Soft soil foundation structure for airport runway and construction method

Abstract

The invention relates to the technical field of soft soil area foundation construction, in particular to a soft soil foundation structure for an airport runway and a construction method.The soft soil foundation structure comprises a vertical water-resisting layer and a horizontal water-resisting layer; the vertical water-resisting layer extends into the water-resisting soil layer from the top face of the soft soil layer in the vertical direction. The horizontal water-resisting layer is arranged at the top of the vertical water-resisting layer; the vertical water-resisting layers comprise a plurality of first vertical water-resisting layers which are arranged at equal intervals and a plurality of second vertical water-resisting layers which are vertically intersected with the first vertical water-resisting layers; and the soft soil layer is divided into a plurality of independently sealed waterproof units by the plurality of first vertical waterproof layers, the plurality of second vertical waterproof layers, the horizontal waterproof layer and the waterproof soil layer. The vertical water-resisting layer and the horizontal water-resisting layer are arranged to form a non-drainage sealed space for the soft soil, a drainage path of the soft soil layer is cut off, and the effect that the soft soil foundation structure does not settle due to drainage consolidation of the soft soil layer is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation construction in soft soil areas, and particularly to a soft soil foundation structure and construction method for airport pavements. Background Art

[0002] Soft soil layers refer to soil layers with low strength, high compressibility, high water content, and poor drainage in their natural state. Generally, they are difficult to be directly used as building foundations and need to be artificially reinforced to meet engineering requirements. In soft soil areas, in order to avoid excessive settlement during the service period of airport runways, the soft soil layers are treated during the airport construction period. The existing treatment methods mainly include shallow replacement, shallow dynamic compaction, preloading, cement-soil mixing pile composite foundation, etc. However, at present, the thickness of the soil layer treated shallowly for soft soil is mainly determined by experience. This method will cause large settlement of the airport runway due to too shallow soil layer treatment thickness during the later use process. The preloading method for treating soft soil has a too long treatment period and unsatisfactory treatment effect, and large settlement will occur during the later use process. While using the cement-soil mixing pile composite foundation method has a good treatment effect on soft soil layers, but the cost is too high for large-area use.

[0003] Therefore, to solve the above deficiencies, the present invention provides a soft soil foundation structure for airport pavements to avoid settlement caused by drainage consolidation of soft soil layers. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a soft soil foundation structure and construction method for airport pavements, which solves the technical problem that the existing soft soil layers will cause large settlement of the airport runway due to drainage consolidation.

[0006] (2) Technical Solutions

[0007] To achieve the above object, the main technical solutions adopted by the present invention include:

[0008] A soft soil foundation structure for airport pavements includes a vertical water barrier layer and a horizontal water barrier layer;

[0009] The vertical water barrier layer extends from the top surface of the soft soil layer to the water-resistant soil layer along the vertical direction; the horizontal water barrier layer is arranged on the top of the vertical water barrier layer;

[0010] The vertical water barrier layer includes a plurality of first vertical water barrier layers arranged at equal intervals and a plurality of second vertical water barrier layers vertically intersecting with the first vertical water barrier layers. The plurality of first vertical water barrier layers, the plurality of second vertical water barrier layers, the horizontal water barrier layer, and the water-resistant soil layer divide the soft soil layer into a plurality of independent and sealed water barrier units.

[0011] The outer edge of the horizontal waterproof layer extends to the outside of the vertical waterproof layer, and the extension length is not less than 3m.

[0012] Multiple layers of geogrids are arranged inside the horizontal waterproof layer, and each layer of geogrids is arranged at equal intervals.

[0013] The distance between adjacent first vertical waterproof layers is less than or equal to the height of the first vertical waterproof layer, and less than or equal to 10m;

[0014] The distance between adjacent second vertical waterproof layers is less than or equal to the height of the second vertical waterproof layer, and less than or equal to 10m.

[0015] The lower end of the vertical waterproof layer extends into the waterproof soil layer by at least 3m.

[0016] The horizontal waterproof layer and the vertical waterproof layer are both made of waterproof materials.

[0017] A construction method for a soft soil foundation structure, applied to the above-mentioned soft soil foundation structure, comprises the following steps:

[0018] Step 1: Select the construction area;

[0019] Step 2: forming a plurality of first vertical waterproof layers arranged in parallel at a preset interval, wherein the first vertical waterproof layers extend from the top surface of the soft soil layer to the waterproof soil layer;

[0020] Step 3: forming a plurality of second vertical waterproof layers arranged in parallel at a preset interval, wherein the second vertical waterproof layers intersect the first vertical waterproof layers vertically and extend from the top surface of the soft soil layer to the waterproof soil layer;

[0021] Step 4: After the first vertical waterproof layer and the second vertical waterproof layer are cured to the preset strength, premixed fluid cement soil or low-grade waterproof concrete is laid in layers on the first vertical waterproof layer, the second vertical waterproof layer and the top surface of the soft soil layer, and the layers are vibrated and compacted, or dry hard cement mixed soil is laid in layers, and the layers are rolled and compacted, and geogrids are laid to form a horizontal waterproof layer.

[0022] The specific method for forming the first vertical waterproof layer and the second vertical waterproof layer in step 2 and step 3 is as follows:

[0023] S1: Inject cement slurry into the soft soil layer and the water-repellent soil layer to fully mix the cement slurry and the soil to form cement piles;

[0024] S2: Repeat step S1 to continuously form a plurality of cement piles along the first direction / the second direction, wherein adjacent cement piles are overlapped and interlocked according to a preset width to form a first vertical waterproof layer / a second vertical waterproof layer.

[0025] Among them, the specific methods for forming the first vertical water barrier layer and the second vertical water barrier layer in Step 2 and Step 3 are as follows:

[0026] S1: Form a groove with equal width in the soft soil layer and the water-resistant soil layer, and inject premixed fluidized cement soil into the groove to form a continuous and equally wide first vertical water barrier layer / second vertical water barrier layer.

[0027] The selection method of the construction area is as follows: There is a continuous and stable water-resistant soil layer below the soft soil layer, the thickness of the water-resistant soil layer is greater than or equal to 5m, and the permeability coefficient of the water-resistant soil layer is less than or equal to 10 -7 cm / s.

[0028] (III) Beneficial effects

[0029] The beneficial effects of the present invention are: The embodiments of the present invention provide a soft soil foundation structure for an airport runway. By setting a vertical water barrier layer and a horizontal water barrier layer to form a non-drainage sealed space for the soft soil, the drainage path of the soft soil layer is truncated, so as to achieve the effect that the soft soil foundation structure does not settle due to the drainage consolidation of the soft soil layer.

[0030] Among them, the main function of the vertical water barrier layer is water isolation, rather than a load-bearing structure. In this way, the vertical water barrier layer can adopt a larger layout spacing, thereby reducing the project cost and making the project cost lower than the treatment method of traditional composite foundations. At the same time, compared with the traditional foundation, the structure of the soft soil foundation structure is simpler, so that the construction period of the soft soil foundation structure is shorter.

[0031] Among them, a geogrid is provided in the horizontal water barrier layer to improve the strength and integrity of the horizontal water barrier layer to meet the construction and use requirements of the subsequent airport runway surface layer. The outer edge of the horizontal water barrier layer extends to the outside of the vertical water barrier layer to effectively seal the connection nodes of the horizontal water barrier layer and the vertical water barrier layer. Description of the drawings

[0032] Figure 1 It is a schematic cross-sectional structure diagram of the soft soil foundation structure of the present invention;

[0033] Figure 2 It is a schematic top view structure diagram of the soft soil foundation structure of the present invention.

[0034]

Description of the reference numerals

[0035] 1: Horizontal water barrier layer;

[0036] 2: Vertical water barrier layer;

[0037] 21: First vertical water barrier layer;

[0038] 22: Second vertical water barrier layer;

[0039] 3: Impervious soil layer;

[0040] 4: Geogrid;

[0041] 5: Pavement layer;

[0042] 6: Soft soil layer;

[0043] 61: Impervious unit. Detailed implementation manners

[0044] For better explaining the present invention for easy understanding, the present invention will be described in detail below in conjunction with the accompanying drawings through specific implementation manners. Among them, the orientation nouns such as "upper", "lower", etc. mentioned in this article are Figure 1 taken as a reference for the orientation of

[0045] The soil layers in the soft soil area are successively the soft soil layer 6 and the impervious soil layer 3 from top to bottom. The present application aims to form a soft soil foundation structure on this specific soft soil layer 6 so that the soft soil foundation structure can be used as the foundation of the airport runway and will not produce large settlements due to drainage consolidation during the use of the airport runway.

[0046] The meaning of the above "drainage consolidation" is: According to the soil consolidation theory, in a saturated soil mass under pressure, the pore water gradually drains out, the void ratio decreases, resulting in the compression of the soil mass volume.

[0047] The present invention provides a soft soil foundation structure for an airport runway. A plurality of vertical impervious layers 2 are poured in the soft soil layer 6 to separate the soft soil layer 6, and a horizontal impervious layer 1 is poured on the top of the vertical impervious layer 2 to form an undrained closed space for the soft soil, so as to cut off the drainage path of the soft soil layer 6 and achieve the effect of not generating settlements due to the drainage consolidation of the soft soil layer 6.

[0048] To better understand the above technical solution, the exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more clear and thorough understanding of the present invention and to be able to fully convey the scope of the present invention to those skilled in the art.

[0049] See the attached Figure 1, an embodiment of the present invention provides a soft soil foundation structure for airport pavements, which includes a plurality of vertical water barriers 2 cast vertically in the soft soil layer 6 and a horizontal water barrier 1 cast on the top of the vertical water barriers 2. The vertical water barriers 2 and the horizontal water barrier 1 are integrated, the vertical water barriers 2 are perpendicular to the horizontal water barrier 1, and the vertical water barriers 2 extend from the top surface of the soft soil layer 6 into the water-resistant soil layer 3, so that the vertical water barriers 2 and the horizontal water barrier 1 divide the soft soil layer 6 to form a plurality of independent and sealed water barrier units 61, thereby truncating the drainage path of the soft soil layer 6.

[0050] The vertical water barrier 2 includes a plurality of first vertical water barriers 21 arranged at equal intervals in the first direction and a plurality of second vertical water barriers 22 arranged at equal intervals in the second direction. The first direction is perpendicular to the second direction, and the first vertical water barriers 21 and the second vertical water barriers 22 form a grid-shaped structure filled with soft soil in the soft soil layer 6, achieving effective water isolation for the soft soil.

[0051] The spacing between adjacent vertical water barriers 2 in the same direction is determined according to the treatment depth of the soft soil layer 6, and the spacing is less than or equal to the treatment depth and less than or equal to 10 m. Since the main function of setting the vertical water barrier 2 is water isolation and it is not used as a load-bearing structure, therefore, the layout spacing of the vertical water barrier 2 is relatively large, reducing the project cost and shortening the construction period.

[0052] The lower ends of the first vertical water barriers 21 and the second vertical water barriers 22 extend into the water-resistant soil layer 3 located below the soft soil layer 6, and the depth of penetration into the water-resistant soil layer 3 is at least 3 m, so that the vertical water barrier 2 can completely truncate the drainage path of the soft soil in the horizontal direction and improve the sealing effect on the soft soil.

[0053] The horizontal water barrier 1 is laid horizontally on the tops of the first vertical water barriers 21 and the second vertical water barriers 22. The horizontal water barrier 1 and the first vertical water barriers 21 and the second vertical water barriers 22 are combined to form a plurality of independent and closed non-drainage spaces, which can completely truncate the drainage path of the soft soil layer 6, achieving the effect that the soft soil layer 6 does not settle due to drainage consolidation.

[0054] The horizontal water barrier 1 is provided with geogrids 4. The geogrids 4 are arranged along the horizontal direction. In this embodiment, the horizontal water barrier 1 is provided with two layers of geogrids 4, and the two layers of geogrids 4 are arranged at equal intervals, which are used to improve the strength and integrity of the horizontal water barrier 1.

[0055] The outer edge of the horizontal water barrier 1 extends to the outside of the vertical water barrier 2, and the extension length is not less than 3 m. Since the connection nodes of the horizontal water barrier 1 and the vertical water barrier 2 are relatively weak in water isolation, therefore, measures such as outward expansion and increasing the geogrids 4 are comprehensively considered to effectively seal the connection nodes of the horizontal water barrier 1 and the vertical water barrier 2.

[0056] The horizontal water - impermeable layer 1 and the vertical water - impermeable layer 2 are both made of water - impermeable materials. In this embodiment, the horizontal water - impermeable layer 1 and the vertical water - impermeable layer 2 are cast integrally with cement - soil. Using cement - soil materials for construction is more convenient and more economical in terms of price.

[0057] The thickness of the vertical water - impermeable layer 2 is determined comprehensively according to factors such as construction conditions and site environment, and the thickness is between 0.6m and 1.5m.

[0058] The horizontal water - impermeable layer 1 is determined comprehensively considering factors such as the strength of cement - soil, the condition of soft soil layers, and the spacing between the first vertical water - impermeable layer 21 and the second vertical water - impermeable layer 22, and the thickness is greater than or equal to 2m.

[0059] The permeability coefficients of the vertical water - impermeable layer 2 and the horizontal water - impermeable layer 1 are less than or equal to 10 -7 cm / s. By setting the vertical water - impermeable layer 2 and the horizontal water - impermeable layer 1 with low permeability coefficients, a horizontal and vertical anti - seepage barrier is formed for the soft soil layer 6, significantly reducing the seepage pressure of groundwater, effectively blocking the seepage of groundwater, and improving the foundation stability.

[0060] The compressive strength of the vertical water - impermeable layer 2 is greater than or equal to 0.8MPa, and the compressive strength of the horizontal water - impermeable layer 1 is greater than or equal to 2MPa, forming the effect of a hard - shell layer, which can meet the subsequent construction and use requirements of the airport runway.

[0061] In the application scenario of the airport runway, the thickness of the water - retaining soil layer 3 in the construction area of the airport runway is greater than or equal to 5m, and the permeability coefficient is less than or equal to 10 -7 cm / s.

[0062] The top of the horizontal water - impermeable layer 1 is provided with a runway surface layer 5. The runway surface layer 5 is made according to the practices and requirements of the airport apron. The runway surface layer 5 includes a base layer and a surface layer arranged in sequence from bottom to top. The base layer is a semi - rigid layer formed by mixing and compacting aggregates such as gravel and sand with cementitious materials such as cement or lime, which is used to transfer loads, disperse the aircraft wheel loads to the underlying soft soil foundation structure, and resist the cracking of the base layer caused by repeated aircraft loads. At the same time, it reduces the infiltration of rainwater and protects the soft soil foundation structure from water damage.

[0063] The surface layer is the top layer directly bearing the aircraft loads and environmental effects, which is used to resist the impact and wear of aircraft take - off and landing and taxiing, improve the flatness, ensure the taxiing stability of the aircraft, and resist chemical corrosion such as temperature difference, rainwater, and fuel.

[0064] This embodiment of the present invention also provides a construction method for an airport apron, including the following steps:

[0065] Step 1: Select a suitable construction site;

[0066] Below the soft soil layer 6 in the construction area, there is a continuous and stable water - insulating soil layer 3. The thickness of the water - insulating soil layer 3 is greater than or equal to 5m, and the permeability coefficient is less than or equal to 10 -7 cm / s, enabling the construction site to meet the construction conditions of the airport runway.

[0067] Step 2: Form multiple first vertical water - insulating layers 21 arranged in parallel at a preset spacing. The first vertical water - insulating layers 21 extend from the top surface of the soft soil layer 6 into the water - insulating soil layer 3.

[0068] Step 3: Form multiple second vertical water - insulating layers 22 arranged in parallel at a preset spacing. The second vertical water - insulating layers 22 intersect perpendicularly with the first vertical water - insulating layers 21 and extend from the top surface of the soft soil layer 6 into the water - insulating soil layer 3.

[0069] Among them, the specific methods for forming the first vertical water - insulating layer 21 and the second vertical water - insulating layer 22 in the above - mentioned Step 2 and Step 3 are as follows:

[0070] S1: Inject cement slurry into the soft soil layer 6 and the water - insulating soil layer 3 to fully mix the cement slurry and the soil to form cement piles.

[0071] The formation method of the cement piles is as follows: Through a deep mixer drilling, the drill bit successively passes through the soft soil layer 6 to reach the preset depth of the water - insulating soil layer 3. During the drilling process, cement slurry is injected synchronously to enable the full mixing of the cement slurry and the soil, thereby forming cement piles.

[0072] S2: Repeat S1, continuously form multiple cement piles along the first direction / second direction. The adjacent cement piles overlap and interlock according to a preset width to form the first vertical water - insulating layer 21 / the second vertical water - insulating layer 22.

[0073] In addition, the methods for forming the first vertical water - insulating layer 21 and the second vertical water - insulating layer 22 also include the following:

[0074] Form grooves with equal widths in the soft soil layer 6 and the water - insulating soil layer 3, and inject premixed fluidized cement soil into the grooves to form continuous and equal - width first vertical water - insulating layers 21 / second vertical water - insulating layers 22.

[0075] The above - mentioned grooves are formed by a grooving machine. The depth of the grooves penetrates into the water - insulating soil layer 3, and premixed fluidized cement soil or gelling water - insulating materials such as low - grade concrete are injected into the grooves to form a continuous and equal - width wall.

[0076] It is also possible to use the CSM or TRD construction method to fully stir the in - situ soil and cement slurry to form a continuous cement - soil wall with equal thickness.

[0077] Step 4: After the first vertical water barrier layer 21 and the second vertical water barrier layer 22 are cured to the preset strength, place the ready-mixed flowable soil-cement or low-grade water-proof concrete with fluidity on the top surfaces of the first vertical water barrier layer 21, the second vertical water barrier layer 22 and the soft soil layer 6, vibrate and compact it in layers, or lay dry-hard soil-cement mixture in layers and roll and compact it in layers, and lay the geogrid 4 to form the horizontal water barrier layer 1.

[0078] Among them, the ready-mixed soil-cement is formed by mixing cement slurry and soil according to a preset ratio. The low-grade water-proof concrete is a kind of concrete with a relatively low strength grade (usually C15 or below) and is mainly used for anti-seepage and water-proofing. The geogrid 4 is laid synchronously when the soil-cement is laid in layers, so that the geogrid 4 is covered into the soil-cement.

[0079] By pouring the first vertical water barrier layer 21 and the second vertical water barrier layer 22 first and then pouring the horizontal water barrier layer 1, the soft soil foundation structure is formed into an integral body, improving the integrity of the first vertical water barrier layer 21, the second vertical water barrier layer 22 and the horizontal water barrier layer 1, thereby improving the waterproof performance of the soft soil foundation structure.

[0080] Step 5: Lay the road surface layer 5 on the top of the horizontal water barrier layer 1.

[0081] The embodiment of the present invention provides a soft soil foundation structure for an airport runway. By setting the vertical water barrier layer 2 and the horizontal water barrier layer 1 to form a non-drainage sealed space for the soft soil, the drainage path of the soft soil layer 6 is cut off, so as to achieve the effect that the soft soil foundation structure does not settle due to the drainage consolidation of the soft soil layer 6.

[0082] Among them, the main function of the vertical water barrier layer 2 is water-proofing, rather than a load-bearing structure, enabling the vertical water barrier layer 2 to adopt a larger layout spacing, thereby reducing the project cost and making the project cost lower than the treatment method of the composite foundation. At the same time, since the soft soil foundation structure is simpler than the traditional foundation, the construction period of the soft soil foundation structure is shorter.

[0083] The horizontal water barrier layer 1 is provided with a geogrid 4 to improve the strength and integrity of the horizontal water barrier layer 1 to meet the construction and use requirements of the subsequent airport runway surface layer 5. The outer edge of the horizontal water barrier layer 1 extends to the outside of the vertical water barrier layer 2 to effectively seal the connection nodes of the horizontal water barrier layer 1 and the vertical water barrier layer 2.

[0084] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0085] In the present invention, unless otherwise clearly specified or limited, terms such as "installed", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral one; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium; it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0086] In the present invention, unless otherwise clearly specified or limited, when the first feature is "on" or "under" the second feature, it may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, when the first feature is "above", "over" and "on top of" the second feature, it may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. When the first feature is "under", "beneath" and "underneath" the second feature, it may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0087] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0088] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A soft soil foundation structure for airport runway, characterized in that, It includes a vertical water barrier layer (2) and a horizontal water barrier layer (1); The vertical water barrier layer (2) extends vertically from the top surface of the soft soil layer (6) into the water-resistant soil layer (3); the horizontal water barrier layer (1) is arranged on the top of the vertical water barrier layer (2); The vertical water barrier layer (2) includes a plurality of first vertical water barrier layers (21) arranged at equal intervals and a plurality of second vertical water barrier layers (22) vertically intersecting with the first vertical water barrier layers (21). The plurality of first vertical water barrier layers (21), the plurality of second vertical water barrier layers (22), the horizontal water barrier layer (1) and the water-resistant soil layer (3) divide the soft soil layer (6) to form a plurality of independent and sealed water barrier units (61).

2. The soft soil foundation structure for airport runway according to claim 1, wherein, The outer edge of the horizontal water barrier layer (1) extends to the outside of the vertical water barrier layer (2), and the extension length is not less than 3m.

3. The soft soil foundation structure for airport runway according to claim 2, wherein, A plurality of layers of geogrids (4) are arranged inside the horizontal water barrier layer (1), and each layer of the geogrids (4) is arranged at equal intervals.

4. The soft soil foundation structure for airport runway according to claim 1, wherein, The distance between adjacent first vertical water barrier layers (21) is less than or equal to the height of the first vertical water barrier layer (21) and less than or equal to 10m; The distance between adjacent second vertical water barrier layers (22) is less than or equal to the height of the second vertical water barrier layer (22) and less than or equal to 10m.

5. The soft soil foundation structure for airport runway according to claim 1, wherein, The lower end of the vertical water barrier layer (2) extends into the water-resistant soil layer (3) by at least 3m.

6. The soft soil foundation structure for airport runway according to claim 1, wherein, Both the horizontal water barrier layer (1) and the vertical water barrier layer (2) are made of cementitious water barrier materials.

7. A construction method for a soft soil foundation structure, characterized in that Applied to the soft soil foundation structure according to any one of claims 1-6, it includes the following steps: Step 1: Select the construction area; Step 2: Form a plurality of first vertical water barrier layers (21) arranged in parallel at a preset interval. The first vertical water barrier layers (21) extend from the top surface of the soft soil layer (6) into the water-resistant soil layer (3); Step 3: Form a plurality of second vertical water barrier layers (22) arranged in parallel at a preset interval. The second vertical water barrier layers (22) vertically intersect with the first vertical water barrier layers (21) and extend from the top surface of the soft soil layer (6) into the water-resistant soil layer (3); Step 4: After the first vertical water barrier layer (21) and the second vertical water barrier layer (22) are cured to a preset strength, pre-mixed flowing cement soil is laid in layers on the top surfaces of the first vertical water barrier layer (21), the second vertical water barrier layer (22) and the soft soil layer (6), vibrated and compacted in layers, or dry-hardened cement mixed soil is laid in layers and rolled and compacted in layers, and geogrids (4) are laid to form the horizontal water barrier layer (1).

8. The construction method of the soft soil foundation structure according to claim 7, wherein, Among them, The specific method of forming the first vertical waterproof layer (21) and the second vertical waterproof layer (22) in step 2 and step 3 is as follows: S1: injecting cement slurry into the soft soil layer (6) and the water-repellent soil layer (3) to fully mix the cement slurry and the soil to form a cement pile; S2: Repeat step S1 to continuously form a plurality of cement piles along the first direction / the second direction, wherein adjacent cement piles overlap and interlock according to a preset width to form a first vertical waterproof layer (21) / a second vertical waterproof layer (22).

9. The construction method of an airport runway according to claim 7, characterized in that: Among them, The specific method of forming the first vertical waterproof layer (21) and the second vertical waterproof layer (22) in step 2 and step 3 is as follows: S1: A trough body of equal width is formed in the soft soil layer (6) and the impermeable soil layer (3), and premixed fluidized cement soil is injected into the trough body to form a first vertical impermeable layer (21) / a second vertical impermeable layer (22) of continuous equal width.

10. The construction method of soft soil foundation structure according to claim 7, characterized in that: The method for selecting the construction area is as follows: there is a continuous and stable water-resistant layer (3) below the soft soil layer (6), the thickness of the water-resistant layer (3) is greater than or equal to 5 m, and the permeability coefficient of the water-resistant layer (3) is less than or equal to 10 -7 cm / s.

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