JPS5826122A - Settlement of open caisson - Google Patents

Abstract

PURPOSE:To prevent the occurrence of accident due to the contact of a bit with a caisson when using the conventional expanded diameter bit by removing soil and sand at the cutting edge portion of the caisson being settled by means of a jet nozzle provided on the periphery of the excavating bit. CONSTITUTION:A counter weight 6 is first placed on an open caisson well 5 erected on the ground where a caisson is to be settled, a rotary table 3 is provided at the center of the counter table 6, and a rotary rod 1 hung down from a crane, etc., is rotatably set. While injecting excavation water 7 from a water supply pipe 8 into the open caisson well 5, the rotary table 3 is turned to excavate almost all area inside the well 5. Then, soil and sand in the cutting edge 5a portion of the caisson are broken and excavated by high-pressure water jetted from the jet nozzles 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for lowering an open caisson.

This type of open caisson is constructed using a construction method in which the inside of the cylindrical frame is excavated underwater with a bit, allowed to sink, and then concrete is poured at the bottom to form the foundation.The machinery and equipment are simple and the excavation cost is low. It is one of the widely used construction methods because it requires low friction and allows deep excavation.

Therefore, unless the earth and sand at the mouth of the caisson well is removed by some method, it will create resistance and the caisson will not sink, so conventionally the diameter of the bit was expanded.

However, the above-mentioned conventional method has the disadvantage that the bit bites the caisson well during diameter-expanding excavation, damaging the bit and the caisson well.

Therefore, the present invention uses a bit that is compatible with the inner diameter of the caisson well to excavate and remove earth and sand for the inner diameter of the well using a reverse method, and also uses high-pressure water from an injection nozzle installed on the outer periphery of the bit to remove the soil from the thick wall of the blade. The object of the present invention is to provide a method for sinking an open caisson in which the caisson is sunk by destroying and excavating earth and sand and discharging the soil.

An embodiment of the present invention will be described below with reference to the drawings.

First, to explain the names and functions of each part of the □ device used in the method of the present invention, reference numeral 1 is a hollow rotating rod with a bit 2 attached to its tip, and a suction pump or the like is connected to the other end (not shown) for use in a crane. etc., and is rotated together with the sibbit 2 by the rotary table 3. Reference numeral 4 designates a stabilizer attached to the rotating rod 1.

Reference numeral 5 designates a cylindrical open caisson well made of concrete or PC, which forms a cutting edge 5a whose inner circumferential surface is inclined outward so that the tip becomes gradually thinner.

A counterweight 6 is stacked on the upper end of the open caisson well 5, and although not shown, the counterweight 6 is further equipped with a stack of weights, gloss, etc., and uses the reaction force caused by its traction. This is to sink the open caisson well 5.

In addition, a water supply pipe 8 (not shown) communicates with an external water supply source for injecting excavation water 7 into the open caisson well 5.
is provided.

In this case, the outside diameters of the bit 2 and the stabilizer 4 are each formed so that they are only slightly smaller than the inside diameter of the open caisson well 5.

Furthermore, two high pressure water supply pipes 9, 9 are installed along the rotating rod 1.
The high-pressure water supply pipe is bent left and right at the toe end of the bit 2 and attached thereto, and an injection nozzle 10, 10 is connected to each tip in a slightly downwardly inclined manner. Note that the number of injection nozzles is not limited to two, and one or more may be provided, and at the other end of the high-pressure water supply pipe 10.10, a high-pressure turbine pump or the like for pumping water is installed, although not shown. It is connected.

Next, a case where a foundation is constructed by burying an open caisson underground using the above-mentioned device will be explained.

First, a counterweight 6 is placed on an open caisson well 5 erected on the construction ground, a rotary table 3 is provided at the center of the counterweight 6, and a rotary rod 1 suspended by a crane or the like is rotatably attached. Then, while injecting drilling water 7 from the water supply pipe 8 into the open caisson well 5, the rotary table 3 is rotated and the bit 2 at the tip is
At the same time, almost the entire inner diameter of the open caisson well 5 is excavated, and the earth and sand at the position of the cutting edge 5a is destroyed and excavated using high-pressure water injected from each injection nozzle 10.10.

The excavated earth and sand are pumped up and discharged from the tip of the bit 2 together with excavation water 7 via a rotating rod 1 which also serves as a reverse shovel. Therefore, the open caisson well 5, from which the earth and sand inside and at the cutting edge have been excavated and discharged, sinks into the ground under the weight of the counterweight 6, and can be lowered successively by similar excavations thereafter.

If necessary, a new well is stacked on top of the Oshin caisson well 5 that has been sunk in this way, and an open caisson well of a predetermined depth is constructed while carrying out the same excavation and removal. .

Then, the excavated water 7 can be discharged into the well after construction, and concrete can be poured to construct the foundation.

According to the method described above, since the bit 2 has a smaller diameter than the inner circumference of the open caisson well 5, the bit and the well come into contact with each other during excavation, resulting in damage to both, unlike conventional diameter-expanding bits. Excavation at the position of the cutting edge 5a can be carried out efficiently by jetting high-pressure water without causing any damage, and since the high-pressure water from the jet nozzle 10 stirs the excavated earth and sand, the excavated earth and sand can be discharged extremely easily. This is a method of sinking an open caisson that has the following effects:

[Brief explanation of drawings]

The drawing is a longitudinal sectional view showing an embodiment of the method for lowering an open caisson according to the present invention. [Explanation of symbols] l... Rotating rod 2... Bit 3... Rotary table 4... Stabilizer 5...
・Open caisson well 5a...Blade mouth 6...Counterweight 7...Drilling water 8...Water pipe
9... High pressure water supply pipe 10... Injection nozzle @ Ninbun Fleece Co., Ltd. Patent applicant NIT Co., Ltd. Patent applicant Mitsui Construction Co., Ltd.

Claims (1)

[Claims] Using a bit that matches the inside diameter of the caisson well, the earth and sand corresponding to the inside diameter of the well are excavated and removed using the reverse method, and the earth and sand in the thick part of the cutting edge are destroyed and excavated using high-pressure water from the injection nozzle installed on the outer periphery of the pit. A method for sinking an open caisson, which is characterized in that the caisson is lowered by lifting soil and discharging it using the same reverse construction method.