outer peripheral surface portion of the frame, and the expansion / contraction control of the expansion / contraction mat body according to the ground type is performed. This adjusts the peripheral frictional force.

  Patent Document 4 is an open caisson method, provided at the upper end portion of the caisson, and provided between a plurality of support columns elongated in the axial direction of the caisson and the upper end portion of the support column. A caisson oversinking prevention device characterized in that a stopper beam projecting outward from the caisson is provided.

  The material of the expansion mat body of Patent Document 3 is, for example, a rubber material having flexibility and excellent wear resistance, specifically, synthetic rubber such as chloroprene rubber, styrene butadiene rubber, butyl rubber, or recycled rubber. Can be preferably used. The expansion / contraction operation of the expansion mat body is controlled by supplying a working fluid such as air, water or oil to the inside of the expansion mat body or drawing it out through a working fluid conduit embedded in the side wall of the housing. Is done.

  In Patent Document 4, since the end portion is provided with a stopper beam protruding outward from the caisson, when the caisson is set in the ground, the oversink prevention device is installed at the upper end of the caisson. The caisson can be submerged in the ground until the stopper beam contacts the ground surface. In other words, when the stopper beam comes into contact with the ground surface, the caisson can be prevented from sinking and the caisson can be prevented from further sinking.

  However, neither Patent Document 3 nor Patent Document 4 is suitable for increasing the supporting force when the press-fitting caisson is press-fitted. However, in the case of Patent Document 3, it is applied in the pneumatic caisson method, and when the outer peripheral surface of the caisson is appropriately expanded and expanded to increase the friction between the caisson and the surrounding ground, the press-in subsidence is performed. Will exert an excessive force on the expansion mat body, and the required frictional resistance will not be obtained, and there is also a risk of damage.

  In Patent Document 4, the stopper beam cannot act when the caisson sinks into the ground, and cannot increase the support force when the press-fitting caisson is pressed.

  The object of the present invention is to eliminate the inconvenience of the conventional example, without pressing the soft soil by pressing the soft soil with a flat plate, the caisson housing can have a supporting force as its reaction force, the ground supporting force is insufficient It is an object of the present invention to provide a caisson press-in method that can eliminate the risk of over-sinking or self-sinking.

  In order to achieve the above object, the present invention as set forth in claim 1 is a guide formed on a caisson housing in a caisson press fitting method in which a caisson housing is press-fitted and submerged with a press-fitting jack using a ground anchor installed in the vicinity of the caisson housing as a reaction force. The gist is to drop a flat plate such as a steel plate along the groove toward the excavator at the inner tip of the caisson housing, and fix the flat plate to support the caisson housing which is press-fit and sink.

  According to the first aspect of the present invention, the flat plate is pushed down toward the excavator at the inner tip of the caisson housing, and this flat plate is fixed so that the flat plate suppresses the soft soil rising from the bottom when the caisson housing is press-fitted. As a reaction force, the Caisson body will have support.

  The gist of the present invention described in claim 2 is to fix the flat plate by dropping the rod-shaped body along the guide groove formed in the caisson housing and pressing the flat plate support portion in the guide groove from above.

  According to the second aspect of the present invention, in order to fix the flat plate, the rod-shaped body is dropped along the guide groove formed in the caisson housing, and the flat plate support portion in the guide groove is pressed from above, so that It can be done easily and reliably under the ground.

  The gist of the present invention described in claim 3 is that a reinforcing frame is attached to the flat plate in order to give strength.

  According to the third aspect of the present invention, in order to give strength to the flat plate itself, the thickness of the flat plate increases and the weight also increases. However, by adding a reinforcing frame, the strength of the flat plate itself is not increased. Can be improved.

  The gist of the present invention described in claim 4 is that an opening is provided between the flat plate and the caisson housing or / and between the flat plates, and the earth and sand are excavated through the opening.

  According to the fourth aspect of the present invention, the excavation when the caisson housing is press-fitted and subsidized has an opening between the flat plate and the caisson housing or / and between the flat plates, and the earth and sand are passed through the opening. Since it excavates, it can carry out without pulling up the fixed flat plate.

  According to the fifth aspect of the present invention, the caisson housing is set in one or more times for one rod of the caisson housing, and the installation position of the flat plate to be dropped toward the excavator is the height of the set-up once. The gist is to set the height of the settling after the excavation to the settling completion position at which the flat plate comes into contact with the excavator.

    According to the fifth aspect of the present invention, during the laying operation, the sunk height (sinking amount) can be controlled once by fixing the flat plate to be fixed higher than the bottom excavator. The fixed height of the flat plate can be adjusted by the insertion depth of the rod-shaped body.

  As described above, the caisson press-fitting method of the present invention is capable of giving support force to the caisson frame as a reaction force by pressing soft soil with a flat plate without improving the ground. It is possible to eliminate the risk of over-sinking or self-settling caused by

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing a first embodiment of the caisson press-in method according to the present invention, and FIG. 2 is a vertical side view of the same. First, the press-in caisson method as a premise of the present invention will be described.

  As shown in FIG. 4, a ground anchor 1 for press-fitting reaction force is installed using a boring machine 9 or the like. After curing the grout, perform a tensile test to check the yield strength.

  As shown in FIG. 5, the floor of the construction foundation surface is prepared so as not to be sunk unevenly by the load of the first lot, and the plate 8 is installed.

  As shown in FIG. 6, the blade metal fitting 7 is installed at a predetermined position, and as shown in FIG. 7, as the first lot construction of the caisson housing 3, the concrete is cast after assembling the scaffolding, the reinforcing bars, and the formwork. And wait for the curing period to remove the frame.

  As shown in FIG. 8, press-fitting equipment is installed and the posture is controlled by controlling the pressure input of each jack, and the ground anchor 1 installed in the vicinity of the caisson housing 3 by excavating and discharging the internal soil is used as a reaction force. The caisson housing 3 is sunk by press-fitting with the press-fitting jack 6.

  In the press-fitting and excavation of the caisson housing 3, the gripper rod 2 is directly or indirectly connected to the ground anchor 1 to construct a cylindrical caisson housing 3 having a cutting edge, and a pressure bearing plate is formed on the upper surface of the caisson housing 3. 4, the reaction force girder 5 is placed, the gripper rod 2 is pulled with the press-fit jack 6 attached to the reaction force girder 5, and the reaction force is taken with the above-mentioned ground anchor 1 to overcome the cutting edge resistance and the peripheral friction force. The caisson housing 3 is pressed into the ground. In the figure, reference numeral 10 denotes a clamshell bucket for excavation.

  After completing the press-fitting and setting of 1 rod, the gripper rod 2, press-in jack 6, reaction force girder 5, etc. are removed, and the second lot of caisson housing 3 is removed by bracket / stage installation, inner / outer scaffold assembly, etc. Prepare for construction, rebar assembly, formwork assembly, concrete placement, formwork / scaffold dismantling, and press-fit equipment again.

  Thereafter, as shown in FIG. 9, the caisson housing 3 is laid down by repeating the construction and the laying down.

  As shown in FIG. 10, the caisson housing 3 is submerged to a predetermined depth by press-fitting excavation in the final lot, and it is confirmed whether the bottom surface of the excavation is uneven and the remaining soil at the blade edge is removed. (Caisson installation completed)

  As shown in FIG. 11, the slime deposited on the bottom surface of the pit is processed to place the underwater slab concrete 11.

  As an example of construction, in order to install structures in the river without hindering the planned riverbed, banking is performed in a fence made by steel sheet pile closure, and the bridge pier foundation is specified by the caisson. This is the case when installing at a depth.

  In the caisson press fitting method in which the caisson casing is press-fitted and submerged with a press-fitting jack using the ground anchor installed in the vicinity of the caisson casing as described above, the present invention provides a guide groove 12 in the caisson casing 3 as shown in FIG. Form.

  If the caisson housing 3 has the partition wall 3a, the guide groove 12 may be provided directly on the partition wall 3a. The caisson housing 3 may be formed in the partition wall 3a, and the outer surface may be made of steel or the like. This may be formed by attaching a rail member. In any case, it is like a bag groove, and when a support part 14 of a flat plate 13 to be described later is dropped from above and engaged, the support part 14 continues vertically with a narrow slit opening so that the support part 14 does not come out. Things are desirable.

  A caisson in which a flat plate 13 having a support portion 14 is dropped along the guide groove 12 toward the excavator at the inner tip of the caisson housing 3, and the flat plate 13 is fixed at an appropriate position higher than the installation completion position α and press-fitted and submerged. Support the housing 3.

  The flat plate 13 may be made of any material such as steel or concrete as long as it has a certain degree of strength depending on the thickness. However, the flat plate 13 may be provided with a truss structure or other reinforcing frame 15 in order to provide strength. .

  The support portion 14 of the flat plate 13 is a joint having a large T-shaped head corresponding to the cross section of the guide groove 12, and the flat plate 13 is fixed by dropping the rod-shaped body 16 along the guide groove 12. The support part 14 is pressed from above. The rod-shaped body 16 is preferably a steel material having a T-shaped cross section that is the same as the shape of the support portion 14.

  By fixing the flat plate 13 in this way and pressing the soft soil that rises on the flat plate 13, the caisson housing 3 that is press-fitted and subsidized can be supported, and oversink or self-sink can be prevented.

  Since the opening 17 is provided between the flat plate 13 and the caisson housing 3, the internal earth and sand is excavated and discharged, and the ground anchor 1 installed in the vicinity of the caisson housing 3 is used as a reaction force to be press-fitted with the press-in jack 6. Thus, the excavation and earth excavation when the caisson housing 3 is sunk is excavated through the opening 17.

  The closing of the excavator at the inner tip of the caisson housing 3 by the flat plate 13 is performed symmetrically about the center of the caisson housing 3 in order to ensure the balance of the sinking of the caisson housing 3. As a result, the portion of the opening 17 at the inner tip of the caisson housing 3 without the flat plate 13 is also symmetric, and a settlement balance is obtained.

  In addition, as shown in FIG. 3, the entire excavation plate at the inner tip of the caisson housing 3 is divided into a plurality of flat plates 13 and designed so that the flat plate 13 of the presser can be attached to the whole. Thus, the cover range of the flat plate 13 may be determined.

  As described above, when a plurality of flat plates 13 are used and the entire excavator at the inner tip of the caisson housing 3 is divided into several, openings 17 are formed between the flat plate 13 and the caisson housing 3 and between the flat plates 13. Therefore, excavation and excavation when the caisson enclosure 3 is submerged by press-fitting with the press-in jack 6 by using the ground anchor 1 installed in the vicinity of the caisson enclosure 3 as a reaction force by excavating and excavating the internal soil and sand, Sediment is excavated through the opening 17.

  In order to obtain the support force of the next rod load by the reaction force girder 5 built on the upper part of the caisson housing 3, after caisson is laid down at a predetermined position, pressure is applied to the required load with the press-in jack 6 and the load is released. Keep it.

  In addition, during the laying operation, the caisson housing 3 is laid down for one rod in one or a plurality of times, and the holding plate 13 to be dropped toward the excavator is installed at a position higher than the bottom laying completion position α by a certain amount. By fixing to β, it may be used for controlling the set height (set amount) once. The fixed height of the flat plate 13 can be adjusted by the insertion depth of the rod-like body 16.

  In this way, the holding plate 13 is set and fixed at a certain height higher than the bottom settling completion position α, and the earth and sand are excavated through the opening 17 so that the set height (set amount) at one time is excavated. It is possible to control up to the position where the settling is completed.

It is a top view which shows 1st Embodiment of the press-fitting method of the caisson of this invention. It is a vertical side view which shows 1st Embodiment of the press-fitting method of the caisson of this invention. It is a top view which shows 2nd Embodiment of the press-fitting method of the caisson of this invention. It is a vertical side view which shows the 1st process of a press fit caisson method. It is a vertical side view which shows the 2nd process of a press fit caisson method. It is a vertical side view which shows the 3rd process of a press fit caisson method. It is a vertical side view which shows the 4th process of a press fit caisson method. It is a vertical side view which shows the 5th process of a press fit caisson method. It is a vertical side view which shows the 6th process of a press fit caisson method. It is a vertical side view which shows the 7th process of a press fit caisson method. It is a vertical side view which shows the 8th process of a press fit caisson method. It is explanatory drawing of a press fit caisson method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Grand anchor 2 ... Gripper rod 3 ... Caisson housing 3a ... Bulkhead 4 ... Pressure plate 5 ... Reaction force girder 6 ... Press-fit jack 7 ... Blade fitting 8 ... Dish plate 9 ... Boring machine 10 ... Clamshell bucket 11 ... Underwater Bottom slab concrete 12 ... Guide groove 13 ... Flat plate 14 ... Support part 15 ... Reinforcement frame 16 ... Bar-shaped body 17 ... Opening

Claims (5)

  In the caisson press-fitting method in which the caisson housing is press-fitted and submerged with a press-fit jack using the ground anchor installed in the vicinity of the caisson housing as a reaction force, a flat plate such as a steel plate is attached to the inner tip of the caisson housing along the guide groove formed in the caisson housing. A caisson press-in method, characterized in that the caisson housing is supported by a caisson housing that is dropped into the excavator and fixed and pressed down.   The caisson press-fitting method according to claim 1, wherein the flat plate is fixed by dropping the rod-shaped body along the guide groove formed in the caisson housing and pressing the flat plate support portion in the guide groove from above.   The caisson press-in method according to claim 1 or 2, wherein a reinforcing frame is attached to the flat plate to give strength.   The caisson press-fitting method according to any one of claims 1 to 3, wherein an opening is provided between the flat plate and the caisson housing or / and between the flat plates, and the earth and sand are excavated through the opening.   The caisson housing is installed in one or more times for one rod of the caisson housing, and the installation position of the flat plate to be dropped toward the excavator is higher than the completion position of the installation by one scheduled installation height. The caisson press-fitting method according to any one of claims 1 to 4, wherein the caisson press-fitting method according to any one of claims 1 to 4, wherein the caisson is installed and controlled once after the excavation to a setting completion position where the flat plate comes into contact with the excavator.

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