JPH02232416A - Foundation pile structure - Google Patents

Abstract

PURPOSE:To make it possible to construct a foundation pile having bearing power suitable to differences of soil layers by driving knotted concrete piles, superior in peripheral surface bearing power, into the lower layer of the soil and a cylindrical pile, having large flexural strength, into the upper layer, and by connecting both piles each other. CONSTITUTION:A knotted pile F is driven in to the ground with a diesel pile hammer 10 or the like and when deep driving is required, extension is made with additional knotted piles F1 driven in and connected thereon. Then a cylindrical pile P is driven in, being connected to the knotted pile with an end connector 4. Void spaces around the piles, created by driving in of knotted parts 2 of the knotted piles F, are then filled with filling materials such as gravels 11, sand or crushed stones. As excessive pore water pressure on an occasion of earthquake can be dissipated by drainage effect of the filling materials, construction of strong foundation piles can be made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a foundation pile structure that supports two above-ground structures.

[Conventional technology and problems to be solved] Conventionally, J1 at the bottom of structures has been used as foundation piles! Within the I panel, multiple ready-made concrete piles or steel pipe piles are connected and cast to a predetermined depth to support the superstructure 2! There is a method to create a foundation shaft.

When designing and constructing such foundation piles, the load of the superstructure and the horizontal force acting on the structure are generally considered, and a pile suitable for the ground is selected and used. In construction sites, piles of the same type were connected together, and foundation piles were never created by connecting different types of piles with different pile performance in the length direction of the piles. .

For example, when actually cast into the ground, the following cylindrical piles are available as ready-made piles that have a large horizontal bearing capacity, although they cannot be expected to have a large circumferential bearing capacity.・Cylindrical bristless concrete piles, high-strength bristless concrete piles, etc. Concrete piles (PC pile, PHC pile) ・Composite pile (M-tube concrete composite pile) ・Steel pipe pileAlso, although we cannot expect much horizontal bearing capacity, knotted concrete piles etc. There are friction piles, but as mentioned above, piles with different performances have never been properly connected and driven according to the properties of the ground to form foundation piles that support structures.

In particular, in addition to axial force and bending moment, a foundation pile actually driven into the ground is subject to negative frictional force depending on the ground, and there is also a risk of liquefaction in the ground during an earthquake. There are different types of soil, and therefore it is desirable to build foundation piles that are optimal and most economical for each of these types of foundation piles. However, in the conventional method of connecting and driving certain types of piles, the foundation piles mentioned above are constructed. That is completely impossible.

For example, in the ground shown in Figure 11, the upper layer A of the ground is a soft and viscous consolidated ground, and the lower layer B is the ground with a large Nlii and is expected to have a circumferential surface bearing capacity and a tip bearing capacity. Assume that the horizontal force and bending moment acting on the

In such a ground, if a cylindrical pile (P) such as a PHC pile or a steel pipe pile with a large horizontal bearing capacity is used as a foundation pile for the entire length of the pile as shown in the figure, taking into account the bending moment etc., the lower layer B soil This results in insufficient peripheral support force.

Furthermore, if the vertical bearing capacity of the above-mentioned ground is taken into account, and if a foundation pile is made of a knotted concrete pile with a large circumferential bearing capacity for the entire length of the pile, the horizontal bearing capacity of the upper layer A of the ground will be insufficient. Furthermore, because the peripheral support force is large, when the upper layer A of the ground consolidates and settles, a negative frictional force acts on the upper part of the antibody, and as a result, the antibody bears the axial force due to the negative frictional force in addition to the axial force due to the structure load. I will do it.

Therefore, in the past, foundation piles were constructed using extremely uneconomical methods such as increasing the diameter of the same type of pile, increasing the length of the pile, or increasing the number of piles.

In view of the above, the present invention has been made to create a safe and economical foundation pile that has a supporting capacity that is compatible with the properties of the ground.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention installs cylindrical bristless concrete piles, steel pipe piles, etc., which have a large bending capacity, in the upper ground where a relatively large horizontal capacity is required. Instead of using cylindrical piles, we decided to use knotted concrete piles with excellent circumferential bearing capacity in the underlying ground where vertical bearing capacity such as circumferential bearing capacity can be expected.

In other words, the foundation pile structure of the present invention has a horizontal R that moves in the structure.
A ready-made cylindrical pile is placed above the heavily supported foundation pile, a ready-made knotted concrete pile is placed below this pile, and these two piles are connected and driven into the ground.

In the above, the diameter of the cylindrical pile may be approximately the same as the body diameter of the knotted concrete pile, or may be larger than the body diameter of the knotted concrete pile.

It is also desirable to fill the outer periphery of the ready-made cylindrical pile at the top of the foundation pile with filler such as sand, gravel, crushed stone, etc.

[For production]

According to the foundation pile of the present invention having the above configuration, in the upper ground where a relatively large bending moment acts, a cylindrical pile with a large bending capacity is used, so the horizontal load acting on the upper structure is transferred to the cylindrical pile. It can be adequately supported by piles. Moreover, this cylindrical pile has a smaller circumferential frictional support force than a knotted concrete pile.
Even if the upper ground is soft and viscous and may undergo consolidation and subsidence, no negative frictional force will be generated.

In addition, in the lower ground, knotted concrete piles with high circumferential bearing capacity are used, so even if the trunk has the same diameter as the cylindrical pile, the tip bearing capacity will also increase due to the larger diameter tip joint. This, together with the increase in the circumferential support force due to the joints, makes it possible to obtain a sufficient vertical support force without any shortage.

Furthermore, if the outer circumference of the cylindrical pile is filled with filler such as sand, gravel, or crushed stone, the surrounding ground will be compacted and the horizontal bearing capacity will increase. It also acts as a drain.

[Example] Next, embodiments of the present invention will be described based on the drawings.

In the figure, (P) indicates a ready-made cylindrical pile used in the upper ground, and (F) indicates a ready-made knotted concrete pile (hereinafter referred to as "knotted pile") used below the cylindrical pile. The required number of knotted piles (P) and knotted piles (P) are connected and driven into the ground as shown in Fig. 1 according to the ground properties, required pile bearing capacity, etc. Foundation piles are constructed. Cylindrical pile (
The connection between P) and the knotted pile (F) is performed as follows.

The embodiment shown in FIG. 2 shows an embodiment in which the diameter of the trunk (3) of the knotted pile (F) and the diameter of the cylindrical pile (P) are the same. At the ends of the cylindrical pile (P) and the knotted pile (P), there are end plates (4a) as shown in Figure 3.
) and a side plate (4b) are fixed to the end fitting (4), and the main reinforcement (5) inside the pile is fixed to this end fitting (4).
The ends of are attached. The piles (P) (F) are connected by welding the end fittings (4) (4) together.

Figure 4 shows the inside of the head of the upper part of the knotted pile (1?) in order to increase the bending strength at the joint of the jointed pile (F) connected to the lower part in the embodiment shown in Figure 2 above. 2 shows a case in which a reinforcing bar (5a) is provided separately from the main pile bar, which is particularly effective when the bending strength of the upper and lower piles to be connected differs greatly.

FIG. 5 shows an embodiment in which the cylindrical pile (P) has a pile diameter that is approximately the same or larger than the diameter of the knots (2) of the knotted pile (P). In this case, the upper and lower cylindrical piles (P) and knotted piles (F) are connected by a tapered joint vibe (T) as shown in the figure, and this joint vibe (T) has a cylindrical top. Pile (P
), and a tapered vibrator whose lower part has the same diameter as the trunk (3) with a joint (F) is used. Especially the thickness of the vibe,
The bending strength of the cylindrical vibrator (P) is comparable to or greater than that of the cylindrical vibrator (P).

In this example, the cylindrical pile (P) will be the upper part of the foundation pile.
Since the diameter is larger than the diameter of the body (3) of the knotted pile (P), the bending strength increases and the axial compressive strength also increases.

In each of the above embodiments, the cylindrical pile (P) connected to the upper part includes a cylindrical concrete pile (PC pile, PHC pile, etc.), a composite pile (steel pipe concrete composite pile), a steel pipe pile ( 6), etc., and should be used appropriately depending on the vertical bearing capacity, horizontal bearing capacity, ground properties, differences in construction method, etc. of the piles supporting the structure.

In addition, since the bending moment mainly acts on the upper part of the pile near the ground on the foundation pile, the cylindrical pile (P) at the upper part of the pile that is connected as described above is a knotted pile (P).
It is desirable to use piles that have a higher bending strength than the above.

Furthermore, when using a steel pipe pile (6) as the cylindrical pile (P), a ribbed steel pipe pile (not shown) with striped ribs on the inner and outer surfaces of the steel pipe is used to meet the required pile performance. Alternatively, as shown in FIG. 6, a T-tube vile (6) having a plurality of water permeation holes <7) provided on the steel pipe wall surface can be used. As described later, the steel pipe pile (8) provided with the permeable holes (7) is particularly effective as a foundation pile for preventing the ground from liquefying in the event of an earthquake, when the upper layer is sandy ground.

When the length of the pile to be driven is long and multiple piles, for example four piles, are connected and driven, only the top one is used as a cylindrical pile (P), and the three piles below it are used as a cylindrical pile (P). Use knotted pile (F), or use cylindrical pile (P) for the upper two piles.
) and the lower two piles are knotted piles (P), or the upper three piles are cylindrical piles (P) and only the lowest part is knotted pile (F).
), and the ground, horizontal bearing capacity, and vertical bearing capacity R
An appropriate one may be used.

A method for constructing the foundation pile of the present invention with the above-mentioned connection structure in the ground will be explained below.

First, in order to use the driving method, as shown in Figure 7,
A knotted pile (P) is erected on a predetermined ground and hammered with a diesel hammer (10) or the like to drive it into the ground.

In this case, as the knotted bale (P) penetrates, gravel (11) or the like is filled from the circumferential wall [see figure (a)]. If the length of the knotted pile to be installed is long, add a knotted pile (F1).
) and type in the same way.

Next, the cylindrical pile (P) is added to the end fitting (4) by welding or other means, but at this time, the anti-circumferential gap created by driving the knots (2) of the knotted pile (P) is is filled with filler such as gravel (H) or sand [see the same figure (
b)]. Moreover, after driving a predetermined length, the upper part of the inner hole of the cylindrical pile (P) or the like may be filled with sand, gravel, etc. for the purpose of increasing the horizontal strength of the pile.

In addition, when gravel, crushed stone, etc. are used as a filler, the drainage effect of the filled gravel becomes effective in dissipating excess pore water pressure during an earthquake, and the upper cylindrical pile (P
), if a steel pipe pile (6) with permeable holes (7) is used, the filled part with gravel, etc. inside and outside the trench will be filled with permeable holes (7).
Because they are connected to each other, the drain effect of packed gravel, etc. is further increased, which is effective in dissipating excess pore water pressure during earthquakes, and is effective in preventing ground liquefaction.

If the cylindrical pile (P) portion is long, additional cylindrical piles (P) may be added and driven in the same manner as described above.

Based on the above, cylindrical pile (P) is used for the upper ground,
Foundation piles using knotted piles (P) are constructed in the ground below this [Figure (C)].

To install the above foundation pile using a low-noise pre-drilling method such as the cement milk method, proceed as follows.

As shown in FIG. 8(a), a screw auger (1.
2) etc., a hole is dug into the ground to a predetermined depth with a diameter slightly larger than the diameter of the knot (2) of the knotted pile (P). When pulling up this screw auger (12),
Fill with a hardening liquid (M) such as cement milk or mortar.

This hardening liquid (M), such as milk, has a high strength around the knotted pile (F) and the hardening part at the tip [part (M1) in Figure 9], and around the cylindrical pile (P). It is also possible to change the composition in the depth direction of the pile, such as by filling the (M2) part with a liquid with low strength. It is desirable to use a filling liquid that can provide high strength in areas where vertical bearing capacity of the pile is expected.

In this way, the knotted pile (P) is suspended and press-fitted into the borehole (K). At this time, a predetermined number of knotted piles (F) are added. Next, add a cylindrical pile (P) and hang it in the hole (K) and press it in the same way as above.

As a result, foundation piles using cylindrical piles (P) in the upper ground and knotted piles (P) in the ground below are built into the ground.

The periphery of the cylindrical pile (P) may be filled with sand (13), gravel (1 liter), etc. instead of the hardening liquid (M) such as cement milk (Figs. 5 and 10). In this case, gravel (II) or the like may be dropped and filled into the ri5 gap from around the shaft on the ground. Further, after the cylindrical pile (P) is set and compacted, a casing may be separately hung into the gap around the pile, and gravel or the like may be filled while compacting with the casing. In this case, it is also effective in increasing the horizontal bearing capacity.

In addition, when the cylindrical pile (F) at the top of the pile is a steel pipe pile (6), etc., not only the outer periphery of the pile but also the inner hole may be filled with gravel, as in the case of the driving method described above. be.

Note that the foundation pile of the present invention can also be produced by a mixing method in which a ready-made pile is press-fitted into a cement soil excavation hole in which earth and sand in the ground and injection hardening liquid are mixed. The method in this case is almost the same as the pre-drilling method.

In the foundation pile of the present invention constructed as described above, in the upper ground, concrete with a large amount of bristles such as PC pile, PHC pile, etc. is used as a cylindrical pile (P) with a large bending strength. Pile, composite pile (steel pipe concrete composite pile) with high bending strength, steel pipe pile (8), or one with the same diameter or larger diameter as the body (3) of the knotted pile (F) connected below. The cylindrical pile (P) is selected and used as appropriate depending on the magnitude of the axial force and bending moment acting on the foundation pile and the soil properties, and this cylindrical pile (P) can sufficiently support the horizontal load acting on the superstructure. In addition, in the lower ground, joints (2)
Since knotted piles (P) are used that can be expected to have a large circumferential support force R due to the presence of . Therefore, it is possible to obtain a safe, strong, and economical foundation pile that has a bearing capacity that is compatible with the ground.

In particular, the tip of the knotted pile (F) is usually embedded in the support layer, but the cylindrical pile (P)
) body (3) Even if the pile has the same diameter as the cylindrical pile (P), the tip knot of the knotted pile (P) is larger than the body diameter, so the tip supporting force is also large, making it economical and even more It becomes a safe foundation pile.

In addition, if the cylindrical pile (P) at the top of the foundation pile is one with a larger diameter than the trunk (3) of the knotted pile (F), or one with approximately the same diameter as the knot (2), , the axial strength of the pile is further increased, and the vertical bearing capacity is also further increased.

In addition, in soft and viscous ground, when the upper layer of the ground consolidates and settles, a negative frictional force acts on the upper part of the antibody, so if the peripheral support force is large, the antibody will not only receive the axial force due to the above negative frictional force, but also the axial force due to the structure load. However, according to the foundation pile of the present invention described above, since a cylindrical pile with a small circumferential bearing capacity is used in the upper ground, the axial force due to the negative N friction force is not borne. There is no.

In addition, when implementing the foundation pile of the present invention using the pre-drilling method, the strength of the hardening liquid such as cement milk that is injected into the hole is changed, and a high-strength hardening liquid is injected into the lower ground, and the hardening liquid is injected into the upper ground. If a hardening liquid with low strength is injected, the negative frictional force applied to the cylindrical pile will be reduced, and safe foundation piles can be constructed more economically, in the same way as described above.

[Effects of the Invention] As described above, according to the foundation pile structure of the present invention, a cylindrical pile with a large bending capacity can be installed in the upper ground where a relatively large horizontal capacity is required, and vertical bearing capacity such as circumferential bearing capacity can be expected. Knotted concrete piles with excellent circumferential bearing capacity are used in the lower ground, and these are connected and cast, so the horizontal bearing capacity of the upper ground and the vertical bearing capacity of the lower ground are excellent. It is possible to construct safe and economical foundation piles that have a bearing capacity that is compatible with the soil.

Especially when the upper ground is soft and viscous ground,
Even if the upper layer of the ground consolidates and settles, causing negative frictional force, the upper layer of the ground uses cylindrical piles with low circumferential support, so it bears the axial force due to the negative frictional force. Never. Therefore, in combination with the horizontal bearing capacity of the upper part and the vertical bearing capacity of the lower part, it is particularly suitable for use on soft and viscous ground.

Furthermore, if the outer periphery of the cylindrical pile is filled with filler such as sand, gravel, crushed stone, etc., the horizontal bearing capacity of the surrounding ground will not only increase due to compaction, but especially if this filler is gravel, crushed stone, etc. , due to its drain effect, during earthquakes. Excess gap! } (This allows for the construction of strong foundation piles that effectively dissipate pressure and prevent liquid purification in the ground.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing one embodiment of the present invention, FIG. 2 is a partially enlarged front view of the same as the above, FIG. 3 is a partial sectional view of the end of the vail, and FIGS. FIG. 6 is a partial front view showing an embodiment, FIG. 6 is a partial sectional view showing still another embodiment, and FIG.
Figures (a), (b), and (C) are schematic sectional views showing the construction state of the foundation pile of the present invention, and Figures 8 (a), (b), and (c) are schematic cross-sectional views showing other construction states of the foundation pile of the invention. 9 is a partially enlarged view of the same as above, FIG. 10 is a partially enlarged sectional view showing another embodiment, and FIG. 11 is an explanatory view of a conventional example. (P)... Cylindrical pile, (P)... Knotted concrete pile, (2)... Knot, (3)... Body, (
4)...End metal fitting, (5)...Main reinforcement, (5a)...
・Auxiliary reinforcement, (6)...Steel pipe pile, (7)...Permeability hole, (11)...Gravel, (l3)...Sand, (M)・
...Curing liquid. Patent Applicant: Takechi Construction Co., Ltd. Figure 7 Figure 5 Figure 6 Figure 9 Figure 10 Figure 1l Figure N Planting

Claims (1)

[Claims] 1. A ready-made cylindrical pile is placed above the foundation pile that supports the horizontal load acting on the structure, and a ready-made knotted concrete pile is placed below this pile, and these two piles are connected to form the ground. A foundation pile structure characterized by being driven in. 2. The foundation pile structure according to claim 1, wherein the diameter of the connected cylindrical pile and the body diameter of the knotted concrete pile are approximately the same diameter. 3. The foundation pile structure according to claim 1, wherein the diameter of the connected cylindrical pile is larger than the trunk diameter of the knotted concrete pile. 4. The foundation pile structure according to claim 1, wherein the outer periphery of the ready-made cylindrical pile at the upper part of the foundation pile is filled with a filler such as sand, gravel, crushed stone, etc.