JPS63277319A - Setting of friction pile - Google Patents

Abstract

PURPOSE:To increase the bearing force of pile by a method in which a partially bound bag is set in the ground, and a filler is packed under pressure into the bag and hardened to form a pile whose unbound portions are buried in the surrounding ground. CONSTITUTION:A bag 16 with bound portions formed at an adequate interval by bands 14 is inserted into a steel casing pipe 12, and a cone 16 is fixed to the bottom of the bag 16. The pipe 12 with the bag 16 is driven into the ground 18 and the pipe 12 alone is drawn out. Cement mortar 22 is injected into the bag 16 to expand the portions not bound with bands 14 and hardened under a condition that it is deformed so as to allow it to penetrate into the ground. The surrounding ground can thus be consolidated by the expansion of the unbound portions to increase the strength of the ground, and the contact area between the pile and the ground can also be increased. The resistance force against the settlement can also be increased, and therefore, the bearing force of the pile can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to driving friction piles suitable for foundations when constructing civil engineering and building structures on soft ground such as clayey soil layers and peat layers. Regarding the construction method, in more detail, a locally tied bag-like body is placed in the ground, and a filling material such as mortar is press-fitted into the bag-like body so that it bulges and pushes into the surrounding ground to provide large support. This relates to a method for driving friction piles that obtain force.

[Prior Art] Pile foundations are generally used as foundations when constructing civil engineering and architectural structures.

Piles can be broadly classified into tip support piles and friction piles. Tip-supported piles are piles whose tips reach layers with sufficient bearing capacity, such as bedrock or hard gravel layers, and most of the load supported by the pile is transferred from the pile tips to these layers. Friction piles, on the other hand, are driven into sand, silt, or cohesive soil layers, and their tips do not reach the supporting layer, and the load is transmitted into the ground due to the friction between the pile and the surrounding soil.

[Problems to be Solved by the Invention] Driving tip support piles is the most reliable method, but if the support layer is deep, problems such as technical difficulties and economical burdens arise. For this reason, friction piles are often used.

However, when the ground is soft and the frictional force is small, such as in a cohesive soil layer or a peat layer, ordinary friction piles may have a small pile bearing capacity, making it impossible to construct a pile foundation.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a method for driving friction piles that can obtain a large bearing capacity even in soft ground where it is difficult to obtain a friction force using the prior art, and that can be easily constructed. The purpose is to provide a method.

[Means for solving the problem] The frictional force between the ground and the piles is determined not only by the characteristics of the ground, but also by the combination of the ground and the piles. Therefore, it is possible to increase the frictional force by changing the shape and structure of the pile, even in extremely soft ground such as a peat layer, where conventional piles could not provide sufficient frictional force. However, a pile that exerts a large amount of frictional force naturally requires a large amount of force to be driven into the pile. Forcibly driving a pile may disturb the surrounding soil and cause a loss of frictional bearing capacity, or it may become impossible to drive the pile itself.

The present invention is a method devised to avoid such unreasonableness, facilitate pouring, and obtain a large supporting force.

That is, in the present invention, a locally tied bag-like body is placed in the ground, and a filling material such as mortar or concrete is press-fitted into the bag-like body so that it bulges and pushes into the surrounding ground. This is a method of driving friction piles that harden.

Here, "locally bound" refers to a state in which the part cannot bulge freely unlike other parts, in other words, a state in which the bulge can be restrained to some extent.

As a method for positioning the bag-like body in the ground, for example, there is a method of driving a casing pipe containing the bag-like body into the ground, and then removing the casing pipe leaving the bag-like body behind. Another method is to drill a hole in the ground in advance and insert the bag-like body into the hole, or insert the bag-like body into a rod-shaped or plate-shaped pushing member without forming a hole in the ground in advance. It is also possible to hold it along, push it in as it is, and pull out only the pushing member. Especially if you use these methods,
Depending on the shape of the bag, it is also possible to drive wall-shaped (flat or curved, etc.) friction piles.

[Function] When a filling material such as mortar is press-fitted into the inside of the bag-like body located in the ground, the unbound part of the bag-like body swells, deforms so as to press into the surrounding ground, and then hardens as it is.

Inserting the bag into the ground is a simple process. However, since the cough pouch-like body then expands and pushes into the surrounding ground, the ground is rarely disturbed. The expansion and deformation of the pile consolidates the ground around the pile, increasing the ground strength in that area, strengthening the adhesion between the pile circumferential surface and the contact surface, and increasing the contact area, resulting in a large frictional bearing capacity.

Since the piles driven by the present invention have a locally bulging shape, in addition to the above-mentioned consolidation effect, the bulging portion is also supported from below, further increasing the supporting capacity of the pile. .

Therefore, the friction pile according to the present invention is extremely effective in that it can be constructed even on extremely soft ground, which has been extremely difficult in the past.

[Example 1] Fig. 1 is a process explanatory diagram showing an example of the method for driving a friction pile according to the present invention. In this embodiment, a hole is formed in the ground using an iron casing pipe, and a bag-like body is inserted at the same time.

First, as shown in Figure A, a removable cone portion 1 is attached to the tip.
An iron casing pipe 12 equipped with 0 is prepared, and a bag-like body 16 made of strong cloth or the like is attached to an elongated band 14 at an appropriate interval in the middle to prevent local expansion. Insert. The bottom of the bag-like body 16 is fixed to the cone part 10. Such a casing pipe 12 is driven into a predetermined position in the ground 18 by a known method.

Next, as shown in Figure B, the casing pipe 12 is removed from the cone portion 1o and only the casing pipe 12 is pulled out. As a result, the bag-like body 16 is placed in the hole 20.

Next, as shown in Figure C, mortar 22 is press-fitted into the upper part of the bag-like body 16. In extremely soft ground, the weight of the piles may become a problem, so in such cases, foam mortar containing aluminum powder or lightweight mortar using lightweight aggregate may be press-fitted. When the mortar 22 is press-fitted, the portion bound by the band 14 is not deformed, but the other unbound portion is expanded by the press-fitted mortar and deformed so as to push into the surrounding ground. The amount of deformation can be controlled by the amount of mortar press-fitted. If the material is cured under pressure, a complex-shaped friction pile can be formed as shown in FIG.

In this way, the surrounding ground is consolidated due to the bulge,
The ground strength increases, the pile bearing capacity increases, and unlike simple stick-shaped piles with a constant cross-sectional shape, the contact area with the surrounding ground increases, and the resistance to subsidence increases, making it possible to support large loads. .

In the above embodiment, the iron casing pipe 12 is used to be driven directly into the ground, but it is also possible to drill a hole in advance with an excavator and insert the bag 14 into the hole. .

However, if the ground is weak (the hole wall easily collapses), it is advantageous to use a method of driving using a casing pipe as shown in the above embodiment.

FIGS. 2 and 3 are explanatory diagrams showing other embodiments of the present invention. Here, a method is adopted in which a bag-like body is inserted into a hole previously formed in the ground. In this embodiment, a planar bag-like body 24 is employed. A plurality of binding fittings 26 are alternately provided at appropriate locations on the bag-like body 24 so as to be at different levels, and the bag-like body 24 is restrained at such locations so that the distance between both sides of the bag-like body 24 does not widen.

Such a bag-like body 24 is extremely convenient when, for example, an open channel or a culvert is passed through extremely soft ground.

A plan view in that case is shown in FIG. A slot having a long width in a direction perpendicular to the installation route of the open channel 30 etc. is formed, and the bag-like body 24 is inserted into it.

Mortar or the like is then press-fitted so that the unbound portion bulges out and presses into the surrounding ground. In this way, friction piles 32 may be formed at appropriate intervals, and open drains 30, underdrains, etc. may be constructed on top of the friction piles 32.

The formation position, number, and shape of the binding parts formed on the bag-like body can be changed as appropriate depending on the ground conditions. For example, in the case of a pillar-shaped bag, the bag-like body is made of strong material such as cloth or sheet. It can be made into a thick cylindrical shape and tied locally with a band, or it can have a structure with pleats so that the untied part can expand, or even a structure where the weave of the cloth is loose to some extent. The bag may be made of a material that is itself deformable, such as rubber. If the bag itself is made of a material with high strength, the bending strength can be increased.

As an example of local binding, in addition to using the above-mentioned band or metal fittings, depending on the material of the bag-like body, it may be possible to sew a certain area together, or fix by thermal welding or adhesive.

In addition, to ensure verticality and straightness in the ground, reinforcing materials such as reinforcing bars, iron pipes, or plastic pipes can be inserted inside the bag, and then mortar or concrete can be press-fitted. .

If the distance between the upper and lower bulges is narrow, it is equivalent to increasing the effective diameter of the pile, and the friction surface due to consolidation is expanded to support the pile. “The force that directly supports the bulge from below has a big influence.In any case, the relatively small amount of mortar
It is possible to develop a large supporting capacity.

In order to position the bag-like body 16.24 in the ground 18, an iron casing pipe may be used as in each of the above embodiments, a hole may be drilled in advance and inserted, or a hole may be inserted into the hole. As shown in Fig. 4, the bag 16.24 is held along the tip of a rod-shaped or plate-shaped pushing member 40 corresponding to the shape of the bag 16. 18 and then only the pushing member 40 is pulled out.

If necessary, the interior of the bag 16.24 can also contain reinforcing material as described above.

[Effects of the Invention] As described above, the present invention has a friction material that is made to bulge and push into the surrounding ground by press-fitting a filler such as mortar into the inside of a locally bound bag-like body located in the ground. Since this is a pile driving method, the bulge consolidates the ground around the pile, increasing the ground strength in that area, strengthening the adhesion between the pile surrounding surface and the contact surface, and increasing the contact area. Therefore, the supporting capacity of the piles becomes extremely large. In addition, because only the unbound portion of the bag-like body bulges out, a large frictional force can be obtained between it and the ground, unlike conventional simple rod-shaped piles. These effects make it possible to develop a sufficiently large bearing capacity, making it possible to construct pile foundations and build civil engineering and architectural structures on top of them, even in extremely soft ground such as peat layers, which was difficult with conventional construction methods. This has the effect of making it possible to construct.

In addition, in the present invention, even when drilling a hole in the ground, the cross-sectional area is small and the excavation volume is small, making it extremely economical. It is made of concrete, etc., and unlike pouring it all over, it swells only locally, so the amount of mortar used can be saved, and it is also economical.

Furthermore, since it has a large degree of freedom and can easily be configured not only in columnar shapes but also in wall-shaped (planar) friction piles, it is possible to construct pile foundations suitable for superstructures, and the surrounding ground can be improved at the same time due to the consolidation effect. There are also other advantages.

[Brief explanation of drawings]

111mA, B, and C are process explanatory drawings showing one embodiment of the friction pile driving method according to the present invention, Fig. 2 is an explanatory drawing showing another example of the bag-like body used in the present invention, and Fig. 3 The figure is a plan view showing an example of construction of a pile foundation using the same, and FIG. 4 is an explanatory diagram showing another example of inserting the bag-like body into the ground. 12...Casing vibe, 14...Band, 16
．． 24... Bag-like body, 18... Ground, 20... Hole,
22...Mortar, 26...Binding fittings. Patent Applicant: Oyoyo Geological Co., Ltd., Director Shigeru Minoru Figure 1 A B C Figure 3

Claims (1)

[Claims] 1. Friction characterized by placing a locally tied bag-like body in the ground, press-fitting a filler into the inside of the bag-like body, causing it to swell and push into the surrounding ground, and allowing it to harden as it is. How to drive piles.