A construction method for a group of overlapping tunnels with small spacing, structure and structure

Abstract

The present invention relates to a three-dimensional tunnel group, in particular to a three-dimensional tunnel group structure with small spacing, a structure and a construction method thereof, wherein the three-dimensional tunnel group structure with small spacing includes a first tunnel, a second tunnel and a backfill area, the backfill area is located on one side of the second tunnel, and the backfill area is filled with a first backfill structure and a second backfill structure from top to bottom in sequence, and a plurality of support piles for supporting the first tunnel are vertically arranged in the first backfill structure, and the upper end of the support pile abuts against the first tunnel. The second backfill structure is a structural member filled with a material having a strength greater than or equal to that of C15 concrete. The three-dimensional tunnel group structure with small spacing of the present application solves the problem that the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling, thereby reducing the overall construction cost of the three-dimensional tunnel group.

Description

Technical Field

[0001] The present invention relates to a three-dimensional tunnel group, in particular to a small-spacing three-dimensional tunnel group structure, construction and its construction method. Background Art

[0002] During the construction of existing airports, an airport, especially a regional hub airport, is no longer a traditional single passenger distribution center concept, but an airport economic zone formed by the aggregation and fission of people flow, logistics, capital flow, and information flow, thus giving rise to a high-end, mutually influential, and mutually beneficial economic form circle. In this case, channels such as subways, roads, commuting channels, cargo transportation, and landscape viewing pick-up and drop-off leading to the airport converge at the entrance of the airport. However, due to limited location space, the tunnel group at this location cannot be horizontally expanded in sequence and can only be designed as a vertically stacked space structure (such as a "pin" - shaped or "lv" - shaped tunnel group), which greatly increases the construction difficulty.

[0003] Meanwhile, due to the construction period, it is not possible to repair one tunnel and complete the backfilling operation before starting to repair the next tunnel. Usually, multiple tunnels are constructed simultaneously. At this time, due to location and cost limitations, the backfilling area on the side of the lower tunnel cannot be compacted, seriously affecting the settlement of the upper backfilling area and other tunnels, resulting in some tunnels being unusable due to excessive settlement, which has a huge impact on the entire construction.

[0004] As Figure 1 shown, the backfilling area 3 located below the first tunnel 1 is on one side of the second tunnel 2. The first tunnel 1 is obliquely above the second tunnel 2. The backfilling area 3 is surrounded by the first tunnel 1, the second tunnel 2, the bottom surface 6 of the foundation, and the foundation slope 4 below the first tunnel 1, presenting an inverted trapezoidal shape. The clear distance in the horizontal direction of the backfilling area 3 is the smallest at the bottom surface 6 of the foundation and increases as it rises. At this time, the horizontal net width of some areas at the bottom of the backfilling area 3 is generally less than 2.5 m, and the backfilling machinery cannot enter, so the filler in some areas at the bottom of the backfilling area 3 cannot be compacted. If compacted manually, the volume is too large, the cost is too high, and the efficiency is low.

[0005] Meanwhile, the tunnel group is close to the runway. Using ordinary backfilling materials such as backfill soil or cement soil cannot fully ensure that the backfilling area meets the settlement standard through compaction. Moreover, due to the synchronous construction and sequential alternating construction of adjacent tunnels in segments, the backfilling area 3 below the first tunnel 1 is compacted in segments along the length direction of the first tunnel 1, and its compaction effect is relatively poor compared with the overall compaction construction, presenting a large settlement hidden danger.

[0006] However, if the backfilling area 3 is integrally filled with a material with a relatively high setting strength such as concrete, the cost is too high. Summary of the Invention

[0007] The purpose of the present invention is to provide a small-spacing three-dimensional tunnel group structure, construction and construction method, which solves the problem that the filling material in the bottom part of the backfill area cannot be compacted in the prior art; the tunnel group is located near the runway, and the general backfill materials cannot fully ensure that the backfill area reaches the settlement standard through compaction; if materials with high solidification strength such as concrete are used for overall filling, the cost is too high. By using different backfill materials for layered backfilling, the problem that the filling material in the bottom part of the backfill area cannot be compacted while ensuring that the entire backfill area meets the settlement standard is solved. At the same time, the cost of the filling material in the backfill area is reduced by using support piles, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A small-spacing three-dimensional tunnel group structure comprises a first tunnel, a second tunnel and a backfill area located below the first tunnel, wherein the backfill area is located on one side of the second tunnel, and the backfill area is filled with a first backfill structure and a second backfill structure in sequence from top to bottom, wherein a plurality of support piles for supporting the first tunnel are vertically arranged in the first backfill structure, and the upper ends of the support piles are in contact with the first tunnel, and the second backfill structure is a structural member filled with a material having a strength greater than or equal to that of C15 concrete.

[0010] The present application describes a small-spacing three-dimensional tunnel group structure, in which the backfill area is surrounded by the first tunnel, the second tunnel, the foundation base surface and the foundation slope below the first tunnel, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area is the smallest at the foundation base surface, and the higher it goes, the larger the horizontal clearance distance.

[0011] The three-dimensional tunnel group structure described in this application is based on whether the filling material in the backfill gap between the foundation slope and the second tunnel can be compacted according to the settlement standard:

[0012] In the area below the interface, compaction machinery cannot enter the area for compaction, and other methods cannot compact the filler according to the settlement standard. In this case, the material with a strength greater than or equal to that of C15 concrete is backfilled in the area to form a second backfill structure. The material's own characteristics are used to achieve the required support strength and settlement requirements for the area, thereby greatly reducing the impact of the settlement of the area where the second backfill structure is located on the settlement of the backfill area and structure above it;

[0013] The area above the interface is accessible to compacting machinery, which can be used to backfill the area with commonly used backfill materials (cement soil, or backfill materials with equal or stronger strength) to carry out filling operations, and then the first backfill structure is compacted to eventually form the first backfill structure that meets the settlement standards. Furthermore, a number of support piles for supporting the first tunnel are vertically arranged in the first backfill structure to support part or all of the deadweight of the upper end of the backfill area, thereby reducing the weight that the first backfill structure needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure, and further reducing the cost of the filler in the first backfill structure while ensuring the settlement requirements. Furthermore, the cost of the added support piles is far less than the cost saved by reducing the filler in the first backfill structure.

[0014] To summarize, the small-spacing three-dimensional tunnel group structure described in the present application solves the problem that part of the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0015] Preferably, the minimum width of the first backfill structure is greater than or equal to 2.5 m.

[0016] The minimum width of the first backfill structure is the minimum width of the first backfill structure in the horizontal direction.

[0017] 2.5m is the minimum width of the working surface that compaction machinery can compact under existing conditions.

[0018] Preferably, the second backfill structure is a structural member filled with C15 concrete.

[0019] The strength of C15 concrete material can meet the strength requirements of the second backfill structure formed by it.

[0020] Preferably, the second backfill structure is a structural member filled with C20 concrete, C25 concrete or C30 concrete.

[0021] The strength of the C20 concrete, C25 concrete or C30 concrete is greater than that of the C15 concrete. By filling C20 concrete, C25 concrete or C30 concrete to form the second backfill structure, its performance can meet the support strength and settlement requirements required by the area, thereby greatly reducing the impact of settlement of the area where the second backfill structure is located on the settlement of the backfill area and structure above it.

[0022] Preferably, the first backfill structure is a structural member filled with cement soil.

[0023] Preferably, when the first tunnel is a tubular tunnel structure, the supporting piles are end-bearing piles.

[0024] The construction of the end bearing pile is specifically as follows: firstly, a hole is drilled at the target location as required, then a steel cage is arranged in the hole, and then grouting is performed in the hole to form an end bearing pile, which has good performance and can independently support the force applied to the first tunnel by the first tunnel and the objects above the first tunnel (including the deadweight and the dynamic load applied by the dynamic load above it);

[0025] Preferably, when the first tunnel is a U-shaped tunnel structure with an open upper end, the supporting piles are high-pressure jet-jet piles, and the high-pressure jet-jet piles and the first backfill structure jointly support the first tunnel.

[0026] The construction of high-pressure rotary jet piles is specifically as follows: first drill small holes at the target location as required, then perform high-pressure grouting toward the holes, spray cement slurry into the soil layer and mix it with the soil to form a continuous overlapping cement reinforcement body. Its performance is weaker than that of the end-bearing piles, so it needs to be subjected to force together with the first backfill structure to meet the settlement requirements.

[0027] In actual construction, when the first tunnel is a tubular tunnel structure, the backfill area needs to withstand a large force (including the weight of the tunnel, the weight of the backfill and structures above the tunnel, and the dynamic load in and above the tunnel), and the supporting piles are end-bearing piles to avoid increasing the cost of backfill materials in the first backfill structure, which has the best effect; when the first tunnel is a U-shaped tunnel structure with an open upper end, the supporting piles are high-pressure rotary jet piles, and the backfill area needs to withstand a small force (including only the weight of the tunnel, and the dynamic load in the tunnel). Without increasing the cost of backfill materials in the first backfill structure, high-pressure rotary jet piles are used. The high-pressure rotary jet piles and the first backfill structure are jointly subjected to force, which can also meet its settlement requirements.

[0028] The present application also discloses a small-pitch overlapping tunnel group structure, comprising a first tunnel, a second tunnel and a backfill area located below the first tunnel, the backfill area being located on one side of the second tunnel, and a first backfill structure and a second backfill structure being arranged horizontally in sequence in the backfill area, wherein:

[0029] A plurality of support piles for supporting the first tunnel are vertically arranged in the first backfill structure, and the upper ends of the support piles are in contact with the first tunnel;

[0030] The second backfill structure is abutted against the second tunnel at a side away from the first backfill structure, and the upper end of the second backfill structure is abutted against the first tunnel. The second backfill structure is a structural member filled with a material having a strength greater than or equal to that of C15 concrete;

[0031] A retaining wall assembly is used to prevent deformation and instability of the foundation slope. The retaining wall assembly is arranged at the contact point between the first backfill structure and the second backfill structure. The top of the retaining wall assembly has an extension portion extending laterally toward the foundation slope, and the extension portion is used to fit the foundation slope.

[0032] The backfill area is surrounded by the first tunnel, the second tunnel, the foundation surface and the foundation slope below the first tunnel, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area is the smallest at the foundation surface, and the higher it goes, the larger the horizontal clearance distance becomes.

[0033] During the actual construction process, deformation and instability of the foundation slope may sometimes occur. In this case, a retaining wall assembly needs to be set at the root of the foundation slope to prevent the deformation and instability of the foundation slope. However, since the root of the foundation slope is very close to the second tunnel, the retaining wall assembly will occupy the position of the support pile closest to the second tunnel, making it impossible to construct the support pile.

[0034] In response to the above problems, a small-spacing overlapping tunnel group structure described in the present application, during construction, the retaining wall assembly is first constructed in accordance with relevant standard requirements, specifically: the base of the retaining wall assembly is first constructed, and after the base of the retaining wall assembly is constructed, the base, the foundation slope and the plane where the top surface of the base is located form a triangular area, at this time, horizontal construction is carried out from the top of the base toward the foundation slope, extending all the way to the foundation slope, thereby filling the triangular area and forming the extension portion.

[0035] Furthermore, the provision of the extension allows the width of the top surface of the retaining wall assembly to be compacted mechanically, while the extension structure is directly backfilled with concrete, or filled with backfill materials and compacted manually.

[0036] Taking the retaining wall assembly as the boundary, a material having a strength greater than or equal to that of C15 concrete is filled in the backfill area between the retaining wall assembly and the second tunnel, and the material is filled upward until it abuts against the first tunnel to form the second backfill structure, so that the second backfill structure can bear a part of the weight of the first tunnel, that is, the second backfill structure is used to replace the support piles that cannot be installed there. In this process, the second backfill structure component not only solves the problem of mutual interference between the retaining wall assembly and the support piles, but also uses a material having a strength greater than or equal to that of C15 concrete for backfilling, and achieves the required support strength and settlement requirements of the area through the characteristics of the material itself. In addition, the hardness of the retaining wall assembly is specified in the standard specification, so that the second backfill structure and the retaining wall assembly jointly solve the problem that the filling material at the bottom of the backfill area cannot be compacted, thereby greatly reducing the influence of the settlement of the area where the second backfill structure is located on the settlement of the backfill area and the structure above it;

[0037] The area located on the side of the retaining wall assembly away from the second tunnel has its bottom as the top of the extension part, and compacting machinery can enter this area, that is, backfill the area with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to carry out filling operations, and then compact the first backfill structure to finally form the first backfill structure that meets the settlement standard. Moreover, a number of support piles for supporting the first tunnel are vertically arranged in the first backfill structure to support a part of the deadweight of the upper end of the backfill area, thereby reducing the weight that the first backfill structure needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure, and then on the basis of ensuring the settlement requirements, reducing the cost of the filler in the first backfill structure, and the cost of the added support piles is much less than the reduced cost of the filler in the first backfill structure, while reducing the settlement risk of the segmented compaction method.

[0038] To summarize, the small-spacing overlapping tunnel group structure described in the present application, when a retaining wall assembly is provided, extends the second backfill structure upward to abut against the support of the first tunnel, thereby replacing the supporting piles there, so as to avoid interference between the retaining wall assembly and the supporting piles. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that part of the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0039] Preferably, the top surface width of the retaining wall assembly is greater than or equal to 2.5 m.

[0040] 2.5m is the minimum width of the working surface that compaction machinery can compact under existing conditions.

[0041] Preferably, the second backfill structure is a structural member filled with C15 concrete.

[0042] The strength of C15 concrete material can meet the strength requirements of the second backfill structure formed by it.

[0043] Preferably, the second backfill structure is a structural member filled with C20 concrete, C25 concrete or C30 concrete.

[0044] The strength of the C20 concrete, C25 concrete or C30 concrete is greater than that of the C15 concrete. By filling C20 concrete, C25 concrete or C30 concrete to form the second backfill structure, its performance can meet the support strength and settlement requirements required by the area, thereby greatly reducing the impact of settlement of the area where the second backfill structure is located on the settlement of the backfill area and structure above it.

[0045] Preferably, the first backfill structure is a structural member filled with cement soil.

[0046] Preferably, when the first tunnel is a tubular tunnel structure, the supporting piles are end-bearing piles.

[0047] The construction of the end bearing pile is specifically as follows: firstly, a hole is drilled at the target location as required, then a steel cage is arranged in the hole, and then grouting is performed in the hole to form an end bearing pile, which has good performance and can independently support the force applied to the first tunnel by the first tunnel and the objects above the first tunnel (including the deadweight and the dynamic load applied by the dynamic load above it);

[0048] Preferably, when the first tunnel is a U-shaped tunnel structure with an open upper end, the supporting piles are high-pressure jet-jet piles, and the high-pressure jet-jet piles and the first backfill structure jointly support the first tunnel.

[0049] The construction of high-pressure rotary jet piles is specifically as follows: first drill small holes at the target location as required, then perform high-pressure grouting toward the holes, spray cement slurry into the soil layer and mix it with the soil to form a continuous overlapping cement reinforcement body. Its performance is weaker than that of the end-bearing piles, so it needs to be subjected to force together with the first backfill structure to meet the settlement requirements.

[0050] In actual construction, when the first tunnel is a tubular tunnel structure, the backfill area needs to withstand a large force (including the weight of the tunnel, the weight of the backfill and structures above the tunnel, and the dynamic load in and above the tunnel), and the supporting piles are end-bearing piles to avoid increasing the cost of backfill materials in the first backfill structure, which has the best effect; when the first tunnel is a U-shaped tunnel structure with an open upper end, the supporting piles are high-pressure rotary jet piles, and the backfill area needs to withstand a small force (including only the weight of the tunnel, and the dynamic load in the tunnel). Without increasing the cost of backfill materials in the first backfill structure, high-pressure rotary jet piles are used. The high-pressure rotary jet piles and the first backfill structure are jointly subjected to force, which can also meet its settlement requirements.

[0051] Preferably, a stop device for preventing the first tunnel from approaching the second tunnel is provided on the side of the first tunnel close to the second tunnel, and the lower end of the stop device is connected to the second backfill structure.

[0052] The stop device is used to prevent the displacement of the first tunnel closer to the second tunnel from exceeding the allowable value during use, thereby preventing a major safety hazard. The lower end of the stop device is connected to the second backfill structure, so that the second backfill structure and the stop device together form an L-shaped structure, which has a better effect of preventing the first tunnel from approaching the second tunnel.

[0053] The present application also discloses a construction method using the small-spacing three-dimensional tunnel group structure described in the present application, comprising the following steps:

[0054] A1. Construction of the second tunnel;

[0055] A2. Filling the backfill area with a filler having a strength greater than or equal to the strength of C15 concrete to form the second backfill structure;

[0056] A3. Fill the remaining space in the backfill area with a filler and compact it to form the first backfill structure;

[0057] A4. Carry out support pile construction on the first backfill structure;

[0058] A5. Construct the first tunnel.

[0059] The application describes a construction method using a small-spacing three-dimensional tunnel group structure, in which the backfill area is surrounded by the first tunnel, the second tunnel, the foundation base surface and the foundation slope below the first tunnel, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area is the smallest at the foundation base surface, and the higher it goes, the larger the horizontal clearance distance becomes. During the construction process, its range is determined by the theoretical design plan.

[0060] During construction, after the foundation is dug, the second tunnel at the bottom is constructed first. When the second tunnel is constructed, a backfill area with an inverted trapezoidal shape and an open top is formed on one side. At this time, the second backfill structure is constructed.

[0061] The construction method described in this application is based on whether the backfill gap between the foundation slope and the second tunnel can allow compaction machinery to enter:

[0062] The area below the interface is inaccessible to compaction machinery. In this case, the area is backfilled with a material whose strength is greater than or equal to that of C15 concrete to form a second backfill structure. The material's own characteristics are used to achieve the required support strength and settlement requirements for the area, thereby greatly reducing the impact of the settlement of the area where the second backfill structure is located on the settlement of the backfill area and structure above it.

[0063] After the construction of the second backfill structure is completed, the compacting machinery can operate on the top surface of the second backfill structure (32), that is, the area above the second backfill structure (32) can be backfilled with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to perform filling operations, and then the first backfill structure is compacted to finally form the first backfill structure that meets the settlement standard. In addition, a number of support piles for supporting the first tunnel are vertically arranged in the first backfill structure to support a part of the deadweight of the upper end of the backfill area, thereby reducing the weight that the first backfill structure needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure, and then on the basis of ensuring the settlement requirements, reducing the cost of the filler in the first backfill structure, and the cost of the added support piles is far less than the cost saved by reducing the filler in the first backfill structure.

[0064] Afterwards, the first backfill structure is used as the basic support to carry out the construction of the corresponding section of the first tunnel and finally complete the construction.

[0065] To sum up, the construction method of a three-dimensional tunnel group structure with a small spacing described in the present application solves the problem that part of the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0066] Preferably, after the construction of the second backfill structure is completed, the width of the top surface thereof is greater than or equal to 2.5 m, so that compaction machinery can operate on the top surface of the second backfill structure.

[0067] The present application also discloses a construction method using the small-spacing overlapping tunnel group structure described in the present application, comprising the following steps:

[0068] S1. Construction of the second tunnel;

[0069] S2. Setting the retaining wall assembly at the root of the foundation slope below the first tunnel;

[0070] S3. Fill the backfill area between the retaining wall assembly and the second tunnel with a filler having a strength greater than or equal to that of C15 concrete to form the second backfill structure, and make the top of the second backfill structure abut against and support the first tunnel;

[0071] S4. Filling the remaining space in the backfill area with a filler and compacting it to form the first backfill structure;

[0072] S5. Carry out support pile construction on the first backfill structure;

[0073] S6. Construct the first tunnel.

[0074] The application describes a construction method that uses a group of overlapping tunnels with small spacing. The backfill area is surrounded by the first tunnel, the second tunnel, the base surface of the foundation and the foundation slope below the first tunnel, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area is the smallest at the base surface of the foundation. The higher it goes, the larger the horizontal clearance distance becomes. During the construction process, its range is determined by the theoretical design plan.

[0075] In the actual construction process, in order to address the possible deformation and instability of the foundation slope, the second tunnel is constructed, and a retaining wall assembly is set at the root of the foundation slope to prevent the deformation and instability of the foundation slope. However, since the root of the foundation slope is very close to the second tunnel, the retaining wall assembly will occupy the position of the support pile closest to the second tunnel, making it impossible to construct the support pile.

[0076] During construction, the retaining wall assembly is first constructed in accordance with the requirements of relevant standards, which is specifically: the base of the retaining wall assembly is first constructed. After the base of the retaining wall assembly is constructed, the base, the foundation slope and the plane where the top surface of the base is located form a triangular area. At this time, horizontal construction is carried out from the top of the base toward the foundation slope, extending all the way to the foundation slope, thereby filling the triangular area and forming the extension portion.

[0077] Furthermore, due to the provision of the extension part, the top surface width of the retaining wall assembly (5) can be compacted mechanically, while the extension part structure is directly backfilled with concrete, or filled with backfill materials and compacted manually.

[0078] In the above scheme, the retaining wall assembly construction can also be carried out before the construction of the second tunnel in this section.

[0079] After the retaining wall assembly is completed, a material having a strength greater than or equal to that of C15 concrete is filled in the backfill area between the retaining wall assembly and the second tunnel with the retaining wall assembly as the boundary, and the material is filled upward until it abuts against the first tunnel to form the second backfill structure, so that the second backfill structure can bear a part of the weight of the first tunnel, that is, the second backfill structure is used to replace the support piles that cannot be installed there. In this process, the second backfill structure component not only solves the problem of mutual interference between the retaining wall assembly and the support piles, but also uses a material having a strength greater than or equal to that of C15 concrete for backfilling, and achieves the required support strength and settlement requirements of the area through the characteristics of the material itself. In addition, the hardness of the retaining wall assembly as specified in the standard specification, so that the second backfill structure and the retaining wall assembly jointly solve the problem that the filling material at the bottom of the backfill area cannot be compacted, thereby greatly reducing the influence of the settlement of the area where the second backfill structure is located on the settlement of the backfill area and the structure above it;

[0080] After the construction of the second backfill structure is completed, in the area located on the side of the retaining wall assembly away from the second tunnel, the bottom of which is the top of the extension part, the compacting machinery can enter this area, and can backfill the area with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to carry out filling operations, and then compact the first backfill structure to finally form the first backfill structure that meets the settlement standards. In addition, a number of support piles for supporting the first tunnel are vertically arranged in the first backfill structure to support a part of the deadweight of the upper end of the backfill area, thereby reducing the weight that the first backfill structure needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure, and then on the basis of ensuring the settlement requirements, reducing the cost of the filler in the first backfill structure, and the cost of the added support piles is much less than the reduced cost of the filler in the first backfill structure, while reducing the settlement risk of the segmented compaction method.

[0081] To summarize, the construction method described in the present application adopts a small-spacing overlapping tunnel group structure. When a retaining wall assembly is provided, the second backfill structure is extended upward to abut against the support of the first tunnel, thereby replacing the supporting piles there, so as to avoid interference between the retaining wall assembly and the supporting piles. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that part of the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0082] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0083] 1. The small-spacing three-dimensional tunnel group structure described in the present application solves the problem that part of the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the support piles are used to reduce the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0084] 2. The present application describes a structure of a group of overlapping tunnels with small spacing. When a retaining wall assembly is provided, the second backfill structure is extended upward to abut against the support of the first tunnel, thereby replacing the supporting piles there, so as to avoid interference between the retaining wall assembly and the supporting piles. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that part of the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0085] 3. The construction method of a three-dimensional tunnel group structure with a small spacing described in the present application solves the problem that part of the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the use of support piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0086] 4. The construction method described in the present application adopts a small-spacing overlapping tunnel group structure. When a retaining wall assembly is provided, the second backfill structure is extended upward to abut against the support of the first tunnel, thereby replacing the supporting piles there, so as to avoid interference between the retaining wall assembly and the supporting piles. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of supporting piles reduces the cost of the filling material in the first backfill structure, thereby reducing the overall construction cost of the three-dimensional tunnel group. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 It is a schematic diagram of the relative position relationship between the first tunnel and the second tunnel in the prior art.

[0088] Figure 2 It is a structural schematic diagram of a small-spacing three-dimensional tunnel group structure of the present invention.

[0089] Figure 3 It is a structural schematic diagram of a small-spacing overlapping tunnel group structure of the present invention.

[0090] Icons: 1-first tunnel; 11-stop device; 2-second tunnel; 3-backfill area; 31-first backfill structure; 32-second backfill structure; 33-support piles; 4-foundation slope; 5-retaining wall assembly; 51-extension; 6-foundation base surface; 7-foundation; 8-upper backfill area. DETAILED DESCRIPTION

[0091] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0092] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0093] Example 1

[0094] like Figure 2 As shown, a small-spacing three-dimensional tunnel group structure described in this embodiment includes a first tunnel 1, a second tunnel 2 and a backfill area 3 located below the first tunnel 1, the backfill area 3 is located on one side of the second tunnel 2, and the backfill area 3 is filled with a first backfill structure 31 and a second backfill structure 32 from top to bottom. A plurality of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31, and the upper ends of the support piles 33 are abutted against the first tunnel 1. The second backfill structure 32 is a structural member filled with a material having a strength greater than or equal to that of C15 concrete.

[0095] The minimum width of the first backfill structure 31 is the minimum width of the first backfill structure 31 in the horizontal direction.

[0096] The minimum width of the first backfill structure is greater than or equal to 2.5 m, and 2.5 m is the minimum width of the working surface on which the backfill machinery can operate under existing conditions.

[0097] On the basis of the above, in a further preferred embodiment, the second backfill structure 32 is a structural member filled with C15 concrete.

[0098] The strength of the C15 concrete material can meet the strength requirement of the second backfill structure 32 formed by the concrete material.

[0099] In the actual construction process, C20 concrete, C25 concrete or C30 concrete can also be used for filling, but compared with C15 concrete, the cost performance is lower.

[0100] like Figure 2 As shown, the foundation 7 is located at the bottom of the foundation pit, and includes a foundation bottom surface 6 and a foundation side slope 4.

[0101] On the basis of the above, in a further preferred embodiment, the first backfill structure 31 is a structure filled with cement soil.

[0102] On the basis of the above, in a further preferred manner, when the first tunnel 1 is a tubular tunnel structure, the support piles 33 are end-bearing piles;

[0103] When the first tunnel 1 is a U-shaped tunnel structure with an open upper end, the supporting piles 33 are high-pressure jet-jet piles, and the high-pressure jet-jet piles and the first backfill structure 31 jointly support the first tunnel 1 .

[0104] The construction of the end bearing pile is specifically as follows: firstly, a hole is drilled at the target position as required, then a steel cage is arranged in the hole, and then grouting is performed in the hole to form an end bearing pile, which has good performance and can independently support the force applied to the first tunnel 1 by the first tunnel 1 and the objects above the first tunnel 1 (including the deadweight and the dynamic load applied by the dynamic load above it);

[0105] The construction of high-pressure rotary jet piles is specifically as follows: first, small holes are drilled at the target location as required, and then high-pressure grouting is performed toward the holes to spray cement slurry into the soil layer and mix with the soil to form a continuous overlapping cement reinforcement body. Its performance is weaker than that of the end-bearing piles, so it needs to be subjected to force together with the first backfill structure 31 to meet the settlement requirements.

[0106] In actual construction, when the first tunnel 1 is a tubular tunnel structure, the backfill area 3 needs to withstand a large force (including the weight of the tunnel, the weight of the backfill and structures above the tunnel, and the dynamic load in and above the tunnel), and the support piles 33 are end-bearing piles to avoid increasing the cost of backfill materials in the first backfill structure 31, which has the best effect; when the first tunnel 1 is a U-shaped tunnel structure with an open upper end, the support piles 33 are high-pressure rotary jet piles, and the backfill area 3 needs to withstand a small force (including only the weight of the tunnel, and the dynamic load in the tunnel). Without increasing the cost of backfill materials in the first backfill structure 31, high-pressure rotary jet piles are used, and the high-pressure rotary jet piles and the first backfill structure 31 are jointly subjected to force, which can also meet its settlement requirements.

[0107] The present application describes a small-spacing three-dimensional tunnel group structure, in which the backfill area 3 is surrounded by the first tunnel 1, the second tunnel 2, the foundation base surface 6 and the foundation slope 4 below the first tunnel 1, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area 3 is the smallest at the foundation base surface 6, and the higher it goes, the larger the horizontal clearance distance.

[0108] The three-dimensional tunnel group structure described in this application is based on whether the filling material in the minimum horizontal gap between the foundation slope 4 and the second tunnel 2 can be compacted according to the settlement standard:

[0109] The area below the interface is not accessible to compaction machinery. In this case, the area is backfilled with a material having a strength greater than or equal to that of C15 concrete to form a second backfill structure 32. The material's own characteristics are used to achieve the required support strength and settlement requirements for the area, thereby greatly reducing the impact of the settlement of the area where the second backfill structure 32 is located on the settlement of the backfill area and structure above it.

[0110] The area above the interface is accessible to compacting machinery, which can be used to backfill the area with commonly used backfill materials (cement soil, or backfill materials with equal or stronger strength) to perform filling operations, and then the first backfill structure 31 is compacted to finally form the first backfill structure 31 that meets the settlement standard. Furthermore, a number of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31 to support part or all of the deadweight of the upper end of the backfill area 3, thereby reducing the weight that the first backfill structure 31 needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure 31, and further reducing the cost of the filler in the first backfill structure 31 while ensuring the settlement requirement. Moreover, the cost of the added support piles 33 is much less than the cost saved by reducing the filler in the first backfill structure 31.

[0111] On the basis of the above, a further preferred method is that in the area above the interface, the minimum horizontal clearance between the foundation slope 4 and the second tunnel 2 is greater than or equal to 2.5m, and the compaction machinery can enter the area.

[0112] To sum up, the small-spacing three-dimensional tunnel group structure described in the present application solves the problem that part of the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the support piles 33 are used to reduce the cost of the filling material in the first backfill structure 31, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0113] Example 2

[0114] like Figure 2 As shown, the construction method of the small-spacing three-dimensional tunnel group structure described in Example 1 described in this embodiment includes the following steps:

[0115] A1. Construction of the second tunnel 2;

[0116] A2. Filling the backfill area 3 with a filler having a strength greater than or equal to that of C15 concrete to form the second backfill structure 32, so that the top surface width of the second backfill structure (32) is greater than or equal to 2.5 m, i.e., at its top surface;

[0117] A3. Filling the remaining space in the backfill area 3 with a filler and compacting it to form the first backfill structure 31;

[0118] A4. Construction of support piles 33 on the first backfill structure 31;

[0119] A5. Construct the first tunnel 1.

[0120] During the construction process, the following two situations usually occur:

[0121] Case 1: After the overall construction of the first tunnel 1 is completed, the second tunnel 2 is constructed. At this time, the construction process in this method is an explanation of the overall construction of the first tunnel 1 or the overall construction of the second tunnel 2;

[0122] Case 2: The first tunnel 1 or the second tunnel 2 is divided into many sections, and construction is carried out in sections. At this time, the construction process in this method is an explanation of the construction of the first tunnel 1 section and the construction of the corresponding section of the second tunnel 2.

[0123] The application describes a construction method using a small-spacing three-dimensional tunnel group structure, in which the backfill area 3 is surrounded by the first tunnel 1, the second tunnel 2, the foundation base surface 6 and the foundation slope 4 below the first tunnel 1, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area 3 is the smallest at the foundation base surface 6, and the higher it goes, the larger the horizontal clearance distance becomes. During the construction process, its range is determined by the theoretical design plan.

[0124] During construction, after the foundation is dug, the second tunnel 2 at the bottom is constructed first. After the second tunnel 2 is constructed, a backfill area 3 with an inverted trapezoid shape and an open top is formed on one side. At this time, the second backfill structure 32 is constructed.

[0125] The construction method described in this application is based on whether the backfill gap between the foundation slope 4 and the second tunnel 2 can allow compaction machinery to enter:

[0126] The area below the interface is not accessible to compaction machinery. In this case, the area is backfilled with a material having a strength greater than or equal to that of C15 concrete to form a second backfill structure 32. The material's own characteristics are used to achieve the required support strength and settlement requirements for the area, thereby greatly reducing the impact of the settlement of the area where the second backfill structure 32 is located on the settlement of the backfill area and structure above it.

[0127] After the construction of the second backfill structure 32 is completed, compaction machinery can enter the area, that is, backfill the area above the second backfill structure (32) with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to perform filling operations, and then compact the first backfill structure 31 to finally form the first backfill structure 31 that meets the settlement standard. In addition, a number of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31 to support a part of the deadweight of the upper end of the backfill area 3, thereby reducing the weight that the first backfill structure 31 needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure 31, and then reducing the cost of the filler in the first backfill structure 31 on the basis of ensuring the settlement requirements. Moreover, the cost of the added support piles 33 is far less than the cost saved by reducing the filler in the first backfill structure 31.

[0128] Afterwards, the first backfill structure 31 is used as a basic support to carry out construction of the corresponding section of the first tunnel 1 and finally complete the construction.

[0129] On the basis of the above, a further preferred method is that after the construction of the second backfill structure 32 is completed, its top surface width is greater than or equal to 2.5m, and compaction machinery can enter the area.

[0130] To sum up, the construction method of a three-dimensional tunnel group structure with a small spacing described in the present application solves the problem that the filling material at the bottom of the backfill area cannot be compacted by using different backfill materials for layered backfilling while ensuring that the entire backfill area meets the settlement standards. At the same time, the support piles 33 are used to reduce the cost of the filling material in the first backfill structure 31, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0131] Example 3

[0132] like Figure 3 As shown, this embodiment discloses a small-pitch three-dimensional tunnel group structure, a small-pitch overlapping tunnel group structure, including a first tunnel 1, a second tunnel 2 and a backfill area 3 located below the first tunnel 1, the backfill area 3 is located on one side of the second tunnel 2, and the backfill area 3 is horizontally arranged with a first backfill structure 31 and a second backfill structure 32 in sequence, wherein:

[0133] A plurality of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31, and the upper ends of the support piles 33 abut against the first tunnel 1;

[0134] The second backfill structure 32 is in contact with the second tunnel 2 at one side away from the first backfill structure 31, and the upper end of the second backfill structure 32 is in contact with the first tunnel 1. The second backfill structure 32 is a structural member filled with a material having a strength greater than or equal to that of C15 concrete.

[0135] The retaining wall assembly 5 is used to prevent the foundation slope from deforming and becoming unstable. The retaining wall assembly 5 is arranged at the contact point between the first backfill structure 31 and the second backfill structure 32. The top of the retaining wall assembly 5 has an extension portion 51 extending laterally toward the foundation slope 4. The extension portion 51 is used to fit with the foundation slope 4. The top surface width of the retaining wall assembly 5 is greater than or equal to 2.5m.

[0136] The backfill area 3 is surrounded by the first tunnel 1, the second tunnel 2, the foundation base surface 6 and the foundation slope 4 below the first tunnel 1, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area 3 is the smallest at the foundation base surface 6, and the higher it goes, the larger the horizontal clearance distance.

[0137] During the actual construction process, the foundation slope 4 may sometimes deform and become unstable. In this case, a retaining wall assembly 5 needs to be set at the root of the foundation slope 4 to prevent the foundation slope from deforming and becoming unstable. However, since the root of the foundation slope 4 is very close to the second tunnel 2 (generally less than 2.5m), the retaining wall assembly 5 will occupy the position of the support pile 33 closest to the second tunnel 2, making it impossible to construct the support pile 33.

[0138] In response to the above-mentioned problems, a small-spacing overlapping tunnel group structure described in the present application, during construction, the retaining wall assembly 5 is first constructed in accordance with relevant standard requirements, specifically: the base of the retaining wall assembly 5 is first constructed. After the base of the retaining wall assembly 5 is constructed, the base, the foundation slope 4 and the plane where the top surface of the base is located form a triangular area. At this time, horizontal construction is performed from the top of the base toward the foundation slope 4, extending all the way to the foundation slope 4, thereby filling the triangular area and forming the extension portion 51.

[0139] Moreover, the setting of the extension part 51 makes it possible for the top surface width of the retaining wall assembly to be compacted mechanically (generally greater than or equal to 2.5m), and the extension part 51 structure is directly backfilled with concrete, or filled with backfill materials and compacted manually.

[0140] Taking the retaining wall assembly 5 as the boundary, a material having a strength greater than or equal to that of C15 concrete is filled in the backfill area 3 between the retaining wall assembly 5 and the second tunnel 2, and the material is filled upward until it abuts against the first tunnel 1, so as to form the second backfill structure 32, so that the second backfill structure 32 can bear a part of the weight of the first tunnel 1, that is, the second backfill structure 32 is used to replace the support piles 33 that cannot be installed there. In this process, the second backfill structure 32 not only solves the problem of mutual interference between the retaining wall assembly 5 and the support piles 33, but also uses a material having a strength greater than or equal to that of C15 concrete for backfilling, and achieves the required support strength and settlement requirements of the area through the characteristics of the material itself. In addition, the hardness of the retaining wall assembly 5 as specified in the standard specification, so that the second backfill structure 32 and the retaining wall assembly 5 jointly solve the problem that the filling material at the bottom of the backfill area cannot be compacted, thereby greatly reducing the influence of the settlement of the area where the second backfill structure 32 is located on the settlement of the backfill area and the structure above it;

[0141] The area located on the side of the retaining wall assembly 5 away from the second tunnel 2 has its bottom as the top of the extension part 51. The compacting machinery can enter this area and backfill the area with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to carry out filling operations, and then the first backfill structure 31 is compacted to finally form the first backfill structure 31 that meets the settlement standard. Moreover, a number of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31 to support a part of the deadweight of the upper end of the backfill area 3, thereby reducing the weight that the first backfill structure 31 needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure 31, and then on the basis of ensuring the settlement requirements, reducing the cost of the filler in the first backfill structure 31. Moreover, the cost of the added support piles 33 is much less than the reduced cost of the filler in the first backfill structure 31, and at the same time reduces the settlement risk of the segmented compaction method.

[0142] To sum up, in the structure of a small-spacing overlapping tunnel group described in the present application, when a retaining wall assembly 5 is provided, the second backfill structure 32 is extended upward to abut against the support of the first tunnel 1, thereby replacing the supporting piles 33 there, so as to avoid interference between the retaining wall assembly 5 and the supporting piles 33. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that part of the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of supporting piles 33 reduces the cost of the filling material in the first backfill structure 31, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0143] On the basis of the above, in a further preferred embodiment, the second backfill structure 32 is a structural member filled with C15 concrete.

[0144] The strength of the C15 concrete material can meet the strength requirement of the second backfill structure 32 formed by the C15 concrete material.

[0145] On the basis of the above, in a further preferred embodiment, the second backfill structure is a structural member filled with C20 concrete, C25 concrete or C30 concrete.

[0146] The strength of the C20 concrete, C25 concrete or C30 concrete is greater than that of the C15 concrete. By filling C20 concrete, C25 concrete or C30 concrete to form the second backfill structure, its performance can meet the support strength and settlement requirements required by the area, thereby greatly reducing the impact of settlement of the area where the second backfill structure is located on the settlement of the backfill area and structure above it.

[0147] On the basis of the above, in a further preferred embodiment, the first backfill structure 31 is a structure filled with cement soil.

[0148] Preferably, when the first tunnel 1 is a tubular tunnel structure, the support piles 33 are end-bearing piles;

[0149] When the first tunnel 1 is a U-shaped tunnel structure with an open upper end, the supporting piles 33 are high-pressure jet-jet piles, and the high-pressure jet-jet piles and the first backfill structure 31 jointly support the first tunnel 1 .

[0150] The construction of the end bearing pile is specifically as follows: firstly, a hole is drilled at the target position as required, then a steel cage is arranged in the hole, and then grouting is performed in the hole to form an end bearing pile, which has good performance and can independently support the force applied to the first tunnel 1 by the first tunnel 1 and the objects above the first tunnel 1 (including the deadweight and the dynamic load applied by the dynamic load above it);

[0151] The construction of high-pressure rotary jet piles is specifically as follows: first, small holes are drilled at the target location as required, and then high-pressure grouting is performed toward the holes to spray cement slurry into the soil layer and mix with the soil to form a continuous overlapping cement reinforcement body. Its performance is weaker than that of the end-bearing piles, so it needs to be subjected to force together with the first backfill structure 31 to meet the settlement requirements.

[0152] In actual construction, when the first tunnel 1 is a tubular tunnel structure, the backfill area 3 needs to withstand a large force (including the weight of the tunnel, the weight of the backfill and structures above the tunnel, and the dynamic load in and above the tunnel), and the support piles 33 are end-bearing piles to avoid increasing the cost of backfill materials in the first backfill structure 31, which has the best effect; when the first tunnel 1 is a U-shaped tunnel structure with an open upper end, the support piles 33 are high-pressure rotary jet piles, and the backfill area 3 needs to withstand a small force (including only the weight of the tunnel, and the dynamic load in the tunnel). Without increasing the cost of backfill materials in the first backfill structure 31, high-pressure rotary jet piles are used, and the high-pressure rotary jet piles and the first backfill structure 31 are jointly subjected to force, which can also meet its settlement requirements.

[0153] On the basis of the above, in a further preferred manner, a stop device 11 for preventing the first tunnel 1 from approaching the second tunnel 2 is provided on the side of the first tunnel 1 close to the second tunnel 2 , and the lower end of the stop device 11 is connected to the second backfill structure 32 .

[0154] The stop device 11 is used to prevent the displacement of the first tunnel 1 close to the second tunnel 2 from exceeding the allowable value during use, thereby preventing a major safety hazard. The lower end of the stop device 11 is connected to the second backfill structure 32, so that the second backfill structure 32 and the stop device 11 together form an L-shaped structure, which has a better effect in preventing the first tunnel 1 from approaching the second tunnel 2.

[0155] Example 4

[0156] like Figure 3 As shown, the construction method of the small-spacing overlapping tunnel group structure described in Example 3 described in this embodiment includes the following steps:

[0157] S1. Construction of the second tunnel 2;

[0158] S2. The retaining wall assembly 5 is provided at the root of the foundation slope 4 below the first tunnel 1;

[0159] S3. Fill the backfill area 3 between the retaining wall assembly 5 and the second tunnel 2 with a filler having a strength greater than or equal to that of C15 concrete to form the second backfill structure 32, and make the top of the second backfill structure 32 abut against and support the first tunnel 1;

[0160] S4. Filling the remaining space of the backfill area 3 with a filler and compacting it to form the first backfill structure 31;

[0161] S5. Construction of support piles 33 on the first backfill structure 31;

[0162] S6. Construct the first tunnel 1, where this section of the first tunnel 1 corresponds to the second tunnel 2 in step S1.

[0163] During the construction process, the following two situations usually occur:

[0164] Case 1: After the overall construction of the first tunnel 1 is completed, the second tunnel 2 is constructed. At this time, the construction process in this method is an explanation of the overall construction of the first tunnel 1 or the overall construction of the second tunnel 2;

[0165] Case 2: The first tunnel 1 or the second tunnel 2 is divided into many sections, and construction is carried out in sections. At this time, the construction process in this method is an explanation of the construction of the first tunnel 1 section and the construction of the corresponding section of the second tunnel 2.

[0166] The present application describes a construction method using a group of overlapping tunnels with small spacing. The backfill area 3 is surrounded by the first tunnel 1, the second tunnel 2, the foundation base surface 6 and the foundation slope 4 below the first tunnel 1, and is in the shape of an inverted trapezoid. The horizontal clearance distance of the backfill area 3 is the smallest at the foundation base surface 6. The higher it goes, the larger the horizontal clearance distance is. During the construction process, its range is determined by the theoretical design plan.

[0167] In the actual construction process, in order to prevent the possible deformation and instability of the foundation slope 4, the second tunnel 2 is constructed, and a retaining wall assembly 5 is set at the root of the foundation slope 4 to prevent the deformation and instability of the foundation slope. However, since the root of the foundation slope 4 is very close to the second tunnel 2 (generally less than 2.5m), the retaining wall assembly 5 will occupy the position of the support pile 33 closest to the second tunnel 2, making it impossible to construct the support pile 33.

[0168] During construction, the retaining wall assembly 5 is first constructed in accordance with relevant standards, specifically: the base of the retaining wall assembly 5 is first constructed. After the base of the retaining wall assembly 5 is constructed, the base, the foundation slope 4 and the plane where the top surface of the base is located form a triangular area. At this time, horizontal construction is performed from the top of the base toward the foundation slope 4, extending all the way to the foundation slope 4, thereby filling the triangular area and forming the extension portion 51.

[0169] Moreover, due to the provision of the extension part, the top surface width of the retaining wall assembly 5 can be compacted mechanically (generally greater than or equal to 2.5m), and the extension part 51 structure is directly backfilled with concrete, or filled with backfill materials and compacted manually.

[0170] In the above solution, the retaining wall assembly 5 can also be constructed before the construction of the second tunnel 2 of this section.

[0171] After the retaining wall assembly 5 is completed, the material with strength greater than or equal to that of C15 concrete is filled in the backfill area 3 between the retaining wall assembly 5 and the second tunnel 2 with the retaining wall assembly 5 as the boundary, and is filled upward until it abuts against the first tunnel 1 to form the second backfill structure 32, so that the second backfill structure 32 can bear part of the weight of the first tunnel 1, that is, the second backfill structure 32 is used to replace the support piles 33 that cannot be installed there. In this process, the second backfill structure 32 not only solves the problem of mutual interference between the retaining wall assembly 5 and the support piles 33, but also uses a material with strength greater than or equal to that of C15 concrete for backfilling, and achieves the required support strength and settlement requirements of the area through the characteristics of the material itself. In addition, the hardness of the retaining wall assembly 5 as specified in the standard specification, so that the second backfill structure 32 and the retaining wall assembly 5 jointly solve the problem that the filling material at the bottom of the backfill area cannot be compacted, thereby greatly reducing the influence of the settlement of the area where the second backfill structure 32 is located on the settlement of the backfill area and the structure above it;

[0172] After the construction of the second backfill structure 32 is completed, in the area located on the side of the retaining wall assembly 5 away from the second tunnel 2, the bottom of which is the top of the extension part 51, the compacting machinery can enter this area, and can backfill the area with commonly used backfill materials (cement soil, backfill materials with equal strength or stronger) to carry out filling operations, and then the first backfill structure 31 is compacted to finally form the first backfill structure 31 that meets the settlement standard. Moreover, a number of support piles 33 for supporting the first tunnel 1 are vertically arranged in the first backfill structure 31 to support a part of the deadweight of the upper end of the backfill area 3, thereby reducing the weight that the first backfill structure 31 needs to bear, thereby reducing the hardness requirement of the filler in the first backfill structure 31, and then on the basis of ensuring the settlement requirements, reducing the cost of the filler in the first backfill structure 31, and the cost of the added support piles 33 is much less than the reduced cost of the filler in the first backfill structure 31, while reducing the settlement risk of the segmented compaction method.

[0173] To sum up, the construction method of the present application adopting a small-spacing overlapping tunnel group structure, when a retaining wall assembly 5 is provided, extends the second backfill structure 32 upward to abut against the support of the first tunnel 1, thereby replacing the support piles 33 there, so as to avoid interference between the retaining wall assembly 5 and the support piles 33. At the same time, while ensuring that the entire backfill area meets the settlement standards, the problem that the filling material at the bottom of the backfill area cannot be compacted is solved. At the same time, the use of support piles 33 reduces the cost of the filling material in the first backfill structure 31, thereby reducing the overall construction cost of the three-dimensional tunnel group.

[0174] After the main structure of the first tunnel 1 is completed, backfill construction is performed in the upper backfill area 8 above the first tunnel 1 and the second tunnel 2, so that the first tunnel 1 and the second tunnel 2 are located underground.

[0175] 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 construction method for a small-spacing three-dimensional tunnel group structure, characterized in that: A small-spacing three-dimensional tunnel group structure, comprising a first tunnel (1), a second tunnel (2) and a backfill area (3) located below the first tunnel (1), the backfill area (3) being located on one side of the second tunnel (2), the backfill area (3) being filled with a first backfill structure (31) and a second backfill structure (32) in sequence from top to bottom, a plurality of support piles (33) for supporting the first tunnel (1) being vertically arranged in the first backfill structure (31), the upper ends of the support piles (33) being in contact with the first tunnel (1), and the second backfill structure (32) being a structural member filled with a material having a strength greater than or equal to that of C15 concrete; The structure of the three-dimensional tunnel group with small spacing is determined by whether the filling material in the minimum horizontal gap between the foundation slope (4) and the second tunnel (2) can be compacted into the interface between the first backfill structure (31) and the second backfill structure (32) according to the settlement standard; In the area above the interface, the minimum horizontal clearance between the foundation slope (4) and the second tunnel (2) is such that compaction machinery can enter the area; The construction method comprises the following steps: A1. constructing the second tunnel (2); A2. Filling the backfill area (3) with a filler having a strength greater than or equal to that of C15 concrete to form the second backfill structure (32); A3. Filling the remaining space of the backfill area (3) with a filler and compacting it to form the first backfill structure (31); A4. Constructing support piles (33) on the first backfill structure (31); A5. Constructing the first tunnel (1).

2. A construction method according to claim 1, characterized in that: The second backfill structure (32) is a structural member filled with C15 concrete.

3. A construction method according to claim 1, characterized in that: When the first tunnel (1) is a tubular tunnel structure, the supporting piles (33) are end-bearing piles.

4. A construction method according to claim 1, characterized in that: When the first tunnel (1) is a U-shaped tunnel structure with an open upper end, the supporting piles (33) are high-pressure jet grouting piles, and the high-pressure jet grouting piles and the first backfill structure (31) jointly support the first tunnel (1).

5. A small-pitch overlapping tunnel group structure, comprising a first tunnel (1), a second tunnel (2) and a backfill area (3) located below the first tunnel (1), characterized in that: The backfill area (3) is located on one side of the second tunnel (2), and a first backfill structure (31) and a second backfill structure (32) are arranged horizontally in sequence in the backfill area (3), wherein: A plurality of support piles (33) for supporting the first tunnel (1) are vertically arranged in the first backfill structure (31), and the upper ends of the support piles (33) are in contact with the first tunnel (1); The second backfill structure (32) is in contact with the second tunnel (2) at a side facing away from the first backfill structure (31), and the upper end of the second backfill structure (32) is in contact with the first tunnel (1). The second backfill structure (32) is a structural member filled with a material having a strength greater than or equal to that of C15 concrete; A retaining wall assembly (5) is used to prevent the foundation slope (4) from deforming and becoming unstable. The retaining wall assembly (5) is arranged at the contact point between the first backfill structure (31) and the second backfill structure (32). The top of the retaining wall assembly (5) has an extension portion (51) extending laterally toward the foundation slope (4). The extension portion (51) is used to fit the foundation slope (4). The extension portion (51) enables the top surface width of the retaining wall assembly (5) to be compacted by mechanical operations. With the retaining wall assembly (5) as the boundary, a material having a strength greater than or equal to that of C15 concrete is filled in the backfill area (3) between the retaining wall assembly (5) and the second tunnel (2), and the material is filled upward until it abuts against the first tunnel (1), thereby forming the second backfill structure (32).

6. A small-spacing overlapping tunnel group structure according to claim 5, characterized in that: The second backfill structure (32) is a structural member filled with C15 concrete.

7. The structure of a group of overlapping tunnels with small spacing according to claim 5, characterized in that: When the first tunnel (1) is a tubular tunnel structure, the support piles (33) are end-bearing piles; When the first tunnel (1) is a U-shaped tunnel structure with an upper end open, the supporting piles (33) are high-pressure jet grouting piles, and the high-pressure jet grouting piles and the first backfill structure (31) jointly support the first tunnel (1).

8. A small-spacing overlapping tunnel group structure according to any one of claims 5 to 7, characterized in that: A stop device (11) is provided on the side of the first tunnel (1) close to the second tunnel (2) for preventing the first tunnel (1) from approaching the second tunnel (2), and the lower end of the stop device (11) is connected to the second backfill structure (32).

9. A construction method for a small-spacing overlapping tunnel group structure using any one of claims 5-8, characterized in that: The steps include: S1. Construction of the second tunnel (2); S2. Arranging the retaining wall assembly (5) at the root of the foundation slope (4) below the first tunnel (1); S3. Filling the backfill area (3) between the retaining wall assembly (5) and the second tunnel (2) with a filler having a strength greater than or equal to that of C15 concrete to form the second backfill structure (32), and making the top of the second backfill structure (32) abut against and support the first tunnel (1); S4. Filling the remaining space of the backfill area (3) with a filler and compacting it to form the first backfill structure (31); S5. Construction of support piles (33) on the first backfill structure (31); S6. Construct the first tunnel (1).

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