JPS6225808B2 - - 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 pipe is penetrated into the ground, and then the hollow pipe is pulled out for a certain length, and the sand inside the hollow pipe 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.

SUMMARY OF THE INVENTION An object of the present invention is to solve these 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 problems, the present invention uses a hollow pipe with spiral blades on the outer periphery to create a compacted sand pile of powder and granular materials such as sand in soft ground. After the initial penetration process in which the pipe is penetrated to a predetermined depth, there is a pull-out process in which sand is pulled out for a certain length while discharging sand from the lower end of the hollow tube, and a re-penetration process in which the hollow pipe is penetrated again and the discharged sand is compacted. The cycle of sequentially carrying out the steps up to the ground surface is repeated, and in the above-mentioned initial penetration process, withdrawal process and re-penetration process, the hollow tube is rotated and the surrounding ground within the range of its outer diameter is covered with the spiral blade. Each step is carried out while stirring.

〔Example〕

First, as shown in FIG. 1, the hollow tube 7 with the spiral blade 4 is penetrated while being rotated to a predetermined depth (initial penetration step). 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). Next, the hollow tube 7 is penetrated again while being rotated in the forward direction (in the same direction as the initial penetration step) (re-penetration step). Through this re-penetration process, the discharged sand is compacted, a compacted sand pile 9 is created, and the diameter of the compacted sand pile 9 is expanded into the surrounding ground.

Thereafter, the cycle of the above-mentioned 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.

The relationship between the rotation of the hollow tube and the vertical movement speed in each of the above steps is such that if the spiral blade advances by one lead of the spiral during one revolution, no disturbance of the ground will occur. The surrounding ground within the range of the outer diameter of the spiral blade is disturbed in each step.

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 spiral blade fixed to the outer periphery of the hollow tube. 3 is an example of a driving means for rotating a hollow tube,
It consists of an electric motor or hydraulic motor, speed reducer, transmission gear, etc. 8 is a bucket that goes up and down along with the leader 2, and the hopper 5
supply sand, etc.

To give a specific example, the hollow pipe diameter is 400mm, the width of the spiral blade is 50mm, the distance between the spiral blades is 30cm, the number of turns of the spiral blade is 3, the penetration device weighs 10 tons, and the construction is performed using a 45KW rotary drive device. Compacted sand piles with a length of 10 m were constructed.

In addition, in the initial penetration process or re-penetration process,
If the penetration force or compaction force is insufficient, it is sufficient to add a pulling force, and the diameter of the sand pile can be further expanded by applying compressed air from inside the pipe during compaction.

〔effect〕

As described above, in the present invention, the hollow tube is rotated in each of the initial penetration process, the extraction process, and the re-penetration process, and the ground is disturbed by its spiral blade, so that the friction with the known ground is significantly reduced. Therefore, the weight of the device effectively acts as a compaction force, making it possible to create sand piles that are sufficiently compacted. Moreover, the disturbance effect on the ground is limited to the maximum extent to the outer diameter of the spiral blade, and does not exert a disturbance effect on a range beyond that.

In addition, without using special compaction equipment,
Since compaction is performed only by re-penetrating the hollow pipe, compacted sand piles can be created without vibration or noise.

[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...Spiral blade, 5, 6
...Hopper, 7...Hollow tube.

Claims (1)

[Claims] 1. When constructing a compacted sand pile of granular materials such as sand in soft ground, a hollow tube with spiral blades on the outer periphery is used, and after an initial penetration process in which the hollow tube is penetrated to a specified depth. , a process of pulling out a certain length while discharging sand from the lower end of the hollow tube, and a re-penetration process of penetrating the hollow tube again and compacting the discharged sand, are repeated until the sand reaches the ground surface. , and characterized in that in the above-mentioned initial penetration step, extraction step and re-penetration step, each step is carried out while rotating the hollow tube and disturbing the surrounding ground within the range of its outer diameter by means of a spiral blade. A construction method for compacted sand piles.