JP3796576B2 - Shaft rebar fixing method in underwater confined construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an underwater confined construction method, which is one of the reinforcement methods for existing structures in water, and more particularly to a fixing method for axially reinforced reinforcing bars positioned as one step of the construction method.
[0002]
[Prior art]
The confined construction method is one of reinforcement methods mainly for the purpose of strengthening the earthquake resistance of existing piers. Since the present invention relates to the seismic reinforcement method when the pier stands from the bottom of the water and the footing part is underwater, that is, the underwater confined method, first, a typical example of the conventional method will be briefly described.
[0003]
FIG. 4 is a schematic side view of the pier 20 after construction by a conventional typical underwater confining method. In the underwater confining method, the precast concrete panel 46 is assembled on the footing 22 so as to surround the periphery of the pier 20, and the precast concrete panel 46 is submerged in the underwater 50. Turn into. In this construction method, the confining (restraint) effect is strengthened by tensioning a plurality of strip reinforcing bars (PC steel materials) inserted in the precast concrete panel 46 in the horizontal direction.
[0004]
FIG. 5 is a schematic cross-sectional view of the pier 20 during the construction of the above construction method. In the gap 44 between the pier 20 and the precast concrete panel 46, a plurality of axial reinforcing bars, that is, shaft reinforcing bars 42, are installed in order to increase the bending strength of the pier. As a construction procedure, these shaft reinforcing bars 42 need to be anchored to the existing footing prior to the assembly of the precast concrete panel 46.
[0005]
FIG. 6 is a schematic cross-sectional view in the axial direction of the fixing portion of the shaft reinforcing bar 42 to the footing 22. In the construction, first, the fixing hole 10 of the shaft reinforcing bar 42 is drilled in the footing 22. Conventionally, this drilling has been performed exclusively by a core boring technique using a diamond core drill. After the drilling, the shaft rebar 42 is inserted and fixed with a fixing material (a kind of adhesive). In the case of the pier 20 erected from the water, this is an underwater work. Thereafter, the precast concrete panel 46 is assembled and set around the pier 20, and the earth and sand and water in the gap 44 are discharged and filled with concrete.
[0006]
[Problems to be solved by the invention]
As described above, since the drilling of the fixing hole 10 of the shaft reinforcing bar 42 is performed in water, there are various problems. First, normally there is an existing reinforcing bar inside the footing 22, but it is necessary to search the location of the existing reinforcing bar prior to drilling the fixing hole 10. This is because the shaft reinforcing bars 42 must be arranged avoiding these existing reinforcing bars. However, there are few construction results of rebar exploration in water, and sufficient technologies such as selection of exploration machines, waterproofing methods for sensors, and exploration accuracy have not yet been established.
[0007]
Secondly, when core boring with a diamond core drill is performed based on insufficient exploration, if there is an existing reinforcing bar at that location, the existing reinforcing bar is easily cut. Therefore, when it is impossible to use a non-destructive reinforcing bar survey machine for existing reinforcing bars, drilling by core boring cannot be performed.
[0008]
Thirdly, in the drilling by core boring, since the hole wall is smooth and there are few irregularities, there is a problem that the pulling strength is insufficient when the shaft reinforcing bar is inserted and fixed with the fixing material.
[0009]
In view of the above problems, an object of the present invention is to provide a method for firmly fixing an axial reinforcing bar for reinforcement by reliably avoiding an existing reinforcing bar in an underwater confining method, and in particular, a drilling method for avoiding an existing reinforcing bar. And
[0010]
[Means for Solving the Problems]
(1) The shaft reinforcing bar fixing method in the underwater confined construction method for reinforcing an existing underwater structure according to the present invention includes at least the following steps.
(a) Fixation for shaft reinforcing bars to the target location of the existing building under the condition that the concrete can be drilled and the reinforcing bars cannot be cut using jetting of abrasive slurry containing water and abrasive The process of drilling holes
(b) A step of inserting a shaft rebar into the fixing hole and fixing with a fixing material
In the step (a) of drilling, irregularities are formed on the hole wall surface of the fixing hole by the jet injection.
[0011]
(2) In the shaft reinforcing bar fixing method of (1) above, preferably, (a) prior to the step of drilling the shaft reinforcing bar fixing hole in the target location of the existing building, (c) The method further includes a step of acquiring in advance drilling test data for determination.
[0012]
(3) In the shaft reinforcing bar fixing method according to (1) or (2), it is preferable that the conditions include at least the jet pressure of the jet injection and the number of rotations of the jet nozzle.
[0013]
(4) In the shaft reinforcing bar fixing method according to any one of (1) to (3), more preferably, the shaft reinforcing bar is an epoxy resin-coated reinforcing bar, and the fixing material is an epoxy resin adhesive.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic arrangement configuration diagram at the time of construction using the shaft reinforcing bar fixing method in the underwater confining method according to the present invention. The present invention is characterized in that drilling is performed using a high-pressure fluid injection by a high-pressure pump, so-called water jet technology. In particular, a direct pressurizing abrasive jet technique in which a slurry in which an abrasive and water are mixed is pressurized and injected by a high-pressure pump is used. As shown in FIG. 1, water from the water tank 32 and abrasive from the abrasive tank 33 are mixed by a mixer 34 to form an abrasive slurry, and this abrasive slurry is sent to the high-pressure slurry pump 35. The high-pressure slurry pump 35 sends high-pressure abrasive slurry through the hole tube rod 31 to the jet nozzle 30 provided at the tip thereof. Then, the abrasive slurry is directly jetted from the jet nozzle 30.
[0015]
The hole tube rod 31 is supported by a drilling machine (not shown) and driven to move forward and backward and rotate. As a result, the jet nozzle 30 can move forward and backward and rotate. In the present invention, since underwater drilling is performed, high-pressure air is sent to the jet nozzle 30 by the air compressor 36 and injected together with the abrasive slurry in order to increase drilling efficiency. Therefore, in this case, the hole tube rod 31 is a two-hole tube rod having an abrasive slurry passage and a high-pressure air passage. The method according to the present invention can be carried out by an abrasive slurry jet system including each of these devices.
[0016]
High-pressure injection of the abrasive slurry can form a jet having a large processing capability even at a relatively low pressure. It has a wide range of application by controlling the pressure. For example, it is possible from surface treatment of structures such as peeling and cleaning to remodeling and dismantling processing of structural parts such as cutting and drilling, and is also suitable for concrete drilling.
[0017]
FIG. 2 is a flowchart schematically showing an execution flow of the shaft reinforcing bar fixing method in the underwater confining method according to the present invention.
[0018]
Step 101: First, it is determined whether or not it is possible to search for existing reinforcing bars in the water of existing piers to be constructed. Judgment is made by conducting an underwater exploration test of the internal reinforcement of the pier underwater.
[0019]
Step 102: As mentioned above, reliable rebar exploration in water is almost impossible. Therefore, in this case, drilling by core boring is not possible. Therefore, in the present invention, an abrasive slurry jet drilling test is performed prior to actual construction on the construction target pier. FIG. 3 is a schematic configuration diagram showing an abrasive slurry jet drilling test method according to the present invention. First, the specimen 60 is prepared. The specimen 60 is preferably made of concrete and concrete under the same conditions as an existing structure such as a pier footing to be constructed. A test reinforcing bar 63 is disposed inside the specimen 60. It is also preferable that the test reinforcing bars 63 have the same conditions as the existing reinforcing bars in the existing structure to be constructed. Further, test water 62 is stretched in the water storage wall 61 on the upper surface of the specimen 60. A drilling test is performed on the upper surface covered with the test water 62 using an abrasive slurry jet system used in actual construction. That is, various data are collected by jetting abrasive slurry from the jet nozzle 30 at the tip of the hole tube rod 31 to drill the specimen 60.
[0020]
The main data to be acquired in the drilling test is as follows.
(1) Relationship between jet pressure and jet nozzle rotation speed when drilling only concrete, hole diameter and time.
(2) Relationship between the cutting time and the jet pressure and jet nozzle rotation speed when cutting reinforcing bars.
(3) Water contamination status during drilling (visual confirmation).
(4) The state of the wall surface of the drilled concrete.
(5) Pull-out strength of rebar fixed by fixing material after drilling.
Among the above, at least (1) and (2) are essential data for determining conditions for drilling only concrete without cutting the rebar by jetting the abrasive slurry. The applicability of abrasive slurry jet injection can be confirmed from these drilling test data.
[0021]
The drilling test performed prior to the actual construction does not necessarily need to be performed every time for the construction of all existing structures. If the already obtained drilling test data can be applied as is, the existing drilling test data should be used. You may divert. For example, this is a case where each of a plurality of existing structures is constructed under substantially the same conditions.
[0022]
Step 103: After obtaining data in the drilling test in step 102, the construction by the underwater confined construction method is actually performed. That is, the fixing hole for the shaft reinforcing bar is drilled in the target portion of the existing structure such as the pier footing by the abrasive slurry jet. At this time, based on the drilling test data acquired in advance, conditions for making only the concrete drillable and preventing the reinforcing bar cut are determined. Such conditions (usually having a certain allowable range) include, for example, jet pressure and jet nozzle rotation speed, or at least one of these. If drilling is performed under such conditions, even if it hits an existing reinforcing bar in the middle of drilling, the reinforcing bar will not be cut, and it will be impossible to drill (the jet nozzle cannot advance). It is possible to sense that there is a reinforcing bar at the position. If it hits an existing reinforcing bar, drill it in another location avoiding that position. After drilling, the shaft rebar is inserted into the fixing hole and fixed with the fixing material. In a preferred example, when an underwater curing type epoxy resin adhesive was used as the fixing material and an epoxy resin-coated reinforcing bar was used as the axial reinforcing bar, the adhesion between the fixing material and the reinforcing bar was good. Compared with drilling by core boring, the wall surface of the fixing hole drilled by the abrasive slurry jet injection of the present invention is not smooth and has moderate irregularities, so the pulling strength after fixing the shaft rebar is large. .
[0023]
Step 104: If it is determined in step 101 that the existing reinforcing bars in the water of the existing pier to be constructed can be searched, the conventional core boring can be performed. However, even when the existing reinforcing bar search is possible, the method according to the present invention can provide a strong fixing force of the shaft reinforcing bar, so that the method according to the present invention may be performed.
[0024]
【The invention's effect】
The shaft reinforcing bar fixing method in the underwater confined construction method according to the present invention is a drilling test data including conditions (jet pressure and jet nozzle rotation speed) that allow only the concrete to be drilled and cannot cut the reinforcing bar in the abrasive slurry jet injection. Then, based on the drilling test data, a fixing hole is drilled at a target location of an existing building such as a bridge pier footing under the condition that only the concrete is drilled and the reinforcing bar is not cut. Thereby, even if it hits an existing reinforcing bar, the presence of the existing reinforcing bar can be sensed by making it impossible to drill a hole by hitting the existing reinforcing bar without cutting the reinforcing bar. Therefore, the reinforcing shaft reinforcing bars can be arranged and fixed in a place where there is no existing reinforcing bars without damaging the existing reinforcing bars.
[0025]
In addition, drilling with abrasive slurry jets creates moderate irregularities on the hole wall, resulting in a strong adhesion between the fixing material and the hole wall, which improves the pull-out strength of the shaft reinforcement. To do. Furthermore, when the epoxy resin coated reinforcing bar and the epoxy resin-based fixing material are used, the strongest pulling strength is realized.
[0026]
The present invention solves various problems in the shaft rebar fixing process, which is one step of the underwater confined construction method. However, since the shaft rebar is firmly fixed as described above, the underwater confined construction method is realized. It is a method that greatly contributes to the overall effect, that is, to strengthening the earthquake resistance of underwater buildings.
[Brief description of the drawings]
FIG. 1 is a schematic arrangement configuration diagram at the time of construction using a shaft reinforcing bar fixing method in an underwater confinement method according to the present invention.
FIG. 2 is a flowchart schematically showing an execution flow of a shaft reinforcing bar fixing method in an underwater confinement method according to the present invention.
FIG. 3 is a schematic configuration diagram showing an abrasive slurry jet drilling test method in the present invention.
FIG. 4 is a schematic side view of a pier after construction by a conventional typical underwater confining method.
FIG. 5 is a schematic cross-sectional view during construction of the pier shown in FIG.
6 is a schematic cross-sectional view in the axial direction of a fixing part to the shaft reinforcing bar footing shown in FIG.
[Explanation of symbols]
10 shaft rebar fixing hole 20 bridge pier 22 footing 30 jet nozzle 31 two-hole pipe rod 32 water tank 33 abrasive material tank 34 mixer 35 high pressure slurry pump 36 air compressor 40 existing rebar 42 axial reinforcing bar 44 concrete filling space 46 precast panel 50 water 60 Specimen 61 Reservoir 62 Test Water 63 Test Rebar

Claims (4)

In the shaft rebar fixing method in the underwater confined construction method that reinforces existing underwater buildings, jetting of abrasive slurry containing water and abrasives is used to make concrete drillable and rebars uncuttable wherein possess the steps of drilling a fixing hole for shaft reinforcement against target portion of the existing buildings, and fixing by the fixing member and inserting the shaft reinforcement into the fixing hole Te, in the step of the boring A shaft reinforcing bar fixing method in an underwater confining method, wherein unevenness is formed on a hole wall surface of the fixing hole by the jet injection . The method further comprises a step of acquiring in advance drilling test data for determining the condition prior to the step of drilling a fixing hole for a shaft reinforcing bar with respect to a target location of the existing building. The shaft reinforcing bar fixing method in the underwater confined construction method according to 1. The shaft reinforcing bar fixing method in the underwater confined construction method according to claim 1, wherein the conditions include at least a jet pressure of the jet injection and a jet nozzle rotational speed. The shaft reinforcing bar fixing method in the underwater confined method according to any one of claims 1 to 3, wherein the shaft reinforcing bar is an epoxy resin-coated reinforcing bar and the fixing material is an epoxy resin adhesive.

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