JPH1122356A - Shaft excavation casing - Google Patents

Abstract

(57) [Problem] To reinforce and use a thin casing in order to reduce the amount of steel material of a thick shaft casing. SOLUTION: The hollow is pressed from the outer surface of the casing to the inner side to reinforce the entire casing. The shape of the hollow is a hemispherical shape with a staggered distribution, a horizontal groove type with a partial circular cross section, a spiral groove type with a partial circular cross section, a left-right inclined spiral with a partial circular cross section There is a groove-shaped one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a circular casing driven by a shaft excavator of a civil engineering construction machine.

[0002]

2. Description of the Related Art As shown in FIG. 1, a shaft excavation using a circular casing is performed by gripping a circular casing 3 with a clamp band 7 by a swing press-fitting machine 2 of a shaft excavator 1 and applying a downward pressure to perform a small rotary reciprocating motion. Given to the circular casing 3,
It is performed by excavating the inside with a grab bucket attached to a shaft excavator while pushing it into the ground, and discharging the soil. A conventional circular casing has a shape as shown in FIG. 9, and a shaft having a diameter of 1 to 2 meters is made of a steel pipe having a wall thickness of 12 to 16 mm. A drilling blade 4 is attached to the tip of the casing. If it is necessary to add a casing, the next casing 13 is butted against the original casing 3 and welded.
Connected with. This casing serves as a part of the drilling equipment to transmit the rotational torque and press input from the shaft excavator to the excavation blade during the shaft excavation work, and is used as a temporary retaining soil after the completion of the shaft, and ultimately Be buried and killed.

[0003]

The burying of this casing as a temporary earth retaining material results in wasteful embedding of a large amount of steel material in the soil, resulting in construction costs, resource consumption, and the like. This is a problem that must be reconsidered from the perspective of the global environment. Therefore, the challenge is to develop a casing that minimizes the amount of steel material, withstands the required excavation resistance as a drilling rig, and withstands the earth pressure applied from the outer surface of the casing as a retaining structure, ensuring worker safety. is there.

[0004]

SUMMARY OF THE INVENTION In order to reduce the thickness of a conventional circular casing having a diameter of 1 to 2 meters from 12 to 16 mm to a thickness of 4.5 to 6 mm and to provide strength, As shown in FIG. 2, a recess 6 is formed by pressing from the outer surface of the steel pipe to the inside thereof so as to increase the strength of the casing. If the recess 6 is formed smoothly, the concentration of stress can be prevented, the inside can be passed without the grab bucket being caught by the recess 6, and the outer surface of the casing has no protrusion, so that the clamp band 7 can be used as shown in FIG. It can be used in any position of the casing as well as the conventional smooth casing 3 or 13. However, the size of the recess 6 must be less than half the width of the clamp band 7.

[0005]

FIG. 3 shows an example in which circular depressions 6 are arranged in a staggered pattern. FIG. 3 shows a part of the arrangement of the depressions 6, and other parts are omitted. It is necessary to determine the diameter and pitch of the circular recess 6 so that the unprocessed planes are not connected in a straight line. The cross section taken along the line AA in FIG. 3 is as shown in FIG. 7, and the second moment of area of this cross section is larger than a flat plate of the same thickness by two orders of magnitude or more, and the structure can withstand the earth pressure of the ground well. It is possible to do. B in FIG.
The section -B is as shown in FIG. 8, and the pole moment of inertia is reduced by several tens of percent in comparison with a smooth circular casing. The torsional strength due to the rotation torque increases. In addition, the cross-sectional area parallel to the force applied by the shaft excavator decreases, but the strength of the casing in the direction of the central axis is sufficiently strong compared to the strength against other external forces, and the press working As a result, the cylindrical surface is less likely to buckle, resulting in an increase in the compressive strength.

Referring to FIG. 3, a simple excavating blade 4 which is embedded and killed together with the casing 3 is attached to the lower end of the casing 3 by welding 5, so that excavation of the ground is facilitated and also used for reinforcing the casing end. When the shaft is deep, the casing 3 needs to be extended. However, the conventional casings 3 and 13 shown in FIG. 9 can be butt-connected because the wall thickness is large, but in the case of a thin casing as shown in FIG. Using the connecting ring 8, the next casing 13
And make a connection by fillet welding 5. The width of the connection ring is made as narrow as possible, and when the casing is gripped by the clamp band 7, it is clamped avoiding this part.

FIG. 4 shows the hollow 6 as a horizontal groove having a partially circular cross section. The AA cross section appears in the same shape as that of FIG. 7, and the second moment of area of this cross section is larger than that of the unpressed smooth casing, like the casing of FIG. Although the proof strength of such earth pressure is increased, the rigidity and proof strength against the axial thrust of the cylinder are significantly reduced. Further, the rigidity and the proof stress against the rotational torque become almost the same as in the case of FIG. Therefore, the present invention can be applied to excavation of soft silt or fine sandy ground which does not require much pressing force. The excavation blade 4 and the connection ring 8 are the same as those shown in FIG.

FIG. 5 shows the recess 6 having a partially circular cross section.
This is a case where a spiral groove is formed with respect to the center axis of the cylinder. When the angle of the helix is reduced, this groove becomes the same as that in FIG. 4, and the rigidity of the cylinder with respect to the radial pressure becomes maximum,
The stiffness to axial thrust is minimal. Increasing the helix angle also maximizes the axial stiffness of the cylinder, but instead minimizes the stiffness to radial pressure. Therefore, an angle at which the rigidity of thrust and torque is just right can be selected for the angle of the groove. The rigidity with respect to the rotational torque is slightly reduced as in the case of the staggered type shown in FIG. The digging blade 4 and the connection ring 8 are the same as in FIG. However, the portion where the connection ring 8 and the recess 6 intersect needs to be blinded by welding so that the casing is kept watertight.

FIG. 6 shows another example in which the casing shown in FIG. 5 is provided with another opposite spiral to prevent the rigidity and strength characteristics from being varied depending on the rotation direction. The rigidity of the ground against the pressure in the radial direction due to the earth pressure becomes larger than that in the case of FIG.
The stiffness of the rotational torque is almost the same or slightly reduced. Drilling blade 4
And the connection ring 8 are the same as in FIG.

[0010]

According to the present invention, the amount of steel used in the shaft shaft casing which is buried after being used as a temporary structure is reduced to less than half.

As the amount of steel decreases, material costs can be reduced, transportation costs can be reduced, and as a result, construction costs can be reduced.

[0012] The burden on the environment, which has recently been called noisy, is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram of an excavation operation performed by a shaft excavator.

FIG. 2 is a cross-sectional view showing a relative position between a casing and a clamp band reinforced by a recess.

FIG. 3 is a sectional view of a casing reinforced with a hemispherical recess.

FIG. 4 is a sectional view of a casing reinforced by a groove having a horizontal partial circular cross section.

FIG. 5 is a cross-sectional view of a casing reinforced with a spiral groove having a partial circular cross section.

FIG. 6 is a cross-sectional view of a casing reinforced with a spiral partial circular cross-section groove having left and right inclinations.

FIG. 7 is a sectional view taken along line AA of FIGS. 3 and 4;

FIG. 8 is a sectional view taken along line BB of FIG. 3;

FIG. 9 is a sectional view of a conventional circular casing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical shaft excavator 2 Oscillating press-fitting machine 3 Casing 4 Drilling blade 5 Welding 6 Recess 7 Clamp band 8 Connection ring 13 Next casing

Claims (5)

[Claims] 1. A circular shaft excavation casing in which a depression is pressed from an outer surface of a cylinder toward an inner surface and has no portion protruding from the outer surface. 2. The shaft for excavating a shaft according to claim 1, wherein the depressions pressed from the outer surface to the inner surface of the cylinder are partially spherical, and the depressions are distributed in a staggered manner on the cylindrical surface. 3. The shaft digging casing according to claim 1, wherein the depression pressed from the outer surface of the cylinder toward the inner surface forms a groove having a partially circular cross section perpendicular to the axis of the cylinder. 4. A shaft shaft excavating casing according to claim 1, wherein the depression pressed from the outer surface of the cylinder toward the inner surface forms a groove having a partially circular cross section spirally continuous with the axis of the cylinder. 5. The method according to claim 1, wherein the depressions pressed from the outer surface of the cylinder toward the inner surface form two spirally continuous partial circular cross-sections inclined at opposite angles with respect to the axis of the cylinder. Shaft excavation casing as described