Method for removing dowel bars and tie bars
The method of cutting, drilling, and using a steel rod to remove dowel bars from concrete pavement addresses inefficiencies in existing methods, enabling quicker and more economical replacement of dowel bars.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- GAEART T K
- Filing Date
- 2020-11-24
- Publication Date
- 2026-06-25
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing methods for removing dowel and tie bars from concrete pavement are inefficient and costly, particularly due to the time-consuming nature of core drilling, which also leads to excessive grout usage when reinstalling new bars.
A method involving cutting concrete pavement along joints, drilling holes towards dowel bars, forming screw holes, and using a steel rod to pull out the bars through microcracks induced by grout loosening and air passage creation.
Facilitates easy and cost-effective removal of dowel bars, reducing time and material waste while allowing for efficient reinstallation of new bars.
Smart Images
Figure 0007880199000001 
Figure 0007880199000002 
Figure 0007880199000003
Abstract
Description
Technical Field
[0001] The present invention relates to a method for removing dowel bars and tie bars provided in concrete pavement.
Background Art
[0002] Pavement includes asphalt pavement and concrete pavement. When durability is required, such as in the pavement of airports, harbors, and intersections of roads, concrete pavement is used. Concrete pavement includes that made by in-situ concrete and that by laying concrete slabs. Concrete slabs can be manufactured in factories. From the viewpoints of rapid construction and quality maintenance, concrete slabs are advantageous. In-situ concrete can flexibly respond to site conditions.
[0003] In laying concrete slabs, adjacent concrete slabs are connected through joints. Also in in-situ concrete, joints are provided at regular intervals to relieve expansion and contraction due to temperature changes. That is, joints are essential in concrete pavement.
[0004] However, many defects in concrete pavement occur at joints. For example, due to external stresses such as those caused by the passage of heavy objects such as aircraft and vehicles, displacement and misalignment are likely to occur between adjacent concrete structures. As a result, steps are generated at the joints, leading to accidents caused by the steps or the risk of damage to the stepped parts due to the passage of aircraft and vehicles. Displacement and misalignment between concrete structures at the joints can also cause noise.
[0005] In contrast, a plurality of metal bars having a load transfer function are embedded at locations corresponding to joints (Patent Document 1). The metal bars at locations corresponding to transverse joints are called dowel bars (slip bars), and the metal bars at locations corresponding to longitudinal joints are called tie bars.
[0006] A dowel bar is generally a round steel bar, with one end fixed and the other end coated with asphalt or similar material, allowing it to slide. This allows it to follow the expansion and contraction of concrete.
[0007] Tie bars are generally made of deformed steel and are used to suppress the opening of joints. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Publication No. 2001-182008 [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] As mentioned above, concrete pavement is highly durable, but it can deteriorate in parts. If the deterioration is minor, it can be repaired, but if the deterioration is advanced, the deteriorated concrete pavement must be removed. Naturally, there is no need to remove sections that are not deteriorated, and they will continue to be used. Generally, the sections to be removed and the sections to be used are determined by the joints.
[0010] At this point, the dowel bars and tie bars become an obstacle and are cut. Half of the dowel bars and tie bars remain embedded in the existing concrete pavement. In this state, it is not possible to install new dowel bars or tie bars between the existing and newly constructed concrete pavement. Therefore, it is necessary to remove the remaining half of the dowel bars and tie bars in the existing concrete pavement.
[0011] Incidentally, while several methods have been proposed for installing dowel bars and tie bars, methods for removing them have not been given much consideration, and the reality is that people are still experimenting with different approaches.
[0012] For example, concrete pavement is cut along with the dowel bar at the joint, core drilling is performed at the cut surface, and the dowel bar is pulled out along with the core. However, core drilling of concrete is time-consuming and costly. Also, if the core diameter is large, the amount of grout injected becomes unnecessarily large when reusing the core hole to install a new dowel bar.
[0013] The present invention aims to solve the above problems and to provide a method for easily removing dowel bars. [Means for solving the problem]
[0014] The present invention, which solves the above problems, is a method for removing dowel bars from concrete pavement. The concrete pavement is cut along the joints, and holes are drilled from the pavement surface toward the dowel bars.
[0015] This releases the vacuum, making it easier for air passages to form around the dowel bar.
[0016] Preferably, in the above invention, the hole is drilled toward the end of the dowel bar.
[0017] This makes the aforementioned effect more likely to occur along the entire length of the dowel bar.
[0018] Preferably in the above invention, a tap is made on the cut end face of the dowel bar to form a screw hole, a steel rod is screwed into the screw hole, and the dowel bar is pulled out via the steel rod.
[0019] This causes some of the tensile force to be dispersed, resulting in the formation of microcracks around the dowel bar. As these microcracks grow, they become pathways for air.
[0020] Preferably in the above invention, the grout end surface around the cut end surface of the dowel bar is kneaded and loosened.
[0021] This makes micro-cracks more likely to occur.
[0022] The invention of the present application for solving the above problems is a method for removing dowel bars from concrete pavement. The dowel bars are embedded through sheath pipes. Cut the concrete pavement along the joint, and drill holes from the pavement surface towards the dowel bars.
[0023] This can also be applied to the method of removing dowel bars.
Effect of the Invention
[0024] According to the present invention, the dowel bar can be easily removed.
Brief Description of the Drawings
[0025] [Figure 1] Example of dowel bar installation (concrete floor slab) [Figure 2] Example of dowel bar installation (cast-in-place concrete) [Figure 3] Example of dowel bar removal (first half) [Figure 4] Example of dowel bar removal (second half) [Figure 5] Example of dowel bar removal (conventional method)
Modes for Carrying Out the Invention
[0026] ~Example of dowel bar installation~ The dowel bar is a metal bar embedded at a location corresponding to the joint and having a function of load transfer. Generally, it is round steel. One end of the dowel bar is fixed, and asphalt or the like is applied to the other end to make it slidable. Thus, the dowel bar follows the expansion and contraction of the concrete.
[0027] Figure 1 is an example of dowel bar installation on a concrete floor slab. The concrete floor slab 1 and the concrete floor slab 2 are connected through a joint.
[0028] The concrete slab 1 is provided with horizontal holes 11 from the side and vertical holes 12 and 13 from the top. The concrete slab 2 is provided with horizontal holes 21 from the side and vertical holes 22 from the top.
[0029] Horizontal holes 11 and 21 are connected via a joint. Vertical hole 12 is connected to the back of horizontal hole 11. Vertical hole 13 is connected to the center of horizontal hole 11. Vertical hole 22 is connected to the back of horizontal hole 21.
[0030] With the dowel bar 3 inserted into the horizontal hole 11 (dotted line in the diagram), concrete floor slabs 1 and 2 are laid. After the concrete floor slabs 1 and 2 are laid, air is supplied from the vertical hole 12 to move the dowel bar 3 to the horizontal hole 21 using air pressure. Once it is visually confirmed that the dowel bar 3 is in the correct position through the vertical holes 13 and 22, grout is injected from the vertical hole 12. Confirm that the grout has filled the vertical holes 13 and 22. This completes the installation of the dowel bar 3.
[0031] Figure 2 shows an example of dowel bar installation in cast-in-place concrete. Concrete structure 101 and concrete structure 102 are connected via a joint.
[0032] First, concrete is poured into the lower halves of concrete structures 101 and 102. After the dowel bar 3 is installed in the correct position, concrete is poured into the upper halves of concrete structures 101 and 102. This completes the installation of the dowel bar 3.
[0033] ~Example of Dowwell Bar Removal~ The removal method according to this embodiment is applicable to both dowel bars installed on concrete slabs and dowel bars installed on cast-in-place concrete. For the sake of explanation, the removal of a dowel bar 3 installed on a concrete slab (see Figure 1) will be described.
[0034] If concrete slab 2 deteriorates, concrete slab 2 will be removed. Concrete slab 1 will continue to be used. Half of the dowel bar 31 will remain on concrete slab 1.
[0035] Figure 3 shows an example of dowel bar removal (first half). First, the concrete pavement is cut along the joint. At this time, the dowel bar 3 is also divided into two halves: dowel bar half 31 and dowel bar half 32.
[0036] A hole is drilled from the location of the vertical hole 13 (grout-filled) in the concrete deck slab 1 towards the far end of the dowel bar half 31. A vertical hole 14 is formed. Since the location of the vertical hole 13 is filled with grout, its position can be easily identified.
[0037] Furthermore, a tap is made on the cut end face of the dowel bar half 31 to form a screw hole 36.
[0038] Figure 4 shows an example of dowel bar removal (second half). A steel rod is screwed into the screw hole 36. Furthermore, the grout end surface 37 around the cut end surface of the dowel bar half 31 may be chipped with a chipper or the like as appropriate.
[0039] Note that the vertical hole formation process 14, the steel rod threading process, and the grout end face loosening process 37 (as appropriate) can be performed in any order. Also, steel rod welding may be used instead of steel rod threading.
[0040] Furthermore, while the grout 37 end face kneading process can be performed as needed, this process makes microcracks (described later) more likely to occur.
[0041] A force of, for example, 20-25 tf is applied via a hydraulic jack through the steel rod, and the steel rod is pulled out in the axial direction.
[0042] In this case, the entire tensile force is not concentrated in the direction of the steel rod, but rather a portion is distributed in a direction perpendicular to the steel rod. In other words, the steel rod wobbles in a perpendicular direction. This causes the lever principle to come into play.
[0043] The repeated micro-movement of the dowel bar half 31 causes microcracks to form between the dowel bar half 31 and the grout surrounding it. These microcracks grow, and the cut end surface and the vertical hole 14 become connected through the microcracks. This creates a small air passage around the dowel bar half 31.
[0044] The dowel bar halves 31 are anchored within the grout due to the combined effect of the grout's adhesive force and the vacuum pressure. However, the creation of an air passage releases the vacuum. As a result, the dowel bar halves 31 can be removed with less pulling force compared to when the vertical holes 14 are not present.
[0045] ~Examples of concrete pavement replacement~ Using the space where the dowel bar half 31 was removed, a new horizontal hole 11 is created. A new vertical hole 12 is also created. The new dowel bar 3 is temporarily placed in the horizontal hole 11. After laying the new concrete floor slab 2, the dowel bar 3 is moved to the correct position (see Figure 1). Grout is injected through the vertical hole 12. This completes the installation of the dowel bar 3.
[0046] ~Effects~ Figure 5 shows an example of dowel bar removal using a conventional method. In the conventional method, a core drilling device is installed at the cut surface, core drilling is performed, and half of the dowel bar is pulled out along with the core. However, core drilling of concrete is time-consuming and costly.
[0047] In this embodiment, the vertical hole 14 formation process, the steel rod threading process, and the grout loosening process (as appropriate) are required, but compared to the core drilling process, it saves time and cost and allows for easy removal of the dowel bar 3.
[0048] Furthermore, the dowel bar half-section 31 has a smaller diameter compared to the core diameter, making it easy to reuse (install a new dowel bar).
[0049] ~Examples of Tie Bar Applications~ While dowel bars are made of round steel, tie bars are made of deformed steel, and therefore, in principle, the above method is presumably not very suitable for removing tie bars.
[0050] However, there are also cases where tie bars are embedded through a conduit. In this case, applying the above method may allow the entire conduit, or the grout inside the conduit, to be removed. The tie bar can then be easily removed. [Explanation of Symbols]
[0051] 1. Precast concrete slab 2. Precast concrete slab 3 Dowwell Bar 11 Horizontal hole 12. Vertical holes (grout filling) 13. Vertical holes (grout filling) 14 vertical holes 21 Horizontal hole 22. Vertical holes (grout filling) 31 Dowwell Bar Half 32 Dowwell Bar Half 36 screw holes 37 Grout end face 101 Concrete Structures 102 Concrete Structures
Claims
1. In a method for removing a straight dowel bar embedded in concrete pavement parallel to the pavement surface, The concrete pavement is cut along the joints, Drill a hole vertically downward from the pavement surface down to the circumferential surface of the dowel bar. The circumferential surface of the dowel bar corresponding to the drilling hole is exposed to the air. Tap the cut end face of the dowel bar to form a screw hole, A steel rod is screwed into the aforementioned screw hole, The dowel bar is withdrawn via the steel rod. How to remove a dowel bar.
2. Drill towards the end of the dowel bar. A method for removing a dowel bar according to claim 1.
3. A method for removing dowel bars in concrete pavement, The concrete pavement is cut along the joints and the deteriorated concrete pavement is removed. The remaining concrete pavement that has not been removed is drilled below the pavement surface down to the dowel bar surface. Attach a steel rod to the dowel bar in the concrete pavement that remains without being removed. Cracks form in the grout around the dowel bars in the concrete pavement that remains without being removed. The dowel bar is withdrawn via the steel rod. How to remove a dowel bar.
4. The grout end surface around the cut end surface of the dowel bar is kneaded and loosened. A method for removing a dowel bar according to any of claims 1 to 3.