JP3071381B2 - Pile used for foundation structure of permafrost zone and pile foundation using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile used for a foundation such as a structure foundation in a permafrost zone and a pile foundation using the same. In the present invention, the permafrost zone refers to an area where a stratum frozen throughout the year (hereinafter referred to as a permafrost layer) is distributed irrespective of the season, and its annual average temperature is 0 ° C. or lower. Such permafrost zones include, for example, Alaska, Canada, Siberia, and the like.

[0002]

2. Description of the Related Art For example, when constructing a pipeline gantry or other structures in a cold region such as a permafrost region,
The active layer existing between the surface and the permafrost layer (the area from the surface to the permafrost layer, which is greatly affected by annual temperature changes, freezes and freezes in winter, and thaws in summer) It is essential to protect the structure from freezing and icing, for which pile foundations are commonly used.

[0003] By the way, the pile foundation in such a cold region is to be embedded into the permafrost and to counter the self-weight of the structure, the frost-freezing force, etc. by the icing strength between the permafrost and the pile surface. It is assumed that. And for this,
Although it is necessary to ensure the freezing strength between the permafrost and the pile and to fully embed the pile in the permafrost, there is a problem that the workability and economic efficiency are poor due to the special conditions of the permafrost zone. Was.

[0004] For this reason, as a countermeasure, several methods for reducing the frost heaving force acting on the pile foundation and increasing the frost adhesion strength between the permafrost and the pile foundation have been considered. .

As a conventional method, for example, there is a method as shown in FIGS. FIG. 8 shows a thermal pile method. In this figure, a corrugated portion 2 is formed on the outer periphery of a pile 1 made of a steel pipe pile, a concrete pile or the like in order to increase the freeze-fit strength, and a heat pipe 3 is inserted into the pile 1. A radiator 4 is provided at an upper end of the heat pipe 3. This pile 1
Is buried in the excavation hole 7 provided in the active layer 6 and the permafrost layer 5 and is backfilled with the sand slurry 8. In the figure, H indicates the penetration length of the pile 1, and h indicates the thickness of the active layer 6.

In such a thermal pile system, the temperature of the permafrost 5 at the root portion is forcibly cooled by the heat pipe 3 in the winter to store cold heat, and the freeze-thaw thickness in the summer (thickness of the active layer 6) is obtained. H), thereby increasing the effect of preventing freezing and frost heaving.

Further, the heat pile can prevent the permafrost on the peripheral surface of the pile 1 from being thawed due to heat input from the upper structure in summer. FIGS. 9A and 9B show a frost heave prevention pile system. The frost heave prevention method is a method in which the active layer and the periphery of the pile are filled with a material capable of cutting off the adhesion between the pile and the frozen soil. And a space between the pile 1 and the casing 9 is filled with a highly concentrated mixture 10 of oil and wax, and the outer periphery of the casing 9 is sand slurry 8
The back-filling is used to separate the frost heaving force. Reference numeral 9a is a flange provided at the lower end of the casing. Further, the one shown in (b) is a material 10a in which soil, oil, and wax are mixed and buried in a portion corresponding to the active layer 6 of the drilling hole 7.

FIG. 10 shows a pile system with increased freeze-adhesion strength, in which a notch or a corrugated portion 2 is provided at the root of the pile 1 into the permafrost 5 so that the pile 1 can be connected to the permafrost 5. The freezing strength of the active layer 6 is increased so that the freezing strength of the active layer 6 is counteracted. This method is the same as the conventional soil cement composite pile in that the bonding strength is increased to increase the resistance.

[0009]

However, the thermal pile can reduce the thickness h of the active layer 6 to some extent, but cannot reduce the freezing and frost heaving force so much that it effectively reduces the frost damage of the structure. It has not been prevented.

[0010] For example, in the winter of the first year of using the thermal pile, the amount of frost heave increases rather than the case without the thermal pile, and a large frost-freezing frost heavier force may be generated due to a decrease in the temperature of the deep ground. Further, even after the second year, there is a possibility that a decrease in the temperature of the active layer may increase the freezing and frost heaving force.
In the conventional use example, the penetration depth H of the thermal pile into the permafrost layer is made longer than necessary to prevent frost damage, but it is insufficient from the viewpoint of workability and economy.

On the other hand, in the frost heave prevention pile system, the pile peripheral surface is filled or backfilled with a mixture of oil and wax, but these operations must be performed on site.
Not only do they need machines and equipment for that, but they are not very good in terms of workability. In addition, since the mixture of oil and wax has fluidity enough to be backfilled at the site, the backfill material permeates and disperses into the surrounding ground in the summer, which requires refilling. In addition, environmental destruction such as melting permafrost due to freezing point depression occurs. In addition, in the double tube method, the casing rises and sinks as the active layer freezes and thaws, which may adversely affect the superstructure.

[0012] In the pile system with increased freezing strength, the permafrost existing at the root of the pile 1 is not always uniform like soil cement, and the freezing strength varies. Changes the adhesive force,
Thus, in order to obtain a large freeze-adhesion strength, there is a problem that a considerable processing accuracy is required for the deformed bar-like processing of the end portion and the like.

Further, the piles in the permafrost zone must have a length corresponding to the thickness h of the active layer 6 at the installation site. The thickness h of the active layer 6 depends on the region, the place, and the like. Due to the significant difference, piles of various lengths corresponding to the thickness of the active layer 6 must be prepared.

For this reason, for example, when a pile foundation is to be installed over a long distance as a pipeline base, piles of various lengths are conventionally produced in a factory in advance, transported to the site and transported to an active layer. Currently, piles with a length corresponding to the thickness of 6 are selected and installed.

For this reason, the packing is not only complicated, but also
There is a problem that the load becomes large and the transportation is troublesome, and the cost is increased because it is not suitable for mass production.

The present invention has been made in view of the above circumstances, and has excellent economical efficiency and workability, and can reliably support a structure in a permafrost zone, and is used for a foundation structure of a permafrost zone. And a pile foundation using the same.

[0017]

In order to solve the above-mentioned problem, the present invention firstly provides a pile which is used by being embedded in a permafrost layer and used for a foundation structure of a permafrost zone, A pile body having a portion to be embedded in the permafrost layer, wherein one or more holes are formed in a wall of the pile body to be embedded in the permafrost layer, whereby the pile Provided is a pile used for a foundation structure of a permafrost zone, in which an anchor effect occurs between the foundation and the permafrost.

[0018] Secondly, there is provided a pile used for a foundation structure of a permafrost zone in which the hole is provided in a plurality of stages along the longitudinal direction of the pile body.
Third, in any of the above piles, there is provided a pile used for a foundation structure of a permafrost zone, wherein the hole is a through hole in a direction orthogonal to an axis of the pile body.

Fourth, in the pile according to the first or second aspect of the present invention, the hole is provided in a plurality of steps along a longitudinal direction of the pile, and the through hole extends in a direction perpendicular to the axis of the pile. The holes and the directions of the through holes intersect each other.

Fifth, in any of the above pile structures,
The pile used for the foundation structure of the permafrost zone according to any one of claims 1 to 4 provided with a flange-like projection above or below the hole in the pile body.

Sixth, in any of the above-mentioned piles, there is provided a pile having a plastic coating on a portion of the pile body corresponding to an active layer existing on the permafrost layer. Seventh, a pile foundation constructed using any one of the above piles is provided. Here, the through hole is a pair of holes, and refers to a hole in which a line connecting the centers of the pair of holes is substantially orthogonal to the axis of the pile body.

[0022]

According to the present invention, the ground around the pile and the soil inside the pile are continuously consolidated and integrated with each other through a through hole provided in a portion of the pile which is embedded in the permafrost layer, and the anchor effect is obtained. Can be applied to the pile body. Due to this anchor effect, the vertical bearing capacity and pull-out resistance of the pile are increased, and the penetration depth of the pile into the permafrost can be reduced as compared with the conventional pile foundation. Costs can be reduced. In addition, by providing holes in multiple steps along the longitudinal direction of the pile body, the anchor effect can be exerted at different parts of the permafrost layer in the depth direction, so that the anchor effect between the pile and the permafrost layer is improved. Further improve.

Further, when the holes provided in the pile are formed as through holes in a direction perpendicular to the axis of the pile, the through holes can be formed at once by using a drill. Has the advantage that it can be processed. Also,
By making the directions of the through-holes orthogonal to each other, the support rod for the self-weight and the frost heave force becomes cross-shaped, and the force can be evenly transmitted to the four-sided permafrost ground. The anchor effect is further improved. Furthermore, by providing a flange-shaped projection above or below the through hole, the freezing strength between the pile outer surface and the surrounding permafrost bed increases, and the synergistic effect of the anchor effect and the freezing strength increase The resistance is further improved. Furthermore, by providing a plastic coating on a portion corresponding to the active layer of the pile body of each of the above aspects, the frost heaving force acting on the pile can be significantly reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a state in which a pile foundation according to one embodiment of the present invention is constructed in a permafrost zone. The pile body 11 is formed by joining an upper steel pipe 11a having no through hole and an anchor steel pipe 11b having a through hole by welding. The anchor steel pipe 11b is provided on a permafrost layer 14 below the active layer 13. It is rooted. The shape of the through hole 12 is not particularly limited, and may be circular as shown in the figure or polygonal.

The presence of the through holes 12 allows the ground around the pile body 11 and the soil inside the pile body 11 to be continuously consolidated and integrated, thereby providing an anchor effect to the pile.
It should be noted that the pile body according to the present invention is not limited to the anchor steel pipe 11b having the upper steel pipe 11a having a through hole welded thereto, but a through hole is provided at a position corresponding to the permafrost layer of one steel pipe pile. May be used.

The installation of such a pile foundation on a permafrost layer is performed as follows. First, a hole, which is usually about 20 cm larger than the outer diameter of the pile to be installed, is excavated to the burial depth of the pile, the pile is built in the excavation hole, and the gap between the pile and the excavation hole is filled with soil slurry. This slurry enters the inside of the pile 11 through the through hole 12 formed in the root portion of the pile 11, and the inside and outside of the pile are continuously filled with the slurry.

The filled slurry is frozen by the cold load of the permafrost in the permafrost layer, and is integrated with the permafrost in the vicinity. At this time, due to the freezing of the filling slurry inside the pile, the pile is also integrated with the surrounding permafrost.

Therefore, when a downward force due to the weight of the supporting structure or an upward force due to the freezing and freezing force acts on the pile, the frozen soil inside the through-hole integrated with the surrounding permafrost ground is shown in FIG. As shown in Fig. 5, these forces act as a support rod and exert an anchor effect.

As described above, the present invention makes use of the characteristics of permafrost, which has been inconvenient until now, very skillfully, and provides a pile for a foundation structure and a pile foundation extremely suitable for a permafrost zone. It is.

The number of through holes is not limited to one, but may be plural. The size, number and spacing of the holes are determined by the soil properties of the ground on which the pile foundation is to be installed. , And can respond to all soil types.

Further, a plurality of through holes may be formed along the longitudinal direction of the pile body, and the directions may be orthogonal to each other. For example, as shown in FIG. 3, the through holes 12a and 12b are formed so as to be orthogonal to each other. With such a configuration, as shown in FIG. 4, the support rod for the self-weight or the frost heave force becomes a cross shape, and the force can be evenly transmitted to the permafrost ground on all sides. The anchor effect between them is further improved.

Further, a flange-shaped projection may be formed above or below the through hole of the pile body 11. For example, as shown in FIG. 5, a flange-like projection 15 is formed above the through hole 12a and the through hole 12b. To form Thereby, the icing strength between the outer surface of the pile and the surrounding permafrost increases. That is, the effect of increasing the freezing strength is added to the above-mentioned anchor effect, and the synergistic effect further increases the resistance.

In the most preferred embodiment of the present invention, as shown in FIG. 6, a plastic coating 16 is formed on the surface of a portion corresponding to the active layer 13 of the pile 11 in each of the above-mentioned embodiments, which is embedded in the permafrost layer 14. I do. Thereby, the frictional force generated between the pile foundation and the active layer 13 is reduced, and the icing and freezing force can be significantly reduced. In this aspect, in addition to the above-described anchor effect, it is possible to realize a significant reduction in the frost heave force, so that the stability of the pile foundation can be further enhanced, and the most desirable form as the pile foundation in the permafrost zone Is realized. Note that this embodiment can be combined with any of the above embodiments, and therefore, the illustration of the through-hole portion is omitted in FIG.

In this case, plastic materials used for coating include polypropylene, propylene / ethylene copolymer, polyolefin-based plastics such as poly-4-methyl-1-pentene, polyethylene terephthalate, and the like.
In addition to thermoplastic polyesters such as polybutylene terephthalate, preferred are polyhaloolefin-based plastics such as polystyrene, rigid polyvinyl chloride and polychloro-3-fluoroethylene, and thermosetting plastics such as polyurethane.

Next, in order to confirm the effects of the present invention,
A description will be given of a result obtained by actually laying the pile according to the present invention in a permafrost zone, performing a pulling test, and measuring a pulling load at that time.

The pile used for the test was an upper steel pipe having a diameter of 325 mm, a wall thickness of 9.5 mm, and a length of 3.5 m, and a length of 2.5 m.
Was constructed by welding and joining the anchor steel pipes. The diameter and wall thickness of the anchor steel pipe were the same as those of the upper steel pipe. Fig. 7 shows the pile installed on the permafrost layer. In FIG. 7, (a)-
(F) is an example of the present invention, and (g) is a conventional pile shown as a comparative example. Table 1 shows the test conditions and results. The symbols a to g in Table 1 correspond to (a) and (b) in FIG.

[0037]

[Table 1]

A shows the case of one hole, the pulling load was measured to be 10 tons, and the pulling resistance was 1.4 times that of g in the comparative example, confirming the effect of the present invention. b is a case where three holes are provided in three groups and shifted by 120 ° in the circumferential direction of the pile. In this case, the pulling load is 14 tons, and it can be seen that the pulling load is larger than a. In this example, the positions of the holes are three steps, but when the diameter of the pile is large, it is also effective to provide holes at the same position in the height direction.

C is a case where a pair of through holes (the number of holes is two) is provided, and the pulling force is 15 tons, which is a larger value. d shows a case where two pairs of through holes (the number of holes is four) are arranged in two stages. The pulling load in this case was 20, and a value twice as large as a was obtained. In addition, although the example of d has shown the case where the direction of a through-hole cross | intersects mutually, even if it does not cross | intersect, it confirmed that the effect more than a was obtained.

E is a case where a plastic coating is applied to a position corresponding to the active layer of the upper steel pipe 11a in addition to d. In this case, the presence of the plastic coating layer 16 prevents the upward force (freeze-freezing force) acting when the active layer freezes from being transmitted to the pile body, so that the pulling load is even greater than in the case of d. Value, and it was confirmed that the drawing force increased due to the presence of the plastic coating.

F is an example in which, in addition to d, a flange-like projection is provided above the through hole. In this example, the flange-shaped projections penetrated the permafrost layer and became a resistance to the pull-out force, and the pull-out load had a large value closer to d, and it was confirmed that the pull-out force increased due to the presence of the flange-shaped protrusions. The degree of the increase was larger than in the case of e, and it was confirmed that the flange-like projection was extremely effective. It was also confirmed that the effect was not changed even if the flange-shaped projection was provided below the through hole.

As described above, it was confirmed that a had a larger pulling load than g in the comparative example, and that b to f had a larger pulling load than a. Therefore, b to f have a much larger pulling force than g used as a comparative example.

[0043]

As described above, according to the present invention, a pile having one or a plurality of holes formed in a portion of a pile to be rooted in a permafrost zone is installed. Since an anchor effect is generated between the pile and the permafrost, the vertical bearing capacity and pull-out resistance of the pile are significantly increased. Therefore, the structure in the permafrost zone can be reliably supported because the structure reliably resists the force acting on the pile. In addition, since the vertical supporting force and the pull-out resistance force of the pile are significantly increased in this way, the penetration length of the pile can be significantly shortened, and the workability and maintainability are improved. It is easy to manufacture, mass-producible, and easy to pack and transport. Therefore, a significant cost reduction can be achieved.

Further, by intersecting the directions of the plurality of holes with each other, the anchor effect between the pile and the permafrost is further improved, and the above-mentioned effect becomes more remarkable. Furthermore, by providing a flange-shaped projection above or below the through hole, the freezing strength between the pile outer surface and the surrounding permafrost bed increases, and the synergistic effect of the anchor effect and the freezing strength increase The resistance is further improved.

Further, by providing a plastic covering on a portion corresponding to the active layer of the pile, the freezing and freezing force acting on the pile can be greatly reduced. The vertical support capacity and pull-out resistance of the pile have been dramatically improved, the stability of the pile foundation can be further improved, and the pile penetration length can be further shortened, realizing the most desirable form as the pile foundation in the permafrost zone. You.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a pile foundation according to one embodiment of the present invention is constructed in a permafrost zone.

FIG. 2 is a view for explaining an anchor effect of the pile foundation of FIG. 1;

FIG. 3 is a view showing a state in which a pile foundation according to another embodiment of the present invention is constructed in a permafrost zone.

FIG. 4 is a view for explaining an anchor effect of the pile foundation of FIG. 2;

FIG. 5 is a view showing a state in which a pile foundation according to still another embodiment of the present invention is constructed in a permafrost zone.

FIG. 6 is a diagram showing a pile foundation according to still another embodiment of the present invention.

FIG. 7 is a view showing a state in which a pile according to an embodiment of the present invention is provided.

FIG. 8 is a view showing an example of a conventional pile foundation.

FIG. 9 is a view showing another example of a conventional pile foundation.

FIG. 10 is a view showing still another example of a conventional pile foundation.

[Explanation of symbols]

11; pile body, 11a; upper steel pipe, 11b; anchor steel pipe, 12, 12a, 12b; hole, 13; active layer, 14;
Permafrost layer, 15; collar projection, 16; plastic coating.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Kotoshi Takano 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Honko Tube Co., Ltd. (72) Inventor Yoshiyuki Morioka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside the Honko K.K. 44 (72) Inventor Alexander I Grychenko Russian Federation, 117296 Moscow, Vavillowa 52-4-284 (56) References JP-A-59-85036 (JP, A) JP-A-6-280253 (JP, A) (5) Field surveyed (Int. Cl. ⁷ , DB name) E02D 27/12 E02D 31/14

Claims (7)

(57) [Claims] 1. A pile which is used by being embedded in a permafrost layer and used for a foundation structure of a permafrost zone, comprising a pile body having a portion which is to be embedded in a permafrost layer. One or more holes are formed in the wall of the body to be entrapped in the permafrost layer, thereby creating an anchoring effect between the pile foundation and the permafrost, in the foundation structure of the permafrost zone. Pile used. 2. The pile according to claim 1, wherein the hole is provided in a plurality of steps along a longitudinal direction of the pile body. 3. The pile according to claim 1, wherein the hole is a through hole in a direction orthogonal to an axis of the pile body. 4. The hole is provided in a plurality of stages along the longitudinal direction of the pile, and is a through hole in a direction orthogonal to the axis of the pile, and the directions of the through holes cross each other. The pile used for the foundation structure of the permafrost zone according to claim 1 or 2, which is provided. 5. The pile used in the foundation structure of a permafrost zone according to claim 1, having a flange-like projection above or below said hole in said pile body. 6. The foundation for a permafrost zone according to claim 1, wherein a portion of the pile body corresponding to an active layer existing on the permafrost layer has a plastic coating. Piles used for construction. 7. A pile foundation constituted by using the pile according to any one of claims 1 to 6.