JPS5948254B2 - Method for reducing circumferential friction when sinking a caisson - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing circumferential friction during sinking of a caisson.

A caisson is a structure mainly made of reinforced concrete that has been built on the ground in advance, and is installed by digging out the soil at the bottom, sinking it to a specified stratum using its own weight or load, and pouring concrete at the bottom. In general, the conditions for a caisson to sink must satisfy the following equation.

Wc+Ww＞UfF 10Q Where, WC: Caisson body weight (1) WW: Sinking load applied when the caisson sinks (1) U: Buoyant force acting on the caisson body (1) F: Caisson peripheral frictional resistance force (1) Q : Caisson cutting edge resistance force (1) In order to safely and reliably sink the caisson to the supporting ground, it is necessary to reduce the tip resistance force of the caisson cutting edge, or to Either by reducing surface friction resistance or by reducing buoyancy (lowering the water level in the caisson by changing the water).

In general, loading a caisson with a load and changing water are relatively easy methods to increase the sinking edge of a caisson, but the former significantly reduces excavation efficiency, and the latter causes quick sanding and heaving, so it is not the preferred method. I can not say.

Therefore, it is very effective not only to make the outer wall surface of Kennison smooth and to make it sink as vertically as possible to reduce the frictional resistance, but also to forcefully reduce the frictional resistance. equipment and methods are used.

Traditionally used air supply type, water supply type, application type,
Methods such as sheet type and blasting methods do not always have sufficient effects.

For example, air supply type and water supply type are relatively effective on fine-grained soil such as clay or silt, but cannot be expected to be very effective on sandy soil.

In addition, the coating and sheet methods have the disadvantage that the membrane is destroyed when the caisson is damaged, and they are no longer effective, and the blasting method may cause damage to the structure.

As a result of intensive research aimed at eliminating the deficiencies of the prior art, the present inventor has come to provide an extremely excellent method for reducing friction on the caisson peripheral surface.

In other words, after injecting a slurry in which a superabsorbent resin is dispersed into a liquid into the outer wall of the caisson, pressurized water is injected onto the outer wall of the caisson into which the slurry has been injected, thereby reducing the frictional resistance on the circumferential surface of the caisson. We have found that it can be significantly reduced.

Furthermore, since the gel that absorbs water and swells is insoluble in water and stable, once it is injected, it acts as a lubricant for a long period of time, allowing stable deposition.

Incidentally, after the caisson has been deposited, the gel can be made to disappear by injecting an aqueous CaCl2 solution or the like.

The superabsorbent resin used in the present invention refers to one that absorbs water and swells from several hundred times to nearly 2,000 times, such as starch-acrylonitrile or starch-methacrylate graft copolymer partial hydrolyzate: poly Partial hydrolysates of acrylonitrile and vinyl ester-ethylenically unsaturated carboxylic acid copolymers: Olefinic polymers loaded with hydrophilic groups such as sulfonated styrene: Polyethylene oxide: Polyvinyl alcohol: Polyvinylpyrrolidone: Sodium polyacrylate: Polyacrylamide : Carboxymethyl cellulose: Polyacrylic acid, polyacrylamide copolymer, niblurane, etc., water-soluble polymer compounds irradiated with radiation, methylene bisacrylamide: dichloroacetic acid: epichlorhydrif: aldehydes, etc. Crosslinked products: Hydrophilic groups Copolymerization products of isobutylene and maleic anhydride v0: crosslinked polyacrylates in which some portions are substituted with lipophilic groups can be mentioned.

By the way, when a super absorbent resin is used as a lubricant, the smaller the water absorption amount (the state in which water absorption power still remains), the greater the water retention capacity and the greater the friction reduction effect.

However, if the amount of water absorbed is small, the apparent viscosity is large, making injection difficult.

Therefore, by dispersing the resin powder with a liquid to form a slurry, it becomes easier to transport it within the pipe and to inject it into the gap between the outer wall of the caisson and the ground.

After injecting this slurry, if pressurized water is injected, a layer of swelling gel will be formed on the outer wall surface, which will have an excellent friction reduction effect on any ground.

As a result, the caissons can be sunk safely and efficiently, making it possible to shorten the construction period and cut costs.

Figure 1 shows a cross section of the caisson when it is sunk, and a slurry injection port 2 and a pressure water injection port 3 are installed vertically in the caisson construction 1.

In other respects, there is no particular difference from the conventional caisson, so details will be omitted.

Now, when the caisson frame 1 has stopped sinking, in order to reduce the frictional resistance on the circumferential surface between the caisson frame 1 and the ground 4, a super absorbent resin is injected with oil from the injection port 2 onto the outer wall surface 5 of the caisson frame 1. The dispersed slurry is injected, and then pressurized water is injected from the injection port 3.

As the pressure water to be injected from the injection port 3, an aqueous dispersion of a super absorbent resin can be used.

In some cases, the injection port 2 and the injection port 3 may be made common,
At the same time, an aqueous dispersion of super absorbent resin can also be injected.

The slurry injected from the injection port 2 is diffused on the outer wall surface 5 by the jet of pressurized water, absorbs water and becomes an insoluble granular gel, and forms a gel layer '5 between the caisson frame 1 and the ground 4.

Therefore, the circumferential frictional force generated between the caisson frame 1 and the ground 4 is significantly reduced, and the sinking of the caisson can be promoted.

FIG. 2 shows an example of a slurry injection device.

The slurry is put into the injection container 6, the hose 8 is connected to the injection fork 2 shown in FIG.

As can be seen from the explanations above, the present invention has extremely excellent effects, and the points will be listed below.

(1) This method has a better friction reduction effect than conventional methods,
The effect can be maintained for a long time.

(2) It is effective under any ground conditions, and in particular, forms a layer of swelling gel even on sandy or gravelly ground, promoting the sinking of caissons.

(3) Super absorbent resin absorbs hundreds of times more water and swells, so it is economical because only a small amount of injection is required.

(4) After the sedimentation is completed, the gel can be eliminated by injecting an aqueous CaCl2 solution, which increases the stability of the basic structure.

(5) No special pump or injection device is required, and conventional air and water supply devices can be used as is.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cane construction in which the method of reducing peripheral surface friction during caisson sinking according to the present invention is implemented, and FIG. 2 is a side view showing an example of a slurry injection device used in the method of the present invention. 1... Caisson frame, 2... Slurry inlet, 3... Pressure water injection port, 4...
Ground, 5... Caisson frame outer surface, 6...
...Injection container, 7...Compressor, 8...
····hose.

Claims (1)

[Claims] 1. By injecting a slurry in which a superabsorbent resin is dispersed in a liquid onto the outer wall of the caisson, and spraying pressurized water onto the outer wall of the caisson into which the slurry has been injected, the friction on the circumferential surface of the caisson is reduced. A method for reducing circumferential friction during sinking of a caisson, characterized by promoting sinking of the caisson.