JPS63176528A - Settling of caisson - Google Patents

Abstract

PURPOSE:To raise the durability of caisson by preventing the corrosion of skeleton as well as to reduce the weight of the caisson by a method in which an inside vertical steel and an outside vertical steel are assembled by skeletal materials to form an inner steel skeleton, and the periphery of the inner steel skeleton is covered with concrete. CONSTITUTION:A caisson A consists of inside vertical steels 1 vertically set at an interval inside and connected with horizontal materials 2, outside vertical steels 3 vertically set at an interval outside, and framing materials 4 to be assembled into a truss form between the steels 1 and 3. A thin steel plate 5 is joined with the inner surface of the steels 1 and a concrete outer wall 6 is formed on the outside of the steels 3. After the caisson A is assembled in a dry dock, the caisson A is provided with outfits on sea and towed to a settling site by a tug boat B. Water ballast 7 is injected between the plate 5 and the peripheral wall 6 to settle it down to the seabed. Concrete is placed into the caisson A under water to settle it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for sinking a caisson covered with concrete into a steel frame.

[Problem that the invention seeks to solve]

For example, two types of caissons are currently used to form the foundations of main towers of bridges: concrete caissons and steel shell caissons, but each has the following problems.

In other words, the former is heavy and has a deep draft, so it cannot be manufactured entirely on the dock, and therefore requires offshore construction in calm waters with great depth, and the water depth of the towing route may be quite large. is necessary.

On the other hand, the latter caisson has a steel plate on its outer circumferential surface, so it is susceptible to corrosion (this may extend to the internal framework and deteriorate the concrete of the main body).

Furthermore, the ribs provided on the inside to reinforce the steel plate make it difficult for the poured concrete to move around, making it easy to form cavities.

This invention was made based on the actual situation of conventional caissons, and it is an attempt to overcome the difficulties of conventional caisson by making the caisson a composite structure of steel and concrete construction, and to form a high quality caisson. It is something to do.

[Means for solving problems]

In the present invention, the basic framework is made of rope and the outer periphery is covered with concrete, thereby reducing the weight of the caisson and at the same time solving the problem of corrosion of the framework. This allows the caisson to have a shallow draft similar to steel-shelled caissons, reducing restrictions on offshore construction and towing, and improving durability.

A caisson is constructed by assembling frame members between the inner vertical stiffeners arranged vertically on the inner circumference and the outer vertical stiffeners on the outer circumference. A wall is formed and a thin steel plate is bonded to the inner peripheral surface of the inner vertical stiffener.

After this caisson is towed to a predetermined sinking site, water is injected between the concrete outer peripheral wall and the thin steel plate, and the caisson is lowered to the bottom by water ballast, and then submerged by pouring underwater concrete inside.

〔Example〕

The present invention will be explained below based on the drawings showing one embodiment.

This invention is a method of towing a caisson A having a composite structure of steel and concrete as shown in FIGS. 1-I and 1-II to a predetermined site and sinking it.

As shown in Fig. 1, the caisson A has an inner vertical auxiliary member 1 arranged vertically at intervals on the inside and connected by horizontal members 2, and an outer vertical member 1 arranged vertically at the same intervals on the outside. The basic framework is a stiffener 3 and a frame member 4 assembled in a truss shape between both stiffeners 1.3, and a thin steel plate 5 is joined to the inner circumferential surface of the inner vertical stiffener 1 to form an outer vertical stiffener. A concrete outer peripheral wall 6 is formed around the outer periphery of the material 3.

A lip 5a for reinforcing the thin steel plate 5 is provided on the outer peripheral side of the thin steel plate 5, if necessary, as shown in FIG.

The concrete outer peripheral wall 6 is a slip form.

It is constructed by pouring concrete using a large formwork such as a jump form, or by joining precast plates, and is formed to cover the outer peripheral surface of the caisson A as shown in the figure.

When constructing this concrete outer peripheral wall 6, the inner framework can be used as scaffolding or support, and temporary construction costs can be saved.

Figures 2-1 and II show some details of the longitudinal section and cross section of the concrete outer peripheral wall 6, respectively, and as shown here, the outer vertical stiffener 3 has the concrete outer peripheral wall 6.
By protruding the shear connector 3a for integration with the concrete outer peripheral wall 6 and forming the shape of the concrete outer peripheral wall 6 into an arch shape as shown in (2), it is possible to effectively resist water pressure, and bending stress is generated. can be suppressed, resulting in a structurally superior structure centered on compressive force.

Next, the construction procedure will be explained according to Fig. 3.

First, bottom plate a of caisson A in the dock.

Inner and outer vertical stiffeners 1, 3. Horizontal material 2. The basic frame is constructed by assembling the frame members 4 (I), and the caisson A is constructed by forming the concrete outer peripheral wall 6 and joining the thin steel plates 5 (II).

At this point, water is once poured into the dock and caisson A is pulled out to calm waters, and the remaining necessary construction work or sheathing is carried out (
I[[).

Then, caisson A is towed to a predetermined site by tugboat B (■), water ballast 7 is injected into caisson A, that is, between the thin steel plate 5 and the concrete outer peripheral wall 6, and caisson A sinks and lands on the bottom (V). .

Finally, underwater concrete 8 is poured into the caisson A to complete the caisson body (■), and the construction is completed.

FIG. 4 shows the completed state of the caisson main body, and an anchor frame C for mounting an upper structure is provided on the upper part of the caisson main body.

[Effects of the Invention] The present invention is as described above, and since the caisson has an outer peripheral wall made of concrete and an internal framework made of steel, the following effects can be obtained.

Like steel-shelled caissons, caissons are lightweight and have shallow drafts, so there are fewer restrictions on offshore construction and towing, making them economical.

Since the outer peripheral surface is covered with concrete, there is no problem of corrosion.

Since there are no ribs on the inside of the outer peripheral wall, when concrete is placed underwater, the concrete flows easily and there is no risk of creating cavities.

[Brief explanation of the drawing]

Figures 1-1 and II are longitudinal cross-sectional views and cross-sectional views, respectively, showing an example of the configuration of a part of the caisson, and Figures-2-I and I[ are longitudinal cross-sectional views, respectively, showing details of a part of the concrete outer peripheral wall. , a cross-sectional view, FIG. 3 is a schematic diagram showing the construction procedure, and FIG. 4 is an elevation view showing the caisson body. A-・-・Caisson, a-----・-Bottom plate, 1-・
-Inner vertical stiffener, 2, -------One horizontal stiffener, 3.-
・-・・・Outer vertical stiffener, 3a------1-tour connector, 4---------frame material, 5-----
・-Thin steel plate, 5 a----Rib, 6...
−・−Concrete peripheral wall, 7−・−・−Water ballast,
8-----Underwater concrete, B--------Tug boat, c----Anchor frame. 1 Figure I Figure 2 1 II Figure 4 Figure 8

Claims (1)

[Claims] (1) There is a framework between the inner vertical stiffeners, which are arranged vertically at intervals on the inside and connected by horizontal members, and the outer vertical stiffeners, which are arranged vertically at the same intervals on the outside. The caisson is constructed by assembling the materials, joining a thin steel plate to the inner circumferential surface of the inner vertical stiffener, and covering the outer circumference of the outer vertical stiffener with concrete to form a concrete outer wall. A method of sinking a caisson in which the caisson is towed to a certain point, water ballast is injected between the thin steel plate and the concrete outer wall, the caisson is lowered to the bottom, and then underwater concrete is placed inside the caisson to sink the caisson.