JPS62129420A - Reinforcing method for tank foundation ground - Google Patents

Abstract

PURPOSE:To reinforce foundation ground and to prevent liquidizing phenomenon from being generated during earthquake, by inserting a plurality of stiffeners into the foundation ground, to the lower section of a tank center from the outer peripheral section of the tank, and by fixing the on-ground side end sections of the respective stiffeners. CONSTITUTION:Boring is executed from the outer peripheral section of the filling 2 of a tank foundation, to the lower inclines section to the center of the tank, and stiffeners 3 are inserted into the bored slot, and after that, grout is injected. Near the end sections of the stiffeners 3, concrete is cast to form a concrete ring 5 on the outer periphery of the tank 4. By this method, the foundation ground of the tank is reinforced, and the liquidizing phenomenon of the ground can be prevented from being generated during earthquake.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for strengthening the foundation ground of a tank. This relates to a method for strengthening tanks and tank foundations to prevent destruction of tanks and tank foundations due to ground liquefaction during earthquakes.

[Conventional technology]

Petroleum tanks are generally built on ground that has been compacted to a certain extent through ground improvement, etc., and is filled with sand or crushed stones. In many cases, uneven settlement occurs due to consolidation settlement, causing problems in the tank's functionality and structure.

However, it is almost impossible to improve the ground of existing tanks by compacting them or replacing them afterwards, so it is desirable to strengthen the ground without moving the tanks.

In the past, various measures have been attempted to effectively reinforce the foundations of existing tanks. For example, in Japanese Patent Application Laid-Open No. 51-151815, multiple steel pipes were installed radially or A method of press-fitting them parallel to each other and horizontally to the tank bottom plate has been proposed.

[Problem that the invention seeks to solve]

Although the above-mentioned prior art is expected to have some effect of reinforcing the tank foundation in the relatively shallow portion, the ground below the tank foundation is not reinforced.

Therefore, it is useless to prevent the sudden and large-scale uneven settlement of the tank body caused by ground liquefaction during an earthquake up to a depth of 15 meters, such as that seen in the Niigata earthquake of 1963. it is conceivable that.

The present invention aims to prevent uneven subsidence that could lead to destruction of the tank body due to ground liquefaction during an earthquake.

[Means for Solving the Problems] In view of the above problems, the present inventors have proposed that by inserting rod-shaped reinforcing members diagonally into the foundation ground from the outer periphery of the tank toward the bottom of the center of the tank, the ground structure during an earthquake can be improved. We have developed a method that can keep the amount of uneven settlement due to liquefaction within an acceptable range and prevent tank destruction.

An outline of the present invention will be explained using FIG. 1 and FIG. 2 corresponding to an embodiment.

As shown in FIG. 1, the present invention inserts reinforcing material 3 in an oblique direction from the outer periphery of the embankment 2 of the tank foundation, so that the side of the ground around the tank side wall 4a, which is caused by ground liquefaction during an earthquake, is It is configured to prevent the tank 4 from flowing in the opposite direction, to minimize uneven settling of the main body of the tank 4, and to maintain a stable state.

The reinforcing material is, for example, by directly driving reinforcing bars or steel pipes, or by inserting the reinforcing material into a hole by boring and then mortar grouting, and has a diameter of 5011 to 120 a.
It is about m.

The cross-sectional shape of the reinforcing material is not limited to circular, square, etc., and the material is not limited to iron, but materials with high tensile and bending strength and corrosion resistance, such as glass or carbon fiber reinforcing material, can also be used.

The insertion angle θ of the reinforcing material with respect to the horizontal plane is 10 to 70 degrees, particularly preferably 30 to 50 degrees, and is appropriately selected depending on the soil quality of the foundation ground, the scale of the tank, workability, etc.

Note that if the insertion angle is too small or too large, the restraint effect by the reinforcing material, which will be described later, will be insufficient.

In addition, the reinforcing material must be long enough so that its tip can reach approximately the center of the tank foundation, and must be long enough to reach approximately the center of the tank foundation.
The length should be 0 to 1.5 times longer. FIG. 2 shows a state in which reinforcing materials 3 are radially arranged on the tank foundation ground 1 at a constant pitch a.

The pitch a of the reinforcing materials 3 is usually 1 to 2 m, although it depends on the scale of the tank 4 and the condition of the foundation ground 1, and the denser the pitch, the better.

The above-ground ends of each reinforcing member are fixed with concrete or the like so as to be integrated with each other to form a concrete ring 5.

[For production]

The reason why the method for strengthening the tank foundation ground of the present invention can prevent uneven settlement due to liquefaction of the ground during an earthquake is considered to be as follows.

The tank foundation ground 1 is subjected to a load due to the contents such as oil, and the stress in the ground is distributed such that the stress in the ground is maximum immediately below the center of the tank 4 and decreases toward the side wall 4a. For this reason, ground liquefaction occurs more easily on the side walls than in the center of the tank, and subsidence tends to concentrate on the side walls.

Therefore, by inserting a rod diagonally around the tank foundation ground to just below the tank and fixing the head, both ends of the reinforcing material are restrained (the area directly below the tank is in a relatively tight state due to the upper load). ), it forms a box-like shape in the ground as a whole, and can restrain the movement of the ground towards the tank surrounding area during liquefaction.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In the illustrated embodiment, a trench with a width of approximately 1 to 2 m is dug around the outer periphery of the embankment 2 laid under the bottom plate 4b of the existing tank 4, and diagonal boring is performed from this trench downward to the center of the tank 4. Form a drilled hole. Next, a reinforcing bar (for example, a steel bar of approximately D51) is inserted into this boring hole as a reinforcing material 3, and mortar is injected as a filler 6 into the gap between the bored hole and the reinforcing material 3 (see Figure 3). ). The length of the reinforcing material 3 is approximately the same as the radius of the tank 4 (approximately 1.5 times as long as necessary), and such reinforcing material 3 is installed at a distance of 1 to 2 m from the groove on the outer periphery of the tank 4. A box-shaped reinforcement work that narrows downward is formed in the foundation ground 1 below. After constructing the reinforcing members 3, concrete is poured into the groove to form a concrete ring 5, thereby fixing the heads (ends on the ground side) of each reinforcing member 3 in one direction.

Therefore, even if local liquefaction occurs near the tank side wall 4a during an earthquake, displacement is restrained, and uneven subsidence that could lead to the destruction of the tank 4 is prevented.

〔Effect of the invention〕

■ By constructing multiple rod-shaped reinforcing materials diagonally from the outer circumference of the tank toward the bottom of the center of the tank and integrally fixing the ends on the ground side, the tank foundation ground is restrained and works in one direction. In addition to simply increasing the support strength of the ground, it is also possible to suppress the amount of uneven settlement caused by ground liquefaction during an earthquake to within an allowable range.

■ It can be installed without disturbing the ground, and the reinforcing material is simply inserted diagonally, so it can be installed on existing tanks while the tank is in use without using fire.

■ It is economical because reinforcing materials are easily available and construction can be carried out in the same way as for general earth anchors.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of the inside of the ground showing the arrangement of reinforcing materials in the present invention, FIG. 2 is a cross-sectional view of the same, and FIG. 3 is a vertical cross-sectional view of essential parts in one embodiment. 1... Foundation ground, 2... Filling sand, 3...
...Reinforcement material, 4...Tank, 4a...
...Side wall, 4b...Bottom plate, 5...Concrete ring, 6...Filling material. Figure 1 Figure 2 Figure 3

Claims (5)

[Claims] (1) A large number of rod-shaped reinforcing materials are diagonally inserted into the foundation ground at required intervals from the outer periphery of the cylindrical tank toward the bottom of the center of the tank, and the ground-side ends of each of the reinforcing materials are integrated into one piece. A method for strengthening the foundation ground for a tank, characterized by fixing it to the ground. (2) The method for strengthening the tank foundation ground according to claim 1, wherein the above ground side end of each reinforcing member is integrally fixed with a cast-in-place concrete ring. (3) The method for strengthening a tank foundation ground according to claim 1 or 2, wherein the reinforcing material is a reinforcing bar or a steel pipe. (4) The insertion angle of the reinforcing material with respect to the horizontal plane is 10 to 70°
A method for strengthening a tank foundation ground according to claim 1, 2, or 3. (5) The method for strengthening the tank foundation ground according to claim 1, 2, 3, or 4, wherein the reinforcing material is inserted into the hole formed by boring, and the filler is injected into the gap. .