JP2802604B2 - Non-vibration compacted sand pile construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-vibration type compacted sand pile construction method.

[0002]

2. Description of the Related Art Conventionally, after a casing is penetrated to a predetermined depth in the ground, the casing is pulled out appropriately, sand in the casing is discharged from a lower end of the casing to form a sand column, and the casing is re-penetrated. It is well known that the steps of compressing and compacting the sand column are sequentially repeated to form a compacted sand pile in soft ground.

[0003] In the above-mentioned conventional example of compacted sand pile formation, the casing is vibrated at the time of penetration and withdrawal.
The so-called vibrating type is generally used, but the vibrating type has disadvantages involving vibration and noise, so recently, a casing having a spiral blade attached to the outer peripheral surface is used, and the casing is rotated up and down, or The so-called non-vibration compaction sand pile construction, in which a casing having a smooth outer surface is forcibly raised and lowered by a powerful lifting device, is becoming widespread.

[0004] In the formation of compacted sand piles, it is important to specifically select and implement the length of the formed sand pile, which is the difference between the drawing length and re-penetration length of the casing and the difference. In the case of the vibrating type, the construction has not been established yet, and the construction specifications that can reliably form high-quality compacted sand piles have not been established yet.

[0005]

The problem to be solved by the present invention, that is, an object of the present invention is to provide a compact and high-quality compacted sand pile in view of the above-mentioned circumstances. An object of the present invention is to provide a vibration-free compaction sand pile construction method.

[0006] The sand according to the present invention includes sand-like substances such as gravel and crushed stone other than sand.

[0007]

In order to solve the above-mentioned problems, in a first method of the present invention, a casing having a smooth outer surface is used. While performing with the casing elevating device that can obtain the force, one compaction sand pile growth L

It is determined based on the following equation.

[0008] In the first method, the length H of one withdrawal of the casing is determined as follows.

When determined based on the equation (3), a compacted sand pile having a predetermined diameter can be formed.

In the first method, the casing may be rotated (including reciprocating rotation) around the axis thereof at the time of penetration and withdrawal, or may not be rotated.

Next, in a second method of the present invention, a casing having spiral blades attached to the outer surface is used, and the casing is rotated in a screw manner at the time of penetration and withdrawal. L

It is determined based on the following equation.

In the second method, when the length H of one pull-out of the casing is determined in the same manner as in the first method, a compacted sand pile having a predetermined diameter can be formed.

In the second method, the casing rotates forward (rotates in the spiral direction) when penetrating the casing, and reversely rotates when the casing is pulled out. However, the ascending and descending speed is limited by the rotational speed of the casing and the pitch of the spiral blades.

Next, in the third method of the present invention, a casing having a spiral blade attached to the outer peripheral surface is used, a sand column having a diameter equal to the outer diameter of the spiral blade is formed by pulling out the casing, and the sand column is formed by re-penetration. While compressing and compacting the sand column, one compaction sand pile growth L

It is determined based on the following equation.

In this third method, the casing withdrawal length L for each time is calculated as

When determined based on the equation (4), a compacted sand pile having a predetermined diameter can be formed.

In the third method, the casing is given a rotation other than the screw type regardless of whether the casing is rotated forward or backward,
This is applicable when the casing rotates forward during initial penetration and is not rotated during removal and re-penetration.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION When a pillar 1 penetrates into the ground,
As shown in FIG. 1, the soil in the region I immediately below the column 1 is first compacted to form a rigid wedge 2, and this wedge 2 is formed.
Eventually, the soil in the surrounding area II is sequentially pushed to the side, and the base angle α of the wedge 2 in this case is

(Equation 5) Is required.

Similarly, when forming compacted sand piles in the noiseless compacted sand pile construction method, the casing 3
By re-penetration, the sand under the casing 3 is first compacted to form a rigid wedge 4, and the wedge 4 pushes the lower sand and the surrounding ground soil sequentially to the side to expand. It is considered that the compacted sand pile is formed and the surrounding ground soil is compacted (see Fig. 2).

FIG. 2 shows that, when the outer surface of the casing 3 is smooth or the outer surface of the casing 3 is provided with a spiral blade, when the screw 3 is rotated to perform drawing and re-penetration, That is, it is an explanatory view in the case of the first and second methods of the present invention. In this case, a sand column having the same diameter as the outer diameter is compacted in the casing 3 to form a compacted sand pile having an increased diameter. Will be.

The figure shows that the tip of the wedge 4 is
At the top of the surface, and the stage at which the formation of the newly formed sand pile portion 6 is completed. From this figure, the height of the newly formed sand pile portion 6, that is, one compaction sand pile growth L is obtained. ,

It can be seen that Equation (1) is required.

A spiral blade is provided on the outer surface of the casing 3, and the spiral blade may be rotated by a method other than the screw type, regardless of whether the rotation is normal or reverse. And the case of not rotating at the time of re-penetration, where the sand column having a diameter equal to the outer diameter of the spiral blade is compacted in the casing 3 with the spiral blade,
In the case of the third method of the present invention, one compacted sand pile growth L is:

It can be obtained by the following equation.

In any of the first to third methods of the present invention, when a single compaction sand pile growth L is determined and executed based on the above-described formula, the length is determined in accordance with the pull-out length of the casing. The diameter of the formed sand pile changes.

FIG. 3 is an explanatory view in the case of forming a formed sand pile having a predetermined diameter in the first and second methods of the present invention.
Assuming that the volume of the sand column 7 formed in the step of pulling out the casing 3 is equal to the volume of the compacted sand pile portion 6 formed in the step of re-penetrating the casing 3.

The formula (3) holds, and the length H of one pull-out of the casing 1 when forming a compacted sand pile having a predetermined diameter is obtained.

Since the length of one re-penetration of the casing 1 is obtained by (HL), when forming a compacted sand pile having a predetermined diameter, the drawing length H obtained as described above is equal to the drawing length H. It can be seen that the re-penetration length (HL) should be used.

In the third method of the present invention, when a compacted sand pile having a predetermined diameter is formed, one drawing length H of the casing is similarly set as follows.

## EQU4 ##

In each method of the present invention, the length L of one compacted sand pile and the length H of pulling out the casing are determined based on the above-mentioned formula, and the construction is performed. And it can be easily created,
Needless to say, the term “determined based on” according to the present invention does not mean that it is strictly as such.

In the first method of the present invention using a casing having a smooth outer surface, the casing is penetrated and pulled out by a casing elevating device which can obtain a reaction force from a leader for supporting and guiding the casing. One example of the casing elevating device is disclosed in Japanese Patent Publication No. 6-78617.

The above-mentioned known example is of a rack and pinion type in which a rack is provided on a leader and a pinion engaging with the rack is provided at an upper end of a casing and a rotation mechanism thereof is provided. The casing lifting device used in the method is not limited to this.

In the first method of the present invention, it is optional whether or not the casing is rotated (including reciprocating rotation) about its axis when the casing is moved up and down. Becomes easier.

An example of an apparatus used in carrying out the second and third methods of the present invention is disclosed in JP-B-62-27204, but is not limited to this. A casing elevating device as used in the first method may be used instead of the wire.

[Brief description of the drawings]

FIG. 1 is a dynamic diagram of the ground soil when a pillar body penetrates into the ground.

FIG. 2 is an explanatory diagram of one calculation of compaction sand pile growth in the first and second methods of the present invention.

FIG. 3 is an explanatory diagram of one calculation of a casing withdrawal length when a compacted sand pile having a predetermined diameter is formed by the first and second methods of the present invention.

[Explanation of symbols]

1: pillar, 2: wedge, 3: casing, 4: wedge,
5: Existing sand pile part, 6: New sand pile part, 7: Sand column.

──────────────────────────────────────────────────続 き Continuation of front page (56) References Geotechnical Engineering Research Presentation Vol. VOL. 31, NO. 2, P. 49-50 (1996) (58) Investigated field (Int. Cl. ⁶ , DB name) E02D 3/10 104 E02D 3/08

Claims (5)

(57) [Claims] After the casing has been penetrated to a predetermined depth in the ground, the casing is pulled out to an appropriate length, the sand in the casing is discharged from the lower end of the casing to form a sand column, and the casing is re-penetrated, The step of compressing and compacting the sand column is sequentially repeated to form a compacted sand pile having a large diameter in soft ground.・ In addition to using a casing lifting / lowering device capable of obtaining a reaction force from the guiding leader, one compaction of sand pile growth L is performed as follows: Non-vibration compaction sand pile construction method characterized by the following. 2. After the casing has penetrated to a predetermined depth in the ground, the casing is pulled out appropriately, and the sand in the casing is discharged from the lower end of the casing to form a sand column. The step of compressing and compacting the sand column is sequentially repeated to form a compacted sand pile having a large diameter in soft ground, using a casing provided with spiral blades on the outer surface thereof, A non-vibration compacted sand pile forming method characterized in that the compacted sand pile growth L is determined on the basis of the following equation (1) while being rotated in a screw type at the time of drawing. 3. After the casing has been penetrated to a predetermined depth in the ground, the casing is pulled out to an appropriate length, the sand in the casing is discharged from the lower end of the casing to form a sand column, and the casing is re-penetrated; The step of compressing and compacting the sand column is sequentially repeated, and when forming a compacted sand pile having a large diameter in soft ground, using a casing provided with spiral blades on the outer peripheral surface thereof, a step of extracting the casing A sand column having a diameter equal to the outer diameter of the spiral blade is formed by compression, and the sand column is compressed and compacted by re-penetration, and a single compaction sand pile growth L is expressed by the following equation. Non-vibration compaction sand pile construction method characterized by the following. 4. The length H of one casing withdrawal is defined as: The non-vibration compacted sand pile construction method according to claim 1 or 2, which is determined based on the following. 5. A casing withdrawal length H for one time is given by: 4. The method for constructing a non-vibration compacted sand pile according to claim 3, wherein the method is based on: