Drainage plate for unsaturated soil roadbed in cold region and mounting method of drainage plate

Abstract

The invention discloses a drainage plate for an unsaturated soil roadbed in a cold region. The drainage plate comprises a hydrophobic layer, a drainage layer and an anti-freezing layer which are sequentially arranged in parallel, the hydrophobic layer is made of a hydrophobic material; the drainage layer comprises at least two layers of capillary structures and water-absorbing fibers filled between the capillary structures, the outer layer is a vertical honeycomb tube, the inner layer is a horizontal honeycomb tube, and the radius is gradually reduced from outside to inside; the capillary tube structure adsorbs pore water in unsaturated soil through capillary action, and the water-absorbing fibers drive water to be discharged out of the roadbed through water content difference; and the anti-freezing layer is made of a low-temperature-resistant polymeric material. According to the drainage plate, through the capillary action of the middle three-dimensional drainage layer, pore water dispersed in unsaturated soil is actively adsorbed, water is directionally discharged in combination with gravity, and the problem that a traditional drainage pipe is low in efficiency in the unsaturated soil is solved; meanwhile, through double-layer protection of the hydrophobic layer and the anti-freezing layer, a moisture seepage path is blocked, soil particles are prevented from invading, and a drainage channel is prevented from being blocked.

Description

Technical Field

[0001] The present invention belongs to the technical field of roadbed slope drainage engineering, and relates to a drainage board structure for unsaturated soil roadbed in cold regions, which can realize capillary water blocking, gradient diversion and anti-frost heave functions, and specifically is a drainage board for unsaturated soil roadbed in cold regions and an installation method thereof. Background Art

[0002] The roadbed is an important part of my country's railway and highway projects. The long-term service stability of the roadbed is of great significance to my country's transportation industry. The gradation and moisture content of the roadbed filler are strictly controlled during the design and construction stage. However, in the long-term operation process, the moisture content in the roadbed filler changes significantly due to the coupling of environmental factors such as climate and rainfall and vehicle loads.

[0003] In cold regions, the roadbed faces the dual challenges of freeze-thaw cycles and capillary water migration. The shortcomings of existing technologies are as follows:

[0004] 1. Special problems in cold regions: Due to the low temperature in winter, the water in the roadbed in cold regions freezes into ice and migrates to the frozen surface, resulting in water enrichment at the frozen surface of the roadbed. In spring, the ice crystals in the soil melt, reducing the strength of the roadbed, causing the roadbed to soften and deform, and reducing the bearing capacity of the roadbed. Therefore, the water enrichment in the roadbed will greatly affect the long-term service reliability of the roadbed.

[0005] 2. Freeze-thaw cycle problem: The temperature gradient and ice-water phase change caused by freeze-thaw cycles in cold-region roadbeds further cause the moisture in the roadbed to migrate from the bottom to the top and accumulate at the top, resulting in frost heave deformation and mud oozing.

[0006] 3. Problems with traditional geotextiles: In order to block the seepage of water, a common treatment method is to lay waterproof and water-isolating geotextiles on the bottom of the roadbed to prevent the seepage of water in the filler.

[0007] Geotextiles can effectively isolate moisture migration in the early stage, but in long-term practice, due to the fact that the roadbed in the frozen soil area undergoes multiple freeze-thaw cycles, traditional geotextiles are prone to structural rupture or damage, and the water-blocking effect is reduced, which eventually leads to an increase in the moisture content inside the roadbed and cannot meet the roadbed drainage needs.

[0008] 4. Gravity drainage pipe problem: In cold regions with less precipitation, the roadbed fill is basically in an unsaturated state. At this time, the water diffuses through capillary action and is difficult to gather in traditional drainage pipes, making it difficult to effectively control the water in the unsaturated roadbed.

[0009] The above defects indicate that the drainage efficiency of waterproof geotextiles or gravity drain pipes is more obvious in roadbed soils with a moisture content close to saturation, but the drainage effect is poor in cold areas with less rainfall. Summary of the invention

[0010] The main purpose of the present invention is to provide a drainage board for unsaturated soil roadbed in cold areas and an installation method thereof, which can effectively drain water from the unsaturated soil roadbed.

[0011] The drainage board for unsaturated soil roadbed in cold regions provided by the present invention comprises a hydrophobic layer, a drainage layer and an antifreeze layer which are arranged in parallel in sequence; the hydrophobic layer is made of a hydrophobic material, such as a polypropylene non-woven fabric covered with a polytetrafluoroethylene coating; the drainage layer comprises at least two layers of capillary structures and water-absorbing fibers filled in the middle of the capillary structures, the outer layer is a vertical honeycomb tube, the inner layer is a horizontal honeycomb tube, and the radius decreases from the outside to the inside; the capillary structure absorbs pore water in the unsaturated soil by capillary action, and the water-absorbing fibers drive the water out of the roadbed by the water content difference; the antifreeze layer is made of a low-temperature resistant polymer material, such as a corrugated high-density polyethylene board. Active adaptive drainage of unsaturated soil is achieved through the multiple synergistic mechanisms of microporous interception of the hydrophobic layer, rapid diversion of the outer layer large-aperture honeycomb tube, continuous adsorption of the inner layer small-aperture honeycomb tube and active drainage of the water-absorbing fibers.

[0012] In one embodiment of the above-mentioned drainage board, the surface of the hydrophobic layer is coated with a hydrophobic coating, which can be a polytetrafluoroethylene coating.

[0013] In one embodiment of the above-mentioned drainage board, the drainage layer is a three-layer structure, with multiple layers of honeycomb capillary grids symmetrically arranged above and below, and the middle is filled with specially woven fibers.

[0014] In one embodiment of the above-mentioned drainage board, the multi-layer honeycomb capillary grid is divided into two layers, the outermost layer is vertically arranged honeycomb capillaries, and the pore diameter is larger than the pore diameter of the inner honeycomb tubes; the inner layer is horizontally arranged honeycomb capillaries, and the pore diameter of the inner capillaries is 1 / 3-1 / 2 of the pore diameter of the outer capillaries, so as to ensure that the inner honeycomb tubes absorb the moisture in the outer honeycomb tubes.

[0015] In one embodiment of the above-mentioned drainage board, each layer of honeycomb tubes is separated by a partition, and dense wave-dot circular holes are arranged on the partition.

[0016] In one embodiment of the above drainage board, the fibers are filled in the central cavity of the drainage layer in the same direction as the inner horizontal honeycomb tubes; the fibers are arranged in layers without spacing.

[0017] In one embodiment of the above-mentioned drainage board, the antifreeze layer is made of low-temperature resistant modified high-density polyethylene material, and the surface is corrugated.

[0018] A full-cover installation method using the above-mentioned drainage board comprises the following steps:

[0019] 1. According to the filler type, gradation and groundwater height of the roadbed, select the appropriate installation position and capillary diameter of the new drainage board;

[0020] 2. Evenly scrape the contact surface of the roadbed; at the same time, measure the transverse slope of the roadbed to ensure that there is a downward longitudinal slope from the center to the shoulder;

[0021] 3. With the central axis of the roadbed as the axis of symmetry, lay two layers of drainage boards from the center to the shoulder; the hydrophobic layer of the top drainage board faces upwards, the antifreeze layer faces downwards, and is in direct contact with the top surface of the roadbed; the antifreeze layer of the bottom drainage board faces upwards, and the hydrophobic layer faces downwards; the drainage boards on the same layer are overlapped; the two layers of drainage boards are set at a fixed interval, and the layers are staggered;

[0022] 4. The drainage board extends out of the shoulder of the road, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; installing a drainage pipe under the fiber to divert the water;

[0023] 5. Backfill the roadbed in layers and compact it to avoid bending the drainage board, which will reduce the drainage cross-section and reduce the drainage efficiency.

[0024] An insertion installation method using the above-mentioned drainage board comprises the following steps:

[0025] 1. According to the filler type, gradation and internal moisture distribution of the roadbed, the width, insertion depth and spacing of the drain board are determined by calculating the effective diameter. The moisture-enriched area of ​​the roadbed is determined by testing, and the drain board of a specific width is inserted into the area with higher moisture content inside the roadbed. The width of the drain board can be calculated by the following formula:

[0026]

[0027] Where: d is the equivalent diameter of the drain board, which is designed according to the distribution of the water-rich area inside the roadbed to ensure that the effective drainage area of ​​the drain board completely covers the water-rich area inside the roadbed; b is the width of the drain board; δ is the thickness of the drain board, which is a fixed value;

[0028] 2. Install an iron tip with a width and thickness slightly larger than the drain board at the insertion end of the drain board;

[0029] 3. Use a hydraulic penetration device to insert the drainage board into the roadbed along the shoulder slope. The insertion depth is determined according to the location of the aquifer, and the horizontal downward slope is maintained;

[0030] 4. The drainage board extends out of the shoulder of the road, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; installing a drainage pipe under the fiber to divert the water;

[0031] 5. When the drainage efficiency decreases, simply pull out the old plate and insert a new one without disturbing the roadbed structure.

[0032] The beneficial effects of the present invention are:

[0033] 1. Through the capillary action of the middle three-dimensional drainage layer, the dispersed pore water in the unsaturated soil is actively adsorbed, and the water is discharged directionally in combination with gravity, which solves the problem of low efficiency of traditional drainage pipes in unsaturated soil; at the same time, the double-layer protection of the hydrophobic layer and the antifreeze layer blocks the water seepage path and prevents the invasion of soil particles, avoiding the blockage of the drainage channel;

[0034] 2. The antifreeze layer uses low-temperature-resistant modified high-density polyethylene corrugated material to resist lateral stretching and frost heave stress and protect the integrity of the middle layer structure. At the same time, it drives drainage through capillary action and water content difference. Even if the water migration path is blocked during the freeze-thaw cycle, it can still continuously discharge the enriched water.

[0035] 3. The outer vertical honeycomb tube absorbs moisture, and the middle horizontal honeycomb tube collects moisture to the special woven fiber through capillary force to achieve multi-level drainage. During roadbed construction, drainage boards can be fully laid or installed on the shoulders during operation to meet different engineering needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the front cross-sectional structure of an embodiment of the present invention.

[0037] Figure 2 for Figure 1 Schematic diagram of the left-side cross-sectional structure.

[0038] Figure 3 for Figure 1 Attached is a schematic diagram of the cross-sectional structure.

[0039] Figure 4 This is a schematic diagram of the structure when the drainage board is fully laid on the roadbed.

[0040] Figure 5 This is a schematic diagram of the structure when the drainage board is inserted and laid on the roadbed. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technical solutions. Obviously, the described embodiments are only part of the embodiments, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Combination Figure 1 , Figure 2 and Figure 3It can be seen that the drainage board for unsaturated soil roadbed in cold regions disclosed in this embodiment includes a hydrophobic layer 1, a drainage layer 2 and an antifreeze layer 3 which are arranged in parallel from top to bottom.

[0043] The hydrophobic layer 1 is made of polypropylene or polyester material, and a hydrophobic coating is sprayed on the surface, and a polytetrafluoroethylene coating can be selected.

[0044] The low surface energy of the sprayed hydrophobic coating makes it difficult for water molecules to adhere, forming a physical barrier. The hydrophobic coating blocks the migration of liquid water into the roadbed, preventing rain or snowmelt from infiltrating the roadbed. At the same time, it isolates soil particles from entering the drainage layer 2, avoiding capillary blockage and maintaining smooth drainage channels.

[0045] The drainage layer 2 is a three-layer structure, with a honeycomb grid 21 symmetrically arranged above and below, and the middle is filled with special woven fibers 22.

[0046] The honeycomb grid 21 is divided into two layers, the outermost layer is a vertically arranged honeycomb polyester tube with a larger pore size; the inner layer is a horizontally arranged honeycomb tube with a smaller pore size layer by layer. Each layer of honeycomb tubes is separated by a partition, and a drainage circular hole group is set on the partition to allow moisture to migrate from the outer layer to the middle.

[0047] The two-layer honeycomb grid can use the outer vertical honeycomb tubes to absorb pore water in the unsaturated soil, and the inner horizontal honeycomb tubes can transfer water from the large-diameter tubes to the small-diameter tubes through capillary action.

[0048] The honeycomb grid mainly absorbs moisture from the soil to the drainage board through the capillary force exerted on the moisture in the soil. The capillary force is calculated as follows:

[0049]

[0050] Where: r is the surface tension of the liquid, here it is the surface tension of water; θ is the contact angle; r m is the pore radius; ρ is the density of water; g is the acceleration due to gravity; h is the rising height of capillary water.

[0051] From the above formula, it can be seen that capillaries with smaller radius can have stronger adsorption capacity. However, as the amount of liquid inside the capillary increases, the water absorption capacity of the capillary will be inhibited; therefore, the capillary radius should be determined according to the type, gradation and pore size distribution of the roadbed filler, and the capillary with the appropriate radius should be selected.

[0052] Adjacent capillaries are not connected, which reduces the probability of mutual influence and blockage between capillaries.

[0053] The fibers 22 are filled in the central cavity of the drainage layer 2 in the same direction as the inner horizontal honeycomb tubes. The fiber diameter is adjusted according to the grade of the roadbed filler and arranged in layers without intervals.

[0054] The fiber has good water absorption and can collect moisture in the outer honeycomb grid into the fiber, and continuously discharge moisture from the roadbed through the difference in moisture content between the fibers inside and outside the roadbed (high inside the roadbed and low outside).

[0055] The antifreeze layer 3 is made of low-temperature-resistant modified high-density polyethylene material, and its surface is corrugated.

[0056] The corrugated structure of the antifreeze layer can absorb lateral tensile stress and resist the brittle cracking of materials caused by freeze-thaw cycles. The mechanical strength of high-density polyethylene prevents the roadbed filler from piercing the drainage board. At the same time, the antifreeze layer and the hydrophobic layer work together to block the migration path of groundwater into the roadbed; it can also protect the drainage layer from being blocked by soil particles.

[0057] When using this drainage board, you can choose to fully pave it or install it with appropriate spacing according to the annual rainfall and evaporation in the area, as well as the length of time the temperature is below 0℃ in winter. At the same time, you can adjust the length of the drainage board that penetrates into the roadbed.

[0058] like Figure 4 As shown, when performing full-pavement installation, it is suitable for new roadbeds. The steps are as follows:

[0059] 1. According to the filler type, gradation and groundwater height of the roadbed, select the appropriate installation position and capillary diameter of the new drainage board;

[0060] 2. Evenly scrape the contact surface of the roadbed to increase the roughness and ensure that the drainage board can fit closely with the soil; at the same time, measure the transverse slope of the roadbed to ensure that there is a longitudinal slope of 5% to 10% from the center to the shoulder;

[0061] 3. With the central axis of the roadbed as the axis of symmetry, lay two layers of drainage boards from the center to the shoulder; the hydrophobic layer of the upper drainage board faces upwards, and the antifreeze layer faces downwards, directly contacting the roadbed filler, blocking the seepage path of water on the roadbed surface migrating downwards; the antifreeze layer of the lower drainage board faces upwards, and the hydrophobic layer faces downwards, blocking the seepage roadbed of water at the bottom of the roadbed migrating to the upper part of the roadbed; the drainage boards on the same layer are overlapped, and the overlap width is 15 to 30 cm to prevent discontinuity in laying of the drainage boards; according to the test results of the water content distribution of the roadbed, the interval between the two layers of drainage boards is 0.5 to 1.5 m, and the layers are staggered;

[0062] 4. The drainage board extends out of the shoulder by ≥20cm, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; install PVC drainage pipes under the fiber to quickly drain the water inside the roadbed;

[0063] 5. Backfill the roadbed in layers and compact it to avoid bending the drainage board, which will reduce the drainage cross-section and reduce the drainage efficiency.

[0064] like Figure 5 As shown, when inserting the installation, it is suitable for reconstruction on the existing roadbed. The steps are as follows:

[0065] 1. According to the filler type, gradation and internal moisture distribution of the roadbed, the width, insertion depth and spacing of the drain board are determined by effective diameter calculation. The effective diameter of the drain board is d and the length is L. The effective range of the drain board forms a cylinder with a diameter of d and a length of L. The water-enriched area of ​​the roadbed is determined by roadbed inspection and monitoring technologies such as ground penetrating radar, and the drain board of a specific width is inserted into the area with high moisture content inside the roadbed. The equivalent diameter of the drain board can be calculated by the following formula:

[0066]

[0067] Where: d is the equivalent diameter of the drain board, which is designed according to the distribution of the water-rich area inside the roadbed to ensure that the effective drainage area of ​​the drain board completely covers the water-rich area inside the roadbed; b is the width of the drain board; δ is the thickness of the drain board, which is a fixed value;

[0068] 2. Install an iron tip with a width and thickness slightly larger than the drainage board at the insertion end of the drainage board to reduce the penetration resistance;

[0069] 3. Use a hydraulic penetration device to insert the drainage board into the roadbed along the shoulder slope. The insertion depth is determined according to the location of the aquifer, and the slope is maintained at 5% to 10% downward from the horizontal;

[0070] 4. The drainage board extends out of the shoulder by ≥20cm, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; install PVC drainage pipes under the fiber to quickly drain the water inside the roadbed;

[0071] 5. When the drainage efficiency decreases, simply pull out the old plate and insert a new one without disturbing the roadbed structure.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A drainage board for unsaturated soil roadbed in cold regions, characterized by: It includes a hydrophobic layer, a drainage layer and an antifreeze layer which are arranged in parallel in sequence; the hydrophobic layer is made of a hydrophobic material; the drainage layer includes two layers of honeycomb capillary structures which are centrally symmetrically distributed and special woven fibers filled in the cavities surrounded by the symmetrically distributed capillary structures; The capillary structure absorbs pore water in unsaturated soil through capillary action, and the special woven fiber drives water to be discharged from the roadbed through capillary action and water content difference; the antifreeze layer is made of low-temperature resistant polymer material.

2. The drainage board for unsaturated soil roadbed in cold regions according to claim 1, characterized in that: The surface of the hydrophobic layer is coated with a hydrophobic coating.

3. The drainage board for unsaturated soil roadbed in cold regions according to claim 1, characterized in that: The drainage layer is a three-layer structure, with multiple layers of honeycomb capillary structures symmetrically arranged above and below, and special woven fibers filled in the middle.

4. The drainage board for unsaturated soil roadbed in cold regions according to claim 3, characterized in that: The multi-layer honeycomb capillary structure is divided into two layers. The outermost layer is vertically arranged honeycomb polyester capillaries with a pore size larger than that of the inner capillaries; the inner layer is horizontally arranged honeycomb polyester capillaries with a pore size that decreases layer by layer.

5. The drainage board for unsaturated soil roadbed in cold regions according to claim 4, characterized in that: Each layer of honeycomb tubes is separated by a partition plate, and dense wavy circular holes are arranged on the partition plate.

6. The drainage board for unsaturated soil roadbed in cold regions according to claim 4, characterized in that: The fibers are filled in the central cavity of the drainage layer in the same direction as the inner horizontal honeycomb tube; the fibers are arranged in layers without intervals.

7. The drainage board for unsaturated soil roadbed in cold regions according to claim 1, characterized in that: The antifreeze layer is made of low-temperature-resistant modified high-density polyethylene material and has a corrugated structure.

8. A method for installing the drainage board for unsaturated soil roadbed in cold regions using the drainage board according to claims 1 to 7, comprising the following steps:

1. Select the installation position of the drainage board and the capillary diameter according to the filler type, gradation and groundwater height of the roadbed; 2. Evenly scrape the contact surface of the roadbed; at the same time, measure the transverse slope of the roadbed to ensure that there is a downward longitudinal slope from the center to the shoulder; 3. With the central axis of the roadbed as the axis of symmetry, lay two layers of drainage boards from the center to the shoulder; the hydrophobic layer of the upper drainage board faces upward and the antifreeze layer faces downward; the antifreeze layer of the lower drainage board faces upward and the hydrophobic layer faces downward; the hydrophobic layer and the antifreeze layer are in direct contact with the roadbed filler; the drainage boards on the same layer are overlapped; the two layers of drainage boards are set at a fixed interval, and the layers are staggered; 4. The drainage board extends out of the shoulder of the road, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; installing a drainage pipe under the fiber to divert the water; 5. Backfill the roadbed in layers and compact it to avoid bending the drainage board, which will reduce the drainage cross-section and reduce the drainage efficiency.

9. An insertion installation method for the drainage board for unsaturated soil roadbed in cold regions using the drainage board according to claims 1 to 7, comprising the following steps:

1. According to the filler type, gradation and internal moisture distribution of the roadbed, the width, insertion depth and spacing of the drain board are determined by effective diameter calculation. The moisture-enriched area of ​​the roadbed is determined by testing, and the drain board of a specific width is inserted into the area with higher moisture content inside the roadbed. The effective diameter of the drain board can be calculated by the following formula: Where: d is the equivalent diameter of the drain board; b is the width of the drain board; δ is the thickness of the drain board, which is a fixed value; 2. Install an iron tip with a width and thickness slightly larger than the drain board at the insertion end of the drain board; 3. Use a hydraulic penetration device to insert the drainage board into the roadbed along the shoulder slope. The insertion depth is determined according to the location of the aquifer, and the horizontal downward slope is maintained; 4. The drainage board extends out of the shoulder of the road, peeling off the hydrophobic layer and antifreeze layer, exposing the special woven fiber and destroying its woven structure; installing a drainage pipe under the fiber to divert the water; 5. When the drainage efficiency decreases, simply pull out the old plate and insert a new one without disturbing the roadbed structure.

Images