A structural form and stiffness design method for uneven settlement control in high-fill tunnel projects

Abstract

The present invention relates to the technical field of tunnel engineering, and more specifically to a high-fill tunnel foundation structure and design method for controlling uneven settlement. The tunnel foundation structure comprises a bedrock layer, a weak stratum, and an artificial fill layer, arranged sequentially from bottom to top. A tunnel is disposed in the artificial fill layer, and a pile foundation structure is disposed at the bottom of the tunnel. The vertical projection of the tunnel into the artificial fill layer is referred to as a first region. A first buffer layer is disposed in the first region above the tunnel, covering the first region. The artificial fill layers on either side of the first region are referred to as second regions, and a second buffer layer is disposed in the second region. The compressive deformation of the first buffer layer is greater than that of the second buffer layer, and the total compressive deformation of the first region is equal to that of the second region. The elastic modulus or thickness of the first and second buffer layers can be determined through a design calculation method to ensure that the road surface above the foundation remains level, effectively preventing uneven surface settlement.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to a high fill tunnel foundation structure and a design method for controlling uneven settlement. Background Art

[0002] my country's airport engineering has numerous functional requirements, with subways, high-speed railways, and expressways crisscrossing each other. To meet the needs of various functions and achieve integrated layout, construction, and operation, various structures are usually arranged in the same area. There are multiple parallel tunnels beneath the high fill field of the airport, with a thickness ranging from several meters to tens of meters. Pile foundation structures are used at the bottom of the tunnel to enhance vertical stiffness and ensure that the tunnel structure does not undergo settlement and deformation. After the pile foundation penetrates the hard rock bearing layer, the settlement is generally less than 10mm. If the geological conditions of the foundation are poor (such as in coastal areas), vertical sloping collapse will occur in the transition area between the tunnel section structure and the fill, seriously affecting the driving function above the airport. Reasonable reinforcement measures must be taken to strengthen the weak foundation to ensure that the surface does not produce large uneven settlement. The main factors causing uneven surface settlement are foundation compression deformation and settlement deformation of high fill body itself. It is generally believed that surface deformation is mainly controlled by foundation compression deformation. The fill body is a layered compacted soil body with relatively small deformation. However, in the high fill state, the deformation of the fill body itself cannot be ignored. According to experience, the compression deformation of the high fill body itself can reach 0.5%-1.5% of the filling height. For example, the compression deformation corresponding to a filling height of 20m can reach 10cm-30cm.

[0003] Traditional foundation treatment measures use CFG piles, crushed stone piles, and plain concrete piles to strengthen foundation rigidity and prevent significant foundation settlement after fill compaction. High fill construction primarily relies on increasing compaction and reinforcing the ground. Due to the influence of multiple parallel tunnels, foundation rigidity varies significantly. In areas with strict settlement controls, such as airport flight zones, fill deformation must be controlled to prevent compliance with regulatory settlement control requirements. Traditional fill settlement control measures are extremely difficult to control for uneven settlement. Summary of the Invention

[0004] The purpose of the present invention is to overcome the technical problem that the existing technology is difficult to control the uneven settlement of the high fill tunnel foundation structure, which may easily lead to surface collapse, and to provide a high fill tunnel foundation structure and design method for controlling uneven settlement.

[0005] In a first aspect, the present invention provides a high-fill tunnel foundation structure for controlling uneven settlement, comprising a bedrock layer, a soft stratum and an artificial fill layer arranged in sequence from bottom to top, a tunnel being provided in the artificial fill layer, and a pile foundation structure being provided at the bottom of the tunnel; the projection area of ​​the tunnel in the artificial fill layer in the vertical direction is a first area, a first buffer layer is horizontally provided in the first area above the tunnel, and the first buffer layer can cover the first area; the artificial fill layers adjacent to both sides of the first area are second areas, and a second buffer layer is horizontally provided in the second area; the compression deformation of the first buffer layer is greater than the compression deformation of the second buffer layer, and the total compression deformation of the first area is equal to the total compression deformation of the second area.

[0006] The present application divides the artificial fill layer into a first area where the tunnel is located and a second area where no tunnel is set in the horizontal direction. Since the settlement in the first area is less than the settlement in the second area, a first buffer layer and a second buffer layer can be horizontally set in the first area and the second area respectively, wherein the first buffer layer is set above the tunnel. The elastic modulus or thickness parameters of the first buffer layer and the second buffer layer can be determined by the corresponding design calculation method, and the compression deformation of the first buffer layer and the second buffer layer in the fill can be determined, so that the elastic modulus and compression deformation of the first buffer layer are greater than the elastic modulus and compression deformation of the second buffer layer, thereby The difference between the original settlement of the first area and the settlement of the second area can be offset. That is to say, by setting a first buffer layer with a larger elastic modulus or thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, a second buffer layer with a smaller elastic modulus or thickness is set in the second area with a larger settlement, which can reduce the settlement in the second area. By reducing the elastic modulus and the thickness, the settlement in the first area and the second area (i.e., the total compression deformation) can be guaranteed to be the same, thereby ensuring that the upper road surface of the foundation structure always remains in the horizontal plane, and effectively avoiding the occurrence of uneven settlement and vertical step-type collapse accidents.

[0007] Preferably, a plurality of the tunnels are arranged side by side and at intervals in the horizontal direction in the artificial fill layer, and the distance between two adjacent tunnels is less than 5m, and the scope of the first area includes the projection area of ​​the tunnel in the vertical direction and the area between two adjacent tunnels.

[0008] When multiple tunnels are set up in the artificial fill layer and the distance between two adjacent tunnels is less than 5m, the settlement of the area between the two adjacent tunnels is almost the same as the settlement of the first area. Therefore, the tunnels can be regarded as connected tunnels or single-line tunnels with a tunnel width that is a multiple of the corresponding width of an ordinary single-line tunnel. The range of the first area can be extended from the range where a single tunnel is located to the range between two adjacent tunnels. Therefore, the first buffer layer can cover the top of multiple tunnels at the same time to increase the settlement in the first area, and the second buffer layer can be set as usual in the second area on both sides of the multiple tunnels to reduce the settlement in the second area, so that the settlement of the first area remains the same as the settlement of the second area.

[0009] Preferably, several tunnels are arranged side by side and at intervals in the horizontal direction in the artificial fill layer, and the spacing between two adjacent tunnels is 5m to 30m. The area in the artificial fill layer between two adjacent tunnels is the third area. A third buffer layer is horizontally arranged in the third area, and the third buffer layer can cover the third area. The compression deformation of the third buffer layer is greater than the compression deformation of the second buffer layer and less than the compression deformation of the first buffer layer; the total compression deformation of the third area is equal to the total compression deformation of the first area and the total compression deformation of the second area.

[0010] When multiple tunnels are set up in the artificial fill layer and the distance between two adjacent tunnels is between 5m and 30m, the range between the two adjacent tunnels can be used as the third area. When no buffer layer is set, the settlement in the third area is greater than the settlement in the first area and less than the settlement in the second area. Therefore, a third buffer layer is set in the third area, and through design calculation, the compression deformation of the third buffer layer is greater than the compression deformation of the second buffer layer and less than the compression deformation of the first buffer layer. Finally, the settlement of the third area can be kept the same as the settlement of the first area and the settlement of the second area.

[0011] Preferably, several tunnels are arranged side by side and at intervals in the horizontal direction in the artificial fill layer, and the distance between two adjacent tunnels is greater than 30m. The scope of the second area includes the area between the two adjacent tunnels, and the second buffer layer can cover the area between the two adjacent tunnels.

[0012] When the number of tunnels in the artificial fill layer is one, or when there are multiple tunnels and the distance between two adjacent tunnels is greater than 30m, it can be regarded as a single-line tunnel situation. At this time, the scope of the second area may include the areas on both sides of the tunnel in the case of a single tunnel, that is, the areas adjacent to both sides of the first area, and may also include the areas on both sides of multiple tunnels in the case of multiple tunnels, as well as the area between two adjacent tunnels. At this time, the second buffer layer may cover the area between the two adjacent tunnels, and the second buffer layer may also be located in the second areas on both sides of the tunnel, so that the settlement of the second area remains the same as the settlement of the first area.

[0013] Preferably, the bottom of the pile foundation structure is located in the bedrock layer, and the first buffer layer and the second buffer layer are both EPS plastic foam boards.

[0014] In a second aspect, the present invention provides a design method for a high fill tunnel foundation structure for controlling uneven settlement, the design method comprising: calculating the compression deformation Δ of the first region according to the following formula: 11 :

[0015]

[0016] Where:

[0017] △ 11 —compression deformation of the filler body and the first buffer layer in the first region;

[0018] E sp1 - elastic modulus of the first buffer layer;

[0019] h p1 - thickness of the first buffer layer;

[0020] γ—the density of the fill in the first area;

[0021] h—the burial depth of the tunnel;

[0022] E s1 - Compression modulus of the fill within the first region.

[0023] Preferably, the method further comprises: if no foundation treatment is performed outside the tunnel, calculating the shear deformation Δ of the fill in the first area according to the following formula: 12 :

[0024]

[0025] Where:

[0026] - the internal friction angle of the fill in the first region;

[0027] ν—Poisson’s ratio of the fill volume within the first region;

[0028] Then the total compressive deformation Δ1 of the filler body in the first region and the first buffer layer is:

[0029] Δ1=Δ 11 +Δ 12 .

[0030] Preferably, the method further comprises: when the number of the tunnel is one or the distance between two adjacent tunnels among the plurality of tunnels is greater than 30 m, calculating the compressive deformation Δ2 of the second region by the following formula:

[0031]

[0032] Where:

[0033] △2—total compression deformation of the second region;

[0034] E sp2 - elastic modulus of the second buffer layer;

[0035] h p2 - thickness of the second buffer layer;

[0036] E s2 - compression modulus of the fill within the second region;

[0037] H—the height of the artificial fill layer.

[0038] Preferably, the method further comprises: when the distance between two adjacent tunnels among the plurality of tunnels is less than 5 m, the compressive deformation amount Δ2 of the second area is calculated according to the calculation formula of the compressive deformation amount Δ1 of the first area.

[0039] Preferably, the method further comprises: when the distance a between two adjacent tunnels among the plurality of tunnels is 5m to 30m, the calculation formula of the compressive deformation amount Δ3 of the third region is:

[0040]

[0041] Where:

[0042] Δ3—total compression deformation of the third region;

[0043] E sp3 —elastic modulus of the third buffer layer;

[0044] h p3 —Thickness of the third buffer layer;

[0045] E s3- compression modulus of the fill within the third region;

[0046] H—the height of the artificial fill layer;

[0047] Among them, the elastic modulus E of the third buffer layer is sp3 The calculation formula is:

[0048]

[0049] The design method of the present application can be based on the same effect of settlement (compression deformation) achieved in each area (first area, second area and third area), and utilizes the calculation relationship between compression deformation and various parameters (elastic modulus, thickness, fill height, tunnel depth, etc. of the buffer layer) to reversely calculate the elastic modulus and thickness parameters of the buffer layer used to achieve the same effect of settlement in each location. The corresponding elastic modulus parameter values ​​of the buffer layer at different locations can be calculated on the basis of the consistent thickness of the buffer layer at each location, and the corresponding thickness values ​​of the buffer layer at different locations can also be calculated on the basis of the consistent elastic modulus of the buffer layer at each location. The parameters can be calculated in two ways by controlling variables to ensure that the total settlement of each area remains the same.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention provides a high fill tunnel foundation structure and design method for controlling uneven settlement. The structure can be divided horizontally into a first area where the tunnel is located and a second area where no tunnel is located. Since the settlement in the first area is less than the settlement in the second area, a first buffer layer and a second buffer layer can be horizontally arranged in the first area and the second area respectively. The first buffer layer is arranged above the tunnel. The elastic modulus or thickness parameters of the first buffer layer and the second buffer layer can be determined by a corresponding design calculation method, and the compression deformation of the first buffer layer and the second buffer layer in the fill can be determined, so that the elastic modulus and compression deformation of the first buffer layer are equal. The elastic modulus and compression deformation of the second buffer layer are greater than those of the first buffer layer, thereby offsetting the difference between the original settlement in the first area and the settlement in the second area. That is to say, by arranging a first buffer layer with a larger elastic modulus or a larger thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, by arranging a second buffer layer with a smaller elastic modulus or a smaller thickness in the second area with a larger settlement, the settlement in the second area can be reduced. By reducing the elastic modulus and the total compression deformation, it is possible to ensure that the settlement in the first area and the second area (i.e., the total compression deformation) is the same, thereby ensuring that the upper road surface of the foundation structure is always maintained in the horizontal plane, and effectively avoiding uneven settlement. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the foundation structure of the existing double-track tunnels arranged in parallel.

[0053] Figure 2 Schematic diagram of the surface settlement deformation curve of the existing double-track tunnels arranged in parallel.

[0054] Figure 3 This is a schematic diagram of the first structure of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (tunnel spacing is less than 5m).

[0055] Figure 4 for Figure 3 Schematic diagram of the surface settlement deformation curve of the structure shown.

[0056] Figure 5 This is a schematic diagram of the second structure of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (the tunnel spacing is greater than 5m and less than 30m).

[0057] Figure 6 for Figure 5 Schematic diagram of the surface settlement deformation curve of the structure shown.

[0058] Figure 7 This is a schematic diagram of the third structure of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (the tunnel spacing is greater than 30m).

[0059] Figure 8 for Figure 7 Schematic diagram of the surface settlement deformation curve of the structure shown.

[0060] Markings in the figure:

[0061] 1. Bedrock layer, 2. Soft stratum, 3. Artificial fill layer, 31. First area, 32. Second area, 33. Third area, 4. Tunnel, 5. Pile foundation structure, 6. First buffer layer, 7. Second buffer layer, 8. Third buffer layer, 9. Artificial fill site, 10. Reinforcement piles. DETAILED DESCRIPTION

[0062] The present invention will be further described in detail below with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0063] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or positional relationship, such as "upper", "lower", "left", "right", "center", "inside", and "outside", are based on the expressions of the orientation or positional relationship shown in the accompanying drawings, or are the orientation or positional relationship in which the invented product / device / apparatus is placed when it is conventionally used. These terms of orientation or positional relationship are merely for the purpose of facilitating the description of the scheme of the present invention or simplifying the description of the specific embodiments to facilitate the rapid understanding of the scheme by technicians, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship, and therefore should not be understood as limiting the present invention.

[0064] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simply understood that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", and "parallel", and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the solution of the present invention.

[0065] In addition, the expressions “first”, “second”, “third”, etc. in the terms are merely used to distinguish the description of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0066] In addition, in the description of the embodiments of the present invention, "several," "plurality," and "a number" represent at least two. It can also be any number such as two, three, four, five, six, seven, eight, nine, or even more than nine.

[0067] Furthermore, in the description of the technical solution of the present invention, unless otherwise expressly specified, defined, or limited, the terms "disposed," "installed," "connected," "connected," "provided with," "laid," and "arranged" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections. They may be welded, riveted, bolted, threaded, or other commonly used connection methods in the art. Such connections may be mechanical, electrical, or communicative; they may be direct, indirect via an intermediate medium, or internally connected between two components.

[0068] Example 1

[0069] This embodiment provides a high fill tunnel foundation structure for controlling uneven settlement.

[0070] Figure 1 This is a schematic diagram of the foundation structure of the existing double-track tunnels arranged in parallel; Figure 2 A schematic diagram of the surface settlement deformation curve for an existing double-track tunnel arranged in parallel; Figure 3 This is a schematic diagram of the first structural type of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (tunnel spacing is less than 5m); Figure 4 for Figure 3 Schematic diagram of the surface settlement deformation curve of the structure shown; Figure 5 This is a schematic diagram of the second structure of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (the tunnel spacing is greater than 5m and less than 30m); Figure 6 for Figure 5 Schematic diagram of the surface settlement deformation curve of the structure shown; Figure 7 This is a schematic diagram of the third structure of the high fill tunnel foundation structure for controlling uneven settlement of the present invention (tunnel spacing is greater than 30m); Figure 8 for Figure 7 Schematic diagram of the surface settlement deformation curve of the structure shown.

[0071] like Figures 1 to 2 As shown in the figure, the existing tunnel 4 foundation structure has reinforced piles 10 installed in the soft stratum 2 areas on both sides of the pile foundation structure 5 below the tunnel 4 to strengthen the foundation rigidity. The reinforced piles 10 can generally be CFG piles, crushed stone piles, plain concrete piles, etc., which can ensure that there is no significant foundation settlement after the fill is compacted. The main means of controlling the high fill are to improve the compaction degree and add reinforcement. Due to the influence of multiple parallel tunnels 4, the foundation is large and the rigidity of different parts of the foundation varies greatly. Above the artificial fill layer 3 is the artificial fill field 9. Usually in areas with strict settlement control such as airport flight zones, the deformation of the fill must be controlled, otherwise it will not meet the settlement control requirements of the standard. For the settlement control of high fill, even if the foundation is compacted with reinforced piles 10, it is still difficult to avoid uneven settlement.

[0072] like Figures 3 to 8As shown in , the foundation structure of the high fill tunnel 4 for controlling uneven settlement described in this embodiment may include a bedrock layer 1, a soft stratum 2 and an artificial fill layer 3 arranged in sequence from bottom to top, a tunnel 4 is provided in the artificial fill layer 3, and a pile foundation structure 5 is provided at the bottom of the tunnel 4; the projection area of ​​the tunnel 4 in the artificial fill layer 3 in the vertical direction is a first area 31, and a first buffer layer 6 is horizontally provided in the first area 31 above the tunnel 4, and the first buffer layer 6 can cover the first area 31; the artificial fill layers 3 adjacent to both sides of the first area 31 are second areas 32, and a second buffer layer 7 is horizontally provided in the second area 32; the compression deformation of the first buffer layer 6 is greater than the compression deformation of the second buffer layer 7, and the total compression deformation of the first area 31 is equal to the total compression deformation of the second area 32. Here, the tunnel 4 is buried in the artificial fill layer 3. Usually, the bottom of the tunnel 4 is driven into the stratum below the artificial fill layer 3 through the pile foundation structure 5 to support the tunnel 4. Therefore, the settlement of the first area 31 where the tunnel 4 is located is small, while the settlement of the second area 32 without the tunnel 4 is large due to the effect of the weak stratum 2 below.

[0073] Here, the artificial fill layer 3 can be divided horizontally into a first area 31 where the tunnel 4 is located and a second area 32 where the tunnel 4 is not located. Since the settlement in the first area 31 is less than the settlement in the second area 32, a first buffer layer 6 and a second buffer layer 7 can be horizontally arranged in the first area 31 and the second area 32, respectively. The first buffer layer 6 is arranged above the tunnel 4. The elastic modulus or thickness parameters of the first buffer layer 6 and the second buffer layer 7 can be determined by a corresponding design calculation method, and the compression deformation of the first buffer layer 6 and the second buffer layer 7 in the fill can be determined, so that the elastic modulus and compression deformation of the first buffer layer 6 are greater than the elastic modulus and compression deformation of the second buffer layer 7. The difference between the settlement of the original first area 31 and the settlement of the second area 32 can be offset. That is to say, by arranging a first buffer layer 6 with a larger elastic modulus or thickness in the first area 31 with smaller settlement, the settlement in the first area 31 can be increased. In addition, by arranging a second buffer layer 7 with a smaller elastic modulus or thickness in the second area 32 with larger settlement, the settlement in the second area 32 can be reduced. By these two methods, the settlement (i.e., the total compression deformation) in the first area 31 and the second area 32 can be kept the same, thereby ensuring that the upper road surface of the foundation structure is always maintained in the horizontal plane, and effectively avoiding the occurrence of uneven settlement and vertical step-type collapse accidents.

[0074] In this embodiment, if Figure 3 and Figure 4As shown in , several tunnels 4 are arranged side by side and at intervals in the horizontal direction in the artificial fill layer 3, and the spacing between two adjacent tunnels 4 is less than 5m. The range of the first area 31 may include the projection area of ​​the tunnel 4 in the vertical direction and the area between the two adjacent tunnels 4; when multiple tunnels 4 are set in the artificial fill layer 3, and the spacing between two adjacent tunnels 4 is less than 5m, the settlement of the area between the two adjacent tunnels 4 is almost the same as the settlement of the first area 31. Therefore, each tunnel 4 can be regarded as a connected tunnel 4 or a single-line tunnel 4 whose tunnel 4 width is a corresponding multiple of an ordinary single-line tunnel 4. The range of the first area 31 can extend from the range where a single tunnel 4 is located to the range between two adjacent tunnels 4. Therefore, the first buffer layer 6 can cover the top of multiple tunnels 4 at the same time to increase the settlement in the first area 31, and the second buffer layer 7 can be set as usual in the second area 32 on both sides of the multiple tunnels 4 to reduce the settlement in the second area 32, so that the settlement of the first area 31 remains the same as the settlement of the second area 32.

[0075] In this embodiment, if Figure 5 and Figure 6 As shown in the figure, several tunnels 4 are arranged side by side and at intervals in the horizontal direction in the artificial fill layer 3, and the spacing between two adjacent tunnels 4 is 5m to 30m. The area in the artificial fill layer 3 between two adjacent tunnels 4 is the third area 33. A third buffer layer 8 is horizontally arranged in the third area 33, and the third buffer layer 8 can cover the third area 33. The compression deformation of the third buffer layer 8 is greater than the compression deformation of the second buffer layer 7 and less than the compression deformation of the first buffer layer 6; the total compression deformation of the third area 33 is equal to the total compression deformation of the first area 31 and the total compression deformation of the second area 32. When multiple tunnels 4 are set in the artificial fill layer 3 and the distance between two adjacent tunnels 4 is between 5m and 30m, the range between the two adjacent tunnels 4 can be used as the third area 33. When no buffer layer is set, the settlement in the third area 33 is greater than the settlement in the first area 31 and less than the settlement in the second area 32. Therefore, a third buffer layer 8 is set in the third area 33, and through design calculation, the compression deformation of the third buffer layer 8 is greater than the compression deformation of the second buffer layer 7 and less than the compression deformation of the first buffer layer 6. Finally, the settlement of the third area 33 can be kept the same as the settlement of the first area 31 and the settlement of the second area 32.

[0076] In this embodiment, if Figure 7 and Figure 8As shown in , a plurality of tunnels 4 are arranged horizontally side by side and at intervals in the artificial fill layer 3, and the spacing between two adjacent tunnels 4 is greater than 30m. The scope of the second area 32 includes the area between two adjacent tunnels 4, and the second buffer layer 7 can cover the area between the two adjacent tunnels 4. When the number of tunnels 4 in the artificial fill layer 3 is one, or when there are multiple tunnels 4 and the spacing between two adjacent tunnels 4 is greater than 30m, both can be regarded as the case of a single-line tunnel 4. In this case, the scope of the second area 32 can include the areas on both sides of the tunnel 4 in the case of a single tunnel 4, that is, the areas immediately adjacent to both sides of the first area 31, or can include the areas on both sides of multiple tunnels 4 in the case of multiple tunnels 4, as well as the area between two adjacent tunnels 4. In this case, the second buffer layer 7 can cover the area between the two adjacent tunnels 4. At the same time, the second buffer layer 7 can also be located in the second areas 32 on both sides of the tunnels 4, so that the settlement of the second areas 32 remains the same as that of the first area 31.

[0077] Optionally, the bottom of the pile foundation structure 5 can be located in the bedrock layer 1, and the first buffer layer 6 and the second buffer layer 7 are both EPS plastic foam boards. Here, the bottom of the pile foundation structure 5 can be driven into the bedrock layer 1, stably supporting the tunnel 4 and maintaining a small amount of settlement in the first area 31. The first buffer layer 6, the second buffer layer 7, and the third buffer layer 8 can all be made of EPS plastic foam. Of course, in addition to this, the first buffer layer 6, the second buffer layer 7, and the third buffer layer 8 can also be made of other types of compressible elastic materials, such as HDPE (high-density polyethylene), PP (polypropylene), and other polymer materials, which are not specifically limited in the present invention.

[0078] Optionally, the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 can be connected to each other to form an integral structure, such as an integrally formed connection, or they can be arranged in abutment with each other without adopting a fixed connection. In addition, the setting depths of the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 can be the same or different. For example, the first buffer layer 6 can be set in the area above the tunnel 4, and the second buffer layer 7 and the third buffer layer 8 can be set at any depth in the second area 32 and the third area 33, respectively. Accordingly, the parameter values ​​of the elastic modulus or thickness of the buffer layer calculated using different depth parameters will also be different. The present invention does not specifically limit the burying parameters of the buffer layer.

[0079] In addition, the number of layers of material plates used for the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8, respectively, and the vertical elevation positions at which they are laid can also be selected arbitrarily. For example, if the elastic modulus is determined, the thickness of the first buffer layer 6 is calculated to be 80 cm, and the thickness of the standard plate is 20 cm. Then, four layers of plates can be stacked to form a first buffer layer 6 with a total thickness of 80 cm to meet the use requirements, or customized 80 cm thick plates can be directly used, and only one layer is needed as the first buffer layer 6 to meet the use requirements; the present invention does not limit the specific number of layers of the buffer layer.

[0080] Example 2

[0081] This embodiment provides a design method for a high fill tunnel foundation structure.

[0082] The design method of the high fill tunnel foundation structure described in this embodiment can be used to design the high fill tunnel foundation structure for controlling uneven settlement as described in Example 1.

[0083] The design method of the high fill tunnel foundation structure described in this embodiment may include the following steps:

[0084] S1: Calculate the compression deformation Δ of the first region 31 according to the following formula 11 :

[0085]

[0086] Where:

[0087] △ 11 - the compressive deformation of the fillet in the first region 31 and the first buffer layer 6;

[0088] E sp1 - elastic modulus of the first buffer layer 6;

[0089] h p1 - thickness of the first buffer layer 6;

[0090] γ—the density of the fill in the first region 31;

[0091] h—the burial depth of tunnel 4;

[0092] E s1 - Compression modulus of the fill in the first region 31 .

[0093] S2: If no foundation treatment is performed outside the tunnel 4, the shear deformation Δ of the fill in the first region 31 is calculated as follows: 12 :

[0094]

[0095] Where:

[0096] - internal friction angle of the fill in the first region 31;

[0097] ν—Poisson’s ratio of the fill volume in the first region 31;

[0098] The total compressive deformation Δ1 of the filler body in the first region 31 and the first buffer layer 6 is:

[0099] Δ1=Δ 11 +Δ 12 .

[0100] S3: When the number of tunnels 4 is one or the distance between two adjacent tunnels 4 among the plurality of tunnels 4 is greater than 30 m, the compressive deformation Δ2 of the second region 32 is calculated as follows:

[0101]

[0102] Where:

[0103] △2—total compression deformation of the second region 32;

[0104] E sp2 - elastic modulus of the second buffer layer 7;

[0105] h p2 - thickness of the second buffer layer 7;

[0106] E s2 - compression modulus of the fill in the second region 32;

[0107] H—height of artificial fill layer 3.

[0108] S4: When the distance between two adjacent tunnels 4 among the plurality of tunnels 4 is less than 5 m, the compression deformation Δ2 of the second region 32 is calculated according to the calculation formula of the compression deformation Δ1 of the first region 31, that is, the calculation steps of S1 and S2 are repeated.

[0109] S5: When the distance a between two adjacent tunnels 4 in the plurality of tunnels 4 is 5 m to 30 m, the calculation formula for the compressive deformation Δ3 of the third region 33 is:

[0110]

[0111] Where:

[0112] Δ3—total compression deformation of the third region 33;

[0113] E sp3 - elastic modulus of the third buffer layer 8;

[0114] h p3- thickness of the third buffer layer 8;

[0115] E s3 - compression modulus of the fill in the third region 33;

[0116] H—height of artificial fill layer 3;

[0117] Among them, the elastic modulus E of the third buffer layer 8 is sp3 The calculation formula is:

[0118]

[0119] S6: Compare Δ1, Δ2, and Δ3 calculated above. Δ1=Δ2=Δ3 should be achieved. Then, reversely calculate the elastic modulus or thickness parameter of the corresponding buffer layer.

[0120] The thicknesses of the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 can be set separately or the same, as shown in the following formula:

[0121] h p1 =h p2 =h p ;

[0122] When the shear deformation of the soil is not considered, the parameters of the buffer material are derived to satisfy the following relationship:

[0123]

[0124] When considering the shear deformation of the soil, the parameters of the buffer material satisfy the following relationship:

[0125]

[0126] In the case of connected tunnels (i.e., the distance between tunnels 4 is less than 5m), assuming that the outer contour widths of tunnel 4 are L1 and L2, the total width of the connected tunnel is L1+L2. At this time, the first buffer layer 6 is laid above the tunnel 4 according to the size of L1+L2.

[0127] When considering the mutual influence of double-line tunnels (i.e. the distance between tunnels 4 is greater than 5m and less than 30m), the modulus of the third buffer layer 8 is calculated as that of the single-line tunnel and then linearly interpolated. The modulus of the third buffer layer 8 is E sp3 and thickness h p3 The modulus range of the first buffer layer 6 and the second buffer layer 7 can be [E sp1 , E sp2 ] is obtained by linear interpolation, that is, the interval a of tunnel 4 is linearly interpolated between [5m, 30m], which can be calculated as follows:

[0128]

[0129] It should be noted that the settlement of the second area 32 and the third area 33 can be calculated by selecting any step from S3 to S5 according to the actual spacing of the tunnel 4, while the compression deformation Δ 11 and the shear deformation Δ of the fillet in the first region 31 12 The calculation order of (i.e., S1 and S2) is not limited, and the calculation order of the settlement amounts of the first area 31, the second area 32, and the third area 33 is also not limited.

[0130] The design method of the present application can be based on the same effect of settlement (compression deformation) achieved in each area (first area 31, second area 32 and third area 33), and utilizes the calculation relationship between compression deformation and various parameters (elastic modulus, thickness, fill height, tunnel depth, etc. of the buffer layer) to reversely calculate the elastic modulus and thickness parameters of the buffer layer used to achieve the same effect of settlement in each location. The corresponding elastic modulus parameter values ​​of the buffer layer at different positions can be calculated on the basis of the consistent thickness of the buffer layer at each location, and the corresponding thickness values ​​of the buffer layer at different positions can also be calculated on the basis of the consistent elastic modulus of the buffer layer at each location. The parameters can be calculated in two ways by controlling variables to ensure that the total settlement of each area remains the same.

[0131] The following is an example of the calculation process using a specific parameter:

[0132] The design parameters are: burial depth h = 4.3m, H = 14.3m, tunnel 4 spacing a = 15m, filler compaction degree 0.9, satisfying the following formula

[0133]

[0134] Ignoring shear deformation, assuming h p Take 50cm, the elastic modulus of EPS materials on the market currently ranges from 0.1MPa to 12MPa, E sp1 Take 0.5MPa, the filler elastic modulus E corresponding to the compaction degree 0.9 s =25MPa.

[0135] E can be obtained sp2 =3.7MPa.

[0136] The distance a between the tunnels 4 is 15 m. Considering the mutual influence between the tunnels 4, the compression modulus of the third buffer layer 8 is (0.5+3.7) / 2=2.1 MPa.

[0137] Considering shear deformation, assuming h p Take 80cm, the elastic modulus of EPS materials on the market currently ranges from 0.1MPa to 12MPa, E sp1Take 1.0MPa and compaction degree 0.9, and the corresponding filler elastic modulus Es = 25MPa.

[0138]

[0139] E can be obtained sp2 =3.2MPa.

[0140] The distance a between the tunnels 4 is 15 m. Considering the mutual influence between the tunnels 4, the compression modulus of the third buffer layer 8 is (1.0+3.2) / 2=2.1 MPa.

[0141] The above example is only for a specific parameter. When other parameters are selected, the calculation formula and calculation steps used will be adjusted according to actual conditions, and the present invention does not make specific limitations on this.

[0142] It should be noted that the critical values ​​of the spacing between the above-mentioned tunnels 4: 5m and 30m, are only the critical values ​​selected for tunnels of standard size and structure. If the tunnel sizes are different or significantly different, the critical value of the tunnel spacing will also change. The present invention does not limit the specific numerical value of the critical value of the tunnel spacing.

[0143] for Figure 2 、 Figure 4 、 Figure 6 and Figure 8 In the graphs shown, the horizontal axis in each graph represents the horizontal distance of the surface (unit: m), and the vertical axis represents the surface settlement distance (unit: cm), wherein, Figure 2 The K value in represents the degree of compaction or compaction coefficient; Figure 4 When the clear distance is 5m, the mutual influence between the tunnels is relatively large, and there is no differential settlement between the tunnels, that is, the settlement between the tunnels is consistent with the settlement inside the tunnels, and the two tunnels form an integral structure. As the burial depth increases to 30m, there is still a large differential settlement in the surface deformation, and the two tunnel structures can be considered as connected single-track tunnels.

[0144] Figure 6 When the clear distance increases to 15m, the mutual influence of the tunnels weakens, a settlement trough is formed between the two tunnels, and the tunnel spacing has a significant impact on the settlement between tunnels.

[0145] Figure 8 When the clear distance increases to 30m, there is almost no mutual influence between the tunnels. The settlement between the two tunnels is equivalent to the settlement formed by the pure fill section, and the influence of differential settlement can be ignored.

[0146] In summary, the present invention provides a high fill tunnel foundation structure and design method for controlling uneven settlement. The artificial fill layer can be divided horizontally into a first area where the tunnel is located and a second area where no tunnel is located. Since the settlement in the first area is less than the settlement in the second area, a first buffer layer and a second buffer layer can be horizontally arranged in the first area and the second area, respectively. The first buffer layer is arranged above the tunnel. The elastic modulus or thickness parameters of the first buffer layer and the second buffer layer can be determined by a corresponding design calculation method, and the compression deformation of the first buffer layer and the second buffer layer in the fill can be determined, so that the elastic modulus and compression deformation of the first buffer layer are greater than those of the second buffer layer. The deformation is greater than the elastic modulus and compression deformation of the second buffer layer, and thus can offset the difference between the original settlement of the first area and the settlement of the second area. That is to say, by setting a first buffer layer with a larger elastic modulus or thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, setting a second buffer layer with a smaller elastic modulus or thickness in the second area with a larger settlement can reduce the settlement in the second area. By reducing and increasing the elastic modulus and the compressive deformation, it can be ensured that the settlement in the first area and the second area (i.e., the total compression deformation) is the same, thereby ensuring that the upper road surface of the foundation structure always remains in the horizontal plane, and effectively avoiding uneven settlement.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high fill tunnel (4) foundation structure for controlling uneven settlement, characterized in that: The invention comprises a bedrock layer (1), a weak stratum (2) and an artificial filling layer (3) arranged in sequence from bottom to top, a tunnel (4) being provided in the artificial filling layer (3), and a pile foundation structure (5) being provided at the bottom of the tunnel (4); The projection area of ​​the tunnel (4) in the artificial filling layer (3) in the vertical direction is a first area (31); a first buffer layer (6) is horizontally provided in the first area (31) above the tunnel (4); the first buffer layer (6) is capable of covering the first area (31); the artificial filling layers (3) adjacent to both sides of the first area (31) are second areas (32); a second buffer layer (7) is horizontally provided in the second area (32); The compressive deformation of the first buffer layer (6) is greater than the compressive deformation of the second buffer layer (7), and the total compressive deformation of the first region (31) is equal to the total compressive deformation of the second region (32).

2. The high fill tunnel (4) foundation structure for controlling uneven settlement according to claim 1 is characterized in that: A plurality of tunnels (4) are arranged side by side and spaced apart in the horizontal direction in the artificial filling layer (3), and the spacing between two adjacent tunnels (4) is less than 5m. The range of the first area (31) includes the projection area of ​​the tunnel (4) in the vertical direction and the area between two adjacent tunnels (4).

3. The high fill tunnel (4) foundation structure for controlling uneven settlement according to claim 1 is characterized in that: A plurality of tunnels (4) are arranged side by side and at intervals in the horizontal direction in the artificial filling layer (3), and the spacing between two adjacent tunnels (4) is 5m to 30m. The area in the artificial filling layer (3) between two adjacent tunnels (4) is a third area (33). A third buffer layer (8) is horizontally arranged in the third area (33). The third buffer layer (8) can cover the third area (33). The compression deformation of the third buffer layer (8) is greater than the compression deformation of the second buffer layer (7) and less than the compression deformation of the first buffer layer (6); the total compression deformation of the third area (33) is equal to the total compression deformation of the first area (31) and the total compression deformation of the second area (32).

4. The high fill tunnel (4) foundation structure for controlling uneven settlement according to claim 1 is characterized in that: A plurality of tunnels (4) are arranged side by side and spaced apart in a horizontal direction in the artificial filling layer (3), and the spacing between two adjacent tunnels (4) is greater than 30 m. The range of the second area (32) includes the area between the two adjacent tunnels (4), and the second buffer layer (7) can cover the area between the two adjacent tunnels (4).

5. The high fill tunnel (4) foundation structure for controlling uneven settlement according to any one of claims 1 to 4, characterized in that: The bottom of the pile foundation structure (5) is located in the bedrock layer (1), and the first buffer layer (6) and the second buffer layer (7) are both EPS plastic foam boards.

6. A design method for a high fill tunnel foundation structure, characterized in that: For designing a high fill tunnel foundation structure for controlling uneven settlement according to any one of claims 1 to 5, the design method comprises: The compression deformation Δ of the first region (31) is calculated as follows: 11 : Where: △ 11 - the compressive deformation of the filler body in the first region (31) and the first buffer layer (6); E sp1 - elastic modulus of the first buffer layer (6); h p1 - the thickness of the first buffer layer (6); γ—the density of the fill in the first region (31); h—the burial depth of the tunnel (4); E s1 - Compression modulus of the fill in the first region (31).

7. The design method of high fill tunnel foundation structure according to claim 6, characterized in that: Also includes: If no foundation treatment is performed outside the tunnel (4), the shear deformation Δ of the fill in the first region (31) is calculated as follows: 12 : Where: - the internal friction angle of the fill in the first region (31); ν—Poisson’s ratio of the fill volume in the first region (31); Then the total compression deformation Δ1 of the filler body in the first region (31) and the first buffer layer (6) is: Δ1=Δ 11 +D 12 。 8. The design method of high fill tunnel foundation structure according to claim 7, characterized in that: Also includes: When the number of the tunnel (4) is one or the distance between two adjacent tunnels (4) among the plurality of tunnels (4) is greater than 30 m, the compression deformation Δ2 of the second region (32) is calculated as follows: Where: △2—total compression deformation of the second region (32); E sp2 - elastic modulus of the second buffer layer (7); h p2 - the thickness of the second buffer layer (7); E s2 - compression modulus of the fill in the second region (32); H—the height of the artificial filling layer (3).

9. The design method of high fill tunnel foundation structure according to claim 8, characterized in that: Also includes: When the distance between two adjacent tunnels (4) in the plurality of tunnels (4) is less than 5 m, the compressive deformation Δ2 of the second region (32) is calculated using the calculation formula for the compressive deformation Δ1 of the first region (31).

10. The design method of high fill tunnel foundation structure according to claim 9, characterized in that: Also includes: When the distance a between two adjacent tunnels (4) in the plurality of tunnels (4) is 5m to 30m, the calculation formula for the compression deformation Δ3 of the third region (33) is: Where: Δ3—total compression deformation of the third region (33); E sp3 - elastic modulus of the third buffer layer (8); h p3 - thickness of the third buffer layer (8); E s3 - compression modulus of the fill in the third region (33); H—the height of the artificial filling layer (3); Among them, the elastic modulus E of the third buffer layer (8) sp3 The calculation formula is:

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