JPS6229611A - Ground amendment construction with widening device - Google Patents

Abstract

PURPOSE:To make the diameter of a widening hole remarkably larger than the diameter of a pilot hole, by fitting gradually lengthened stirring wings and nozzles at the wing ends of a wing bit containable in a device. CONSTITUTION:One of the wing sections of a wing bit 4 is contained in a device 1, and a pilot hole 12 is bored. Then, the wings of the bit 4 are opened, and water is jetted from the nozzles 11, 11' at the wing ends and the tip of the device 1, and at the same time the device 1 is hoisted and rotated to widen the bored hole. After the bored hole 14A is formed, stirring wings 18 are fitted on the bit 4, and the internal wall surface of the bored hole 14A is mechanically stirred with the stirring wings 18, and the secondary widened hole 15 of the stable wall surface is formed, and water is jetted to the widened hole 15 to form the secondary jet bored slot 15A. Then, by lengthening the stirring wings and the nozzles at the wing ends of the bit 4 gradually, the diameter of the widening hole is made larger than the diameter of the pilot hole 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a ground improvement method using a widening device, and particularly to a ground improvement method that can improve the width of the ground by a wider amount than the prescribed width of the widening device.

[Prior art]

BACKGROUND ART Conventionally, a deep mixing method has been known as a ground improvement method that mainly targets soft layers and improves the soft layers by mixing and solidifying the injected material. A widening device has been proposed that is used in this construction method and has a widening bit that can partially expand the improvement range of the soft layer.

The structure of this type of widening bit for ground improvement is shown in FIG. 4. The widening bit has a drilling support, and a rotary drive shaft 3 on which a wheel gear 2 is formed is provided at the lower end. This is the one with wing bit 4 attached. The wing bit 4 is formed into a flat plate shape, and has tapered side edges of both wings and a cutting blade 5 attached to the outer periphery.The wing bit 4 is used to attach the bus to the main body of the trenching device (hereinafter referred to as (referred to as the main body) 1, and the other buses are arranged to protrude downward from the tip of the main body 1 (imaginary line in Fig. 4). When widening the hole, the horizontal axis 3 is rotated to align the blade axis with the main body axis. solid lines in the same figure).

When a predetermined depth is reached, the hole is expanded and drilled. The wing bit 4 is operated by a gear mechanism built into the main body 1, including a rack par 6 that is movable in the axial direction at the center of the main body, a pinion gear 7 that meshes with the rack par 6, and a bevel gear mechanism 8 that rotates the wing bit 4 by rotation of the pinion gear 7. This is accomplished by a worm shaft 10 provided with a worm 9 that meshes with the wheel gear 2. In addition, in order to inject the ground improvement material after drilling, an improvement material discharge hole 11 is provided inside the main body 1, and is opened at the lower end of the main body 1.
It passes through the inside of the wing bit 4 and is also opened at its tip.

As shown in Figure 5 (1) to (5), the widening bit with such a configuration first drills a hole while pouring water to the improved ground (Figure 5 (1)), then rotates the widening device after drilling to a predetermined depth. While doing so, open the wing bit 4 underground ((2) in the same figure). After the blade opening is completed, the improved ground is expanded and the holes are pulled up and drilled (Figure 3).
), lower the widening bit to a predetermined depth, and while rotating the main body 1, inject the improving material from the discharge hole 11 and stir (see the same figure).
4)).

After the injection is completed, the wing bit 4 is closed and pulled up to complete the work. (Figure (5)).

[Problem that the invention seeks to solve]

However, with conventional width widening equipment equipped with wing bits, when performing continuous ground improvement such as impermeable walls, the widening range is limited to the length of the wing bit, making it difficult to construct continuous walls below existing buried structures. There was a problem that could not be done. In other words, when the width of the existing buried object is greater than the wing bit length, when pilot holes are drilled from the left and right sides of the buried object and widening holes are drilled at the bottom of the buried object, the widening holes do not communicate with each other. It separates at the bottom of the buried object.

The present invention focuses on the above-mentioned conventional problems, and the present invention makes the widening diameter by the wing bit larger than the wing bit rotating diameter, and provides a ground improvement method using a widening device that can significantly increase the widening ratio of the widening diameter to the pilot diameter. The purpose is to provide

[Means for solving problems]

In order to achieve the above object, the ground improvement method according to the present invention includes a rotatable wing bit provided at the tip of the trenching device main body, and after pilot drilling by the half-wing part of the wing bit, the wing bit is horizontally drilled. In the method of improving the ground by widening the hole by opening the wings in the direction, widening is further performed by installing a high-pressure nozzle at the wing tip of the wing bit to inject and discharge drilling fluid when widening the hole. At the same time, the length of the high-pressure nozzle is sequentially increased to add stirring again, thereby improving the width of a large diameter.

[Effect]

With the above configuration, after the pilot hole is drilled, the wing bit is opened to widen the hole. During this widening operation, drilling fluid is jetted out from the high-pressure nozzle installed at the tip of the wing to further widen the hole to the extent that the jet penetrates. Can be cut. Then, since the nozzle length is gradually increased and the width widening cutting is performed, the width widening amount can be increased in accordance with the increase in the nozzle length, and the width widening ratio can be increased.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the Example of the ground improvement method used for the widening device based on this invention is described in detail with reference to drawings.

FIGS. 1 (1) to (7) are cross-sectional views of the state of drilling work in each step of the soil improvement method of the embodiment.

A wing bit 4 similar to that shown in FIG. The pilot hole 12 is drilled to a predetermined depth while rotating and injecting water from the discharge hole 11 of the main body 1 with the other wing protruding from the lower end of the main body 1 (see Fig. 1 (1). )).

Next, after reaching a predetermined depth, the wing bit 4 is opened in the ground while continuing to rotate twice to bring it into a horizontal state ((2) in the same figure). The degree of opening of the wing bit 4 may be monitored by detecting the stroke amount of the hydraulic device that drives the rack par 6 (see FIG. 4).

After that, with the wings of the wing bit 4 opened, the discharge hole 1 opened at the tip of the wing bit 4 and the tip of the main body of the device.
While discharging water for drilling through 1.11', the drill is rotated while being pulled upward to widen the hole. At this time, the discharge hole 11 of the wing bit 4 is as shown in FIG. 2 (1).
As shown in FIG. 2, a high-pressure nozzle 13 is installed, and the jet flow from the nozzle 13 is used to further widen cutting underground from the inner wall surface of the widening hole 14 by the wing bit 4. Through this drilling operation, the widened hole 14 covering the closed blade range of the wing bit 4 and the cut hole 15 formed by the jet flow are formed at the same time. (Figure 1 (3)). As shown in FIG. 2 (1), the nozzle 13 is connected to the cutting edge 5 at the tip of the wing bit 4.
It is attached by being screwed into a recess 16 formed therebetween.

In this way, after drilling the rotary hole 14 of the wing bit 4 and the jet hole 14A using the nozzle 13, the wing bit 4 is closed and pulled up to the ground, and the nozzle 13 is removed from the tip of the wing bit 4. , a nozzle 13A longer than the nozzle 13 is attached. The length of this nozzle 13A is set to correspond to the jet cutting length in the previous step. As shown in FIG. 2(2), stirring blades 18 are attached to protect the nozzle 13A and stir the cutting fluid in the hole. As shown in FIGS. 2(2) and 3, the structure of the stirring blade 18 is such that, for example, angle irons 18B are attached to both sides of a rectangular cylinder 18A to reduce the resistance during horizontal rotation of the wing bit 4. A closed end plate 18G is located in the tip of the 6-cylindrical body 18A, whose base part clamps the wing tip of the wing bit 4 and is bolted together.
is attached, and a mounting hole 18D for the nozzle 13A is formed so that the tip of the nozzle 13A is exposed. Attach such a long nozzle 13A and stirring 3X18 to one end of the wing bit 4, and pass it through the pilot hole 12 again to the widened hole 14.
The wing bit 4 is inserted into the hole A, the wing bit 4 is closed, and at the same time as the hole is stirred, widening cutting is further performed by high-pressure jetting from the long nozzle 13A (FIG. 1 (4)). As a result, the inner wall surface of the jet cutting hole 14A in the previous step is removed by the stirring blade 1.
8 to mechanically stir the secondary widened hole 15A in the stable wall surface.
At the same time, jets are simultaneously made from the long nozzles 13A toward the inner wall surface of the secondary widened hole 15A to form a secondary jet cut hole 15A over the jet permeation range.

After that, pull up the wing bit 4 further and
), a longer nozzle 13B and a stirring blade 181
is attached to the wing tip of the wing bit 4, inserted into the secondary widening hole 15A, and the same widening operation is performed to form the tertiary widening hole 16 and the tertiary jet cutting hole 16A. (Figure 1 (5)).

Further, by repeating the same process, it is possible to widen the width even further.

If necessary, after the above widening work is completed, the long stirring blade 18
1 and the nozzle 13B, the stirring blade 182 finally reaches the inner wall surface of the tertiary jet cutting hole 16A cut by the jet.
At the same time, a discharge pipe (not shown) is attached in place of the nozzle, and solid material is filled and injected into the final widened hole 17 having a stable wall surface through this discharge pipe, while empty agitation is performed by the entire vertical and rotational movement. Add (1st @ (6)). After that, close the wing bit 4 and pull it upward (first
Figure (7)), the work is completed.

In this way, according to this embodiment, the diameter of the final widened hole is approximately 1.5 to 2 times the normal widened diameter without using the high pressure nozzle by making the stirring blade and the high pressure nozzle sequentially longer and drilling the widened hole. You can do up to.

Therefore, the widening ratio can be made much larger than in the past, and as a result, even if there is an existing buried structure, it is possible to construct a continuous water-shielding wall directly under it, perform ground improvement, etc. Moreover, since mechanical stirring is performed using stirring blades in multiple stages after cutting by jet flow, reliable ground improvement can be carried out with small torque. In addition, it is also possible to perform close-contact construction to sheet piles or continuous construction in place of wrapping.

〔Effect of the invention〕

As explained above, according to the present invention, an excellent effect is achieved in that widening holes with a large widening ratio can be reliably drilled with a small torque without causing loosening of the ground.

[Brief explanation of the drawing]

Figures 1 (1) to (7) are cross-sectional views showing each step of the soil improvement method of the example, and Figures 2 (1) to (3) are each nozzle mounting section with nozzles of different lengths installed. 3 is a front view of the stirring blade, 4 is a sectional view of the width expanding device, and 5 is a sectional view of the stirring blade.
1) to (5) are cross-sectional views showing each step of the conventional construction method. 1... Main body of the trenching device, 4... Wing bit, 4.
. Cutting blade, 11...Discharge hole, 12 Pilot hole, 13°1
3A, 13B... Nozzle, 14, 15, 16° 16B
... Widening hole, 14A, 15A, 17 ... Jet cutting hole, 18, 181, 182 ... Stirring blade.

Claims (1)

[Claims] (1) A rotatable wing bit is provided at the tip of the trenching device body, and after pilot drilling with the half-wing part of the wing bit, the wing bit is opened horizontally to widen the hole and drill the ground. In the improved method, when widening a hole, a high-pressure nozzle is installed at the wing tip of the wing bit to inject and discharge drilling fluid to perform further widening cutting, and the length of the high-pressure nozzle is sequentially lengthened. A ground improvement method using a widening device characterized by widening and improving large diameter areas by adding stirring.