Refreezing construction method for soil around piles in permafrost region

Abstract

The invention relates to a permafrost region pile periphery soil re-freezing construction method which comprises the steps that a plurality of cooling pipes are erected along with a reinforcement cage of a pile foundation in advance, the liquid inlet ends of the cooling pipes are connected with a natural cooling tank through a liquid pump and a refrigerant inflow pipeline, and refrigerants are arranged in the natural cooling tank; the liquid outlet end of the cooling pipe is connected with a natural cooling tank through a refrigerant outflow pipeline to form a refrigerant circulating system; the pile foundation is poured, the multiple cooling pipes are embedded into the pile foundation, in the pile foundation pouring and maintaining process, a liquid pump is started, a refrigerant flows, and the pile foundation and frozen soil on the pile side are cooled through the cooling pipes; after the pile foundation is built, the cooling pipe is separated from the cooling circulation system, the refrigerant in the cooling pipe is pumped out, then evaporated liquor is added into the cooling pipe, and the condensation sections of the hot rods are installed at the liquid outlet end and the liquid inlet end of the cooling pipe, and by the adoption of the method, quick re-freezing of the frozen soil around the pile is achieved, and the construction progress is accelerated.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation construction, and in particular to a construction method for refreezing soil around piles in permafrost areas. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The annual average temperature in permafrost areas is low and the temperature difference between day and night is large, so the construction period is short. When constructing cast-in-place concrete in permafrost areas, the heat released by the hydration of concrete will seriously disturb the frozen soil, causing the frozen soil around the piles to melt radially up to 2 meters along the pile foundation. Permafrost areas are mostly high-temperature frozen soil with a long refreezing time. The melted soil around the piles has obvious water migration and the bearing capacity increases slowly, which prolongs the construction time of the pile foundation superstructure and delays the progress of the project. After the construction is completed, due to the high-temperature frozen soil area, the friction resistance on the pile side is small, which affects the stability of the pile foundation and the superstructure.

[0004] For concrete cast-in-place piles in permafrost areas, the natural refreezing method is generally used for the refreezing of soil around the piles during the current construction process. The large amount of hydration heat released during the hydration reaction of concrete produces a large thermal disturbance to the frozen soil around the piles, causing the frozen soil around the piles to melt radially, causing water redistribution, water accumulation, hole expansion and other problems, affecting the refreezing time of the frozen soil around the piles. The bearing capacity of the pile foundation in permafrost areas is mainly provided by the freezing force of the frozen soil around the piles. The refreezing time of the frozen soil around the piles has an important impact on the formation of the pile foundation bearing capacity and the subsequent construction time. After construction, in order to improve the bearing capacity, the current main method is to install a hot rod array by drilling holes near the pile side to achieve the goal of cooling the frozen soil and improving the bearing capacity and stability of the pile foundation, but it greatly increases the cost of hot rods, steel bars and construction, and the refreezing time is long, which affects the subsequent construction progress. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a construction method for refreezing the soil around piles in permafrost areas, which reduces the construction cost, shortens the refreezing time of the soil around piles, and speeds up the construction progress.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] The embodiment of the present invention provides a method for refreezing soil around piles in permafrost areas:

[0008] A number of cooling pipes are pre-installed with the steel cage of the pile foundation, and the liquid inlet end of the cooling pipe is connected to the natural cooling tank through a liquid pump and a refrigerant inflow pipe. The natural cooling tank is filled with refrigerant, and the liquid outlet end of the cooling pipe is connected to the natural cooling tank through a refrigerant outflow pipe to form a cooling circulation system;

[0009] The pile foundation is poured so that a plurality of cooling pipes are buried inside the pile foundation. During the pouring and curing of the pile foundation, the liquid pump works, the refrigerant flows, and the cooling pipes are used to cool the pile foundation and the frozen soil on the pile side;

[0010] After the pile foundation is built, the cooling pipe is separated from the cooling circulation system, the refrigerant in the cooling pipe is extracted, and then evaporative liquid is added to the cooling pipe. The condensation section of the heat rod is installed at the liquid outlet and liquid inlet ends of the cooling pipe. The cooling pipe and the condensation section together constitute the heat rod.

[0011] Optionally, the cooling pipe is a U-shaped pipe, including a first straight pipe section and a second straight pipe section parallel to the axis of the pile foundation, and a third straight pipe section arranged along the radial direction of the concrete cast-in-place pile is provided between the bottom ends of the first straight pipe section and the second straight pipe section.

[0012] Optionally, the first straight pipe section and the second straight pipe section are arranged at edge positions of the pile foundation.

[0013] Optionally, the third straight pipe sections of the plurality of cooling pipes are cross-distributed at equal intervals along the annular direction of the pile foundation.

[0014] Optionally, a refrigeration device is installed on the refrigerant inflow pipe between the heat pump and the natural cooling tank.

[0015] Optionally, the condensation section of the heat rod has a length of 1.5m-3m.

[0016] Optionally, before setting up the cooling pipe, first determine the influence radius of the heat rods on the frozen soil based on the pre-collected parameter information of the frozen soil around the piles, determine the spacing between adjacent heat rods based on the influence radius of the heat rods on the frozen soil, and set up the cooling pipe based on the determined spacing between the heat rods.

[0017] Optionally, the method for determining the spacing between adjacent heat rods is: after determining the initial spacing between adjacent heat rods, verify the layout plan of the heat rods; when the total heat absorption power of all heat rods does not meet the design requirements, reselect the heat rod specifications and / or adjust the spacing between the heat rods until the total heat absorption power of all heat rods meets the design requirements, thereby obtaining the final spacing of the heat rods.

[0018] Optionally, the heat dissipation of the pile foundation and the set soil area around the pile foundation is calculated, and whether the total heat absorption power of the heat rod meets the design requirements is determined based on the heat dissipation of the pile foundation and the set soil area around the pile foundation.

[0019] Optionally, the pile foundation is a cast-in-place concrete pile.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The frozen soil refrozen construction method of the present invention embeds a cooling pipe inside the pile foundation. During the pouring and maintenance of the pile foundation, the cooling pipe is cooled by the circulating flow of a refrigerant, so that the soil around the pile is quickly cooled and refrozen during the construction and maintenance of the pile foundation, and the bearing capacity of the pile foundation is increased. After the pile foundation is built, condensation sections of a hot rod are installed at the liquid inlet and outlet ends of the cooling pipe to form a hot rod, which can improve and maintain the bearing capacity of the pile foundation after construction. Compared with the natural refrozen method and the refrozen method using a hot rod after construction, the refrozen method using the circulating flow of a refrigerant has a faster refrozen speed, the bearing capacity is quickly improved during the construction and maintenance process, the bearing capacity is stable after construction, the construction period is shortened, the energy consumption and cost are reduced, and the stability of the pile foundation is improved.

[0022] 2. In the frozen soil refreezing construction method of the present invention, the cooling pipe can be used as the longitudinal reinforcement in the pile foundation, which saves the setting of the longitudinal reinforcement, achieves multiple effects, and saves construction costs.

[0023] 3. In the frozen soil refrozen construction method of the present invention, the cooling pipe includes a first straight pipe section, a second straight pipe section and a third straight pipe section. The straight pipe is used to avoid the problem of high refrigerant temperature at the inlet and outlet liquid ends and poor cooling effect caused by the long pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 is a flow chart of the method of embodiment 1 of the present invention;

[0026] Figure 2 is a schematic diagram of a cooling cycle system formed in Example 1 of the present invention;

[0027] Figure 3 It is a schematic diagram of the liquid inlet and liquid outlet of the cooling tube in Example 1 of the present invention;

[0028] Figure 4 This is a schematic diagram of the coordination between the cooling tube and the condensing section of the hot rod in Example 1 of the present invention;

[0029] Figure 5 This is a schematic diagram of area division in Example 1 of the present invention;

[0030] Among them, 1. cooling pipe, 2. liquid pump, 3. refrigeration device, 4. natural cooling tank, 5. liquid inlet end, 6. liquid outlet end, 7. condensation section of the heat rod. DETAILED DESCRIPTION

[0031] Example 1

[0032] This embodiment provides a method for refreezing the soil around piles in permafrost areas. Figure 1As shown, the following steps are included:

[0033] Step 1: Casting construction on the pile foundation. In this embodiment, the pile foundation adopts concrete bored piles. The construction method of concrete bored piles can adopt the existing construction method. The only difference is that when setting up the concrete bored pile steel cage, multiple cooling pipes 1 are used to replace part of the longitudinal steel bars of the steel cage, and the cooling pipes 1 are set up synchronously with the steel cage.

[0034] The cooling pipe 1 adopts a U-shaped pipe, including a first straight pipe section and a second straight pipe section arranged along the axial direction of the pile foundation, a third straight pipe section is arranged between the bottom ends of the first straight pipe section and the second straight pipe section, the third straight pipe section is arranged along the radial direction of the pile foundation and passes through the central axis of the pile foundation, the first straight pipe section, the second straight pipe section and the third straight pipe section constitute a U-shaped pipe, the first straight pipe section and the second straight pipe section extend from the top of the pile foundation along the axial direction of the pile foundation to the bottom of the pile foundation, replacing part of the longitudinal reinforcement in the steel cage, the bottom of the first straight pipe section and the second straight pipe section are connected through the third straight pipe section to form a loop.

[0035] In this embodiment, the cooling pipe 1 is composed of three straight pipe sections, which can achieve rapid cooling of the pile foundation and the frozen soil on the side of the pile, improve the cooling efficiency, and improve the problem of high refrigerant temperature in the inlet and outlet pipes and poor cooling effect caused by the long pipe thread of the spiral temperature control pipe.

[0036] The top end of the first straight pipe section serves as the liquid inlet end, and is provided with a bent section facing outward. After the pile foundation is cast, the liquid inlet end of the first straight pipe section extends from the top side of the pile foundation to the outside of the pile foundation. The top end of the second straight pipe section serves as the liquid outlet end, and is provided with a bent section facing outward. After the pile foundation is cast, the liquid outlet end of the second straight pipe section extends from the top side of the pile foundation to the outside of the pile foundation.

[0037] like Figure 2-3 As shown, after the steel cage and the cooling pipe 1 are placed into the pre-constructed drilled hole, the liquid inlet end 5 of the first straight pipe section is connected to the liquid pump 3 through the refrigerant inflow pipeline, and the liquid pump 2 is connected to the natural cooling tank 4 through the refrigerant inflow pipeline.

[0038] The top end of the second straight pipe section is used as the liquid outlet 6 and is directly connected to the natural cooling tank 4 through the refrigerant outflow pipeline to form a cooling circulation system.

[0039] Furthermore, a refrigeration device 3 is installed on the refrigerant inflow pipe between the liquid pump 2 and the natural cooling tank 4. The refrigeration device 3 can be an existing refrigeration equipment, which will not be described in detail here.

[0040] The natural cooling tank 4 is pre-constructed, and a refrigerant is placed in the natural cooling tank 4. Preferably, the refrigerant is an ethylene glycol solution, and the natural cooling tank 4 uses the natural air in the high-cold area to reduce the temperature of the refrigerant. The refrigeration device 3 is not used unless necessary, which meets the engineering requirements and reduces the construction cost.

[0041] After the refrigerant circulation system is built, the concrete pouring of the pile foundation begins. The first straight pipe section and the second straight pipe section are located at the edge of the pile foundation and distributed along the annular direction. The third straight pipe sections of multiple cooling pipes cross at the bottom end of the pile foundation and are evenly spaced along the annular direction of the pile foundation.

[0042] During the pouring process and the concrete curing process after the pouring is completed, the liquid pump 2 works, and the liquid pump 2 allows the refrigerant to circulate in the cooling circulation system to cool the pile foundation during the construction and curing process.

[0043] Step 2: construct the condensation section 7 of the heat rod, wherein the heat rod is a hollow heat rod.

[0044] like Figure 4 As shown, after the pile foundation is built, the top ends of the first straight pipe section and the second straight pipe section are separated from the refrigerant inlet pipe and the refrigerant outlet pipe, the refrigerant remaining in the cooling pipe is extracted, and then evaporative liquid is added to the cooling pipe 1. In this embodiment, the evaporative liquid uses liquid ammonia that can vaporize under the temperature conditions of frozen soil around the pile.

[0045] Then, the condensation section 7 of the heat rod is installed at the top of the first straight tube section of the cooling tube, i.e., the liquid inlet end of the cooling tube, and the top of the second straight tube section, i.e., the liquid outlet end of the cooling tube. The condensation end 7 is fixed to the cooling tube 1 by welding or detachably fixed by threaded fasteners such as bolts. The cooling tube 1 as the evaporation section and the condensation section 7 of the heat rod together constitute the heat rod. After installation, the condensation section 7 of the heat rod is located above the ground.

[0046] Active cooling can be achieved through heat rods, and the ecological environment will not be damaged during construction. It can not only protect the frozen soil environment around the pile foundation from degradation, but also improve the bearing capacity and stability of the pile foundation.

[0047] At the same time, the evaporation section of the heat rod is set in the pile foundation rather than in the frozen soil on the side of the pile, avoiding frozen soil excavation and reducing construction and material costs.

[0048] In this embodiment, in order to ensure the refreezing effect, before setting up the cooling pipe 1, the influence radius of the hot rod on the frozen soil is first determined based on the parameter information of the frozen soil around the pile collected in advance. The distance between any two hot rods should be less than twice the influence radius. After determining the distance between adjacent hot rods, multiple cooling pipes 1 are set up according to the distance between adjacent hot rods.

[0049] Specifically, meteorological data of the area where the bridge is located are collected, and combined with geological characteristics, basic thermophysical parameters of the frozen soil around the piles, permafrost types, and ground temperature change patterns are obtained as parameter information of the frozen soil around the piles.

[0050] In order to ensure the refrosting effect, a plurality of heat rods are arranged at equal intervals along the annular direction of the pile foundation, and the length of the condensation end of the heat rod is 1.5m-3m.

[0051] According to the parameter information of frozen soil around piles collected in advance, the influence radius r of a single heating rod on frozen soil is calculated according to the Fourier equation. The spacing between adjacent heating rods should be within the range of r, that is, the spacing between adjacent heating rods should be less than 2 times of the influence radius.

[0052]

[0053] Where r represents the heat transfer influence range of the hot rod, and m is the correction coefficient, which is generally 0.20-0.25.

[0054] λ w represents the thermal conductivity of the unfrozen water in the soil around the evaporation section of the hot rod; i represents the thermal conductivity of ice in the soil around the evaporation section of the hot rod; s1 represents the thermal conductivity of the soil around the evaporation section of the hot rod; s2 It represents the thermal conductivity of the concrete around the evaporation section of the heat rod;

[0055] The above coefficients can be obtained by combining the collected soil parameter information around the pile with soil tests. The existing methods can be used and will not be described in detail here.

[0056] θ u represents the unfrozen water content in the soil around the evaporation section of the hot rod; θ i represents the ice content in the soil around the evaporation section of the hot rod; θ s1 Represents the solid content in the soil around the hot rod evaporation section; θ s2 represents the concrete content around the hot rod evaporation section; the above coefficient can be obtained by combining the collected soil parameter information around the pile with soil tests, and the existing method can be used, which will not be described in detail here; t represents the temperature fluctuation period of the hot rod evaporation section, which can be obtained through experiments, and will not be described in detail here.

[0057] C w represents the specific heat capacity of the unfrozen water in the soil around the evaporation section of the hot rod; C i represents the specific heat capacity of ice in the soil around the evaporation section of the hot rod; C s1 represents the specific heat capacity of the soil around the evaporation section of the hot rod; C s2 It represents the specific heat capacity of the concrete around the evaporation section of the hot rod; the above parameters can be obtained by combining the collected soil parameter information around the pile with soil tests, and the existing method can be used, which will not be described in detail here.

[0058] T0 represents the temperature difference at the boundary of the heat transfer influence range of the heat rod, and generally takes 0.1 °C.

[0059] T1 + T2 represents the temperature difference in the evaporation section of the heat rod, which can be obtained from materials and will not be described in detail here.

[0060] The method for determining the spacing between adjacent heat rods is as follows: After determining the initial spacing between adjacent heat rods, verify the layout plan of the heat rods. When the total power of all heat rods does not meet the design requirements, reselect the heat rod specifications and / or adjust the spacing between the heat rods until the total power of all heat rods meets the design requirements to obtain the final heat rod spacing.

[0061] Specifically, as Figure 5 shown, conduct area division. The calculation area is in the direction of the pile foundation cross-section. There are N heat rods in the calculation area. Divide it into two circular areas according to the heat exchange characteristics. The first area is the pile foundation cross-section area, and its heat dissipation is Q1. The second area is the annular area set outside the pile foundation, and its heat dissipation is Q2.

[0062] The determined spacing between the heat rods should satisfy:

[0063] Q1 + Q2 < Ptotal t (2)

[0064] Where Ptotal is the total heat absorption power of all heat rods.

[0065] Q1 = C1(πR1 2 h1)ΔT1 + Q c M c (2 - 1)

[0066] Q2 = Lρ2θ i (π(R2 - R1) 2 h2) + C2(π(R2 - R1) 2 )ΔT2 (2 - 2)

[0067] In the formula:

[0068] L represents the latent heat of crystallization of water, which is a known quantity;

[0069] ρ represents the dry density of the soil, which is obtained from the pre-acquired pile perimeter soil parameter information;

[0070] θ i represents the natural soil ice content, which is obtained from the pre-acquired pile perimeter soil parameter information;

[0071] R1 represents the concrete volume; R2 represents the soil volume around the concrete, which is obtained from the pile foundation construction process parameters;

[0072] h represents the depth of concrete, i.e., the surrounding soil, which is obtained through the pile foundation construction process parameters;

[0073] C represents the heat capacity of the soil, which is obtained by pre-acquired soil parameter information around the pile;

[0074] ΔT represents the target temperature change, which is a preset value;

[0075] Qc represents the hydration heat of concrete per unit mass, which is the material parameter of concrete and is a known quantity;

[0076] Mc represents the concrete mass in the calculation area, which is obtained by calculation.

[0077] In this embodiment, within the calculation area, the total power of the evaporation section of multiple heat rods must be greater than Ptotal, and the total power of the condensation section is greater than the total power of the evaporation section. After the above verification calculation, the current heat rod specification parameters and spacing cannot meet the total heat absorption power requirement, then the specification parameters of the heat rods are reselected, the spacing of the heat rods is changed, and the calculation is repeated until the power requirement is met to obtain the final heat rod spacing, and the cooling tube is set up according to the final heat rod spacing.

[0078] In a practical application of this embodiment, taking a bridge pier pile foundation at a test site as an example, the following steps are included:

[0079] Obtain data, take the temperature difference T1+T2 of the hot rod evaporation section as 2℃, the temperature difference T0 of the boundary of the hot rod heat transfer influence range as 0.1℃, the temperature fluctuation period T of the hot rod evaporation section as 3600h, the m correction coefficient as 0.25, the average thermal conductivity λ around the evaporation section as 5.69kJ / (mh℃), and the average specific heat capacity C around the frozen soil of the evaporation section as 2302kJ / (m3.℃). Take the upper limit of permafrost as 2m, the average value of soil ρ as 1750kg / m3, and the latent heat of water crystallization phase change L as 334.56kJ / kg.

[0080] Step 2: The hot rod group at the test position adopts a circular setting of the pile edge;

[0081] According to formula 1, calculate the heat transfer influence radius of a single heat rod: r = 1.26m

[0082] According to the heat transfer influence radius, the initial design of the heat rod is as follows: the distance between the heat rod on the near edge side and the bridge pier is 1m, and the initial distance between adjacent heat rods is 1.5m (in this embodiment, the heat rods are arranged in a square, and the diagonal distance is less than the distance between the two influence radii 2*1.26=2.5m, the maximum adjacent distance is 1.58, and 1.5m is taken).

[0083] Step 3:

[0084] (1) Q1 calculation: Based on the calculation area,

[0085] Take 42.39m3, Qc as 310kJ / kg, Mc as 83932.2kg, and ΔT1 as 2.0℃.

[0086] Q1=26214145.56kJ

[0087] (2) Q2 calculation: Based on the calculation area,

[0088] π(R2-R1) 2 h2 takes 304.46m 3 ,θ i Take 16% and ΔT2 as 2.0℃.

[0089] Q2=29922572.37kJ

[0090] Based on the above, it can be calculated that Ptotal in the calculation area = 422.05W, so the heat absorption power of the evaporation section of a single hot rod must meet 422.05 / n W or more, where n is the number of hot rods (cooling tubes).

[0091] By adopting the construction method of this embodiment, a cooling pipe is buried inside the pile foundation. During the pouring and maintenance of the pile foundation, the cooling pipe is cooled by the circulating flow of the refrigerant, thereby achieving rapid cooling and refreezing of the soil around the pile during the construction and maintenance of the pile foundation, and the bearing capacity of the pile foundation is increased. After the pile foundation is built, hot rods are installed at the liquid inlet and outlet ends of the cooling pipe, which can improve and maintain the bearing capacity of the pile foundation after construction. Compared with the natural refreezing method and the refreezing method using hot rods after construction, the refreezing speed is faster, the bearing capacity is rapidly improved during the construction and maintenance process, and the bearing capacity is stable after construction, shortening the construction period, reducing energy consumption and costs, and improving the stability of the pile foundation. Moreover, the cooling pipe can serve as the longitudinal steel bar in the pile foundation, saving the setting of the longitudinal steel bar, achieving multiple effects, and saving construction costs.

[0092] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for refreezing soil around piles in permafrost areas, characterized in that: A number of cooling pipes are pre-installed with the steel cage of the pile foundation, and the liquid inlet end of the cooling pipe is connected to the natural cooling tank through a liquid pump and a refrigerant inflow pipe. The natural cooling tank is filled with refrigerant, and the liquid outlet end of the cooling pipe is connected to the natural cooling tank through a refrigerant outflow pipe to form a cooling circulation system; The pile foundation is poured so that a plurality of cooling pipes are buried inside the pile foundation. During the pouring and curing of the pile foundation, the liquid pump is started to flow the refrigerant, and the cooling pipe is used to cool the pile foundation and the frozen soil on the pile side; After the pile foundation is built, the cooling pipe is separated from the cooling circulation system, the refrigerant in the cooling pipe is extracted, and then evaporative liquid is added to the cooling pipe. The condensation section of the heat rod is installed at the liquid outlet and liquid inlet ends of the cooling pipe. The cooling pipe and the condensation section together constitute the heat rod.

2. A method for refreezing soil around piles in permafrost areas as claimed in claim 1, characterized in that: The cooling pipe is a U-shaped pipe, including a first straight pipe section and a second straight pipe section parallel to the axis of the pile foundation, and a third straight pipe section arranged along the radial direction of the concrete cast-in-place pile is provided between the bottom ends of the first straight pipe section and the second straight pipe section.

3. A method for refreezing soil around piles in permafrost areas as claimed in claim 2, characterized in that: The first straight pipe section and the second straight pipe section are arranged at the edge of the pile foundation.

4. A method for refreezing soil around piles in permafrost areas as claimed in claim 2, characterized in that: The third straight pipe sections of the plurality of cooling pipes are cross-distributed at equal intervals along the annular direction of the pile foundation.

5. A method for refreezing soil around piles in permafrost areas as claimed in claim 1, characterized in that: A refrigeration device is installed on the refrigerant inflow pipeline between the liquid pump and the natural cooling tank.

6. A method for refreezing soil around piles in permafrost areas as claimed in claim 1, characterized in that: The condensation section length of the heat rod is 1.5m-3m.

7. A method for refreezing soil around piles in permafrost areas as claimed in claim 1, characterized in that: Before setting up the cooling pipe, first determine the influence radius of the hot rod on the frozen soil based on the pre-collected parameter information of the frozen soil around the pile, determine the spacing between adjacent hot rods based on the influence radius of the hot rod on the frozen soil, and set up the cooling pipe based on the determined spacing between the hot rods.

8. A method for refreezing soil around piles in permafrost areas as claimed in claim 7, characterized in that: The method for determining the spacing between adjacent heat rods is as follows: after determining the initial spacing between adjacent heat rods, verify the layout of the heat rods; when the total heat absorption power of all heat rods does not meet the design requirements, reselect the heat rod specifications and / or adjust the spacing between the heat rods until the total heat absorption power of all heat rods meets the design requirements, thereby obtaining the final spacing of the heat rods.

9. A method for refreezing soil around piles in permafrost areas as claimed in claim 8, characterized in that: Calculate the heat dissipation of the pile foundation and the set soil area around the pile foundation, and determine whether the total heat absorption power of the heat rod meets the design requirements based on the heat dissipation of the pile foundation and the set soil area around the pile foundation.

10. A method for refreezing soil around piles in permafrost areas as claimed in claim 1, characterized in that: The pile foundation adopts concrete cast-in-place piles.

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