A combined sleeve for preventing salt swelling and dissolution of pile foundations in thick saline soil areas and its application method

Abstract

The invention relates to the technical field of construction of a collector line tower foundation and a photovoltaic panel support foundation, and discloses a combined casing for preventing salt swelling and dissolution of pile foundations in thick saline soil areas and a use method thereof. The combined casing comprises at least two layers of casings, a rollable structure is filled between the casings, and sealing structures are arranged at both ends of the combined casing; the rolling structure is butter and steel balls filled between the casings, and the sealing structure is a sealing rubber ring, which can seal the butter and the steel balls; the combined casing can transfer the tangential force generated by the thick saline soil due to the salt swelling and dissolution to the casing outside the combined casing, and the dustproof and hydrophobic lubricant is arranged on the outer casing for lubrication, thereby further reducing the pulling-up and pulling-down effect of the tangential force generated by the salt swelling and dissolution on the pile foundation, better protecting the pile foundation structure, and ensuring the stability of the pile foundation; the combined casing of the invention saves the need for basic treatment of the pile foundation for improving the interference of salt swelling and dissolution of saline soil, saves engineering cost, and reduces construction difficulty.

Description

Technical Field

[0001] The invention relates to the technical field of construction of a collector line tower foundation and a photovoltaic panel support foundation, and in particular to a combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas and a use method thereof. Background Art

[0002] With the development of power grid construction and new energy business in northwest my country, more and more overhead transmission line projects need to cross saline soil areas. Similarly, more and more photovoltaic power stations are built in the saline soil areas in northwest China with better light conditions. When carrying out infrastructure construction in saline soil areas, the impact of salt expansion and collapse of saline soil on the foundation of buildings must be considered. It is necessary to select reasonable foundation forms and calculation methods, and take measures to reduce the harm of saline soil.

[0003] Saline soil refers to soil with soluble salt content greater than or equal to 0.3% and less than 20%, and has engineering properties such as salt swelling or dissolution. Salt swelling mainly occurs in sulfate saline soil. The volume expands due to the absorption of a large amount of water when sodium sulfate crystallizes, which increases the pores between soil particles, loosens the soil particles, and forms a fluffy layer of salt crust peeling. Dissolution is the property of saline soil to sink due to the dissolution or erosion of salt crystals after being soaked in water. The salt swelling and dissolution of saline soil causes the soil to expand or shrink, which corresponds to the upward or downward tangential force of the pile foundation, destroying the pile foundation. If the pile foundation in the saline soil area is not carefully considered during the design and construction of the salt swelling and dissolution, it will cause the foundation to produce upward or downward deformation under the action of the tangential force, and even destroy the pile foundation. The design is based on the pull-out requirements of the building, the grade of saline soil, the lithology of the formation, the compression coefficient, the pull-out coefficient and other indicators to calculate the standard value of the pull-out ultimate bearing capacity of the foundation pile.

[0004] Patent CN 111622254 A discloses an anti-pullout pile foundation structure, including: a pile body; and also including: an angle-limiting pin, which is arranged on the lower side surface of the pile body, and includes a rotating shaft, which is perpendicular to the central axis of the pile body; a bolt, which is rotatably connected to the side surface of the pile body through the rotating shaft, the upper part of the rotating shaft is an upper bolt, and the lower part of the rotating shaft is a lower bolt, and the angle-limiting pin limits the activity angle θ of the upper bolt to 0°≤θ≤90°, and the activity angle θ of the bolt is the angle between the upper bolt and the central axis of the pile body above the bolt rotating shaft. An angle-limiting pin is added to the lower side surface of the pile body to solve the problem of increasing the pullout resistance of the pile foundation in the prior art, but this increases the cost and construction difficulty. In areas with thick saline soil, in order to meet the pullout resistance requirements of buildings, it is often necessary to increase the length of the pile foundation, and the foundation treatment and other methods all increase the project cost. Summary of the invention

[0005] The present invention provides a combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas and a use method thereof, which can be applied to pile foundations in thick saline soil areas, and can transfer the tangential force generated by the salt swelling and dissolution to the combined casing, so that the pile foundation is not easily disturbed by the salt swelling and dissolution of the saline soil, and the length and diameter of the pile foundation are reduced to the maximum extent, and the foundation treatment for increasing the pull-out resistance of the pile foundation is omitted, thereby saving engineering costs and reducing construction difficulty.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: a combined casing for preventing salt swelling and dissolution of pile foundations in thick saline soil areas, the combined casing comprising at least two layers of casing, a rollable structure is filled between the casings, and sealing structures are provided at both ends of the combined casing.

[0007] Preferably, the rollable structure is butter and steel balls.

[0008] Preferably, the sealing structure is a sealing rubber ring.

[0009] Preferably, the inner sleeve of the combined sleeve is a PVC tube, and the outer sleeve is a PE tube.

[0010] Preferably, the inner wall of the PVC pipe is adhered with wood chips by adhesive.

[0011] Preferably, the outer wall of the PE pipe is provided with a dustproof and hydrophobic lubricant.

[0012] Preferably, the inner diameter of the PVC pipe is 5 to 8 mm larger than the diameter of the pile foundation, and the inner diameter of the PE pipe is 5 to 8 mm larger than the outer diameter of the PVC pipe.

[0013] The present invention also provides a method for using a combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas, comprising the following steps:

[0014] Step 1: Make pile foundation holes;

[0015] Step 2: inserting the pile foundation into the combined casing for assembly;

[0016] Step 3: Place the pile foundation and combined casing assembled in step 2 into the pile foundation hole made in step 1.

[0017] Preferably, in step three, the combined casing is located in a saline soil layer, with the upper portion of the combined casing exposed above the ground surface and the lower portion slightly deeper than the saline soil layer.

[0018] Preferably, the joints between the two ends of the combined sleeve and the pile foundation are sealed.

[0019] The present invention has the following beneficial effects:

[0020] 1. The present invention transfers the tangential force generated by the salt expansion and dissolution of thick saline soil to the PE pipe outside the combined casing. The butter and steel balls between the PVC pipe and the PE pipe can be lubricated, and the outer wall of the PE pipe is sprayed with a dust-proof and hydrophobic lubricant for lubrication. The outer casing of the combined casing is subjected to the tangential force generated by the salt expansion and dissolution, and the tangential force is blocked from acting on the pile foundation, so that the pile foundation is protected from the influence of the salt expansion and dissolution.

[0021] 2. The present invention can shorten the length of the pile foundation, eliminate the need for basic treatment of the pile foundation to improve the stability of the pile foundation in saline soil areas, save engineering costs, and reduce construction difficulty.

[0022] 3. The various equipment materials of the combined casing of the present invention are easy to purchase, inexpensive, environmentally friendly and low in cost.

[0023] 4. The combined casing and pile foundation of the present invention are both prefabricated materials, which are convenient for large-scale centralized production, have low process difficulty, are easy to master, and are convenient for construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the combined casing and pile foundation of the present invention in a saline soil layer.

[0025] Figure 2 It is a cross-sectional view of the combined sleeve structure of the present invention.

[0026] Among them: 1. Sawdust layer; 2. Adhesive; 3. PVC pipe; 4. Steel balls; 5. Butter; 6. PE pipe; 7. Dust-proof and hydrophobic lubricant; 8. Pile foundation; 9. Ground surface; 10. Saline soil layer; 11. Non-frozen soil layer; 12. Sealing rubber ring. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings. The present invention provides a technical solution: a combined casing for preventing pile foundation salt expansion and dissolution in thick saline soil areas, such as Figure 1 , Figure 2The combined sleeve comprises at least two layers of sleeves, a rolling structure is filled between the sleeves, and sealing structures are provided at both ends of the combined sleeve. The inner sleeve of the combined sleeve is a PVC tube 3, and the outer sleeve is a PE tube 6. The inner diameter of the PVC tube 3 is about 5 to 8 mm larger than the diameter of the pile foundation 8, and the inner diameter of the PE tube 6 is about 5 to 8 mm larger than the outer diameter of the PVC tube 3; the rolling structure is butter 5 and steel balls 4, butter 5 is sprayed and filled with steel balls 4 between the outer wall of the PVC tube 3 and the inner wall of the PE tube 6, the diameter of the steel balls 4 is 3 mm, and the filling amount of the steel balls 4 can be determined according to actual conditions. The steel balls 4 and butter 5 can play a better lubricating effect between the sleeves, so that the tangential force generated by the salt expansion and dissolution of the saline soil mainly acts on the combined sleeve, especially on the outer sleeve of the combined sleeve, so that the outer sleeve is displaced, thereby reducing the influence of the tangential force on the pile foundation 8 and improving the stability of the pile foundation 8.

[0028] The sealing structure is a sealing rubber ring 12, which seals the butter 5 and the steel ball 4 between the PVC tube 3 and the PE tube 6. The middle of the sealing rubber ring 12 can pass through the pile foundation 8, and can seal the gap between the pile foundation 8 and the combined sleeve, which plays a role of waterproofing and heat preservation. The inner wall of the PVC tube 3 is adhered with wood chips through the adhesive 2, and the wood chips are blown and adhered to the adhesive 2 on the inner wall of the PVC tube 3 by a blower to form a wood chip layer 1, similar to fluff; the wood chip layer 1 on the inner wall of the PVC tube 3 can be used to isolate the cold air in the pile foundation 8 and the sleeve pores, which plays a role of heat insulation and heat preservation. The outer wall of the PE tube 6 is provided with a dustproof hydrophobic lubricant 7, preferably silicone oil, calcium stearate, etc., and the dustproof hydrophobic lubricant 7 is sprayed on the outer wall of the PE tube 6, so that the combined sleeve has hydrophobicity and a lower friction coefficient, which can reduce the effect of the tangential force generated by the salt expansion and dissolution on the combined sleeve, and further reduce the degree to which the tangential force affects the pile foundation 8.

[0029] Working principle of the present invention:

[0030] The principle of the present invention is to transfer the tangential force generated by the salt expansion and dissolution of thick saline soil to the external combined casing, and use the combined casing to bear the tangential force, block the tangential force from acting on the pile foundation 8, and protect the pile foundation 8 from the influence of the salt expansion and dissolution. The wood chips pasted on the inner wall of the combined casing can be used to isolate the cold air in the pile foundation 8 and the casing pores, and play a role in heat insulation and heat preservation. The butter 5 sprayed between the outer wall of the PVC pipe 3 and the inner wall of the PE pipe 6 and the filled steel balls 4 and the dust-proof hydrophobic lubricant 7 sprayed on the outer wall of the PE pipe 6 can all produce a lower friction coefficient, greatly reducing the effect of the tangential force generated by the salt expansion and dissolution on the combined casing, so that the combined casing can operate better, better protect the pile foundation 8 structure, ensure the stability of the pile foundation 8, and save the pile foundation 8 to improve the basic treatment disturbed by the salt expansion and dissolution of saline soil, saving engineering costs and reducing construction difficulty.

[0031] The present invention also provides a method for using a combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas, comprising the following steps:

[0032] Step 1: Lay out the lines at the pile position, put the hole-making equipment in place, and use mechanical equipment to make 8 pile foundation holes;

[0033] Step 2: insert the prefabricated pile foundation 8 into the prefabricated combined casing for assembly, and seal the gaps between the two ends of the combined casing and the pile foundation 8 with sealing rubber rings 12 to achieve waterproof and heat preservation effects;

[0034] Step 3: Place the pile foundation 8 and combined casing assembled in step 2 into the pile foundation 8 hole made in step 1. The combined casing is entirely inserted into the saline soil layer 10 . The upper part of the combined casing is exposed above the ground surface 9 , and the lower part is slightly deeper than the saline soil layer 10 , reaching the non-frozen soil layer 11 .

[0035] When using the combined sleeve of the present invention, butter 5 and filling steel balls 4 are sprayed between the PVC pipe 3 and the PE pipe 6 in the combined sleeve, and a dust-proof and hydrophobic lubricant 7 is sprayed on the outside of the PE pipe 6. Both of them have a lubricating effect and a low friction coefficient, which reduces the pulling and pulling effect of the tangential force generated by salt expansion and dissolution on the pile foundation 8, better protects the structure of the pile foundation 8, and ensures the stability of the pile foundation 8.

[0036] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. It should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

Claims

1. A combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas, characterized in that: The combined sleeve comprises at least two layers of sleeves, a rollable structure is filled between the sleeves, and sealing structures are arranged at both ends of the combined sleeve; the rollable structure is butter and steel balls; the sealing structure is a sealing rubber ring; the inner sleeve of the combined sleeve is a PVC tube, and the outer sleeve is a PE tube; the inner wall of the PVC tube is adhered with wood chips by adhesive to form a wood chip layer; the outer wall of the PE tube is provided with a dustproof and hydrophobic lubricant; when the combined sleeve is sleeved on the pile foundation, the gaps between the two ends of the combined sleeve and the pile foundation are sealed by the sealing rubber ring; when the tangential force generated by the expansion and dissolution of saline soil due to salt mainly acts on the combined sleeve, the inner sleeve and the outer sleeve are displaced.

2. The combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas according to claim 1 is characterized in that: The inner diameter of the PVC pipe is 5-8 mm larger than the diameter of the pile foundation, and the inner diameter of the PE pipe is 5-8 mm larger than the outer diameter of the PVC pipe.

3. A method for using a combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas, characterized in that: The following steps are involved: Step 1: Make pile foundation holes; Step 2: inserting the pile foundation into the combined casing described in any one of claims 1-2 for assembly; Step 3: Place the pile foundation and combined casing assembled in step 2 into the pile foundation hole made in step 1.

4. The method for using the combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas according to claim 3 is characterized in that: In the step 3, the combined casing is located in the saline soil layer, the upper part of the combined casing is exposed to the surface, and the lower part is slightly deeper than the saline soil layer.

5. The method for using the combined casing for preventing pile foundation salt swelling and dissolution in thick saline soil areas according to claim 4 is characterized in that: The joints between the two ends of the combined sleeve and the pile foundation are sealed.

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