JPS6319645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for burying ready-made piles in underground trenches without noise or vibration, and is primarily aimed at increasing the pile supporting capacity.

Various proposals have been made in the past regarding so-called pollution-free construction methods for ready-made piles.

Applicants have already developed a method of hollow construction in which an earth auger with a bit is inserted into the hollow part of the pile, and the pile is sunk to a predetermined depth in the ground, and then the earth auger is pulled out. An injection pipe rod with a high-pressure jet nozzle is also inserted into the hollow part, and after the rod reaches the tip of the pile, high-pressure jets of water, etc. are sprayed while rotating the rod until it reaches a predetermined depth, and then it is immediately poured into the ground. We have proposed a method for burying ready-made hollow piles (Japanese Unexamined Patent Publication No. 39906/1973), which is characterized by forming a supporting hardened layer at the tip by injecting hardening agent at high pressure and pulling up the rod while rotating. ing.

In these construction methods, the ground is drilled with an earth auger, and the soil is forced into the pile using hydraulic pressure while being discharged from the top through the hollow part of the pile. A frixion cutter is attached for cutting purposes.
(See Figure 1) This makes construction easier, but
On the other hand, even with piles whose construction was completed in the future, there was a problem in that the friction on the circumferential surface did not recover easily.

On the other hand, at the tip of the pile, a strong supporting hardened layer was formed by the above-mentioned invention, so sufficient supporting force could be expected.

This invention eliminates these imbalances and provides a method for embedding piles that exhibits a rational support function.

This will be explained below based on the drawings.

FIG. 2 shows a cross-sectional view of the hollow ready-made pile 1 used in the present invention, which consists of a linear non-expanded portion A, a tapered portion B formed near the tip, and an enlarged portion C at the tip. This ready-made pile 1 can be manufactured using centrifugal molding or the like.

The enlarged part C plays the role of a friction cutter in conventional construction methods, and the inside of the enlarged part C is also tapered to facilitate medium excavation construction. All parts have a constant inner diameter except for this inner tapered part.

In this ready-made pile 1, when the outer diameter _D1 of the non-expanded part A is 500 mm, the outer diameter _D2 of the enlarged part C is about 550 to 600 mm. In addition, the conventional friction cutter is 12
~19mm thicker, and diameter is 524~538 compared to 500mm
mm, but in this invention it is made larger than this. As a result, the capacity of the tip is 550
The same effect as driving ~600mm piles can be expected. That is, the enlarged portion C serves to receive the support hardening layer 6 (see FIG. 7) formed near the enlarged portion C, but the enlarged portion also increases the support cross-sectional area.

On the other hand, due to the formation of this enlarged portion C, the gap with the surrounding earth and sand becomes larger than in the case of a conventional friction cutter, making it even more difficult to restore the frictional force.

Therefore, in the present invention, construction is carried out by placing at least one column pipe 2 along the non-expanded portion A of the outer peripheral surface of the ready-made pile 1. In the above example, if the outside diameter D ₁ of the non-expanded part is 500 mm and the outside diameter D ₂ of the expanded part C is 550 mm, this injection pipe 2 should have an outside diameter within 25 mm, and the outside diameter of the expanded part C should be 550 mm. D Do not go outside beyond ₂ .

3 to 7 show an example of the construction procedure of the burying method of the present invention using this ready-made pile 1.

First, as shown in FIG. 3, the auger 3 is inserted into the hollow part of the ready-made pile 1, and the ready-made pile 1 is sunk to a predetermined depth while drilling into the ground, similar to the conventional hollow excavation method. Further, the injection pipe 2 is attached in advance to the outer peripheral surface of the non-expanded portion A of the ready-made pile 1 along the longitudinal direction.

In addition, as shown in Fig. 4, an injection pipe 2 is inserted into the gap between the surrounding ground and the ready-made pile 1 created by the enlarged portion C.
The gap is filled with mortar such as cement milk or other hardening material 4. Note that the work of filling the hardening material 4 may be performed while the ready-made pile 1 is being sunk during the construction of the medium excavation, or may be performed after the ready-made pile 1 has been sunk to a predetermined depth.

In cases where the ground is not likely to collapse, such as in viscous soil, this injection pipe 2 will leave gaps and the hardening material 1 will be able to cover the entire area even with a small number of pipes, but in cases where collapse is expected, such as in sandy soil, multiple injection pipes may be used. You will need a book. Note that this injection pipe 2 may be recovered after injection.

After this, in order to form a hardened support layer 6 at the tip of the buried ready-made pile 1, a hardening material can be injected at high pressure using an injection pipe rod 5 inserted into the hollow part of the ready-made pile 1, or an auger can be used as an auxiliary method. There is a method of creating a strong supporting ground by installing expanding blades on the ground and mechanically stirring and mixing the supporting ground and hardening material.

Figures 5 to 7 show the former method.
First, as shown in FIG. 5, after the auger 3 is pulled out, the injection pipe rod 5 is inserted. Next, while rotating the rod 5, water is jetted at high pressure from the high-pressure jet nozzle at the tip to preliminarily excavate the supporting ground, and the rod 5 is inserted to a predetermined depth.

Subsequently, as shown in FIG. 6, the rod 5 is pulled up while being rotated and curable material is injected by high-pressure injection. FIG. 7 shows the completed state of the ready-made pile 1. A hardened support layer 6 is formed at the tip of the ready-made pile 1, and the surrounding surface is also made of hardened material 4.
Because it is filled with
It has a large supporting capacity as a whole.

The following method can also be considered as a way of thinking about peripheral surface friction. In other words, in areas where alluvial ground continues for a long time, as a countermeasure against negative friction that may occur due to future ground subsidence, it is considered to apply a bituminous agent to the circumferential surface of the pile to reduce the circumferential friction from the beginning. Methods have been proposed, but according to this method, the area to be injected onto the circumferential surface is controlled, and by not injecting into areas where such negative friction countermeasures are required, it is possible to reduce the circumferential friction.
By injecting only the lower part of the pile that is not affected by negative friction, it is possible to consider countermeasures against ground subsidence. FIG. 8 shows an example in that case.
The curable material 4 is not injected into the range l ₁ affected by negative friction, but is injected only into the range l ₂ where it is not affected. When the pile length is L, l ₁ ≒
It is thought to be about 0.8L, l ₂ ≒ 0.2L.

The present invention has the above configuration and has the following advantages and features.

(1) The enlarged part at the tip of the ready-made hollow pile acts as a friction cutter, making it easy to perform medium excavation construction.

(2) Since the support cross-sectional area of the enlarged part is large, the tip support force is large.

(3) Instead of creating a larger gap due to the enlarged section than in the case of conventional friction cutters, the hardening material is filled by the injection pipe along the non-enlarged section of the prefabricated pile, so there is sufficient circumferential friction. You can expect power. In addition, the injection pipe is attached in advance to the outer circumferential surface of the ready-made pile, and fits into the gap between it and the surrounding ground created by the enlarged portion, making it possible to fill the hardenable material even if the gap is narrow.

(4) This method can be used in conjunction with a construction method in which a strong hardened support layer is placed at the tip of a ready-made pile to balance the bearing capacity at the tip and the bearing capacity due to circumferential friction, resulting in highly reliable buried piles.

(5) By injecting hardenable material only at the tip of the outer circumferential surface of the ready-made pile, negative friction can be countered.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional example, Figure 2 is a sectional view of a ready-made hollow pile used in the construction method of the present invention, Figures 3 to 7 are sectional views showing the construction procedure, and Figure 8 is another example. FIG. 3 is an example cross-sectional view. a... ready-made pile, b... auger, c... friction cutter, 1... ready-made pile, 2... injection pipe, 3... auger, 4... curable material, 5... injection pipe rod, 6
...Supporting hardened layer, S...Supporting ground surface.

Claims (1)

[Claims] 1. An earth auger is inserted into the hollow part of a ready-made hollow pile that has an enlarged part at the tip and an injection pipe is installed longitudinally along the outer circumferential surface of the non-expanded part to ground the ground. of the ready-made hollow pile, which is characterized by drilling a hole, sinking the ready-made hollow pile to a predetermined depth, and injecting a hardening material from the injection pipe to fill the gap between the outer peripheral surface of the ready-made hollow pile and the surrounding ground. Medium excavation method. 2 The gap between the outer peripheral surface of a ready-made hollow pile and the surrounding ground is filled with a hardening material only in an area from the tip of the pile to a depth of about 0.2 times the total length of the pile.Claim 1
The method of burying ready-made piles in a hollow hole as described in Section 1.