A dam anti-frost heaving protection structure and construction method

Abstract

The application belongs to the technical field of geotechnical engineering, and particularly relates to a dam anti-frost heaving protection structure and a construction method. The dam anti-frost heaving protection structure comprises a capillary barrier and an inclined drainage pipe. The capillary barrier comprises a top layer, a middle layer and a bottom layer. The top layer comprises a plurality of soil-PCM microcapsule geotextile bags and a soil layer. The middle layer is composed of a plurality of fine particle-wicking geotextile geotextile bags, which are located on the inner side of the soil-PCM microcapsule geotextile bags and are adjacent to each other. The bottom layer comprises a coarse particle layer and a coarse particle recycled concrete aggregate layer, which are adjacent to the middle layer and located on the inner side of the middle layer. The inclined drainage pipe is inserted into the slope soil. The dam anti-frost heaving protection structure adopts the capillary barrier system, wicking geotextile, PCM and inclined drainage pipe, can effectively reduce the freezing temperature of the reservoir slope soil in the cold region in winter, can effectively improve the stability of the reservoir slope in the cold region in winter, can increase the vegetation coverage, and can play the roles of heat preservation, environment beautification and soil and water conservation.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically a dam frost heave protection structure and construction method. Background Technology

[0002] People's needs for a better life have led to higher demands, including higher requirements for living conditions and the natural environment. The construction of reservoirs can not only improve the quality of drinking water for residents but also improve the ecological environment.

[0003] The impact of winter frost heave on reservoir slopes cannot be ignored. In cold winters, especially in areas where minimum temperatures drop below -10°C, reservoir slopes are frequently damaged. Frost heave can cause cracks in the slopes, allowing ice to rise from the water's edge to the slope, subjecting it to ice thrust and pressure, potentially leading to slope failure. More seriously, the combined effects of ice pressure, ice thrust, and freeze-thaw cycles can cause overall sliding and overturning deformation. Particularly during warming and freeze-thaw cycles, excessive and uneven settlement of the slope soil can occur, leading to the overturning and collapse of the dam and slope. If the soil moisture content is too high, it can even cause liquefaction and rheological changes in the foundation soil, resulting in large-scale damage to the dam and slope protection.

[0004] Therefore, managers and maintainers of reservoir slopes must fully consider the impact of winter icing and freeze-thaw cycles on reservoir slopes and take corresponding measures to prevent and mitigate these impacts in order to ensure the safety and stability of reservoir slopes. Summary of the Invention

[0005] The purpose of this invention is to provide a dam frost heave protection structure and construction method to improve the stability of reservoir slopes under freezing and freeze-thaw cycles. Utilizing the Gibbs-Thompson principle, the suction effect of capillary barriers is applied to slope frost prevention, and wicking geotextiles are added to the capillary barriers to enhance their suction. PCM materials are used to effectively control and delay temperature changes within the dam frost heave protection structure. Furthermore, the double-layered inclined drainage pipes ensure effective drainage of the slope during both the high-water and low-water periods of the reservoir.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes: A dam frost heave protection structure includes a capillary barrier and an inclined drainage pipe. The capillary barrier comprises a top layer, a middle layer, and a bottom layer. The top layer includes several soil-PCM microcapsule geotextile bags and a soil layer. The middle layer consists of several fine-particle-core geotextile bags, which are located inside and adjacent to each other on the soil-PCM microcapsule geotextile bags. The bottom layer includes a coarse-particle layer and a coarse-particle recycled concrete aggregate layer, which are adjacent to and inside the middle layer. The inclined drainage pipe is inserted into the slope soil.

[0007] In a preferred embodiment, the proportion of PCM microcapsules mixed in the soil is 5%~15%; the PCM microcapsules include a first type of PCM with a phase transition temperature of -3°C and a second type of PCM with a phase transition temperature of -8°C. If A2C2 + A1C1 is lower than the phase transition temperature of the second type of PCM of -8°C, then the volume ratio of the first type of PCM and the second type of PCM is: (-3°C - (-8°C)) : (-8°C - (A2C2 + A1C1)), where C1 is the average winter temperature of a certain place for several consecutive years, C2 is the lowest winter temperature of a certain place for several consecutive years, A1 is the weight of the average winter temperature of a certain place, A2 is the weight of the lowest winter temperature of a certain place, A1 + A2 = 1, A2 > A1, and A1 and A2 are respectively > 0.

[0008] Furthermore, when C1 < 0℃, the volume ratio of wicking geotextile to fine particles-wicking geotextile is: (1) p — The proportion of wicking geotextile in the mixed soil. C1 — The average winter temperature of a certain location over several consecutive years. θ — The average volumetric water content in the soil of the reservoir slope. A ———— Reservoir slope gradient Xt — Microcapsule volume ratio d————Proportional coefficient of wicking geotextile.

[0009] Among them, the coarse-grained layer in the bottom layer is adjacent to the soil layer and located below the soil layer; the coarse-grained layer in the bottom layer abuts against each other and the coarse-grained layer is located above the coarse-grained recycled concrete aggregate layer; the coarse-grained recycled concrete aggregate layer abuts against the slope and top surface of the reservoir slope soil and presents an approximately L-shaped form.

[0010] Several soil-PCM microcapsule geotextile bags are vertically staggered and basically parallel to the slope of the reservoir slope soil; the soil layer is adjacent to the upper layer of several soil-PCM microcapsule geotextile bags and is basically parallel to the top surface of the reservoir slope soil.

[0011] Preferably, the inclined drainage pipe is set at an angle of 7 to 13° to the water surface; the inclined drainage pipe is inserted into the slope soil at a distance of 1.2 to 1.8m.

[0012] The inclined drainage pipe is wrapped with geotextile; the inclined drainage pipe is installed in two layers. The first layer of inclined drainage pipe is installed 0.4~0.6m above the water surface during the dry season in winter, and the second layer of inclined drainage pipe is installed 0.4~0.6m above the water level during the wet season in summer.

[0013] Another object of the present invention is to disclose a construction method for the aforementioned dam frost heave protection structure, comprising the following steps: Site surveying; mixing PCM microcapsules with soil, mixing fine particles with wicking geotextiles, filling geotextile bags; particle compaction; laying geotextile bags, laying geogrids, laying geotextiles; geogrid laying; turf construction; jacking up slope drainage pipes.

[0014] The proportion of PCM microcapsules mixed in the soil is 5%~15%; the PCM microcapsules include a first type of PCM with a phase transition temperature of -3°C and a second type of PCM with a phase transition temperature of -8°C. If A2C2+ A1C1 is lower than the phase transition temperature of the second type of PCM of -8°C, then the volume ratio of the first type of PCM and the second type of PCM is: (-3°C-(-8°C)):(-8°C-(A2C2+ A1C1)), where C1 is the average winter temperature of a certain place for several consecutive years, C2 is the lowest winter temperature of a certain place for several consecutive years, A1 is the weight of the average winter temperature of a certain place, A2 is the weight of the lowest winter temperature of a certain place, A1+A2=1, A2>A1, and A1 and A2 are respectively>0.

[0015] When C1 < 0℃, the volume ratio of wicking geotextile to fine particles - wicking geotextile is: (1) p ———— The volume ratio of wicking geotextile to fine particles - wicking geotextile C1 — The average winter temperature of a certain location over several consecutive years. θ — The average volumetric water content in the soil of the reservoir slope. A ———— Reservoir slope gradient Xt — Microcapsule volume ratio d————Proportional coefficient of wicking geotextile.

[0016] The advantages of this invention are: by implementing this invention, the stability of reservoir slopes in cold regions during winter can be enhanced. This invention employs a capillary barrier system, wicking geotextiles, PCM (polycrystalline silicon membrane), and inclined drainage pipes, which can effectively reduce the freezing temperature of reservoir slope soil in cold regions during winter. This not only effectively improves the stability of reservoir slopes in cold regions during winter but also increases vegetation cover, playing a role in heat preservation, environmental beautification, and soil and water conservation. Simultaneously, the construction of this system can also realize the secondary utilization of construction solid waste, demonstrating a certain degree of environmental friendliness. The application of this invention is conducive to promoting environmental improvement and sustainable development. Attached Figure Description

[0017] Figure 1 A schematic cross-sectional view of a dam frost heave protection structure; Figure 2A schematic diagram of a dam's frost heave protection structure; Figure 3 Schematic diagram of the cross-section of the inclined drainage pipe; Meaning of the reference numerals in the diagram: 1-Soil-PCM microcapsule geotextile bag, 2-Ryegrass, 3-Summer high water level, 4-Winter low water level, 5-Geogrid, 6-Fine particle-core absorbent geotextile geotextile bag, 7-Soil layer, 8-Coarse particle layer, 9-Coarse particle recycled concrete aggregate layer, 10-Reservoir slope soil, 11-Inclined drainage pipe, 12-Reservoir, 13-Piercing drill bit, 14-Drainage hole, 15-Drainage outlet, 16-Geotextile. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] Unless otherwise specified, all materials used in this invention are conventional products that can be purchased commercially.

[0020] A dam frost heave protection structure consists of a capillary barrier, an inclined drainage pipe 11, and other structures.

[0021] The capillary barrier comprises a top layer, a middle layer, and a bottom layer. The top layer includes several soil-PCM microcapsule geotextile bags 1 and a soil layer 7. The soil-PCM microcapsule geotextile bags 1 are vertically staggered and are basically parallel to the slope of the reservoir slope soil 10. The soil layer 7 is adjacent to the upper layer of geotextile bags of the soil-PCM microcapsule geotextile bags 1 and is basically parallel to the top surface of the reservoir slope soil. The soil layer 7 is also adjacent to the upper layer of fine particle-core geotextile geotextile bags 6. The middle layer consists of several vertically staggered fine particle-core geotextile geotextile bags 6, which are located inside the soil-PCM microcapsule geotextile bags and are adjacent to each other. The bottom layer includes a coarse-grained layer 8 and a coarse-grained recycled concrete aggregate layer 9. The bottom layer is adjacent to the middle layer and located inside the middle layer. The coarse-grained layer 8 in the bottom layer is adjacent to the soil layer and located below the soil layer. The coarse-grained layer 8 and the coarse-grained recycled concrete aggregate layer 9 in the bottom layer abut against each other, and the coarse-grained layer 8 is located above the coarse-grained recycled concrete aggregate layer 9. The coarse-grained recycled concrete aggregate layer 9 abuts against the slope and top surface of the reservoir slope soil 10 and presents an approximately L-shaped form.

[0022] The soil in the PCM microcapsule geotextile bag 1 and the soil layer 7 consist of well-drained, arable, loose loam that is free from clods and contains no grass or weeds, other impurities, or stones with a diameter greater than 25 mm; it is free from calcium carbonate, subsoil, garbage, roots, mud, phytotoxic substances, and other harmful substances; it should be fertile, loose, non-toxic, and able to support the growth of healthy plants.

[0023] PCM is added to the top layer to improve the insulation effect, and geotextile is added to the middle layer to remove moisture from the soil. PCM is not added to soil layer 7 because the water-facing slope of the reservoir is the main area of ​​frost heave, and the moisture content at the top is low, so adding PCM is not considered.

[0024] Soil, including fine and coarse particles, is collectively referred to as soil. According to the Gibbs-Thomson effect, when pore water in soil begins to freeze, a curved interface forms between capillary water and ice. The surface tension at this interface causes the water pressure to be lower than the ice pressure. The lower capillary pressure relative to pure water pressure results in a lower chemical potential, and the freezing temperature of the soil corresponding to the intersection of this chemical potential and that of ice is lower. The freezing temperature of soil is also influenced by its water content. Water first fills small pores and then large pores. If the water content is low, water only fills the smaller pores, leaving the larger pores empty. The capillary action in the smaller pores is more significant, resulting in a lower freezing temperature. Therefore, the less water in the soil, the lower the freezing temperature. This invention increases the suction of unsaturated soil on slopes and increases seepage flow through the capillary barrier, reducing the water content of reservoir slopes and thus lowering the freezing temperature of the slope soil. Simultaneously, the vegetation on the capillary barrier system enhances slope stability while also providing insulation, beautifying the environment, and conserving water and soil.

[0025] For details on the frost heave protection structure of the dike, please refer to Figure 1 , Figure 2 Sloping drain pipe Figure 3 The dam frost heave protection structure and construction method of this invention have the advantages of effectively preventing frost heave damage to dam slopes, simple construction process, and enhanced environmental resilience. This structure exhibits excellent performance under winter reservoir slope freezing and freeze-thaw cycles, effectively resisting the damage to slopes caused by ice thrust and ice heave. A capillary barrier is installed on the slope surface. This structure itself enhances slope stability, and the capillary barrier utilizes the principles of unsaturated soil and the Gibbs-Thompson effect to enhance slope seepage and increase soil suction through capillary action. The inclined drainage pipes effectively drain water infiltrating into the slope from the reservoir, reducing slope moisture content and effectively lowering the soil freezing temperature in winter, making the reservoir slope soil less prone to freezing and damage. Green planting on top of the capillary barrier not only beautifies the environment but also reduces runoff erosion in summer, reduces soil erosion, and enhances environmental resilience.

[0026] Capillary barriers are installed on the surface of the reservoir slope. The top layer of soil-PCM microcapsule geotextile bag 1 consists of soil and microcapsules containing low-temperature phase change material PCM. The PCM microcapsules are mixed evenly with the soil. PCM is liquid at room temperature and solidifies at low temperatures. Mixing the PCM microcapsules with the soil effectively improves the material's durability, prevents leakage caused by microcracks, and extends the lifespan of the PCM, making it suitable for slope environments with severe freeze-thaw cycles. To effectively play a temperature control and delay role in dam frost heave prevention structures, PCM material undergoes a phase change at around -3°C to -8°C. This temperature range is typically suitable for frost protection requirements in engineering structures such as reservoirs. PCM material has a high latent heat (typically 100–200 J / g or even higher), providing sufficient buffering capacity by absorbing or releasing enough heat during the phase change process to smooth temperature fluctuations. The soil and PCM microcapsules are thoroughly mixed and placed in the geotextile bag. The system incorporates two types of PCM microcapsules for phased temperature control: the first PCM has a phase change temperature of -3°C to handle rapid initial freezing, and the second PCM has a phase change temperature of -8°C to handle extremely cold weather. This allows for phased delayed freezing, increasing the multi-level buffering effect of the freezing process. The middle layer of fine-particle-endoseptic geotextile geobags consists of fine particles and endoseptic geotextiles. Compared to ordinary capillary barrier systems, the addition of endoseptic geotextiles to the fine-particle layer enhances soil suction, draining rainwater and freeze-thaw water infiltrating the slope surface, thereby lowering the freezing temperature. The bottom layer consists of recycled concrete aggregate (RCA) and equivalent coarse particles, acting as a barrier. The particle size of the coarse and fine particles is mainly determined based on the climatic conditions of the region and the unsaturated hydraulic properties of different particle size soil combinations. The top layer of soil-PCM microcapsules and the middle layer of fine-particle-endoseptic geotextiles are both filled in geobags. A suitable geogrid 5 is used, which is securely fixed to each geobag. Compact the geotextile bags to ensure they are strong enough to provide the stability required during and after construction.

[0027] An inclined drainage pipe 11 is inserted into the slope to drain water that has seeped into the slope from the reservoir. Optionally, intelligent control can be used to control the drainage from the inclined drainage pipe. The controller is electrically connected to a temperature sensor, a soil moisture sensor, and an inclined drainage pipe regulating valve. A temperature sensor and a soil moisture sensor are installed in the slope soil next to each inclined drainage pipe, and an inclined drainage pipe regulating valve is installed on each pipe. The controller can be located inside or outside the slope. If the temperature sensor detects that the temperature in a certain area is below -3℃, or the soil moisture sensor detects that the soil moisture is above a preset threshold, the controller, upon receiving the temperature and humidity information, increases the drainage rate in that area (i.e., the corresponding inclined drainage pipe regulating valve increases the drainage volume; this increased drainage volume value can be preset), accelerating water removal. If the temperature sensor detects that the temperature in a certain area is not lower than -3℃, and the soil moisture sensor detects that the soil moisture is not above a preset threshold, the controller adjusts the corresponding inclined drainage pipe regulating valve (i.e., the regulating valve decreases to reduce the drainage volume and protect capillary suction; this decreased drainage volume value can be preset). This forms an intelligent drainage-intelligent temperature control collaborative system, which is more dynamic and precise.

[0028] Construction process of the dam's frost heave protection structure: During the construction of the dam's frost heave protection structure, it is essential to prevent rainwater from entering the site. If rainfall occurs during construction, temporary protective coverings must be prepared to reduce rainwater seepage into the slope.

[0029] Step 1: Site Measurement Before construction begins, the on-site density of the original slope soil should be measured, and the slope surface should be trimmed and leveled, including dimensions, depth, or slope, in order to facilitate the construction of the capillary barrier (GBS).

[0030] Specifically, before construction begins, the on-site density of the original slope soil should be measured at three locations. The original slope soil should be compacted to ensure that the effective internal friction angle of the compacted soil reaches at least 34 degrees and the minimum dry density is 1.8 mg / m³. The soil at the toe of the slope should be compacted to a minimum dry density of 18.5 kN / m³. 3 The depth should be at least 1 meter. Compaction should be carried out in units of 500mm depth, or in other appropriate units of depth. Figure 1 As shown, the slope surface is trimmed and leveled, including dimensions, depth, or slope, to facilitate the construction of capillary barriers (GBS). The bottom layer of the capillary barrier is placed at the water surface during the winter dry season.

[0031] Step 2: Mix PCM microcapsules with soil, mix fine particles with wicking geotextile, and fill with geotextile bags. Use qualified geotextile bags, such as Polyfelt TS nonwoven geotextile TS80 or materials with equivalent field performance, and fill them with soil, PCM microcapsules, fine-grained materials, or wicking geotextiles for slope construction. After filling, all geotextile bags should be closed and sewn (or other equivalent methods should be used) to prevent the material inside the geotextile bags from being washed away by rainwater.

[0032] The process involves using qualified geotextile bags (i.e., geotextile bags) to uniformly mix PCM microcapsules with soil in a specific ratio. The volume ratio of PCM microcapsules is controlled between 5% and 15% (referring to the proportion of PCM microcapsule volume to the total volume of PCM microcapsules and soil within the geotextile bag, preferably 10%) to ensure sufficient latent heat reserve during the phase change process. If the proportion of added PCM microcapsules is less than 5%, the release temperature will be limited, and the anti-freezing function of PCM cannot be effectively utilized when the temperature drops; if the proportion of added PCM microcapsules is greater than 15%, it will reduce the soil strength and is uneconomical. The geotextile bags are filled with fine-grained materials and wicking geotextiles for slope construction.

[0033] PCM includes a first type of PCM and a second type of PCM. In some embodiments, the first type of PCM and the second type of PCM can be set to a fixed ratio, such as a volume ratio of 1:1.

[0034] In other embodiments, the ratio of the two PCMs can be set as follows: if A2C2 + A1C1 is lower than the phase transition temperature of the second PCM by -8°C, then the volume ratio of the first PCM to the second PCM is: (-3°C - (-8°C)) : (-8°C - (A2C2 + A1C1)), where C1 is the average winter temperature of a certain location over several consecutive years, C2 is the lowest winter temperature of a certain location over several consecutive years, A1 is the weight of the average winter temperature of a certain location, A2 is the weight of the lowest winter temperature of a certain location, A1 + A2 = 1, and A1 and A2 are both > 0. When setting the ratio of the two PCMs, both the lowest winter temperature and the average winter temperature are considered, with the lowest winter temperature being more important. Setting A2>A1, since the number of days with the lowest winter temperatures is limited and this invention also employs other anti-frost heave measures such as capillary barriers, wicking geotextiles, and inclined drainage outlets, it is unnecessary to use the method of determining the ratio of the two PCMs solely based on the lowest temperature (when determining the ratio solely based on the lowest temperature, the relative amount of the second PCM added is higher, and the relative amount of the first PCM added is lower, but in most cases the temperature is not low enough so that the second PCM cannot play its role). The method of this invention can better exert the phased delayed freezing effect and increase the multi-level buffering effect of the freezing process; if the winter temperature of A2C2+ A1C1 in a certain area is higher than the phase transition temperature of the first PCM by -3℃, then there is no need to add PCM microcapsules; if the winter temperature of A2C2+ A1C1 in a certain area is lower than -3℃ but higher than -8℃, then only the first PCM is added.

[0035] This invention is mainly applicable to extremely cold weather, specifically when the phase transition temperature of A2C2+ A1C1 is below -8°C for the second type of PCM.

[0036] For example, the average winter temperature in a certain area is -7℃ for three consecutive years, the lowest winter temperature is -17℃ for three consecutive years, A1 is 0.3, A2 is 0.7, and the volume ratio of the first type of PCM to the second type of PCM is 5:6.

[0037] The proportion of wicking geotextile mixed in the fine particles (i.e., the volume ratio of wicking geotextile to fine particles - wicking geotextile) can be 0-20% (preferably 0-15%) to achieve water absorption and prevent swelling, while also preventing excessive wicking geotextile from significantly affecting the properties of the fine-particle soil. When C1 < 0℃, in some embodiments, the proportion of wicking geotextile mixed in the fine particles can be directly preset to 1-15%.

[0038] Furthermore, when C1 ≥ 0℃, no wicking geotextile is added to the fine particles.

[0039] Furthermore, in other embodiments, when C1 < 0°C, the proportion of wicking geotextile mixed in the fine particles (i.e., the volume ratio of wicking geotextile to fine particles - wicking geotextile) can also be determined by formula (1): (1) p ———— The volume ratio of wicking geotextile to fine particles - wicking geotextile C1 — The average winter temperature of a certain location over several consecutive years; C1 < 0℃. θ — The average volumetric water content in the soil of a reservoir slope; typically, θ is between 0.1 and 0.4. A ———— Reservoir slope, typically A is 20-45°. Xt — Microcapsule volume ratio d————The proportion coefficient of wicking geotextile reflects the relationship between the proportion of the wicking geotextile and the overall coefficient consisting of the directly proportional average winter temperature, volumetric moisture content, and slope, and the inversely proportional proportion of the microcapsule volume.

[0040] Due to the varying wicking capacities of different geotextiles, the value of d may differ for different geotextiles.

[0041] When the amount calculated by formula (1) is higher than the threshold of 20%, the proportion of wicking geotextile mixed in the fine particles is determined to be 20%; otherwise, the proportion of wicking geotextile mixed in the fine particles is determined to be the calculated amount. The 20% threshold is set with reference to the existing technology for the addition amount of wicking geotextile.

[0042] For example, the average winter temperature in a certain area for three consecutive years is -7℃ (C1 is -7 in formula (1)), the slope is 25° (θ is 25 in formula (1)), the average volumetric water content is 0.4%, and the total proportion of PCM microcapsules added is 10% (in formula (1)). X t Take 10), d=0.5, and by formula (1), we can get: =3.5 (unit is %).

[0043] Step 3: Particle compaction The fine-grained material is compacted, and the coarse-grained material (coarse-grained layer 8 and coarse-grained recycled concrete aggregate layer 9, collectively referred to as the coarse-grained layer) is compacted.

[0044] The fine-grained material (which can be fine sand) should be compacted to a relative density (Dr) between 70% and 90%, or to a minimum dry density (ρd) of 1.55 Mg / m³. The coarse-grained layer should be compacted to a relative density (Dr) between 70% and 90%, or to a minimum dry density (ρd) of 1.8 Mg / m³. The coarse-grained recycled concrete aggregate layer should also be compacted to a relative density (Dr) between 70% and 90%, or to a minimum dry density (ρd) of 1.8 Mg / m³.

[0045] Step 4: Laying geotextile bags, geogrids, and geotextile fabrics. The process involves laying a coarse-grained recycled concrete aggregate layer, a coarse-grained layer, a soil layer, fine-grained wicking geotextile geotextile bags, and soil-PCM microcapsule geotextile bags. The geogrid must be securely attached to each geotextile bag. Appropriate geogrids should be used to ensure sufficient strength to provide the required stability during and after GBS construction.

[0046] The geotextile is placed between the coarse-grained layer and the fine-grained layer (i.e., fine-grained-core geotextile geobags), and between the soil-PCM microcapsule geobag layer and the grass planting medium, at the top of the slope.

[0047] Step 5: Turf Installation Turfing should be planted at the top of the slope (specifically, a planting medium layer is placed on top of the soil-PCM microcapsule geotextile bag layer and the soil layer, and turf is planted in this planting medium layer), using ryegrass 2. The planting medium layer should be at least 100 mm deep. The planting medium consists of three parts topsoil and one part soil conditioner (e.g., straw biochar), by weight, and 1 kg of granular fertilizer (with an N:P:K mass ratio of 15:15:6.4) should be added per cubic meter. The topsoil used should be free of garbage, roots, tree stumps or other debris, and should be loose and well-aerated.

[0048] Step 6: Insert the inclined drainage pipe into the slope and install the temperature and humidity sensor and the regulating valve of the inclined drainage pipe.

[0049] The inclined drainage pipe has a diameter of 10cm, which facilitates the jacking of the slope soil and meets drainage requirements. It is wrapped with geotextile 16 to prevent fine soil particles from entering the inclined drainage pipe and causing blockage when jacking into the capillary barrier system and slope. During construction, the inclined drainage pipe should be set at a 10° angle to the water surface to facilitate water flow. The inclined drainage pipe should pass through the soil-PCM microcapsule geotextile bag layer, the fine particle-core absorbent geotextile bag layer, and the coarse-grained layer (referring to the coarse-grained recycled concrete aggregate layer) and be jacked into the slope soil by the jacking drill bit 13 for a distance of 1.5m (1.5m refers to the extension length of the inclined drainage pipe in the slope soil); the inclined drainage pipe passes through the soil-PCM microcapsule geotextile bag layer, the fine particle-core absorbent geotextile bag layer, and the coarse-grained layer in the same way: by jacking into the slope soil by the jacking drill bit 13. The inclined drainage pipes are installed in two layers. The first layer is set 0.5m above the water level of 4 during the dry season in winter (the highest point of the first layer of drainage pipes is 0.5m above the water level during the dry season in winter). The second layer is set 0.5m above the water level of 3 during the wet season in summer (the highest point of the second layer of drainage pipes is 0.5m above the water level during the wet season in summer). During the wet season, the upper drainage pipe can be used while the lower drainage pipe is submerged in water. In this way, the system can reduce the water content of the slope in both winter and summer.

[0050] Drainage holes 14 are evenly distributed on the surface of the inclined drainage pipe 11. One end of the inclined drainage pipe 11 is located in the soil of the slope, and the other end is located next to the turf, with a drainage outlet 15 provided at the other end.

[0051] The slope embankment anti-frost heave structure was constructed using steps 1-7 above, with a PCM microcapsule volume ratio of 3.5% and a PCM microcapsule volume ratio controlled at 10%. The volume ratio of the first type of PCM to the second type of PCM was 5:6. After one winter, the average temperature in the area was -7℃ and the lowest temperature was -18℃. The slope remained stable, and no cracks or collapses were observed.

[0052] In the description of this invention, references to terms such as “embodiment,” “specific example,” or “practical application” indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment or example of the invention; the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A dam frost heave protection structure, characterized in that: The system includes a capillary barrier and an inclined drainage pipe. The capillary barrier consists of a top layer, a middle layer, and a bottom layer. The top layer comprises several soil-PCM microcapsule geotextile bags and a soil layer. The soil-PCM microcapsule geotextile bags are vertically staggered and basically parallel to the slope of the reservoir slope. The soil layer is adjacent to the upper layer of geotextile bags and is basically parallel to the top surface of the reservoir slope soil. The soil layer is also in contact with the upper layer of fine-particle-core geotextile bags. The middle layer consists of several vertically staggered fine-particle-core geotextile bags. The granular-core absorbent geotextile geotextile bags are located inside the soil-PCM microcapsule geotextile bags and are adjacent to each other; the bottom layer includes a coarse-grained layer and a coarse-grained recycled concrete aggregate layer. The bottom layer is adjacent to the middle layer and is located inside the middle layer. The coarse-grained layer in the bottom layer is adjacent to the soil layer and is located below the soil layer; the coarse-grained layer and the coarse-grained recycled concrete aggregate layer in the bottom layer abut against each other and the coarse-grained layer is located above the coarse-grained recycled concrete aggregate layer. The coarse-grained recycled concrete aggregate layer abuts against the slope and top surface of the reservoir slope soil and presents an approximately L-shaped form; the inclined drainage pipe is pushed into the slope soil.

2. The frost heave protection structure for dikes according to claim 1, characterized in that: The volume of PCM microcapsules accounts for 5% to 15% of the total volume of PCM microcapsules and soil in the geotextile bag. The PCM microcapsules include a first type of PCM with a phase transition temperature of -3°C and a second type of PCM with a phase transition temperature of -8°C. If A2C2 + A1C1 is lower than the phase transition temperature of the second type of PCM of -8°C, then the volume ratio of the first type of PCM and the second type of PCM is: (-3°C - (-8°C)) : (-8°C - (A2C2 + A1C1)), where C1 is the average winter temperature of a certain place for several consecutive years, C2 is the lowest winter temperature of a certain place for several consecutive years, A1 is the weight of the average winter temperature of a certain place, A2 is the weight of the lowest winter temperature of a certain place, A1 + A2 = 1, A2 > A1, and A1 and A2 are respectively > 0.

3. The frost heave protection structure for dikes according to claim 1, characterized in that: When C1 < 0℃, the volume ratio of wicking geotextile to fine particles - wicking geotextile is: ； C1 ———— The average winter temperature of a certain location over several consecutive years. θ — The average volumetric water content in the soil of the reservoir slope. A ———— Reservoir slope gradient —Microcapsule volume ratio, d————Proportional coefficient of wicking geotextile.

4. The frost heave protection structure for dikes according to claim 1, characterized in that: The inclined drainage pipe is set at an angle of 7 to 13 degrees to the water surface; the inclined drainage pipe is inserted into the slope soil at a distance of 1.2 to 1.8 meters.

5. A dam frost heave protection structure according to claim 1, characterized in that: The inclined drainage pipe is wrapped with geotextile; the inclined drainage pipe is installed in two layers. The first layer of inclined drainage pipe is installed 0.4~0.6m above the water surface during the dry season in winter, and the second layer of inclined drainage pipe is installed 0.4~0.6m above the water level during the wet season in summer.

6. A construction method for a dam frost heave protection structure according to any one of claims 1 to 5, characterized in that, Includes the following steps: Site surveying; mixing PCM microcapsules with soil, mixing fine particles with wicking geotextiles, filling geotextile bags; particle compaction; laying geotextile bags, laying geogrids, laying geotextiles; geogrid laying; turf construction; jacking up slope drainage pipes.

7. The construction method according to claim 6, characterized in that: The volume of PCM microcapsules accounts for 5% to 15% of the total volume of PCM microcapsules and soil in the geotextile bag. The PCM microcapsules include a first type of PCM with a phase transition temperature of -3°C and a second type of PCM with a phase transition temperature of -8°C. If A2C2 + A1C1 is lower than the phase transition temperature of the second type of PCM of -8°C, then the volume ratio of the first type of PCM and the second type of PCM is: (-3°C - (-8°C)) : (-8°C - (A2C2 + A1C1)), where C1 is the average winter temperature of a certain place for several consecutive years, C2 is the lowest winter temperature of a certain place for several consecutive years, A1 is the weight of the average winter temperature of a certain place, A2 is the weight of the lowest winter temperature of a certain place, A1 + A2 = 1, A2 > A1, and A1 and A2 are respectively > 0.

8. The construction method according to claim 6, characterized in that: When C1 < 0℃, the volume ratio of wicking geotextile to fine particles - wicking geotextile is: ； C1 ———— The average winter temperature of a certain location over several consecutive years. θ — The average volumetric water content in the soil of the reservoir slope. A ———— Reservoir slope gradient —Microcapsule volume ratio, d————Proportional coefficient of wicking geotextile.

Images