JPH026888B2 - - Google Patents

Description

[Detailed description of the invention]

This invention provides underwater corrosion protection using concrete coating.
Regarding the reinforcement method, it is a method to prevent or repair corrosion that frequently occurs near the splash zone and tidal zone of steel plates that extend from above water to underwater, such as underwater steel pipe piles and steel sheet piles for seawalls, as well as to strengthen them. This is an innovative corrosion countermeasure that uses the newly developed underwater stud welding method and the newly developed method of placing concrete into underwater formwork. First, we will explain in detail the newly developed method for placing concrete into underwater formwork, and then we will explain embodiments of the present invention using both the above-mentioned placing method and stud welding method for steel pipe piles and steel sheet piles. Conventional underwater concrete construction methods include the tremie method, concrete pump method, open-bottom box method (bucket method), bagging method, KDT tremie method,
There are seven types: NUCS method and hydrovalve method. I don't think it's necessary to explain them in detail, but currently the most commonly used methods are the tremie method, the improved KDT tremie method, and the concrete pump method. Figure 1 shows the principle of the tremie method. In this way, while concrete C is deposited at the bottom of the water, the tip of the charging tube T is inserted into it to pour the concrete, so even with ordinary concrete, only the upper layer does not come into contact with water W, so it deteriorates due to cement diversion loss. There is no. The KDT tremie construction method made the charging pipe T shown in Figure 1 a shrinkable material that prevents water from entering, and the charging pipe T was made into a vertical pipe T' connected to the concrete pump P as shown in Figure 2. This is the concrete pump method. M in the figure indicates the formwork. Since the concrete pump construction method is the most widely used and this invention also uses a concrete pump, this concrete pump construction method will be considered as a prior art and its problems will be described. Figure 2 is a diagram using the concrete pump construction method in the most suitable location, where a steel vertical pipe T' is connected to the end of the hose H coming out of the pump truck, lowered below the water surface W, and then hooked onto the crane hook F. It is held in place by the In reality, the hose H is often directly lowered into the formwork, but in the example shown in Figure 2, there are no obstacles above the formwork M, so a long vertical pipe T' can be suspended. If the height of formwork M is tall as shown in Figure 1,
Similar to the charging pipe T in Figure 1, the poured concrete C
As the height increases, the vertical pipe T′ must be lifted. Otherwise, the lower end of the charging pipe T will be buried deep in the poured concrete C, making it difficult to pull it out after pouring, and it will also be difficult to pull it out unless the feed pressure is increased. When the feed pressure is increased, the reaction force causes the vertical pipe to
If the lower end of the vertical pipe is lowered again and buried in the poured concrete, the water that has entered the pipe will be removed from the concrete. If you push it inside, the causes of the defect will occur all at once. Also, because there are obstacles above the formwork M, as shown in Figures 6 and 11, the vertical pipe T' cannot be hung down.
There are many cases in which the hose H is bent and its tip hangs down to the bottom of the formwork, or the vertical pipe T' is used at an angle. As the pump pumps concrete, the hose swings around a lot, so divers have to restrain it, and the slanted vertical pipe T′ has to be held in place by hand.
Non-modern work must also be done. The method of placing concrete in an underwater form according to the present invention eliminates the above-mentioned problems by providing a concrete inlet and a shutter or valve at the bottom of the underwater form. Even if the formwork has a large opening into which a concrete feed pipe can be inserted, we abandon the conventional wisdom of inserting the feed pipe from there and add an inlet at the bottom of the form.
Connect the concrete feed pipe to this. Eliminates concerns about the feed pipe vibrating or rocking due to pump pressure.
If the feed pipe comes out due to the reaction force of the pump pressure, or if the vertical pipe
This also eliminates the fear of erroneously determining the pulling speed of T'. Next, the configuration and effects of the present invention will be explained with reference to the drawings. FIG. 3 is a diagram illustrating the principle of the method of placing concrete into underwater formwork according to the present invention. When constructing concrete structures with a relatively small horizontal cross-sectional area, such as piles and walls that protrude from the water above the water surface, concrete feed pipes or hoses H are installed in advance on the frame plate that is the bottom of the formwork M of the desired shape. An inlet 1 with a shutter or valve that can be connected is provided, a formwork M is assembled at a desired position underwater using this frame plate, a feed pipe connected to the concrete pump is connected to the inlet 1, and the shutter 1a or valve is connected. By opening it and press-fitting concrete C, the water in the formwork M is pushed up from the bottom, replacing it with concrete C, and all of it is discharged from the upper edge of the formwork M, filling the formwork M with concrete C. The shutter 1a of the introduction port 1 is closed or the feed pipe H is removed. Figure 4 shows that the poured concrete C in Figure 3 is the formwork M.
is satisfied, and not only the water in the formwork M but also the upper layer concrete whose cement content has been reduced due to water overflows from the upper edge of the formwork M. Conventionally, even if the concrete pump was powerful, it was not possible to use a sufficiently strong pressure due to the vibration of the feed pipe and the increase in reaction force as described above, but with this method, any strong feed pressure can be used. Therefore, even if the concrete inlet port 1 is provided at the deepest point of the formwork M, it is possible to press-fit the concrete C to the top of the formwork M using the full supply pressure of the pump. It was summer. Next, an embodiment of the present invention will be described with reference to FIG. 5 and subsequent figures. Figures 5 and 6 are explanatory diagrams of an embodiment in which the present invention is applied because the steel pipe pile 2 erected on the seabed has corroded to the extent that corrosion holes 3 are formed in the splash zone and tidal zone near the water surface W.
Only a portion of the concrete C covering, stud welded dowel 4, and reinforcing bars 5 are shown. The appearance with formwork M applied is shown in Figure 6. The outline of the present invention will be described with reference to FIGS. 5 and 6. The present invention is designed to protect the integrity of at least the splash zone and the entire tidal zone of the second grade steel plate of the steel pipe pile extending into the water from the superstructure 6 above the water surface W. Groups of dowels 4 are welded by underwater stud welding in various parts, and reinforcing bars 5 are placed in the above area by connecting the dowels, and the whole is surrounded by a concrete formwork M, and the upper edge of the formwork M and the above A booth is provided between the lower surface of the upper structure 6 and a shutter 8 or an inlet 1 with a valve is installed in advance on the outer surface of the bottom of the formwork M.
By connecting and fixing the feed pipe H leading to the concrete pump and press-fitting concrete, the water in the formwork M is pushed up from the bottom, replacing it with concrete C, and all of it is drained from the booth After the defective part of the surface layer is also overflowed, close the shutter 8 or the valve, remove the feed pipe H,
This is an underwater corrosion protection and reinforcement method using a concrete coating that is characterized by curing. According to the conventional method of pouring concrete into formwork, since there is a superstructure 6 (concrete slab) above formwork M, the outlet of the concrete feed pipe should be fixed to the upper edge of formwork M from the side. There is no other choice but to discharge the concrete and let it fall. However, since the formwork M contains water during assembly, the concrete will fall freely into the water. Even if the water and concrete are replaced, the quality of the concrete is extremely poor because the cement content of the concrete is washed away or reduced. In addition, the surrounding area will be contaminated by washed away cement.
Therefore, it is necessary to use submersible concrete, which is not only expensive but also has a tendency to stick inside the pump due to its strong viscosity, making the work extremely difficult. However, by applying this invention, ordinary concrete can be used, and the above difficulties have been eliminated. As shown in FIG. 6, according to the present invention, the upper edge of the mold M does not require an opening for introducing a hose, so that the upper edge of the mold M can be extended to the lower surface of the upper structure 6. If a narrow or local gap is provided between the lower surface of the superstructure 6 and water overflows, the concrete will fill the formwork M as shown in Figure 4, and the water and defective areas of the concrete surface will flow from between the upper ends. It will overflow, so all you have to do is close the gap afterwards. This also made it possible to connect corrosion-preventing and reinforcing concrete to the superstructure. The concrete used is regular concrete, and its composition is as follows:

[Table] The concrete pump truck used was a 4-ton concrete pump.Maximum discharge pressure: 127Kg/ ^cm2Maximum discharge volume: ^40m3 /H Delivery pipe diameter: 4 inches Same length: 6.5m (2 90° elbows) Working discharge pressure: Approx. 14Kg/cm ² (constant) Inlet pressure 0.75Kg/cm ² (1.5m below the water surface) Casting time 5 minutes 10 seconds (1/3 to 1/4 of conventional steel pipe pile outer diameter 300mm Formwork inner diameter 600mm Formwork Height: 4m Concrete specimen compressive strength test value σ ₂₆ = 236Kg/cm ^2The formwork M may be a disposable formwork held together with FRP resin plates, or a formwork made of steel plates that can be moved to another location. The assembling, fixing, and disassembling methods are all based on conventional techniques, so explanations will be omitted. FIG. 7 shows an example of the inlet 1 that plays an important role in this invention. In this example, a pair of flanges 7, 7 are provided between the short pipe 1a with the inlet 1 welded to the formwork M side and the tube opening 1b into which the concrete feed pipe is fitted, and the shutter plate 8 can be inserted and removed between them. ing. The flange 7 is shown in FIG. 9, and the shutter plate 8 is shown in FIG. The flanges 7, 7 are tightened with two upper and lower bolts 9, and the diver can simply tap the end of the shutter plate 8 with a hammer or the like to align or remove the shutter plate opening 8a with the inlet 1 on which the flange 7 is attached. It has a simple structure that can be folded and closed. However, it is not a shutter,
It goes without saying that a commercially available on-off valve may be attached to the outside of the inlet 1. The above is an application of the present invention to the steel pipe pile 2, but this invention can also be used to cover the corroded part of the wall surface where the steel sheet piles 10 for seawall are connected with concrete from the sea side as shown in Figures 11 and 12. The invention is preferred. If the wall continues horizontally for a long time, partition plates should be placed in places on the enclosure formwork M with the back to the sheet piles, so that concrete placement can be completed within the scheduled time, depending on the concrete capacity of one section and the capacity of the pump truck. Just separate them as appropriate. The introduction ports 1 may be provided at multiple locations and concrete may be press-fitted all at once. Other points are almost the same as in the case of concrete covering of steel pipe pile 2. The only changes are the shape, assembly, and fixing method of the formwork M, and since these are conventional techniques, their explanation will be omitted. Although the present invention has been described above with reference to a small number of embodiments, the present invention can be varied and applied in various ways using techniques known to those skilled in the art without changing the gist thereof. In addition to repairing corroded areas, it is also effective in preventing corrosion. If the inlet 1 in Fig. 6 is oriented diagonally downward, there is an advantage that the concrete will spread along the bottom of the form. In the case of the horizontal inlet 1, a diagonally downward guide plate may be provided at the outlet. 7th
The short pipe 1a in the figure is omitted, and the flange 7 is directly connected to the formwork M.
You can also put it on. The material and shape of the formwork does not matter. The horizontal cross-sectional area only needs to be such that the concrete press-fitted from the inlets can rise all at once after being spread over the bottom of the formwork, but it can be considerably improved by increasing the number of inlets and making improvements to their arrangement. , can also be applied to large formworks. Multiple sets of concrete pumps and feed pipes may be used at the same time. In principle, the concrete used is general purpose concrete, but if non-separable special underwater concrete is used, sound concrete quality can be obtained up to the top layer, and there is no need to remove the top layer as is the case with ordinary concrete. For the underwater stud welding method, it is preferable to use the welding gun previously developed by the present inventor, but the method is not limited thereto. Reinforcement bars are not always required vertically and horizontally; wire mesh may be used instead. This invention improves studs, which were conventionally used to simply connect the steel surface and concrete in bridges, etc.
This paved the way for the first use of dowels for corrosion prevention and reinforcement of underwater steel plates with concrete. Since the underwater stud welding method is also used for dowel welding to the splash zone above the water surface, the welded part does not contain moisture and is highly reliable. By attaching reinforcing bars to the group of dowels and covering at least the entire splash zone and tidal zone, corroded areas are strongly protected and the corrosion-resistant and reinforcing effects of reinforced concrete are fully demonstrated. In addition, in the concrete placing method, there are unavoidable difficulties in the conventional underwater concrete method using a concrete pump, such as supporting the concrete placing vertical pipe T', lifting operation, vibration and oscillation caused by the pump, and important problems. According to the present invention, the problem of reaction force is solved at once because the tip of the feed pipe is connected and fixed to the inlet of the bottom plate of the form. According to this invention, the feed pressure of the concrete pump is not just used to send concrete overcoming piping resistance as in the past, but is also used to push the sent concrete up from the bottom of the formwork to the top. . In this case, since the pipe end is fixed, there is no risk of it moving due to press-in reaction force, making it possible to increase the pump's maximum pressure, and dramatically improving the casting speed.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of two examples of the conventional underwater concrete placing method, Figures 3 and 4 are illustrations of the principle of the underwater concrete placing method of the present invention, and Figure 5 is an illustration of the corroded steel pipe pile according to the present invention. Repair status diagram, No. 6
Figure 7 is an enlarged view of the concrete inlet at the bottom of the formwork, Figure 8 is its flange, Figure 9 is an illustration of its shutter plate, and Figure 10 is an explanatory view of the concrete inlet at the bottom of the formwork. Fig. 11 is an explanatory diagram of the state of repair of a corroded portion of a steel sheet pile of a revetment wall according to the present invention, and is an explanatory diagram of a state in which a formwork is applied to this. M... Formwork, H... Concrete feed pipe (hose), 1... Inlet with shutter or valve, 4...
... Jibel group, 5... Rebar.

Claims (1)

[Claims] 1 Steel pipe piles extending into the water from the superstructure above the water surface,
Groups of dowels are welded using the underwater stud welding method in healthy parts of steel sheets such as sheet piles, at least throughout the splash zone and tidal zone, and reinforcing bars are placed in the above areas by connecting the dowels, and concrete molding is performed. The whole is surrounded by a frame, a small gap is provided between the upper edge of the formwork and the lower surface of the superstructure, and a feed pipe connected to the concrete pump is connected to an inlet with a shutter or valve built in advance on the outer surface of the bottom of the formwork. By fixing the connection and press-fitting concrete, the water in the formwork is pushed up from the bottom, replacing it with concrete, and all of it is drained from the small gap above. After the defective parts of the concrete surface layer are also spilled out, An underwater corrosion protection and reinforcement method using concrete coating, which is characterized by closing the shutter or valve, removing the feed pipe, and curing it.