JP2002121732A - Method and device for improving soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stirring blade in a deep mixing device minimized in drive torque with hardly reducing the stirring effect and, particularly, a method and device for improving soil particularly suitable for the development of an improved pile of large diameter. SOLUTION: The sectional shape of the stirring blade vertically mounted in a plurality of stages on a hollow rod used for deep layer mixing method are formed so that the lateral lengths of both the upper and lower surfaces are varied to each other, and the stirring blade is mounted on the rod without an angle of attack to the rotating direction thereof. Accordingly, a turbulence of soft soil is generated in the rotating directional rear of the stirring blade when the blade is rotated, whereby the hardener discharged from the hollow rod is stirred and mixed with the soft soil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an apparatus used in a deep mixing method, which is one of the methods for improving soft ground, and a ground improvement method using the same.

[0002]

2. Description of the Related Art In a deep mixing method, a hollow rod rotatable in a circumferential direction is provided with a drilling blade at a tip thereof, and a plurality of stages of stirring blades are mounted above the hollow rod. This is a method of improving the ground by discharging the ground hardening material and mixing it with the soft soil with stirring.

As shown in FIG. 4, a stirring blade 5 conventionally used in this method generally has a surface protruding from a hollow rod 1 at an obliquely downward angle as shown in FIG. This has a structure that enhances the effect of stirring and mixing the hardened material and the soft soil.

However, in this structure, the projected area of the stirring blade on the soft soil in the rotation direction of the stirring blade 5 becomes large and has an angle of attack, so that the stirring blade itself becomes a large resistor and the driving torque becomes large. Inevitably, a large rotary drive motor is required, and especially recently, the construction of a large-diameter improved pile is required.In this case, the conventional drive motor may cause the hollow rod to be unable to rotate. Often there was.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and proposes a stirring blade having a reduced driving torque without substantially reducing the stirring effect. An object of the present invention is to propose a deep mixing apparatus and a method suitable for forming an improved pile having a large diameter.

[0006]

Therefore, in the present invention, the agitating blade mounted on the rotating rod has its blade surface mounted horizontally, that is, without an angle of attack, to minimize the driving torque.
Moreover, the cross-sectional shape of the stirring blade is trapezoidal or arc-shaped,
By changing the length of the width direction (sides) of the lower surfaces to different lengths and changing the speed at which the soft soil on the upper side and the lower side of the blade pass by the width of the blade when the stirring blade is rotated. The turbulence of the soft soil is generated behind the stirring blade in the rotation direction to enhance the stirring effect. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall explanatory view showing an example of the apparatus of the present invention. Reference numeral 1 denotes a hollow rod which is rotated in a circumferential direction by a driving motor (not shown). An example is shown in which the rod 1 is configured as a set of two rods rotating in opposite directions to each other. A hardening material such as a cement slurry is pressed into the rod 1,
When the rod 1 penetrates into the soft ground, it is discharged from the lower end nozzle 2.

Reference numeral 3 denotes a tip excavation wing at the lower end of the rod 1, and 4 denotes an upper excavation wing for expanding the diameter. Excavation bits are fixed to both the excavation wings 3 and 4.

Reference numeral 5 denotes a plurality of (three in the figure) rods 1 vertically and perpendicularly to the outer peripheral surface of the rod 1 above the upper excavation wing 4.
The stirring blade 5 is attached and fixed to both sides of the stirring blade. The stirring blade 5 has a substantially trapezoidal cross section as shown in FIG. It is mounted so that it does not stick, so that the horizontal rotational torque in soft ground is minimized. In addition,
Such a stirring blade having a substantially trapezoidal cross section can be easily manufactured by, for example, chamfering the left and right shoulders of a narrow metal plate by cutting.

The cross-sectional shape of the stirring blade 5 is not limited to a substantially trapezoidal shape, but may be an arc shape as shown in FIG. 3 (camaboko shape). To the hollow rod 1 without an angle of attack.

In short, each agitating blade 5 has a cross-sectional shape in which the upper and lower surfaces thereof have different lengths in the width direction, and the blade surface may be attached to the rod 1 without an angle of attack with respect to the rotation direction. The cross-sectional shape of the stirring blade 5 may be an inverted trapezoid or an inverted arc shape (an inverted camboko type) obtained by turning the example of FIGS. 2 and 3 upside down.

By rotating the hollow rod 1 to which the stirring blade 5 is attached at the time of penetration or withdrawal, the soft soil above the stirring blade 5 and the soft soil below the stirring blade 5 pass by the width of the blade 5. Since the velocities are different, a turbulent flow of the soft soil is generated on the rear side in the rotation direction of the blade 5, thereby exhibiting the effect of stirring and mixing with the hardening material.

[0013]

According to the present invention as described above, each stirring blade is attached to the hollow rod without an angle of attack, so that the rotating torque can be reduced, and the cross-sectional shape of the stirring blade is equal to the width of the upper and lower surfaces of the blade. Since the length of the pile is changed, turbulence is generated behind the rotation direction, the stirring effect is sufficiently exhibited, and the conventional problems such as insufficient torque when building a large diameter improved pile are solved. Can be.

In the case of manufacturing an apparatus using a pair of hollow rods rotating in opposite directions as in the illustrated example, in the conventional apparatus, the blade surfaces of the stirring blades are moved in opposite directions according to the rotation direction of the rod. It was necessary to pay attention to the mounting angle because it was required to be installed obliquely downward.However, in the present invention, the stirring blades are mounted without the angle of attack, so that all the mounting methods may be the same. Manufacturing is also easy.

[Brief description of the drawings]

FIG. 1 is an explanatory front view showing an example of the device of the present invention.

FIG. 2 is a perspective view showing an example of the shape of each stirring blade used in the apparatus of the present invention.

FIG. 3 is a perspective view showing another example of the shape of each stirring blade used in the apparatus of the present invention.

FIG. 4 is an explanatory front view showing an example of a conventional device.

[Invention of sign]

 1-Hollow rod 2-Hardened material discharge nozzle 3-Tip excavation wing, 4-Upper excavation wing, 5-Stirring wing

Claims (3)

[Claims] 1. A stirring blade which is mounted in a plurality of stages vertically on a hollow rod used in a deep mixing treatment method, has a cross-sectional shape in which upper and lower surfaces have different lengths in the width direction, and moves the stirring blade with respect to its rotation direction. With no angle of attack
A soil improvement method comprising: mixing a hardening material discharged from a hollow rod with soft soil by generating a turbulent flow of soft soil behind the rotation direction of the blade when the stirring blade is rotated. . 2. A stirring blade which is mounted in a plurality of stages on a hollow rod used in a deep mixing treatment method, has a cross-sectional shape in which the lengths in the width direction of the upper and lower surfaces are different, and the stirring blade is moved with respect to its rotation direction. A ground improvement device characterized by being attached to the rod without an angle of attack. 3. The ground improvement device according to claim 2, wherein the cross-sectional shape of the stirring blade is substantially trapezoidal, circular arc-shaped (camaboko-shaped), or inverted upside down.