A saline soil roadbed structure and construction method considering freeze-thaw cycle effects

Abstract

The embodiment of the present invention discloses a saline soil roadbed structure and construction method that takes into account the effects of freeze-thaw cycles. The saline soil roadbed includes a saline soil layer, a gravel salt barrier layer, a geotextile, an insulation layer, and a slope soil layer. The saline soil layer includes an upper saline soil layer, a middle saline soil layer, and a lower saline soil layer. The gravel salt barrier layer includes a first gravel salt barrier layer and a second gravel salt barrier layer. The geotextile includes a first geotextile and a second geotextile. The saline soil roadbed is provided with an insulation layer to reduce the damage to the roadbed structure caused by water and salt due to freeze-thaw cycles. The roadbed slope is provided with a slope soil layer and vegetation is planted. The growth of vegetation is ensured by a water collection tank and a drip irrigation belt, thereby ensuring the stability of the saline soil roadbed slope. The saline soil layer is provided with a drainage ditch to discharge the water and salt that migrate and enrich in the gravel salt barrier layer to the outside of the saline soil roadbed. The present invention effectively controls the occurrence of saline soil roadbed diseases under the freeze-thaw cycle state, and prolongs the service life of municipal road projects in saline soil areas.

Description

Technical Field

[0001] The present invention relates to the technical field of municipal road engineering, and in particular to a saline soil roadbed structure and a construction method taking freeze-thaw cycle effects into consideration. Background Art

[0002] With the continued rapid advancement of infrastructure construction across China, the overall focus of construction is gradually shifting to the saline soil regions of Northwest China. The unique environmental and climatic conditions of the Northwest region result in significant temperature swings, particularly the extreme temperatures caused by global warming. This conditions saline soil roadbeds with extreme freeze-thaw cycles. As a special type of soil, saline soil is highly sensitive to external factors such as temperature, groundwater, and precipitation. This leads to numerous problems such as frost heave, salt swelling, dissolution, and mudslides, which severely impact the quality of saline soil roadbed construction and cause significant losses to public life and property.

[0003] Traditional saline soil roadbed structures and construction methods primarily minimize roadbed damage by removing water and controlling salt levels. These methods fail to fundamentally and effectively address the problems associated with saline soil roadbeds, which arise from the coupled effects of temperature, moisture, and salinity. Therefore, designing a saline soil roadbed structure and construction method that considers freeze-thaw cycles to address these issues and provide effective technical support for related engineering projects is of great significance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a saline soil roadbed structure and a construction method that take freeze-thaw cycle effects into consideration.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A saline soil roadbed structure taking into account the effects of freeze-thaw cycles includes a saline soil layer, a gravel salt-blocking barrier layer, a geotextile, an insulation layer and a slope soil layer, wherein the saline soil layer includes a lower saline soil layer, a middle saline soil layer and an upper saline soil layer stacked from bottom to top, the gravel salt-blocking barrier layer is arranged between the upper saline soil layer and the middle saline soil layer, and between the middle saline soil layer and the lower saline soil layer, the geotextile is arranged above and below the gravel salt-blocking barrier layer, the insulation layer covers the top of the upper saline soil layer, and the slope soil layers are arranged at both lateral ends of the saline soil layer.

[0007] As a preferred technical solution of the present invention, the pebble gravel salt barrier layer includes a first pebble gravel salt barrier layer and a second pebble gravel salt barrier layer, the first pebble gravel salt barrier layer is arranged between the upper saline soil layer and the middle saline soil layer, the second pebble gravel salt barrier layer is arranged between the middle saline soil layer and the lower saline soil layer, and the first pebble gravel salt barrier layer and the second pebble gravel salt barrier layer are arranged from both sides toward the center and downward, and the inclination slope is 2%.

[0008] The above technical solution further comprises a first geotextile and a second geotextile, the first geotextile is provided with two layers and respectively covers above and below the first gravel salt barrier layer, the second geotextile is provided with two layers and respectively covers above and below the second gravel salt barrier layer, and the inclination gradient of the first geotextile and the second geotextile is 2%.

[0009] Furthermore, in the above technical solution, the first geotextile and the second geotextile are made of SNG-PP-300 polypropylene needle-punched non-woven geotextile, and the reverse wrapping anchoring length of the geotextile is 2m.

[0010] The above technical solution further features drainage ditches at the toe of the first and second gravel salt barrier layers, running along the saline soil roadbed. An interception pit is excavated in the slope soil layer, containing a water collection tank. The drainage ditch is connected to the water collection tank via a drainage pipe, and a drip irrigation tape is connected to the drainage outlet on the bottom sidewall of the water collection tank. The drip irrigation tape is laid downward along the surface of the slope soil layer, which has a slope of 1:1.75 and is planted on the surface.

[0011] The above technical solution further features a sloped surface on one side of the top of the water collection tank, with a water collection area at its base. This water collection area is composed of a grid structure formed by multiple hexagonal units connected by filter plates. The hexagonal unit comprises a hexagonal frame with a circular disc at its center. Multiple support rods are positioned between the sidewalls of the disc and the inner wall of the hexagonal frame, and a central column with a spherical top is positioned above the disc. The hexagonal frame is wrapped with a waterproof sheet, the center of which rests on the central column, forming an umbrella-shaped unit with a high center and low edges. The filter plate is positioned between two connected hexagonal frames.

[0012] As another preferred technical solution of the present invention, a slope geogrid is laid between the slope soil layer and the saline soil roadbed. The slope geogrid adopts a bidirectional polypropylene geogrid. A drainage ditch is set at 2m away from the toe of the slope soil layer, and the slope is set to 1:1.5.

[0013] As another preferred technical solution of the present invention, the thermal insulation layer is arranged to tilt upward from both sides toward the center, and the road crown slope is 2%.

[0014] The present invention also provides a construction method for a saline soil roadbed structure taking into account the effects of freeze-thaw cycles, comprising the following steps:

[0015] Step S1: clean the site and perform base treatment, and determine the filling position of the saline soil roadbed and the excavation position of the drainage ditch by measuring and setting out;

[0016] S2. Spread the lower saline soil layer in layers and set up drainage ditches and drainage pipes at the center line of the roadbed. Use a TYD200 bulldozer and a YZ20T roller to level and compact the lower saline soil layer.

[0017] S3. Layer-by-layer paving and compacting of the first gravel salt barrier layer. Before and after completion of the construction, first geotextiles are laid on the upper and lower sides of the first gravel salt barrier layer, and then wrapped and anchored in the reverse direction.

[0018] S4. Repeat the work of S2 and S3 to complete the construction of the middle saline soil layer, the second gravel salt barrier layer, the second geotextile, the upper saline soil layer, the drainage ditch and the drainage pipe in sequence;

[0019] S5. Pour foam concrete on the top of the upper saline soil layer and perform curing after pouring and forming;

[0020] S6. Install slope geogrids on both sides of the saline soil roadbed slope, spread and compact the slope soil layer in layers, dig an interception pit on the slope of the slope soil layer, and install a water collection tank in the interception pit. The bottom of the water collection tank is buried in the slope soil layer and connected to the drainage pipe;

[0021] S7. After the construction of saline soil roadbed is completed, dig drainage ditches.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention sets a gravel salt barrier layer above each saline soil layer. When the external environment is low temperature, the barrier blocks the migration of salt to the frozen surface along with water due to capillary action. When the external environment is high temperature, the barrier blocks the upward migration of water and salt due to transpiration. The barrier is inclined from top to bottom with a slope of 2%, thereby collecting salt water at the foot of the slope and flowing to the drainage ditch, and then flowing to the water collection tank through the drainage pipe. The water collection tank not only collects the salt water moving upward in the saline soil layer, but also collects rainwater through the water collection area at the top, and then irrigates the vegetation on the slope soil layer through the drip irrigation belt, thereby preventing the loss of the slope soil layer and reinforcing the saline soil roadbed slope.

[0024] (2) The present invention sets a geotextile to play the role of filtering, permeability, protection and reinforcement;

[0025] (3) The present invention sets up a drainage ditch to collect the salt, water and groundwater that migrate and enrich in the gravel salt barrier layer due to capillary action and transpiration, and discharge them out of the saline soil roadbed;

[0026] (4) The present invention provides a thermal insulation layer to weaken the ability of water and salt to migrate to the surface of the saline soil roadbed due to capillary action and transpiration, thereby avoiding salt enrichment in the surface of the saline soil roadbed;

[0027] (5) The present invention sets a slope soil layer to reinforce the saline soil roadbed slope, thereby preventing the saline soil roadbed slope from being invaded by precipitation and ensuring the stability of the saline soil roadbed;

[0028] (6) The present invention sets up drainage ditches to collect surface precipitation and drain it out of the saline soil roadbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a saline soil roadbed structure provided by the present invention taking into account the effects of freeze-thaw cycles.

[0030] Figure 2 This is a transverse cross-sectional view of a saline soil roadbed structure that takes into account the effects of freeze-thaw cycles provided by the present invention.

[0031] Figure 3 The figure is a schematic diagram of the slope of a saline soil roadbed structure taking into account the effects of freeze-thaw cycles according to the present invention.

[0032] Figure 4 Schematic diagram of the water collecting tank in the present invention.

[0033] Figure 5 Schematic diagram of the hexagonal frame in the above-mentioned water collecting tank.

[0034] Figure 6 This is a side view of the connection between the above-mentioned hexagonal units in the water collection area and the filter plate.

[0035] Figure 7 Schematic diagram of the filter plate in the above-mentioned water collecting tank.

[0036] In the figure: 1. Saline soil layer; 101. Lower saline soil layer; 102. Middle saline soil layer; 103. Upper saline soil layer; 2. Pebble salt barrier layer; 201. First pebble salt barrier layer; 202. Second pebble salt barrier layer; 3. Geotextile; 301. First geotextile; 302. Second geotextile; 4. Insulation layer; 5. Slope soil layer; 6. Drainage ditch; 7. Drainage pipe; 8. Water collecting tank; 801. Slope; 802. Hexagonal unit; 803. Filter plate; 804. Drainage outlet; 805. Fixed column; 806. Arc filter screen; 9. Intercepting pit; 10. Drainage ditch; 11. Drip irrigation belt; 12. Hexagonal frame; 13. Disc; 14. Support rod; 15. Center column; 16. Fixing hole. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, a saline soil roadbed structure taking into account the effects of freeze-thaw cycles includes a saline soil layer 1, a gravel salt barrier layer, a geotextile, an insulation layer 4, and a slope soil layer 5. The saline soil layer 1 includes an upper saline soil layer 103, a middle saline soil layer 102, and a lower saline soil layer 101; the gravel salt barrier layer includes a first gravel salt barrier layer 201 and a second gravel salt barrier layer 202; and the geotextile includes a first geotextile 301 and a second geotextile 302.

[0039] The fillers in the upper, middle, and lower saline soil layers 103, 102, and 101 are all improved, solidified saline soils with a moisture content close to the optimal range. The fill thickness of the saline soil layer is 200 mm, and the width is widened by 500 mm on each side compared to the design value. The fill height is determined by the actual project. A TYD200 bulldozer and a YZ20T roller are used for the saline soil construction.

[0040] The first and second pebble-stone salt barrier layers 201 and 202 have a particle size distribution range of 2 to 5 mm, a particle size content greater than 75%, and a thickness of 300 to 500 mm. The first and second geotextiles 301 and 302 are SNG-PP-300 needle-punched polypropylene nonwoven geotextiles, and the reverse-wrapped anchorage length of the geotextiles is 2 meters.

[0041] The first pebble gravel salt barrier layer 201 is arranged between the upper saline soil layer 103 and the middle saline soil layer 102, and the second pebble gravel salt barrier layer 202 is arranged between the middle saline soil layer 102 and the lower saline soil layer 101. The first pebble gravel salt barrier layer 201 and the second pebble gravel salt barrier layer 202 are arranged from both sides toward the center and downward, and the inclination slope is 2%.

[0042] The first geotextile 301 is provided in two layers, covering the upper and lower layers of the first gravel salt barrier layer 201, respectively. The second geotextile 302 is provided in two layers, covering the upper and lower layers of the second gravel salt barrier layer 202, respectively. The slope of the first geotextile 301 and the second geotextile 302 is 2%. Therefore, a saline soil roadbed should be provided with at least two layers of gravel salt barrier layers and four layers of geotextiles.

[0043] like Figure 2As shown, a drainage ditch 6 is provided at the foot of the first gravel salt barrier layer 201 and the second gravel salt barrier layer 202 along the direction of the saline soil roadbed, and an interception pit 9 is excavated on the slope soil layer 5. A water collecting box 8 is provided in the interception pit 9. The drainage ditch 6 is connected to the water collecting box 8 through a drainage pipe 7. The drainage port 804 on the bottom side wall of the water collecting box 8 is connected to a drip irrigation belt 11. Figure 3 The drip irrigation belt 11 is laid downward along the surface of the slope soil layer 5, and vegetation is planted on the surface of the slope soil layer 5.

[0044] The insulation layer 4 is arranged upward from both sides toward the center, constructed of foamed concrete with a 2% crown slope. The side slope layer 5 is filled with gravel-containing low-liquid-limit clay, with a thickness of 200 mm and a slope gradient of 1:1.75. The surface of the side slope layer 5 is covered with vegetation. A bidirectional polypropylene geogrid is installed between the side slope layer 5 and the saline soil subgrade. A drainage ditch 10 is located 2 meters from the toe of the side slope layer 5, with a slope gradient of 1:1.5.

[0045] like Figure 4 As shown, a slope 801 is provided on one side of the top of the water collecting box 8, and a water collecting area is provided at the bottom of the slope 801. The water collecting area is a grid structure formed by splicing multiple hexagonal units 802 through filter plates 803. Figure 5 As shown, the hexagonal unit 802 includes a hexagonal frame 12, a disk 13 is arranged in the center of the hexagonal frame 12, a plurality of support rods 14 are arranged between the side wall of the disk 13 and the inner wall of the hexagonal frame 12, and a central column 15 with a spherical top is arranged on the disk 13. The hexagonal frame 12 is wrapped with a waterproof cloth, and the center of the waterproof cloth is pressed against the central column 15, thereby forming an umbrella-shaped unit with a high center and low edges. The filter plate 803 is arranged between the two connected hexagonal frames 12.

[0046] like Figure 5 and Figure 7 As shown, fixing posts 805 are provided on both the front and rear ends of the filter plate 803. These fixing posts 805 connect to the fixing holes 16 on the sidewalls of the hexagonal frame 12, thereby connecting two adjacent hexagonal units 802. This forms a water collection structure composed of multiple small umbrella-like structures connected in series. Rainwater flows along the inclined surface 801 toward the water collection area, passing through the filter plates 803 between adjacent hexagonal units 802 and into the water collection tank 8. When rainwater falls onto the hexagonal units 802, due to their umbrella-like structure, it slides from the top of the umbrella to the bottom of the umbrella, flowing from the filter plates 803 into the water collection tank 8. The water in the water collection tank 8 is then irrigated through the drip irrigation tape 11 to irrigate the surface vegetation, thereby solidifying the slope and preventing the vegetation on the slope from dying due to drought.

[0047] like Figure 3As shown, water collection tanks 8 are installed on the slopes on both sides of the saline soil roadbed, and a water collection tank 8 is also installed on the top of the slope. The top water collection tank 8 is mainly used to collect rainwater. The water collection area at the top of the water collection tank 8 is designed as a structure with multiple hexagonal units 802 connected in sequence by filter plates 803. On the one hand, it can prevent debris such as stones, tree trunks, and leaves from falling into the water collection tank 8 and blocking the drain outlet 804. At the same time, the hexagonal units 802 are designed into an umbrella-like structure to facilitate rainwater collection. This can block debris and achieve the purpose of rapid rainwater collection.

[0048] like Figure 6 As shown, to prevent debris such as stones, tree trunks, and leaves from falling and clogging filter plate 803, a downwardly concave curved filter screen 806 is fixed above filter plate 803. The upper ends of curved filter screen 806 extend and bend toward the tarpaulin on either side, forming inclined sections that align with the tarpaulin's inclination. Debris such as leaves, branches, or stones that fall onto the tarpaulin will slide downward along the tarpaulin's inclination. Because the angle of the inclined sections aligns with the tarpaulin's current position, they will slide down along the inclined sections and onto curved filter screen 806. This prevents clogging filter plate 803 below curved filter screen 806. A gap for rainwater to pass through is left between the inclined sections and the tarpaulin on either side, allowing rainwater to flow smoothly to filter plate 803 below.

[0049] The drip irrigation belt can adopt a three-way structure or a Y-shaped structure.

[0050] The above-mentioned saline soil roadbed construction method comprises the following steps:

[0051] Step S1: clean the site and perform base treatment, and determine the filling position of the saline soil roadbed and the excavation position of the drainage ditch 10 by measuring and setting out;

[0052] S2. Spread the lower saline soil layer 101 in layers and set a drainage ditch 6 and a drainage pipe 7 at the center line of the roadbed. Use a TYD200 bulldozer and a YZ20T roller to level and compact the lower saline soil layer 101 respectively;

[0053] S3, layer by layer paving and compacting the first gravel salt barrier layer 201. Before and after the construction is completed, the first geotextile 301 is laid on the upper and lower sides of the first gravel salt barrier layer 201, and wrapped and anchored in the reverse direction;

[0054] S4, repeat the work of S2 and S3 to complete the construction of the middle saline soil layer 102, the second gravel salt barrier layer 202, the second geotextile 302, the upper saline soil layer 103, the drainage ditch 6 and the drainage pipe 7 in sequence;

[0055] S5, pouring foamed concrete on the top of the upper saline soil layer 103, and curing it after pouring and forming;

[0056] S6. Lay out slope geogrids on both sides of the saline soil roadbed slope, spread and compact the slope soil layer 5 in layers, dig an interception pit 9 on the slope of the slope soil layer 5, and set a water collection tank 8 in the interception pit 9. The bottom of the water collection tank 8 is buried in the slope soil layer 5 and connected to the drainage pipe 7;

[0057] S7. After the saline soil roadbed is constructed, a drainage ditch 10 is excavated and vegetation is planted on the slope.

[0058] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A saline soil roadbed structure taking into account the effects of freeze-thaw cycles, characterized in that: It includes a saline soil layer, a gravel salt barrier layer, a geotextile, an insulation layer and a slope soil layer, wherein the saline soil layer includes a lower saline soil layer, a middle saline soil layer and an upper saline soil layer stacked from bottom to top, the gravel salt barrier layer is arranged between the upper saline soil layer and the middle saline soil layer, and between the middle saline soil layer and the lower saline soil layer, the geotextile is arranged above and below the gravel salt barrier layer, the insulation layer covers the top of the upper saline soil layer, and the slope soil layer is arranged at both ends of the saline soil layer in the horizontal direction; The pebble gravel salt barrier layer includes a first pebble gravel salt barrier layer and a second pebble gravel salt barrier layer. The first pebble gravel salt barrier layer is arranged between the upper saline soil layer and the middle saline soil layer, and the second pebble gravel salt barrier layer is arranged between the middle saline soil layer and the lower saline soil layer. The first pebble gravel salt barrier layer and the second pebble gravel salt barrier layer are arranged from both sides to the center and inclined downward, and the inclination gradient is 2%. A drainage ditch is set up at the foot of the first gravel salt barrier layer and the second gravel salt barrier layer along the direction of the saline soil roadbed, and an interception pit is excavated on the slope soil layer. A water collection tank is set up in the interception pit. The drainage ditch is connected to the water collection tank through a drainage pipe. The drainage outlet on the bottom side wall of the water collection tank is connected to a drip irrigation belt. The drip irrigation belt is laid downward along the surface of the slope soil layer. The slope of the slope soil layer is 1:1.75, and vegetation is planted on the surface. A slope is provided on one side of the top of the water collection tank, and a water collection area is provided at the bottom of the slope. The water collection area is a grid structure formed by multiple hexagonal units spliced ​​together through filter plates; The hexagonal unit includes a hexagonal frame, a disc is arranged in the center of the hexagonal frame, a plurality of support rods are arranged between the side wall of the disc and the inner wall of the hexagonal frame, and a central column with a spherical top is arranged on the disc. The hexagonal frame is wrapped with a waterproof cloth, and the center of the waterproof cloth is pressed against the central column, thereby forming an umbrella-shaped unit with a high center and low edges. The filter plate is arranged between the two connected hexagonal frames.

2. The saline soil roadbed structure considering freeze-thaw cycle effects according to claim 1, characterized in that: The geotextile includes a first geotextile and a second geotextile. The first geotextile is provided with two layers and covers the upper and lower parts of the first gravel salt barrier layer respectively. The second geotextile is provided with two layers and covers the upper and lower parts of the second gravel salt barrier layer respectively. The inclination gradient of the first geotextile and the second geotextile is 2%.

3. The saline soil roadbed structure considering freeze-thaw cycle effects according to claim 2, characterized in that: The first geotextile and the second geotextile are SNG-PP-300 polypropylene needle-punched non-woven geotextile, and the reverse wrapping anchoring length of the geotextile is 2m.

4. The saline soil roadbed structure considering freeze-thaw cycle effects according to claim 1, characterized in that: A slope geogrid is laid between the slope soil layer and the saline soil roadbed. The slope geogrid adopts a bidirectional polypropylene geogrid. A drainage ditch is set 2m away from the toe of the slope soil layer, and the slope is set to 1:1.

5.

5. The saline soil roadbed structure considering freeze-thaw cycle effects according to claim 1, characterized in that: The insulation layer is arranged upward from both sides to the center, and the road crown slope is 2%.

6. A construction method for a saline soil roadbed structure taking freeze-thaw cycle effects into consideration according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step S1: clean the site and perform base treatment, and determine the filling position of the saline soil roadbed and the excavation position of the drainage ditch by measuring and setting out; S2. Spread the lower saline soil layer in layers and set up drainage ditches and drainage pipes at the center line of the roadbed. Use a TYD200 bulldozer and a YZ20T roller to level and compact the lower saline soil layer. S3. Layer-by-layer paving and compacting of the first gravel salt barrier layer. Before and after completion of the construction, first geotextiles are laid on the upper and lower sides of the first gravel salt barrier layer, and then wrapped and anchored in the reverse direction. S4. Repeat the work of S2 and S3 to complete the construction of the middle saline soil layer, the second gravel salt barrier layer, the second geotextile, the upper saline soil layer, the drainage ditch and the drainage pipe in sequence; S5. Pour foam concrete on the top of the upper saline soil layer and perform curing after pouring and forming; S6. Install slope geogrids on both sides of the saline soil roadbed slope, spread and compact the slope soil layer in layers, dig an interception pit on the slope of the slope soil layer, and install a water collection tank in the interception pit. The bottom of the water collection tank is buried in the slope soil layer and connected to the drainage pipe; S7. After the construction of saline soil roadbed is completed, dig drainage ditches.

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