Structural form and rigidity design method for differential settlement control of high-fill tunnel engineering

Abstract

The invention relates to the technical field of tunnel engineering, in particular to a high-fill tunnel foundation structure for controlling differential settlement and a design method.The tunnel foundation structure comprises a bedrock layer, a soft stratum and an artificial fill layer which are sequentially arranged from bottom to top, a tunnel is arranged in the artificial fill layer, and a pile foundation structure is arranged at the bottom of the tunnel; the projection area of the tunnel in the artificial filling layer in the vertical direction is a first area, a first buffer layer is arranged in the first area above the tunnel, and the first buffer layer covers the first area; the artificial filling layers on the two sides of the first area are second areas, and second buffer layers are arranged in the second areas; the compressive deformation of the first buffer layer is larger than that of the second buffer layer, and the total compressive deformation of the first area is equal to that of the second area. The elasticity modulus or thickness of the first and second buffer layers can be determined through a design calculation method, the upper pavement of the foundation is kept horizontal, and differential settlement of the ground surface is effectively avoided.

Description

Technical Field

[0001] The 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] There are many functional requirements for airport engineering in my country, with subways, high-speed railways, and expressways crisscrossing each other. In order to meet the requirements of various functions and realize integrated layout, construction, and operation, various structures are usually arranged in the same area. There are multiple parallel tunnels under the high fill field of the airport, with a thickness of several meters to tens of meters. The pile foundation structure is used at the bottom of the tunnel to enhance the vertical stiffness to ensure that the tunnel structure does not undergo settlement and deformation. The settlement of the pile foundation after penetrating into the hard rock bearing layer is generally less than 10mm. If the geological conditions of the foundation are poor (such as coastal areas), the surface of the transition area between the tunnel section structure and the fill will produce vertical sill-like collapse, which will seriously affect the driving function above the airport. Reasonable reinforcement measures must be taken to strengthen the soft foundation to ensure that the surface does not produce large uneven settlement. The main factors causing uneven surface settlement are compression deformation of the foundation and settlement deformation of the high fill body itself. It is generally believed that surface deformation is mainly controlled by compression deformation of the foundation. 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, plain concrete piles, etc. to strengthen the foundation stiffness and ensure that there is no large foundation settlement after the fill is compacted. The main means of high fill are to improve the compaction degree and reinforce the fill. Due to the influence of multiple parallel tunnels, the foundation stiffness varies greatly. In areas with strict settlement control such as airport flight areas, the deformation of the fill must be controlled, otherwise it will not meet the settlement control requirements of the specification. It is extremely difficult to control the uneven settlement of the fill using traditional treatment measures. Summary of the invention

[0004] The purpose of the present invention is to overcome the technical problem that it is difficult to control uneven settlement of high fill tunnel foundation structure in the prior art, 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 arranged in the artificial fill layer, and a pile foundation structure being arranged 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 arranged 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 arranged 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 filling layer into a first area where the tunnel is located and a second area where the tunnel is not set in the horizontal direction. Since the settlement in the first area is less than the settlement in the second area, the first buffer layer and the 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 a corresponding design calculation method, and the compression deformation of the first buffer layer and the second buffer layer in the filling can be determined, so that the elastic modulus and the compression deformation of the first buffer layer are greater than the elastic modulus and the 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 a larger thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, by setting 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. This balance can ensure that the settlement (i.e., the total compression deformation) in the first area and the second area is 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 spacing 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-track tunnels whose tunnel width is a multiple of the corresponding multiple of the ordinary single-track tunnel. The range of the first area can extend 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, a plurality of the tunnels are arranged side by side and at intervals in the horizontal direction in the artificial fill layer, and the interval between two adjacent tunnels is 5m to 30m, the area in the artificial fill layer between two adjacent tunnels is the third area, and a third buffer layer is horizontally arranged in the third area, 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 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 regarded 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, 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 greater than 30 m, the scope of the second area includes the area between two adjacent tunnels, and the second buffer layer can cover the area between two adjacent tunnels.

[0012] When the number of tunnels in the artificial fill layer is 1, 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. 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 area 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, which is used to design the high fill tunnel foundation structure for controlling uneven settlement as described above, the design method comprising: calculating the compression deformation amount Δ of the first area according to the following formula 11 :

[0015]

[0016] Where:

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

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

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

[0020] γ—weight of the fill body in the first region;

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

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

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

[0024]

[0025] Where:

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

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

[0028] Then the total compression deformation Δ1 of the fill 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 tunnels is 1 or the distance between two adjacent tunnels among the plurality of tunnels is greater than 30 m, calculating the compression deformation Δ2 of the second region according to 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 - the 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 compression deformation amount Δ3 of the third area is:

[0040]

[0041] Where:

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

[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 in the third region;

[0046] H—the height of the artificial filling 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 (the first area, the second area and the third area), and utilizes the calculation relationship between the compression deformation and each parameter (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 that can 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 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 the 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 into a first area where the tunnel is located and a second area where the tunnel is not located in the horizontal direction by dividing the artificial fill layer. 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, wherein 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 The amount is greater than the elastic modulus and compression deformation of the second buffer layer, thereby offsetting the difference in 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 a larger thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, by setting 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. The balance between the two can ensure that the settlement (i.e. the total compression deformation) in the first area and the second area 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 (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. Reinforced piles. DETAILED DESCRIPTION

[0062] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to 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 position relationship such as "up", "down", "left", "right", "center", "inside", "outside", etc. are all expressions based on the orientation or position relationship shown in the drawings, or are the orientation or position relationship when the invented product / equipment / device is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the present invention or simplifying the description in the specific embodiments, so as to facilitate the technicians to quickly understand the scheme, 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 position relationship, and therefore cannot be understood as a limitation on 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 simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., 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 scheme of the present invention.

[0065] In addition, the expressions “first”, “second”, “third”, etc., which appear 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 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0067] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0068] Example 1

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

[0070] Figure 1 A schematic diagram of the foundation structure of the existing double-track tunnels arranged in parallel; Figure 2 It is a schematic diagram of the ground settlement deformation curve of the existing double-track tunnels arranged in parallel; 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); Figure 4 for Figure 3 Schematic diagram of ground settlement deformation curve of the structure shown; Figure 5 A schematic diagram of a second structure of a high fill tunnel foundation structure for controlling uneven settlement of the present invention (tunnel spacing is greater than 5m and less than 30m); Figure 6 for Figure 5 Schematic diagram of ground settlement deformation curve of the structure shown; Figure 7 A third structural schematic diagram 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 Figure 1 to Figure 2 As shown in , the existing tunnel 4 foundation structure sets reinforcement piles 10 in the soft stratum 2 area on both sides of the pile foundation structure 5 below the tunnel 4 to strengthen the foundation rigidity. The reinforcement piles 10 can usually be CFG piles, crushed stone piles, plain concrete piles, etc., which can ensure that there is no large foundation settlement after the fill is compacted. The main means of high fill body are to improve the compaction degree, reinforce the reinforcement, etc. Due to the influence of multiple parallel tunnels 4, the foundation range is large, and the rigidity of each part of the foundation varies greatly. The artificial fill layer 3 is above the artificial fill field 9. Usually, in areas with strict settlement control such as airport flight areas, the deformation of the fill body must be controlled, otherwise it cannot meet the standard settlement control requirements. For the settlement control of the high fill body, even if the foundation is compacted with reinforcement piles 10, it is still difficult to avoid the occurrence of 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 arranged in the artificial fill layer 3, and a pile foundation structure 5 is arranged at the bottom of the tunnel 4; the projection area of ​​the tunnel 4 in the artificial fill layer 3 along the vertical direction is the first area 31, and a first buffer layer 6 is horizontally arranged 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 the second area 32, and a second buffer layer 7 is horizontally arranged 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 a 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 soft stratum 2 below.

[0073] Here, the artificial filling layer 3 can be divided into a first area 31 where the tunnel 4 is located and a second area 32 where the tunnel 4 is not set in the horizontal direction. 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 set in the first area 31 and the second area 32 respectively, wherein the first buffer layer 6 is set 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 filling can be determined, so that the elastic modulus and the compression deformation of the first buffer layer 6 are greater than the elastic modulus and the compression deformation of the second buffer layer 7. The difference between the original settlement of the first area 31 and the settlement of the second area 32 can be offset. That is to say, by setting a first buffer layer 6 with a larger elastic modulus or a larger thickness in the first area 31 with a smaller settlement, the settlement in the first area 31 can be increased. In addition, by setting a second buffer layer 7 with a smaller elastic modulus or a smaller thickness in the second area 32 with a larger settlement, the settlement in the second area 32 can be reduced. The balance between the two can ensure that the settlement (i.e., the total compression deformation) in the first area 31 and the second area 32 are 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 , 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 less than 5m, and the range of the first area 31 may include the projection area of ​​the tunnel 4 in the vertical direction and the area between two adjacent tunnels 4; when a plurality of tunnels 4 are arranged in the artificial filling layer 3, and the spacing between two adjacent tunnels 4 is less than 5m, the settlement of the area between two adjacent tunnels 4 is almost the same as the settlement of the first area 31, so each tunnel 4 can be regarded as a connected tunnel 4 or a single-line tunnel 4 whose width is a corresponding multiple of an ordinary single-line tunnel 4, and 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, so the first buffer layer 6 can cover the top of the plurality of tunnels 4 at the same time to increase the settlement in the first area 31, and the second buffer layer 7 can be arranged in the second area 32 on both sides of the plurality of tunnels 4 as usual 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, a number 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 the 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. 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 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 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 two adjacent tunnels 4. When the number of tunnels 4 in the artificial filling layer 3 is 1, or when there are multiple tunnels 4 and the spacing between two adjacent tunnels 4 is greater than 30m, it can be regarded as a single-line tunnel 4. At this time, 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 adjacent to both sides of the first area 31, and can also 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. At this time, the second buffer layer 7 can cover the area between two adjacent tunnels 4, and the second buffer layer 7 can also be located in the second area 32 on both sides of the tunnel 4, so that the settlement of the second area 32 remains the same as the settlement 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, and the tunnel 4 can be stably supported, so that the first area 31 maintains a small amount of settlement; the materials of the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 can all be EPS plastic foam. Of course, in addition to this, the materials of the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 can also be other types of compressible elastic materials, for example, HDPE (high-density polyethylene), PP (polypropylene) and other high molecular 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 interconnected to form an integral structure, such as an integrally formed connection, or they may not be fixedly connected but simply be arranged in abutment with each other. In addition, the setting depths of the first buffer layer 6, the second buffer layer 7 and the third buffer layer 8 may 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 amount Δ of the first region 31 according to the following formula 11 :

[0085]

[0086] Where:

[0087] △ 11 - compression deformation of the filler body and the first buffer layer 6 in the first region 31;

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

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

[0090] γ—weight of the fill body 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 body in the first region 31 is calculated as follows: 12 :

[0094]

[0095] Where:

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

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

[0098] Then the total compression 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 1 or the distance between two adjacent tunnels 4 among the plurality of tunnels 4 is greater than 30 m, the compressive deformation amount 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 - the 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 compression deformation amount 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- the 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 filling 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 the Δ1, Δ2 and Δ3 calculated above, and make sure that Δ1=Δ2=Δ3, and 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 can be set equal, 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 tunnels 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 the mutual influence of double-line tunnels is considered (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 according to the single-line tunnel and then linearly interpolated. The modulus E of the third buffer layer 8 is 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 spacing 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, and the compression deformation of the first area 31 Δ 11 and the shear deformation Δ of the fill body in the first region 31 12 The calculation order of (ie, S1 and S2) is not limited, and at the same time, 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 (the first area 31, the second area 32 and the third area 33), and utilizes the calculation relationship between the compression deformation and each parameter (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 that can achieve the same effect of settlement in each location. The corresponding elastic modulus parameter values ​​of the buffer layers at different locations can be calculated on the basis of the consistent thickness of the buffer layers at various locations, and the corresponding thickness values ​​of the buffer layers at different locations can be calculated on the basis of the consistent elastic modulus of the buffer layers at various locations. The parameters can be calculated in two ways by controlling the variables to ensure that the total settlement of each area remains the same.

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

[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, compaction degree 0.9 corresponding to the filler elastic modulus E s =25MPa.

[0135] E 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 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 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 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 The graphs shown in the figure, 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), where: 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-line 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, and the settlement formed between the two tunnels is equivalent to the settlement formed by the pure fill section, so the influence of differential settlement can be ignored.

[0146] In summary, the high fill tunnel foundation structure and design method for controlling uneven settlement of the present invention can be achieved by dividing the artificial fill layer into a first area where the tunnel is located and a second area where the tunnel is not located 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 arranged in the first area and the second area respectively, wherein the first buffer layer is arranged above the tunnel, and 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 the elastic modulus and compression deformation of the second buffer layer in the fill. The deformation is greater than the elastic modulus and compressive deformation of the second buffer layer, thereby offsetting 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 a larger thickness in the first area with a smaller settlement, the settlement in the first area can be increased. In addition, by setting 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. This balance can ensure that the settlement in the first area and the second area (i.e., the total compressive deformation) is the same, thereby ensuring that the upper road surface of the foundation structure always remains in a 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 protection scope of the present invention.

Claims

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

2. The high fill tunnel (4) foundation structure for controlling uneven settlement according to claim 1, 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 distance between two adjacent tunnels (4) is less than 5 m. 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, 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, 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 distance between two adjacent tunnels (4) is greater than 30 m. The range of the second area (32) includes the area between two adjacent tunnels (4), and the second buffer layer (7) can cover the area between 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 as claimed in 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 amount of compression 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 body in the first region (31); h—the burial depth of the tunnel (4); E s1 - Compression modulus of the fill in said first region (31).

7. The design method of high fill tunnel foundation structure according to claim 6 is characterized in that: Also includes: If no foundation treatment is performed outside the tunnel (4), the shear deformation Δ of the fill body in the first area (31) is calculated as follows: 12 : Where: - the internal friction angle of the fill body 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 is 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 amount Δ2 of the second region (32) is calculated according to the following formula: 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 the high fill tunnel foundation structure according to claim 8, characterized in that: Also includes: When the distance between two adjacent tunnels (4) among the plurality of tunnels (4) is less than 5 m, the compressive deformation amount Δ2 of the second area (32) is calculated according to the calculation formula of the compressive deformation amount Δ1 of the first area (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) among the plurality of tunnels (4) is 5 m to 30 m, the calculation formula for the compression deformation amount 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 - the 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); The elastic modulus E of the third buffer layer (8) is sp3 The calculation formula is:

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