Temperature control type anti-frost heaving retaining wall structure and design method thereof

Abstract

The invention provides a temperature control type anti-frost-heaving retaining wall structure and a design method thereof, and belongs to the technical field of infrastructure retaining engineering in cold regions, the temperature control type anti-frost-heaving retaining wall structure comprises a retaining wall body, a ground temperature energy conversion system and an intelligent control system, and the ground temperature energy conversion system is connected with the retaining wall body; the ground temperature energy conversion system is used for absorbing ground temperature energy, converting a gas-state heating medium from a low-pressure state into a high-pressure state, adjusting the flow of a liquid-state heating medium, reducing the pressure of the heating medium and dissipating the ground temperature energy into the retaining wall body, and the intelligent control system is electrically connected with the ground temperature energy conversion system; the controller is used for monitoring the temperature of filling soil on one side of the retaining wall body and controlling the ground temperature energy conversion system to operate according to the filling soil temperature so as to control the retaining wall body temperature and filling soil heat. The technical problems that the retaining wall frost heaving disease control difficulty is large, and the frost damage prevention and control effect is poor are solved, and the technical effects that the retaining wall and the filling temperature can be controlled, frost heaving disease control is easy, and the frost damage prevention and control effect is good are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of infrastructure support engineering in cold regions, and more specifically, relates to a temperature-controlled frost-resistant retaining wall structure and a design method thereof. Background Art

[0002] Retaining walls are a type of retaining structure commonly used in infrastructure civil engineering projects. The distribution area of ​​frozen soil in my country accounts for more than 70% of the total land area. The seasonal frost heave of the backfill of the retaining wall will produce horizontal and tangential frost heave forces on the back of the wall, causing cracks, tilts, horizontal displacements, and even fractures and collapses in the wall. After the spring thaw period, it may also thaw and overturn. Therefore, anti-frost heave design is one of the important issues of retaining wall engineering in frozen soil areas.

[0003] Frost heave force is the controlling condition of frost damage of retaining walls. The anti-frost heave design of retaining walls mainly includes three ways: reducing or eliminating the frost heave of soil, weakening the frost heave force of the wall-soil interface, and increasing the bearing capacity of the wall. Specifically, they include: (1) Replace the non-frost-heaving soil. The replacement range is the freezing depth of the fill soil.

[0004] The shortcoming of this measure is that the natural freezing depth in deep seasonal permafrost areas such as Northeast my country can reach more than 2.0m. When the freezing depth is large, the replacement volume is too large, the disposal of abandoned soil is difficult and the cost is high.

[0005] (2) Waterproof drainage method: Drainage holes are set on the wall, including bottom drainage, back wall drainage, inclined drainage and horizontal drainage. Waterproof materials such as geotextile membranes are set on the top surface of the wall to reduce the moisture content of the fill behind the wall.

[0006] The disadvantage of this measure is that the retaining wall is in an open climate and geological environment, and no measure can completely isolate the influence of groundwater, atmospheric precipitation and other factors on the moisture of the backfill behind the wall. Due to the presence of moisture, frost heave is an inherent property of the soil, and it is impossible to completely eliminate the frost heave force through replacement filling and water isolation and drainage methods.

[0007] (3) Insulation method: Use insulation materials to change the heat exchange conditions between the climate environment and the soil, reduce the freezing depth of the soil, and reduce the amount and force of frost heave. Retaining walls generally adopt two-way insulation measures, that is, laying insulation boards made of materials such as EPS on the back of the wall and the ground behind the wall at the same time.

[0008] The shortcoming of this measure is that the insulation material may affect the mechanical interaction mode between the retaining wall and the fill, affecting the retaining effect, and the insulation performance is prone to deterioration and mechanical strength decrease after being saturated with water, and the durability is insufficient.

[0009] (4) Wall-soil interface smoothing method: Apply asphalt waterproofing material on the back of the retaining wall to make the wall-soil contact surface smooth and flat, reduce the freezing bond strength between the soil and the wall, and weaken the influence of the tangential frost heave force.

[0010] The disadvantage of this measure is that asphalt materials have poor durability in geological environments and pose a risk of pollution.

[0011] (5) Structural measures: First, treat the frost heave force as an external load and increase the wall section to meet the stability and strength requirements under the action of the frost heave force. Second, adopt anchor plate and buttress retaining wall types to increase the anchoring force of the stable stratum. Third, design new prefabricated empty box and culvert retaining structures with compression deformation capacity and large allowable displacement, which is conducive to reducing frost heave force.

[0012] The disadvantage of this measure is that it will increase the amount of work or structural complexity, and increase the cost and difficulty of construction.

[0013] In summary, the fundamental cause of frost heave disease of retaining walls lies in the negative temperature of the fill behind the wall. The above existing measures mainly focus on weakening the frost heave force and increasing the anti-slip bearing capacity, and cannot achieve artificial control of the key disaster-causing factor of frost heave of the fill behind the wall. It is difficult to control frost heave in cold and water-rich areas such as those behind the wall with good surface water collection conditions, shallow groundwater levels, and large freezing depths. After the construction of the retaining wall is completed, when adverse working conditions such as extreme cold weather are predicted, there is a lack of effective response measures and post-disaster disposal measures. Summary of the invention

[0014] The purpose of the present invention is to provide a temperature-controlled frost-heaving resistant retaining wall structure and a design method thereof, aiming to solve the technical problems in the prior art that the frost heaving disease of the retaining wall is difficult to control and the frost damage prevention and control effect is poor.

[0015] To achieve the above object, the technical solution adopted by the present invention is to provide a temperature-controlled frost-resistant retaining wall structure, comprising: The retaining wall body, with the upper part located at the top of the foundation and the lower part extending into the foundation, is used to support unstable cutting slopes on both sides of traffic lines, roadbed widening of mountain railways and highways, and the edge of building foundations; A geothermal energy conversion system is connected to the retaining wall body and is used to absorb geothermal energy, convert the gaseous heat medium from a low-pressure state to a high-pressure state, and is also used to adjust the flow of liquid heat medium and reduce the heat medium pressure and to dissipate the geothermal energy into the retaining wall body to increase the temperature of the retaining wall body and the heat of the fill; The intelligent control system is electrically connected to the geothermal energy conversion system, and is used to monitor the temperature of the backfill at the rear of the retaining wall body, and dynamically and intelligently control the operation of the geothermal energy conversion system according to the change of the backfill temperature, so as to control the backfill temperature of the retaining wall body within a preset threshold range, thereby preventing the backfill from cooling and freezing to form frost heave disease.

[0016] In a possible implementation, the retaining wall body includes: The micro pile is arranged vertically with the lower end extending to the foundation bearing layer and the upper end extending above the foundation, and the micro pile comprises a seamless steel pipe and a grouting layer arranged inside and outside the seamless steel pipe; A retaining wall is placed on the upper end of the foundation, the upper ends of the micropiles are inserted into the retaining wall, and the retaining wall and the micropiles are fixedly connected to each other; An outer protective layer, connected to the side of the retaining wall facing away from the fill, and used to protect the side of the retaining wall facing away from the fill; The inner protective layer is connected to the side of the retaining wall close to the fill and is used to protect the side of the retaining wall close to the fill. The fill is located outside the inner protective layer. The area on the side of the retaining wall close to the inner protective layer is defined as the rear of the retaining wall.

[0017] In a possible implementation, the thickness of the outer protective layer is not less than 5 cm, the thickness of the inner protective layer is not less than 10 cm, the outer protective layer is mixed with low thermal conductivity material, and the inner protective layer is mixed with high thermal conductivity material.

[0018] In a possible implementation, the geothermal energy conversion system includes: A geothermal energy collector connected to the outer wall of the lower part of the micropile, the geothermal energy collector is used to convert the liquid heat medium inside it into a low-pressure gas state to absorb the geothermal energy in the foundation, and the geothermal energy collector includes a plurality of spiral coils; A geothermal energy converter, connected to the geothermal energy collector, is used to convert the gaseous heat medium from a low-pressure state to a high-pressure state to increase the temperature and heat flux density of the geothermal energy, and is also used to adjust the flow rate of the liquid heat medium and reduce the heat medium pressure; A radiator is connected to the geothermal energy converter and is disposed inside the inner protective layer. It is used to convert high-pressure gaseous heat medium into liquid so as to dissipate geothermal energy into the inner protective layer to increase the temperature of the inner protective layer and the heat of the fill. The radiator includes a plurality of U-shaped coils.

[0019] In a possible implementation, the geothermal energy converter includes: A pressure converter, the inlet of which is connected to the outlet of the geothermal energy collector, and the outlet of which is connected to the inlet of the radiator. The pressure converter is used to convert the input gaseous heat medium from a low-pressure state to a high-pressure state. The inlet and outlet of the pressure converter respectively produce low-pressure suction and high-pressure ejection effects; A flow regulator, the inlet of which is connected to the outlet of the radiator, and the outlet of which is connected to the inlet of the geothermal energy collector. The flow regulator is used to adjust the flow of liquid heat medium and reduce the pressure of heat medium. The geothermal energy collector, the pressure converter, the radiator and the flow regulator are connected to each other end to end through a heat medium pipeline to form a closed circulation loop. The closed circulation loop is a vacuum environment and is filled with heat medium to dissipate the geothermal energy into the inner protective layer to increase the input heat and temperature of the fill.

[0020] In a possible implementation, the geothermal energy converter further includes: A power supply system, the power output ends of which are electrically connected to the pressure converter and the flow regulator, respectively, and are used to supply power respectively; Among them, the power supply system is one of a municipal power supply system, a photovoltaic power supply system, and a wind-photovoltaic complementary power supply system.

[0021] In a possible implementation, the intelligent control system includes: A temperature sensor is arranged inside the backfill of the retaining wall body and is used to monitor the backfill temperature in real time; A PLC controller is electrically connected to the temperature sensor and the pressure converter and the flow regulator of the geothermal energy conversion system respectively, and dynamically and intelligently controls the operation of the geothermal energy conversion system according to the received temperature information, so as to adjust the input heat and temperature of the backfill of the retaining wall body; The PLC controller pre-sets three temperature control thresholds, including a lower limit, an intermediate value, and an upper limit, the temperature relationship of the three being lower limit < intermediate value < upper limit, the lower limit being the average temperature of the fill in the freezing period in the natural environment, the intermediate value being 1 / 2 of the average temperature during the freezing period, and the upper limit being 0°C; The PLC controller is provided with four types of commands, including: The first type of command: starting the pressure converter and setting the flow regulator to the rated flow value of the heat medium; The second type of command: increasing the heat medium flow rate through the flow regulator to adjust the heat medium to fully participate in the circulation; The third type of command: reducing the heat medium flow rate through the flow regulator to adjust it to the rated flow rate value of the heat medium; The fourth type of command: closing the pressure converter and the flow regulator; When the fill temperature monitoring value is equal to or lower than the middle value, the PLC controller executes the first type of command; when the fill temperature monitoring value is equal to or lower than the lower limit value, the PLC controller executes the second type of command; when the fill temperature monitoring value increases from the lower limit value to above the middle value, the PLC controller executes the third type of command; when the fill temperature monitoring value is higher than the upper limit value, the PLC controller executes the fourth type of command; through the intelligent dynamic control process, the fill temperature at the rear of the retaining wall body is controlled within a pre-set threshold range.

[0022] The beneficial effects of a temperature-controlled frost-resistant retaining wall structure provided by the present invention are as follows: compared with the prior art, the temperature-controlled frost-resistant retaining wall structure provided by the present invention comprises a retaining wall body, a geothermal energy conversion system and an intelligent control system; the upper part of the retaining wall body is arranged at the upper end of the foundation and the lower part extends into the foundation, and is used to support unstable road cutting slopes on both sides of the traffic line, the roadbed widening of mountain railways and highways, and the edge of the building foundation; the geothermal energy conversion system is connected to the retaining wall body, and is used to absorb geothermal energy, convert the gaseous heat medium from a low-pressure state to a high-pressure state, and also to It is used to adjust the flow rate of liquid heat medium and reduce the pressure of heat medium and to dissipate the geothermal energy into the retaining wall body to increase the temperature of the retaining wall body and the heat of the fill; the intelligent control system is electrically connected to the geothermal energy conversion system to monitor the temperature of the fill on one side of the retaining wall body and control the operation of the geothermal energy conversion system according to the fill temperature to control the temperature of the retaining wall body and the heat of the fill, which solves the technical problems of difficulty in controlling frost heave disease of retaining wall and poor frost damage prevention and control effect, and has the technical effect of actively controlling the temperature of retaining wall and fill and having good timeliness in controlling frost heave disease.

[0023] The present invention also provides a design method for a temperature-controlled frost-resistant retaining wall structure, comprising the following steps: S1: Determine the initial temperature and thermal physical parameters of the frost heave strata and stable strata through on-site thermal response tests and indoor tests, and calculate the geothermal flux density and heat storage level of the stable strata; S2: According to the relevant design specifications of retaining walls and micropiles, combined with the design load and foundation conditions, the composite structure design is carried out according to the rigid connection between the retaining wall and the micropiles as an integral elastic foundation beam, including the height and width of the retaining wall, and the length, diameter, spacing, thickness and diameter of the micropiles; S3: Divide the retaining wall into several retaining wall sub-units according to the number of micro-piles. According to the typical meteorological data corresponding to the frost heave disease of retaining walls in previous years, calculate the hourly heat load when the backfill temperature of each retaining wall sub-unit is controlled above the target value, and determine the average and maximum heat load values. S4: Compare the heat storage level of the stable stratum with the average heat load of the retaining wall to check the design value of the micropile length; S5: Determine the rated flow value and charging amount of the heat medium of the geothermal energy conversion system; S6: Select the model of pressure converter and flow regulator according to the heat medium filling amount; S7: Determine the heat medium pipe length of the radiator and the U-shaped coil layout plan; S8: Determine the length of the heat medium pipeline and the spiral coil scheme of the geothermal energy collector; S9: Calculate the system power consumption based on the power consumption of the pressure converter and the flow regulator, and match the power supply with the corresponding power supply capacity.

[0024] In a possible implementation, the calculation method in step S3 includes: 1) Combined with the target value of fill temperature control behind the retaining wall T 0 Hourly air temperature T a , surface comprehensive heat transfer coefficient h c , calculate the air convection heat exchange between the retaining wall surface and the top of the backfill behind the wall Q c ; The calculation formula is:

[0025] In the formula, Q c is the cumulative value of air convection heat transfer, kJ; q c is the hourly value of air convection heat transfer, kJ; h c is the comprehensive heat transfer coefficient of the surface, W / (㎡·℃), A is the area of ​​the retaining wall and the side of the fill, m 2 ; T 0 is the temperature control target value of the backfill of the retaining wall body, ℃; T a is the air temperature, °C; 2) Combined with solar radiation heat conversion coefficient h r , calculate the surface radiation heat gain Q r ; The calculation formula is:

[0026] In the formula, Q r is the cumulative value of solar radiation heat transfer, kJ; q r is the hourly value of solar radiation heat transfer, kJ; h cis the installation heat transfer coefficient, W / (m 2 ℃), A is the area of ​​the retaining wall and the side of the fill, m 2 ; T 0 is the temperature control target value of the backfill of the retaining wall body, ℃; T a is the air temperature, °C; 3) Multiply the sum of air convection heat exchange and radiation heat gain by the heat load coefficient k , calculate the hourly heat load time history curve q , calculate and determine the average heat load q ave With the maximum value q max ; The calculation formula is:

[0027] In the formula, k is the heat load coefficient; t is time, h; In the above step S4, the verification method of the design value of the pile length of the micropile is that if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall is less than or equal to the design value of the pile length in S2, the design value remains unchanged; if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall is greater than the design value of the pile length in S2, the design value is increased to the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall; The calculation method in step S5 above includes: Determine the rated flow value of the heat medium m 0 , the calculation method is the average heat load divided by the latent heat of phase change per unit mass of heat medium; the calculation formula is:

[0028] In the formula, c is the latent heat of phase change of heat medium, kJ / kg; Determine the heat medium charge m max , the calculation method is the maximum heat load divided by the latent heat of phase change per unit mass of heat medium; the calculation formula is: .

[0029] In a possible implementation, the calculation method in step S7 includes: According to the density of liquid heat medium and the inner diameter of heat medium pipeline, calculate the mass of liquid heat medium inside the heat medium pipeline per unit length, and then divide the heat medium filling amount by the mass of liquid heat medium in the pipeline per unit length. Three times the calculated result is the length of the heat medium pipeline of the radiator. Lc Value; calculation formula is:

[0030] In the formula, ρ is the density of liquid heat medium, kg / m3; d is the inner diameter of the heat medium pipeline, m; According to the design size of the retaining wall and the length of the heat medium pipeline of the radiator, determine the spacing of the U-shaped coils inside the retaining wall; The calculation method in step S8 includes: Length of heat medium pipeline of geothermal collector L e 1.2 times the length of the radiator heat medium pipeline; According to the design size of the micropile and the length of the geothermal collector pipeline, the spacing of the spiral coils inside the micropile is determined.

[0031] The beneficial effect of the design method of a temperature-controlled frost-resistant retaining wall structure provided by the present invention is that: compared with the prior art, the design method of a temperature-controlled frost-resistant retaining wall structure provided by the present invention can accurately calculate the heat load of the fill and select the geothermal energy conversion system according to the structural form of the retaining wall body and the degree of frost damage of the rear fill, combined with the climatic conditions and geothermal energy storage conditions of the area, so that the two can reach a reasonable supply and demand balance, intelligently regulate the input heat and temperature of the fill at the rear of the retaining wall body, fundamentally solve the problem of frost damage to the retaining wall, and have a more effective, intelligent and energy-saving technical effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic diagram of the main structure of a temperature-controlled frost-resistant retaining wall structure provided by an embodiment of the present invention; Figure 2 A schematic diagram of a retaining wall body structure of a temperature-controlled frost-resistant retaining wall structure provided by an embodiment of the present invention; Figure 3 A schematic diagram of the structure of a geothermal energy conversion system and an intelligent control system for a temperature-controlled frost-heaving resistant retaining wall structure provided by an embodiment of the present invention (the arrows in the figure indicate the direction of heat medium flow); Figure 4 A schematic side view of a temperature-controlled frost-resistant retaining wall structure provided by an embodiment of the present invention; Figure 5 A control logic block diagram of an intelligent control system for a temperature-controlled frost-heavy resistant retaining wall structure during winter operation provided by an embodiment of the present invention.

[0034] Description of reference numerals: 1. Retaining wall body; 11. Micro pile; 111. Seamless steel pipe; 112. Grouting layer; 12. Retaining wall; 13. Outer protective layer; 14. Inner protective layer; 2. Geothermal energy conversion system; 21. Geothermal energy collector; 22. Geothermal energy converter; 221. Pressure converter; 222. Flow regulator; 23. Radiator; 3. Intelligent control system; 31. Temperature sensor; 32. PLC controller; 4. Foundation; 5. Filling; 6. Cabinet. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Please also read Figures 1 to 5 Now, a temperature-controlled frost-resistant retaining wall structure and a design method thereof provided by the present invention are described. The temperature-controlled frost-heaving resistant retaining wall structure comprises a retaining wall body 1, a geothermal energy conversion system 2 and an intelligent control system 3. The upper part of the retaining wall body 1 is arranged at the upper end of a foundation 4 and the lower part extends into the foundation 4, and is used to support unstable road cutting slopes on both sides of traffic lines, roadbed widening of mountain railways and highways, and edge parts of building foundations; the geothermal energy conversion system 2 is connected to the retaining wall body 1, and is used to absorb geothermal energy, convert gaseous heat medium from a low-pressure state to a high-pressure state, and is also used to adjust the flow rate of liquid heat medium and reduce the heat medium pressure and to dissipate geothermal energy into the retaining wall body 1, so as to increase the temperature of the retaining wall body 1 and the heat of the backfill 5; the intelligent control system 3 is electrically connected to the geothermal energy conversion system 2, and is used to monitor the temperature of the backfill 5 at the rear of the retaining wall body 1, and dynamically and intelligently control the operation of the geothermal energy conversion system 2 according to the change of the temperature of the backfill 5, so as to control the temperature of the backfill 5 at the rear of the retaining wall body 1 within a preset threshold range, so as to prevent the backfill 5 from cooling and freezing to form frost heaving diseases.

[0037] The present invention provides a temperature-controlled frost-heaving resistant retaining wall structure and a design method thereof. Compared with the prior art, geothermal energy is converted by using a geothermal energy conversion system 2, and the operation of the geothermal energy conversion system 2 is controlled by an intelligent control system 3 according to the temperature of the fill 5, thereby controlling the temperature of the retaining wall body 1 and the heat of the fill 5, thereby solving the technical problems of difficulty in controlling frost heaving diseases of the retaining wall 12 and poor frost damage prevention and control effects. The present invention has the technical effect of actively controlling the temperatures of the retaining wall 12 and the fill 5 and having good timeliness in controlling frost heaving diseases.

[0038] In some embodiments, see Figures 1 to 5 The retaining wall body 1 includes a micropile 11, a retaining wall 12, an outer protective layer 13 and an inner protective layer 14. The micropile 11 is vertically arranged with the lower end extending to the bearing layer of the foundation 4 and the upper end extending to the top of the foundation 4. The retaining wall 12 is placed on the upper end of the foundation 4, and the upper end of the micropile 11 is inserted into the retaining wall 12. The retaining wall 12 and the micropile 11 are fixedly connected to each other. The outer protective layer 13 is connected to the side of the retaining wall 12 away from the backfill 5, and is used to protect the side of the retaining wall 12 away from the backfill 5. The inner protective layer 14 is connected to the side of the retaining wall 12 close to the backfill 5, and is used to protect the side of the retaining wall 12 close to the backfill 5. The backfill 5 is located outside the inner protective layer 14, and the area on the side of the retaining wall 12 close to the inner protective layer 14 is defined as the rear of the retaining wall 12. Specifically, the outer protective layer 13 and the inner protective layer 14 form a clamp for the retaining wall 12, which effectively protects the retaining wall 12. There are multiple micropiles 11, which are arranged at intervals. The cooperation between the retaining wall 12 and the multiple micropiles 11 produces the following beneficial effects: from a mechanical point of view, the rigid connection between the two can transmit the fill pressure and frost heave force of the earth retaining wall 12 behind the micropiles 11, and utilize the structural resistance of the micropiles 11 and the foundation 4 to improve the anti-slip and anti-overturning performance of the upper retaining wall 12.

[0039] Preferably, the micro pile 11 is a bored pile with a diameter of 10 to 20 cm, which is implemented by a process combining implantation of a seamless steel pipe 111 and grouting, wherein slurry is poured inside and outside the seamless steel pipe 111, and a grouting layer 112 is formed after grouting outside the seamless steel pipe 111. The lower end of the pile body of the micro pile 11 reaches the bearing layer of the foundation 4, and the upper end of the pile body enters 1 / 3 of the height of the retaining wall 12. The retaining wall 12 is a cast-in-place reinforced concrete rectangular cross-section retaining wall 12, and the inner protective layer 14 and the outer protective layer 13 are both formed by concrete pouring, and a certain amount of heat conductive material is added during the pouring process.

[0040] In some embodiments, see Figures 1 to 5The thickness of the outer protective layer 13 is not less than 5 cm, and the thickness of the inner protective layer 14 is not less than 10 cm. The outer protective layer 13 is mixed with low thermal conductivity materials, and the inner protective layer 14 is mixed with high thermal conductivity materials. The function of the low thermal conductivity material is to block the heat of the retaining wall 12 from being transferred to the outside, reduce the cold input of the external environment to the retaining wall 12, and reduce the cooling amplitude of the backfill 5 behind the wall. The function of the high thermal conductivity material is to transfer the heat output by the geothermal energy conversion system 2 to the backfill 5 well to increase its temperature, and effectively improve the frost heave resistance of the retaining wall 12. The ratio of the low thermal conductivity material and the high thermal conductivity material corresponds to a certain proportional relationship with the weight of the outer protective layer 13 and the weight of the inner protective layer 14, respectively.

[0041] In some embodiments, see Figures 1 to 5 The geothermal energy conversion system 2 includes a geothermal energy collector 21, a geothermal energy converter 22 and a radiator 23. The geothermal energy collector 21 is connected to the lower outer wall of the micropile 11. The geothermal energy collector 21 is used to convert the liquid heat medium inside it into a low-pressure gas state to absorb the geothermal energy in the foundation 4. The geothermal energy collector 21 includes a plurality of spiral coils; the geothermal energy converter 22 is connected to the geothermal energy collector 21, and is used to convert the gaseous heat medium from a low-pressure state to a high-pressure state to increase the temperature and heat flux density of the geothermal energy, and is also used to adjust the flow rate of the liquid heat medium and reduce the heat medium pressure; the radiator 23 is connected to the geothermal energy converter 22, and is arranged inside the inner protective layer 14, and is used to convert the high-pressure gaseous heat medium into a liquid state to dissipate the geothermal energy into the inner protective layer 14, so as to increase the temperature of the inner protective layer 14 and the heat of the fill 5, and the radiator 23 includes a plurality of U-shaped coils. The geothermal energy collector 21 includes a spiral coil fixed on the outer wall of the seamless steel pipe 111 of the micropile 11 in a spiral winding manner and a heat medium pipeline connected to the spiral coil. The heat medium pipeline is a flexible heat medium pipeline with a diameter of 5 to 8 mm and a length of tens of meters to tens of meters. The spiral coil and the heat medium pipeline can be wound around the outer wall of the seamless steel pipe 111, and grouting is performed after winding. The grouting layer 112 after grouting is formed on the outer wall of the geothermal energy collector 21 and the seamless steel pipe 111, and the location of the grouting is below the maximum freezing depth of the foundation 4. The geothermal energy collector 21 and the micropile 11 form a composite structure, which has the following beneficial effects: from a thermal point of view, the geothermal energy collector 21 is embedded in the stable layer of the foundation 4 by means of the construction process of the micropile 11, absorbs the geothermal energy of the stable layer several meters below the foundation 4, and is protected by the grouting layer 112 on the outer layer of the micropile 11, which can isolate it from erosion and damage by the geological environment. It can be seen that the micro pile 11 has the ability to improve the mechanical properties of the retaining wall 12 and the ability to improve the thermal properties of the geothermal energy collector 21 .

[0042] Specifically, the radiator 23 includes a plurality of U-shaped coils and a heat medium pipeline connected to the plurality of U-shaped coils. The heat medium pipeline is a flexible heat medium pipeline with a diameter of 5 to 8 mm and a length of tens to tens of meters. The U-shaped coil is installed in the middle of the inner protective layer 14, and there is a distance between the end or side of the inner protective layer 14. The radiator 23 can efficiently exchange heat with the foundation 4 by means of high thermal conductivity materials, and input heat into the fill 5 at the rear of the retaining wall 12 and increase the temperature of the fill 5, so as to achieve the purpose of frost heave prevention and control. At the same time, the thickness between the radiator 23 and the outer surface of the retaining wall 12 is ensured to be not less than 5 cm, so as to ensure that the radiator 23 does not affect the retaining performance requirements of the retaining wall body 1.

[0043] In some embodiments, see Figures 1 to 5 The geothermal energy converter 22 includes a pressure converter 221 and a flow regulator 222. The inlet of the pressure converter 221 is connected to the outlet of the geothermal energy collector 21, and the outlet is connected to the inlet of the radiator 23. The pressure converter 221 is used to convert the input gaseous heat medium from a low pressure state to a high pressure state. The inlet and outlet of the pressure converter 221 produce low pressure suction and high pressure ejection effects respectively; the inlet of the flow regulator 222 is connected to the outlet of the radiator 23, and the outlet is connected to the inlet of the geothermal energy collector 21. The flow regulator 222 is used to adjust the flow of liquid heat medium and reduce the heat medium pressure; the geothermal energy collector 21, the pressure converter 221, the radiator 23 and the flow regulator 222 are connected to each other through a heat medium pipeline to form a closed circulation loop. The closed circulation loop is a vacuum environment and is filled with heat medium to dissipate the geothermal energy into the inner protective layer 14 to increase the input heat and temperature of the fill 5. The heat medium pipeline is a flexible heat medium pipeline with a diameter of 5-8 mm. The pressure converter 221 and the flow regulator 222 are both existing technology products, and their functions and working principles are not described here.

[0044] The working principle of geothermal energy conversion system 2 is: The heat medium circulates in a closed loop consisting of the geothermal energy collector 21, the pressure converter 221, the radiator 23, and the flow regulator 222, and the heat is collected, converted, transferred and transported through the latent heat recovery and release accompanied by the phase change of the heat medium. The specific process is: after the pressure converter 221 is started, the low-pressure suction effect at the inlet forms a low-pressure environment in the geothermal energy collector 21; the high-pressure ejection effect at the outlet forms a high-pressure environment in the radiator 23. First, the liquid heat medium enters the geothermal energy collector 21 through the flow regulator 222. The boiling point of the liquid heat medium in the low-pressure environment of the geothermal energy collector 21 is a negative temperature lower than the temperature of the foundation 4. After absorbing sufficient phase change latent heat, it quickly vaporizes, thereby realizing the collection of low-grade geothermal energy in the foundation 4 around the micropile 11 through the drastic temperature difference heat absorption effect; then, the gathered gaseous heat medium is sucked into the pressure converter 221, and becomes a high-temperature and high-pressure gas after being compressed by the pressure converter 221; then, the high-temperature and high-pressure gaseous heat medium enters the radiator 23 through the high-pressure ejection effect of the pressure converter 221 outlet. The condensation point of the gaseous heat medium in the high-pressure environment of the radiator 23 is lower than the natural environment temperature range, so it releases a large amount of phase change latent heat and then liquefies, thereby realizing the heating of the backfill 5 at the rear of the retaining wall 12 through the drastic temperature difference heat release effect, increasing the temperature of the backfill 5, weakening or eliminating the influence of the frost heave deformation of the backfill 5 on the retaining wall 12, and ensuring the stability of the retaining wall 12. Finally, the liquid heat medium flows into the geothermal energy collector 21 again through the flow regulator 222, and the cycle repeats. The phase change cycle of the heat medium can extract and supply heat energy that is 5 times the power consumption, which is essentially a heat enhancement device.

[0045] In some embodiments, see Figures 1 to 5 The geothermal energy converter 22 also includes a power supply system, whose power output ends are electrically connected to the pressure converter 221 and the flow regulator 222, and are used to supply power respectively; wherein the power supply system is one of a municipal power supply system, a photovoltaic power supply system, and a wind-photovoltaic complementary power supply system. In actual application, one of the power supply systems can be used for power supply according to actual conditions.

[0046] In some embodiments, see Figures 1 to 5 The intelligent control system 3 includes a temperature sensor 31 and a PLC controller 32. The temperature sensor 31 is arranged inside the backfill 5 at the rear of the retaining wall body 1, and is used to monitor the temperature of the backfill 5 in real time; the PLC controller 32 is electrically connected to the temperature sensor 31 and the pressure transducer 221 and the flow regulator 222 of the geothermal energy conversion system 2 respectively, and dynamically and intelligently controls the operation of the geothermal energy conversion system 2 according to the received temperature information, so as to regulate the input heat and temperature of the backfill 5 at the rear of the retaining wall body 1.

[0047] A plurality of temperature sensors 31 can be provided, which are provided at different positions or different areas, and can measure the filling temperature at different positions. The plurality of temperature sensors 31 are all electrically connected to the PLC controller 32 and all send temperature information. The freezing state of the fill is reflected according to the average value of the plurality of temperature information, and the dynamic control of the operation mode of the geothermal energy conversion system 2 can be realized, so as to reasonably control the temperature of the fill 5, etc., and realize the improvement of the anti-frost heave property. Preferably, a plurality of control logics are embedded in the PLC controller 32, which are used to control the operation state of the pressure transducer 221 and the flow regulator 222, that is, the adjustment parameter range. The control basis of the PLC controller 32 is: judging the freezing state and the change trend by the temperature of the fill 5 at the rear of the retaining wall 12, and then outputting the control command for the pressure transducer 221 and the flow regulator 222.

[0048] The present invention also includes a cabinet, wherein the geothermal energy conversion system 2 and the intelligent control system 3 are both installed inside the cabinet 6, and a mounting hole for the heat medium pipeline to pass through is provided on the side of the cabinet 6. The cabinet 6 can be installed at the top of the retaining wall 12, the top of the backfill 5 of the retaining wall 12, or the foot of the retaining wall 12 according to the application scenario conditions.

[0049] The present invention also provides a design method for a temperature-controlled frost-resistant retaining wall structure, comprising the following steps: S1: Determine the initial temperature and thermal physical parameters of the frost heave strata and stable strata through on-site thermal response tests and indoor tests, and calculate the geothermal flux density and heat storage level of the stable strata; S2: According to the relevant design specifications of the retaining wall 12 and the micro piles 11, combined with the design load and foundation conditions, the composite structure design is carried out according to the rigid connection between the retaining wall 12 and the micro piles 11 as an integral elastic foundation beam, including the height and width of the retaining wall 12, the pile length, pile diameter, pile spacing of the micro piles 11, and the thickness and diameter of the seamless steel pipe 111; S3: Divide the retaining wall 12 into several retaining wall 12 subunits according to the number of micropiles 11, calculate the hourly heat load when the backfill temperature of each retaining wall 12 subunit is controlled above the target value based on the typical meteorological data corresponding to the frost heave disease of the retaining wall 12 in previous years, and determine the average and maximum values ​​of the heat load; S4: Compare the heat storage level of the stable stratum with the average heat load of the retaining wall 12, and check the design value of the micropile length; S5: Determine the rated flow value and the charge amount of the heat medium of the geothermal energy conversion system 2; S6: Select the models of the pressure converter 221 and the flow regulator 222 according to the heat medium filling amount; S7: Determine the heat medium pipeline length and U-shaped coil layout plan of the radiator 23; S8: Determine the heat medium pipeline length and spiral coil scheme of the geothermal energy collector 21; S9: Calculate the system power consumption according to the power consumption of the pressure converter 221 and the flow regulator 222, and match the power supply with the corresponding power supply capacity.

[0050] The beneficial effect of the design method of a temperature-controlled frost-resistant retaining wall structure provided by the present invention is that: compared with the prior art, the design method of a temperature-controlled frost-resistant retaining wall structure provided by the present invention can accurately calculate the heat load of the fill 5 and select the geothermal energy conversion system 2 according to the structural form of the retaining wall body 1 and the degree of frost damage of the rear fill 5, combined with the climatic conditions and geothermal energy reserves of the area, so that the two can reach a reasonable supply and demand balance, intelligently regulate the input heat and temperature of the rear fill 5 of the retaining wall body 1, fundamentally solve the frost damage problem of the retaining wall 12, and have a more effective, intelligent and energy-saving technical effect.

[0051] In some embodiments, the calculation method in step S3 above includes: 1) Combined with the target value of fill temperature control after retaining wall 12 T 0 Hourly air temperature T a , surface comprehensive heat transfer coefficient h c , calculate the air convection heat exchange between the surface of retaining wall 12 and the top of the backfill behind the wall Q c ; The calculation formula is:

[0052] In the formula, Q c is the cumulative value of air convection heat transfer, kJ; q c is the hourly value of air convection heat transfer, kJ; h c is the comprehensive heat transfer coefficient of the surface, W / (㎡·℃), A is the area of ​​the retaining wall 12 and the side of the fill, m 2 ; T 0 is the temperature control target value of the backfill 5 of the retaining wall body 1, °C; T a is the air temperature, °C; 2) Combined with solar radiation heat conversion coefficient h r , calculate the surface radiation heat gain Q r ; The calculation formula is:

[0053] In the formula, Q r is the cumulative value of solar radiation heat transfer, kJ; q r is the hourly value of solar radiation heat transfer, kJ; h c is the installation heat transfer coefficient, W / (m 2 ℃), A is the area of ​​the side of the retaining wall 12 and the fill 5, m 2 ; T 0 is the temperature control target value of the backfill 5 of the retaining wall body 1, °C; T a is the air temperature, °C; 3) Multiply the sum of air convection heat exchange and radiation heat gain by the heat load coefficient k , calculate the hourly heat load time history curve q , calculate and determine the average heat load q ave With the maximum value q max ; The calculation formula is:

[0054] In the formula, k is the heat load coefficient; t is time, h; In the above step S4, the verification method of the design value of the pile length of the micropile is that if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall 12 is less than or equal to the design value of the pile length in S2, the design value remains unchanged; if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall 12 is greater than the design value of the pile length in S2, the design value is increased to the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall 12; The calculation method in step S5 above includes: Determine the rated flow value of the heat medium m 0 , the calculation method is the average heat load divided by the latent heat of phase change per unit mass of heat medium; the calculation formula is:

[0055] In the formula, c is the latent heat of phase change of heat medium, kJ / kg; Determine the heat medium charge m max The calculation method is the maximum heat load divided by the unit mass of heat medium phase change latent heat value. The calculation formula is: .

[0056] In some embodiments, the calculation method in step S7 above includes: According to the density of liquid heat medium and the inner diameter of heat medium pipeline, calculate the mass of liquid heat medium inside the heat medium pipeline per unit length, and then divide the heat medium filling amount by the mass of liquid heat medium in the pipeline per unit length. Three times the calculated result is the length of the heat medium pipeline of the radiator. L c Value; calculation formula is:

[0057] In the formula, ρ is the density of liquid heat medium, kg / m3; d is the inner diameter of the heat medium pipeline, m; According to the design size of the retaining wall and the length of the heat medium pipeline of the radiator, determine the spacing of the U-shaped coils inside the retaining wall; The calculation method in step S8 includes: Length of heat medium pipeline of geothermal collector L e 1.2 times the length of the radiator heat medium pipeline; According to the design size of the micropile and the length of the geothermal collector pipeline, the spacing of the spiral coils inside the micropile is determined.

[0058] The present invention also provides an operation control method of a temperature-resistant and frost-resistant retaining wall structure, which is specifically as follows: The PLC controller 32 pre-sets three temperature control thresholds, including a lower limit value, a middle value, and an upper limit value, and the relationship between the three is lower limit value < middle value < upper limit value.

[0059] The PLC controller 32 has 4 built-in commands, including: The first type of command: start the pressure converter 221 and set the flow regulator 222 to the rated flow value of the heat medium.

[0060] The second type of command: increasing the heat medium flow rate through the flow regulator 222, and adjusting it so that all the heat medium participates in the circulation.

[0061] The third type of command: reducing the heat medium flow rate through the flow regulator 222 and adjusting it to the rated heat medium flow rate value.

[0062] The fourth type of command: closing the pressure converter 221 and the flow regulator 222 .

[0063] The PLC controller 32 has a dynamic operation control function. The control content and method are that the PLC controller 32 collects the monitoring value of the temperature sensor 31 in the backfill 5 of the retaining wall 12 once every hour.

[0064] 1) When the monitoring value of the temperature sensor 31 in the backfill 5 of the retaining wall 12 is equal to or lower than the middle value, that is, when the retaining wall 12 is at risk of freezing damage, the PLC controller 32 executes the first type of command, and the geothermal energy conversion system 2 starts to supply heat.

[0065] 2) When the monitoring value of the temperature sensor 31 in the backfill 5 of the retaining wall 12 is equal to or lower than the lower limit value, the PLC controller 32 executes the second type of command to make the heating capacity of the geothermal energy conversion system 2 reach the maximum capacity.

[0066] 3) When the monitoring value of the temperature sensor 31 in the backfill 5 of the retaining wall 12 increases from the lower limit value to above the middle value, the PLC controller 32 executes the third type of command to make the heating capacity of the geothermal energy conversion system 2 at the average capacity state.

[0067] 4) When the monitoring value of the temperature sensor 31 in the backfill 5 of the retaining wall 12 is higher than the upper limit value, that is, when the risk of freezing damage to the retaining wall 12 has been eliminated, the PLC controller 32 executes the fourth type of command, and the geothermal energy conversion system 2 stops heating.

[0068] Through the above intelligent dynamic control process, the temperature of the backfill 5 of the retaining wall body 1 is controlled within a preset threshold range.

[0069] Preferably, the low thermal conductivity material of the outer protective layer 13 of the retaining wall 12 is polystyrene beads used in the construction field, and the amount added is preferably such that the thermal conductivity of the concrete is reduced by 20%.

[0070] Preferably, the high thermal conductivity material of the inner protective layer 14 of the retaining wall 12 is aluminum oxide beads used in the industrial field, and the amount of the beads added is preferably such that the thermal conductivity of the concrete is increased by 20%.

[0071] Preferably, the heat medium pipeline is a copper tube or aluminum tube with a wall thickness of 0.5 to 1.0 mm, which can be flexibly made into different forms and sizes according to scene conditions.

[0072] Preferably, the heat medium has a low-pressure boiling point below 0°C, a high-pressure freezing point below the atmospheric temperature, and is an alcohol or alkane refrigerant with a large latent heat of phase change.

[0073] Preferably, the pressure conversion range of the pressure converter 221 is: low pressure 0-50Pa, high pressure 1.0-1.5Mpa.

[0074] Preferably, the geothermal energy conversion system 2 (mainly the geothermal energy converter 22) is installed in a cabinet 6, and a base is provided at the bottom of the cabinet 6, which can be fixedly connected to the ground at the location to be installed to fix the cabinet 6, wherein the cabinet 6 is fixed at a position near the radiator 23 according to the requirements of the application scenario.

[0075] Preferably, the heat load coefficient is determined according to the wind speed value at the location. When in the leeward position and the wind speed is 0-4 m / s, the heat load coefficient is 1.1; when the wind speed is 4-8 m / s, the heat load coefficient is 1.2; when in the windward position and the wind speed is above 8 m / s, the heat load coefficient is 1.3.

[0076] Preferably, in the temperature control threshold of the PLC controller 32, the lower limit is taken as the average temperature of the natural fill 5 during the freezing period, the middle value is taken as 1 / 2 of the average temperature of the natural fill 5 during the freezing period, and the upper limit is taken as 0°C.

[0077] The present invention also provides a construction method of a frost-resistant temperature-controlled retaining wall structure, comprising the following steps: Drilling holes into the foundation 4 below the location of the retaining wall 12 to be constructed to form vertical pile holes; The micro pile 11 is constructed, and the geothermal energy collector 21 is wound around the outer wall of the micro pile 11, so that the bottom of the micro pile 11 extends to the bearing layer of the foundation 4 and the upper end extends to above the foundation 4, so that the geothermal energy collector 21 absorbs the geothermal energy in the foundation 4; the lower 2 / 3 part of the micro pile 11 is inserted into the pile hole, and the upper 1 / 3 part extends to the inside of the retaining wall 12, forming an integral stable structure with the retaining wall 12; the specific structure of the micro pile 11 can refer to the above description, when the seamless steel pipe 111 is inserted into the pile hole, concrete is poured, and at the same time, the heat medium pipeline connected to the geothermal energy integrator is led out to the outside of the pile hole or above the ground surface; Construct the retaining wall 12, insert the upper part of the micropile 11 into the retaining wall 12, and combine the micropile 11 and the retaining wall 12 to form an integral structure; the width of the retaining wall 12 is greater than about 5 times the diameter of the pile hole; An inner protective layer 14 and an outer protective layer 13 are constructed on both sides of the retaining wall 12, respectively, so that a high thermal conductivity material is mixed into the inner protective layer 14, and a low thermal conductivity material is mixed into the outer protective layer 13; the inner protective layer 14 and the outer protective layer 13 can be constructed after the construction of the retaining wall 12 is completed; when constructing the inner protective layer 14, the radiator 23 can be constructed together, or a space for installing the radiator 23 is reserved in the inner protective layer 14, so as to facilitate the installation of the radiator 23 at a later stage; the thermal conductive material is mixed in a certain weight ratio when constructing the inner protective layer 14 and the outer protective layer 13; Install the geothermal energy converter 22 and the radiator 23, so that the radiator 23 is installed inside the inner protective layer 14, so that the thermal energy converter converts the gaseous heat medium from a low-pressure state to a high-pressure state, and can also adjust the flow rate of the liquid heat medium and reduce the heat medium pressure, so that the radiator 23 dissipates the geothermal energy into the inner protective layer 14, and the geothermal energy collector 21, the geothermal energy converter 22 and the radiator 23 are interconnected to form a closed circulation loop, so that the closed circulation loop is a vacuum environment and is filled with heat medium, so that the geothermal energy is dissipated into the inner protective layer 14, so as to increase the input heat of the fill 5 and the temperature of the retaining wall 12; A temperature sensor 31 is provided in the backfill 5 of the retaining wall 12, and the temperature sensor 31 is electrically connected to the PLC controller 32, so that the PLC controller 32 controls the operation of the geothermal energy converter 22 according to the received temperature information, so as to regulate the temperature of the retaining wall body 1 and the input heat of the backfill 5. A plurality of mounting holes can be preset at the backfill 5 of the retaining wall 12, and a plurality of temperature sensors 31 can be installed in the mounting holes at different positions, so as to measure or monitor the internal temperature of the backfill 5 in real time.

[0078] Compared with the prior art, the technical progress achieved by the present invention is at least: (1) The frost-heaving resistant temperature-controlled retaining wall 12 is a multifunctional composite retaining structure that has both mechanical bearing and thermal control functions, and the two functions do not interfere with each other. In winter, when the temperature drops and the soil behind the retaining wall 12 shows a tendency to frost heave, the heat energy conversion system collects geothermal energy and converts it into a high-quality artificial heat source, and actively transfers heat to the soil behind the retaining wall 12, strictly controlling the soil temperature above 0°C, that is, maintaining the soil in a non-frozen state, directly and completely eliminating the frost heave force, and fundamentally solving the frost damage problem of the retaining wall 12, which is more proactive and effective.

[0079] (2) The geothermal energy conversion system 2 is a special-shaped heat pump specially designed for the retaining wall 12. It adopts phase change heat transfer, with a large heat exchange temperature difference, high geothermal energy collection efficiency, and high heating temperature. The geothermal energy conversion system 2 is a closed circulation system, which is not affected by various adverse environmental conditions such as external atmospheric temperature, humidity, and foundation 4 moisture content. It has a long service life, good durability, and low maintenance workload.

[0080] (3) The geothermal energy conversion system 2 can be driven by a small off-grid photovoltaic or wind power generation system, which is green and low-carbon. It is controlled by the intelligent control system 3 and dynamically adjusts the operation mode according to the measured temperature of the backfill 5 of the retaining wall 12. It does not require manual supervision and has the functions of automatic monitoring, intelligent decision-making, and emergency response. Therefore, the retaining wall 12 of the present invention is a green, intelligent, frost-resistant, temperature-controlled retaining wall structure that collects, improves, converts, and transports low-grade geothermal energy on the surface.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A temperature-controlled frost-resistant retaining wall structure, characterized in that: include: The retaining wall body, with the upper part located at the top of the foundation and the lower part extending into the foundation, is used to support unstable cutting slopes on both sides of traffic lines, roadbed widening of mountain railways and highways, and the edge of building foundations; A geothermal energy conversion system is connected to the retaining wall body and is used to absorb geothermal energy, convert the gaseous heat medium from a low-pressure state to a high-pressure state, and is also used to adjust the flow of liquid heat medium and reduce the heat medium pressure and to dissipate the geothermal energy into the retaining wall body to increase the temperature of the retaining wall body and the heat of the fill; The intelligent control system is electrically connected to the geothermal energy conversion system, and is used to monitor the temperature of the backfill at the rear of the retaining wall body, and dynamically and intelligently control the operation of the geothermal energy conversion system according to the change of the backfill temperature, so as to control the backfill temperature of the retaining wall body within a preset threshold range, thereby preventing the backfill from cooling and freezing to form frost heave disease.

2. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 1, characterized in that: The retaining wall body comprises: The micro pile is arranged vertically with the lower end extending to the foundation bearing layer and the upper end extending above the foundation, and the micro pile comprises a seamless steel pipe and a grouting layer arranged inside and outside the seamless steel pipe; A retaining wall is placed on the upper end of the foundation, the upper ends of the micropiles are inserted into the retaining wall, and the retaining wall and the micropiles are fixedly connected to each other; An outer protective layer connected to the side of the retaining wall facing away from the fill, and used to protect the side of the retaining wall facing away from the fill; The inner protective layer is connected to the side of the retaining wall close to the fill and is used to protect the side of the retaining wall close to the fill. The fill is located outside the inner protective layer. The area on the side of the retaining wall close to the inner protective layer is defined as the rear of the retaining wall.

3. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 2, characterized in that: The thickness of the outer protective layer is not less than 5 cm, the thickness of the inner protective layer is not less than 10 cm, the outer protective layer is mixed with low thermal conductivity material, and the inner protective layer is mixed with high thermal conductivity material.

4. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 2, characterized in that: The geothermal energy conversion system comprises: A geothermal energy collector connected to the outer wall of the lower part of the micropile, the geothermal energy collector is used to convert the liquid heat medium inside it into a low-pressure gas state to absorb the geothermal energy in the foundation, and the geothermal energy collector includes a plurality of spiral coils; A geothermal energy converter, connected to the geothermal energy collector, is used to convert the gaseous heat medium from a low-pressure state to a high-pressure state to increase the temperature and heat flux density of the geothermal energy, and is also used to adjust the flow rate of the liquid heat medium and reduce the heat medium pressure; A radiator is connected to the geothermal energy converter and is disposed inside the inner protective layer. It is used to convert high-pressure gaseous heat medium into liquid so as to dissipate geothermal energy into the inner protective layer to increase the temperature of the inner protective layer and the heat of the fill. The radiator includes a plurality of U-shaped coils.

5. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 4, characterized in that: The geothermal energy converter comprises: A pressure converter, the inlet of which is connected to the outlet of the geothermal energy collector, and the outlet of which is connected to the inlet of the radiator. The pressure converter is used to convert the input gaseous heat medium from a low-pressure state to a high-pressure state. The inlet and outlet of the pressure converter respectively produce low-pressure suction and high-pressure ejection effects; A flow regulator, the inlet of which is connected to the outlet of the radiator, and the outlet of which is connected to the inlet of the geothermal energy collector. The flow regulator is used to adjust the flow of liquid heat medium and reduce the pressure of heat medium. The geothermal energy collector, the pressure converter, the radiator and the flow regulator are connected to each other end to end through a heat medium pipeline to form a closed circulation loop. The closed circulation loop is a vacuum environment and is filled with heat medium to dissipate the geothermal energy into the inner protective layer to increase the input heat and temperature of the fill.

6. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 5, characterized in that: The geothermal energy converter also includes: A power supply system, the power output ends of which are electrically connected to the pressure converter and the flow regulator, respectively, and are used to supply power respectively; Among them, the power supply system is one of a municipal power supply system, a photovoltaic power supply system, and a wind-photovoltaic complementary power supply system.

7. A temperature-controlled frost-resistant retaining wall structure as claimed in claim 5, characterized in that: The intelligent control system comprises: A temperature sensor is arranged inside the backfill of the retaining wall body and is used to monitor the backfill temperature in real time; A PLC controller is electrically connected to the temperature sensor and the pressure converter and the flow regulator of the geothermal energy conversion system respectively, and dynamically and intelligently controls the operation of the geothermal energy conversion system according to the received temperature information, so as to adjust the input heat and temperature of the backfill of the retaining wall body; The PLC controller pre-sets three temperature control thresholds, including a lower limit, an intermediate value, and an upper limit, the temperature relationship of the three being lower limit < intermediate value < upper limit, the lower limit being the average temperature of the fill in the freezing period in the natural environment, the intermediate value being 1 / 2 of the average temperature during the freezing period, and the upper limit being 0°C; The PLC controller is provided with four types of commands, including: The first type of command: starting the pressure converter and setting the flow regulator to the rated flow value of the heat medium; The second type of command: increasing the heat medium flow rate through the flow regulator to adjust the heat medium to fully participate in the circulation; The third type of command: reducing the heat medium flow rate through the flow regulator to adjust it to the rated flow rate value of the heat medium; The fourth type of command: closing the pressure converter and the flow regulator; When the fill temperature monitoring value is equal to or lower than the middle value, the PLC controller executes the first type of command; when the fill temperature monitoring value is equal to or lower than the lower limit value, the PLC controller executes the second type of command; when the fill temperature monitoring value increases from the lower limit value to above the middle value, the PLC controller executes the third type of command; when the fill temperature monitoring value is higher than the upper limit value, the PLC controller executes the fourth type of command; through the intelligent dynamic control process, the fill temperature at the rear of the retaining wall body is controlled within a pre-set threshold range.

8. A design method for a temperature-controlled frost-resistant retaining wall structure according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Determine the initial temperature and thermal physical parameters of the frost heave strata and stable strata through on-site thermal response tests and indoor tests, and calculate the geothermal flux density and heat storage level of the stable strata; S2: According to the relevant design specifications of retaining walls and micropiles, combined with the design load and foundation conditions, the composite structure design is carried out according to the rigid connection between the retaining wall and the micropiles as an integral elastic foundation beam, including the height and width of the retaining wall, and the length, diameter, spacing, thickness and diameter of the micropiles; S3: Divide the retaining wall into several retaining wall sub-units according to the number of micro-piles. According to the typical meteorological data corresponding to the frost heave disease of retaining walls in previous years, calculate the hourly heat load when the backfill temperature of each retaining wall sub-unit is controlled above the target value, and determine the average and maximum heat load values. S4: Compare the heat storage level of the stable stratum with the average heat load of the retaining wall to check the design value of the micropile length; S5: Determine the rated flow value and charging amount of the heat medium of the geothermal energy conversion system; S6: Select the model of pressure converter and flow regulator according to the heat medium filling amount; S7: Determine the heat medium pipe length of the radiator and the U-shaped coil layout plan; S8: Determine the length of the heat medium pipeline and the spiral coil scheme of the geothermal energy collector; S9: Calculate the system power consumption based on the power consumption of the pressure converter and the flow regulator, and match the power supply with the corresponding power supply capacity.

9. A design method for a temperature-controlled frost-resistant retaining wall structure as claimed in claim 8, characterized in that: The calculation method in the above step S3 includes: 1) Combined with the target value of fill temperature control behind the retaining wall T 0. Hourly air temperature T a , surface comprehensive heat transfer coefficient h c , calculate the air convection heat exchange between the retaining wall surface and the top of the backfill behind the wall Q c ; The calculation formula is: In the formula, Q c is the cumulative value of air convection heat transfer, kJ; q c is the hourly value of air convection heat transfer, kJ; h c is the comprehensive heat transfer coefficient of the surface, W / (㎡·℃), A is the area of ​​the retaining wall and the side of the fill, m 2 ; T 0 is the temperature control target value of the backfill of the retaining wall body, °C; T a is the air temperature, °C; 2) Combined with solar radiation heat conversion coefficient h r , calculate the surface radiation heat gain Q r ; The calculation formula is: In the formula, Q r is the cumulative value of solar radiation heat transfer, kJ; q r is the hourly value of solar radiation heat transfer, kJ; h c is the installation heat transfer coefficient, W / (m 2 ℃), A is the area of ​​the retaining wall and the side of the fill, m 2 ; T 0 is the temperature control target value of the backfill of the retaining wall body, °C; T a is the air temperature, °C; 3) Multiply the sum of air convection heat exchange and radiation heat gain by the heat load coefficient k , calculate the hourly heat load time history curve q , calculate and determine the average heat load q ave With the maximum value q max ; The calculation formula is: In the formula, k is the heat load coefficient; t is time, h; In the above step S4, the verification method of the design value of the pile length of the micropile is that if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall is less than or equal to the design value of the pile length in S2, the design value remains unchanged; if the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall is greater than the design value of the pile length in S2, the design value is increased to the ratio of the thermal reserve level of the stable stratum to the average value of the heat load of the retaining wall; The calculation method in step S5 above includes: Determine the rated flow value of the heat medium m 0, calculated by dividing the average heat load by the latent heat of phase change per unit mass of heat medium; the calculation formula is: In the formula, c is the latent heat of phase change of heat medium, kJ / kg; Determine the heat medium charge m max , the calculation method is the maximum heat load divided by the latent heat of phase change per unit mass of heat medium; the calculation formula is: 。 10. The design method of a temperature-controlled frost-resistant retaining wall structure according to claim 8, characterized in that: The calculation method in step S7 includes: According to the density of liquid heat medium and the inner diameter of heat medium pipeline, calculate the mass of liquid heat medium inside the heat medium pipeline per unit length, and then divide the heat medium filling amount by the mass of liquid heat medium in the pipeline per unit length. Three times the calculated result is the length of the heat medium pipeline of the radiator. L c Value; calculation formula is: In the formula, ρ is the density of liquid heat medium, kg / m 3 ; d is the inner diameter of the heat medium pipeline, m; According to the design size of the retaining wall and the length of the heat medium pipeline of the radiator, determine the spacing of the U-shaped coils inside the retaining wall; The calculation method in step S8 includes: Length of heat medium pipeline of geothermal collector L e 1.2 times the length of the radiator heat medium pipeline; According to the design size of the micropile and the length of the geothermal collector pipeline, the spacing of the spiral coils inside the micropile is determined.

Images