A method for treating shield tunnel diseases by non-excavation micro-disturbance external prestressing

Abstract

The present invention relates to a method for treating shield tunnel diseases by non-excavation micro-disturbance external prestress, belonging to the field of tunnel structures, and comprising: determining the spatial position of the tunnel structure, and constructing a first shaft, a second shaft and a shaft support structure; constructing a first vertical hole, and pushing a prestressed strand to the bottom of the first vertical hole; locally reinforcing the formation, and then excavating to form a first operation port and a second operation port, using a telescopic rod to cross the formation from the second operation port to the first operation port, and pulling the prestressed strand back to the second operation port; locally reinforcing the formation and excavating to form a third operation port, then constructing a second vertical hole, and pulling the prestressed strand from the second operation port to the third operation port; locally reinforcing the formation and excavating to form a tensioning operation port, using a telescopic rod to cross the formation from the tensioning operation port to the third operation port, and pulling the prestressed strand back to the tensioning operation port; passing the two ends of the prestressed strand through an anchoring system and tensioning to apply external prestress to the tunnel structure.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel structures, and particularly to a method for treating shield tunnel diseases by non-excavation micro-disturbance external prestress. Background Technique

[0002] According to years of subway monitoring data, a large number of operating tunnels have entered the stage of serving with diseases, and various diseases occur frequently, such as tunnel convergence, deformation, cracks, water leakage, lining peeling off, etc. Therefore, treating shield tunnel diseases has important practical significance and necessity.

[0003] The main reasons for the occurrence of shield tunnel diseases are as follows: First, there may be problems with the integrity of the shield tunnel structure and its weak anti-deformation ability. Especially, the segment joints, as the weakest links, are prone to joint deformation, cracking, leakage, etc. under complex soil and water load environments, resulting in diseases such as large deformation and instability. Second, shield tunnels are usually located in strata with different properties. When encountering train vibrations in the tunnel or adjacent construction nearby, it may trigger adverse geological effects. With the change of the bearing capacity of the surrounding soil, longitudinal uneven settlement and deformation and other diseases may occur in the shield tunnel. Third, during the construction period of the shield tunnel, if the construction technology is not standardized and the procedures are not strictly implemented, it may lead to the occurrence of voids and cavities around the tunnel structure, resulting in a series of problems such as water leakage, cracking, frost damage, and corrosion.

[0004] To solve the diseases of the tunnel structure, 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 is applicable to special slurries. The treatment method is as follows: Step 1, in the sections of the tunnel where water leakage diseases are likely to occur and before and after them, between the primary support and the waterproof layer of the tunnel, a plurality of groups of repeatable grouting component groups are arranged at intervals along the longitudinal direction of the tunnel. Step 2, connect the two adjacent connecting pipes of two adjacent slurry overflow cylinders near the tunnel ground to a horizontal pipe, horizontally penetrate the waterproof layer and the secondary lining, and extend into the tunnel interior. The upper connecting pipe is used as the drainage end, and the lower connecting pipe is used as the grouting end for connecting with the grouting machine. Step 3, seal the drainage end, start the grouting machine, and the slurry is injected from the grouting end, transported through the annular slurry transportation channel, and fills each slurry overflow cylinder in turn. However, the effect of external grouting reinforcement is often unsatisfactory and requires long-term maintenance; while pasting high-strength materials inside can improve the strength of the tunnel structure, but after the secondary deformation of the tunnel structure, these materials may be separated from the original structure, affecting the reinforcement effect.

[0005] Therefore, there is an urgent need in the art for a treatment method that can more effectively alleviate the existing diseases of tunnel structures, such as large deformations, cracks, water leakage, etc., and fundamentally avoid various diseases during the subsequent operation of tunnel structures, so as to improve the durability and safety of tunnel structures and reduce the subsequent operation and maintenance costs.

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

[0007] Aiming at 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 anti-deformation ability of the tunnel structure, alleviate the existing diseases of the tunnel structure such as large deformations, cracks, water leakage, etc., and fundamentally avoid various diseases during 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 prestress to the tunnel structure through the two side shafts and vertical holes, which can permanently improve the overall stiffness and anti-deformation ability of the tunnel structure, alleviate the existing diseases of the tunnel structure such as large deformations, cracks, water leakage, etc., and fundamentally avoid various diseases during 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 includes the following steps:

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

[0010] S2. Construct a first vertical hole between the tunnel structure and the first shaft, and push the prestressed strand to the bottom of the first vertical hole;

[0011] S3. Locally reinforce the formation according to the formation conditions through the first cable passing openings and the second cable passing openings at the bottoms of the two side shaft support structures, and then excavate to form a first operation opening and a second operation opening. Use a telescopic rod to cross the formation from the second operation opening to the first operation opening, and pull the prestressed strand back to the second operation opening;

[0012] S4. Locally reinforce the formation according to the formation conditions through the third cable passing opening and excavate to form a third operation opening, and then construct a second vertical hole between the tunnel structure and the second shaft, and pull the prestressed strand from the second operation opening to the third operation opening;

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

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

[0015] According to a preferred embodiment, the first shaft and the second shaft are excavated synchronously and the shaft support structure is constructed in a timely manner. The bottom of the shaft is constructed with a bottom reinforcement structure using concrete. The depth of the shaft is greater than the buried depth of the bottom of the tunnel structure, and the inner diameter is designed to meet the movement of construction personnel and the operation of the jack.

[0016] According to a preferred embodiment, the first cable-passing opening and the second cable-passing opening are respectively arranged at the same buried depth position below the bottom of the tunnel structure for the first shaft and the second shaft, and the third cable-passing opening and the tensioning opening are respectively arranged at the same buried depth position above the top of the tunnel structure.

[0017] According to a preferred embodiment, the first cable-passing opening, the second cable-passing opening, the third cable-passing opening and the tensioning opening are pits with a thickness smaller than the surrounding area, and the size of the tensioning opening is larger than that of each of the above-mentioned cable-passing openings. Among them, the above-mentioned pits can be chiseled to reinforce and excavate the outer soil body to form the first operation opening, the second operation opening, the third operation opening and a tensioning operation opening with a size larger than each of the above-mentioned operation openings.

[0018] According to a preferred embodiment, the telescopic rod for towing the prestressed strand is a multi-section telescopic round rod with a hook at the end. Among them, the length of the telescopic rod in the non-telescopic state is smaller than the inner diameter of the shaft support structure, and the length in the fully telescopic state is larger 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 lifting ring, which is connected to the hook of the telescopic rod. Among them, based on the different sand and gravel particle contents of the formation, the prestressed strand is preferably a carbon fiber strand or other high-strength strands with strong corrosion resistance.

[0020] According to a preferred embodiment, the anchoring system includes an anchor backing plate, wedge grips, a jack and a protective cover. The anchor backing plate includes an arc-shaped base, a tensioning surface, a first cluster of holes and a second cluster of holes. The arc radius of the arc-shaped base is consistent with the outer diameter of the tunnel structure. The cluster of holes is a variable-diameter circular inclined hole penetrating the anchor backing plate, including a hole inlet located below the tensioning surface and a hole outlet located above the tensioning surface. The slope of the cluster of holes is designed to ensure that the prestressed strand does not deflect at the hole inlet, and the tensioning surface is approximately perpendicular to the cluster of holes.

[0021] According to a preferred embodiment, one end of the prestressed strand is inserted into the duct inlet of the first duct cluster, passes through the duct outlet, and is fixed at the duct outlet by a wedge; the other end of the prestressed strand is inserted into the duct inlet of the second duct cluster, passes through the duct outlet, and is fixed at the duct outlet by a wedge after tensioning by a jack.

[0022] According to a preferred embodiment, the components of the anchoring system are made of corrosion-treated materials, and the anchoring system is wrapped with a protective cover. Grease is filled in the protective cover or materials such as a polyurea coating are applied to the outer surface of the anchoring system to ensure the anti-corrosion requirements. A waterproof gasket is arranged between the protective cover and the outer surface of the tunnel structure, and expansion bolts are used for fixation.

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

[0024] By applying an external prestressing system outside the tunnel structure, the present invention not only provides circumferential prestress for 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 ovality of the tunnel structure, while the tangential force adds an additional axial force to the tunnel structure. The combined action of the two can effectively reduce the deformation of the tunnel structure and reduce the opening amount of the joints, thereby alleviating existing diseases such as large deformation, cracking and water leakage. This external prestressing system enables the tunnel structure to form a self-stabilizing structural system, significantly enhancing its overall stiffness and anti-deformation ability, and improving 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, so it can effectively prevent further large deformation, cracking or water leakage problems of the tunnel structure, and at the same time reduce the subsequent operation and maintenance costs. In addition, the present invention can select carbon fiber strands as the prestressing material, which has good corrosion resistance and mechanical strength; each component of the anchoring system has been subjected to anti-corrosion treatment and is wrapped with a protective cover, and 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 prestressing system can meet the requirements of the design service life of the tunnel structure. Finally, the present invention only needs to excavate small-sized first and second shafts on both sides of the tunnel structure respectively, and set vertical holes and necessary operation ports and tensioning ports therebetween for applying external prestress. The first and second shafts are constructed symmetrically and synchronously, which can minimize the impact of the external prestress construction on the existing tunnel structure, ensure the micro-disturbance characteristics during the construction process, and guarantee the safety and stability of the original structure. In summary, the present invention provides an efficient, reliable and durable technical solution, bringing significant technical effects and economic benefits to the treatment of shield tunnel diseases. 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 prestress 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 prestress 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 prestress 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 prestress 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 prestress 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 prestress provided by the present invention;

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

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

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

[0034] Figure 10 It is a structural schematic diagram of the anchor backing plate provided by the present invention;

[0035] Figure 11 It is a schematic diagram of the tension surface of the anchor backing plate provided by the present invention;

[0036] Figure 12 It is a schematic diagram of the action mechanism of the external prestress on the tunnel structure provided by the present invention;

[0037] Figure 13 It is the effective prestress of the prestressed strands considering the prestress loss terms σ 1 and σ 2 after the anchoring system provided by the present invention is in different layout schemes;

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

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

[0040] Figure 16 It is a comparison diagram of the axial force distribution between the external prestressing treatment solution and the ordinary solution under the unloading condition provided by the present invention;

[0041] Figure 17 It is a comparison diagram of the bending moment distribution between the external prestressing treatment solution and the ordinary solution under the unloading condition provided by the present invention;

[0042] Figure 18 It is a comparison diagram of the overall deformation between the external prestressing treatment solution and the ordinary solution under the unloading condition provided by the present invention.

[0043] List of reference numerals

[0044] 100: Tunnel structure; 101: First shaft; 102: Second shaft; 103: Shaft support structure; 104: First cable-passing opening; 105: Second cable-passing opening; 106: Third cable-passing opening; 107: Tensioning opening; 108: Bottom reinforcement structure; 200: First vertical hole; 201: Second vertical hole; 202: Prestressing strand; 203: Suspension ring; 204: Telescopic rod; 205: Hook; 301: First operation opening; 302: Second operation opening; 303: Third operation opening; 304: Tensioning operation opening; 400: Anchoring system; 401: Anchor plate; 402: Arc-shaped base; 403: Tensioning surface; 404: First duct cluster; 405: Second duct cluster; 406: Duct entrance; 407: Duct exit; 408: Wedge; 409: Jack; 500: Protective cover; 501: Waterproof gasket; 502: Expansion bolt; 600: Inspection well; 601: Inspection well bottom; 602: Manhole cover. Detailed implementation manners

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

[0046] As Figures 1 to 8 disclosed, the present invention discloses a method for treating shield tunnel diseases 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 diseases, and construct a first shaft 101, a second shaft 102 and a shaft support structure 103 on both sides of the tunnel structure 100 respectively.

[0048] Preferably, the spatial position of the tunnel structure 100 includes parameters such as tunnel coordinates, burial depth, diameter, and surrounding pipelines. At the same time, considering that the tunnel structure 100 will undergo structural settlement and convergence deformation during construction and operation, the actual position of the tunnel structure 100 needs to consider the influence caused by the deformation.

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

[0050] Preferably, the first vertical hole 200 can be drilled after the shaft structure is constructed. It is located between the tunnel structure 100 and the shaft and is as close as possible to the cable-passing opening or tensioning opening 107 of the shaft because the first vertical hole 200 needs to be located within the subsequently formed operation opening to facilitate the winding of the prestressed strand 202 at the operation opening. Preferably, the first vertical hole 200 can be excavated in the form of slurry-supported wall to avoid collapse of the hole. Further, a telescopic rod 204 or a rod with a length exceeding the depth of the shaft and having a hook 205 at any end can be used to push the prestressed strand 202 to the bottom of the first vertical hole 200. During the pushing process, avoid the rod or the prestressed strand 202 rubbing against the hole wall of the first vertical hole 200 and causing collapse of the hole. Preferably, the purpose of constructing the shaft and the vertical hole is to facilitate the winding of the prestressed strand 202 around the tunnel structure 100 for one circle, which is an optional auxiliary measure or structure of the present invention. The present invention can also use other methods that can achieve the winding of the prestressed strand 202 around the tunnel structure 100 for one circle.

[0051] S3. According to the formation conditions, locally reinforce the formation through the first cable-passing opening 104 and the second cable-passing opening 105 at the bottom of the two-side shaft support structure 103, and then excavate to form the first operation opening 301 and the second operation opening 302. Use the telescopic rod 204 to cross the formation from the second operation opening 302 to the first operation opening 301, and pull back the prestressed strand 202 to the second operation opening 302.

[0052] Preferably, the area of the formation grouting reinforcement should be larger than the size of the operation opening to ensure the stability of the formation after the operation opening is excavated.

[0053] Preferably, for formations with good permeability and rich groundwater, water glass-based materials can be selected for grouting reinforcement or local treatment of the formation can be carried out by means of weak freezing, etc., to play a role in stabilizing the soil body and waterproofing. At the same time, the strength of the soil body after reinforcement is very low, which is convenient for the construction of the operation opening and does not affect the cutting of the soil body during the subsequent tensioning of the prestressed strand 202. For formations with low permeability or good stability, no reinforcement treatment is required.

[0054] S4. Through the third cable-passing opening 106, locally reinforce the formation according to the formation conditions and excavate to form the third operation opening 303. Then, construct the second vertical hole 201 between the tunnel structure 100 and the second vertical shaft 102, and pull the prestressed strand 202 from the second operation opening 302 to the third operation opening 303.

[0055] S5. Through the tensioning opening 107, locally reinforce the formation according to the formation conditions and excavate to form the tensioning operation opening 304. Use the telescopic rod 204 to cross the formation 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. Pass both ends of the prestressed strand 202 through the anchoring system 400. Fix one end and connect the other end to the jack 409 and tension it to apply external prestress to the tunnel structure 100.

[0057] Preferably, in step S6, before the prestressed strand 202 penetrates into the anchoring system 400, the outer surface of the tunnel structure 100 at the third operation opening 303 can be cleaned first. The cleaning work not only removes the 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 tensile force to be effectively transmitted from the prestressed strand 202 to the tunnel structure 100, improving the reinforcement effect. At the same time, the clean surface facilitates the construction personnel to inspect the state of the tunnel structure 100, confirm that there are no cracks or other diseases, thus ensuring the construction quality, and helps to discover and handle the 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 unobstructed working surface also makes it more convenient to install the anchoring system 400 and can be adjusted as needed to ensure the correct positioning of the prestressed strand 202.

[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 during subsequent operation. The applied prestress value is related to the current conditions of the tunnel structure 100 and the possible subsequent conditions, including the design parameters of the tunnel structure 100, the existing deformation characteristics, the formation conditions, the proposed adjacent construction, etc.

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

[0060] S7. Perform anti-corrosion and rust-proof treatment on the anchoring system 400, fill the first vertical hole 200, the second vertical hole 201 and the second vertical shaft 102 with mortar. Fill the bottom of the first vertical shaft 101 to below the tensioning opening 107 and cover the top to form an inspection well 600.

[0061] Preferably, the above steps can be repeated until the application of multiple external prestresses within the length range of the tunnel structure 100 to be treated for diseases is completed. Preferably, the rationality of the assumed conditions for the application of multiple external prestresses can be verified through numerical simulation. Exemplarily, based on the relevant design and test foundation of the prestressed segment structure in the early stage, the following reference design can be obtained: 4 to 6 prestressing strands 202 with a diameter of 15.2 mm and a tensile strength of 3000 MPa are used, the controlled tensile force is 2400 MPa, and the spacing between the prestressing strands 202 is about 2 m.

[0062] Preferably, the anchoring systems 400 of multiple external prestresses longitudinally arranged along the tunnel structure 100 can be symmetrically arranged on both sides of the tunnel structure 100, that is, the first bunch of anchoring systems 400 are arranged on the left side of the tunnel structure 100 and tensioned, and then the next bunch of anchoring systems 400 are arranged on the right side of the tunnel structure 100 and tensioned, and so on in a cycle. Such an arrangement is considered because the prestress loss will occur during the tensioning process of the prestressing strands 202 due to factors such as the deformation of the anchor, the shrinkage of the prestressing strands 202, the friction between the prestressing strands 202 and the duct, and the creep of the concrete, and this prestress loss will gradually increase with the increase in the distance from the anchoring system 400, resulting in uneven stress on the tunnel structure 100. By symmetrically arranging the anchoring systems 400 on both sides of the tunnel structure 100, the maximum prestress loss parts of adjacent external prestress systems can be staggered, which can not only improve the uniformity of the overall prestress bearing capacity of the tunnel structure 100, but also make the stress of the tunnel structure 100 more reasonable and stable. The above arrangement method helps to ensure the prestress effect of each anchoring point, reduce the potential structural risks caused by excessive local prestress loss, and at the same time optimize the mechanical properties of the entire tunnel structure 100. In addition, the symmetrical arrangement is also beneficial to the operation balance during the construction process and reduces the possible structural offset problems caused by unilateral loading.

[0063] Preferably, the first shaft 101 and the second shaft 102 should be excavated simultaneously. The shafts are circular, and it is advisable to have a smaller outer diameter rather than a larger one, and a larger clear distance from the tunnel structure 100 rather than a smaller one, so as to avoid uneven load distribution on both sides of the tunnel structure 100 caused by different excavation depths of the shafts and reduce the disturbance to the tunnel structure 100 due to the unloading effect during shaft construction. Meanwhile, during the shaft excavation process, the shaft support structure 103 should be constructed in a timely manner to prevent the shaft itself from deforming. The outer diameter of the shaft can be limited to about 1.2 m to 1.5 m, and the clear distance from the tunnel structure 100 can be limited to more than 0.5 m. The shaft support structure 103 can adopt a precast reinforced concrete structure, and waterproof treatment should be carried out at the joints. After the shaft excavation is completed, the bottom of the shaft can be reinforced with concrete to construct the bottom reinforcement structure 108, and waterproof treatment should be carried out. After the shaft is constructed, the depth of the bottom reinforcement structure 108 of the shaft should be greater than the bottom buried depth of the tunnel structure 100 to facilitate the cable threading construction of the prestressing strands 202 at the bottom. Since the control equipment such as the tensioning machine required for prestress tensioning is placed on the ground outside the shaft, the inner diameter of the shaft only needs to meet the requirements for the movement of construction personnel and the operation of the jack 409.

[0064] Preferably, the first cable threading opening 104 and the second cable threading opening 105 are respectively arranged at the same buried depth position below the bottom of the tunnel structure 100 for the first shaft 101 and the second shaft 102, and the third cable threading opening 106 and the tensioning opening 107 are respectively arranged at the same buried depth position above the top of the tunnel structure 100. When the shaft support structure 103 adopts a precast structure, the tunnel buried depth should be considered during the preparation stage of the precast structure, so as to set the cable threading openings (the first cable threading opening 104, the second cable threading opening 105, the third cable threading opening 106) and the tensioning opening 107. If the buried depths of the cable threading openings and the tensioning opening 107 are set improperly, it will cause the subsequent telescopic rod 204 to be unable to reach the corresponding operation opening after crossing the formation, resulting in the inability to pull the prestressing strands 202.

[0065] Preferably, the cable-passing opening and the tensioning opening 107 have different functions. Among them, the cable-passing opening mainly serves for the telescopic rod 204 to tow the prestressed strand 202, and has a relatively small size. In addition to the function of the cable-passing opening, the tensioning opening 107 also needs to serve for the tensioning of the prestressed strand 202, and has a relatively large size. In addition, both the cable-passing opening and the tensioning opening 107 need to be chiseled during construction, and the structural thickness of this area should be thinner than that of other areas. Therefore, the first cable-passing opening 104, the second cable-passing opening 105 and the third cable-passing opening 106 are designed as small-sized pits with a thickness smaller than that of the surrounding area, and the tensioning opening 107 is designed as a large-sized pit with a thickness smaller than that of the surrounding area. The first cable-passing opening 104, the second cable-passing opening 105 and the third cable-passing opening 106 can be chiseled at one time and the outside soil body can be grouted and reinforced, and then the first operation opening 301, the second operation opening 302 and the third operation opening 303 with small sizes are excavated. The tensioning opening 107 has a large size, and chiseling it at one time is likely to cause the instability of the soil body. Small holes can be chiseled first for grouting and reinforcing the soil body, and then it can be chiseled completely to construct the 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. The connection between the hook 205 of the telescopic rod 204 and the suspension ring 203 of the prestressed strand 202 needs to be carried out in this area, so as to facilitate the telescopic rod 204 to tow the prestressed strand 202. Among them, the size of the small-sized operation opening can be, for example, 15 cm×15 cm×15 cm. Preferably, the main purpose of designing the tensioning operation opening 304 as a large size is to serve for the fixing and tensioning of the prestressed strand 202. Therefore, the space requirements for the installation of the anchoring system 400 and the construction of the jack 409 need to be met. Among them, the size of the large-sized tensioning operation opening 304 can be, for example, 50 cm×50 cm×50 cm.

[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. Therefore, a telescopic rod 204 with a telescopic function and a hook 205 at the end needs to be selected for towing the prestressed strand 202. If the same telescopic rod 204 is used for the horizontal and vertical towing of the prestressed strand 202, the length of the telescopic rod 204 in the non-telescopic state is smaller than the inner diameter of the shaft support structure 103, and the length in the fully telescopic state is greater than the depths of the first shaft 101 and the second shaft 102. If the telescopic rod 204 is only used for the horizontal towing of the prestressed strand 202, the length of the telescopic rod 204 in the fully telescopic state is greater than the distance between the first shaft 101 and the second shaft 102, and any rod with a hook 205 at the end and a length exceeding the shaft depth can be used for the vertical towing of the prestressed strand 202.

[0067] Preferably, the end of the prestressed strand 202 is a circular lifting ring 203, which can be connected to the hook 205 of the telescopic rod 204. Considering that the external prestressing 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 will affect the durability and long-term safety of the external prestressing system. At the same time, the prestressed strand 202 is in the soil. During tensioning, in order to ensure the circumferential prestress distribution is as uniform as possible, 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 environments such as the nuclear industry and seawater, which can meet the durability requirements of the external prestressing of the 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 backing plate 401 are shown. The anchoring system 400 includes an anchor backing plate 401, wedge grips 408, a jack 409 and a protective cover 500. The anchoring system 400 is used for the tensioning and fixing (i.e., anchoring) of the prestressed strand 202. Limited by the operating space, the external 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 backing plate 401 includes an arc-shaped base 402, a tensioning surface 403, a first pore cluster 404 and a second pore cluster 405. The contact part between the anchor backing plate 401 and the tunnel structure 100 can adopt the arc-shaped base 402. The arc radius of the arc-shaped base 402 is the same as the outer diameter of the tunnel structure 100, that is, the entire surface of the arc-shaped base 402 can be in close contact with the outer surface of the tunnel structure 100. On the one hand, it is convenient for the movement of the arc-shaped base 402 during the tensioning process. On the other hand, it can increase the contact area between the anchor backing plate 401 and the tunnel structure 100, and avoid damaging the tunnel structure 100 due to excessive stress on the tunnel structure 100 caused by the anchor backing plate 401 after tensioning. The first pore cluster 404 and the second pore cluster 405 can be arranged in a rectangular or circular array, and are variable-diameter circular inclined holes penetrating the anchor backing plate 401, including a small-diameter pore inlet 406 located below the tensioning surface 403 and a large-diameter pore outlet 407 located above the tensioning surface 403. Since the wedge grip 408 is in the shape of a frustum with a circular through-hole in the middle, the prestressed strand 202 can pass through the circular channel of the wedge grip 408. The wedge grip 408 is installed at the pore outlet 407. The design of the variable-diameter circular inclined hole is beneficial to clamping the prestressed strand 202 by the wedge grip 408 during tensioning, and the greater the tensioning force, the greater the clamping force. In addition, since the pore inlet 406 is higher than the outer surface of the tunnel structure 100 and the prestressed strand 202 is obliquely inserted into the pore inlet 406, the slope of the pore cluster should be designed so that the prestressed strand 202 does not deflect at the pore inlet 406, and the tensioning surface 403 also needs to be as perpendicular to the pore cluster as possible to reduce the prestress loss during tensioning.

[0070] Preferably, the external prestressing system can adopt a scheme of fixed at one end and tensioned at the other end. One end of the prestressing strand 202 penetrates into the duct inlet 406 of the first duct cluster 404, passes through the duct outlet 407, and is fixed at the duct outlet 407 by the wedge 408. The other end of the prestressing strand 202 penetrates into the duct inlet 406 of the second duct cluster 405, passes through the duct outlet 407, and is fixed by the wedge 408 after being tensioned by the jack 409. For the convenience of the operation of the jack 409, the jack 409 should face the side of the shaft (the first shaft 101 or the second shaft 102). During prestressing, under the action of the pulling force of the jack 409, the prestressing strand 202 cuts the soil body and continuously tightens towards the outer wall of the tunnel structure 100, and finally is closely attached to the outer wall.

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

[0072] Preferably, the environment where the external prestressing system is located is harsh and needs to be regularly inspected and maintained. Except for the first shaft 101, the remaining excavated shafts, vertical holes, operation openings, etc. need to be sealed in time after the external prestressing is completed. By treating the first shaft 101, it can be changed into an inspection well 600. Since the depth of the first shaft 101 is relatively large, it is not conducive to workers detecting the prestress loss and structural corrosion of the anchoring system 400 at the tensioning port 107. When constructing the inspection well 600, the bottom of the first shaft 101 needs to be filled, and the filling depth reaches the area below the tensioning port 107, and the inspection well bottom 601 is constructed with concrete. At the same time, the manhole cover 602 of the inspection well 600 can be prepared with a steel-concrete structure, and the strength of the manhole cover 602 should meet the driving safety requirements. When necessary, the opening can be waterproof-sealed.

[0073] According to a preferred embodiment, the action mechanism of the external 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 of the prestressing strand 202, prestress losses will be generated due to factors such as anchor deformation, strand shrinkage, concrete elastic deformation, and concrete creep. Among them, the prestress loss (σ 1 ) caused by anchor deformation and shrinkage of the prestressing strand 202 and the prestress loss (σ 2) It accounts for a relatively large proportion among all the prestress losses. Therefore, the present invention mainly considers the prestress losses caused by σ 1 and σ 2 . The calculation formula is as follows:

[0076] ,

[0077] ,

[0078] In the formula, σ con is the tensile control stress value of the prestressed strand 202, and the anchor mouth friction loss 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 segment assembly; r is half of the outer diameter of the segment; θ is the included angle between the tangent line of the curve pipeline part from the tension end to the calculation section; θ 0 is the reverse friction influence angle of the prestressed strand 202, which can be calculated by the following formula:

[0079] ,

[0080] In the formula, a is the deformation of the tension end anchor and the shrinkage value of the prestressed strand 202; E s is the elastic modulus of the prestressed strand 202.

[0081] The effective prestress (σ e ) of the prestressed strand 202 is the tensile control stress value of the prestressed strand 202 minus each prestress loss. The calculation expression is as follows:

[0082] .

[0083] (2) Action mechanism of external prestress on the tunnel structure 100

[0084] As Figure 12 shown, after the prestressed strand 202 is tensioned, the prestress will act on the tunnel structure 100. Through decomposition, a radial force (σ n ) pointing to the center of the tunnel structure 100 and a tangential force (σ t ) tangent to the outer surface of the tunnel structure 100 can be formed. Select a micro-element section of the prestressed strand 202 and the tunnel structure 100 for force analysis. The equilibrium equation of the prestressed strand 202 can be expressed as:

[0085] ,

[0086] In the formula, dσ e is the effective prestress increment of the prestressed strand 202; dθ is the included angle of the micro-segment of the prestressed strand 202; t is the converted width of the action surface of the prestressed strand 202, and the width of the anchor slot can be taken; θ is the included angle between the tangent line of the curve pipeline part from the tension end to the calculation section.

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

[0088] ,

[0089] .

[0090] Based on the above conclusion, the expressions for the radial force (σ n ) and the tangential force (σ t ) can be obtained as follows:

[0091] ,

[0092] .

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

[0094] The tangential force (σ t ) generated by the external prestressing on the tunnel structure 100 after tensioning and anchoring 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 part is the axial force generated by the external water and soil loads, and the other part 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] Figure 13 is the effective prestress of the prestressed strand 202 considering the prestress loss terms σ 1 and σ 2 under different layout schemes of the anchoring system 400. Among them, 6 bundles of prestressed strands 202 are selected, 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. Taking the top of the tunnel structure 100 as 0°, the angle is increased clockwise. The right anchoring position of the tunnel structure 100 is at 60°, and the left anchoring position is at 300°. σ con is 2400 MPa, μ is 0.2 rad -1 , k is 0.0015 m -1 , a is 1 mm, E sis 150 GPa. 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 - 1892 kN, and the difference between the maximum and minimum effective prestresses is 790 kN; when the anchoring systems 400 are arranged at intervals on the right and left sides of the tunnel structure 100, the average effective prestresses of the prestressed strands 202 on the left and right sides are between 1357 - 1700 kN, and the difference between the maximum and minimum effective prestresses is 342 kN, and the prestress difference is only 43% of that in the unilateral arrangement. When the anchoring systems 400 are all arranged on the right side or the left side of the tunnel structure 100, the effective prestress is asymmetrically distributed along both sides of the tunnel structure 100, and the tunnel structure 100 bears 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 stress of the tunnel structure 100 is more uniform and more reasonable.

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

[0097] (1) Model parameter settings

[0098] Figure 14 is a software simulation schematic diagram of shaft excavation under the external prestress treatment scheme established by using the stratum structure model. The outer diameter of the tunnel structure 100 is 6.0 m, the thickness is 0.3 m, the ring width is 1.5 m, and there are 5 rings in total, with a top burial depth of 15 m. The outer diameters of the shaft structures on both sides are 1.2 m, the inner diameters are 0.8 m, the burial depth is 23 m, the spacing is 2 m, and the net distance from the tunnel structure 100 is 1.8 m. Both the shafts and the tunnel structure 100 are made of C50 concrete. The stratum is fine silty sand, and the modified Mohr - Coulomb model is adopted. The elastic modulus of the soil layer is 24.14 MPa, the Poisson's ratio is 0.3, the unit weight is 20.3 kN / m 3 , the secant stiffness of the triaxial test is 5000 kN / m 2 , the unloading elastic modulus is 50 MPa, and the ultimate dilation angle is 10°.

[0099] (2) Simulation steps

[0100] a. Establish a soil model and conduct in - situ stress balance; b. Excavate the tunnel and construct the tunnel structure 100; c. Excavate the shafts and construct the support structure.

[0101] (3) Simulation results

[0102] The horizontal deformation of the tunnel structure 100 before and after the shaft excavation under the external prestress treatment scheme is as Figure 15As shown in the figure. The maximum horizontal deformations of the tunnel structure 100 before and after the shaft excavation are 6.71 mm and 6.74 mm respectively, and the deformation increment is only 0.03 mm, that is, 0.4%. This shows that the shaft excavation has little effect on the deformation of the tunnel structure 100. In other words, the construction of external prestress is a micro-disturbance to the tunnel structure 100.

[0103] According to another preferred embodiment, the method for treating shield tunnel diseases with external prestress of the present invention is compared with the ordinary method, and the specific comparison process is as follows:

[0104] (1) Model parameter setting

[0105] A three-dimensional model of the tunnel structure 100 is established by using Abaqus software, and the shield tunnel diseases are treated under the condition of unloading on both sides by using the external prestress treatment scheme and the ordinary scheme of the present invention respectively. The outer diameter of the tunnel structure 100 is 6.0 m, the thickness is 0.3 m, the ring width is 1.5 m, and there is 1 ring in total. The material is C50 concrete. The external prestress treatment scheme is to set a bundle of prestressed carbon fiber strands composed of 6 pieces of 15.2 mm outside the tunnel structure 100, with a tensile strength of 3000 MPa, which is a truss-linear elastic model, and the tension control stress value is 2400 MPa. The ordinary scheme does not set external prestress. The load structure model is used to apply the loads around the tunnel structure 100, where the vertical pressure and the bottom reaction force are 220 kPa, and the lateral pressure is 80 kPa.

[0106] (2) Simulation steps

[0107] For the external prestress treatment scheme, the simulation steps are as follows: a. Establish the model of the tunnel structure 100 and carry out in-situ stress balance; b. Apply the loads around the tunnel structure 100; c. Establish the model of the prestressed strands and apply prestress to the prestressed strands; d. Reduce the pressure on both sides of the tunnel structure 100 to 40 kPa. Preferably, for the ordinary scheme, the simulation step c can be deleted.

[0108] (3) Simulation results

[0109] The internal forces of the external prestress treatment scheme and the ordinary scheme under the unloading condition are respectively as Figure 16 and Figure 17 shown. The axial force per unit length of the external prestress treatment scheme and the ordinary scheme are 2005.5 kN and 925 kN respectively. Among them, compared with the ordinary scheme, the axial force of the external prestress treatment scheme is increased by 117%. The bending moments of the external prestress treatment scheme and the ordinary scheme are 343 kN·m and 323 kN·m respectively. Among them, compared with the ordinary scheme, the bending moment of the external prestress treatment scheme increases slightly, but generally, the internal forces of the existing tunnel are improved significantly, and at the same time, 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 Figure 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), fix one end of the strand and connect the other end to the jack (409) and tension it, so as to apply external prestress to the tunnel structure (100). When the prestress is tensioned, the prestressed strand (202) cuts the soil under the pulling force of the jack (409) and continuously tightens toward the outer wall of the tunnel structure (100), and finally adheres closely to the outer wall.

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).

Images