JPS6227204B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The purpose of the present invention is to improve the ground by creating compacted sand piles of granular material such as sand in soft ground. This relates to the construction method for compacted sand piles.

[Conventional technology and its problems]

This construction method, which uses a hollow pipe with spiral blades, rotates the pipe into soft ground, and then pulls it out to the ground surface while discharging sand into the ground has been known as the sand drain method. (For example, see Japanese Patent Application Laid-Open No. 51-30113).

The above construction method simply pulls out the hollow pipe while discharging the sand, and does not re-penetrate it midway through, so what is formed in the ground is simply a sand pile (sand drain) and is tightened. It is not a hardened sand pile.

As a construction method for creating compacted sand piles, for example, as shown in Japanese Patent Application Laid-Open No. 48-37906, a vibrating machine is installed at the top of a hollow pipe, and the vibrating force is used to create a concrete pile in the ground. The hollow tube is then pulled out for a certain length and the sand inside the hollow tube is discharged into the ground.
There is a construction method that creates compacted sand piles by penetrating the hollow pipe while vibrating it again.

However, this construction method causes pollution problems due to large vibration and noise, and has the problem that it cannot be constructed in areas close to private houses, offices, etc.

Furthermore, Japanese Patent Application Laid-Open No. 49-45518 discloses a method of constructing lime piles using hollow auger screws, but since the pitches of the screw blades in this case are unevenly spaced, they are always ground level. It also has no function of compacting the column of lime bags discharged by the tip of the auger crew.

Therefore, such technology cannot be directly applied to the construction method of compacted sand piles.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and provide a method for constructing compacted sand piles that is free from vibration and has a sufficient compaction effect.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a hollow tube provided with spiral propulsion blades of a constant pitch on the outer peripheral surface when constructing a compacted sand pile of powder and granular materials such as sand in soft ground. After the initial penetration process, in which the hollow tube is rotated forward to a predetermined depth and penetrated, the sand is discharged from the lower end of the hollow tube, and the sand is pulled out for a certain length while rotating in the opposite direction, and the Repeat the cycle of sequentially carrying out the re-penetration process to the ground surface, in which the pipe is penetrated while rotating forward again and the above-mentioned discharged sand is compacted, and in each of the above processes, the feed rate when penetrating and withdrawing the hollow pipe is adjusted per rotation. This is set to one lead of the propulsion blade.

〔Example〕

First, as shown in FIG. 1, a hollow tube 7 equipped with spiral propulsion blades 4 of a constant pitch is penetrated while rotating to a predetermined depth (initial penetration step). In this case, the raising and lowering temperatures of the rotary penetrating device of the hollow tube 7 are set so that the penetrating feed amount is equal to one lead of the propulsion blade per rotation. When reaching a predetermined depth, the rotation is stopped and sand is thrown into the hollow tube 7 from the hoppers 5 and 6 as shown in the figure. Next, compressed air is supplied into the hollow tube 7 to sufficiently increase the internal air pressure, and then the hollow tube 7 is pulled out for a certain length while rotating in the opposite direction, and the sand inside is removed from the hollow tube. 7 into the ground (pulling process). In this case, the feed in the drawing direction is also set to one lead per revolution, as described above.

As described below, the hollow tube 7 is again rotated in the normal direction (in the same direction as the initial penetration step), and the tube is penetrated while being rotated by one lead per rotation (re-penetration step). This re-penetration process compacts the discharged sand and causes it to expand into the surrounding ground.

Thereafter, the above-described cycle of extraction process and re-penetration process can be repeated in sequence until reaching the ground surface. FIG. 2 shows this operation cycle at the depth of the tip of the hollow tube 7.
This is a graph showing the relationship between GL and time T.

In each of the above steps, the feed amount of the hollow tube when it is inserted by forward rotation and when it is pulled out by reverse rotation is set to be one lead per rotation. Therefore, the ground is not disturbed during both penetration and withdrawal, so when the cycle of withdrawal and re-penetration is repeated after the initial penetration, there is less resistance due to the rotation of the hollow tube, and during re-penetration, the rotation Power can be efficiently converted into propulsive force. This propulsion force and the weight of the rotary penetration device can exert a compaction force on the discharged sand.

Note that an on-off valve or the like is provided at the lower end of the hollow pipe 7 as a conventionally known means to prevent backflow of the ground.

Next, the device shown in FIG. 3 will be explained.
1 is a crane main body, and 7 is a hollow tube, the upper end of which is provided with hoppers 5 and 6 for charging powder and granular materials such as sand. 4 is a propulsion blade fixed to the outer periphery of the hollow tube. 3 is an example of a driving means for rotating a hollow tube,
It is composed of an electric motor or a hydraulic motor and a speed reducer, and is attached to the leader 2 so that it can be moved up and down. This may be a hydraulic motor. 8 is a bucket that lifts and lowers the leader 2, and supplies sand, etc. to the hopper 5.

To give a concrete example, the diameter of the hollow tube is 400 mm, the width of the propulsion blade is 150 mm, the inclination of the propulsion blade is 15°, and the number of turns of the propulsion blade is
The construction length is 15m using a rotary penetration device consisting of 10 rolls, penetration device weight of 10 tons, and a 45KW rotary drive device.
Compacted sand piles were created.

The specifications of the rotary penetration device described above are an example of numerical values derived from the conditional expression for the hollow tube with propulsion vanes to penetrate in a threaded manner and to exert the propulsive force of the hollow tube as compaction force. A hollow pipe with spiral blades that penetrates the ground while excavating it, such as an earth auger, discharges sand into the ground while being pulled out, and then penetrates again to compact the sand pile. Penetration and withdrawal will be performed while disturbing the
The resistance received from the ground is large, making it inefficient.

The diameter expansion is (sand pile cross-sectional area) / (hollow pipe cross-sectional area) 3
The results obtained above and measured as compaction force are:
It was found that about 10 tons could be obtained. This compaction force is the value obtained by subtracting the friction of the ground and hollow tube from the propulsion force and the weight of the equipment. If the penetration force is insufficient during penetration or if a larger compaction force is required, the number of windings of the propulsion blades may be increased, the width of the propulsion blades may be increased, or retraction force may be added. Furthermore, the sand pile diameter can be further expanded by applying air from inside the pipe during compaction.

Conventional rotary sand drain equipment does not use a sand meter to measure the amount of sand in the hollow pipe, but estimates the amount of sand discharged into the ground based on the capacity of the bucket and the number of times sand is added. The only way to check whether sand was being discharged from the hollow tube into the ground was to check whether sand remained inside the hollow tube after it was pulled out above the ground surface. However, in this embodiment, a sand meter is used to ensure quality control of the sand pile, and a depth meter is used to display the quality of sand discharge from the hollow pipe and the penetration depth of the hollow pipe. In combination with this, it is possible to determine the re-penetration length so as to create a predetermined sand pile diameter from the amount of discharged sand.

〔Effect of the invention〕

The present invention does not disturb the ground because the feed amount during penetration and withdrawal of the hollow tube is set to one lead of the propulsion amount per revolution as described above. Therefore, when compacting the discharged sand by repeatedly pulling out and re-penetrating the hollow tube, the rotational force can be efficiently converted into propulsive force (compaction force).

Therefore, compacted sand piles can be efficiently created using a simple device that is vibrationless and noiseless, without using any special compaction equipment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of each step of the construction method of the present invention, FIG. 2 is a graph showing a construction cycle of the construction method of the present invention, and FIG. 3 is a partially cutaway side view showing an example of construction equipment. 3...Rotary drive device, 4...Propulsion blade, 5, 6...
...Hopper, 7...Hollow tube.

Claims (1)

[Claims] 1. When constructing compacted sand piles of powder and granular materials such as sand in soft ground, a hollow tube with spiral propulsion blades of a certain pitch on the outer circumferential surface is used, and the hollow tube is vertically pushed to a predetermined depth. After the initial penetration process in which the sand is penetrated while rotating, there is a drawing process in which the sand is discharged from the lower end of the hollow tube and pulled out for a certain length while being rotated in the opposite direction, and then the sand is penetrated again while being rotated in the forward direction to perform the above-mentioned discharge process. It is characterized by repeating a cycle in which the re-penetration process for compacting the sand is carried out sequentially to the ground surface, and in each of the above processes, the feed amount when penetrating and withdrawing the hollow tube is set to one lead of the propulsion blade per rotation. A construction method for compacted sand piles.