Runway foundation in permafrost region

Abstract

The utility model provides a permafrost region runway foundation which comprises a foundation pit, a first rubble layer and a second rubble layer are arranged in the foundation pit in a replacement mode, the first rubble layer is located above the second rubble layer, a concrete layer is arranged between the first rubble layer and the second rubble layer, and a bidirectional geogrid is arranged in the first rubble layer. The utility model has the following beneficial effects: according to the foundation treatment measure of the permafrost region runway foundation replacement method, after the frost heaving and thaw collapse foundation soil is excavated, the non-frost heaving and thaw collapse block gravel material is backfilled, so that the problems of frost heaving and thaw collapse of the soil of the permafrost region runway foundation thaw collapse foundation can be solved; meanwhile, the deformation coordination measure of the double-layer geogrid and the roller compacted concrete layer is adopted, it is ensured that post-construction settlement and differential settlement of the runway can meet the safe use requirement, the adverse effect of underground water on frozen soil of a runway base is prevented with the assistance of the composite geomembrane anti-seepage measure and the foundation pit side wall transverse drainage blind ditch measure, and certain practical significance and popularization value are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a runway foundation in permafrost region relates to runway foundation treatment technical field in permafrost region, avoid runway foundation in permafrost region and take place frost heaving thaw settlement deformation, influence airport safe operation. BACKGROUND

[0002] In the runway construction in permafrost region, the existence of frost heaving and thaw settlement of the foundation soil can easily cause many types of engineering diseases such as frost heaving and thaw settlement deformation. Once the limit value is exceeded, there is a great potential risk of safe operation of the aircraft, and even the function of the airport runway is lost. After the treatment, groundwater will inevitably invade the foundation. If the infiltration of groundwater cannot be effectively prevented, it will also cause the problems of frost heaving and thaw settlement of the foundation, which will threaten the safe operation of the aircraft. During the construction process of the deep foundation pit by the replacement method, atmospheric precipitation falls into the runway slot, and the frozen soil of the side wall of the foundation pit melts and deforms due to temperature influence. In the past, it was difficult to treat the frost heaving and thaw settlement of the permafrost foundation in the runway construction in cold regions, and engineering problems such as uneven settlement deformation and runway benching occurred.

[0003] The replacement method is often used for treatment of the thaw settlement of the permafrost foundation. In the foundation treatment scheme by the replacement method, the replacement of the crushed stone as the main means can effectively cure the problem of the thaw settlement of the foundation soil, and the control of the mud content can avoid the frost heaving and thaw settlement deformation. The auxiliary deformation coordination structure can achieve the purpose of uniform deformation of the runway structure and enhance the overall structural property of the foundation. The waterproofing measure can effectively avoid the deterioration of the foundation soil due to the infiltration of groundwater into the runway slot. Once the groundwater reaches the height that affects the stability of the runway slot, it can be discharged from the foundation range through the lateral drainage blind ditch. The composite geomembrane heat preservation and anti-seepage structure is arranged on the side wall of the foundation pit during the excavation process, which can avoid the serious melting of the frozen soil of the side wall during construction and also can enhance the water-resisting capacity of the soil foundation during use.

[0004] In summary, the study of the runway foundation in permafrost region can solve the deformation characteristics of the thaw settlement of the permafrost in the foundation, and can prevent the adverse effects of groundwater on the frozen soil of the foundation, which has certain practical significance and popularization value. CONTENT OF THE UTILITY MODEL

[0005] In view of the deficiencies in the prior art, the utility model aims to provide a runway foundation in permafrost region.

[0006] In order to achieve the above-mentioned purpose, the utility model is realized by the following technical scheme:

[0007] The utility model provides a runway foundation in permafrost region, including foundation pit, the backfilling of which is provided with gravel layer one and gravel layer two, gravel layer one is located above gravel layer two, and concrete layer is arranged between gravel layer one and gravel layer two, bidirectional geogrid is arranged in gravel layer one, the top and side wall of foundation pit are provided with composite geomembrane one, and a layer of clay pressure roof is arranged on the composite geomembrane one of top, and one side of foundation pit is provided with transverse drainage blind ditch.

[0008] Further, the transverse drainage blind ditch is composed of composite geomembrane two and gravel layer three, and the gravel layer three is wrapped in the composite geomembrane two.

[0009] Further, the composite geomembrane one is arranged on the top surface of the concrete layer, the top surface of the gravel layer one and the side wall of the foundation pit respectively, and the composite geomembrane two on the transverse drainage blind ditch is overlapped with the composite geomembrane one on the concrete layer.

[0010] Further, the particle size of the gravel in the gravel layer one and the gravel layer two is greater than or equal to 0.2 m, the non-uniformity coefficient Cu is greater than or equal to 5, and the curvature coefficient Cc is 1-3.

[0011] Further, the concrete layer and the bidirectional geogrid constitute a deformation coordination structure.

[0012] Further, the weight of the composite geomembrane one and the composite geomembrane two is greater than 600g / m 3 , the nominal tensile strength in longitudinal and transverse directions is greater than 20kN / m, and the tear strength is greater than 500N.

[0013] Further, the composite geomembrane one and the composite geomembrane two wrap the particle size of 5-10cm.

[0014] The utility model discloses the beneficial effect:

[0015] The non-frozen and thawing block gravel material is backfilled in the foundation pit, the frozen heaving and thawing sinking problem of runway foundation soil quality in permafrost region can be solved, the double-layer geogrid and the deformation coordination measures of the rolling concrete layer are adopted, the post-construction settlement and uneven settlement of the runway can meet the safety use requirement, the anti-seepage measures of the composite geomembrane, the transverse drainage blind ditch measures of the side wall of the foundation pit prevent the adverse effect of underground water on the runway foundation permafrost, and have certain practical significance and popularization value. DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0017] Figure 1 It is a schematic diagram of the overall structure of the runway foundation in the permafrost region according to the present application.

[0018] Figure 2 It is a schematic diagram of the cross-drainage blind ditch section of the runway foundation in the permafrost region according to the present application.

[0019] In the figure: 1, gravel layer one; 2, gravel layer two; 3, concrete layer; 4, two-way geogrid; 5, composite geomembrane one; 6, clay capping layer; 7, cross-drainage blind ditch; 8, gravel layer three; 9, composite geomembrane two. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0021] Please refer to Figures 1-2 The present application provides a technical solution: a runway foundation in a permafrost region, comprising a foundation pit, the foundation pit is filled with gravel layer one 1 and gravel layer two 2, the gravel layer one 1 is located above the gravel layer two 2, a concrete layer 3 is arranged between the gravel layer one 1 and the gravel layer two 2, a two-way geogrid 4 is arranged in the gravel layer one 1, composite geomembrane one 5 is arranged on the top and side wall of the foundation pit, a layer of clay capping layer 6 is arranged on the composite geomembrane one 5 on the top, a cross-drainage blind ditch 7 is arranged on one side of the foundation pit.

[0022] Please refer to Figures 1-2, the transverse drainage blind ditch 7 is composed of a composite geomembrane two 9 and a gravel layer three 8, the gravel layer three 8 is wrapped in the composite geomembrane two 9, the composite geomembrane one 5 is arranged on the top surface of the concrete layer 3, the top surface of the gravel layer one 1 and the side wall of the foundation pit respectively, the composite geomembrane two 9 on the transverse drainage blind ditch 7 is overlapped with the composite geomembrane one 5 on the concrete layer 3, the gravel layer one 1 and the gravel layer two 2 contain mud, the mud content in the gravel layer one 1 is greater than or equal to 5%, the mud content in the gravel layer two 2 is 10%-15%, the gravel particle size in the gravel layer one 1 and the gravel layer two 2 is greater than or equal to 0.2m, the non-uniformity coefficient Cu is greater than or equal to 5, the curvature coefficient Cc is 1-3, the concrete layer 3 and the bidirectional geogrid 4 form a deformation coordination structure, the weight of the composite geomembrane one 5 and the composite geomembrane two 9 is greater than 600g / m 3 , the longitudinal and transverse nominal tensile strength is greater than 20kN / m, the tear strength is greater than 500N, the composite geomembrane one 5 and the composite geomembrane two 9 wrap the particle size of 5-10cm.

[0023] The gravel particle size of the gravel layer is required to be greater than or equal to 0.2m, the non-uniformity coefficient Cu is greater than or equal to 5, the curvature coefficient Cc=1-3, the hard rock saturated uniaxial compressive strength of granite or basalt, diabase and other rocks is greater than 30MPa, the compaction method adopts vibration roller compaction method, the solid volume rate is greater than or equal to 88%, the dry density is greater than or equal to 2.0g / cm 3 , the thickness of the layered virtual filling is 30cm.

[0024] The deformation coordination structure adopts double-layer bidirectional geogrid laid in the track bed, the laying position is that one layer is laid at the bottom surface of the pavement structure layer cushion and 0.5m below the bottom surface, the width of the polypropylene bidirectional geogrid is 4m, the length direction is perpendicular to the longitudinal direction of the runway, the overlapping width of the lap joint is 0.4m, the bidirectional ultimate tensile strength per unit length is greater than or equal to 50kN / m, the elongation rate under the longitudinal and transverse ultimate tensile strength is less than or equal to 15%, the tensile force under 2% elongation of the bidirectional is greater than or equal to 17.5kN / m, the tensile force under 5% elongation is greater than or equal to 35kN / m. The 20cm thick roller compacted concrete layer is arranged at the depth of 6.2m below the pavement elevation, and the 7-day unconfined compressive strength is not less than 15MPa.

[0025] The weight of the composite geomembrane is greater than 600g / m 3 , the longitudinal and transverse nominal tensile strength is greater than 20kN / m, the tear strength is greater than 500N, and it is used as the heat preservation and anti-seepage structure of the foundation pit.

[0026] The underground drainage function is achieved by wrapping hard crushed stone with a particle size of 5-10cm, a mud content of ≥5%, and a saturated uniaxial compressive strength of ≥30MPa in a composite geomembrane and setting it in a transverse drainage blind ditch on the sidewall of the foundation pit at a depth of 6m below the design surface.

[0027] In practice, the foundation of a runway in permafrost regions involves excavating the frost-susceptible and thaw-settling soil and then backfilling it with non-frost-susceptible and thaw-settling crushed stone material. This approach addresses the frost heave and thaw settlement issues of the thaw-settling soil in permafrost regions. Simultaneously, the use of double-layer geogrids and roller-compacted concrete layers to coordinate deformation ensures that post-construction settlement and uneven settlement meet safety requirements. Furthermore, composite geomembrane anti-seepage measures and transverse drainage blind ditches on the sidewalls of the foundation pit prevent adverse effects of groundwater on the permafrost foundation. This approach has significant practical value and potential for wider application.

[0028] The technical solutions in the embodiments of this utility model are described in detail below with reference to the accompanying drawings:

[0029] Based on the distribution depth of thawed permafrost in the runway subgrade, a 17m deep foundation pit was excavated from the design elevation of the runway surface. The slope of the pit sidewalls was 1:1.5, and the bottom width was 54m, which is 3m wider on both sides of the 48m runway width.

[0030] After the foundation pit inspection, in accordance with Figure 1 As shown, composite geomembrane 5 is laid from the top of the pit along the sidewall to 1m inside the bottom of the pit. Composite geomembrane 5 consists of two layers of fabric and one layer of membrane, with a weight greater than 600g / m². 3 The nominal tensile strength in both longitudinal and transverse directions is greater than 20kN / m, the tear strength is greater than 500N, and the overlap width is 20cm.

[0031] The backfilling process begins at the bottom of the excavation pit, with 10%–15% mud content crushed stone being layered and filled to a depth of 6.2m below the design elevation of the pavement. The maximum particle size of the material must be greater than or equal to 0.2m, the coefficient of uniformity Cu greater than or equal to 5, and the coefficient of curvature Cc between 1 and 3. Hard rocks such as granite, basalt, or diabase with a saturated uniaxial compressive strength greater than 30MPa are used. Vibratory compaction is employed, with a solid volume fraction greater than or equal to 88% and a dry density not less than 2.0g / cm³. 3 The layered loose filling is 30cm thick.

[0032] A 20cm thick roller-compacted concrete layer is laid on top of the crushed stone 2 with a mud content of 10%~15%. The unconfined compressive strength after 7 days is not less than 15MPa. The transverse drainage slope is 0.3%~0.5% and the slope is reduced to the side of the lateral drainage blind ditch. After 7 days of curing, a composite geomembrane 5 is laid on top, which effectively overlaps with the composite geomembrane 5 used in the transverse drainage blind ditch 7 to avoid water leakage.

[0033] according to Figure 2As shown, the transverse drainage blind ditch 7 is constructed along the side wall of the foundation pit, for the convenience of mechanical operation, the groove is excavated with a top width of 6 m, the blind ditch is located at a depth of 6 m below the designed ground surface, the runoff slope is 2%, the composite geomembrane 5 is wrapped with the gravel 8, and the cross-sectional size is 1 m x 2 m. The gravel 8 uses hard gravel with a particle size of 5-10 cm, a silt content greater than or equal to 5%, and a rock saturated uniaxial compressive strength greater than 30 MPa.

[0034] According to Figure 1 As shown, 20 cm thick rolled concrete layer and composite geomembrane, layered backfill of 5% silt block gravel 1 to the depth of 1.52 m below the design elevation of the pavement, the maximum particle size of the material is required to be greater than or equal to 0.2 m, the coefficient of uniformity Cu is greater than or equal to 5, the curvature coefficient Cc is 1-3, the hard rock saturated uniaxial compressive strength is greater than 30 MPa, the filling and compaction method uses vibration compaction method, the solid volume fraction is greater than or equal to 88%, and the dry density is not less than 2.0 g / cm 3 , the thickness of the layered virtual filling is 30 cm.

[0035] The layered backfill of 5% silt block gravel is placed to the bottom surface of the pavement structure layer cushion and the position 0.5 m below the bottom surface, each of which is provided with a layer of bidirectional geogrid 4, the length direction is perpendicular to the longitudinal direction of the runway, the overlapping width is 0.4 m, and the metal anchor nail is fixed, the bidirectional ultimate tensile strength per unit length is greater than or equal to 50 kN / m, the elongation rate in the longitudinal and transverse directions is less than or equal to 15%, the tensile force at 2% elongation is greater than or equal to 17.5 kN / m, and the tensile force at 5% elongation is greater than or equal to 35 kN / m.

[0036] In the range of the soil surface area on both sides of the runway, after the backfill of 5% silt block gravel to the position 75 cm below the designed ground surface, the composite geomembrane 5 is wrapped, and the overlapping width with the composite geomembrane 5 of the side wall of the foundation pit is 1 m. The top close to the ground surface is 75 cm thick clay pressure top 6, which is layered and virtually filled with a thickness of 30 cm, and the compaction degree is greater than 95%.

[0037] After the above procedures are completed, the runway surface layer, base layer, and cushion structure are constructed.

[0038] Although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A runway foundation in a permafrost region, characterized in that: The foundation pit includes a first layer of crushed stone (1) and a second layer of crushed stone (2) filled in the foundation pit. The first layer of crushed stone (1) is located above the second layer of crushed stone (2). A concrete layer (3) is provided between the first layer of crushed stone (1) and the second layer of crushed stone (2). A bidirectional geogrid (4) is provided in the first layer of crushed stone (1). A composite geomembrane (5) is provided on the top and side walls of the foundation pit. A clay layer (6) is provided on the top of the composite geomembrane (5). A transverse drainage ditch (7) is provided on one side of the foundation pit.

2. The runway foundation in permafrost regions according to claim 1, characterized in that: The transverse drainage blind ditch (7) is composed of a composite geomembrane two (9) and a crushed stone layer three (8), with the crushed stone layer three (8) wrapped inside the composite geomembrane two (9).

3. The runway foundation in a permafrost region according to claim 2, characterized in that: The first composite geomembrane (5) is respectively set on the top surface of the concrete layer (3), the top surface of the first crushed stone layer (1) and the side wall of the foundation pit. The second composite geomembrane (9) on the transverse drainage blind ditch (7) overlaps with the first composite geomembrane (5) on the concrete layer (3).

4. The runway foundation in a permafrost region according to claim 3, characterized in that: The particle size of the crushed stone in the first crushed stone layer (1) and the second crushed stone layer (2) is greater than or equal to 0.2m, the non-uniformity coefficient Cu is greater than or equal to 5, and the curvature coefficient Cc is 1-3.

5. A runway foundation in a permafrost region according to claim 4, characterized in that: The concrete layer (3) and the bidirectional geogrid (4) constitute a deformation-coordinated structure.

6. A runway foundation in a permafrost region according to claim 5, characterized in that: The composite geomembrane one (5) and the composite geomembrane two (9) have a weight greater than 600 g / m³. 3 The nominal tensile strength in both longitudinal and transverse directions is greater than 20 kN / m, and the tear strength is greater than 500 N.

7. A runway foundation in a permafrost region according to claim 6, characterized in that: The composite geomembrane one (5) and the composite geomembrane two (9) encapsulate particles with a diameter of 5-10 cm.

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