JPS5843532B2 - Caisson sinking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for sinking a caisson which can be applied even to poor ground conditions.

In order to accurately install a caisson without tilting, it is necessary to sink it gradually and evenly, but uneven settlement may occur in soft and viscous ground or uneven ground, or trees buried in the ground, etc. If there are obstacles such as boulders, accurate sinking may not be possible and the caisson may tilt.

And once it tilts, it becomes difficult to correct it.

By the way, important structures constructed using caissons (for example, underground tanks, etc.) are required to stop sinking at a predetermined depth and not to tilt.

This invention was devised in view of the above circumstances, and will be explained below based on the illustrated embodiments.

The construction procedure begins by replacing the ground below the cutting edge 3 at the position where the caisson 2 is sunk with a sand pillar 1.

Note that instead of this sand column 1, a column of gravel (fine) may be used, and the same applies in the following description.

Possible methods for installing the sand pillar 1 include using the sand compaction method used for installing sand piles and sand drains, or in some cases, inserting sand or gravel after reverse drilling.

In addition, the sand pillars 1 are arranged according to the cross-sectional shape (cutting edge part) of the caisson 2, but it is desirable to arrange them as densely as possible because they aim to equalize the soil quality and bearing capacity of the ground. .

(The illustrated embodiment is a case in which the cross-sectional shape of the caisson is circular.

) Next, the caisson 2 is placed on a group of sand pillars arranged as described above, and the caisson 2 is sunk while repeating excavation inside the caisson 2 and excavation of the lower part of the cutting edge 3 of the sand pillar 1.

Incidentally, the excavation of the portion below the cutting edge 3 is carried out gradually by using a high-pressure water jet 4 or the like to prevent uneven settlement.

This invention has the above-mentioned configuration, and since the caisson is sunk in the ground that has been made uniform with sand or gravel columns in advance under its cutting edge, the caisson can be easily constructed even on soft or uneven ground without tilting.

Furthermore, even if there are obstacles in the ground, they can be removed when installing the sand pillars, so construction will not be hindered when the caisson is lowered.

In addition, the sand pillar section provides sufficient support through vibrations, etc., so the caisson can be gradually sunk, and excavation below the cutting edge is very easy as the sand can be washed out using water jets, etc. becomes.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view, and FIGS. 2 and 3 are longitudinal sectional views during construction. 1...sand pillar, 2...caisson, -tarjet. 3...Blade mouth, 4...Woo

Claims (1)

[Claims] 1. After equalizing the ground bearing capacity by replacing the ground under the caisson's cutting edge with sand or gravel columns, the ground inside the caisson and the sand or gravel column portion below the cutting edge are excavated and the caisson is sunk. A caisson sinking method that is characterized by: