JPS6010020A - Freezing damage preventive pile - Google Patents

Abstract

PURPOSE:To prevent freezing damage on superstructures by a method in which a solid lubricant is coated over a range slightly longer the thickness of an active layer or a seasonal frozen soil layer on the surface of a pile body being driven to the active layer or the seasonal frozen soil layer. CONSTITUTION:Since the frictional coefficient between the surface of a lubricant 11 coated on the surface of a pile body 1 and soil or frozen soil is smaller than that with the surface of the pile body 1, even when the active layer 6 is heaved by freezing in the winter season, the frost heaving force to be applied to the pile 10 is reduced beyond that to be directly applied to the pile body 1 because of the generation of slippage. Since negative friction to be applied to the pile 10 in thawing and settlement of the active layer 6 in the summer season is likewise reduced, the pile 10 can be protected from frost damage and the superstructure can be protected.

Description

[Detailed Description of the Invention] The present invention relates to a pile foundation among structure #5 foundations in a cold region C-, and more specifically relates to frost damage prevention piles. When constructing pipeline frames and other various structures in cold regions, it is essential to protect the structures from frost damage such as frost heaving of the active layer and seasonal frozen layer, and subsidence due to melting. Various countermeasure construction methods are used, 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 (hereinafter referred to as permafrost) that remains frozen throughout the year regardless of the season, and the average annual temperature is below 0°C. The active layer is the part of the earth that extends from the earth's surface to the permafrost layer, and is greatly affected by annual temperature changes, freezing and heaving in the winter and thawing in the summer. Furthermore, the seasonal 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 addition, in the explanation below,
The active layer may include the seasonal frozen layer.

By the way, pile foundations in cold regions are embedded deep into the permanent soil, and the (lj i/F strength) between the permafrost and the pile surface is used to counteract the self-weight of the superstructure, the upper part of the freezing method, and the negative friction. For this purpose, it is necessary to have a permanent freezing strength between the Yonago and the pile, and a sufficient root depth for the pile to penetrate into the permafrost.However, from the left, the permafrost The layers do not necessarily have uniform properties, and the freezing strength varies greatly depending on the soil type and temperature. Therefore, in order to have sufficient freezing strength, it is designed to be rooted in the permafrost for a long time. However, in reality, structures often suffer from frost damage, and the penetration length must be determined based on a design with a safety factor added, which poses a major problem in terms of workability and economic efficiency. Due to these conditions, several methods have been considered to reduce the effects of frost heave acting on pile foundations.

Figures 1 to 3 show conventional methods of reducing frost heave on pile foundations in permafrost and seasonal frozen areas. Figure 1 is the thermal pile method, and Figure 2 is the frost heave reduction method. The prevention pile method, and Figure 6 shows the freeze strength increasing pile method.

Figure 1 is a longitudinal cross-sectional view showing an example of the thermal pile method.
1 is a pile body made of a steel pipe pile, a concrete pile, etc.; 2 is a corrugation provided on the outer periphery of the pile body 1 to increase the freezing strength; 6 is a heat vibrator inserted into the antibody 1; and 4 is a lanator.

・5 is the permafrost layer, 6 is the active layer, and the pile body 1 is in the active layer 6 and the excavation hole 7 provided in the permafrost layer 5 (two roots are widened,
It has been backfilled with sand slather IJ-8. In addition, H indicates the joist length of the pile body 1, and h indicates the thickness of the active layer B.

In such a thermal pile method, the temperature of the permafrost 5 in the joists is forcibly cooled during the winter by using a heat vibrator (B) to store cold energy, thereby increasing the freeze-thaw thickness and the thickness of the active layer (h). The aim is to reduce this and thereby increase the anti-freezing ability. moreover,
This thermal pile can prevent the permafrost on the circumferential surface of the pile body 1 from thawing due to heat input from the upper structure in the summer. In other words, according to the thermal pile method (2), negative friction acts on the pile due to the thawing part F of permafrost on the circumference of the pile, and this thawing part freezes in winter, causing excess frost-heavy edges on the pile. can be prevented from working.

However, although the thermal pile can reduce the thickness of the active layer 6 to some extent, it cannot reduce the negative friction of the ice 721 or more so much, and is still unable to prevent frost damage to the structure. For example, in the winter of the first year of use, due to the drop in the deep ground temperature, the frost heave gauge increases even more than when using thermal nozzles, and large frost heave edges occur. Sometimes. Furthermore, from the second year onwards, the decrease in temperature of the active layer is thought to cause a tilting process that increases the amount of ice formation. In conventional usage, the root length of thermal piles into permafrost has been long enough to prevent frost damage. The curve between the pile body 1 and the surrounding surface of the pile is filled with a material that acts as a barrier between the pile and the frozen soil. (Nikesing 9
The space between the pile body 1 and the casing 9 is filled with a mixture 10 of highly concentrated oil and wax, and the outer periphery of the casing 9 is backfilled with sand slurry 8. It is C-shaped so that the upper and upper frosting blades are separated. 2.9α is a flange provided at the lower end of the casing. , and what is shown in FIG. 2 (61) is a material 10α mixed with soil, oil, and wax used as a backfilling material for the active layer B of the construction hole 7.

This type of frost heaving prevention pile method involves filling or backfilling the surrounding surface of the pile with a mixture of oil and wax, but this must be done on-site and requires machinery and equipment for this purpose. Not only that, but it is also not very good in terms of workability.Also, mixtures of oil and wax have enough fluidity that they can be backfilled on site.
During the summer, the backfill material penetrates and disperses into the surrounding ground, requiring refilling and causing environmental damage such as melting of permafrost due to freezing point depression F. In addition, in the double pipe system, freezing and thawing of the active layer may cause the casing to lift and sink, which may adversely affect the superstructure.

Figure 6 shows the freezing strength increasing pile method.

Notches and corrugations 2 are added to the joists of the pile body 1 into the permafrost 5.
By providing this, the freezing strength between the permafrost 5 and the pile body 1 is increased, and the freezing of the active layer 6 (H4j upper blade (C2) is made by making two opposing blades).

In this method, the property of permafrost in the root part of pile body 1 ′(′f
The freezing strength is not necessarily uniform, and the frosting strength (variation occurs), and the frosting edge changes depending on the shape and spacing of the notches and corrugations. There is +1!q between steel bar processing ITi!, etc. (requires all manufacturing and machining with considerable precision).

Furthermore, by applying a viscoelastic substance such as asphalt or grease to the surface of the pile body, the frozen soil force of the active layer and the negative friction caused by thawing and sinking (two pairs of piles may be considered, but (After 1 minute, the viscoelastic substance peels off from the antibody due to repeated freezing and negative friction, making it impossible to expect the desired effect.

The present invention has been made to solve the above-mentioned conventional problems, and is aimed at preventing freezing of the active layer or seasonal frozen layer in winter.
Therefore, the objective is to completely reduce the negative friction that acts on the piles due to the freezing heave blades acting on the piles and the thawing and subsidence in the summer, and to prevent frost damage to the superstructure.

In order to achieve the above-mentioned object, the frost damage prevention pile according to the present invention is a pile that is installed in a cold region where freezing upper blades act. It is characterized by having its body surface covered in advance with a solid d"8 nott A'1, which is slightly thicker than the thickness of the previous layer or the seasonal frozen layer. The present invention will be explained using the following.

FIG. 4 is a vertical sectional Ifri diagram showing the basic configuration of the present invention, 'j
Figure 5 is an explanatory diagram of its operation.The same parts C2 as in Figures 1 to 6 are denoted by the same reference numerals, and explanations and explanations are omitted. Solid lubricant 11 is applied in advance to a substantially uniform thickness f2 by spraying or other means on an area slightly longer than the thickness of active layer B on the surface of pile body 1. This solid lubricant 11 The condition is that the coefficient of friction against soil or frozen frozen soil is smaller than that of the surface of the pile body, and that the pile body: 1. - surface can be coated,
-IQ11 Busy 7] The results are as shown in Table 1.

Table 1 Molybdenum disulfide (M, S), graphite, pbo, N
aM604. -'-1 The frost damage prevention pile configured as described above is installed in the ground using one of the following methods.

(1) Bury active/auxiliary layer 6 and permafrost layer 5 to length I (+
11) Pile i, o'f: Erecting, then pile 1
Backfill the sand slurry 8 into Group 1-H of ゜.

(2) If the strength of ik permafrost soil 5) W is not large and is rooted in unfrozen soil, excavate only the activity 1x 6 and dig there (after erecting 1 pile 1o). , the permafrost layer is driven into the permafrost layer by a pile driver.
Sand slurry 8=i is backfilled around the pile 1o.

According to the frost damage prevention pile of the present invention built in the ground in this way, the coefficient of friction between the surface of the antibody 10 (1 ml of lubricant 11 coated with 1 ml of soil or frozen soil) is as follows:
Since the coefficient of friction with the 8 surfaces of the pile 10 is smaller than the coefficient of friction with the 8 surfaces of the pile 10, the frost heaving edge applied to the pile 10 will cause slippage even if the active layer 6 freezes and heaves as shown in Figure 45 (T shown in Figure 1) due to freezing of the winter active layer. The frost heaving edge directly applied to the pile (- is reduced to +9 compared to -), and the negative friction applied to the pile 1° due to the melting and subsidence of the U seasonal active layer is also greatly reduced as shown in 4th i%l. Therefore, piles 10 (il: protection from frost damage) can be installed.

Next, in a cold region, experimental results will be described in which conventional steel pipe piles were buried one step and in which frost damage prevention piles according to the present invention were completely driven. In order to make friends, the g position γ1 was set as shown in Fig. 6. This device bridges the frame filter 2゜32 + two-panel frame 33 erected on the base 31, and also connects the pigeon board 31. An earthen tank 35 filled with +66 is installed on the top surrounded by a heat insulating layer 34 with a thickness of 100 mm, and a model pile 37 is inserted into the top 36 to form a model pile 37.
A load cell 38 is interposed between the frame 33 and the 1y frame 33, and the displacement of the surface of the soil 66 in the soil tank 65 is measured.
9f.

[Experiment example]

(1) Steel pipe pile (conventional) Outer diameter = 34mm, length: 400mm, embedded length: 250m
m (2) Freeze damage prevention pile according to the present invention (al antibody dimensions outer diameter: 27.5 valence, length: 400 mm, embedded length: 25
(3) Fixed lubricant material Molybdenum disulfide-based lubricating treatment agent Coating Φ thickness: 0-03 mm Coating length = 600 mm The conventional steel pipe pile as described above and the frost damage prevention pile according to the present invention C1 After setting up the experimental apparatus shown in Figure 6, the experimental apparatus was placed in a freezing chamber, and cooled to -20°C starting from 100°C, and then cooled to -40°C after about 24 hours. After changing the condition and continuing that condition for about 48 hours, the cooling medium was removed. The change over time in the amount of frozen soil 36 in the soil tank 65 during this period was added by 111 using the displacement meter 69, and the results are shown in Figure 7 C2. It is shown in FIG. 8 (in the figure, A is the conventional steel pipe pile, and B is the long-term result of the frost damage prevention pile of the present invention). From the figure it is clear that i-
(2. Even though the amount of freezing damage prevention pile B according to the present invention is larger than that of FLF4 pipe pile A),
Freezing frost heave is a steel pipe pile (At is 6.5
H/cyst, whereas the frost damage protection 1F according to the present invention.

It was confirmed that the value of pile B was approximately 1.1-1.2 Jr9/crii, which was reduced to one-sixth or less.

In the above embodiment, the present invention was applied to steel pipe piles, but the present invention can also be applied to concrete piles and Kizuki piles.
It can also be used in combination with the ``Kan-Kan-Ko-Kabuto-increasing pile'' shown in the figure. Table 1 shows an example of a solid lubricant that is suitable for the present invention.
However, the present invention is not limited thereto, and may be modified as appropriate, including the shape of the antibody, without departing from the gist of the present invention.As is clear from the above description, the present invention According to this, the following remarkable effects can be cited.

(1) Since the fL-freezing edge of the active layer against antibodies can be significantly reduced, structures in cold regions can be protected from frost damage.

(2) Freeze AS that acts on antibodies can be reduced, so the upper cutting edge can be reduced (π rooting distance can be significantly shortened. Furthermore, considering workability and maintenance, it is possible to reduce the cost by 111 yen and reduce the cost by 1.

[Brief explanation of the drawing]

No. I: Noko, Figure 163 is the conventional freezing freezing method.
T&Methods are the T type, and Figure 1 is the thermal) pile method, No. 21 (αl, (f)l is the frost heaving prevention pile method, and Figure 6 is the frost heaving prevention pile method. 41'A is a diagram showing the basic structure of this invention, Figure 5 is a diagram 1 explaining its function, and Figure 61 is a diagram showing the anti-freeze pile according to the present invention C1. Figure 7 is a line section showing changes in frost damage over time between steel pipe piles of the past and C1 of the present invention. It is a diagram showing the change over time of the 1jL stitch. 1: Pile body, 5: Water-filled frozen soil layer, 6: Active layer, 8: Sand slurry, 10: Freeze damage prevention pile, 11: Solid l'14 Layering agent.Representative Patent Attorney Sanro Kimura Figure 4 to 1 Figure 5

Claims (1)

[Claims] For piles to be installed in cold regions where frost heaving blades act, the pile body surface C2, which corresponds to the active layer or seasonal frozen soil layer of antibodies to be built, is preliminarily coated with the active layer or layer i.
5. A frost damage prevention pile characterized by being coated with the same lubricant for a length slightly longer than the thickness of the frozen soil layer,