JP2001098550A - Slime treating method for excavating hole for constructing foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slime treating method capable of completely removing slime accumulated on the hole bottom and of constructing a highly reliable foundation. SOLUTION: In a method for constructing a foundation by placing concrete 7 in an excavating hole 1 after forming the excavating hole 1 while filling muddy water 2, before placing the concrete 7, a coagulant is injected and agitated in the hole bottom of the excavating hole 1 via an injection pipe 5 to turn slime accumulated on the hole bottom into a block to be discharged outside the excavating hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slime treatment method for a drilling hole for foundation construction, and more particularly, to a method for constructing a pile foundation or an underground continuous wall foundation using cast-in-place concrete. The present invention relates to a method for removing slime deposited on slime.

[0002]

2. Description of the Related Art Cast-in-place concrete piles and underground continuous walls are constructed by excavating holes while filling with muddy water, and then laying a steel cage in the excavation holes and pouring concrete. Slime (fine clay particles) floats in the excavation hole before concrete is poured, and part of it is deposited at the bottom of the hole. Casting concrete while slime is deposited on the bottom of the hole may cause uneven settlement and a decrease in bearing capacity, so slime is generally treated.

[0003] As a method of treating this slime, there has been conventionally known a method of sucking it with a sand pump and forcibly discharging the slime out of a drill hole. However, the method using a sand pump does not completely remove slime. This is shown in FIG.
This will be described with reference to FIG. 5, the legend is the same as that shown in FIG.

When the excavation is completed, at the bottom of the excavation hole,
As shown in (a), slime (including silt) is deposited as if mixed in a sand layer. Therefore, FIG.
As shown in (b), even when the slime is forcibly discharged by the sand pump, the slime remains in the sand.

[0005] In addition, a long period of setup such as the installation of a reinforcing steel cage or a tremy tube is required before concrete is cast, and slime is newly settled and deposited. For this reason, as shown in FIG. 5C, when the concrete is cast, some slime is pushed up by this, but the slime remains below the concrete. This residual slime has an adverse effect on the substructure as described above.

[0006]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above technical background, and has the following objects. It is an object of the present invention to provide a slime treatment method capable of completely removing slime deposited on the bottom of a hole and building a highly reliable foundation.

[0007]

The present invention employs the following means to achieve the above object. That is, the present invention provides a method for forming a drilling hole while filling with muddy water and then casting concrete in the drilling hole to build a foundation. A slime treatment method for excavation holes for foundation construction is characterized in that slime deposited at the bottom of the holes is floculated by injecting and aggregating a coagulant and discharged outside the excavation holes.

According to the present invention, when the aggregating material is injected into the bottom of the drilling hole and stirred, the slime at the bottom of the hole aggregates to form flocs. The flocs are stirred and floated with the sand, but settle and deposit on the sand because the sedimentation speed is lower than that of the sand. That is, the slime mixed in the sand is completely separated from the sand without being mixed due to the formation of the flocculated floc. In this way, concrete is poured into the excavation hole in a state where the slime flock and sand are completely separated from each other, whereby the flock is pushed up and discharged out of the excavation hole. Therefore, a slime-free layer of gravel and sand is formed at the bottom of the hole below the concrete, and the required bearing capacity is exhibited.

At the time of placing concrete, a tremy tube is erected in the excavation hole. An injection pipe can be inserted into the tremy tube, and the coagulant can be injected through the injection pipe. A stirring blade for stirring the bottom of the hole can be provided at the tip of the injection pipe so as to be able to expand and contract. Before embedding the tremy tube in the borehole, a coagulant may be injected into the bottom of the borehole, and the slime flock formed thereby may be forcibly discharged by a pump in advance.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention. This embodiment is an example of constructing a cast-in-place concrete pile.

The cast-in-place concrete pile is constructed by a well-known benot method, earth drill method, reverse circulation method, or the like, and a hole 1 is excavated with a drilling machine (not shown) while filling with muddy water 2 (FIG. 1 (a)). When the excavation depth of the hole 1 reaches a predetermined value (FIG. 1B), the reinforced cage 3 and the tremee pipe 4 are erected in the hole 1 (FIG. 1).
(C)).

Next, as shown in FIG. 1 (d), a coagulant injection pipe 5 having a stirring blade 6 provided at the tip is inserted into the tremy tube 4, and the coagulant is inserted into the bottom of the drilling hole 1. And stirred by the stirring blade 6. As the coagulant, well-known aluminum sulfate or a polymer-based material can be used.
As shown in an example in FIG. 2, the stirring blade 6 is attached to the tip of the injection pipe 5 via a spring 10 so as to be able to expand and contract, and is constantly urged by the spring 10 in a direction in which it is expanded.

As shown in FIG. 3A, the injection pipe 5 can be set in the tremy tube 4 with the stirring blade 6 closed and inserted into the drilling hole 1 together with the tremy tube 4. . When the bottom of the drill hole 1 is reached, the injection pipe 5 is made to protrude from the tip of the tremee pipe 4 and the spring 10
(FIG. 3B). When the injection pipe 5 is removed, when the injection pipe 5 is raised, the stirring blade 6 closes against the spring 10 and only the injection pipe 5 can be pulled up (FIG. 3C).

Referring to FIG. 1 again, after the coagulant is injected, the injection pipe 5 is removed as described above, and concrete 7 is poured into the excavation hole 1 via the tremee pipe 4 (FIG. 1).
(E)). Concrete 7 is poured while pulling up the tremy tube 4, and is filled upward from the bottom of the borehole 1. The mud 2 is replaced by concrete 7 and in this way a cast-in-place concrete pile is built (FIG. 1).
(F)).

FIG. 4 shows the behavior of the slime in the excavation hole 1 in the process of constructing the cast-in-place concrete pile as described above.
This will be described with reference to the schematic diagram shown in FIG. FIG. 4 (a) shows a state in which excavation is completed, and as described in the section of the prior art with reference to FIG. 5 (a), slime is settled and deposited together with silt on the bottom of the hole, and this slime is deposited. It is mixed in the sand layer as if kneaded.

When the coagulant is poured into the bottom of the hole and stirred, as shown in FIG. 4 (b), the slime coagulates and flocs are formed. The flocs are stirred and floated with the sand, but settle and deposit on the sand because the sedimentation speed is lower than that of the sand. That is, the slime mixed in the sand is completely separated from the sand without being mixed due to the formation of the flocculated floc. Therefore, as shown in FIG. 4 (c), when concrete is poured into the excavation hole with the slime floc and the sand completely separated, the floc is pushed up by the concrete. As a result, only slime-free gravel and sand layers are formed at the bottom of the hole below the concrete, and the required bearing capacity is exhibited.

The coagulant is injected at a time closer to the time when concrete is poured, so that the sedimentation of new slime is less. Therefore, it is preferable to inject the coagulant through the injection pipe 5 using the tremy pipe 4 as in the above embodiment. . However,
The present invention is not limited only to the above-described injection mode. In other words, the injection and stirring of the coagulant are performed as shown in FIG.
The step (b) may be performed at the completion of the excavation, and the flocs of the aggregated slime may be sucked by a sand pump or the like and discharged out of the excavation hole.

In this case, there is a possibility that new slime may accumulate due to the lapse of time until the concrete is poured. However, the sand pump does not completely remove the slime floc but remains on the sand layer. New slime will be deposited on top. For this reason, the state where the sand layer and the slime are separated from each other is maintained, and the slime is discharged to the outside of the excavation hole together with the floc by casting concrete, so that a required bearing capacity can be expected.

In the above embodiment, the case where the cast-in-place concrete pile is constructed has been described. However, the present invention can be applied to the case where the underground continuous wall is constructed. Further, the mode of pouring and stirring the coagulant is only an example, and various modes can be adopted.

[0020]

As described above, according to the present invention, the coagulant is injected into the bottom of the excavation hole and stirred to form slime flocs, so that the slime is completely separated from the sand and gravel layers. . Therefore, a slime-free support layer is formed below the poured concrete, and a high-quality and reliable foundation can be built.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a stirring blade.

FIG. 3 is a diagram illustrating expansion and contraction of a stirring blade.

FIG. 4 is a schematic view showing a behavior of a slime when an aggregating material is injected and stirred.

FIG. 5 is a schematic diagram showing the behavior of slime in the case of the conventional method.

[Explanation of symbols]

 1: drill hole 2: muddy water 3: reinforced cage 4: tremy pipe 5: injection pipe 6: stirring blade 7: concrete 10: spring

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Nakajima 2-3-5 Misaki-cho, Chiyoda-ku, Tokyo Iron Construction Construction Co., Ltd. ) Inventor Kaoru Togashi 3-6 Kiuri, Yoshikawa-shi, Saitama F-term (reference) 2D041 BA14 EB01 2D045 AA02 BA04 CA24 2D049 GA03

Claims (5)

[Claims] After forming a borehole while filling with muddy water,
In the method of laying concrete in this excavation hole and constructing a foundation, before pouring the concrete, a coagulant is injected into the hole bottom of the excavation hole and agitated to deposit on the hole bottom. A slime treatment method for excavation holes for foundation construction, which comprises flocking slime that is present and discharging the slime outside the excavation hole. 2. The slime treatment method according to claim 1, wherein the flock is pushed up and discharged by placing concrete in the excavation hole. 3. The method according to claim 2, wherein an injection pipe is inserted into a tremy pipe for placing concrete built in the excavation hole, and the coagulant is injected through the injection pipe. Slime treatment method for excavation holes for foundation construction. 4. The slime treatment method for excavation holes for foundation construction according to claim 3, wherein an expandable and contractable stirring blade is provided at a tip of the injection pipe. 5. The method according to claim 1, wherein said flocks are forcibly discharged by a pump.