JPS6010019A - Freezing damage preventive pile - Google Patents

Abstract

PURPOSE:To prevent damage by freezing on superstructures by a method in which a covering part having a spiral expandible part longer part longer than the thickness of an active layer or a seasonal frozen soil layer is fitted on a pile, and a spring is provided along the inner wall of the expandible part. CONSTITUTION:When an active layer 6 is frozen in the winter season, sand slurry 8 is also frozen to adhere to the surface of the covering part 11 of a pile 10. As the active layer 6 is heaved by freezing, an expandible part 12 is correspondingly extended with a spring 17 along the pile 1 to form an expanded portion T below a fixer 15. A fluid substance 18 packed into the space between the pile 1 and the expandible part 12 is moved upwards and gathered into the expanded portion T. The frost heaving force of the active layer 6 is absorbed by the expandible part 12 and the fluid substance 18 and prevented from its transmission to the pile 1. When the active layer 6 is thawed and settled in the summer season, the covering part 11 is also lowered and restored to its original state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pile foundations among structure foundations in cold regions, and more specifically to frost damage prevention piles.

When constructing pipeline frames and various other structures in cold regions such as permafrost or seasonal frozen land, it is essential to protect the structures from frost damage such as frost heave and thawing subsidence in active and seasonal frozen layers. be. Various countermeasure construction methods are used for this purpose, but the most common is pile foundations.

Here, permafrost areas include, for example, Alaska, Canada,
This refers to areas such as Siberia, where there is a geological layer that is frozen throughout the year regardless of the season (hereinafter referred to as permafrost 3), and the average annual temperature is below 0°C. The active layer is the area from the earth's surface to the permafrost layer, which is greatly affected by annual temperature changes, freezing and heaving in the winter, and thawing and sinking in the summer. Furthermore, a rare frozen layer refers to a geological layer that freezes in the winter and thaws in the summer in areas where there is no permafrost and the average temperature is below 0°C. In the following explanation, the seasonal frozen layer may be included in the active layer.

By the way, pile foundations in cold regions are rooted deep into the permanent Gi8 soil, and are designed to counteract the superstructure's own weight, frost heave, and negative friction by utilizing the strength of freezing between the permafrost and the pile surface. And for this,
It is necessary to have reliable freezing strength between the permafrost and the piles, and sufficient root length for the piles into the permafrost. However, the permafrost layer does not necessarily have uniform properties, and the freezing strength varies greatly depending on the soil quality and temperature. However, in reality, structures often suffer from frost damage, and the penetration length must be determined based on a design that takes into account a safety factor, which poses major problems in terms of workability and economic efficiency. Because of these prerequisites, several methods have been considered to reduce the amount of frost heave acting on pile foundations as a countermeasure.

Figures 1 to 3 show the permafrost zone and the main frozen zone.
Figure 1 shows the thermal pile method, Figure 2 shows the frost heaving prevention pile method, and Figure 6 shows the frost heaving prevention pile method, and Figure 6 shows the frost heaving prevention pile method. It is.

Figure 1 is a longitudinal cross-sectional view showing an example of the thermal pile method.
1 is an antibody made of steel pipe piles, concrete piles, etc., 2 is a corrugation provided around the outer circumference of the pile body 1 to increase the freezing strength, 6 is a heater I and a pipe inserted into the pile body 1, and 4 is a radiator. It is. 5 is the permafrost layer, 6 is the active layer, and pile body 1 is the active layer 6.
and are rooted in a borehole 7 made in the permafrost layer 5,
It is backfilled with sand slurry 8. In addition, H is pile body 1
h indicates the root length, and h indicates the thickness of the active layer O.

In such a thermal pile method, the temperature of the permafrost 5 in the joist part is forcibly cooled through the heat pipe 3L during the winter, and cold energy is stored, thereby increasing the freeze-thaw thickness and the active layer B, the thickness h. ), thereby reducing
This is intended to increase the ability to prevent frost heaving. Furthermore, this thermal pile can prevent the permafrost on the circumferential surface of the pile body 1 from melting due to heat input from the upper structure in the summer. In other words, according to the thermal pile method, negative friction acts on the pile as the permafrost around the pile thaws and sinks, and when this thawing area freezes in winter, extra frost-heaving blades act on the pile. This can be prevented.

However, Surful Pile is active layer 6 layer Jv h
However, it is not possible to significantly reduce the negative friction caused by freezing, and it is still not possible to prevent frost damage to structures. For example, in the winter of the first year of use, due to a drop in the deep ground temperature, the amount of frost heave increases compared to when the surf vile is not used, and large frost heave edges may occur. It is also conceivable that from the second year onwards, the decrease in temperature of the active layer will tend to increase the amount of ice formation. In conventional usage, the root length H of the surflevile into the permafrost is made considerably long to prevent frost damage, which poses problems from the viewpoint of workability and economy.

The frost heaving prevention pile method is a method in which a material is filled between the active layer and the surrounding surface of the pile to break the adhesion between the pile and the frozen soil, as shown in Figure 2 (
In the case shown in a), a casing 9 is arranged concentrically with the outside of the pile body 1 to form a double pipe system, and a mixture of highly concentrated oil and wax is used between the pile body 1 and the casing 9. Fill it with 10, ke.

- By backfilling the outer periphery of the sink 9 with sand slurry 8,
The freezing upper blade is separated. In addition, 9
a is a flange provided at the lower end of the casing. Further, in the case shown in FIG. 2(b), a material 10a containing a mixture of soil, oil and wax is used as a backfilling material for the active layer 6 of the construction hole 7.

In this type of frost heaving prevention pile system, the surrounding surface of the pile is filled with a mixture of oil, wax, etc. 4), but this requires 1 ton of work and must be done on-site, and does not require any machinery or equipment for that purpose, and is not very convenient in terms of workability. In addition, since mixtures such as oil and wax have enough fluidity to allow backfilling on site, the backfilling material permeates into the surrounding ground and disperses during the summer.
This requires refilling and causes environmental damage by lowering the freezing point and melting permafrost. In addition, in the double-pipe system, the casing may lift and sink as the active layer freezes and thaws, which can have a negative impact on the superstructure.

Figure 6 shows a pile system with increased freezing strength, in which notches and corrugations 2 are provided at the part of the pile body 1 that penetrates into the permafrost 5, thereby creating a gap between the permafrost 5 and the pile body 1. The freezing strength of the active layer 6 is increased to counteract the freezing upper blade of the active layer 6.

In this method, the properties of the permafrost at the root of the pile body 1 are not necessarily uniform, resulting in variations in the freezing strength, and the frost top edge changes depending on the shape and spacing of the notches and corrugations. In order to obtain high freezing strength,
There are problems such as the need for highly accurate machining to process the ends into a deformed steel bar.

The present invention was made to solve the above-mentioned conventional problems, and reduces the frost-heaving blades that act on piles due to freezing of the active layer and the seasonal frozen layer, and the negative friction that occurs in the summer. By adding the member to the antibody, the purpose is to prevent frost damage to the upper structure.

In order to achieve the above-mentioned purpose, the frost damage prevention pile according to the present invention has the following features:
A covering member having a spiral extensible part with a length equal to or greater than the thickness of the active layer or seasonal frozen layer is fitted onto the antibody, and the upper end of the covering member is placed near or near the bottom of the active layer or the seasonal frozen layer. In the lower part, f and the upper end above the ground surface, respectively f
l, fixed to the pile body and interposing a coiled spring along the inner wall or outer wall of the extensible part, or 1j the inner wall and the outer wall;
The present invention is characterized in that a fluid substance is filled between the antibody and the covering member as necessary. The present invention will be explained below using the drawings.

FIG. 4 is a longitudinal sectional view of an embodiment of the present invention. /f oh, 1st
The same parts as in Figs.
, the explanation is omitted. 11 is a spiral iJ expansion and contraction part 1 in the middle.
2, and cylindrical parts 13 and 14 are provided above and below the covering member. near or below the boundary.

14 are fixed to the pile body 1 by fixing members 15 and 16, respectively. Reference numeral 17 denotes a coiled spring interposed along the inner wall 12a of the large-diameter portion of the stretchable portion 12, and reference numeral 18 denotes a fluid substance filled in the space formed by the pile body 1, the stretchable portion 12, and the spring 17. It is.

Although the covering member 11 used in the present invention varies depending on the region, in general, 1) brittle fracture does not occur at temperatures ranging from room temperature to about 150°C, and 2) displacement of the concave edge prevents freezing of the active layer. Moxibustion is defined as 1+ if it is larger than the amount of frost heave (Δe), and (i) does not corrode or corrode from a fluid substance.

In addition, the coiled part inserted in the extensible part 12 allows the covering member 11 to smoothly cover against the melting and subsidence of the summer active layer.
This is to suppress large deformations such as excessive compression, crushing, and expansion of the covering member 11 due to the QJ binding of the winter active layer. When the member 11 is in an extended state, the fluid substance 18 filled inside is prevented from flowing upward or downward and becoming biased.

The strength of the spring 17 may be such that it can expand and contract following the freezing of the blade in the winter or the melting and subsidence in the summer. That is,
The size of the freezing upper blade acting per unit area of the pile 10 is P (kg/cm2), the size of the negative friction is S (kg/cm2), the diameter of the pile 10 is d (Cm), and the active layer B. The amount of frost heaving or subsidence - Δd (Cm), the thickness of active layer O in summer fea (cm), the thickness of active layer O in winter as eyt, <am>, then the strength of spring 17 k (kg/cm2) should be i7° within the range of the following formula.

However, in general, it is necessary that the negative friction has a smaller absolute value θ) than the freezing upper blade, and that it has a spring constant that can be expanded and contracted with respect to the negative friction. Furthermore, the material of the spring 17 is
Does not cause brittle fracture at low humidity xi of around 0°C; ■ Has no reversibility under full frost heave changes (approximately 10% to −Qll<); (θ,) Will not deteriorate or corrode due to fluid substances 18 These are referred to as strips 1'1-, and MM is made of, for example, stainless steel.

Furthermore, although the fluid substance 18 varies depending on the region,
In general, operate the flow 2 to a low temperature of about -51LI℃ (Pot temperature/'J) and reduce the temperature (deterioration or loss of antibody 1 and coating member 11!j') at J5 quality. This is referred to as Article 1, and representative examples are shown in Table 2.

2 (1 2) The frost damage prevention pile constructed as described above is installed using a conventional construction method.

(1) The active layer 6 and permafrost layer 5 are excavated by the burial depth of the piles 10 (h1H), the piles 10 are erected in the excavated holes 7, and the sand slurry 8 is backfilled around the piles 10.

(2) When the strength of the permafrost layer 5 is relatively low or when it is embedded in unfrozen soil, only the active layer 6 is excavated, the piles 10 are erected in the excavated hole 7, and then a pile driver is used to penetrate the permafrost. Alternatively, it is driven into unfrozen soil, and finally, sand slurry 8 is backfilled around the piles 10 in the active layer 6.

Next, the function of the damage prevention pile according to the present invention installed as described above will be explained with reference to FIGS. 4 and 5. FIG. 4 shows the state in which the frost damage prevention pile 10 according to the present invention is installed in the excavated hole 7 drilled into the active layer 6 and permafrost layer 5, and the state in summer.

When the active layer 6 freezes in winter, the sand slurry 8 also freezes and adheres to the surface of the covering member 11 of the pile 10. When the active layer 6 is frost heaved, the extensible portion 12 also follows this and expands along the pile body 1 together with the spring 17, as shown in FIG. However, since the upper and lower cylindrical parts 13 and 14 are fixed to the pile body 1, the fixed member 15
An expanded portion T is formed below.

As the stretchable part 12 expands, the fluid substance 18 filled between the pile body 1 and the stretchable part 12 moves upward and collects in the expansion part T. In this way, the frost heaving blade of the active layer B is absorbed by the extensible part 12 and the fluid substance 18 and is not transmitted to the pile body 1. In addition, due to the freezing of the active layer B, the expandable part 12
Even if it is compressed, since the spring 17 is interposed, deformation such as crushing or expansion will not occur, and therefore the fluid substance 18 will not be biased.

When the active layer 6 melts and sinks in the summer, the covering member 11 also descends following this, returning to the state shown in FIG. 4 again. Note that the negative friction generated as the active layer B melts and sinks is absorbed by the stretchable part 12 and the fluid substance 18, and has almost no effect on the pile body 1. Furthermore, the spring 17 allows the extendable portion 12 to be lowered and restored reliably and smoothly.

FIG. 6(a) is a schematic diagram showing the main part of another embodiment of the present invention. In this embodiment, a spring 17 is interposed along the outer wall of the small diameter portion 12b of the extensible portion 12, and its action is (b
) As shown in the figure. FIG. 7(a) is a schematic diagram 1 showing the main parts of yet another embodiment of the present invention;
Bathing on the outer wall of 2b, there is 2-L.

A spring 17.17a is inserted. In addition, (b
) is an explanatory diagram of its action.

Next, in cold regions, conventional steel pipe piles (7,), t
, ; When used and when using the frost damage prevention pile according to the present invention 1
I will explain about the experimental tea feeding. In the experiment, an apparatus as shown in FIG. 8 was used.

This device consists of a frame 32°62 erected on a base 31.
In addition to bridging the reaction frame 55 to
66 is installed, a model pile 67 is erected in the C square 36, a row 1 cell 68 is interposed between the model pile 67 and the reaction frame 36, and the inside of the soil tank 55 is A displacement meter 69 is provided to measure the surface displacement of ±36.

[Experiment example]

(1) Steel pipe pile (conventional type) Outer diameter: 34 rrm, length: 400 man, embedded length = 250 mm +21 Freeze damage prevention pile (corresponding to the example shown in Figure 4)
(a) Dimensions of antibody: Outer diameter = 2 5 rrrn, length: 4 [I Q m
m, embedded length: 250 feet tb) Material and dimensions of covering member Material: Chloroprene rubber Thickness Hl, 5 mm 1 Covering length:! +00mm (e) Spring material: Ni stainless steel Spring constant: 20 kg/cm (d) Fluid substance isoparaffin (C13 to C+n) The conventional steel pipe pile as described above and the frost protection pile according to the present invention were After setting up the experimental apparatus shown in Figure 8, the experimental apparatus was placed in a freezing room, and the temperature was increased from room temperature to -20°.
After about 24 hours, the temperature was changed to -40°C, and after this state was continued for about 48 hours, cooling was stopped. During this period, the displacement meter 6 measured the change over time in the amount of frost heave of ±66 within the Doso 35.
The results measured in step 9 are shown in Fig. 9, and the liquefaction of the upper blade is measured with the load cell 38 and the saw results are shown in Fig. 10 (A in the figure is a conventional steel pipe pile, B is related to the present invention (i
This is an experimental supply of E-damage prevention stakes). As is clear from the figure, although the amount of frost heaving is almost the same between the two, the frost heave of the frost heave blade is 6°5 ("g/ cm'l), whereas the uninvented frost damage prevention stake (B) is almost 0, and it is
i! Is it confirmed that it has been reduced to I vine? in.

In the above embodiment, the present invention was applied to pipe piles, but the present invention can also be applied to concrete piles and woody piles. It can also be used in conjunction with frost protection piles (for example, the frost protection piles shown in Figure 6).Furthermore, the shape of the expandable part and the materials, shapes, dimensions, etc. of each part, etc. The present invention is not limited to fiiJ, and may be modified as appropriate without departing from the gist of the present invention.

As is clear from the above description, r+ according to the present invention.

(The following are notable effects.)

+II Since the freezing edge of the active layer relative to the pile body can be set to approximately υ, structures in cold regions can be sufficiently protected from frost damage.

(21) Since a spring is inserted in the extensible part, even if excessive compression is applied to the extensible part due to freezing of the active layer, there is no risk of deformation such as crushing or expansion, and therefore, the fluid substance is unevenly distributed. There's nothing to do.

(3) Against the melting and subsidence of the summer active layer, the downward restoration of the covering member can be carried out more reliably and smoothly.

(It is possible to reduce the frost-heaving blade acting on the pile body, so the length of pile penetration can be significantly shortened.Furthermore, the workability and maintenance are 86, which can significantly reduce the cost by 1.

[Brief explanation of the drawing]

Figures 1 to 5 show the conventional method of reducing the upper edge of the freezing method.
(b) shows the frost heaving prevention pile method, and Figure 6 shows the frost heaving prevention pile method. FIG. 4 is a longitudinal sectional view of an embodiment of the present invention, FIG. 5 is an explanatory diagram of its operation, FIG. FIG. 7(a) is a schematic diagram of a main part of yet another embodiment of the present invention, FIG. 7(b) is an explanatory diagram of its operation, and FIG. 8 is a concept of an apparatus for testing a frost damage prevention pile according to the present invention. Figure 7 is a diagram showing the change over time in the amount of build-up between a conventional steel pipe pile and a frost damage prevention pile according to the present invention.
Figure 0 is also a diagram showing the change over time of the frozen heave blade. 1... Pile body, 5... Permafrost layer, 6... Active layer,
8...Sand slurry v-1io...Freeze damage prevention pile, 11...
・Covering part shrine, 12...Extendable part, 17, 17a ・
...Spring, 18...Fluid substance. Agent Patent Attorney Saburo Kimura Figure 4 85 Figure 5 1 , Figure 6 (a) (b) Figure 7 (a) (b)

Claims (1)

[Claims] For piles to be installed in cold regions where freezing upper blades act, a covering member having a spiral extensible part with a length equal to or greater than the thickness of the active layer or seasonal frozen layer is fitted onto the antibody, and the lower end of the covering member is fitted onto the antibody. The antibody is fixed near or below the bottom of the active layer or seasonal frozen layer, and the upper end is fixed to the antibody above the ground surface, so that the coil overflows the inner wall or outer wall or the inner wall and outer wall of the stretchable part. A frost damage prevention pile characterized in that a shaped spring is interposed therein, and a fluid substance is filled between the antibody and the covering member as necessary.