JPS59126821A - Erection work of foundation pile - Google Patents

Abstract

PURPOSE:To construct a foundation pile to exactly support a structure by preventing the subsidence and cave-in of the ground above a cave by a method in which a hollow tube pile is inserted into an outer steel tubular pile provided with a slit and a packer, and cement milk is injected into the upper and lower part of the cave. CONSTITUTION:An outer steel tubular pile 3 is erected in a pit 5, and cement milk is injected into an inner hollow pile 1 set on the bottom of the pit 5. When the pile 1 alone is slightly pulled up from the bottom of the pit 5, the cement milk 6b flows out of the lower end of the pile 1 to pack the aperture between the pile 1 and the pile 3, and fills up between the pit 5b and the pile 3 through the slit 9 of the pile 3. After the pile is struck to the supporting ground, sand 7 is packed into the space between the piles 1 and 3, and cement milk 6a is packed onto the packer 8 between the pile 3 and the pit 5a. The subsidence and cave-in of the ground above a cave 4 can thus be prevented, and a foundation pile to exactly support a structure can be constructed.

Description

[Detailed description of the invention] be.

Generally, when a structure is constructed directly in a place where there is a cavity directly under the ground, the ground may cave in or subside, and the structure may be destroyed.

Conventionally, the cavities have been filled with cement mortar, ready-mixed concrete, cement bacilli, etc., but these have had the following problems. That is, (a) it is almost impossible or very difficult to confirm whether the filling has been completely applied to the target area.

口) At the time of design planning, the internal volume of the cavity cannot be accurately calculated, so accurate grasping of the filling quantity, etc. is almost beyond estimation and is uncertain. c) There is a risk of groundwater contamination due to the filling nozzle flowing out of the intended filling area.

Therefore, in such a case, as a reliable construction method, it is better to find a support layer in the ground deeper than the cavity and adopt a construction method in which the structure is supported by foundation piles. The same applies if there is an extremely permeable layer directly beneath the ground.

The present invention was created to carry out the above construction method,
Construction under such ground conditions can be achieved by using double-structured piles, i.e., hollow outer tube piles on the outside and hollow inner tube piles made of ready-made concrete piles, steel pipe piles, or cast-in-place piles on the inside. At the same time, the load of the structure is borne by the inner pile, and the abrasive force generated by natural or sudden collapse is applied to the outer pipe pile.

The construction method for hollow outer pipe piles is the pre-poling method, but the method that uses a stabilizing liquid such as muddy water as a drilling method does not allow the muddy water to completely wash away due to the existence of cavities, making it difficult to drill the holes. Not only will this not be possible, but it will also lead to groundwater contamination, which is inappropriate.

Therefore, in the present invention, the hole drilling method is performed by a down-the-hole hammer or tri-drilling using an earth auger (rock auger) or the like.

After drilling the hole to a specified depth using this method, the hollow outer pipe that is the outer pile is erected. However, if it is difficult to drill the hollow part and its lower part, the outer pipe of the outer pile can be erected using the hollow drilling method. Install to depth.

After constructing the outer pipe, thoroughly remove the slime deposited at the bottom of the hole using methods such as air lift.

After cleaning the bottom of the hole, install ready-made concrete piles, steel pipe piles, or cast-in-place piles as the inner piles, but if the inner piles are engineered concrete piles or steel pipe piles, the hole bottom is installed in the hollow part of these piles. After the injection is completed, the injection pipe is lifted up and the pre-built concrete pile or steel pipe pile that was erected before is removed before the cement milk has hardened. is pulled up several tens of centimeters, and the cement milk that had been stored in the hollow part flows out from its tip into the gap between the hollow outer tube and the hollow inner tube.
Fill.

Further, the water flows out to the outer periphery of the hollow outer tube through several openings provided in advance at the tip of the outer tube.

After that, lower the ready-made concrete pile or steel pipe pile, which was the inner pile that was being pulled up, to the bottom of the hole, and before the cement milk has hardened, hit the inner pile with a hammer or similar tool to ensure that its tip is firmly attached to the supporting ground. I'll make it like that.

After that, the gap between the hollow outer tube and the hollow inner tube is filled with sand, etc., and finally, the part of the outer periphery of the hollow outer tube above the cavity is filled with cement milk, mortar, etc. A packer is installed at a predetermined position to prevent cement milk from flowing into the cavity, and the cement mill is filled up to the mouth of the outer pipe to integrate the steel pipe with the ground above the cavity.

In the case of the present invention, a packer is attached to the outer periphery before building the outer pile, that is, a hollow outer pipe pile, and since the hollow outer pipe pile with a slit at the tip is driven, this pile is used to fill with mortar. This prevents mortar from being washed away into the cavity.

Therefore, the hemmortal inside the cavity will not be washed away during the pouring of cementing mortar and the filling of mortar around the outer circumference of the hollow outer pipe, which will not affect the water quality of the groundwater aquifer, and the foundation pile will be strong.

The embodiments shown in the drawings will be described below.

Fig. 1 shows the foundation pile completed by the construction method of the present invention, and 111 is a prefabricated concrete pile or the like that becomes a hollow inner pipe pile, which supports the structure (2). It is a steel pipe pile with an outer pipe pile (
4) shows a cavity formed in the ground. (5
) is a pre-bored hole, into which a double structure pile consisting of the inner pile and the outer crushed/pipe pile is built, and the hole (5), the pile (11) and the pile (3) are erected. Lower part of cavity, hole (
The upper parts of the cavities between the piles 5) and the piles (3) are filled with cement milk or mortar (6), and the gaps between the piles +11 and the piles (3) are filled with sand (7). At this time, the packer (8) prevents the cement milk or mortar (6a) from flowing into the cavity (4), and the cement milk or mortar (6b) is opened to fill the outer periphery of the steel pipe (3). A hole (9) is provided. The packer (8) is made of sponge, soft plastic or wood.

Next, the order of construction will be explained.

First, as shown in Figure 2 (a), pre-boring is carried out using a method that does not use circulating mud, such as a down-the-hole hammer or an earth auger (rock auger), and the pre-boring is carried out to a specified depth (supporting ground).
Provide a hole (5) that reaches up to.

Next, the outer steel pipe pile (3) is erected as shown in Figure 2 (b), but at this time, the steel pipe pile (3) has a backer (8
) and an opening (9). After the erection is completed, the hole (
5b) Completely remove the slime at the bottom using a method such as air lift.

After erecting the hollow pipe pile (1) as shown in Figure 2 (c), the cement milk (6) was completely injected into the hollow part of the hollow pipe pile (1+) using a vibrator 0 that reached the bottom of the hole. do.

The cement milk has a cavity (4) as shown in Figure 2).
-1 Inject only the amount that will not be lost.

After the injection is completed, remove the pipe 0, and before the cement milk hardens, pull up only the inner pile (1) several tens of centimeters to 1 Torr from the hole bottom as shown in Figure 2).

By doing this, the cement milk (6b) is attached to the pile (1
) flows out from the bottom of the pile (1) and the steel pipe pile (3), fills the gap between the pile (1) and the steel pipe pile (3), and then flows through the slit (9) to the hole (5b) and the steel pipe (3).
) will also fill in the gaps. Then, before the cement milk (6b) hardens, the hollow pipe pile (1) is returned to its original state as shown in Figure 2 (e), and the Monken aυ
After applying a moderate blow to ensure that the tip of the pile (tl) is completely in contact with the supporting ground, wait for the cement milk (6b) to harden and attach it to the hollow pipe pile +11 as shown in Figure 2 (f). The gap between the hollow pipe pile (3) is filled with sand (7), and finally the pile (
Cement milk or mortar (6a) is filled into the gap between the outer periphery of the hole (3) and the drilled wall (5a).
In order to prevent a) from being washed away into the cavity (4), the stake (3)
Set the backer (8) in the specified position.

As described above, according to the method of the present invention, it is possible to prevent the subsidence and collapse of the ground above the cavity without causing pollution in the ground where there is a cavity, and it is possible to construct foundation piles that reliably support the structure. It can be done.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a foundation pile according to the construction method of the present invention. FIGS. (1) Hollow inner pipe piles (ready-made concrete piles, steel pipe piles, etc.) (
2) Structure (3) Hollow pipe pile (1 pipe pile) (4) Cavity (5) Hole by pre-boring (6) Cement milk or mortar (7) Sand (8) Backer (9) Slit 0 [Injection pipe ( 1υ Monken Patent Applicant Aoki Construction Co., Ltd. Figure 1 Figure 2 (A) (B) Figure 2 (M) (D) 2nd (E) (F)

Claims (1)

[Claims] If there is a cavity or an extremely permeable layer in the ground where the foundation pile is to be erected, first drill a hole to the solid stratum below the cavity or extremely permeable layer, and then build into the hole. A hollow outer tube with a slit at the tip and a packer attached to the outer periphery is installed in the middle so that the position is directly above the top of the cavity or a layer with extremely high water permeability, and a hollow inner tube is installed inside this hollow outer tube. The mortar is injected into the inside of the hollow inner pipe and overflows from the lower end opening, and the mortar is passed through the slit in the outer pipe to the outside of the hollow outer pipe to perform foot protection, and then from the top of the outer pipe. A construction method for foundation piles in which mortar is filled in the gap between the outer pipe and the hole wall to prevent the mortar from overflowing from the packer onward toward the cavity or an extremely permeable layer.