JPS6146610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foundation pile erection method.

Generally, when a structure is constructed directly in a place where there is a cavity directly under the ground, the ground will collapse or subside.
The structure is at risk of being destroyed.

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

(b) 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 material flowing out of the intended filling area.

Therefore, in such cases, as a reliable construction method, it is better to find a support layer in the ground deeper than the cavity and use a construction method that supports the structure with foundation piles. The same is true.

The present invention was created to carry out the above construction method, and has a double structure pile, that is, a hollow outer pipe pile on the outside.
By using hollow inner pipe piles such as ready-made concrete piles, steel pipe piles, or cast-in-place piles on the inside, it is possible to carry out construction under such ground conditions, and the load of the structure is borne by the inside piles. However, the friction force generated due to natural or sudden collapse was made to act on the outer pipe pile on the outside.

The construction method for hollow outer pipe piles is the pre-boring method, but the method that uses a stabilizing liquid such as muddy water for drilling holes is difficult because the muddy water is completely washed away due to the existence of cavities. 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 dry drilling using a down-the-hole hammer, an earth 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 is dug 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 or steel pipe piles or cast-in-place piles as the inner piles. If the inner piles are ready-made 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 stored in the hollow part flows out from its tip and fills the gap between the hollow outer tube and the hollow inner tube.

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, the ready-made concrete pile or steel pipe pile, which was the inner pile that had been pulled up, is lowered to the bottom of the hole, and before the cement milk has hardened, the inner pile is struck with a hammer etc. to ensure that its tip lands firmly on the supporting ground. do as you like.

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 the cement milk from flowing into the cavity, and the cement milk is filled up to the mouth of the outer pipe to integrate the steel pipe with the ground above the cavity.

According to the present invention, before erecting the outer pile, that is, the hollow outer pipe pile, a packer is attached to the outer periphery, and in order to drive the hollow outer pipe pile having a slit at the tip, this pile is used to fill with mortar. This prevents mortar from being washed away into the cavity.

Therefore, the mortar does not flow into the cavity during the pouring of foot protection mortar and the filling of mortar around the outer circumference of the hollow outer pipe, which does not affect the water quality of the groundwater aquifer, and a strong foundation pile can be obtained. be.

The embodiments shown in the drawings will be described below.

FIG. 1 shows a foundation pile completed by the construction method of the present invention, in which 1 is a ready-made concrete pile or the like that becomes a hollow inner pipe pile, and supports a structure 2. 3 is a steel pipe pile with a hollow outer pipe pile, and 4 is a hollow formed in the ground. Reference numeral 5 is a pre-bored hole, into which a double structure pile consisting of the inner pile and outer steel pipe pile is built, and the hole 5, the hollow lower part of pile 1 and pile 3, and the hole 5
The upper part of the cavity of the piles 3 is filled with cement milk or mortar 6, and the gap between the piles 1 and 3 is filled with sand 7. At this time, a packer 8 prevents the cement milk or mortar 6a from flowing into the cavity 4, and an opening 9 is provided in order to fill the outer periphery of the steel pipe 3 with the cement milk or mortar 6b. The packer 8 is made of sponge, soft plastic or wood.

Next, the order of construction will be explained.

First, as shown in Figure 2A, pre-boring is performed using a method that does not use circulating mud, such as a down-the-hole hammer or an earth auger, to form a hole 5 that reaches a predetermined depth (supporting ground). Next, the outer steel pipe pile 3 is erected as shown in FIG. After the construction is completed, the slime at the bottom of the hole 5b is completely removed by a method such as an air lift.

After erecting the hollow inner pipe pile 1 as shown in FIG. 2C, cement milk 6 is injected into the hollow part of the hollow inner pipe pile 1 through a pipe 10 reaching the bottom of the hole. Cement milk is injected into the cavity 4 in an amount that does not flow away as shown in FIG. 2D.

After the injection is completed, remove the pipe 10 and insert the inner pile 1 as shown in Figure 2 D before the cement milk hardens.
The chisel is pulled up several tens of centimeters from the bottom of the hole.
By doing this, the cement milk 6b is attached to the pile 1.
It flows out from the bottom end and fills the gap between pile 1 and steel pipe pile 3.
Furthermore, the gap between the hole 5b and the steel pipe 3 is also filled through the slit 9. and cement milk 6
Before b has hardened, return the hollow inner pipe pile 1 to its original state as shown in Figure 2 e, and give it a moderate blow with the Monken 11 so that the tip of the pile 1 is in complete contact with the supporting ground. After that, after waiting for the cement milk 6b to harden, the gap between the hollow inner pipe pile 1 and the hollow outer pipe pile 3 is filled with sand 7 as shown in Fig. 2, and finally the outer periphery of the pile 3 and the drilled wall 5a are filled. Cement milk or mortar 6a is filled into the gap between the piles 3 and 3. At this time, a packer 8 is set at a predetermined position on the pile 3 in order to prevent the filling material 6a from flowing into the cavity 4.

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 method of the present invention. FIG. 1... Hollow inner pipe pile (ready-made concrete pile, steel pipe pile, etc.), 2... Structure, 3... Hollow outer pipe pile (steel pipe pile), 4... Hollow, 5... Hole by pre-boring, 6... Cement milk or mortar, 7...
Suna, 8...Patzka, 9...Slit, 10...
Injection pipe, 11...Monken.

Claims (1)

[Claims] 1. When there is a cavity or an extremely permeable layer in the ground where the foundation pile is to be erected, a hole is first drilled to the solid stratum below the cavity or an extremely permeable layer, and then the foundation pile is built 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 an extremely permeable layer. The pipe is erected, mortar is injected into 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 for foot hardening, and then the top of the outer pipe is poured. A method for constructing foundation piles in which mortar is filled in the gap between the outer pipe and the hole wall to prevent mortar from overflowing from the packer onward toward the cavity or an extremely permeable layer.