JPS5819836B2 - Large-diameter vertical hole drilling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large-diameter vertical hole excavation method for constructing large-diameter concrete piles.

Conventionally, as a method of excavating a large-diameter pit for constructing large-diameter cast-in-place concrete piles, a casing is built into the ground and the interior of the casing is excavated with an excavator such as a hammer grab or a rotary packet. There is.

However, with this conventional method, in ground with high excavation resistance such as hard ground, the excavation force of the grab, packet, etc. is weak, so the excavation speed is extremely slow.
This resulted in a significant decrease in work efficiency.

The purpose of the present invention is to provide a large diameter vertical hole excavation method that can eliminate the drawbacks of the conventional method, and its characteristics are as follows:
At the same time, a large-diameter casing is press-fitted into the ground, and at the same time, a small-diameter pilot hole is drilled vertically into the casing from the inner diameter of the casing using a screw auger, and then the remaining unexcavated soil in the casing is excavated with an excavator and removed. be.

The casing used in the present invention is a hollow cylindrical body such as a steel pipe, and preferably has a large number of digging blades at its tip (lower end) as shown in Figure 9. For press-fitting, a method is adopted in which a static load, a pressing force, a dynamic load such as vibration, or both loads are applied to the upper end of the casing, and the casing is rotated in one direction or reciprocated (oscillated).

Preferably, the casing may be equipped with a device for selectively rotating and rocking the casing.

Further, the excavation diameter of the screw auger is set to an appropriately small diameter such as about 1.1 of the inner diameter of the casing.

2 3 Furthermore, to excavate the inside of the casing after drilling the pilot hole, various excavators such as a hammer grab excavator, a grab bucket excavator, a rotary packet excavator, a packet excavator with a screw compare, and a screw auger are used. .

The present invention will be described in detail below with reference to the drawings.

First, as shown in the first diagram, a large-diameter casing with a diameter of 150 cm, for example, is continuously rotated counterclockwise while applying a static load to its upper end to compact it perpendicularly to the ground E, and at the same time, the casing is A small-diameter pilot hole 3 is drilled on the axis inside the casing by a screw auger 2 having an excavation diameter of about 1 of the inner diameter (.

In this case, since the pilot hole 3 in the casing is drilled at the same time as the casing 1 is press-fitted, the casing
The ground inside is loosened, thereby making it easier to press fit the casing 1 and drill the pilot hole.

Note that the direction of rotation of the screw auger 2 is preferably opposite to that of the casing 1.

The excavated soil is discharged upward by the screw auger 2.

After the casing 1 is built to a predetermined depth and a pilot hole 3 is drilled to approximately the same depth as the casing 1 (Fig. 2), the rotation is stopped as shown in Fig. 3. The screw auger 2 is pulled upward, thereby holding the excavated soil between its screw blades and discharging it upward, and then leaving unexcavated residual soil 4 with a doughnut-shaped cross section between the inner surface of the casing 1 and the casing 1. A pilot hole 3 that extends vertically and concentrically is exposed.

Next, as an example, a packet excavator 5 with a screw conveyor is inserted and lowered into the casing 1 from the upper end as shown in the fourth figure, and the remaining soil 4 in the casing 1 is excavated and discharged.

Here, the packet excavator 5 with the screw conveyor
As shown in FIG. 8, a cylindrical packet 9 is fixed concentrically to the tip of a ram 8 of a hydraulic cylinder 7 whose one end is fixed to a cylindrical holder 6, and the packet 9 has a bifurcated conical shape on the lower end surface of its opening. A screw conveyor 12 rotated by a hydraulic morph 11 was positioned concentrically within the packet, and the caps 10, 10 were opened to the position shown by the chain line in Figure 8. In this state, the packet 9 is lowered by driving the hydraulic cylinder 7 1, and its cap 10.10 is pushed into the ground along the inner surface of the casing, and earth and sand is carried into the packet 9 by the screw conveyor 12, and when it is full, the cap is removed. 10,
10 is closed, the casing 1 is lifted out of the casing 1, the earth is discharged, and excavation is performed again.

13 is a hydraulic cylinder for opening and closing the cap; 14 (O connecting rod; 15... is a locking piece supported swingably so as to be able to move forward and backward from the outer circumferential surface of the holder 6; this is moved toward and away from the inner surface of the casing 1; The holder 6 is engaged and disengaged from the casing.

16 is a cam that moves the locking piece 15 back and forth, and 17 is a hydraulic cylinder that moves the cam 16.

When excavating the remaining soil 4, the remaining soil 4 is already loose as described above and has a donut shape centered on the pilot hole 3, so it is easy to collapse and is easily excavated.

In this way, the remaining soil 4 inside the casing 1 is sufficiently excavated and removed to form a predetermined dog-diameter vertical hole 18 inside the casing 1.

Next, the reinforcing bar cage 19 is inserted into the pit 18 from the upper end of the casing 1 as shown in the fifth figure, and then concrete is poured into the pit 18 through the tremie pipe 20 as shown in the sixth figure.

Next, while the poured concrete has not yet hardened, the casing 1 is pulled upward while swinging as shown in Figure 7.

When the concrete hardens, large-diameter reinforced concrete 1
・Piles are built in the ground.

In addition, in the process of excavating the remaining soil 4 (Fig. 4), the reinforcing bar cage insertion process (Fig. 5), and the concrete IJ-casting process (Fig. 6), the casing 1 is swung, so that the surroundings of the casing are It is best to prevent the ground from becoming so compact that it becomes impossible to pull out the casing.

Depending on the ground conditions, the casing 1 may be rocked continuously or intermittently after the casing 1 is press-fitted until it is pulled out.

In the process of excavating the remaining soil 4 using the packet excavator 5 with a screw conveyor, if the casing 1 is swung as described above, the packet 9 during excavation will also be swung accordingly, making it more effective. Excavation will be carried out.

According to the large-diameter vertical hole drilling method of the present invention, while press-fitting the casing, a small-diameter pilot hole is excavated vertically into the casing using a screw auger having a diameter smaller than the inner diameter of the casing, thereby constructing the hole underground. A cylindrical unexcavated residual soil with a donut-shaped cross section is left inside the casing, and this residual soil is isolated from the surrounding ground by the casing and is already loose, and moreover, it is easy to collapse after passing through the pilot hole. This is extremely easy to do, and allows for efficient drilling of large-diameter shafts.

[Brief explanation of the drawing]

Figures 1 to 7 are cross-sectional views showing each process of the embodiment of the present invention, and Figure 8.
The figure is an enlarged longitudinal sectional view of a packet excavator with a screw conveyor used in the present invention, and FIG. 9 is an enlarged front view of the lower end of the casing. 1... Casing, 3... Pilot hole, 4... Unexcavated remaining soil, E... Ground.

Claims (1)

[Claims] 1. While rotating a large-diameter casing and press-fitting it into the ground, a small-diameter pilot hole is excavated vertically into the casing using a screw auger having a diameter smaller than the inner diameter of the casing; A large diameter vertical hole excavation method consisting of excavating and discharging excavated soil with an excavator, and 711).