Method for treating shield tunnel diseases through trenchless perturbation external prestressing

Abstract

The invention relates to a method for treating shield tunnel diseases through trenchless perturbation external prestressing, and belongs to the field of tunnel structures.The method comprises the steps that the spatial position of a tunnel structure is determined, and a first vertical shaft, a second vertical shaft and a vertical shaft supporting structure are constructed; constructing a first vertical hole, and pushing the prestressed stranded wire to the bottom of the first vertical hole; the stratum is locally reinforced, then a first operation opening and a second operation opening are formed through excavation, a telescopic rod is adopted to transversely penetrate through the stratum from the second operation opening to the first operation opening, and the prestress stranded wire is pulled back to the second operation opening; the stratum is locally reinforced and excavated to form a third operation opening, then a second vertical hole is formed, and the prestress stranded wire is pulled to the third operation opening from the second operation opening; the stratum is locally reinforced and excavated to form a tensioning operation opening, a telescopic rod is adopted to transversely penetrate through the stratum from the tensioning operation opening to a third operation opening, and the prestress stranded wire is pulled back to the tensioning operation opening; and the two ends of the prestress stranded wire penetrate into the anchoring system and are tensioned, so that external prestress is applied to the tunnel structure.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel structures, and in particular to a method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing. Background Art

[0002] According to the subway monitoring data over the years, a large number of tunnels in operation have entered the stage of service with defects, and various defects frequently occur, such as tunnel convergence, deformation, cracks, water leakage, lining shedding, etc. Therefore, it is of great practical significance and necessity to treat shield tunnel defects.

[0003] The main reasons for shield tunnel diseases are as follows: First, the shield tunnel structure may have problems such as insufficient integrity and weak deformation resistance. In particular, the segment joints are the weakest link. Under complex water and soil load environments, joint deformation, cracking, leakage, etc. are prone to occur, leading to large deformation and instability. Second, shield tunnels are usually located in strata of different properties. When encountering train vibrations in the tunnel or nearby construction, adverse geological effects may occur. With the change of the bearing capacity of the surrounding soil, the shield tunnel may experience longitudinal uneven settlement and deformation and other diseases. Third, during the construction of the shield tunnel, if the construction technology is not standardized and the process is not strictly implemented, it may cause voids and cavities around the tunnel structure, which will lead to a series of problems such as leakage, cracking, frost damage, and corrosion.

[0004] In order to solve the tunnel structure disease, the current common treatment methods mainly include grouting reinforcement on the outside of the tunnel structure or pasting high-strength materials inside the tunnel. For example, CN112901212A discloses a tunnel disease treatment method that can be repeatedly grouted and can be applied to special slurries. The treatment method is as follows: Step 1, in the tunnel section prone to water leakage and before and after the tunnel, between the initial support and the waterproof layer of the tunnel, multiple groups of repeatable grouting component groups are arranged along the longitudinal interval of the tunnel. Step 2, the two adjacent connecting pipes of the two adjacent overflow tubes near the tunnel ground are connected to a horizontal pipe, which horizontally penetrates the waterproof layer and the secondary lining and extends into the tunnel. The upper connecting pipe is used as the discharge end, and the lower connecting pipe is used as the grouting end, which is used to connect to the grouting machine; Step 3, the discharge end is closed, the grouting machine is started, and the slurry is injected from the grouting end, transported through the annular slurry delivery channel, and each overflow tube is filled in turn. However, the effect of external grouting reinforcement is often unsatisfactory and requires long-term maintenance; and although internal gluing of high-strength materials can improve the strength of the tunnel structure, after the secondary deformation of the tunnel structure, these materials may separate from the original structure, affecting the reinforcement effect.

[0005] Therefore, this field urgently needs a treatment method that can more effectively alleviate the existing large deformation, cracking, water leakage and other diseases of the tunnel structure, and fundamentally avoid various diseases in the subsequent operation of the tunnel structure, so as to improve the durability and safety of the tunnel structure and reduce the subsequent operation and maintenance costs.

[0006] In addition, 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 the present invention, but due to space limitations, not all details and contents are listed in detail. However, this does not mean that the present invention does not have the characteristics of these prior arts. On the contrary, the present invention already has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art to the background technology. Summary of the invention

[0007] In view of the deficiencies of the prior art, the present invention provides a method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing, so as to permanently improve the overall stiffness and deformation resistance of the tunnel structure, alleviate the existing large deformation, cracking, water leakage and other diseases of the tunnel structure, and fundamentally avoid various diseases in the subsequent operation of the tunnel structure, improve the durability and safety of the tunnel structure, and reduce the subsequent operation and maintenance costs. Under the condition of basically not disturbing the original tunnel structure, the present invention applies external prestressing to the tunnel structure through the vertical shafts and vertical holes on both sides of the tunnel structure, which can permanently improve the overall stiffness and deformation resistance of the tunnel structure, alleviate the existing large deformation, cracking, water leakage and other diseases of the tunnel structure, and fundamentally avoid various diseases in the subsequent operation of the tunnel structure, improve the durability and safety of the tunnel structure, and reduce the subsequent operation and maintenance costs.

[0008] The present invention discloses a method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing, which comprises the following steps:

[0009] S1. Determine the spatial position of the tunnel structure to be treated for damage, and construct the first vertical shaft, the second vertical shaft and the vertical shaft support structure on both sides of the tunnel structure;

[0010] S2, constructing a first vertical hole between the tunnel structure and the first vertical shaft, and pushing the prestressed stranded wire to the bottom of the first vertical hole;

[0011] S3, locally reinforce the stratum through the first and second cable-through openings at the bottom of the shaft support structure on both sides according to the stratum conditions, then excavate to form the first and second operating openings, use a telescopic rod to cross the stratum from the second operating opening to the first operating opening, and pull the prestressed stranded wire back to the second operating opening;

[0012] S4, locally reinforce the stratum according to the stratum conditions through the third cable-through opening and excavate to form a third operating opening, then construct a second vertical hole between the tunnel structure and the second vertical shaft, and pull the prestressed strand from the second operating opening to the third operating opening;

[0013] S5, locally reinforce the stratum according to the stratum conditions through the tensioning opening and excavate to form a tensioning operation opening, use a telescopic rod to cross the stratum from the tensioning operation opening to the third operation opening, and pull the prestressed strand back to the tensioning operation opening;

[0014] S6. Insert both ends of the prestressed strand into the anchoring system, fix one end and connect the other end to the jack and tension it, so as to apply external prestress to the tunnel structure.

[0015] According to a preferred embodiment, the first shaft and the second shaft are excavated simultaneously and the shaft support structure is constructed in time. The bottom of the shaft is reinforced with concrete. The depth of the shaft is greater than the burial depth of the bottom of the tunnel structure. The inner diameter is designed to meet the needs of construction personnel to move and operate the jack.

[0016] According to a preferred embodiment, the first vertical shaft and the second vertical shaft are respectively provided with a first cable insertion opening and a second cable insertion opening at the same buried depth below the bottom of the tunnel structure, and a third cable insertion opening and a tensioning opening are respectively provided at the same buried depth above the top of the tunnel structure.

[0017] According to a preferred embodiment, the first cable passage opening, the second cable passage opening, the third cable passage opening and the tensioning opening are pits with a thickness less than that of the surrounding area, and the size of the tensioning opening is larger than the above-mentioned cable passage openings, wherein the above-mentioned pits can be chiseled out and the outer soil can be reinforced and excavated to form the first operating opening, the second operating opening, the third operating opening and the tensioning operating opening whose size is larger than the above-mentioned operating openings.

[0018] According to a preferred embodiment, the telescopic rod used for pulling the prestressed stranded wire is a multi-section telescopic round rod with a hook at the end, wherein the length of the telescopic rod in an un-extended state is less than the inner diameter of the shaft support structure, and the length in a fully extended state is greater than the distance between the first shaft and the second shaft.

[0019] According to a preferred embodiment, the end of the prestressed strand is a circular ring connected to the hook of the telescopic rod, wherein, based on the different sand and gravel particle content of the stratum, the prestressed strand should preferably be made of carbon fiber strand or other high-strength strand with strong corrosion resistance.

[0020] According to a preferred embodiment, the anchoring system includes an anchor plate, a clip, a jack and a protective cover. The anchor plate includes an arc-shaped base, a tensioning surface, a first channel cluster and a second channel cluster. The arc radius of the arc-shaped base is consistent with the outer diameter of the tunnel structure. The channel cluster is a variable diameter circular inclined hole that passes through the anchor plate, including a channel entrance located below the tensioning surface and a channel exit located above the tensioning surface. The slope of the channel cluster is designed to ensure that the prestressed strands do not deflect at the channel entrance, and the tensioning surface is approximately perpendicular to the channel cluster.

[0021] According to a preferred embodiment, one end of the prestressed stranded wire is inserted into the channel entrance of the first channel cluster, passes out from the channel exit, and is fixed at the channel exit by a clamp; the other end of the prestressed stranded wire is inserted into the channel entrance of the second channel cluster, passes out from the channel exit, and is fixed at the channel exit by a clamp after being tensioned by a jack.

[0022] According to a preferred embodiment, the components of the anchoring system are made of anti-corrosion treated materials, and the anchoring system is wrapped with a protective cover. The protective cover is filled with grease or the anchoring system is coated with polyurea coating and other materials to ensure corrosion resistance requirements. A waterproof gasket is arranged between the protective cover and the outer surface of the tunnel structure, and is fixed with expansion bolts.

[0023] According to a preferred embodiment, the first vertical shaft is transformed into an inspection well after processing, the bottom of the inspection well is located below the tensioning mouth, the bottom is a concrete-cast inspection well bottom, and the opening is sealed with a manhole cover.

[0024] The present invention not only provides annular prestress for the tunnel structure by applying an external prestressing system on the outside of the tunnel structure, but also forms a radial force pointing to the center of the tunnel structure and a tangential force tangent to the outer surface of the tunnel structure. The radial force helps to reduce the ellipticity of the tunnel structure, while the tangential force adds additional axial force to the tunnel structure. The two work together to effectively reduce the deformation of the tunnel structure and reduce the opening of the joints, thereby alleviating existing defects such as large deformation, cracking and water leakage. The external prestressing system enables the tunnel structure to form a self-stabilizing structural system, significantly enhances its overall stiffness and deformation resistance, and improves the ultimate bearing capacity. These improved mechanical properties enable the tunnel structure to more effectively cope with various external load changes that may be encountered during operation, thereby effectively preventing the tunnel structure from further large deformation, cracking or water leakage, while reducing the cost of subsequent operation and maintenance. In addition, the present invention can select carbon fiber strands as prestressed materials, which have good corrosion resistance and mechanical strength; each component of the anchoring system is treated with anti-corrosion and wrapped by a protective cover, and the interior of the protective cover is filled with grease or other anti-corrosion measures are taken to further enhance the durability of the system. The above measures ensure that the entire external prestressed system can meet the design service life requirements of the tunnel structure. Finally, the present invention only needs to excavate a small-sized first vertical shaft and a second vertical shaft on both sides of the tunnel structure, and set vertical holes and necessary operating ports and tensioning ports therebetween for the application of external prestress. The first vertical shaft and the second vertical shaft are constructed symmetrically and synchronously, which can minimize the impact of external prestressed construction on the existing tunnel structure, ensure the micro-disturbance characteristics during the construction process, and ensure the safety and stability of the original structure. In summary, the present invention provides an efficient, reliable and durable technical solution, which brings significant technical effects and economic benefits to the treatment of shield tunnel diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of step S1 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0026] Figure 2 It is a schematic diagram of step S2 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0027] Figure 3 It is a schematic diagram of step S3 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0028] Figure 4 It is a schematic diagram of step S4 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0029] Figure 5 It is a schematic diagram of step S5 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0030] Figure 6 It is a schematic diagram of step S6 of the method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing provided by the present invention;

[0031] Figure 7 It is a schematic plan view of step S6 of the method for treating shield tunnel diseases by trenchless micro-disturbance external prestressing provided by the present invention;

[0032] Figure 8 It is a schematic plan view of step S7 of the method for treating shield tunnel diseases by trenchless micro-disturbance external prestressing provided by the present invention;

[0033] Fig. 9 It is a structural schematic diagram of the anchoring system provided by the present invention;

[0034] Fig.10 It is a structural schematic diagram of the anchor pad provided by the present invention;

[0035] Fig.11 It is a schematic diagram of the tensioning surface of the anchor pad provided by the present invention;

[0036] Fig.12 It is a schematic diagram of the mechanism of action of the external prestressing force on the tunnel structure provided by the present invention;

[0037] Fig.13 It is a schematic diagram of the effective prestress of the prestressed strands after considering the prestress loss terms σ1 and σ2 under different arrangement schemes of the anchoring system provided by the present invention;

[0038] Fig.14It is a schematic diagram of software simulation of shaft excavation under the external prestressing treatment solution provided by the present invention;

[0039] Fig.15 It is a schematic diagram of the horizontal deformation of the tunnel structure before and after the shaft excavation under the external prestressing treatment solution provided by the present invention;

[0040] Fig.16 It is a comparison diagram of the axial force distribution of the external prestressing treatment scheme and the common scheme under the unloading condition provided by the present invention;

[0041] Fig.17 It is a comparison diagram of the bending moment distribution of the external prestressing treatment scheme and the common scheme under the unloading condition provided by the present invention;

[0042] Fig.18 It is a comparison diagram of the overall deformation of the external prestressing treatment scheme under unloading conditions provided by the present invention and the common scheme.

[0043] Reference numerals list

[0044] 100: tunnel structure; 101: first vertical shaft; 102: second vertical shaft; 103: vertical shaft support structure; 104: first cable hole; 105: second cable hole; 106: third cable hole; 107: tensioning hole; 108: shaft bottom reinforcement structure; 200: first vertical hole; 201: second vertical hole; 202: prestressed stranded wire; 203: lifting ring; 204: telescopic rod; 205: hook; 301: first operation hole; 302: second operation hole; 303: third operation port; 304: tensioning operation port; 400: anchoring system; 401: anchor pad; 402: arc base; 403: tensioning surface; 404: first channel cluster; 405: second channel cluster; 406: channel entrance; 407: channel exit; 408: clip; 409: jack; 500: protective cover; 501: waterproof gasket; 502: expansion bolt; 600: inspection well; 601: bottom of inspection well; 602: well cover. DETAILED DESCRIPTION

[0045] The following is a detailed description with reference to the accompanying drawings.

[0046] like Figure 1 to Figure 8 The present invention discloses a method for treating shield tunnel defects by non-excavation micro-disturbance external prestressing, which may include the following steps:

[0047] S1. Determine the spatial position of the tunnel structure 100 to be treated for defects, and construct a first vertical shaft 101, a second vertical shaft 102 and a vertical shaft support structure 103 on both sides of the tunnel structure 100.

[0048] Preferably, the spatial position of the tunnel structure 100 includes parameters such as tunnel coordinates, burial depth, diameter, and surrounding pipelines. Considering that the tunnel structure 100 may produce structural settlement and convergence deformation during construction and operation, the actual position of the tunnel structure 100 needs to take into account the impact of the deformation.

[0049] S2. Construct a first vertical hole 200 between the tunnel structure 100 and the first vertical shaft 101 , and push the prestressed strands 202 to the bottom of the first vertical hole 200 .

[0050] Preferably, the first vertical hole 200 can be drilled after the construction of the shaft structure is completed. It is located between the tunnel structure 100 and the shaft, and as close to the cable insertion port or tensioning port 107 of the shaft as possible. This is because the first vertical hole 200 needs to be located in the operation port formed later, which is convenient for the prestressed stranded wire 202 to be surrounded at the operation port. Preferably, the first vertical hole 200 can be excavated in the form of mud wall protection to avoid hole collapse. Further, a telescopic rod 204 or a rod with a hook 205 at any end whose length exceeds the depth of the shaft can be used to push the prestressed stranded wire 202 to the bottom of the first vertical hole 200. During the pushing process, the rod or prestressed stranded wire 202 is prevented from scraping the hole wall of the first vertical hole 200 to cause hole collapse. Preferably, the purpose of the construction of the shaft and the vertical hole is to facilitate the realization of the prestressed stranded wire 202 surrounding the tunnel structure 100, which is an optional auxiliary measure or structure of the present invention. The present invention can also use other methods that can realize the prestressed stranded wire 202 surrounding the tunnel structure 100.

[0051] S3. Partially reinforce the stratum according to the stratum conditions through the first cable insertion opening 104 and the second cable insertion opening 105 at the bottom of the vertical shaft support structure 103 on both sides, and then excavate to form the first operating opening 301 and the second operating opening 302, use the telescopic rod 204 to cross the stratum from the second operating opening 302 to the first operating opening 301, and pull the prestressed strand 202 back to the second operating opening 302.

[0052] Preferably, the stratum grouting reinforcement area should be larger than the size of the operating opening to ensure that the stratum is stable after the operating opening is excavated.

[0053] Preferably, for strata with good permeability and abundant groundwater, water glass materials can be used for grouting reinforcement or weak freezing can be used for local treatment of the strata, which can stabilize the soil and waterproof it. At the same time, the strength of the soil after reinforcement is very low, which is convenient for operation and does not affect the cutting of the soil during the subsequent tensioning of the prestressed strands 202. For strata with low permeability or good stability, no reinforcement treatment is required.

[0054] S4. The stratum is locally reinforced and excavated through the third cable passage 106 according to the stratum conditions to form a third operating opening 303, and then a second vertical hole 201 is constructed between the tunnel structure 100 and the second vertical shaft 102, and the prestressed strand 202 is pulled from the second operating opening 302 to the third operating opening 303.

[0055] S5. Partially reinforce the stratum according to the stratum conditions and excavate to form a tensioning operation opening 304 through the tensioning opening 107 , use the telescopic rod 204 to cross the stratum from the tensioning operation opening 304 to the third operation opening 303 , and pull the prestressed strand 202 back to the tensioning operation opening 304 .

[0056] S6. Insert both ends of the prestressed strand 202 into the anchoring system 400 , wherein one end is fixed and the other end is connected to the jack 409 and tensioned, so as to apply external prestress to the tunnel structure 100 .

[0057] Preferably, in step S6, before the prestressed strand 202 is inserted into the anchoring system 400, the outer surface of the tunnel structure 100 at the third operating port 303 may be cleaned. The cleaning work not only removes loose materials, dirt or other impurities that may exist on the surface of the tunnel structure 100, ensures good contact between the prestressed strand 202 and the tunnel structure 100 and the bonding effect during subsequent mortar filling, but also enables the tension force to be effectively transferred from the prestressed strand 202 to the tunnel structure 100, thereby improving the reinforcement effect. At the same time, the clean surface makes it easier for construction personnel to check the status of the tunnel structure 100 and confirm that there are no cracks or other defects, thereby ensuring the quality of construction, and helps to find and deal with problems that may cause corrosion of the prestressed strand 202 or the anchoring system 400, such as wet areas or chemical erosion sources, to ensure the long-term stability and durability of the system. In addition, a clean and barrier-free working surface also makes it more convenient to install the anchoring system 400, and can be adjusted as needed to ensure that the prestressed strand 202 is correctly in place.

[0058] Preferably, the purpose of applying external prestress to the tunnel structure 100 is to adjust the existing deformation of the tunnel structure 100 and resist its re-deformation in subsequent operation. The value of the applied prestress is related to the current conditions of the tunnel structure 100 and the conditions that may arise in the future, including the design parameters of the tunnel structure 100, the existing deformation characteristics, the formation conditions, and the adjacent construction to be carried out.

[0059] Preferably, the method of the present invention may further include, in addition to the above steps:

[0060] S7. Anti-corrosion and anti-rust treatment is performed on the anchoring system 400. The first vertical hole 200, the second vertical hole 201 and the second vertical shaft 102 are filled with mortar. The bottom of the first vertical shaft 101 is filled to below the tensioning opening 107, and the top is covered to form an inspection shaft 600.

[0061] Preferably, the above steps can be repeated until the application of external prestressing at multiple locations within the length of the tunnel structure 100 to be treated for defects is completed. Preferably, numerical simulation can be used to verify whether the assumed conditions for the application of external prestressing at multiple locations are reasonable. For example, based on the design and test basis of the previous prestressed segment structure, the following reference design can be obtained: 4 to 6 prestressed strands 202 with a diameter of 15.2 mm and a tensile strength of 3000 MPa are used, the tensioning force is controlled to be 2400 MPa, and the spacing between the prestressed strands 202 is about 2 m.

[0062] Preferably, the multiple external prestressed anchor systems 400 arranged longitudinally along the tunnel structure 100 can be arranged symmetrically along the two sides of the tunnel structure 100, that is, the first bundle of anchor systems 400 is arranged on the left side of the tunnel structure 100 and tensioned, and the second bundle of anchor systems 400 is arranged on the right side of the tunnel structure 100 and tensioned, and the cycle is repeated in sequence. Such an arrangement is based on the consideration that the prestressed strands 202 will cause prestress loss during the tensioning process due to factors such as anchor deformation, contraction of the prestressed strands 202, friction between the prestressed strands 202 and the duct, and creep of concrete, and as the distance from the anchor system 400 increases, this prestress loss will gradually increase, resulting in uneven force on the tunnel structure 100. By arranging the anchor systems 400 symmetrically on both sides of the tunnel structure 100, the maximum prestress loss parts of the adjacent external prestressed systems can be staggered, which can not only improve the uniformity of the overall prestress of the tunnel structure 100, but also make the force of the tunnel structure 100 more reasonable and stable. The above arrangement helps to ensure the prestressing effect of each anchor point, reduce the potential structural risk caused by excessive local prestressing loss, and optimize the mechanical properties of the entire tunnel structure 100. In addition, the symmetrical arrangement is also conducive to the operation balance during the construction process, reducing the possible structural deviation problem caused by unilateral loading.

[0063] Preferably, the first vertical shaft 101 and the second vertical shaft 102 should be excavated at the same time. The vertical shaft is circular, the outer diameter should be small rather than large, and the net distance from the tunnel structure 100 should be large rather than small, so as to avoid uneven load distribution on both sides of the tunnel structure 100 due to the difference in the excavation depth of the vertical shaft, and reduce the disturbance of the tunnel structure 100 caused by the unloading effect caused by the vertical shaft construction. At the same time, the vertical shaft support structure 103 is constructed in time during the vertical shaft excavation process to avoid deformation of the vertical shaft itself. The outer diameter of the vertical shaft can be limited to about 1.2m~1.5m, and the net distance from the tunnel structure 100 can be limited to more than 0.5m. The vertical shaft support structure 103 can be a prefabricated reinforced concrete structure, and the joints are waterproofed. After the vertical shaft excavation is completed, the bottom of the vertical shaft can be constructed with concrete to form a bottom reinforcement structure 108, and waterproof treatment is performed. After the vertical shaft is constructed, the depth of the bottom reinforcement structure 108 should be greater than the bottom burial depth of the tunnel structure 100, so as to facilitate the cable threading construction of the prestressed stranded wire 202 at the bottom. Since the control equipment such as the tensioning machine required for prestressing is placed on the ground outside the vertical shaft, the inner diameter of the vertical shaft only needs to be sufficient for the construction personnel to move and operate the jack 409.

[0064] Preferably, the first vertical shaft 101 and the second vertical shaft 102 are respectively provided with a first cable insertion opening 104 and a second cable insertion opening 105 at the same buried depth below the bottom of the tunnel structure 100, and a third cable insertion opening 106 and a tensioning opening 107 are respectively provided at the same buried depth above the top of the tunnel structure 100. When the vertical shaft support structure 103 adopts a prefabricated structure, the buried depth of the tunnel should be considered in the prefabricated structure preparation stage, so as to set the cable insertion openings (the first cable insertion opening 104, the second cable insertion opening 105, and the third cable insertion opening 106) and the tensioning opening 107. If the buried depth of the cable insertion opening and the tensioning opening 107 is improperly set, the subsequent telescopic rod 204 will not be able to reach the corresponding operation opening after crossing the stratum, resulting in the inability to pull the prestressed stranded wire 202.

[0065] Preferably, the cable-through opening and the tensioning opening 107 have different functions, wherein the cable-through opening is mainly used to serve the telescopic rod 204 to pull the prestressed strand 202, and is relatively small in size; the tensioning opening 107, in addition to having the function of the cable-through opening, also needs to serve the tensioning of the prestressed strand 202, and is relatively large in size. In addition, both the cable-through opening and the tensioning opening 107 need to be chiseled out during construction, and the structural thickness of this area should be thinner than that of other areas. Therefore, the first cable-through opening 104, the second cable-through opening 105, and the third cable-through opening 106 are designed as small-sized pits with a thickness smaller than that of the surrounding areas, and the tensioning opening 107 is designed as a large-sized pit with a thickness smaller than that of the surrounding areas. The first cable-through opening 104, the second cable-through opening 105, and the third cable-through opening 106 can be chiseled out at one time, and the outer soil can be reinforced by grouting, and then excavated to form the first operating opening 301, the second operating opening 302, and the third operating opening 303 of small size. The tensioning opening 107 is relatively large in size, and it is easy to cause soil instability if it is removed at one time. Small holes can be drilled first to reinforce the soil with grouting, and then all holes can be removed to construct a large-sized tensioning operation opening 304. Preferably, the main purpose of designing the operation opening as a small size is to assist the prestressed strand 202 to surround the tunnel structure 100. This area needs to connect the hook 205 of the telescopic rod 204 with the ring 203 of the prestressed strand 202, so that the telescopic rod 204 can pull the prestressed strand 202. The size of the small-sized operation opening can be, for example, 15cm×15cm×15cm. Preferably, the main purpose of designing the tensioning operation opening 304 as a large size is to serve the fixation and tensioning of the prestressed strand 202, so it is necessary to meet the space requirements for the installation of the anchoring system 400 and the construction of the jack 409. The size of the large-sized tensioning operation opening 304 can be, for example, 50cm×50cm×50cm.

[0066] Preferably, the inner diameter of the shaft support structure 103 is much smaller than the distance between the first shaft 101 and the second shaft 102, so the traction of the prestressed strand 202 needs to use a telescopic rod 204 with a telescopic function and a hook 205 at the end. If the same telescopic rod 204 is used for the horizontal and vertical traction of the prestressed strand 202, the length of the telescopic rod 204 in the un-expanded state is less than the inner diameter of the shaft support structure 103, and the length in the fully-expanded state is greater than the depth of the first shaft 101 and the second shaft 102. If the telescopic rod 204 is only used for the horizontal traction of the prestressed strand 202, the length of the telescopic rod 204 in the fully-expanded state is greater than the distance between the first shaft 101 and the second shaft 102, and the vertical traction of the prestressed strand 202 can use any rod with a hook 205 at the end whose length exceeds the depth of the shaft.

[0067] Preferably, the end of the prestressed strand 202 is a circular eye 203, which can be connected to the hook 205 of the telescopic rod 204. Considering that the extracorporeal prestressed system is in a groundwater environment and is corrosive, ordinary prestressed strands 202 are prone to rust in this environment for a long time, which in turn affects the durability and long-term safety of the extracorporeal prestressed system. At the same time, the prestressed strand 202 is in the soil. In order to ensure the uniform distribution of the annular prestress as much as possible during tensioning, the friction between the prestressed strand 202 and the tunnel structure 100 and the soil can be reduced. Carbon fiber strands have the advantages of good corrosion resistance, wear resistance, light weight and high strength, and can be used in nuclear industry, seawater and other environments, and can meet the durability requirements of the extracorporeal prestressed tunnel structure 100.

[0068] Preferably, Figures 9 to 11 The structural schematic diagram of the anchoring system 400 and the structural schematic diagram of the anchor pad 401 are shown. The anchoring system 400 includes the anchor pad 401, the clip 408, the jack 409 and the protective cover 500. The anchoring system 400 is used for tensioning and fixing (i.e., anchoring) the prestressed strand 202. Due to the limited operating space, the extracorporeal prestressing system can adopt a one-end fixed and one-end tensioning scheme. The anchoring system 400 is not fixed to the tunnel structure 100 and can move freely during the tensioning process.

[0069] Preferably, the anchor plate 401 comprises an arc base 402, a tensioning surface 403, a first hole cluster 404 and a second hole cluster 405. The contact portion between the anchor plate 401 and the tunnel structure 100 may adopt an arc base 402, and the arc radius of the arc base 402 is consistent with the outer diameter of the tunnel structure 100, that is, the entire surface of the arc base 402 may be in close contact with the outer surface of the tunnel structure 100, which, on the one hand, facilitates the movement of the arc base 402 during the tensioning process, and on the other hand, increases the contact area between the anchor plate 401 and the tunnel structure 100, thereby avoiding damage to the tunnel structure 100 due to excessive stress on the tunnel structure 100 by the anchor plate 401 after tensioning. The first hole cluster 404 and the second hole cluster 405 may be arranged in a rectangular or annular array, and are variable diameter circular inclined holes penetrating the anchor plate 401, including a small diameter hole inlet 406 located below the tensioning surface 403 and a large diameter hole outlet 407 located above the tensioning surface 403. Since the clip 408 is in the shape of a truncated cone with a circular through hole in the middle, the prestressed strand 202 can pass through the circular channel of the clip 408. The clip 408 is installed at the channel outlet 407. The variable diameter circular inclined hole design is conducive to the clip 408 clamping the prestressed strand 202 during tensioning, and the greater the tensioning force, the greater the clamping force. In addition, since the channel entrance 406 is higher than the outer surface of the tunnel structure 100, the prestressed strand 202 is obliquely inserted into the channel entrance 406, so the slope of the channel cluster should be designed so that the prestressed strand 202 does not deflect at the channel entrance 406, and the tensioning surface 403 should also be kept as vertical as possible with the channel cluster to reduce the loss of prestress during tensioning.

[0070] Preferably, the extracorporeal prestressing system can adopt a one-end fixed and one-end tensioning scheme, where one end of the prestressed strand 202 passes through the channel entrance 406 of the first channel cluster 404, passes through the channel exit 407, and is fixed at the channel exit 407 by a clip 408. The other end of the prestressed strand 202 passes through the channel entrance 406 of the second channel cluster 405, passes through the channel exit 407, and is fixed by a clip 408 after being tensioned by a jack 409. To facilitate the operation of the jack 409, the jack 409 should face one side of the shaft (the first shaft 101 or the second shaft 102). During prestressing, the prestressed strand 202 cuts the soil under the tension of the jack 409 and continuously tightens toward the outer wall of the tunnel structure 100, and finally adheres closely to the outer wall.

[0071] Preferably, all components of the anchor system 400 can be made of anti-corrosion treated materials. After the tensioning is completed, the entire anchor system 400 can be wrapped with a corrosion-resistant protective cover 500, wherein the protective cover 500 can be filled with grease. A waterproof gasket 501 is provided between the protective cover 500 and the outer surface of the tunnel structure 100, and can be fixed to the outer surface of the tunnel structure 100 with expansion bolts 502.

[0072] Preferably, the environment in which the external prestressing system is located is harsh and requires regular inspection and maintenance. Except for the first vertical shaft 101, the other excavated vertical shafts, vertical holes, operating ports, etc. need to be closed and processed in time after the external prestressing is completed. The first vertical shaft 101 can be processed to become a maintenance well 600. Since the depth of the first vertical shaft 101 is large, it is not conducive to workers to detect the prestress loss and structural corrosion of the anchoring system 400 at the tensioning mouth 107. When constructing the maintenance well 600, it is necessary to fill the bottom of the first vertical shaft 101 to a depth of the area below the tensioning mouth 107, and use concrete to construct the bottom 601 of the maintenance well. At the same time, the opening of the maintenance well 600 can be prepared with a steel-concrete structure to prepare a manhole cover 602. The strength of the manhole cover 602 should meet the driving safety. If necessary, the opening can be waterproof and sealed.

[0073] According to a preferred embodiment, the mechanism of action of the in vitro prestressing system constructed based on the method of the present invention on the tunnel structure 100 is as follows:

[0074] (1) Calculation of external prestress loss

[0075] During the tensioning and anchoring process, the prestressed strand 202 will generate prestress loss due to factors such as anchor deformation, strand shrinkage, concrete elastic deformation, concrete creep, etc. Among them, the prestress loss (σ1) caused by anchor deformation and prestressed strand 202 shrinkage and the prestress loss (σ2) caused by the friction between the prestressed strand 202 and the outer wall of the tunnel structure 100 account for a large proportion of all prestress losses. Therefore, the present invention mainly considers the prestress loss caused by σ1 and σ2, and the calculation formula is as follows:

[0076] ,

[0077] ,

[0078] In the formula, σ con is the tension control stress value of the prestressed strand 202, and the friction loss of the anchor should be deducted; μ is the friction coefficient between the prestressed steel bar and the outer wall of the tunnel structure 100; k is the friction coefficient considering the misalignment of the segment assembly; r is half of the outer diameter of the segment; θ is the angle from the tensioning end to the tangent of the pipeline part of the calculated section curve; θ0 is the reverse friction influence angle of the prestressed strand 202, which can be calculated by the following formula:

[0079] ,

[0080] Where a is the deformation of the anchor at the tensioning end and the shrinkage value of the prestressed strand 202; E s is the elastic modulus of the prestressed strand 202.

[0081] The effective prestress of the prestressed strand 202 (σ e ) is the tension control stress value of the prestressed strand 202 minus various prestress losses, and the calculation expression is as follows:

[0082] .

[0083] (2) Mechanism of action of external prestress on tunnel structure 100

[0084] like Fig.12 As shown, after the prestressed strands 202 are tensioned, the prestress will act on the tunnel structure 100, and a radial force (σ n ) and the tangential force tangent to the outer surface of the tunnel structure 100 (σ t ). The microelement segment of the prestressed stranded wire 202 and the tunnel structure 100 is selected for force analysis, and the equilibrium equation of the prestressed stranded wire 202 can be expressed as:

[0085] ,

[0086] Where dσ eis the effective prestress increment of the prestressed strand 202; dθ is the wrap angle of the micro-segment of the prestressed strand 202; t is the converted width of the action surface of the prestressed strand 202, which can be taken as the width of the anchor groove; θ is the angle from the tensioning end to the tangent of the pipe part of the calculated section curve.

[0087] Since dθ is very small, the following conclusions can be derived:

[0088] ,

[0089] .

[0090] According to the above conclusions, the radial force (σ n ) and tangential force (σ t ) is expressed as:

[0091] ,

[0092] .

[0093] (3) Effect of external prestressing on the internal force enhancement of tunnel structure 100

[0094] The tangential force (σ t ) is actually the axial force provided to the tunnel structure 100. Compared with the ordinary tunnel structure, the axial force of the tunnel structure 100 under this scheme can be divided into two parts, one of which is the axial force generated by the external water and soil load, and the other is the axial force formed by the external prestressing. That is, the axial force borne by the tunnel structure 100 under this scheme will be greater than that of the ordinary tunnel structure.

[0095] Fig.13 is the effective prestress of the prestressed strand 202 after considering the prestress loss terms σ1 and σ2 under different arrangement schemes of the anchor system 400, wherein the prestressed strand 202 uses 6 bundles, each bundle is composed of multiple strands of prestressed carbon fiber strands, the diameter of a single strand is 15.2 mm, and the tensile strength is 3000 MPa. The top of the tunnel structure 100 is 0°, and the angle increases clockwise. The right anchor position of the tunnel structure 100 is 60°, and the left anchor position is 300°. σ con is 2400MPa, μ is 0.2rad -1 , k is 0.0015m -1 , a is 1 mm, E sis 150GPa. When the anchoring systems 400 are all arranged on the right side of the tunnel structure 100 and when the anchoring systems 400 are all arranged on the left side of the tunnel structure 100, the effective prestress of a single prestressed strand 202 is between 1101 and 1892kN, and the difference between the maximum and minimum effective prestress is 790kN; when the anchoring systems 400 are arranged at intervals on the right and left sides of the tunnel structure 100, the average effective prestress of the prestressed strands 202 on the left and right sides is between 1357 and 1700kN, and the difference between the maximum and minimum effective prestress is 342kN, and the difference in prestress is only 43% of that when arranged on one side. When the anchoring systems 400 are all arranged on the right or left side of the tunnel structure 100, the effective prestress is asymmetrically distributed along the two sides of the tunnel structure 100, and the tunnel structure 100 is subjected to a large eccentric load. When the anchoring systems 400 are arranged at intervals on the right and left sides of the tunnel structure 100, the effective prestress is symmetrically distributed along both sides of the tunnel structure 100, and the tunnel structure 100 is subjected to more uniform and reasonable stress.

[0096] According to a preferred embodiment, the influence of shaft excavation on the deformation of the tunnel structure 100 under the external prestressing treatment scheme of the present invention is analyzed, and the specific analysis process is as follows:

[0097] (1) Model parameter setting

[0098] Fig.14 The software simulation diagram of the shaft excavation under the extracorporeal prestressing treatment scheme established with the stratum structure model is shown. The outer diameter of the tunnel structure 100 is 6.0m, the thickness is 0.3m, the ring width is 1.5m, there are 5 rings in total, and the top is buried at a depth of 15m. The outer diameter of the shaft structures on both sides is 1.2m, the inner diameter is 0.8m, the burial depth is 23m, the spacing is 2m, and the net distance from the tunnel structure 100 is 1.8m. Both the shaft and the tunnel structure 100 are C50 concrete. The stratum is fine sand, and the modified Mohr-Coulomb model is used. The elastic modulus of the soil layer is 24.14MPa, the Poisson's ratio is 0.3, and the bulk density is 20.3kN / m 3 , triaxial test secant stiffness 5000kN / m 2 , unloading elastic modulus is 50MPa, and the final expansion angle is 10°.

[0099] (2) Simulation sequence

[0100] a. Establish soil model and balance ground stress; b. Excavate tunnel and construct tunnel structure 100; c. Excavate shaft and construct support structure.

[0101] (3) Simulation results

[0102] The horizontal deformation of the tunnel structure 100 before and after shaft excavation under the external prestressing treatment scheme is shown in Fig.15As shown in the figure, the maximum horizontal deformation of the tunnel structure 100 before and after the shaft excavation is 6.71 mm and 6.74 mm respectively, and the deformation increment is only 0.03 mm, i.e. 0.4%. This shows that the shaft excavation has almost no effect on the deformation of the tunnel structure 100. In other words, the external prestressing construction is a micro-disturbance to the tunnel structure 100.

[0103] According to another preferred embodiment, the in vitro prestressing treatment method (shield tunnel disease) of the present invention is compared with the common method, and the specific comparison process is as follows:

[0104] (1) Model parameter setting

[0105] Abaqus software was used to establish a three-dimensional model of the tunnel structure 100, and the in vitro prestressing treatment scheme of the present invention and the ordinary scheme were used to treat shield tunnel diseases under unloading conditions on both sides. The outer diameter of the tunnel structure 100 is 6.0m, the thickness is 0.3m, the ring width is 1.5m, there is 1 ring in total, and the material is C50 concrete. The in vitro prestressing treatment scheme is to set a bundle of 6 15.2mm prestressed carbon fiber strands outside the tunnel structure 100, with a tensile strength of 3000MPa, a truss-linear elastic model, and a tension control stress value of 2400MPa. The ordinary scheme does not set in vitro prestressing. The load structure model is selected to apply the peripheral load of the tunnel structure 100, in which the vertical pressure and bottom reaction force are 220kPa, and the lateral pressure is 80kPa.

[0106] (2) Simulation sequence

[0107] For the external prestressing treatment scheme, the simulation steps are: a. Establish a model of the tunnel structure 100 and balance the ground stress; b. Apply peripheral loads to the tunnel structure 100; c. Establish a prestressed strand model and apply prestress to the prestressed strand; d. Reduce the pressure on both sides of the tunnel structure 100 to 40 kPa. Preferably, for the common scheme, the simulation step c can be deleted.

[0108] (3) Simulation results

[0109] The internal forces of the external prestressing treatment scheme and the ordinary scheme under unloading conditions are as follows: Fig.16 and Fig.17 As shown. The axial forces per linear meter of the external prestressing treatment scheme and the ordinary scheme are 2005.5kN and 925kN respectively. Compared with the ordinary scheme, the axial force of the external prestressing treatment scheme is increased by 117%. The bending moments of the external prestressing treatment scheme and the ordinary scheme are 343kN·m and 323kN·m respectively. Compared with the ordinary scheme, the bending moment of the external prestressing treatment scheme is slightly increased, but overall, the internal force of the existing tunnel is significantly improved, and the ultimate bearing capacity level of the existing tunnel is greatly improved.

[0110] The overall deformation increment of the external prestressing treatment scheme and the ordinary scheme under unloading conditions is shown in Fig.18 The horizontal convergence deformation increments of the external prestressing treatment scheme and the ordinary scheme were 26mm and 46.4mm respectively, and the horizontal convergence was reduced by 44%; the vertical convergence deformation increments of the external prestressing treatment scheme and the traditional method were 24mm and 35mm respectively, and the vertical convergence was reduced by 31%. Therefore, compared with the ordinary scheme, the deformation of the external prestressing treatment scheme is reduced.

[0111] Based on the simulation comparison results, it can be seen that by applying external prestress, the axial force of the tunnel structure 100 can be greatly increased and the deformation can be reduced, making the structural force more reasonable, which can effectively improve the tunnel deformation disease and reduce the deformation hazards in the later operation.

[0112] It should be noted that the above-mentioned specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention specification and its drawings are illustrative and do not constitute a limitation of the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The present invention specification contains multiple inventive concepts, such as "preferably" or "according to a preferred embodiment", which means that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application based on each inventive concept. Throughout the text, the features guided by "preferably" are only an optional method and should not be understood as a must-have setting. Therefore, the applicant reserves the right to abandon or delete the relevant preferred features at any time.

Claims

1. A method for treating shield tunnel defects by non-excavation micro-disturbance external prestressing, characterized in that: It includes the following steps: S1. Determine the spatial position of a tunnel structure (100) to be treated for damage, and construct a first vertical shaft (101), a second vertical shaft (102), and a vertical shaft support structure (103) on both sides of the tunnel structure (100); S2, constructing a first vertical hole (200) between the tunnel structure (100) and the first vertical shaft (101), and pushing the prestressed stranded wire (202) to the bottom of the first vertical hole (200); S3, locally reinforcing the stratum through the first cable insertion opening (104) and the second cable insertion opening (105) at the bottom of the vertical shaft support structure (103) on both sides according to the stratum conditions, and then excavating to form a first operating opening (301) and a second operating opening (302), using a telescopic rod (204) to cross the stratum from the second operating opening (302) to the first operating opening (301), and pulling the prestressed stranded wire (202) back to the second operating opening (302); S4, locally reinforcing the stratum according to the stratum conditions through the third cable insertion opening (106) and excavating to form a third operating opening (303), then constructing a second vertical hole (201) between the tunnel structure (100) and the second vertical shaft (102), and pulling the prestressed strand (202) from the second operating opening (302) to the third operating opening (303); S5, locally reinforcing the stratum according to the stratum conditions through the tensioning opening (107) and excavating to form a tensioning operation opening (304), using a telescopic rod (204) to cross the stratum from the tensioning operation opening (304) to the third operation opening (303), and pulling the prestressed strand (202) back to the tensioning operation opening (304); S6. Insert both ends of the prestressed strand (202) into the anchoring system (400), wherein one end is fixed and the other end is connected to the jack (409) and tensioned, so as to apply external prestress to the tunnel structure (100).

2. The method according to claim 1, characterized in that The first vertical shaft (101) and the second vertical shaft (102) are excavated simultaneously and the vertical shaft support structure (103) is constructed in a timely manner. The bottom of the vertical shaft is constructed with concrete to form a shaft bottom reinforcement structure (108). The depth of the vertical shaft is greater than the burial depth of the bottom of the tunnel structure (100), and the inner diameter is designed to meet the needs of construction personnel to move and operate the jack (409).

3. The method according to claim 1 or 2, characterized in that: The first vertical shaft (101) and the second vertical shaft (102) are respectively provided with a first cable insertion opening (104) and a second cable insertion opening (105) at the same buried depth below the bottom of the tunnel structure (100), and a third cable insertion opening (106) and a tensioning opening (107) are respectively provided at the same buried depth above the top of the tunnel structure (100).

4. The method according to claim 3, characterized in that The first cable insertion opening (104), the second cable insertion opening (105), the third cable insertion opening (106) and the tensioning opening (107) are pits with a thickness less than that of the surrounding area, and the size of the tensioning opening (107) is larger than the above-mentioned cable insertion openings, wherein the above-mentioned pits can be chiseled out and the outer soil can be reinforced by grouting and excavation to form a first operating opening (301), a second operating opening (302), a third operating opening (303) and a tensioning operating opening (304) with a size larger than the above-mentioned operating openings.

5. The method according to claim 2, characterized in that: The telescopic rod (204) used for pulling the prestressed stranded wire (202) is a multi-section telescopic round rod with a hook (205) at the end, wherein the length of the telescopic rod (204) in an un-telescopic state is less than the inner diameter of the shaft support structure (103), and the length in a fully telescopic state is greater than the distance between the first shaft (101) and the second shaft (102).

6. The method according to claim 5, characterized in that The end of the prestressed strand (202) is a circular hanging ring (203) connected to a hook (205) of the telescopic rod (204).

7. The method according to claim 1, characterized in that The anchoring system (400) comprises an anchor plate (401), a clip (408), a jack (409) and a protective cover (500); the anchor plate (401) comprises an arc-shaped base (402), a tensioning surface (403), a first channel cluster (404) and a second channel cluster (405); the arc radius of the arc-shaped base (402) is consistent with the outer diameter of the tunnel structure (100); the channel cluster is a variable diameter circular inclined hole penetrating the anchor plate (401), comprising a channel entrance (406) located below the tensioning surface (403) and a channel exit (407) located above the tensioning surface (403).

8. The method according to claim 7, characterized in that One end of the prestressed stranded wire (202) passes through the hole entrance (406) of the first hole cluster (404), passes through the hole exit (407), and is fixed at the hole exit (407) by a clamp (408); the other end of the prestressed stranded wire (202) passes through the hole entrance (406) of the second hole cluster (405), passes through the hole exit (407), is tensioned by a jack (409), and is fixed at the hole exit (407) by a clamp (408).

9. The method according to claim 7, characterized in that: The components of the anchoring system (400) are made of materials that have been treated for corrosion, and a protective cover (500) is used to wrap the anchoring system (400). Grease is filled in the protective cover (500) or a coating is applied to the anchoring system (400) to ensure corrosion resistance requirements. A waterproof gasket (501) is provided between the protective cover (500) and the outer surface of the tunnel structure (100), and expansion bolts (502) are used to fix them.

10. The method according to claim 1, characterized in that The first vertical shaft (101) is transformed into a maintenance shaft (600) after being processed. The bottom of the maintenance shaft (600) is located below the tensioning opening (107). The bottom is a maintenance shaft bottom (601) cast in concrete, and the opening is sealed with a manhole cover (602).

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