A casing equipment for preventing short piles from being frozen and pulled out in frozen soil areas and its usage method

Abstract

The present invention discloses a casing device for preventing short piles from being frost-heaved in frozen soil areas and a using method thereof, which includes a casing sleeved outside a precast pile. An adhesive layer is coated on the inner wall of the casing, a filling layer is arranged on the adhesive layer, a lubricating layer is coated on the outer wall of the casing, and a sealing rubber ring is further connected to the inner wall at the upper end of the casing. The casing is a PE pipe. The adhesive layer is an adhesive sprayed on the inner wall. The filling layer is wood chips. The lubricating layer is a hydrophobic lubricating glue. The tangential frost heaving force generated by the frost heaving of thick-layer seasonal frozen soil is transferred to the casing, and the casing bears the frost cutting force, blocking the frost cutting force from acting on the pile body, so that the precast pile is not affected by the frost heaving effect, thereby the length of the precast pile can be shortened and the project cost can be saved.

Description

Technical Field

[0001] The invention belongs to the field of construction in regions with thick permafrost, and particularly relates to a casing device for preventing short piles from being frozen and pulled out in permafrost regions and a using method thereof. Background Art

[0002] With the development of China's power grid construction, more and more overhead transmission line projects need to cross permafrost regions. Similarly, more and more photovoltaic power stations are built in high-altitude and alpine permafrost regions with better lighting conditions. When carrying out infrastructure construction in permafrost regions, the influence of permafrost foundation on the foundation force must be considered, and a reasonable foundation form and calculation method need to be selected, and measures to reduce frost heaving should be taken.

[0003] Permafrost is composed of a complex "four-phase" system of solid mineral particles, ice inclusions and ice interlayers, bound and free water, gaseous components, etc. Each component is in a dynamic mechanical and thermal equilibrium due to changes in external conditions such as temperature. With the change of environmental factors, the engineering properties of permafrost often undergo a sudden change from one state to another. When the external temperature drops, a part of the unfrozen water in the soil freezes into ice, increasing in volume, causing relative displacement between soil particles, and the soil expands (frost heaves) towards the surrounding. If restricted and resisted by the foundation, the constrained soil will exert a reaction force on the foundation at this time, and this force is often called the frost heaving force.

[0004] In permafrost regions, pile foundation projects participate in the natural soil system in the form of foundations. According to the relationship between the frost heaving force and the foundation action, the frost heaving force suffered by the foundation is usually divided into three categories: tangential frost heaving force, normal frost heaving force, and horizontal frost heaving force. The tangential frost heaving force is perpendicular to the freezing front, and it is the uplift force that causes the foundation to displace upward with the frost heaving deformation of the soil; the normal frost heaving force is perpendicular to the freezing front and the foundation ground surface, forming an uplift force to lift the foundation upward; the horizontal frost heaving force is perpendicular to the side surface of the foundation, causing the foundation to be horizontally extruded or pushed and generating horizontal displacement.

[0005] If the consideration of frost heaving is not comprehensive enough in the design and construction of pile foundations in permafrost regions, it will cause the foundation to undergo uplift deformation or even damage under the action of the tangential frost heaving force. The design calculates the standard value of the ultimate uplift bearing capacity of the foundation piles according to indicators such as the anti-uplift requirements of the building, the permafrost depth, the formation lithology, the compression coefficient, and the anti-uplift coefficient. In regions with thick permafrost, in order to meet the anti-uplift requirements of the building, it is often necessary to increase the pile length, increasing the project cost. Summary of the Invention

[0006] The purpose of the invention is to provide a casing device for preventing short piles from being frozen and pulled out in permafrost regions and a using method thereof, so that the precast piles are not easily interfered by the frost heaving of permafrost.

[0007] The object of the present invention is achieved by the following technical means. A casing device for preventing short piles from being frozen and pulled out in frozen soil areas includes a casing sleeved outside a precast pile. An adhesive layer is coated on the inner wall of the casing, a filling layer is provided on the adhesive layer, a lubricating layer is coated on the outer wall of the casing, and a sealing rubber ring is also connected to the inner wall at the upper end of the casing.

[0008] The casing is a PE pipe.

[0009] The adhesive layer is an adhesive sprayed on the inner wall.

[0010] The filling layer is shredded wood chips.

[0011] The lubricating layer is a hydrophobic lubricating glue.

[0012] A method for using a casing device for preventing short piles from being frozen and pulled out in frozen soil areas includes the following steps:

[0013] Casing prefabrication: Spray the adhesive on the inner wall of the casing to form an adhesive layer, and spray the hydrophobic lubricating glue on the outer wall of the casing to form a lubricating layer;

[0014] Filling layer prefabrication: Sprinkle the shredded wood chips onto the inner wall of the casing, and the shredded wood chips adhere to the adhesive layer to form a filling layer;

[0015] Place the precast pile and the casing in the prepared hole position, and insert the precast pile into the casing. The upper end of the casing exposes above the ground surface.

[0016] At the position where the casing and the pile body expose above the ground surface, use a sealing rubber ring to enclose the gap between the inner wall of the casing and the outer wall of the pile body to seal the casing and the pile body.

[0017] The lower end of the casing is also deeper than the frozen soil layer.

[0018] The beneficial effects of the present invention are as follows: 1. Transfer the tangential frost heaving force generated by the frost heaving of thick seasonal frozen soil to the casing, use the casing to bear the frost cutting force, block the frost cutting force from acting on the pile body, so that the precast pile is not affected by the frost pulling effect, thereby shortening the length of the precast pile and saving the project cost.

[0019] 2. The shredded wood chips on the inner wall of the casing isolate the downward movement of cold air in the gap between the precast pile and the casing, playing a role in heat preservation and heat insulation.

[0020] 3. The wood chips are flexible materials with large gaps between them. In the process of the casing being pulled upward under the action of the frost cutting force, the wood chips will not have a great effect on the pile body, preventing the frost cutting force from being transmitted to the precast pile, and further ensuring that the precast pile is not affected by the frost pulling effect.

[0021] 4. The lubricating layer on the outer side of the casing has a low friction coefficient, further reducing the upward pulling effect of the frost cutting force on the casing, so that the casing can operate better, better protect the structure of the precast pile, and ensure the stability of the precast pile. Brief Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the present invention;

[0023] Figure 2 It is an enlarged schematic diagram of the casing wall;

[0024] Figure 3 It is a schematic diagram of the force on the present invention;

[0025] In the figure, 1 is the casing; 2 is the adhesive layer; 3 is the filling layer; 4 is the lubricating layer; 5 is the sealing rubber ring.

[0026] The present invention will be further described in detail below with reference to the drawings and embodiments. Detailed Description of the Specific Embodiment

[0027]

Embodiment 1

[0028] As Figure 1 shown, a casing device for preventing short piles from being frozen and pulled out in frozen soil areas includes a casing 1 sleeved outside a precast pile. The inner wall of the casing 1 is coated with an adhesive layer 2, a filling layer 3 is provided on the adhesive layer 2, the outer wall of the casing 1 is coated with a lubricating layer 4, and a sealing rubber ring 5 is further connected to the inner wall at the upper end of the casing 1.

[0029] The casing 1 is a PE pipe.

[0030] The adhesive layer 2 is an adhesive sprayed on the inner wall.

[0031] The filling layer 3 is wood chips.

[0032] The lubricating layer 4 is a hydrophobic lubricating glue.

[0033] As Figure 2 shown, the inside of the casing 1 is hollow, and the inner diameter is about 5 mm larger than the diameter of the precast pile. The entire casing 1 is sleeved outside the precast pile, and an adhesive is sprayed on the inner wall of the casing 1 to form the adhesive layer 2.

[0034] Wood chips are sprayed on the adhesive layer 2, and the wood chips adhere to form a thin layer on the adhesive, similar to fluff, that is, the filling layer 3. The wood chips are flexible materials, and there are large gaps between the wood chips. In this way, when the casing is pulled upward under the action of frost cutting force, the wood chips will not have a great effect on the pile body, preventing the frost cutting force from being transmitted to the precast pile. If a rigid material is used, the frost cutting force will be transmitted to the precast pile. Other flexible materials can also be used.

[0035] A hydrophobic lubricating glue is sprayed on the outer wall of the casing 1 to form the lubricating layer 4. The purpose is to reduce the friction coefficient and further reduce the upward pulling effect of the frost cutting force on the casing 1. Other materials with a low friction coefficient can also be used to form the lubricating layer.

[0036]

Embodiment 2

[0037] Based on Embodiment 1, as Figure 3 shown, a method for using a casing device for preventing short piles from being frost-heaved in frozen soil areas includes the following steps:

[0038] Casing prefabrication: Spray adhesive on the inner wall of the casing 1 to form an adhesive layer 2, and spray hydrophobic lubricating glue on the outer wall of the casing 1 to form a lubricating layer 4;

[0039] Filling layer prefabrication: Spray shredded wood chips onto the inner wall of the casing 1, and the shredded wood chips adhere to the adhesive layer 2 to form a filling layer 3;

[0040] Place the precast pile 6 and the casing 1 in the prepared hole position, and insert the precast pile 6 into the casing 1. The upper end of the casing 1 is exposed above the ground surface.

[0041] At the position where the casing 1 and the pile body are exposed above the ground surface, put a sealing rubber ring 5 into the gap between the inner wall of the casing 1 and the outer wall of the pile body to seal the casing 1 and the pile body.

[0042] The lower end of the casing 1 is also deeper than the frozen soil layer.

[0043] First, prepare the casing 1 in advance, and also apply the adhesive layer 2, the lubricating layer 4 and the filling layer 3 on the casing 1.

[0044] Insert the precast concrete pile into the casing 1, and then place it in the prepared hole position. At this time, the bottom end of the precast pile extends into the frozen soil layer, and the bottom end of the casing 1 also inserts into the soil layer below the frozen soil layer. The tops of the casing 1 and the precast pile are both exposed above the ground surface for connecting other structures to the upper ends of the casing 1 and the precast pile subsequently.

[0045] Finally, at the part where the casing 1 and the precast pile are exposed above the ground surface, since the inner diameter of the casing 1 is larger than the outer diameter of the precast pile, connect the sealing rubber ring 5 in the annular space between the two to seal the joint between the casing 1 and the precast pile, playing a role in waterproofing and heat preservation.

[0046] The soil at the bottom end of the casing 1 plays the role of the sealing rubber ring 5, closing the joint between the casing 1 and the precast pile from the lower end, and the shredded wood chips in the annular space between the two also play a role in heat insulation and preservation.

[0047] As Figure 3 shown, the tangential frost heaving force is perpendicular to the freezing front, which is an uplift force that causes the foundation to displace upward with the frost heaving deformation of the soil, pulling the precast pile upward. Now, the tangential frost heaving force is transferred to the casing 1, and the casing 1 is used to bear the dynamic shear force, preventing the frost cutting force from acting on the pile body and protecting the pile body from the influence of frost heaving.

Claims

1. A casing device for preventing short piles from being frozen and pulled out in frozen soil areas, characterized in that, it includes: A casing (1) sleeved outside the precast pile. An adhesive layer (2) is coated on the inner wall of the casing (1). A filling layer (3) is provided on the adhesive layer (2). A lubricating layer (4) is coated on the outer wall of the casing (1). A sealing rubber ring (5) is also connected to the inner wall at the upper end of the casing (1). The filling layer (3) is shredded wood chips sprayed on the adhesive layer (2). The inside of the casing (1) is hollow, and the inner diameter is 5 mm larger than the diameter of the precast pile. The sealing rubber ring (5) seals the annulus between the casing (1) and the precast pile.

2. The casing device for preventing short piles from being frozen and pulled out in frozen soil areas according to claim 1, characterized in that: The casing (1) is a PE pipe.

3. The casing device for preventing short piles from being frozen and pulled out in frozen soil areas according to claim 1, characterized in that: The adhesive layer (2) is an adhesive sprayed and brushed on the inner wall.

4. The casing device for preventing short piles from being frozen and pulled out in frozen soil areas according to claim 3, characterized in that: The lubricating layer (4) is a hydrophobic lubricating glue.

5. The using method of the casing device for preventing short piles from being frozen and pulled out in frozen soil areas according to claim 4, characterized in that, it includes the following steps: Casing prefabrication: Spray and brush the adhesive on the inner wall of the casing (1) to form the adhesive layer (2). Spray and brush the hydrophobic lubricating glue on the outer wall of the casing (1) to form the lubricating layer (4); Filling layer prefabrication: Spray the shredded wood chips onto the inner wall of the casing (1), and the shredded wood chips stick to the adhesive layer (2) to form the filling layer (3); Place the precast pile (6) and the casing (1) in the prepared hole position, and the precast pile (6) is inserted into the casing (1). The upper end of the casing (1) is exposed on the ground surface, At the position where the casing (1) and the pile body are exposed on the ground surface, put the sealing rubber ring (5) into the gap between the inner wall of the casing (1) and the outer wall of the pile body to seal the casing (1) and the pile body.

6. The using method of the casing device for preventing short piles from being frozen and pulled out in frozen soil areas according to claim 5, characterized in that: The lower end of the casing (1) is also deeper than the frozen soil layer.

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