JP2019007302A - Method of filling concrete inside steel pipe shaft for small cross section caisson bridge pier - Google Patents

Abstract

[Problem] To provide a method for filling concrete into the inside of a steel pipe shaft in a small-section caisson pier, which suppresses the thermal expansion of the steel pipe shaft and prevents cracks in the caisson pier. [Solution] A method for filling concrete into the inside of a steel pipe shaft in a small-section caisson pier, which is characterized by forming an insulating layer along the inner wall of the steel pipe shaft and filling concrete inside the insulating layer. [Selected drawing] Figure 1

Description

  The present invention relates to a method for filling concrete into a steel pipe shaft of a caisson pier constructed by a small-section caisson method.

In recent years, a method of performing mechanized excavation (slim caisson method) has been widely used in small cross-section caissons having small caisson cross-sectional dimensions.
As shown in FIG. 4, the small cross-section caisson has a pair lock in which a manlock for a person to enter and leave the excavation part and a material lock for carrying in and out materials and earth and sand are integrated. And with the pair shaft arrange | positioned at the upper part of a pair lock, those outlines are formed with the circular steel pipe shaft.

  When the caisson pier is constructed on the water surface by the small cross section caisson method, after the bottom of the bottom of the frame is built, the caisson pier is constructed up to the water surface, and then each equipment in the steel pipe shaft is carried out and the concrete inside the steel pipe shaft. The strength of the caisson pier is secured by filling and curing (FIG. 5).

When the concrete is filled into the steel pipe shaft and hardened, if the heat of hydration generated is large, the steel pipe shaft will thermally expand due to the heat of hydration.
The cross section of the caisson pier is rectangular. May occur (FIG. 6).
Fig. 7 shows the results of the three-dimensional FEM temperature stress analysis (cracking index) of the deformation of the caisson pier during concrete filling in a 1/4 model, where the concrete thickness is outside the steel pipe shaft. It can be seen that the crack index is small (the probability of occurrence of cracks is high). The 1/4 model shows caisson piers, but does not show steel pipe shafts or filled concrete.

  In view of the problems of the prior art as described above, the present invention provides a method for filling concrete inside a steel pipe shaft in a small-section caisson pier that suppresses thermal expansion of the steel pipe shaft and prevents cracking of the caisson pier. With the goal.

The invention of the present application made to solve the above problems is a method of filling concrete into a steel pipe shaft in a small-section caisson pier, wherein a heat insulating layer is formed along the inner wall of the steel pipe shaft, and the concrete is formed inside the heat insulating layer. It is characterized by filling. The heat insulation layer prevents the heat of hydration generated during the hardening of the concrete filled inside from being transmitted to the steel pipe shaft, thereby suppressing the thermal expansion of the steel pipe shaft and preventing cracking of the concrete outside the steel pipe shaft.
The heat insulating layer may be made of concrete. Since the concrete heat insulating layer is formed along the inner wall of the steel pipe shaft, the amount of concrete is small, so that the heat of hydration generated is reduced, the thermal expansion of the steel pipe shaft is small, and the concrete outside the steel pipe shaft is prevented from cracking.
The heat insulating layer may be formed of a heat insulating material. Since a heat insulating material is pasted to form a heat insulating layer, construction is easy.
The heat insulating layer may be an air layer, and concrete may be filled inside the air layer, and then the air layer may be filled with concrete. When the concrete is filled inside the air layer, the air layer becomes a heat insulating layer, and the heat of hydration can be prevented from being transmitted to the steel pipe shaft. Further, the amount of concrete to be filled in the air layer thereafter is small, so that the heat of hydration generated is small, the thermal expansion of the steel pipe shaft is small, and there is no cracking of the concrete outside the steel pipe shaft.

The present invention can obtain at least one of the following effects by means for solving the above-described problems.
(1) By forming a heat insulation layer along the inner wall of the steel pipe shaft, the heat of hydration generated when the concrete filled inside the heat insulation layer is hardened is prevented from being transmitted to the steel pipe shaft, and the thermal expansion of the steel pipe shaft is prevented. It can suppress and prevent the crack of the concrete outside a steel pipe shaft.
(2) The heat insulating layer is made of concrete, and the mold used at the time of forming the heat insulating layer is removed, so that only the concrete is filled into the steel pipe shaft.
(3) Since the heat insulating material is pasted to form a heat insulating layer, construction is easy.

Concrete filling method in steel pipe shaft inside small cross section caisson pier according to embodiment 1 of the present invention Concrete filling method for steel pipe shaft in small cross section caisson pier according to embodiment 2 of the present invention Method for filling concrete into steel pipe shaft in small cross section caisson pier according to embodiment 3 of the present invention Illustration of small section caisson Illustration of caisson pier constructed by small section caisson method Explanatory drawing of deformation due to thermal expansion of steel pipe shaft Explanatory drawing of the results of 3D FEM temperature stress analysis of deformation of caisson piers when filling concrete

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[1] Method of filling concrete in steel pipe shaft in small section caisson pier <1> Outline of the present invention The present invention is a method for filling concrete in the steel pipe shaft 2 in the caisson pier 1 constructed by the small section caisson method. (FIG. 1 (c)).
In the present invention, the filled concrete 3 is filled inside the heat insulating layer 4 in a state where the heat insulating layer 4 is formed along the inner wall of the steel pipe shaft 2.
The method will be described below.

<2> Arrangement of Formwork First, the formwork 5 is constructed at a predetermined distance from the inner wall of the steel pipe shaft 2 (FIG. 1A).
The formwork 5 may be a corrugated pipe, a steel formwork (metal foam), polystyrene foam, or the like, in addition to combining wooden plate materials.

<3> Formation of Heat Insulating Layer Next, concrete is filled between the inner wall of the steel pipe shaft 2 and the mold 5 to construct the heat insulating layer 4 (FIG. 1B).
Since the amount of concrete for constructing the heat insulating layer 4 is smaller than that in the case where the entire steel pipe shaft 2 is filled with concrete, the generated hydration heat is reduced, the thermal expansion of the steel pipe shaft 2 is also small, and the outside of the steel pipe shaft To prevent the caisson pier 1 from cracking.
When the heat insulating layer 4 is constructed, water may be injected into the mold 5. By injecting water, the temperature rise of the concrete filled in the heat insulating layer 4 can be suppressed.
The thickness of the heat insulation layer 4 should just be the thickness which can prevent the crack of the caisson pier 1 outside a steel pipe shaft, and can be suitably set from the restrictions on workability or design.

<4> Placement of filled concrete After the concrete of the heat insulating layer 4 is hardened, the mold 5 is removed from the mold, and then the filled concrete 3 is placed inside the heat insulating layer 4 (FIG. 1C). When water is poured into the mold 5, it is drained before the filling concrete 3 is placed. If the mold 5 can be left behind, the filled concrete 3 may be placed directly inside without removing the mold.
Since the amount of the filling concrete 3 is smaller than that in the case where the entire steel pipe shaft 2 is filled with concrete, the heat of hydration generated is also small. And since the heat insulation layer 4 which consists of concrete exists between the filling concrete 3 and the steel pipe shaft 2, the thermal expansion of the steel pipe shaft 2 by the generated hydration heat becomes small, and the crack of the caisson pier 1 outside the steel pipe shaft is reduced. Can be prevented.
When the filled concrete 3 is hardened, the steel pipe shaft 2 is filled with concrete and hardened together with the concrete of the heat insulating layer 4. If the mold 5 is removed, the inside of the steel pipe shaft 2 is filled with only concrete.

<1> Formation of a heat insulating layer by a heat insulating material In this embodiment, a heat insulating material 41 is attached along the inner wall of the steel pipe shaft 2 to form a heat insulating layer (FIG. 2A).
As the heat insulating material 41, a foamed heat insulating material such as foamed polystyrene or a fiber heat insulating material such as glass wool is suitable. Styrofoam, glass wool, and the like are easy to process and lightweight, so that they are excellent in workability and workability and can easily form a heat insulating layer.
And the filling concrete 3 is laid inside the heat insulation layer formed with the heat insulating material 41 (FIG.2 (b)).
Since the amount of the filling concrete 3 is smaller than that in the case where the entire steel pipe shaft 2 is filled with concrete, the heat of hydration generated is also small. And since the heat insulation layer 4 which consists of the heat insulating material 41 exists between the filling concrete 3 and the steel pipe shaft 2, the thermal expansion of the steel pipe shaft 2 by the generated hydration heat becomes small, and the caisson pier 1 outside the steel pipe shaft. Can prevent cracking.

<1> Formation of a heat insulating layer by an air layer In this embodiment, a mold 5 made of a corrugated pipe, a steel mold (metal foam), or the like is disposed in the steel pipe shaft 2, and the mold 5 and the steel pipe shaft 2 The air layer between them is defined as a heat insulating layer 4 (FIG. 3A).
Then, the filled concrete 3 is placed inside the mold 5 (FIG. 3B).
Since the amount of the filling concrete 3 is smaller than that in the case where the entire steel pipe shaft 2 is filled with concrete, the heat of hydration generated is also small. And since the heat insulation layer 4 which is an air layer exists between the filling concrete 3 and the steel pipe shaft 2, the steel pipe shaft 2 does not thermally expand by the generated hydration heat, and the caisson pier outside the steel pipe shaft. 1 will not crack.
Finally, the mold 5 is removed from the mold, and then the filled concrete 3 is placed on the heat insulating layer 4 (FIG. 3C). When the formwork 5 can be left, the filled concrete 3 may be cast as it is without removing the mold.
Since the amount of the concrete 3 to be cast in the heat insulating layer 4 is smaller than that in the case where the entire steel pipe shaft 2 is filled with concrete, the generated hydration heat is reduced, and the thermal expansion of the steel pipe shaft 2 is small. The caisson pier 1 outside the shaft is not cracked.

1 Caisson pier 2 Steel pipe shaft 3 Filled concrete 4 Heat insulation layer 41 Heat insulation material 5 Formwork

Claims (4)

A method of filling concrete into a steel pipe shaft in a small section caisson pier,
Forming a heat insulating layer along the inner wall of the steel pipe shaft;
Concrete filling the steel pipe shaft inside the small-section caisson pier characterized by filling concrete inside the heat insulating layer. In the method of filling concrete into the steel pipe shaft in the small-section caisson pier according to claim 1,
The method for filling concrete into a steel pipe shaft in a small-section caisson pier, wherein the heat insulating layer is made of concrete. In the method of filling concrete into the steel pipe shaft in the small-section caisson pier according to claim 1,
The method for filling concrete inside a steel pipe shaft in a small-section caisson pier, wherein the heat insulating layer is made of a heat insulating material. In the method of filling concrete into the steel pipe shaft in the small-section caisson pier according to claim 1,
The heat insulating layer is an air layer;
A concrete filling method for filling a steel pipe shaft in a small-section caisson pier, comprising filling concrete inside the air layer and then filling the air layer with concrete.

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