A method for preventing water accumulation in a roadbed, a structure, and a calculation method for heating temperature

Abstract

The present invention relates to the technical field of subgrade protection in frozen soil areas, and discloses a method for preventing water accumulation in subgrade, a structure and a calculation method for heating temperature. The calculation of heating temperature includes: obtaining the months with a monthly average temperature greater than 0°C and the total difference between evaporation capacity and precipitation; obtaining the first daily water infiltration volume; according to the months with a monthly average temperature greater than 0°C, the total difference between evaporation capacity and precipitation, the first daily water infiltration volume, and combining with the parameters of the water accumulation prevention structure, calculating the surface evaporation loss, calculating the saturated vapor pressure on the surface of the heating drainage ditch in the water accumulation prevention structure according to the surface evaporation loss, and calculating the heating temperature by using the saturated vapor pressure. The water accumulation prevention structure collects, blocks and evaporates the freeze-thaw water on the mountainside side or slope side, alleviates the serious problem of road-side water accumulation, ensures road stability, prevents subgrade diseases from occurring, extends the service life of the road, and contributes to the high-quality construction of cold region road projects.

Description

Technical Field

[0001] The present invention relates to the technical field of subgrade protection in frozen soil areas, and particularly relates to a method for preventing water accumulation in subgrades, a structure, and a calculation method for heating temperature. Background Art

[0002] The extreme climatic conditions on the Qinghai-Tibet Plateau, especially factors such as low temperature, high-frequency freeze-thaw cycles, and strong ultraviolet radiation, pose huge challenges to the construction and operation of highways in frozen soil environments. Highway construction has changed the original topography and blocked the original surface drainage system, cutting off the natural drainage channels, thus causing water to accumulate in local areas; at the same time, the strong heat absorption characteristics of highway asphalt pavements have led to a continuous decline in the upper limit of permafrost areas, increasing the internal meltwater of subgrades and further exacerbating the water accumulation effect. Especially in the warm season, the problem of roadside water accumulation on highways is particularly serious, especially in sections on the mountainside or slope side. Snowmelt water, groundwater, and freeze-thaw water on the mountainside are more likely to accumulate on the roadside, making the phenomenon of subgrade water accumulation more prominent. Water accumulation on the roadside of subgrades on the mountainside or slope side in permafrost areas, on the one hand, water accumulation will enhance the freeze-thaw cycle effect, exacerbating the resulting frost heave and thaw settlement phenomena; on the other hand, hydrothermal migration will accelerate the degradation of permafrost, ultimately leading to problems such as subgrade settlement, cracks, and waves on highways. Therefore, effective measures must be taken to control the problem of roadside water accumulation in permafrost areas to reduce the damage of accumulated water to subgrades.

[0003] The current "Highway Drainage Design Specification" (JTG / T D33-2012) uses water retaining dams and drainage berms to intercept or squeeze out the hillside water collection outside the subgrade range, but does not actually drain the water flow and eliminate its influence, and the harm caused by water accumulation still exists. Patent document CN115807367A discloses a solar-heated seasonal antifreeze and drainage subgrade and its construction method, proposing a composite subgrade drainage method with heating and moisture-absorbing geotextiles arranged inside the subgrade; patent document CN113026462A discloses a temperature control structure applicable to subgrades and slope engineering in permafrost areas, both focusing on internal drainage of subgrades and unable to effectively solve the problem of freeze-thaw water accumulation on the roadside in the warm season, and neither calculates nor evaluates the drainage effect.

[0004] Currently, in order to solve the problem of freeze-thaw water accumulation on the roadside of subgrades on the mountainside or slope side in permafrost areas, a water accumulation prevention structure is arranged on the mountainside or slope side of the subgrade in permafrost areas. Part of the freeze-thaw water in the active layer of the frozen soil area in the warm season converges into the water accumulation prevention structure, and the water accumulation prevention structure evaporates the accumulated water by heating, which is an effective treatment method, but there is no method in the prior art on how to calculate the heating temperature of the water accumulation prevention structure to achieve effective evaporation of the accumulated water. Summary of the Invention

[0005] The object of the present invention is to solve the problem that in the prior art, there is no method for calculating the heating temperature when heating and evaporating the accumulated water on the roadbed and the roadside of the roadbed, and to provide a method for preventing water accumulation on the roadbed, a structure, and a method for calculating the heating temperature.

[0006] In a first aspect, the present invention provides a method for calculating the heating temperature of a roadbed water accumulation prevention structure, including the following steps:

[0007] Obtain the months with a monthly average temperature greater than 0 °C and the total sum of the difference between the evaporation capacity and the precipitation in the months with a monthly average temperature greater than 0 °C throughout the year;

[0008] Obtain the first daily seepage volume, which is the seepage volume of the water entering the water accumulation prevention structure;

[0009] According to the months with a monthly average temperature greater than 0 °C, the total sum of the difference between the evaporation capacity and the precipitation, and the first daily seepage volume, combined with the parameters of the water accumulation prevention structure, calculate the surface evaporation loss of the water accumulation prevention structure. The calculation formula for the surface evaporation loss is:

[0010]

[0011] In the formula, H is the surface evaporation loss, with the unit of mm / d, Q 1 is the first daily seepage volume, with the unit of m 3 / d, B 1 is the average width of the heating drainage ditch in the water accumulation prevention structure, with the unit of m, is the water collection length of the heating drainage ditch in the water accumulation prevention structure along the ditch length direction, with the unit of m, is the number of months with a monthly average temperature greater than 0 °C, c is the total sum of the difference between the evaporation capacity and the precipitation in the months with a monthly average temperature greater than 0 °C throughout the year, with the unit of mm;

[0012] Calculate the saturated vapor pressure on the surface of the heating drainage ditch in the water accumulation prevention structure according to the surface evaporation loss, and calculate the heating temperature using the saturated vapor pressure. The calculation formula for the heating temperature is:

[0013]

[0014] In the formula T is the heating temperature on the surface of the heating drainage ditch in the water accumulation prevention structure, with the unit of °C, P m is the saturated vapor pressure, with the unit of Pa, A, B, C is the Antoine constant.

[0015] In the above technical solution, by obtaining the months with a monthly average temperature greater than 0°C, the total difference between the evaporation capacity and precipitation in the months with a monthly average temperature greater than 0°C throughout the year, and the first daily water seepage volume of the water entering the waterproof moisture accumulation structure, where the water entering the waterproof moisture accumulation structure includes the water converging from the active layer of the permafrost area to the waterproof moisture accumulation structure, the surface evaporation loss through the waterproof moisture accumulation structure is calculated by combining the data. The saturation vapor pressure on the surface of the heating drainage ditch in the waterproof moisture accumulation structure is calculated based on the surface evaporation loss, and the heating temperature is calculated using the saturation vapor pressure. When the waterproof moisture accumulation structure is set on the mountainside or slope side of the roadbed, by adopting the above technical solution of the present invention, the heating temperature of the waterproof moisture accumulation structure can be quickly and accurately calculated, which is used to evaporate the accumulated water by heating, effectively solving the problem of the accumulation of thawing water in the warm season in the permafrost area on the roadside and avoiding the harm caused by the moisture accumulation to the roadbed.

[0016] As a preferred solution of the present invention, the implementation method for obtaining the total difference between the evaporation capacity and precipitation is as follows:

[0017] Step S11: Based on the meteorological data of the permafrost area, count the months with a monthly average temperature greater than 0°C throughout the year;

[0018] Step S12: Obtain the monthly evaporation capacity and monthly precipitation data for the months with a monthly average temperature greater than 0°C;

[0019] Step S13: Calculate the total difference between the evaporation capacity and precipitation throughout the year according to the monthly evaporation capacity and monthly precipitation data. The calculation formula for the total difference between the evaporation capacity and precipitation is:

[0020]

[0021] Where PE i is the monthly evaporation capacity, with the unit of mm, P i is the monthly precipitation, with the unit of mm, is the number of months with a monthly average temperature greater than 0°C.

[0022] As a preferred solution of the present invention, the implementation method for obtaining the first daily water seepage volume is as follows:

[0023] Step S21: Based on the stratum and hydrological data of the permafrost area, obtain the first soil layer permeability coefficient and the first soil layer hydraulic gradient of the active layer where the water enters the waterproof moisture accumulation structure;

[0024] Step S22: Calculate the first daily water seepage volume of the water entering the waterproof moisture accumulation structure based on the first soil layer permeability coefficient and the first soil layer hydraulic gradient. The calculation formula for the first daily water seepage volume is:

[0025]

[0026] In the formula, is the permeability coefficient of the first soil layer, is the hydraulic gradient of the first soil layer, is the cross-sectional area of the water passage, A 1 = h 1 × L , with the unit of square meter 。

[0027] As a preferred solution of the present invention, the calculation formula for the average width of the heating drainage ditch is:

[0028]

[0029] In the formula B 0 is the bottom width of the heating drainage ditch, α is the reciprocal of the slope rate of the left side wall of the heating drainage ditch, β is the reciprocal of the slope rate of the right side wall of the heating drainage ditch.

[0030] As a preferred solution of the present invention, the calculation formula for the saturated vapor pressure is:

[0031]

[0032] Where P is the relevant air pressure value, with the unit of Pa; V m represents the daily average wind speed, with the unit of m / s.

[0033] In a second aspect, the present invention provides a method for preventing water accumulation on the mountainside side or slope side of the roadbed in the permafrost region. A water accumulation prevention structure is provided on the mountainside side or slope side of the roadbed. A heating drainage ditch is provided in the water accumulation prevention structure. A permeable layer is provided on the side of the water accumulation prevention structure away from the roadbed for collecting the water in the permafrost region into the heating drainage ditch; an electric heating film is provided on the side of the water accumulation prevention structure close to the roadbed for heating the heating drainage ditch;

[0034] The method includes monitoring the temperature and relative humidity at the bottom of the heating drainage ditch;

[0035] When the temperature at the bottom of the heating drainage ditch ≥ 0°C and the relative humidity ≥ 60%, start the electric heating film for heating to make the temperature at the bottom of the heating drainage ditch reach the heating temperature calculated by the above method;

[0036] Maintain the constant temperature heating state of the heating drainage ditch to heat and evaporate the water until the relative humidity at the bottom of the heating drainage ditch < 60%, and stop heating.

[0037] In the above technical solution, a waterproof accumulation structure is provided on the mountainside side or the slope side of the roadbed, a permeable layer is provided on the side far from the roadbed, and the snowmelt water, rainwater and subsurface freeze-thaw water on the mountainside side or the slope side flow into the heating drainage ditch through the permeable layer, and the heating drainage ditch is heated and evaporated by the electric heating film close to the roadbed; when it is monitored that the temperature at the bottom of the heating drainage ditch is ≥0°C and the relative humidity is ≥60%, the electric heating film is started to be heated so that the temperature at the bottom of the heating drainage ditch reaches the heating temperature calculated by the above method, which can effectively treat the accumulated water on the roadbed and prevent the harm caused by water accumulation to the roadbed.

[0038] As a preferred solution of the present invention, the electric heating film is selected from at least one of a graphene electric heating film, a silica gel electric heating film or a carbon fiber heating film.

[0039] As a preferred solution of the present invention, the electric heating film satisfies a waterproof grade of ≥IPX8, a thickness of ≥0.25 mm, a power density of 80 - 200 W / m 2 , an electrothermal conversion efficiency of ≥60%, and a heating uniformity of ≤±5°C. Preferably, the thickness of the electric heating film is 0.25 - 0.6 mm, and the power density is 100 W / m 2 or 150 W / m 2 .

[0040] In a third aspect, the present invention provides a waterproof accumulation structure for a roadbed on the mountainside side or the slope side in a permafrost area. The waterproof accumulation structure includes a permeable layer and a heating layer. The permeable layer is provided on the side far from the roadbed, and the heating layer is provided on the side close to the roadbed. Turf is arranged on the permeable layer and the heating layer. The heating layer includes an electric heating film, a heat insulation layer and a waterproof layer arranged from top to bottom; the permeable layer and the heating layer enclose a semi-open heating drainage ditch, and a temperature sensor and a humidity sensor are arranged at the bottom of the heating drainage ditch corresponding to the heating layer.

[0041] As a preferred solution of the present invention, the cross-section of the waterproof accumulation structure is an inverted trapezoid structure, the cross-section of the heating drainage ditch is an inverted trapezoid structure, the two side edges of the waterproof accumulation structure are respectively a first surface and a third surface, the bottom edge is a second surface, the second surface connects the first surface and the third surface, the side far from the roadbed is the first surface, the side close to the roadbed is the third surface, the permeable layer is provided on the first surface, and the heating layer is provided on the second surface and the third surface. The slope ratio of the first surface is not greater than 1:2, and the slope ratio of the third surface is not greater than 1:1.

[0042] As a preferred embodiment of the present invention, the permeable layer includes a filter layer and a permeable membrane layer arranged in sequence. The filter layer includes a coarse sand layer, a medium sand layer, and a fine sand layer arranged in sequence, and the coarse sand layer is arranged away from the roadbed; the thickness of the coarse sand layer is 8 - 30 cm, the thickness of the medium sand layer is 10 - 20 cm, the thickness of the fine sand layer is 10 - 20 cm, the particle size of the sand and gravel in the coarse sand layer is 5 - 20 mm, the particle size of the sand and gravel in the medium sand layer is 1 - 5 mm, and the particle size of the sand and gravel in the fine sand layer is 0.25 - 1 mm.

[0043] As a preferred embodiment of the present invention, the electric heating film is powered by a solar energy storage system, and the solar energy storage system includes a solar panel, an energy storage device, a controller, and an inverter.

[0044] As a preferred embodiment of the present invention, the height from the bottom end of the heating drainage ditch to the upper limit of permafrost is a defined height, and the method for determining the defined height is as follows:

[0045] Based on the sum of the differences between the evaporation capacity and precipitation in months with an average monthly temperature greater than 0°C throughout the year and the parameters of the water accumulation prevention structure, the second daily seepage volume is calculated. The second daily seepage volume is the seepage volume of water in the active layer of the permafrost area that does not enter the water accumulation prevention structure. The calculation formula for the second daily seepage volume is:

[0046]

[0047] Where is the second daily water collection volume, with the unit of m 3 / d, l is the distance from the heating drainage ditch to the toe of the roadbed slope, with the unit of m;

[0048] Based on the geological data of the permafrost area, the second soil layer permeability coefficient and the second soil layer hydraulic gradient of the active layer where water does not enter the water accumulation prevention structure are obtained;

[0049] Using the second soil layer permeability coefficient, the second soil layer hydraulic gradient, and the second daily seepage volume, the defined height is calculated. The calculation formula for the defined height is:

[0050]

[0051] Where is the defined height, with the unit of mm, is the second soil layer hydraulic gradient, is the second soil layer permeability coefficient.

[0052] Compared with the prior art, the beneficial effects of the present invention are:

[0053] 1. The present invention provides a method for calculating the heating temperature of a roadbed waterproof moisture accumulation structure. By obtaining the months with a monthly average temperature greater than 0°C, the total difference between the evaporation force and precipitation in the months with a monthly average temperature greater than 0°C throughout the year, and the first daily water seepage volume, the surface evaporation loss through the waterproof moisture accumulation structure is calculated by combining the data. The saturated vapor pressure on the surface of the heating drainage ditch in the waterproof moisture accumulation structure is calculated through the surface evaporation loss, and the heating temperature is calculated using the saturated vapor pressure. When a waterproof moisture accumulation structure is set on the mountainside or slope side of the roadbed, adopting the above technical solution of the present invention can quickly and accurately calculate the heating temperature of the waterproof moisture accumulation structure, which is used to evaporate the accumulated water through heating, effectively solve the problem of the accumulation of thaw-freeze water on the road side in the warm season in the permafrost area, and avoid the harm caused by moisture accumulation to the roadbed.

[0054] 2. The present invention provides a roadbed waterproof moisture accumulation structure on the mountainside or slope side in the permafrost area. A waterproof moisture accumulation structure is set on the mountainside or slope side of the roadbed. A heating drainage ditch is arranged in the waterproof moisture accumulation structure, and a permeable layer is arranged on the side far from the roadbed in the waterproof moisture accumulation structure, which is used to drain the moisture in the permafrost area to the heating drainage ditch and collect the thaw-freeze water on the mountainside or slope side in the warm season; an electric heating film is arranged on the side close to the roadbed in the waterproof moisture accumulation structure, which is impermeable and is used to heat and evaporate the heating drainage ditch, prevent the thaw-freeze water from continuing to flow towards the roadbed, heat and evaporate the collected water, and prevent the heat from transferring downward to disturb the permafrost, forming an effective water accumulation treatment system, but not solving the water accumulation problem from the source.

[0055] 3. Aiming at the problems of serious water accumulation on the road side of the existing roadbed in the permafrost area, which leads to frequent occurrence of roadbed frost heaving and thaw settlement diseases, and causes diseases such as roadbed subsidence, cracks, and waves, the present invention alleviates the problem of serious water accumulation on the road side by collecting, blocking, and evaporating the thaw-freeze water on the mountainside or slope side, ensures the road stability, prevents the occurrence of roadbed diseases, extends the service life of the road, and contributes to the high-quality construction of road projects in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic flow chart of the method for calculating the heating temperature of the roadbed waterproof moisture accumulation structure of the present invention;

[0057] Figure 2 It is a structural diagram of the waterproof moisture accumulation structure of the roadbed on the mountainside or slope side in the permafrost area in Embodiment 2;

[0058] Figure 3 It is a structural diagram of the permeable layer in the waterproof moisture accumulation structure of the roadbed on the mountainside or slope side in the permafrost area in Embodiment 2;

[0059] Figure 4 It is a structural diagram of the heating layer in the waterproof moisture accumulation structure of the roadbed on the mountainside or slope side in the permafrost area in Embodiment 2;

[0060] Markings in the figure:

[0061] 1 - Subgrade,

[0062] 21 - First active layer, 22 - Second active layer, 23 - Permafrost upper limit, 24 - Active layer boundary,

[0063] 3 - Permeable layer, 31 - Coarse sand layer, 32 - Medium sand layer, 33 - Fine sand layer, 34 - Permeable membrane layer,

[0064] 4 - Turf, 5 - Heating drainage ditch, 6 - Heating layer, 61 - Electric heating membrane, 62 - Heat insulation layer, 63 - Waterproof layer. Detailed implementation manners

[0065] The present invention will be further described in detail below in conjunction with specific embodiments. However, this should not be construed as limiting the scope of the above - mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0066] In the description of the specific embodiments of the present invention, without special explanation, the expression terms of the orientation or position relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or position relationship shown in the drawings, or the orientation or position relationship when the invention product / device / equipment is usually used. These orientation or position relationship terms are only for facilitating the description of the present invention solution or simplifying the description in the specific embodiments, facilitating technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship. Therefore, it should not be construed as a limitation to the present invention.

[0067] In addition, for terms such as "horizontal", "vertical", "hanging", "parallel", etc., it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8% of the error / deviation, more preferably within ±6% of the error / deviation, more preferably within ±5% of the error / deviation, more preferably within ±4% of the error / deviation. As long as the corresponding device / component / element is within the error / deviation range, it can still play its role in the solution of the present invention.

[0068] In addition, the expressions such as "first", "second", "third", etc. in the terms are only used to distinguish the descriptions of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0069] In addition, in the description of the embodiments of the present invention, "several", "multiple", and "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., and even can be a situation where it exceeds 9.

[0070] In addition, in the description of the technical solutions of the present invention, unless otherwise clearly specified / defined / restricted, where the terms "set", "install", "connect", "be connected", "be provided with", "lay", "arrange" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be common connection means in the art such as welding, riveting, bolting, threaded connection, etc. Such a connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0071] Embodiment 1

[0072] This embodiment provides a method for calculating the heating temperature of a subgrade waterproof accumulation structure, as Figure 1 shown, including the following steps:

[0073] Step S1, obtain the months with a monthly average temperature greater than 0°C and the total sum of the difference between the evaporation capacity and the precipitation in the months with a monthly average temperature greater than 0°C throughout the year;

[0074] In step S1, the implementation method for obtaining the total sum of the difference between the evaporation capacity and the precipitation is:

[0075] Step S11, based on the meteorological data in the permafrost region, count the months with a monthly average temperature greater than 0°C throughout the year;

[0076] Step S12, obtain the monthly evaporation capacity and monthly precipitation data for the months with a monthly average temperature greater than 0°C;

[0077] Step S13, calculate the total sum of the difference between the evaporation capacity and the precipitation throughout the year according to the monthly evaporation capacity and monthly precipitation data. The calculation formula for the total sum of the difference between the evaporation capacity and the precipitation is:

[0078]

[0079] where PE i is the monthly evaporation capacity, with the unit of mm, P i is the monthly precipitation, with the unit of mm, is the number of months with a monthly average temperature greater than 0°C. After calculation,c， If c is negative, water infiltration is not allowed.

[0080] Step S2: Obtain the first daily infiltration volume, which is the infiltration volume of water entering the waterproof moisture accumulation structure. The water entering the waterproof moisture accumulation structure includes the water converging from the active layer of the permafrost area into the waterproof moisture accumulation structure;

[0081] In step S2, the method for obtaining the first daily infiltration volume is as follows:

[0082] Step S21: Based on the stratum and hydrological data of the permafrost area, obtain the first soil layer permeability coefficient and the first soil layer hydraulic gradient of the active layer where water enters the waterproof moisture accumulation structure;

[0083] Step S22: Calculate the first daily infiltration volume of water entering the waterproof moisture accumulation structure based on the first soil layer permeability coefficient and the first soil layer hydraulic gradient. The calculation formula for the first daily infiltration volume is:

[0084]

[0085] In the formula, is the first soil layer permeability coefficient, is the first soil layer hydraulic gradient, is the cross-sectional area of the water flow, A 1 = h 1 × L , with the unit of square meters, h 1 is the water passing height of the waterproof moisture accumulation structure, with the unit of m, L is the water collection length of the heating drainage ditch in the waterproof moisture accumulation structure along the ditch length direction, that is, the longitudinal length of the heating drainage ditch. The order of the above step S1 and step S2 can be swapped or they can be carried out simultaneously.

[0086] Step S3: According to the months with a monthly average temperature greater than 0 °C, the total difference between the evaporation capacity and the precipitation, and the first daily infiltration volume, combined with the parameters of the waterproof moisture accumulation structure, calculate the surface evaporation loss of the waterproof moisture accumulation structure. The calculation formula for the surface evaporation loss is:

[0087]

[0088] In the formula, H is the surface evaporation loss, with the unit of mm / d or L / (d·m 2 ), mm / d = L / (d·m 2 ), Q 1 is the first daily infiltration volume, with the unit of m 3 / d, B 1 is the average ditch width of the heating drainage ditch in the waterproof moisture accumulation structure, with the unit of m, The water collection length of the heated drainage ditch in the water accumulation prevention structure along the ditch length direction, unit: m, is the number of months with a monthly average temperature greater than 0°C, c is the total difference between the evaporation capacity and precipitation of the months with a monthly average temperature greater than 0°C throughout the year, unit: mm. Among them, the active layer refers to the near-surface layer above the permafrost layer and within a certain depth below the ground surface in the permafrost region, which melts in the warm season and completely refreezes in the cold season. Part of the water in the active layer is collected into the water accumulation prevention structure for heating and evaporation, and part seeps into the subgrade from the bottom of the water accumulation prevention structure for natural evaporation.

[0089] Among them, the calculation formula for the average ditch width of the heated drainage ditch is:

[0090]

[0091] In the formula B 0 is the bottom width of the heated drainage ditch, α is the reciprocal of the slope rate of the left side ditch wall of the heated drainage ditch, β is the reciprocal of the slope rate of the right side ditch wall of the heated drainage ditch.

[0092] Step S4: Calculate the saturated vapor pressure on the surface of the heated drainage ditch in the water accumulation prevention structure according to the surface evaporation loss, and calculate the heating temperature using the saturated vapor pressure. The calculation formula for the saturated vapor pressure is:

[0093]

[0094] Among them P m is the saturated vapor pressure calculated according to the surface temperature of the heated drainage ditch, unit: Pa; P is the air pressure value, measured by a barometer, unit: Pa; V m represents the daily average wind speed, unit: m / s.

[0095] The calculation formula for the heating temperature is:

[0096]

[0097] In the formula T is the heating temperature on the surface of the heated drainage ditch in the water accumulation prevention structure, unit: °C, that is, the regulated temperature, A, B, C is the Antoine constant, which can be obtained from the Antoine constant handbook.

[0098] Example 2

[0099] This embodiment provides a moisture accumulation prevention structure for a roadbed on the mountainside or slope side in a permafrost area. The moisture accumulation prevention structure includes a permeable layer 3 and a heating layer 6. The permeable layer 3 is arranged close to the roadbed 1, and the heating layer 6 is arranged away from the roadbed 1. Turf 4 is laid on the permeable layer 3 and the heating layer 6. The heating layer 6 includes an electric heating film 61, a heat insulation layer 62, and a waterproof layer 63 arranged from top to bottom. The permeable layer 3 and the heating layer 6 enclose a semi-open heating drainage ditch 5, and a temperature sensor and a humidity sensor are arranged corresponding to the bottom of the heating layer 6 in the heating drainage ditch 5.

[0100] As Figures 2 - 4 , it can be seen from the figure that the moisture accumulation prevention structure is arranged on the roadside of the roadbed 1 in the permafrost area. The active layer refers to the near-surface layer above the permafrost layer in the permafrost area, within a certain depth below the ground surface, which melts in the warm season and completely refreezes in the cold season. The permafrost table 23 is between the active layer and the permafrost layer. The soil layer of the active layer will generate meltwater in the warm season. The active layer is divided into a first active layer 21 and a second active layer 22 through the active layer dividing line 24. Among them, the water in the first active layer 21 will converge along the hillside into the heating drainage ditch 5 of the moisture accumulation prevention structure. The seepage volume of this part of water is the first daily seepage volume. The water in the second active layer 22 seeps into the roadbed from the bottom of the moisture accumulation prevention structure. The daily seepage volume of the active layer is , , is the first daily seepage volume of the first active layer, is the second daily seepage volume of the second active layer; among them, the permafrost table 23 can be determined by exploration, drilling, by analyzing the soil layer characteristics at different depths in the borehole to judge the location of the permafrost upper limit, or by ground temperature observation to determine the permafrost upper limit area.

[0101] In this embodiment, the cross-section of the moisture accumulation prevention structure is an inverted trapezoidal structure. Since the permeable layer 3 and the heating layer 6 enclose a semi-open heating drainage ditch 5, the cross-section of the heating drainage ditch 5 is also an inverted trapezoidal structure. The two sides of the moisture accumulation prevention structure are the first side and the third side respectively, the bottom edge is the second side, the second side connects the first side and the third side, the side away from the roadbed 1 is the first side, the side close to the roadbed 1 is the third side, the permeable layer 3 is arranged on the first side, and the heating layer 6 is arranged on the second side and the third side. In this embodiment, the slope ratio of the first side is not greater than 1:2, and the slope ratio of the third side is not greater than 1:1.

[0102] The permeable layer 3 includes a filter layer and a permeable membrane layer 34 arranged in sequence. The filter layer includes a coarse sand layer 31, a medium sand layer 32, and a fine sand layer 33. The coarse sand layer 31 is arranged away from the roadbed 1, and the fine sand layer 33 is adjacent to the permeable membrane layer 34. The filter layer has a filtering function and sufficient water permeability, can effectively intercept pollutants, reduce the concentration of pollutants in runoff, and prevent water accumulation. The permeable layer 3 is arranged near the side of the waterproof accumulation structure to achieve effective drainage. Its main purpose is to promote the rapid discharge of water, prevent water from accumulating near the roadbed 1, and thus protect the stability and durability of the roadbed 1. The thickness of the coarse sand layer 31 is 8 - 30 cm, the thickness of the medium sand layer 32 is 10 - 20 cm, the thickness of the fine sand layer 33 is 10 - 20 cm, the particle size of the gravel in the coarse sand layer 31 is 5 - 20 mm, the particle size of the gravel in the medium sand layer 32 is 1 - 5 mm, and the particle size of the gravel in the fine sand layer 33 is 0.25 - 1 mm. In this embodiment, the thickness of the coarse sand layer 31 is 20 cm, the thickness of the medium sand layer 32 is 15 cm, and the thickness of the fine sand layer 33 is 15 cm. The permeable membrane layer 34 is a permeable geotextile, and the permeable membrane layer 34 satisfies that the unit area mass ≥ 400 g / m², the tensile strength ≥ 20 N / m, the elongation at break ≥ 50%, the CBR bursting strength ≥ 3.5 KN, the tearing strength ≥ 0.56 KN, and the vertical permeability coefficient is 1×10 -1 ~1×10 -2 cm / s. The permeable geotextile is lapped on the heating layer 6, and the lapping length is not more than 30 cm.

[0103] In this embodiment, a leveling layer is also arranged between the heating layer 6 and the soil layer. The leveling layer is laid with fine sand. The heat insulation layer 62 can reduce the influence of the heating of the heating layer 6 on the soil layer temperature. The waterproof layer 63 is a composite geotextile, and the waterproof layer 63 satisfies: the unit area mass ≥ 400 g / m², the thickness ≥ 0.5 mm, the tensile strength ≥ 20 N / m, the elongation at break ≥ 50%, the tearing strength ≥ 0.15 KN, and the hydrostatic pressure resistance ≥ 0.6 MPa / m.

[0104] In some embodiments, the electric heating film 61 is powered by a solar energy storage system, which includes solar panels, energy storage devices, controllers, inverters, etc. The solar panels convert solar energy into electrical energy and store the excess in the energy storage devices. Common energy storage devices include lithium-ion batteries, lithium iron phosphate batteries, and lead-acid batteries. The controller is responsible for managing the charging process of the solar panels to ensure that the batteries are not overcharged or over-discharged, and monitors the status of the batteries to protect the batteries from damage. At the same time, the inverter converts the direct current generated by the solar panels into alternating current to meet the power needs of equipment such as the electric heating film 61: during the day, the solar panels receive sunlight and convert it into electrical energy. Part of the electrical energy directly powers loads such as the electric heating film 61 to meet real-time power needs; the other part of the excess electrical energy is transmitted to the energy storage device through the controller for storage; at night or on cloudy days when there is insufficient light, the electrical energy in the energy storage device is converted into alternating current through the inverter to power loads such as the electric heating film 61 to ensure continuous and stable operation of the system.

[0105] In some other embodiments, the moisture accumulation prevention structure is further provided with a leakage protection device for quickly cutting off the power supply when leakage occurs. The leakage protection device can monitor the leakage current in the circuit in real time, and once it is detected that the leakage current exceeds the set value, the circuit will be cut off immediately.

[0106] The electric heating film 61 adopts a low-temperature heating film, and can be selected from at least one of graphene electric heating film, silicone electric heating film or carbon fiber heating film, preferably PET graphene electric heating film-polyester heating film. The electric heating film 61 meets the waterproof level ≥ IPX8, the thickness ≥ 0.25mm, preferably, the thickness is 0.25~0.6mm, and the power density is 80~200W / m 2 , preferably, the power density is 100W / m 2 or 150W / m 2 , electrothermal conversion efficiency ≥ 60%, heating uniformity ≤ ± 5 ℃, service life > 10 years.

[0107] In this embodiment, the height between the bottom of the heating drainage ditch and the upper limit of the permafrost is the limited height, and the method for determining the limited height is:

[0108] The second daily water seepage is calculated based on the sum of the difference between the evaporation power and precipitation in the months with an average monthly temperature greater than 0°C and the parameters of the water-proof water accumulation structure. The second daily water seepage is the water seepage in the active layer of the permafrost area that does not enter the water-proof water accumulation structure. The calculation formula for the second daily water seepage is:

[0109]

[0110] in is the daily second water volume, in m 3 / d, the second daily water inflow is the water in the second active layer, l is the distance from the heating drainage ditch to the toe of the subgrade slope;

[0111] Based on the geological data in the permafrost area, obtain the second soil layer permeability coefficient and the second soil layer hydraulic gradient of the active layer where water does not enter the water accumulation prevention structure;

[0112] Calculate the limited height using the second soil layer permeability coefficient, the second soil layer hydraulic gradient, and the second daily water seepage. The calculation formula for the limited height is:

[0113]

[0114] where is the limited height, with the unit of mm, is the second soil layer hydraulic gradient, is the second soil layer permeability coefficient. The second soil layer hydraulic gradient and the second soil layer permeability coefficient are the soil layer parameters in the second active layer.

[0115] Embodiment 3

[0116] This embodiment provides a method for preventing water accumulation on the mountainside or slope side of the subgrade in the permafrost area. Set the water accumulation prevention structure of Embodiment 2 on the mountainside or slope side of the subgrade. A heating drainage ditch is arranged in the water accumulation prevention structure. A permeable layer is arranged on the side of the water accumulation prevention structure far from the subgrade to collect the water in the permafrost area into the heating drainage ditch; an electric heating film is arranged on the side of the water accumulation prevention structure close to the subgrade to heat the heating drainage ditch;

[0117] The method includes monitoring the temperature and relative humidity at the bottom of the heating drainage ditch;

[0118] When the temperature at the bottom of the heating drainage ditch ≥ 0°C and the relative humidity ≥ 60%, start the electric heating film to heat, so that the temperature at the bottom of the heating drainage ditch reaches the heating temperature in Embodiment 1;

[0119] Maintain the constant temperature heating state of the heating drainage ditch to heat and evaporate the water until the relative humidity at the bottom of the heating drainage ditch < 60%, and stop heating.

[0120] When the temperature in the permafrost area is greater than 0°C, the ice begins to melt, and the water accumulation prevention structure collects the water into the heating drainage ditch.

[0121] When the humidity sensor shows that the relative humidity of the air in the soil pores is below 60%, it can generally be considered that there is no water accumulation in the soil. When the temperature ≥ 0°C and the relative humidity ≥ 60%, there is water accumulation, and the electric heating film is started to heat and evaporate. When the electric heating film is heated to TWhen the relative humidity ≥ 60%, maintain the constant temperature heating state. Generally, the calculated heating temperature T ≤ 25°C. According to the ground temperature monitoring data, the highest ground temperature in this area in summer can reach 30°C. Taking a 5°C margin, so the heating film T max ≤ 25°C does not affect the growth of the sod in the heated drainage ditch and the local ecosystem; when the relative humidity in the soil < 60%, stop heating.

[0122] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for calculating the heating temperature of a roadbed moisture accumulation protection structure, characterized in that: The following steps are involved: Obtain the sum of the differences between evaporation and precipitation in the months with a monthly average temperature greater than 0°C and the months with a monthly average temperature greater than 0°C throughout the year; Obtaining a first daily water seepage amount, where the first daily water seepage amount is the water seepage amount of water entering the moisture accumulating structure; According to the months with average monthly temperature greater than 0℃, the sum of the difference between evaporation power and precipitation, the first daily seepage volume, and the parameters of the moisture-proof accumulation structure, the surface evaporation loss of the moisture-proof accumulation structure is calculated. The calculation formula for the surface evaporation loss is: Where H is the surface evaporation loss, Q 1 is the first daily water seepage volume, B 1 is the average width of the heating drainage ditch in the structure to prevent moisture accumulation. To prevent moisture accumulation in the heating drainage ditch, the water collection length along the ditch length is is the number of months with a monthly average temperature greater than 0°C, c It is the sum of the difference between evaporation and precipitation in the months with an average monthly temperature greater than 0℃ throughout the year; The saturated vapor pressure on the surface of the heating drainage ditch in the anti-water accumulation structure is calculated based on the surface evaporation loss, and the heating temperature is calculated using the saturated vapor pressure. The calculation formula for the heating temperature is: In the formula T To prevent moisture accumulation in structures that heat the surface of the gutter, P m is the saturated vapor pressure, A, B, C is the Antoine constant; The water-proof moisture accumulation structure includes a water-permeable layer and a heating layer. The water-permeable layer is arranged on the side away from the roadbed, and the heating layer is arranged on the side close to the roadbed. Turf is arranged on the water-permeable layer and the heating layer. The heating layer includes an electric heating film, an insulating layer and a waterproof layer arranged from top to bottom. The water-permeable layer and the heating layer enclose a semi-open heating drainage ditch, and a temperature sensor and a humidity sensor are arranged at the bottom of the heating drainage ditch corresponding to the heating layer.

2. A method for calculating the heating temperature of a roadbed water-proof structure according to claim 1, characterized in that: The implementation method to obtain the sum of the difference between evaporation power and precipitation is: Step S11, based on the meteorological data of the permafrost region, counting the months with an average monthly temperature greater than 0°C throughout the year; Step S12, obtaining monthly evaporation power and monthly precipitation data for months with a monthly average temperature greater than 0°C; Step S13, according to the monthly evaporation power and monthly precipitation data, the total difference between the evaporation power and the precipitation for the whole year is calculated. The calculation formula for the total difference between the evaporation power and the precipitation is: in PE i is the evaporation power of the moon, P i Monthly precipitation.

3. A method for calculating the heating temperature of a roadbed water-proof structure according to claim 1, characterized in that: The method for obtaining the first daily seepage volume is: Step S21, based on the stratum and hydrological data of the permafrost area, obtaining the first soil layer permeability coefficient and the first soil layer hydraulic gradient of the active layer of the water entering the water-proof accumulation structure; the active layer refers to the near-surface layer above the permafrost layer and below the surface in the permafrost area, which shows melting in the warm season and complete refreezing in the cold season. The active layer is divided into a first active layer and a second active layer by an active layer boundary line, wherein the water in the first active layer will be collected in the heating drainage ditch of the water-proof accumulation structure, and the seepage amount of this part of water is the first daily seepage amount, and the active layer where the water enters the water-proof accumulation structure is the first active layer; Step S22, based on the permeability coefficient of the first soil layer and the hydraulic gradient of the first soil layer, the first daily water seepage amount of water entering the moisture-proof accumulation structure is calculated. The calculation formula of the first daily water seepage amount is: In the formula, is the permeability coefficient of the first soil layer, is the hydraulic gradient of the first soil layer, The cross-sectional area of ​​water 。 4. A method for calculating the heating temperature of a roadbed water-proof moisture accumulation structure according to any one of claims 1 to 3, characterized in that: The calculation formula for saturated vapor pressure is: in P is the air pressure value; V m Indicates the daily average wind speed.

5. A method for preventing moisture accumulation on the roadbed on the mountain side or slope side in permafrost areas, characterized in that: A moisture-proof accumulation structure is arranged on the mountain side or slope side of the roadbed, wherein a heating drainage ditch is arranged in the moisture-proof accumulation structure, and a permeable layer is arranged on the side of the moisture-proof accumulation structure away from the roadbed, so as to collect moisture in the permafrost area to the heating drainage ditch; an electric heating film is arranged on the side of the moisture-proof accumulation structure close to the roadbed, so as to heat the heating drainage ditch; The method includes monitoring the temperature and relative humidity at the bottom of the heated drain; When the temperature at the bottom of the heating drainage ditch is ≥0°C and the relative humidity is ≥60%, the electric heating film is started for heating, so that the temperature at the bottom of the heating drainage ditch reaches the heating temperature calculated by the method for calculating the heating temperature of a roadbed moisture accumulation structure according to any one of claims 1 to 4; The heating drain ditch is maintained in a constant temperature heating state until the relative humidity at the bottom of the heating drain ditch is less than 60%, and then the heating is stopped.

6. A method for preventing moisture accumulation on a roadbed on a mountain side or a slope side in a permafrost region according to claim 5, characterized in that: The electric heating film meets the requirements of waterproof grade ≥ IPX8, thickness ≥ 0.25mm, power density 80~200W / m 2 , electrothermal conversion efficiency ≥ 60%, heating uniformity ≤ ± 5℃.

7. A moisture-proof accumulation structure for a roadbed on a mountain side or slope side in a permafrost region, characterized in that: A method for preventing moisture accumulation in a roadbed on a mountainside or slope side in a permafrost region as described in any one of claims 5-6, wherein the moisture accumulation structure comprises a permeable layer and a heating layer, the permeable layer is arranged on the side away from the roadbed, and the heating layer is arranged on the side close to the roadbed, turf is arranged on the permeable layer and the heating layer, and the heating layer comprises an electric heating film, an insulating layer and a waterproof layer arranged from top to bottom; the permeable layer and the heating layer enclose a semi-open heating drainage ditch, and a temperature sensor and a humidity sensor are arranged at the bottom of the heating drainage ditch corresponding to the heating layer.

8. The moisture-proof accumulation structure for roadbed on the mountain side or slope side in permafrost areas according to claim 7, characterized in that: The permeable layer includes a filter layer and a permeable membrane layer arranged in sequence, the filter layer includes a coarse sand layer, a medium sand layer, and a fine sand layer arranged in sequence, the coarse sand layer is arranged away from the roadbed; the thickness of the coarse sand layer is 8~30cm, the thickness of the medium sand layer is 10~20cm, the thickness of the fine sand layer is 10~20cm, the particle size of the gravel in the coarse sand layer is 5~20mm, the particle size of the gravel in the medium sand layer is 1~5mm, and the particle size of the gravel in the fine sand layer is 0.25~1mm.

9. The moisture-proof accumulation structure for roadbed on the mountain side or slope side in permafrost areas according to claim 7, characterized in that: The electric heating film is powered by a solar energy storage system.

10. A moisture-proof accumulation structure for roadbed on the mountain side or slope side in permafrost areas according to any one of claims 7 to 9, characterized in that: The height between the bottom of the heating drainage ditch and the upper limit of the permafrost is a limited height, and the method for determining the limited height is: The second daily water seepage is calculated based on the sum of the difference between the evaporation power and precipitation in the months with an average monthly temperature greater than 0°C and the parameters of the water-proof water accumulation structure. The second daily water seepage is the water seepage in the active layer of the permafrost area that does not enter the water-proof water accumulation structure. The calculation formula for the second daily water seepage is: in The second daily water inflow, l The distance between the heating drainage ditch and the toe of the roadbed slope; Based on the geological data of permafrost areas, the permeability coefficient of the second soil layer and the hydraulic gradient of the second soil layer are obtained so that water does not enter the active layer of the anti-water accumulation structure; The limited height is calculated using the second soil layer permeability coefficient, the second soil layer hydraulic gradient, and the second daily seepage volume. The calculation formula for the limited height is: in To limit the height, The permeability coefficient of the second soil layer, is the hydraulic gradient of the second soil layer.

Images