JPH0480496A - Head tube for casing excavation technique - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to foundation piles for architectural structures such as bridge piers for roads and railways and buildings, landslide prevention piles, parent piles for continuous underground walls, etc. This invention relates to a first tube for a casing excavation method used for digging various pile holes.

[Conventional technology]

The casing construction method involves pushing a cylindrical tube (casing tube) into the ground using a head machine, an earth auger machine, a fully rotating all-casing machine, etc., and scraping up the earth and sand inside the pipe with a screw auger or grabbing it with a hammer packet, etc. be.

When this method is applied to soft ground, the small amount of chips discharged to the outer circumference of the cylindrical pipe during rotary excavation is consolidated onto the hole wall by the outer circumferential surface of the pipe, and this compaction has the effect of preventing the wall of the hole from collapsing. .

However, in recent years, due to the development of excavation equipment, the size of buildings, and increased safety, excavation has begun to take place in rock formations that had previously been avoided, and problems have arisen in this case.

In other words, in rock, it is almost impossible to compact the hole wall surface, and although the amount of milling powder that fills the outer periphery of the cylindrical pipe, it causes solidification in the gap called "milling powder clogging".
The resulting increase in resistance makes it impossible to rotate the cylindrical tube.

Therefore, various measures are being considered to alleviate this problem. The technique of Utility Model Application Publication No. 2-5488 is also an example.

[Problem to be solved by the invention]

In excavation using a fully rotating all-casing machine, a cylindrical tube consisting of a leading tube 1 and a tube 11 is used, as shown in FIG. 6, and by adding tubes it is possible to dig a hole to a depth of 40 m or more.

Excavation proceeds while grabbing the earth, sand, and core inside the pipe out of the hole with a hammer club H. However, once the earth, sand, cobbles, pumice layer, etc. Scraps, powder) A begins to fill the gap around the pipe periphery without being consolidated on the hole wall surface.

In order to prevent this, the technology of Utility Model Application Publication No. 2-5488 creates a groove on the outer periphery of the leading pipe to create a space where the milled powder should be filled and a discharge path, but this method does not allow it to penetrate deep into the rock. If the gap exceeds the length of the leading pipe and the hole depth reaches 40 m, the milled powder will eventually fill the gap and solidify, and the resistance will stop the rotation of the cylindrical pipe.

This phenomenon is remarkable in slate, limestone, shale, and fine-grained sedimentary rocks. Therefore, in such a case, it is necessary to reverse the cylindrical pipe just before it comes to a stop so that the cylindrical pipe cannot be pulled out in order to secure a gap, which poses a problem in increasing the excavation speed and increasing the maximum excavation length.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention includes a slope that is disposed on the outer periphery of the leading tube from the digging blade attachment part toward the rear in the rotational direction of the tube toward the rear end of the tube. A plurality of milling grooves are provided, and a milling powder introduction hole is provided at a position set back a predetermined distance from the tip of the cutting blade so as to pass through the milling groove into the inside of the pipe.

[Operation] The chips flowing out from the tip of the cutting edge to the outer periphery of the cylindrical tube move upward along the groove on the outer periphery due to the resistance between the rotational force and the hole wall surface, and sequentially enter the pipe through the chips introduction hole. Pushed in.

If a groove is simply provided as in Utility Model Application Publication No. 2-5488, for example, when drilling a deep hole of more than 30 m in a slate layer, the groove will become clogged and the function of discharging the milled powder will be lost, and the gap around the outer circumference of the pipe will be blocked. However, as described above, if the moving chips are taken into the pipe one after another, the discharge function of the grooves is maintained, and the clogging of the chips on the outer periphery of the pipe is eliminated.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2.

As shown in the figure, the leading pipe 1 is provided with milling grooves 3 at a predetermined pitch P on its outer periphery, extending obliquely upward at an inclination angle of α0 from the mounting portion of the excavating blade 2. The groove 3 in the figure was formed by welding a rectangular iron plate 4 to the outer surface of the tube for ease of workability, and forming the groove in the recess between the iron plates, but if the tube was thick enough, it could be formed directly on the outer circumference. It can also be processed. Further, the groove 3 may ascend in a spiral manner, and the groove width may be made larger than the pitch when installing the excavating blades 2, as shown in Fig. 3, so that a plurality of excavating blades can be covered. It may be something that has been done.

However, the direction of inclination of the groove 3 must be determined in such a direction that the inflowing milling powder rises up the inside of the groove due to friction with the hole wall surface when the cylindrical tube rotates.

5 is the milling powder introduction hole which is the key point of this invention;
It penetrates inside the tube 1. This hole 5 can have any shape such as a circle, an ellipse, or a rectangle. In addition, it may be provided in each milling groove, or it may be provided in each plurality of grooves.Furthermore, in order to suppress a decrease in torsional rigidity of the leading pipe,
As shown in FIG. 4, the hole positions may be alternately shifted up and down.

The hole size is preferably such that the diameter is larger for a round hole, the shorter axis for an elliptical hole, and the shorter side for a square hole is larger than the wall thickness of the leading pipe. Below this, especially below 50 kaku, milled flour becomes easily clogged.

Further, the hole 5 is preferably positioned at least 30 C11 away from the cutting edge of the excavating blade in the direction of the tube axis, since if dirt or core inside the tube becomes an obstacle, the flow of milled powder into the tube will be hindered.

In addition, when the soft stratum up to the bedrock is deep and it is desired to have the effect of a consolidation plate on the hole wall surface, the hole 5 should be placed as far away from the cutting edge as possible within the range of the leading pipe, and the sloped recessing should be performed as shown in Figure 5. The milled powder may be taken into the pipe after being moved from the powder groove 3 to the collecting groove 6. In this configuration, the groove 3 is completely filled with the flowing milled powder, which is convenient for pressing against the hole wall surface. good. 7 in the figure is a ring attached to create the collecting groove 6.

In addition, when the introduction hole 5 is provided in the groove 3, the outlet of the groove 3 is placed between the iron plates 4 above the hole 5, as shown in FIG. A baffle plate 8 may be attached to close or narrow the space.

Below are the results of the effectiveness confirmation test.

In the test, a casing was excavated using a 240 horsepower earth auger using a leading pipe and tube with a diameter of 1000 m+.

The leading pipe is a general one without a groove on the outer periphery (comparison product),
As shown in Fig. 1, a chip groove 3 is provided between each excavation blade 2,
As shown in FIG. 4, each of the milling grooves was provided with milling powder introduction holes 5 in a staggered manner with the height position alternately changed (product of the present invention).

The excavated strata were roughly 4 m each of sandy silt, shale, and tuff from the surface, with a slate layer underneath, and the hole depth was 15 m (3 m deep into the slate).

As a result, although the comparison product did not result in a complete stoppage due to powder clogging, there was a clear difference in digging time as shown in the table below.

This is because in the comparison product, the rotational resistance increases when it enters the deep slate layer, so it is necessary to reverse the cylindrical tube just before it stops to adjust the amount of the tube to remove it, and to secure a gap around the tube's outer periphery. Depends on what you did.

In addition, when excavating hard rock using the leading pipe of the present invention, it is preferable to inject an appropriate amount of water into the pipe from the ground surface as described below. That is, the injected water flows out of the tube from the cutting edge, washes away the chips in the groove, and returns into the tube through the introduction hole. Since hard rock chips are grains with a high quartz content, they normally accumulate between the holes and the hole wall, accelerating the wear of the cylindrical tube, but this can be reduced.

In addition, the injected water cools the cutting edge and prevents cutting edge wear due to frictional heat.

〔effect〕

As described above, in the leading pipe of the present invention, the chips that have come out of the pipe are raised up along the grooves and taken into the pipe via the introduction type, so that there is no possibility of chips clogging and the resulting Increase in rotational resistance of the cylindrical tube is effectively prevented.

Therefore, even when excavating slate, shale, and fine powder rocks, it is possible to increase the excavation speed and increase the maximum excavation length, which also leads to a longer life of the leading pipe.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the leading pipe of the present invention, and FIG.
The figure is a cross-sectional view, FIG. 3 is a partial side view of another embodiment, FIG. 4 is a developed view of the main part of another embodiment, FIG. 5 is a perspective view of an example with collecting grooves, and FIG. The figure is a sectional view schematically showing an example of excavation using a full-turn all-casing machine. 1...Top pipe, 2...Drilling blade,
3... Inclined milling groove, 4... Steel plate, 5
...Drilling powder introduction hole, 6...Collecting groove, 7
...Ring, 8...Baffle board. Figure 5 Figure 6

Claims (1)

[Claims] (1) A leading pipe for a casing tube used in the casing excavation method, which has an inclined milling groove on the outer periphery of the pipe that extends from the excavator blade attachment part toward the rear in the rotational direction of the tube and toward the rear end of the tube. 1. A top pipe for a casing drilling method, characterized in that a plurality of holes are provided, and a chip introducing hole is provided at a position set back a predetermined distance from the tip of a cutting blade, through which the chip passes through the chip groove into the inside of the pipe.