Construction method for processing underground space structure within limit with low disturbance

Abstract

The application discloses a low-disturbance construction method for processing an underground space structure invading a limit, and relates to the technical field of urban underground engineering construction. The construction method comprises the following steps: removing the soil on the top of the invading part, and opening a temporary construction passage on the top plate; constructing an inner support structure wall and a temporary inclined support in the existing underground structure; continuously drilling holes on the bottom plate and the side walls of the existing underground structure on the two sides intersecting with the to-be-constructed supporting structure to form two partition joints; cutting the top plate of the existing underground structure to form an open space between the inner support structure wall and the existing supporting structure; removing the temporary inclined support and backfilling in the open space to form a backfill body; excavating a groove on the backfill body, and constructing the to-be-constructed supporting structure in the groove. The application discards the traditional process of overall excavation first and invading limit processing later, realizes large-excavation-free and low-disturbance construction, and significantly reduces the stress mutation of the soil and the additional deformation of the existing structure caused by the unloading of earthwork.

Description

Technical Field

[0001] This application relates to the field of urban underground engineering construction technology, specifically to a construction method for low-disturbance treatment of encroaching underground space structures. Background Technology

[0002] With the acceleration of urbanization, the development and utilization of urban underground space is becoming increasingly frequent, and the mutual influence between underground space structures is becoming more and more prominent. During the development of underground space, proposed underground structures often conflict with existing underground structures spatially, a phenomenon known as encroachment. Encroachment typically manifests as the construction area of ​​the proposed structure encroaching on the protection zone of the existing structure. If not handled properly, this can lead to changes in the stress state of the existing structure, limitations on its functionality, and even safety hazards. Encroachment is prevalent among underground structures such as subway tunnels, underground utility tunnels, basements, and pile foundations, especially in densely populated areas such as urban core areas and transportation hubs, and has become a key technical challenge restricting the efficient development and sustainable utilization of underground space.

[0003] To address the issue of encroachment by underground structures, the traditional approach mainly employs a construction mode that combines open-cut exposure with structural modification. The specific steps are as follows: First, large-scale earthwork excavation is carried out in the encroaching area until the encroaching portion of the existing underground structure is fully exposed. Second, the exposed encroaching structure is partially demolished, reinforced, or rerouted, for example, by cutting off the intruding concrete structure, severing the reinforcing bars, and recasting the joints. Finally, after the modification of the encroaching structure is completed, the construction of the proposed underground structure is carried out.

[0004] This treatment method relies on large-scale excavation operations, has a clear construction process, and a mature technical approach, and was widely used in early underground engineering construction. However, this method also has the following drawbacks: large-area excavation produces a strong unloading effect on the surrounding soil, causing significant disturbance and leading to a redistribution of the soil stress field. This can easily trigger large horizontal displacements and vertical settlements in existing underground structures, seriously affecting their structural safety and functionality, especially in soft soil areas or around sensitive building complexes, where the risks are even more pronounced. Furthermore, the excavation process requires the installation of complex support systems, such as retaining piles and internal bracing, which not only increases the construction difficulty and time but also raises project costs. Summary of the Invention

[0005] The purpose of this application is to provide a construction method for low-disturbance treatment of encroaching underground space structures, which solves the problem of large unloading disturbance in traditional encroachment treatment.

[0006] The technical solution adopted by this application to solve its technical problem is: A construction method for treating encroaching underground space structures with low disturbance includes: S1. Remove the top soil covering the encroaching portion of the existing underground structure and open a temporary construction access point on the top slab of the encroaching portion. S2. Construct an internal support structure wall between the top and bottom slabs of the existing underground structure and on one side of its encroachment portion, and construct temporary oblique supports within the existing underground structure to connect the portions of the proposed support structure on both sides. S3. On both sides where the existing underground structure’s bottom slab and side walls intersect with the proposed support structure, drill holes continuously along the intersection line of the existing underground structure and the proposed support structure to form two partition joints. S4. Cut the top slab of the existing underground structure between the inner supporting structure wall and the existing retaining structure to create an open space with an open top between the inner supporting structure wall and the existing retaining structure. S5. Remove the temporary inclined supports and backfill the open space with engineering materials to the natural elevation to form a backfill body; S6. Excavate on the backfill body at the location corresponding to the proposed support structure to form a trench for constructing the proposed support structure, and construct the proposed support structure in the trench. S7. Remove the encroaching portions of the existing support structure and existing underground structure.

[0007] Furthermore, the overburden on top of the encroaching portion of the existing underground structure was removed using a natural slope method.

[0008] Furthermore, the temporary inclined support includes an inclined support rod and connecting plates fixed at both ends of the inclined support rod. The connecting plates are connected to the existing underground structure by anchoring expansion bolts.

[0009] Furthermore, before constructing the partition joint, pre-grouting is performed under the base slab of the encroaching portion of the existing underground structure.

[0010] Furthermore, continuous drilling was carried out using a water-cooled drill along the intersection line of the existing underground structure's bottom slab and the proposed support structure, and continuous drilling was carried out using a geological drill along the intersection line of the existing underground structure's sidewall and the proposed support structure.

[0011] Furthermore, before backfilling the engineering materials, a waterproof layer is first constructed on the side of the internal support structure wall facing the encroachment of the existing underground structure.

[0012] Furthermore, the method of backfilling the open space using engineering materials includes: pouring concrete at the bottom of the open space to form a seepage-proof sealing layer; backfilling the seepage-proof sealing layer with stone chips to form a stone chip layer; and backfilling the stone chip layer with clay to the natural elevation to form a clay layer.

[0013] Furthermore, the method for excavating trenches on the backfill includes: marking out the construction location of the proposed support structure on the top of the backfill, and laying platform protective steel plates on both sides of the construction location of the proposed support structure; setting up a rotary drilling rig on the platform protective steel plates, and using the rotary drilling rig to cut trenches on the backfill.

[0014] Furthermore, at the bottom slab of the existing underground structure, the rotary drilling rig uses a standard barrel-shaped rotary drilling cutter head to cut and create trenches; at the sidewalls of the existing underground structure, the rotary drilling rig uses a composite rotary drilling cutter head to cut and create trenches.

[0015] Furthermore, after the proposed support structure is constructed, a drainage ditch is constructed on top of the backfill, with the drainage ditch closely attached to the side of the proposed support structure away from the encroachment of the existing underground structure.

[0016] The beneficial effects of this application are: The construction method for treating encroaching underground space structures with low disturbance provided in this application embodiment eliminates the traditional process of first excavating the entire structure and then treating the encroachment by removing only the local overburden and carrying out minor operations inside the existing underground structure. This achieves construction without large-scale excavation and with low disturbance, significantly reducing the sudden changes in soil stress and additional deformation of the existing structure caused by earthwork unloading. It avoids the structural safety risks of large horizontal and vertical displacements of the existing structure during the excavation and unloading process, ensuring the safety of use and operation of the existing underground structure during the encroachment treatment period, while also significantly reducing the cost of earthwork excavation and support structure construction. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the construction method provided in the embodiments of this application; Figure 2 This is a schematic diagram showing the encroachment relationship between the existing underground structure and the proposed underground structure. Figure 3 yes Figure 2 Top view; Figure 4 This is a structural diagram showing the internal support wall and temporary diagonal bracing after construction. Figure 5 yes Figure 4 Top view; Figure 6 This is a schematic diagram of a temporary inclined support structure; Figure 7 This is a structural diagram of the construction of partition joints in the base slab and side walls of the existing underground structure. Figure 8 This is a schematic diagram of a structure created by cutting the top slab of an existing underground structure to form an open space. Figure 9 This is a structural diagram of backfilling engineering materials in an open space; Figure 10 This is a schematic diagram of a structure for excavating a trench in the backfill; Figure 11 This is a structural diagram of a common barrel-shaped rotary drilling cutter head; Figure 12 This is a schematic diagram of the structure of a composite rotary drilling cutter head; Figure 13 This is a structural diagram of excavating a cavity in the base slab and side walls of an existing underground structure. Figure 14 This is a structural schematic diagram of the proposed support structure to be constructed within the trench cavity; Figure 15 This is a structural diagram of the proposed underground structure being constructed on one side of the proposed support structure.

[0019] Figure label: 1- Existing underground structure; 11- Temporary construction access point; 12- Partition joint; 13- Open space; 14- Partition block; 2- Existing support structure; 3-Proposed underground structure; 4-Proposed support structure; 5-Internal supporting structural wall; 51-Waterproof layer; 6-Temporary diagonal support; 61-Diagonal support rod; 62-Connecting plate; 63-Anchoring expansion bolt; 7-Backfill; 71-Trench cavity; 72-Impact seal layer; 73-Stone slag layer; 74-Clay layer; 75-Intercepting ditch; 8-Platform protection steel plate; 9-Rotary drilling rig; 91-Ordinary barrel-type rotary drilling cutter head; 92-Composite rotary drilling cutter head. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0021] In the description of this application, the terms "upper," "lower," "left," "right," "front," "rear," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Unless otherwise specified, the above-mentioned orientational descriptions can be flexibly set in actual application, provided that the relative positional relationships shown in the accompanying drawings are satisfied.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] See Figure 1 This application provides a construction method for low-disturbance treatment of encroaching underground space structures, including the following steps: S1. Remove the top soil covering the encroaching portion of the existing underground structure 1, and open a temporary construction access point 11 on the top slab of the encroaching portion.

[0024] See Figure 2 The existing underground structure 1 and the existing support structure 2 are represented by solid lines, and the proposed underground structure 3 and the proposed support structure 4 are represented by dashed lines. The existing support structure 2 is located to the right of the existing underground structure 1, and the proposed support structure 4 is located to the left of the proposed underground structure 3. Both the existing underground structure 1 and the proposed underground structure 3 can be underground building structures such as tunnels, underground factories, subway stations, and underground shopping malls. Both the existing support structure 2 and the proposed support structure 4 can be underground continuous walls.

[0025] See Figure 2 , Figure 3 The area where existing underground structure 1 and existing support structure 2 are constructed is called the existing area; the area where proposed underground structure 3 and proposed support structure 4 are to be constructed is called the proposed area; and the area where the existing area and the proposed area intersect is called the encroachment area. Therefore, the encroachment portion of existing underground structure 1 refers to its portion within the encroachment area.

[0026] See Figure 4 , Figure 5At the top of the encroaching portion of the existing underground structure 1, if the top overburden is shallow, the geological conditions are good, and there are no important surrounding buildings or structures, a natural slope excavation can be used to create a stable slope, thereby exposing the top slab of the encroaching portion of the existing underground structure 1. This method can reduce the amount of support work under certain conditions and has the advantages of simple construction, low equipment investment, and low cost. However, the slope stability should be assessed in conjunction with factors such as the site soil quality, groundwater level, and excavation depth. Dewatering or local support measures should be taken if necessary to ensure construction safety. If site conditions are limited and slope excavation is not feasible, sheet piles, reverse construction methods, or other support methods can be selected for overburden excavation. The specific scheme should be determined after technical and economic comparison, and will not be elaborated here.

[0027] After exposing the top slab of the existing underground structure 1, a temporary construction access point 11 should be opened at an appropriate location, based on the structural stress characteristics and safety assessment results, without affecting the overall load-bearing capacity of the structure, for the vertical transportation of subsequent construction materials and small equipment. Structural calculations should be performed before opening the temporary construction access point 11, and reinforcement measures should be taken if necessary to ensure structural safety and construction convenience.

[0028] S2. Construct an internal support structure wall 5 between the top and bottom slabs of the existing underground structure 1 and on one side of its encroaching portion, and construct a temporary oblique support 6 within the existing underground structure 1 to connect the portions of the proposed support structure 4 on both sides.

[0029] See Figure 4 , Figure 5 Construction workers transported the materials and small construction equipment required for the construction of the internal support structure wall 5 and the temporary inclined support 6 to the existing underground structure 1 through the temporary construction access 11, and carried out internal reinforcement construction accordingly. The internal support structure wall 5 is constructed between the top and bottom slabs of the existing underground structure 1, located to the left of the proposed support structure 4, and parallel to the proposed support structure 4. After the construction of the internal support structure wall 5 is completed, it serves as a permanent sealing structure to replace the subsequently cut-off encroaching part, reconstruct a stable underground space boundary, achieve stress isolation and system rebalancing between the encroaching part and the retained part, and ensure the long-term safety of the retained part during subsequent construction and operation phases.

[0030] The temporary inclined supports 6 can be made of steel components and are arranged diagonally on both sides of the proposed support structure 4. Their ends are reliably connected to the encroaching and retained portions of the existing underground structure 1, respectively, forming a temporary support system. After the temporary inclined supports 6 are constructed, they act as temporary supports, suppressing additional deformation and tensile stress caused by structural discontinuity during the removal of the encroaching portion of the existing underground structure 1, preventing uneven cracking or damage to the retained portion, and ensuring the overall stability of the structure.

[0031] For example, see Figure 6 The temporary inclined support 6 includes an inclined support rod 61 and connecting plates 62 fixed at both ends of the inclined support rod 61. The connecting plates 62 are reliably connected to the existing underground structure 1 via anchoring expansion bolts 63. The inclined support rod 61 can be made of rectangular steel tubing, and the connecting plates 62 are made of steel plate. The inclined support rod 61 and the connecting plates 62 are welded together. By connecting the connecting plates 62 to the existing underground structure 1 using detachable anchoring expansion bolts 63, the temporary inclined support 6 is quick to install and reliably stressed, and it is also easy to dismantle quickly later, improving on-site construction efficiency.

[0032] S3. On both sides where the existing underground structure 1 and its sidewalls intersect with the proposed support structure 4, drill holes continuously along the intersection line of the existing underground structure 1 and the proposed support structure 4 to form two partition joints 12.

[0033] Correspondingly, by continuously drilling two partition joints 12 along the intersection line of the existing underground structure 1 and the proposed support structure 4, a partition block 14 is formed at the intersection of the bottom slab and sidewalls of the existing underground structure 1 and the proposed support structure 4, located between the two partition joints 12. This pre-cuts the rigid connection between the partition block 14 and other parts, minimizing the impact of vibration, shearing and uneven settlement on the remaining part of the existing underground structure 1 during subsequent construction. At the same time, the partition joint 12 can also provide an overall and controllable boundary for subsequent construction, avoiding over-excavation or accidental damage, and improving construction accuracy.

[0034] For example, see Figure 7 In the figure, AA' and BB' are two intersection lines where the existing underground structure 1 and the proposed support structure 4 intersect. Based on AA' and BB', holes are continuously drilled along their direction to form two linear partition joints 12. Among them, water-cooled drilling is used to continuously drill holes along the intersection line between the bottom plate of the existing underground structure 1 and the proposed support structure 4, and geological drilling is used to continuously drill holes along the intersection line between the side wall of the existing underground structure 1 and the proposed support structure 4.

[0035] Correspondingly, the water-cooled drill has a smooth cutting action, minimal vibration, and regular hole formation, enabling cold cutting in areas with dense reinforcement in the base slab while preserving the integrity of the original structure to the maximum extent. The geological drill has a fast advance and high torque, allowing for rapid penetration through thick sections of the sidewalls and shortening the time required to form partition joints. By using the water-cooled drill for continuous hole formation at the intersection lines of the base slab and the geological drill for continuous hole formation at the intersection lines of the sidewalls, the advantages of both drilling tools can be fully utilized. The combination of the two not only ensures the core recovery rate but also significantly reduces the impact disturbance, noise, and dust caused by traditional chiseling, achieving low-disturbance partition construction. At the same time, it provides neat and low-damage boundary conditions for the precise embedding of the subsequent proposed support structure 4.

[0036] In geological conditions such as water abundance, to prevent the adverse effects of groundwater outflow on the foundation and subsequent construction, grouting is pre-injected below the base slab of the encroaching portion of the existing underground structure 1 before the construction of partition joint 12. Accordingly, by pre-grouting in the soil below the base slab of the encroaching portion of the existing underground structure 1, a curtain-like water-stop structure is formed, cutting off the confined water channel. This prevents water inflow and quicksand during subsequent continuous drilling, maintains the bearing capacity of the foundation, and provides a dry and stable working environment for subsequent construction.

[0037] The pre-grouting process should be completed before the construction of partition joint 12. It can be arranged in any of the steps S1-S3, but it must be ensured that its implementation sequence is no later than the construction of partition joint 12.

[0038] S4. Cut the top slab of the existing underground structure 1 between the inner supporting structural wall 5 and the existing retaining structure 2 to form an open space 13 with an open top between the inner supporting structural wall 5 and the existing retaining structure 2.

[0039] See Figure 8 After the partition joint 12 is completed, the top slab of the existing underground structure 1 between the inner supporting structure wall 5 and the existing retaining structure 2 is cut using a wire saw. After the cut top slab is removed, an open space 13 with an open top is formed between the inner supporting structure wall 5 and the existing retaining structure 2, so that the encroached part changes from a closed box to an open groove, providing a wide channel for the backfilling of subsequent engineering materials. At the same time, the structural load is released in advance after the top slab is cut off, which makes it easy to monitor the deformation and stress of the retained part in real time. If any abnormality is found, the construction parameters can be adjusted immediately.

[0040] S5. Remove the temporary inclined support 6, and backfill the open space 13 with engineering materials to the natural elevation to form a backfill body 7.

[0041] See Figure 9 By removing the temporary inclined support 6, the temporary support structure between the encroaching part and the retained part of the existing underground structure 1 is removed. By backfilling the engineering materials in the open space 13 to the natural elevation, a backfill body 7 is formed, which has the functions of both water-stop curtain and trench wall stabilization. The self-weight balance of the backfill body 7 is used to eliminate the lateral free surface, suppress the rebound of the existing underground structure 1 and the displacement of the surrounding soil, and provide a stable platform and uniform reaction base for the construction of the subsequent proposed support structure 4. This eliminates the need for additional support, simplifies the process, shortens the construction period, and reduces the cost.

[0042] For example, see Figure 9 The method of backfilling open space 13 using engineering materials includes the following steps: S5.1. Concrete is poured at the bottom of the open space 13 to form a seepage-proof sealing layer 72. The seepage-proof sealing layer 72 is made of low-grade concrete, and its pouring height can be greater than or equal to half of the net height of the existing underground structure 1, which not only ensures the seepage-proof sealing effect at the bottom, but also ensures the structural and construction safety of the existing underground structure 1 after the side walls are depressurized.

[0043] S5.2. Backfill stone chips on the seepage-proof sealing layer 72 to form a stone chip layer 73. The height of the stone chip backfill is equal to the remaining part of the net height of the existing underground structure 1. The stone chip layer 73 serves to drain water vertically and improve the acid-base environment of the soil.

[0044] S5.3. Backfill clay onto the ballast layer 73 to the natural elevation to form a clay layer 74. The clay layer 74 is backfilled to the natural elevation to ensure the impermeability of the top.

[0045] Correspondingly, backfill body 7 adopts a three-level backfill structure with a concrete bottom, a stone slag middle layer, and a clay top layer. The bottom layer of concrete seals the joints in one go, forming a continuous water-stopping curtain. The middle layer of stone slag has large pores and drains quickly, which can instantly dissipate the excess pore pressure on the trench side. The top layer of clay not only restores the original surface load but also prevents rainwater infiltration. The three-layer backfill structure works together to achieve integrated water-stopping, pressure reduction, and seepage prevention, eliminating the need for additional waterproofing and drainage measures. It can bear the load of subsequent trenching machinery 3 days after backfilling, shortening the construction period.

[0046] See Figure 4 , Figure 8 , Figure 9 In order to improve the waterproofing effect of the internal support structure wall 5, before backfilling the engineering materials, a waterproof layer 51 is first constructed on the side of the internal support structure wall 5 facing the encroachment part of the existing underground structure 1.

[0047] The waterproof layer 51 must be constructed continuously in one go after the construction of the internal supporting structural wall 5 is completed and before the backfill material is applied. It can be implemented in any of steps S2-S5. Specifically, the construction method for the waterproof layer 51 may include: first, attaching a polymer waterproof membrane to the right side of the internal supporting structural wall 5, and then applying a layer of cement mortar greater than or equal to 20mm over the polymer waterproof membrane. By setting the waterproof layer 51 on the internal supporting structural wall 5, a complete and continuous water-resistant barrier can be formed, blocking the seepage channel between the backfill area and the existing underground structure 1, thus achieving a seepage prevention effect.

[0048] S6. Excavate on the backfill body 7 at the position corresponding to the proposed support structure 4 to form a cavity 71 for construction of the proposed support structure 4, and construct the proposed support structure 4 in the cavity 71.

[0049] Correspondingly, by precisely excavating the trench cavity 71 on the backfill body 7, the construction interface of the proposed support structure 4 is formed. The uniform and dense material that has been backfilled serves as lateral constraint, preventing trench wall collapse and over-excavation, reducing additional support and dewatering costs, and improving the construction quality of the proposed support structure 4. To improve the trenching quality, the trench cavity 71 must be kept full of mud that balances the wall pressure during the trenching process, and the slurry level must be kept stable.

[0050] See Figure 10 The method for excavating a cavity 71 on the backfill 7 includes the following steps: S6.1 Mark out the construction location of the proposed support structure 4 on the top of the backfill 7, and lay platform protection steel plates 8 on both sides of the construction location of the proposed support structure 4.

[0051] S6.2. A rotary drilling rig 9 is erected on the platform protection steel plate 8, and the rotary drilling rig 9 is used to cut grooves in the backfill body 7.

[0052] Correspondingly, by accurately laying out the top surface of the backfill 7 and laying a platform to protect the steel plate 8, a continuous and hard construction platform is formed. This not only prevents the top surface of the backfill 7 from being crushed and loosened by the tracks of the rotary drilling rig 9, but also provides a stable foundation for the rotary drilling rig 9 to walk and position. The rotary drilling rig 9 uses the steel plate platform to perform trenching operations. The trench walls are highly vertical and the operation is continuous, which significantly reduces the amount of earthwork transported and the time for dewatering, achieving efficient and green construction with "fast positioning, good trenching, and minimal disturbance".

[0053] During the trenching process of the cavity 71, the rotary drilling rig 9 is used to perform core extraction on the partition block 14 between the two partition joints 12 segment by segment. Since the partition block 14 is completely separated from the rest of the existing underground structure 1, the core extraction process of the partition block 14 is without pulling or knocking, and the rest of the existing underground structure 1 is almost completely disturbed.

[0054] To further achieve low-disturbance construction, see Figure 11 , Figure 12 , Figure 13 At the bottom slab of the existing underground structure 1, the rotary drilling rig 9 uses a common barrel-shaped rotary drilling cutter head 91 to cut and groove; at the side wall of the existing underground structure 1, the rotary drilling rig 9 uses a composite rotary drilling cutter head 92 to cut and groove.

[0055] Correspondingly, when the rotary drilling rig 9 drills to the base slab area, it switches to a standard barrel-shaped rotary cutting head 91, utilizing its large opening and low torque characteristics to quickly cut the plain concrete, avoiding additional shear force on the base slab reinforcement. When the rotary drilling rig 9 drills to the side wall area, it switches to a composite rotary cutting head 92, milling first and then cutting, simultaneously cutting and discharging the reinforcement, which can cut the main reinforcement in one go without hooking the wall, while the unloading groove reduces the soil squeezing effect. The segmented switching of the two cutting heads and low-speed grooving achieve low-disturbance demolition without lifting the base slab, cracking the side walls, or tearing the reinforcement.

[0056] See Figure 14 Once the trench cavity 71 has passed the acceptance inspection according to the design dimensions, verticality and bottom elevation, the existing trench clearance can be used to complete the construction of the proposed support structure 4 by following conventional procedures such as bottom cleaning, trench inspection, installation of steel cages or steel sections, and pouring concrete or sprayed concrete. The trench wall is protected by a combination of backfill 7 and rotary drilling mud, without the need for additional support. The construction quality is easy to control, the process is compact, and the construction period of the proposed support structure 4 is significantly shortened.

[0057] S7. Demolish the encroaching portions of the existing support structure 2 and the existing underground structure 1.

[0058] See Figure 15 Once the proposed support structure 4 is completed and the concrete strength reaches the design value, the existing structure on its right side can be demolished, thus completing the treatment of the underground space encroachment. Then, the proposed underground structure 3 can be constructed on the right side of the proposed support structure 4 using conventional techniques.

[0059] See Figure 15 After the proposed support structure 4 is constructed, a drainage ditch 75 is constructed on top of the backfill 7. The drainage ditch 75 is closely attached to the side of the proposed support structure 4 away from the encroachment portion of the existing underground structure 1. Preferably, the drainage ditch 75 is constructed before the proposed underground structure 3.

[0060] Correspondingly, the intercepting ditch 75 is close to the left side of the proposed support structure 4, which can intercept water from the top surface of the backfill 7 and the slope above it, preventing surface water from overflowing the top of the proposed support structure 4 and flowing into the newly built foundation pit on the right side; at the same time, the intercepting ditch 75 can also serve as a permanent drainage facility, taking into account both emergency drainage during the construction period and long-term drainage during the operation period.

[0061] The construction method for treating encroaching underground space structures with low disturbance provided in this application embodiment eliminates the traditional process of first excavating the entire structure and then treating the encroachment by removing only the local overburden and carrying out minor operations inside the existing underground structure 1. This achieves construction without large-scale excavation and with low disturbance, significantly reducing the sudden changes in soil stress and additional deformation of the existing structure caused by earthwork unloading. It avoids the structural safety risks of large horizontal and vertical displacements of the existing structure during the excavation and unloading process, ensuring the safety of use and operation of the existing underground structure 1 during the encroachment treatment period, while also significantly reducing the cost of earthwork excavation and support structure construction.

[0062] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A construction method for treating encroaching underground space structures with low disturbance, characterized in that, include: S1. Remove the soil covering the top of the encroaching part of the existing underground structure (1) and open a temporary construction passage (11) on the top slab of the encroaching part. S2. Construct an internal support structure wall (5) between the top and bottom slabs of the existing underground structure (1) and on one side of its encroachment portion, and construct a temporary inclined support (6) within the existing underground structure (1) that connects the portions on both sides of the proposed support structure (4). S3. On both sides where the existing underground structure (1) and the side wall intersect with the proposed support structure (4), drill holes continuously along the intersection line of the existing underground structure (1) and the proposed support structure (4) to form two partition joints (12). S4. Cut the top plate of the existing underground structure (1) between the inner supporting structure wall (5) and the existing support structure (2) to form an open space (13) with an open top between the inner supporting structure wall (5) and the existing support structure (2). S5. Remove the temporary inclined support (6) and backfill the open space (13) to the natural elevation using engineering materials to form a backfill body (7). S6. Excavate on the backfill (7) at the position corresponding to the proposed support structure (4) to form a cavity (71) for the construction of the proposed support structure (4), and construct the proposed support structure (4) in the cavity (71). S7. Demolish the encroaching parts of the existing support structure (2) and the existing underground structure (1); Water-powered drilling was used to continuously drill holes along the intersection line of the bottom slab of the existing underground structure (1) and the proposed support structure (4), and geological drilling was used to continuously drill holes along the intersection line of the side wall of the existing underground structure (1) and the proposed support structure (4). Before backfilling the engineering materials, a waterproof layer (51) is first constructed on the side of the internal support structure wall (5) facing the encroachment of the existing underground structure (1). Methods of backfilling open spaces (13) using engineering materials include: Concrete is poured at the bottom of the open space (13) to form a seepage-proof sealing layer (72). Backfill the impermeable sealing layer (72) with stone chips to form a stone chip layer (73); Clay is backfilled on the rubble layer (73) to the natural elevation to form a clay layer (74).

2. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 1, characterized in that, The overburden on top of the encroaching portion of the existing underground structure (1) was removed by natural slope method.

3. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 1, characterized in that, The temporary inclined support (6) includes an inclined support rod (61) and a connecting plate (62) fixed at both ends of the inclined support rod (61). The connecting plate (62) is connected to the existing underground structure (1) by an anchoring expansion bolt (63).

4. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 1, characterized in that, Before constructing the partition joint (12), pre-grouting is performed below the bottom slab of the encroaching portion of the existing underground structure (1).

5. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 1, characterized in that, The method of excavating a cavity (71) on the backfill (7) includes: The construction position of the proposed support structure (4) is laid out on the top of the backfill (7), and platform protective steel plates (8) are laid on both sides of the construction position of the proposed support structure (4). A rotary drilling rig (9) is erected on the platform protective steel plate (8), and the rotary drilling rig (9) is used to cut grooves on the backfill (7).

6. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 5, characterized in that, At the bottom slab of the existing underground structure (1), the rotary drilling rig (9) uses a common barrel-shaped rotary drilling cutter head (91) to cut and trench. At the side wall of the existing underground structure (1), the rotary drilling rig (9) uses a composite rotary drilling cutter head (92) to cut and trench.

7. The construction method for low-disturbance treatment of encroaching underground space structures according to claim 1, characterized in that, After the proposed support structure (4) is completed, a water interception ditch (75) is constructed on the top of the backfill (7). The water interception ditch (75) is close to the side of the proposed support structure (4) away from the encroachment of the existing underground structure (1).

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