An external pressure device for treating convergence deformation of an existing shield tunnel and a construction method thereof

Abstract

The present application relates to a kind of treatment of existing shield tunnel convergence deformation external pressure device and construction method, belong to shield tunnel field.The construction method includes: two vertical shafts and vertical shaft support structure are made on the both sides of tunnel structure;Two vertical holes are made, two prefabricated external pressure prestressed plates are respectively sunk to the both sides of tunnel structure along two vertical holes;Local reinforcement is carried out to stratum by grouting port, and then grouting port is excavated to form corresponding operation port, telescopic rod is used to cross stratum to the corresponding operation port of another side of tunnel structure by reserved hole from one side of operation port;When telescopic rod crosses stratum, prestressed strand is pulled through one side of operation port, reserved hole and stratum crossing hole, until it reaches the other side of operation port, two ends of prestressed strand are connected with anchoring system, one end is fixed, the other end is connected with jack and tensioned, to apply external pressure prestress to tunnel structure by prefabricated external pressure prestressed plate.The external pressure device of the present application can be obtained by using the above construction method.

Description

Technical Field

[0001] This invention relates to the field of shield tunnel technology, and in particular to an external pressure device and construction method for managing the convergence deformation of existing shield tunnels. Background Technology

[0002] With the rapid development of urban rail transit, shield tunnels, as a core structural form of underground engineering, have been widely used in subways, railways, and other fields. Shield tunnels are assembled from multiple prefabricated segments connected by bolts, pins, and other connectors, exhibiting a discontinuous structural characteristic. However, the segment joints, as weak points in the tunnel structure, possess inherent defects in strength and stiffness compared to the segments themselves, resulting in the lining ring exhibiting anisotropic stiffness characteristics in its mechanical behavior. Specifically, the joint area cannot transmit bending moments as effectively as a continuous structure; its mechanical properties are closer to those of a hinged or semi-rigid connection, thus creating a differentiated distribution of bending stiffness in the horizontal and vertical directions.

[0003] Under the influence of ground loads, shield tunnels face initial load conditions where "vertical stress is naturally greater than horizontal stress." According to soil mechanics principles, the vertical earth pressure (σv) under the soil's own weight is significantly higher than the horizontal earth pressure (σh). This unbalanced load interacts with the anisotropic stiffness of the tunnel structure, triggering a mechanical coupling process of "deformation-earth pressure feedback." Initially, the tunnel lining ring undergoes slight compressive deformation under vertical loads. This deformation preferentially occurs in the joint area where the bending stiffness is weakest, manifesting as a "lateral elliptic pattern" (commonly known as the "horizontal egg pattern") with an elongated horizontal diameter and a slightly shortened vertical diameter. As the horizontal diameter continues to expand, the soil on both sides is compressed, generating passive resistance. This resistance further intensifies the horizontal constraint effect, forming a positive feedback loop between deformation and earth pressure. Ultimately, the tunnel structure achieves dynamic equilibrium with the ground load under the new geometry, and the lateral elliptic shape is locked in.

[0004] The aforementioned deformation patterns directly trigger a chain reaction of tunnel structural defects. On the one hand, deformation and opening in the joint area lead to frequent problems such as segment cracking, water leakage, and lining detachment; on the other hand, the deterioration of structural stiffness accelerates material aging, threatening the geometric stability of the track and the safety of train operation. Existing treatment technologies mainly rely on external grouting or internal reinforcement measures. External grouting reinforcement methods typically involve injecting cement or chemical grout into boreholes to fill voids and improve soil bearing capacity. For example, CN112901212A discloses a tunnel defect treatment method that can be repeatedly grouted and is applicable to special grouts, and CN119513982A discloses a tunnel stratum grouting reinforcement design method considering vertical jacking construction loads. Internal tunnel reinforcement methods typically involve constructing secondary concrete lining or special structures inside the tunnel structure to improve tunnel stiffness and prevent further deformation. For example, CN116398180A discloses a rapid reinforcement device and method for shield tunnel structures. However, both external grouting and internal reinforcement are passive protective measures that can only delay tunnel deformation and cannot fundamentally change the tunnel's stress pattern and structural state.

[0005] Therefore, there is an urgent need in this field for a more effective solution to alleviate existing defects in tunnel structures such as cracks, leaks, and lining detachment, and to fundamentally prevent the continued development of the "horizontal egg pattern" in tunnel structures.

[0006] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention provides an external pressure device and construction method for treating the convergence deformation of existing shield tunnels, so as to solve at least some of the above-mentioned technical problems.

[0008] This invention discloses a construction method for an external pressure device to mitigate the convergence deformation of existing shield tunnels, comprising the following steps:

[0009] S1. Determine the spatial location of the tunnel structure to be treated for defects, and construct the first shaft, the second shaft, and the shaft support structure on both sides of the tunnel structure respectively.

[0010] S2. The first and second vertical holes are constructed between the tunnel structure and the first and second vertical shafts by continuous drilling, and the two precast external pressure prestressed plates are respectively sunk along the two vertical holes to both sides of the tunnel structure.

[0011] S3. Based on the geological conditions, the strata are locally reinforced through the grouting ports of the vertical shaft support structure on both sides. Then, the grouting ports are excavated to the precast external pressure prestressed plate to form the corresponding operating port. A telescopic rod is used to cross the strata through the reserved channel on the precast external pressure prestressed plate from one side of the operating port to the corresponding operating port on the other side of the tunnel structure.

[0012] S4. When the telescopic rod crosses the stratum, the traction prestressed strand passes through the operating port, reserved duct and stratum crossing hole on one side until it reaches the operating port on the other side. The two ends of the prestressed strand are connected to the anchoring system respectively. One end is fixed and the other end is connected to the jack of the anchoring system and tensioned, so as to apply external pressure prestress to the tunnel structure through the prefabricated external pressure prestressed plate.

[0013] The construction method of this invention directly intervenes in the mechanical causes of the "lateral ellipticization" defect in shield tunnels by applying external prestress to both sides of the tunnel structure. Based on the interaction mechanism between the anisotropic stiffness characteristics of the tunnel lining ring and the initial condition that the vertical load of the stratum is greater than the horizontal load, this method actively increases the lateral horizontal constraint force of the tunnel, breaking the original equilibrium state of the deformation-soil pressure positive feedback loop. By using precast external pressure prestressed plates to convert concentrated tension into uniformly distributed pressure acting on the tunnel sidewalls, the stress system of the tunnel structure is reconstructed, transforming the structure from an elliptic state to a more balanced circular stress state. This fundamentally inhibits the continuous opening and deformation development at the joints, avoiding the passive delaying effect of traditional grouting or internal lining reinforcement.

[0014] According to a preferred embodiment, a plurality of grouting ports are provided in a through manner on one side of the shaft support structure facing the vertical hole, wherein at least one grouting port is higher than the arch of the tunnel structure, at least one grouting port is lower than the arch bottom of the tunnel structure, and a first grouting port is higher than the arch of the tunnel structure, and a second grouting port is lower than the arch bottom of the tunnel structure.

[0015] Grouting ports, positioned above the arch crown and below the arch base, were installed on the shaft support structure to ensure that the grouting reinforcement area covered the critical load-bearing parts of the tunnel structure. This elevation arrangement allowed the grout to fully fill the gap between the precast external pressure prestressed slab and the tunnel sidewall, forming a continuous force transmission medium and effectively optimizing the transmission path of prestress from the slab to the tunnel structure. By enhancing the grouting intensity in the arch crown and arch base areas, local stress concentration was avoided, ensuring that the external pressure prestress was evenly distributed throughout the entire tunnel height. This improved the uniformity and reliability of deformation correction and prevented localized insufficient load-bearing problems caused by inadequate grouting.

[0016] According to a preferred embodiment, when four grouting ports are provided on the shaft support structure, the third grouting port has the same elevation as the first grouting port, and the fourth grouting port has the same elevation as the second grouting port. The reserved holes embedded in the precast external pressure prestressed slab after sinking correspond one-to-one with the positions of each grouting port.

[0017] When the shaft support structure has four grouting ports with elevations corresponding one-to-one with the pre-reserved ducts of the precast external pressure prestressed slab, precise positioning of the telescopic rods when traversing the strata is ensured. This design avoids difficulties in aligning the pre-reserved ducts due to elevation deviations, ensuring that the prestressed strands can smoothly pass through the ducts and achieve anchorage at both ends. This position matching mechanism significantly improves the efficiency and success rate of the strand threading operation, reduces on-site adjustment time, provides structural protection for the reliable application of external pressure prestress, and reduces the risk of unexpected disturbance to the tunnel structure during construction.

[0018] According to a preferred embodiment, the grouting port on the shaft support structure is a pit with a thickness less than that of the surrounding area. This pit can be chiseled out and the soil between the precast external pressure prestressed slab and the tunnel structure can be grouted and reinforced. After chiseling out, a corresponding operating port is formed.

[0019] Designing the grouting port as a recessed structure with a thickness less than the surrounding area allows for precise control over the size and location of the working opening after excavation. This design reduces the excavation area by limiting the recess, avoiding large-scale soil disturbance, while ensuring the fit between the grouting reinforcement area and the tunnel sidewall. The grouting space created after the working opening is excavated effectively fills the gaps, forming a stable force transmission interface. This prevents ground instability caused by excessive excavation, ensuring efficient transfer of prestressed loads and the safety of the tunnel structure.

[0020] According to a preferred embodiment, the telescopic rod for pulling prestressed strands is configured as a multi-section telescopic rod-shaped structure with hooks at the ends, wherein the length of the telescopic rod in its unextended state is less than the inner diameter of the shaft support structure, and its length in its fully extended state is greater than the distance between the first shaft and the second shaft.

[0021] The telescopic boom is configured as a multi-section, telescopic structure with hooks at the ends, and its length characteristics adapt to the construction needs of shafts with varying spacing. This design allows for flexible operation within the shaft; in its non-extended state, it meets the space constraints of the shaft, while in its fully extended state, it ensures continuity across the geological strata, avoiding interruptions in threading due to insufficient length or construction interference caused by excessive length. This structural optimization significantly improves the stability and efficiency of prestressed strand traction, reduces uncertainties in the construction process, and provides reliable tool support for the rapid deployment of external pressure devices.

[0022] According to a preferred embodiment, the end of the prestressed strand is provided with a circular lifting ring for connection to a hook on a telescopic pole. Preferably, depending on the sand and gravel particle content of the stratum, the prestressed strand can be carbon fiber strand or other high-strength strand with strong corrosion resistance.

[0023] The circular lifting rings at the ends of the prestressed strands, connected to the hooks on the telescopic rods, provide reliable mechanical anchoring points. This design prevents slippage or twisting of the strands during threading, ensuring the continuity of the traction process. The simple yet robust connection mechanism simplifies the strand threading operation, reduces construction difficulty, and avoids damage to the strands due to weak connections during threading, thus guaranteeing the integrity of prestress transfer and the accuracy of subsequent tensioning.

[0024] According to a preferred embodiment, the anchoring system includes an anchor plate, a clamp, and a protective cover. Each component of the anchoring system is made of corrosion-resistant material, and the protective cover is filled with grease or a coating material is applied to the outside of the anchoring system to ensure corrosion resistance. A waterproof gasket is provided between the protective cover and the precast external pressure prestressed plate, and the two are fixed together with expansion bolts. Preferably, the coating material can be, for example, a polyurea coating.

[0025] The anchoring system employs corrosion-resistant components and a grease-filled protective cover, effectively addressing corrosion issues in the tunnel environment. This measure prevents anchoring components from rusting and degrading due to groundwater or soil chemical reactions, thus avoiding prestress loss. The combined design of the protective cover and waterproof gasket further prevents moisture penetration, ensuring the long-term durability of the anchoring system and maintaining prestress stability throughout the tunnel's service life, meeting the technical requirements for long-term safe operation of the structure.

[0026] According to a preferred embodiment, in two anchoring systems connected to the same prestressed strand, the anchoring system at the tensioning end is additionally equipped with a jack compared to the anchoring system at the anchoring end, for tensioning the prestressed strand.

[0027] By configuring jacks for tensioning only on one side of the anchoring system, a single-end operation mode for prestressing application is achieved. This design simplifies the layout of the tensioning equipment, avoids the complexity of simultaneous tensioning at both ends, and ensures precise control of the tension force. The clear division of labor between the fixed end and the tensioning end improves the controllability and efficiency of the tensioning process, reduces equipment commissioning time, makes the prestressing application process more in line with construction operation specifications, and ensures the stability and reliability of the external pressure device.

[0028] According to a preferred embodiment, the precast external pressure prestressed slab is a rigid bending member with a vertical length greater than the outer diameter of the tunnel structure, so that the upper part of the precast external pressure prestressed slab after sinking is higher than the arch of the tunnel structure and the lower part is lower than the arch bottom of the tunnel structure, and a gap is maintained between the slab surface and the sidewall of the tunnel structure for subsequent grouting.

[0029] The precast externally stressed prestressed slabs have a vertical length greater than the tunnel's outer diameter, extending beyond the arch crown at the top and below the arch bottom at the bottom, while retaining grouting gaps. This ensures that the prestressing effect covers the entire tunnel height. This design allows the externally stressed prestressing to act uniformly at both ends of the tunnel's horizontal diameter, effectively suppressing the expansion of elliptic deformation in the arch crown and arch bottom regions. The gaps provide the necessary space for grouting, optimize the uniformity of the force transmission interface, and avoid localized stress concentrations, thereby significantly improving the comprehensiveness of deformation correction and the balance of structural stress.

[0030] The present invention also discloses an external pressure device for treating the convergence deformation of existing shield tunnels, which is obtained by the aforementioned construction method.

[0031] Compared to existing technologies (such as CN119712128A), the innovation of this invention lies not only in the disruptive shift in the technical approach, but also in the profound understanding of the fundamental mechanism of "lateral ellipticization" in shield tunnels and the construction of a targeted solution. This existing technology, based on the concept of "internal reinforcement," indirectly improves deformation by increasing the axial force of the tunnel structure through circumferential prestressing. Its mechanism essentially involves suppressing deformation development by enhancing the structure's own stiffness. However, this approach is limited by its inability to directly eliminate the core contradiction causing "lateral ellipticization"—the imbalance between vertical and horizontal loads. Even with prestressing, its effect is still limited by the inherent contradiction in the load ratio. For example, with an initial vertical load of 200 kPa and a horizontal load of 100 kPa, uniformly increasing the axial force to 100 kPa results in a vertical load of 300 kPa while the horizontal load only increases to 200 kPa, resulting in a load difference of 100 kPa, which fails to achieve a true corrective effect. This invention, based on the innovative concept of "external active correction," directly addresses this fundamental contradiction by designing a technical solution: precast externally stressed prestressed slabs are arranged on both sides of the tunnel, and controllable horizontal pressure is applied to the tunnel sidewalls using external tension, precisely balancing the ratio difference between vertical and horizontal loads. For example, under the same load conditions, this invention can achieve both vertical and horizontal loads of 200 kPa by applying 100 kPa of horizontal prestress, completely eliminating the load imbalance that causes deformation. This "directional load control" not only solves the technical bottleneck that existing technologies cannot overcome, but also achieves a technological leap from "passive defense" to "active correction."

[0032] This invention also represents a groundbreaking innovation in construction feasibility. Existing technologies require the tunnel lining itself as an anchoring point for circumferential prestressing, inevitably involving drilling and anchoring of the tunnel's outer wall, posing a risk of disturbing the existing structure. In contrast, this invention, through the collaborative design of an external shaft and precast external pressure prestressing slabs, constructs a reaction system completely independent of the tunnel structure: tensioning operations are entirely completed within the shaft, and prestress is transferred to the tunnel sidewalls through ground reinforcement, achieving "zero-contact" construction of the tunnel structure. This technical approach not only avoids interference with operating tunnels using traditional methods but also overcomes the technical limitation of applying purely horizontal forces under confined underground space. For example, by using telescopic rods to pull prestressed strands, combined with the force transmission medium formed by grouting reinforcement, this invention successfully solves the problem of a lack of effective support points outside the tunnel. Its technical implementation involves complex coupling across multiple dimensions, including ground mechanical properties, force flow path optimization, and structure-ground synergy, far exceeding the capabilities of simply superimposing common knowledge.

[0033] Furthermore, the technical solution of this invention possesses significant scalability and universality. The existing circumferential prestressing technology is mainly applicable to circular tunnels and has limitations on the degree of deformation, as excessive radial force may exacerbate structural instability. In contrast, this invention, based on the principle of load proportion control, can be widely applied to tunnels of various cross-sectional shapes (such as rectangular and elliptical tunnels) and can effectively address complex conditions where deformation exceeds limits. This technological paradigm breakthrough not only provides a new approach to the treatment of shield tunnel defects but also extends to underground engineering fields such as utility tunnels and station retaining structures, demonstrating the dual innovative height of this invention in terms of technological originality and engineering application value. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of step S1 of the construction method of the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention;

[0035] Figure 2 This is a schematic diagram of step S2 of the construction method of the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention;

[0036] Figure 3 This is a schematic diagram of step S3 of the construction method of the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention;

[0037] Figure 4 This is a schematic diagram of step S4 of the construction method for the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention.

[0038] Figure 5 This is a schematic diagram of step S4 completion stage of the construction method of the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention;

[0039] Figure 6 This is a plan view of the completion stage of step S4 in the construction method of the external pressure device for treating the convergence deformation of existing shield tunnels provided by the present invention.

[0040] Figure 7 This is a schematic diagram of the prestressing of the precast external pressure prestressed slab provided by the present invention through the operating port;

[0041] Figure 8 This is a schematic diagram of the tensioning end and the anchoring end of the anchoring system provided by the present invention;

[0042] Figure 9 This is a software simulation diagram of the external pressure device and construction method provided by the present invention;

[0043] Figure 10 This is a comparison diagram of the axial force of the shield tunnel before and after treatment by the external pressure device provided by this invention;

[0044] Figure 11 This is a comparison diagram of the bending moment of the shield tunnel before and after treatment by the external pressure device provided by this invention;

[0045] Figure 12 This is a comparison diagram of the horizontal displacement of the shield tunnel before and after treatment by the external pressure device provided by this invention;

[0046] Figure 13 This is a comparison diagram of the radial displacement of the shield tunnel before and after treatment by the external pressure device provided by the present invention.

[0047] List of reference numerals

[0048] 100: Tunnel structure; 101: First vertical shaft; 102: Second vertical shaft; 103: Shaft support structure; 104: First grouting port; 105: Second grouting port; 108: Bottom reinforcement structure; 200: First vertical hole; 201: Second vertical hole; 202: Telescopic rod; 203: Prestressed strand; 204: Hook; 205: Circular lifting ring; 300: Precast external pressure prestressed plate; 301: Reserved duct; 302: First operating port; 303: Second operating port; 304: Third operating port; 305: Fourth operating port; 400: Anchoring system; 401: Jack; 402: Anchor plate; 403: Wedge; 404: Protective cover; 405: Waterproof washer; 406: Expansion bolt. Detailed Implementation

[0049] The following is a detailed explanation with reference to the accompanying drawings.

[0050] Example 1

[0051] like Figures 1-8As shown, this invention discloses a construction method for an external pressure device to mitigate the convergence deformation of existing shield tunnels. This construction method may include the following steps:

[0052] S1. Determine the spatial location of the tunnel structure 100 to be treated for defects, and construct the first vertical shaft 101, the second vertical shaft 102, and the shaft support structure 103 on both sides of the tunnel structure 100.

[0053] Preferably, the tunnel structure 100 should be selected from sections where the tunnel has undergone significant deformation, sections where the geological conditions are poor but no significant deformation has occurred, or sections where construction is planned to take place soon.

[0054] Preferably, the dimensions of the first shaft 101 and the second shaft 102 should not be too large, just large enough to accommodate personnel activities and the tensioning of the prestressed strands 203.

[0055] S2. The first vertical hole 200 and the second vertical hole 201 are constructed between the tunnel structure 100 and the first vertical shaft 101 and the second vertical shaft 102 by continuous drilling. The two precast external pressure prestressed plates 300 are respectively lowered into the tunnel structure 100 along the two vertical holes to both sides of the tunnel structure 100.

[0056] Preferably, when drilling continuously, the first vertical hole 200 and the second vertical hole 201 can be excavated using mud slurry wall protection to avoid hole collapse. The size of the vertical hole can accommodate the precast external pressure prestressed plate 300. At the same time, a distance can be left between the vertical hole and the tunnel structure 100 to facilitate subsequent grouting to reinforce the stratum.

[0057] Preferably, the lower and upper positions of the precast external pressure prestressed slab 300 after sinking exceed the arch top and arch bottom of the tunnel structure 100 by a certain distance (i.e., the upper part of the precast external pressure prestressed slab 300 is higher than the arch top of the tunnel structure 100, and the lower part of the precast external pressure prestressed slab 300 is lower than the arch bottom of the tunnel structure 100). This distance should not be greater than 1 / 3 of the outer diameter of the tunnel structure 100 and should not be less than 0.5m. The closer the exceedance distance, the better the reinforcement effect. However, too close a distance may also cause disturbance to the tunnel structure 100 when the telescopic rod 202 crosses the stratum.

[0058] Preferably, during the prefabrication of the precast external pressure prestressed slab 300, the designer can determine the reinforcement scheme on the tension side according to the magnitude of the applied prestress. Since the prestressing in this invention is post-tensioned, the embedded ducts can be made of corrugated metal pipes. Anchor plates 402 and spiral reinforcements can be installed at the ends of the embedded ducts during the prefabrication of the precast external pressure prestressed slab 300. The precast external pressure prestressed slab 300 is a rigid bending member, precast in the factory. The planar shape of the precast external pressure prestressed slab 300 is rectangular, and the length of the rectangle (i.e., the longitudinal length of the precast external pressure prestressed slab 300) is greater than the outer diameter of the tunnel structure 100.

[0059] Furthermore, the precast externally stressed prestressed slab 300 can be made of high-strength reinforced concrete with a bidirectional steel mesh inside. The concrete strength grade is not lower than C40 to ensure that the slab has sufficient strength and stiffness when subjected to tension. The reserved ducts 301 of the precast externally stressed prestressed slab 300 can be pre-embedded in the slab before casting. The inner diameter of the reserved ducts 301 is larger than the nominal diameter of the prestressing strands 203 to ensure smooth tensioning. The axis of the reserved ducts 301 is perpendicular to the plane of the precast externally stressed prestressed slab 300, and an anchor plate 402 is pre-embedded at its outlet end.

[0060] After the precast external pressure prestressed slab 300 is lowered along the vertical hole, a gap is maintained between its surface and the sidewall of the tunnel structure 100 for subsequent grouting. The planar projected area of ​​the precast external pressure prestressed slab 300 is much larger than the area of ​​the operating port, which enables it to distribute the prestress applied by the jack 401 into a uniformly distributed load, effectively acting on the tunnel structure 100.

[0061] Preferably, multiple grouting ports can be provided on the side of the shaft support structure 103 facing the vertical hole, wherein at least one grouting port is higher than the arch of the tunnel structure 100, and at least one grouting port is lower than the arch bottom of the tunnel structure 100. Figure 2 In this configuration, the first grouting port 104 is higher than the arch of the tunnel structure 100, and the second grouting port 105 is lower than the arch bottom of the tunnel structure 100. More preferably, four grouting ports can be provided on the side of the shaft support structure 103 facing the vertical opening, wherein the third grouting port has the same elevation as the first grouting port 104, and the fourth grouting port has the same elevation as the second grouting port 105. Therefore, in... Figure 2 The third grouting port is blocked by the first grouting port 104, and the fourth grouting port is blocked by the second grouting port 105.

[0062] Furthermore, for the case where the shaft support structure 103 has four grouting ports, the reserved ducts 301 can be pre-embedded in the four corner areas of the precast external pressure prestressed plate 300 before pouring.

[0063] S3. Based on the geological conditions, the strata are locally reinforced through the grouting ports of the vertical shaft support structures 103 on both sides. Then, the grouting ports are excavated to the precast external pressure prestressed plate 300 to form a corresponding operating port. The telescopic rod 202 is used to cross the strata from one side of the operating port through the reserved channel 301 on the precast external pressure prestressed plate 300 to the corresponding operating port on the other side of the tunnel structure 100.

[0064] Preferably, local reinforcement of the strata can be achieved based on the geological conditions. This can be done by adopting differentiated grouting schemes according to the strength and stability of the soil between the precast external pressure prestressed slab 300 and the tunnel structure 100, and by using the grouting ports of the vertical shaft support structures 103 on both sides to locally reinforce the strata. Preferably, when encountering soft cohesive soil or loose sand, it indicates that the strata have poor self-stabilizing ability and are easily deformed. In this case, comprehensive reinforcement should be carried out, preferably using cement-based grout or chemical grout, starting from the grouting port with a lower grouting pressure and gradually filling upwards, aiming to significantly improve the overall strength of the soil. When encountering dense sand or stiff plastic cohesive soil, it indicates that the strata themselves already have a certain bearing and force transmission capacity. In this case, contact grouting can be carried out, mainly to fill the gaps generated during construction, ensuring a dense contact between the prestressed slab and the soil, and the grouting pressure and grout volume can be reduced accordingly.

[0065] Preferably, the first grouting port 104, the second grouting port 105, the third grouting port and / or the fourth grouting port are connected to the shaft support structure 103 of a single shaft and correspond to the reserved channel 301 on the precast external pressure prestressed plate 300 after sinking, so that the stratum between the precast external pressure prestressed plate 300 and the tunnel structure 100 can be grouted and reinforced.

[0066] Preferably, the grouting reinforcement area can cover most of the area of ​​the precast external pressure prestressed slab 300 to ensure that the force can be evenly transferred to the tunnel structure 100 through the precast external pressure prestressed slab 300 when prestressing is applied. The grouting range should not extend beyond the upper and lower range of the precast external pressure prestressed slab 300 to prevent increasing the difficulty of the telescopic rod 202 crossing the stratum.

[0067] Preferably, each grouting port can be excavated to form a corresponding operating port, and the operating port formed by the excavation of the grouting port must meet the requirements of prestressed construction. When the shaft support structure 103 has four grouting ports, the first grouting port 104 is excavated to form the first operating port 302, the second grouting port 105 is excavated to form the second operating port 303, the third grouting port is excavated to form the third operating port 304, and the fourth grouting port is excavated to form the fourth operating port 305. Further, the distribution positions of the first operating port 302, the second operating port 303, the third operating port 304, and the fourth operating port 305 on the same precast external pressure prestressed slab 300 are as follows: Figure 7 As shown, while Figure 3 In the middle, the third operating port 304 is blocked by the first operating port 302, and the fourth operating port 305 is blocked by the second operating port 303.

[0068] Preferably, based on the above operations, each of the two shafts can have its own first operating port 302, second operating port 303, third operating port 304, and fourth operating port 305. Further, the telescopic rod 202 can pull or push the prestressed strand 203 from the first operating port 302 of one shaft to the first operating port 302 of the other shaft; similarly, the other operating ports can pull or push the prestressed strand 203 in a one-to-one correspondence. Any other rod with the same function can also replace the telescopic rod 202.

[0069] S4. When the telescopic rod 202 crosses the stratum, the traction prestressed strand 203 passes through one side operating port, the reserved duct 301 and the stratum crossing hole until it reaches the other side operating port. The two ends of the prestressed strand 203 are respectively connected to the anchoring system 400. One end is fixed and the other end is connected to the jack 401 of the anchoring system 400 and tensioned, so as to apply external pressure prestress to the tunnel structure 100 through the prefabricated external pressure prestressed plate 300.

[0070] Preferably, the hook 204 at the end of the telescopic rod 202 can be connected to the circular lifting ring 205 at the end of the prestressed strand 203, and the prestressed strand 203 can be delivered to the target operating port by traction.

[0071] Preferably, before threading the prestressed strands 203, the operating opening and its surrounding area of ​​the precast external pressure prestressed slab 300 can be cleaned to facilitate construction, and at the same time, it helps to identify and deal with problems that may cause corrosion of the prestressed strands 203 or the anchoring system 400.

[0072] Preferably, the shield tunnel is reinforced by precast external pressure prestressed plate 300. The purpose is to improve the deformation mode of the tunnel structure 100 and resist further deformation during the subsequent operation of the tunnel. The applied prestress value is related to the tunnel condition, and the factors considered include the design parameters of the tunnel structure 100, whether deformation has occurred, the geological conditions, and whether there are other nearby constructions.

[0073] Preferably, after the precast external pressure prestressed plate 300 is prestressed, it can generate displacement in the direction of the tunnel structure 100. At this time, grouting can be performed between the precast external pressure prestressed plate 300 and the shaft through the operating port to enhance the stability of the structural system.

[0074] Preferably, in addition to the steps described above, the method of the present invention may further include:

[0075] Depending on the specific circumstances, either the first vertical shaft 101 or the second vertical shaft 102 can be selected as the inspection shaft. The above steps can be repeated until the arrangement of external pressure devices and the application of prestressing are completed for all the areas to be treated.

[0076] Preferably, the reinforcement can be evaluated through numerical simulation to determine the applicability of the design parameters of this method. For example, based on the previous design and experimental foundation of the prestressed segment structure, the following reference design can be obtained: each operating port uses 12 prestressed strands 203 with a diameter of 15.2 mm and a tensile strength of 3000 MPa, and the tension stress is controlled at 2400 MPa. The spacing between each group of precast external pressure prestressed slabs 300 is 6 m.

[0077] Preferably, the first shaft 101 and the second shaft 102 can be excavated simultaneously. The shafts are rectangular, with smaller rather than larger dimensions, and their distance from the tunnel structure 100 should be larger rather than smaller, all to minimize disturbance to the tunnel during shaft excavation. The bottom elevation of the shaft is lower than the bottom elevation of the precast external pressure prestressed slab 300, and the bottom can be reinforced with concrete using a shaft bottom reinforcement structure 108. The shaft depth is greater than the bottom burial depth of the tunnel structure 100, and the inner diameter of the shaft is designed to allow for the movement and operation of the jacks 401 by construction personnel.

[0078] Preferably, the longitudinal length of the precast external pressure prestressed plate 300 is greater than the outer diameter of the tunnel structure 100, and it is arranged symmetrically up and down along the transverse axis of the tunnel structure 100. A set of external pressure devices includes two precast external pressure prestressed plates 300, and a single set of precast external pressure prestressed plates 300 is arranged symmetrically left and right along the longitudinal axis of the tunnel structure 100.

[0079] Preferably, when the reserved holes 301 on the precast external pressure prestressed plate 300 are precast in the factory and grouting ports (i.e., the first grouting port 104, the second grouting port 105, the third grouting port and the fourth grouting port) are set on the vertical shaft support structure 103 of a single vertical shaft, the grouting ports and the reserved holes 301 are kept at the same elevation. Improper setting will make it difficult for the subsequent telescopic rod 202 to pass through the stratum to reach the grouting port on the other side.

[0080] Preferably, the dimensions of the operating openings (i.e., the first operating opening 302, the second operating opening 303, the third operating opening 304, and the fourth operating opening 305) can be adjusted according to whether they serve as the anchoring end or tensioning end of the prestressed strand 203. During excavation, a one-time excavation followed by grouting reinforcement of the outer soil can be adopted, or a method of first excavating a small opening for grouting, and then performing secondary excavation and secondary grouting can be adopted.

[0081] Preferably, the length of the telescopic rod 202 in its unextended state is less than the inner diameter of the shaft support structure 103, and the length of the telescopic rod 202 in its fully extended state is greater than the distance between the first shaft 101 and the second shaft 102. Furthermore, for construction efficiency, construction can be carried out simultaneously at the four reserved holes 301 of the precast external pressure prestressed slab 300.

[0082] Preferably, the end of the prestressed strand 203 can be configured as a circular lifting ring 205, which can be connected to the hook 204 of the telescopic rod 202. Considering that groundwater will cause varying degrees of corrosion, carbon fiber steel strand can be selected as the tensioning prestressed strand 203, which has advantages such as good corrosion resistance, wear resistance, lightweight and high strength, and can meet the durability requirements of 100% prestressed tunnel structure.

[0083] Preferably, Figure 8 A schematic diagram of the anchoring system 400 is shown. The anchoring system 400 includes an anchor plate 402, a clamping plate 403, and a protective cover 404. A jack 401 is also provided at the tensioning end. The anchoring system 400 can be used for tensioning and anchoring the prestressed strand 203.

[0084] Preferably, all components of the anchoring system 400 can be made of corrosion-resistant materials. After tensioning, a corrosion-resistant protective cover 404 can be used to cover the other components of the anchoring system 400, and the protective cover 404 can be filled with grease. A waterproof gasket 405 can be provided between the protective cover 404 and the precast external pressure prestressed plate 300 and fixed with expansion bolts 406.

[0085] Preferably, during factory prefabrication, the precast external pressure prestressed slab 300 can be reinforced according to the magnitude of the prestress applied by the prestressing strands 203 to ensure that the cracks generated in the tensile side concrete are less than the design requirements. Corrugated pipes or other types of pipes can be installed in the reserved ducts 301 on the precast external pressure prestressed slab 300, and tensioning can be performed using bonded or unbonded prestressing strands 203.

[0086] According to a preferred embodiment, the present invention also discloses an external pressure device for treating the convergence deformation of existing shield tunnels, which can be obtained by the construction method described above.

[0087] Example 2

[0088] This embodiment is a further improvement on embodiment 1, and repeated content will not be described again.

[0089] This embodiment analyzes the impact of the external pressure device of the present invention on the deformation of the tunnel structure 100 during vertical shaft excavation. The specific analysis process is as follows:

[0090] (1) Model parameter settings

[0091] Figure 9This is a schematic diagram of a tunnel reinforced under external pressure treatment, established using a geological structure model. Tunnel structure 100 has an outer diameter of 6.6m, segment thickness of 0.35m, ring width of 1.2m (13 rings in total), and a top burial depth of 15m. Two sets of precast external pressure prestressed slabs 300 are installed, spaced 6m apart. Each precast external pressure prestressed slab 300 measures 1m × 10m × 2m, with a minimum clearance of 0.35m from tunnel structure 100. Tunnel structure 100 is made of C50 concrete, and the precast external pressure prestressed slabs 300 are made of C40 concrete. The geological stratum is fine silt, and a modified Mohr-Coulomb constitutive model is used, with a soil unit weight of 20.3 kN / m³. 3 Poisson's ratio 0.3, triaxial secant stiffness 7000 kN / m 2 Unloading elastic modulus 35000 kN / m 2 Carbon fiber prestressed strand 203 is used, with 12 strands per bundle, each strand having a diameter of 15.2 mm and a tensile strength of 3000 MPa. The constitutive model is an elastic model of a non-compression truss, with a tension control stress of 2400 MPa.

[0092] (2) Simulation step sequence

[0093] For the external pressure device treatment scheme, the simulation steps are as follows: ① Establish a soil model and perform ground stress balance; ② Excavate the tunnel and construct the tunnel structure 100; ③ Establish a prestressed strand 203 model and apply prestress.

[0094] (3) Simulation results

[0095] Before and after the treatment, the axial force and bending moment of the tunnel structure 100 are as follows: Figure 10 and Figure 11 As shown in the figure, before and after the treatment, the axial forces at the crown of tunnel structure 100 were 588.71 kN and 997.92 kN, respectively, and the axial forces at the waist were 1352.84 kN and 1617.92 kN, respectively, representing an increase of 19.6% to 66.1%. The bending moments at the crown were 294.71 kN·m and 173.83 kN·m, respectively, and the bending moments at the waist were 275 kN·m and 269.1 kN·m, respectively, meaning the bending moment at the crown decreased by 41.1%, while the bending moment at the waist decreased slightly. Overall, the internal forces of tunnel structure 100 were significantly improved after the treatment, and the increased axial forces also significantly improved the ultimate bearing capacity of the existing tunnel.

[0096] Before and after the treatment, the deformation of the tunnel structure was as follows: Figure 12 and Figure 13 As shown in the figure, after treatment, the maximum vertical convergence of the tunnel decreased from 15.442 mm to 10.579 mm, a reduction of 31.5%, and the horizontal convergence decreased from 14.424 mm to 10.806 mm, a reduction of 25.1%. Therefore, the tunnel deformation was significantly reduced after treatment, and the external pressure device was effective.

[0097] Based on the calculation and analysis results, it can be seen that after the construction of the external pressure device, the axial force of the tunnel structure 100 can be greatly increased and the tunnel deformation can be reduced, making the structure more rationally stressed. At the same time, it can significantly improve the tunnel deformation disease and reduce the later operation disease.

[0098] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; phrases such as "preferred" or "according to a preferred embodiment" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept. Throughout the text, the feature introduced by "preferred" is only an optional mode and should not be construed as mandatory. Therefore, the applicant reserves the right to abandon or delete relevant preferred features at any time.

Claims

1. A construction method for an external pressure device to control the convergence deformation of existing shield tunnels, characterized in that, It includes the following steps: S1. Determine the spatial location of the tunnel structure (100) to be treated for defects, and construct the first vertical shaft (101), the second vertical shaft (102), and the shaft support structure (103) on both sides of the tunnel structure (100). S2. The first vertical hole (200) and the second vertical hole (201) are constructed between the tunnel structure (100) and the first vertical shaft (101) and the second vertical shaft (102) by continuous drilling. The two precast external pressure prestressed slabs (300) are respectively lowered into the two vertical holes to both sides of the tunnel structure (100). S3. Based on the geological conditions, the strata are locally reinforced through the grouting ports of the vertical shaft support structure (103) on both sides. Then, the grouting ports are excavated to the precast external pressure prestressed plate (300) to form a corresponding operating port. The telescopic rod (202) is used to cross the strata from one side of the operating port through the reserved channel (301) on the precast external pressure prestressed plate (300) to the corresponding operating port on the other side of the tunnel structure (100). S4. When the telescopic rod (202) crosses the stratum, the traction prestressed strand (203) passes through the operating port on one side, the reserved duct (301) and the stratum crossing hole until it reaches the operating port on the other side. The two ends of the prestressed strand (203) are connected to the anchoring system (400) respectively. One end is fixed and the other end is connected to the jack (401) of the anchoring system (400) and tensioned, so as to apply external pressure prestress to the tunnel structure (100) through the prefabricated external pressure prestressed plate (300).

2. The construction method according to claim 1, characterized in that, Multiple grouting ports are provided in a through manner on one side of the vertical shaft support structure (103) facing the vertical hole. At least one grouting port is higher than the arch of the tunnel structure (100), and at least one grouting port is lower than the arch bottom of the tunnel structure (100). The first grouting port (104) is higher than the arch of the tunnel structure (100), and the second grouting port (105) is lower than the arch bottom of the tunnel structure (100).

3. The construction method according to claim 2, characterized in that, When four grouting ports are opened on the vertical shaft support structure (103), the third grouting port has the same elevation as the first grouting port (104), and the fourth grouting port has the same elevation as the second grouting port (105). The reserved ducts (301) embedded in the precast external pressure prestressed plate (300) after sinking correspond one-to-one with the positions of each grouting port.

4. The construction method according to claim 1, characterized in that, The grouting port on the shaft support structure (103) is a pit with a thickness less than that of the surrounding area. This pit can be chiseled out and the soil between the precast external pressure prestressed slab (300) and the tunnel structure (100) can be grouted and reinforced. After chiseling out, a corresponding operating port is formed.

5. The construction method according to claim 1, characterized in that, The telescopic rod (202) used for traction of prestressed strand (203) is configured as a multi-section telescopic rod structure with hooks (204) at the ends, wherein the length of the telescopic rod (202) in its unextended state is less than the inner diameter of the shaft support structure (103), and its length in its fully extended state is greater than the distance between the first shaft (101) and the second shaft (102).

6. The construction method according to claim 5, characterized in that, The end of the prestressed strand (203) is provided with a circular lifting ring (205) for connection with the hook (204) of the telescopic rod (202).

7. The construction method according to claim 1, characterized in that, The anchoring system (400) includes an anchor plate (402), a wedge (403), and a protective cover (404). Each component of the anchoring system (400) is made of corrosion-resistant material, and the protective cover (404) is filled with grease or coated with a coating material to ensure corrosion resistance. A waterproof gasket (405) is provided between the protective cover (404) and the precast external pressure prestressed plate (300) and fixed by expansion bolts (406).

8. The construction method according to claim 1, characterized in that, Of the two anchoring systems (400) connected to the same prestressed strand (203), the anchoring system (400) at the tensioning end is additionally equipped with a jack (401) for tensioning the prestressed strand (203) compared to the anchoring system (400) at the anchoring end.

9. The construction method according to claim 1, characterized in that, The precast external pressure prestressed slab (300) is a rigid bending member with a vertical length greater than the outer diameter of the tunnel structure (100). This ensures that the upper part of the precast external pressure prestressed slab (300) after sinking is higher than the arch of the tunnel structure (100) and the lower part is lower than the arch bottom of the tunnel structure (100). Furthermore, a gap is maintained between the slab surface and the sidewall of the tunnel structure (100) for subsequent grouting.

10. An external pressure device for controlling the convergence deformation of existing shield tunnels, characterized in that, It is obtained by the construction method described in any one of claims 1 to 9.

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