Geomembrane wrapped macadam / high polymer macadam composite pile-closed dimension stone composite roadbed structure in permafrost region

Abstract

The invention discloses a geomembrane wrapped gravel / high polymer gravel composite pile-closed dimension stone composite roadbed structure in a permafrost region, and relates to a gravel pile-closed dimension stone composite roadbed structure in a permafrost region. The technical problem that at present, it is difficult to effectively cool and reinforce the permafrost foundation at the same time is solved. The low-heat-release high polymer gravel filler is used, the sealing effect of the pile bottom can be guaranteed together with the geomembrane, water infiltration is prevented, meanwhile, the low-heat-release high polymer can reduce thermal disturbance to permafrost, and the bearing capacity of the pile end is enhanced; the geomembrane wrapped macadam / high polymer macadam composite pile-closed dimension stone composite roadbed structure in the permafrost region has the effects of foundation cooling and reinforcement, roadbed thaw collapse caused by permafrost temperature rising and melting can be reduced, and the overall bearing capacity of a composite foundation is also enhanced; settlement deformation of a seasonal active layer above the permafrost layer is reduced, and two purposes are achieved.

Description

Technical Field

[0001] The invention relates to a crushed stone pile-sealed block stone composite roadbed structure in permafrost areas. Background Art

[0002] Under the background of global warming, highway subgrades in permafrost areas often have serious uneven settlement. In order to alleviate the problems caused by permafrost settlement, the block stone subgrade has been widely used in permafrost areas and has become a typical special subgrade structure in permafrost areas. Its characteristics are that there are a large number of pores inside the block stone, and the air inside can play an active cooling effect under the action of convective heat transfer. Studies have shown that even if the roadbed slope is covered by wind and snow to prevent the inflow of external airflow, the pores inside the crushed stone can still produce convective heat transfer under the action of temperature gradient to achieve the purpose of cooling. However, this method still has the problem of being unable to directly transfer cold energy to the permafrost layer for cooling. The cold energy transfer process needs to pass through the active active layer, and there is serious cold energy attenuation. At the same time, the melting settlement and creep deformation of the permafrost foundation seriously restrict the safe and stable operation of the highway subgrade, and it is necessary to use appropriate methods to reinforce the foundation. Concrete piles are currently widely used in permafrost areas to reinforce foundations. However, due to the heat release of cement hydration, the permafrost will often be warmed and melted, and it is difficult to actively cool the permafrost foundation. In order to take into account the effects of permafrost cooling and foundation reinforcement at the same time, a new composite foundation structure needs to be designed to meet the use needs of permafrost areas.

[0003] For soft soil foundations, geogrid reinforced gravel piles are a commonly used foundation reinforcement method. Patent CN202110116353.8 discloses a reinforced gravel pile-supported EPS lightweight embankment structure and construction method in soft soil areas; Patent CN202311223601.4 discloses a method for regional reinforcement of liquefied lateral large deformation foundations by reinforced gravel piles combined with grouting. These inventions apply reinforced gravel piles to soft foundations with high water content, utilizing the drainage function of the pores in the gravel piles, but after the pile body is filled with water, the convective heat exchange of air cannot be completed in the gravel piles. Patent CN202010812169.2 discloses a reinforced hot-melt pile / reinforced gravel pile composite roadbed structure in degraded permafrost areas. This structure is mainly used for active melting of frozen soil and foundation drainage, and also does not have the effect of active cooling. Therefore, the currently disclosed reinforced gravel piles use geogrids or woven geotextiles as the wrapping reinforcement material, and their main function is limited to drainage, and they cannot have a cooling effect on permafrost foundations. Summary of the invention

[0004] The present invention aims to solve the current technical problem that it is difficult to effectively cool and reinforce permafrost foundations at the same time, and to provide a geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas.

[0005] The permafrost region geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure of the present invention comprises, from bottom to top, a permafrost foundation 1, a geomembrane-wrapped gravel / polymer gravel composite pile, an unfrozen foundation 3, a drainage sand cushion layer 4, a closed block stone roadbed 5, a pavement base layer 6 and a pavement surface layer 7;

[0006] The outside of the geomembrane-wrapped gravel / polymer gravel composite pile is a hollow geomembrane cylinder 9, and the inner cavity is divided into two parts, the lower part is a mixed part 8 of polymer and gravel, the polymer is a low-exothermic polymer, and the polymer bonds the gravel and the geomembrane together through solidification, and the mixed part 8 of polymer and gravel penetrates into the permafrost foundation 1 to play the effect of sealing the pile body and increasing the end bearing effect; above the mixed part 8 of polymer and gravel is a pure gravel part 2, the lower end of the pure gravel part 2 penetrates into the permafrost foundation 1, and the upper end of the mixed part 8 of polymer and gravel is in close contact with the lower end of the pure gravel part 2; the pure gravel part 2 passes through the unfrozen foundation 3 and the drainage sand cushion layer 4 in turn, and the top of the pure gravel part 2 is located in the closed block stone roadbed 5; the side of the closed block stone roadbed 5 is sealed with asphalt mortar to prevent external moisture from penetrating into the foundation.

[0007] The present invention selects a low-exothermic polymer, which releases little heat when solidifying, and can avoid the melting of permafrost as much as possible. The rapid bonding effect of the polymer during solidification is used to bond the crushed stone and the geomembrane together, thereby achieving a sealing effect on the lower part. At the same time, the polymer can increase the strength of the crushed stone and improve the bearing capacity of the pile end.

[0008] The low exothermic polymer of the present invention is specifically a low exothermic polyurethane material, which is an existing material. Reference can be made to patent CN115467208B. Like ordinary two-component polyurethane materials, it is a two-component non-aqueous reactive polyurethane composed of polyols and isocyanates as main reaction components, and is made by adding appropriate amounts of foaming and catalysts. While continuing the excellent properties of ordinary two-component polyurethane materials, this material also has the advantages of low heat release during the reaction process and little impact on the temperature environment around the grouting area. It can be used as a grouting material for engineering repair in frozen soil areas.

[0009] The geomembrane-wrapped gravel / polymer gravel composite piles, the permafrost foundation 1 and the unfrozen foundation 3 together form a composite foundation, which effectively improves the bearing capacity of the permafrost foundation.

[0010] The upper part of the geomembrane-wrapped gravel / polymer gravel composite pile penetrates the unfrozen soil foundation 3 and the drainage sand cushion layer 4, and is directly connected to the closed block stone roadbed 5, forming a block stone roadbed-reinforced gravel pile through-air convection heat exchange channel. The drainage sand cushion layer 4 can prevent moisture in the unfrozen soil foundation 3 from rising and entering the roadbed and pile structure.

[0011] The road base layer 6 and the road surface layer 7 are paved in layers on the closed block stone roadbed 5 to bear the effect of traffic load.

[0012] The construction process of the geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas of the present invention is as follows:

[0013] Step 1: First, determine the distribution of permafrost along the proposed highway, determine the upper limit of permafrost and permafrost temperature through drilling, determine the length, diameter, pile spacing and layout of geomembrane-wrapped gravel / polymer gravel composite piles based on on-site survey data, and ensure the bearing capacity of the foundation through mechanical calculations;

[0014] Step 2: Choose a time period when the temperature is below 0°C to carry out pile foundation construction to minimize thermal disturbance to the permafrost foundation 1, clean and level the surface of the proposed roadbed, lay a 30 cm thick drainage sand cushion layer 4 and compact it, then drill holes at the corresponding pile hole positions and carefully remove the soil in the holes, and immediately lower the pre-made double-sided composite geomembrane sleeve 9 after drilling, and ensure that the top of the sleeve is higher than the top surface of the drainage sand cushion layer 4;

[0015] Step 3: insert a casing into the double-sided composite geomembrane sleeve, and pour a mixture of polymer and gravel prepared in advance into the hole along the casing. The two can be mixed in advance and the gravel is immersed in the polymer. The polymer is a low exothermic polymer; after filling to the elevation, pull out the casing. The filling height of the mixed part 8 of polymer and gravel is 50cm. Naturally solidify for 24 hours. The rapid bonding effect of the polymer bonds the gravel and the geomembrane together, which has the effect of sealing the lower part;

[0016] Step 4: Continue to fill the hole with gravel in layers and tamp it appropriately until it reaches the top surface of the drainage sand cushion layer 4. During the construction process, ensure that no water is poured into the gravel pile. After the gravel pile construction is completed, level the site again and level the drainage sand cushion layer 4. If the geomembrane sleeve on the pile top is too long, it can be properly cut;

[0017] Step 5: After the pile foundation is constructed, a closed block stone roadbed 5 is built on top of the pile foundation and compacted. After the roadbed is filled, asphalt mortar is applied to the side slopes of the closed block stone roadbed 5 to seal the block stone roadbed laterally to prevent water infiltration.

[0018] Step 6: After the roadbed is constructed, the road base layer 6 and the road surface layer 7 are layered on the structure.

[0019] Beneficial effects of the present invention:

[0020] 1. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas of the present invention is suitable for highway roadbed construction in permafrost areas. The convection heat exchange process of the internal gas can be completed through the external closure formed by the geomembrane-wrapped gravel pile and the block stone roadbed and the internal porous medium channel, so that the gas convection cooling effect is extended to the permafrost layer, which has a more direct and efficient cooling effect;

[0021] 2. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas described in the present invention uses a double-sided composite geomembrane as a wrapping reinforcement material, which can prevent moisture in the foundation from penetrating into the gravel pile and destroying the gas flow channel while enhancing the strength of the pile body;

[0022] 3. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas of the present invention uses low-exothermic polymer gravel filler underneath, which can ensure the sealing effect of the pile bottom together with the geomembrane to prevent water infiltration. At the same time, the low-exothermic polymer can reduce the thermal disturbance to the permafrost and enhance the bearing capacity of the pile end;

[0023] 4. The geomembrane-wrapped gravel / polymer gravel composite pile-sealed block stone composite roadbed structure in permafrost areas described in the present invention has the effects of both foundation cooling and reinforcement, can reduce the thawing settlement of the roadbed caused by the warming and melting of permafrost, and also enhance the overall bearing capacity of the composite foundation, reducing the settlement and deformation of the seasonal active layer above the permafrost layer, thus killing two birds with one stone. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in a permafrost region in a specific implementation method 1;

[0025] Figure 2 It is a schematic diagram of the interior of a geomembrane-wrapped gravel / polymer gravel composite pile in a first specific implementation mode;

[0026] Figure 3 It is a schematic diagram of the appearance of the hollow geomembrane cylinder 9 in the first specific implementation mode. DETAILED DESCRIPTION

[0027] Specific implementation method 1: This implementation method is a geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas, such as Figure 1 , Figure 2and Figure 3 As shown, from bottom to top, there are permafrost foundation 1, geomembrane-wrapped crushed stone / polymer crushed stone composite piles, unfrozen foundation 3, drainage sand cushion layer 4, closed block stone roadbed 5, pavement base layer 6 and pavement surface layer 7;

[0028] The outside of the geomembrane-wrapped gravel / polymer gravel composite pile is a hollow geomembrane cylinder 9, and the inner cavity is divided into two parts, the lower part is a mixed part 8 of polymer and gravel, the polymer is a low-exothermic polymer, and the polymer bonds the gravel and the geomembrane together through solidification, and the mixed part 8 of polymer and gravel penetrates into the permafrost foundation 1 to play the effect of sealing the pile body and increasing the end bearing effect; above the mixed part 8 of polymer and gravel is a pure gravel part 2, the lower end of the pure gravel part 2 penetrates into the permafrost foundation 1, and the upper end of the mixed part 8 of polymer and gravel is in close contact with the lower end of the pure gravel part 2; the pure gravel part 2 passes through the unfrozen foundation 3 and the drainage sand cushion layer 4 in turn, and the top of the pure gravel part 2 is located in the closed block stone roadbed 5; the side of the closed block stone roadbed 5 is sealed with asphalt mortar to prevent external moisture from penetrating into the foundation.

[0029] The construction process of the geomembrane-wrapped gravel / polymer gravel composite pile-sealed block stone composite roadbed structure in permafrost regions of the first specific implementation method is as follows:

[0030] Step 1: First, determine the distribution of permafrost along the proposed highway, determine the upper limit of permafrost and permafrost temperature through drilling, determine the length, diameter, pile spacing and layout of geomembrane-wrapped gravel / polymer gravel composite piles based on on-site survey data, and ensure the bearing capacity of the foundation through mechanical calculations;

[0031] Step 2: Choose a time period when the temperature is below 0°C to carry out pile foundation construction to minimize thermal disturbance to the permafrost foundation 1, clean and level the surface of the proposed roadbed, lay a 30 cm thick drainage sand cushion layer 4 and compact it, then drill holes at the corresponding pile hole positions and carefully remove the soil in the holes, and immediately lower the pre-made double-sided composite geomembrane sleeve 9 after drilling, and ensure that the top of the sleeve is higher than the top surface of the drainage sand cushion layer 4;

[0032] Step 3: insert a casing into the double-sided composite geomembrane sleeve, and pour a mixture of polymer and gravel prepared in advance into the hole along the casing. The two can be mixed in advance and the gravel is immersed in the polymer. The polymer is a low exothermic polymer; after filling to the elevation, pull out the casing. The filling height of the mixed part 8 of polymer and gravel is 50cm. Naturally solidify for 24 hours. The rapid bonding effect of the polymer bonds the gravel and the geomembrane together, which has the effect of sealing the lower part;

[0033] Step 4: Continue to fill the hole with gravel in layers and tamp it appropriately until it reaches the top surface of the drainage sand cushion layer 4. During the construction process, ensure that no water is poured into the gravel pile. After the gravel pile construction is completed, level the site again and level the drainage sand cushion layer 4. If the geomembrane sleeve on the pile top is too long, it can be properly cut;

[0034] Step 5: After the pile foundation is constructed, a closed block stone roadbed 5 is built on top of the pile foundation and compacted. After the roadbed is filled, asphalt mortar is applied to the side slopes of the closed block stone roadbed 5 to seal the block stone roadbed laterally to prevent water infiltration.

[0035] Step 6: After the roadbed is constructed, the road base layer 6 and the road surface layer 7 are layered on the structure.

[0036] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the geomembrane is a double-sided composite geomembrane, that is, a layer of high-strength geotextile is attached to both sides of the geomembrane to prevent moisture from entering the pile structure while preventing gravel from puncturing, thereby ensuring both anti-seepage and reinforcement effects. Other aspects are the same as specific implementation method 1.

[0037] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the height of the geomembrane-wrapped gravel / polymer gravel composite pile is 50 cm. Other aspects are the same as specific implementation method 1 or 2.

[0038] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the mixed part 8 of polymer and crushed stone is prepared by immersing the crushed stone in the polymer first. The rest is the same as specific embodiments 1 to 3.

[0039] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the inner diameter of the geomembrane-wrapped gravel / polymer gravel composite pile is 40 cm. Other aspects are the same as those of specific implementation method 4.

[0040] Specific implementation example 6: This implementation example is different from the specific implementation example 5 in that the distance between the geomembrane-wrapped gravel / polymer gravel composite piles is 1.2 meters. The rest is the same as the specific implementation example 5.

[0041] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that the thickness of the drainage sand cushion layer 4 is 30 cm. The rest is the same as specific embodiment 6.

[0042] Specific implementation example eight: This implementation example is different from specific implementation example seven in that the particle size of the crushed stone is 20 mm to 50 mm. The rest is the same as specific implementation example seven.

[0043] Specific embodiment 9: This embodiment is different from specific embodiment 8 in that the low exothermic polymer is a low exothermic polyurethane material. Other aspects are the same as specific embodiment 8.

[0044] Specific implementation method 10: This implementation method is different from specific implementation method 9 in that the mud content of the crushed stone is less than 10%. Other aspects are the same as specific implementation method 9.

Claims

1. A geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas, characterized in that The geomembrane-wrapped crushed stone / polymer crushed stone composite pile-sealed block stone composite roadbed structure in permafrost areas is, from bottom to top, permafrost foundation (1), geomembrane-wrapped crushed stone / polymer crushed stone composite pile, unfrozen foundation (3), drainage sand cushion layer (4), closed block stone roadbed (5), pavement base layer (6) and pavement surface layer (7); The exterior of the geomembrane-wrapped gravel / polymer gravel composite pile is a hollow geomembrane cylinder (9), the inner cavity of which is divided into an upper and lower part, wherein the lower part is a mixed part (8) of polymer and gravel, the polymer is a low-exothermic polymer, and the polymer bonds the gravel and the geomembrane together through solidification, and the mixed part (8) of polymer and gravel penetrates deeply into the permafrost foundation (1) to seal the pile body and increase the end bearing effect; above the mixed part (8) of polymer and gravel The invention relates to a pure crushed stone part (2), the lower end of which penetrates into the permafrost foundation (1), and the upper end of the mixed part (8) of polymer and crushed stone is in close contact with the lower end of the pure crushed stone part (2); the pure crushed stone part (2) passes through the unfrozen foundation (3) and the drainage sand cushion layer (4) in sequence, and the top of the pure crushed stone part (2) is located in the closed block stone roadbed (5); the side of the closed block stone roadbed (5) is sealed with asphalt mortar to prevent external moisture from penetrating into the foundation.

2. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The geomembrane is a double-sided composite geomembrane, that is, a layer of high-strength geotextile is attached to both sides of the geomembrane.

3. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The height of the geomembrane-wrapped gravel / polymer gravel composite pile is 50 cm.

4. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The mixed part (8) of polymer and crushed stone is prepared by first immersing the crushed stone in the polymer.

5. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The inner diameter of the geomembrane-wrapped gravel / polymer gravel composite pile is 40 cm.

6. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The distance between the geomembrane-wrapped gravel / polymer gravel composite piles is 1.2 meters.

7. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The thickness of the drainage sand cushion layer (4) is 30 cm.

8. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The particle size of the crushed stone is 20mm to 50mm.

9. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 8, characterized in that The particle size of the crushed stone is 30 mm to 40 mm.

10. The geomembrane-wrapped gravel / polymer gravel composite pile-enclosed block stone composite roadbed structure in permafrost areas according to claim 1, characterized in that The mud content of the crushed stone is less than 10%.

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