Pre-compressive stress rib shield non-excavation repairing method for concrete drainage pipeline

Abstract

The invention relates to a compressive pre-stress rib shield trenchless repair method for a concrete drainage pipeline. The inner wall of the concrete drainage pipeline to be repaired is subjected to surface pretreatment; laying a galvanized steel wire mesh on the inner wall of the pipeline along the axis of the pipeline and fixing; adding a mortar cushion block serving as a support on the inner wall of the pipeline, installing a plurality of pre-compressive stress steel bars, and then adjusting the pre-compressive stress steel bars to generate preset compressive stress; binding and positioning the galvanized steel wire gauze and the pre-compressive stress steel bars, enabling the bound galvanized steel wire gauze to be in a tightened state so as to form external tightening force facing the pipe wall, and forming a pre-compressive stress rib shield capable of resisting initial circumferential pressure with the pre-compressive stress steel bars; cement paste is sprayed to the inner wall of the pipeline, polymer mortar is used for plastering and repairing in a layering mode, and tire supporting plates and adjustable supporting frames are used for tire supporting in a blocking mode; and the tire supporting plate and the adjustable supporting frame are dismantled, and the polymer mortar is maintained. The method has the beneficial effect that local or integral homogeneous material non-excavation repair can be carried out under the severe condition that an underground concrete pipeline is humid or seeps water.

Description

Technical Field

[0001] The invention relates to the technical field of building engineering construction, and in particular to a trenchless repair method for a prestressed reinforcement shield of a concrete drainage pipe. Background Art

[0002] After a certain number of years of use, the inner walls of rainwater and sewage concrete drainage pipes will generally develop structural defects such as corrosion, severe peeling, cracking, and leakage. The resulting structural defects can cause sewage to leak out of the pipe and cause groundwater pollution, or groundwater to leak into the pipe and cause the sand cushion layer under the pipe to be lost, the roadbed to be damaged, and the road surface to be deformed, damaged, and collapsed, causing serious safety accidents.

[0003] Existing trenchless repair technologies for concrete drainage pipes all have some shortcomings. For example, the mainstream UV-curing integral repair technology and heat shrink molding repair technology cannot adapt to the deformation and temperature changes of the foundation because the inner wall of the repaired pipe is a rigid-brittle structure and no expansion joints are set. They cannot meet the working conditions that the structure should not be damaged when the pipe is full of water and when it floats when it is empty. Some trenchless repair technologies require excavation of working pits, which is very inconvenient. Some trenchless technologies use diameter reduction treatment, which has a greater impact on the flow of rainwater and sewage. The broken pipe technology has a greater impact on the foundation when the pipe is pushed in or replaced after treatment, causing holes outside the pipe, which is easy to cause road surface settlement.

[0004] Therefore, for the trenchless repair of concrete drainage pipes, the use of concrete-like homogeneous materials for reinforcement can not only repair defects and strengthen the pipe ring stiffness, but also prevent the original pipe concrete from continuing to be damaged by carbonization or alkali aggregate expansion. This is the most appropriate method. Many units and colleges have conducted research and technical development on this. However, under the harsh conditions of existing pipes being damp or even leaking, it is very difficult to ensure that the repair material has a high bonding strength with the original pipe and is anti-seepage and anti-corrosion, and to overcome the creep, voiding and shrinkage cracks of the concrete material during the homogeneous material reinforcement repair. Currently, there is no solution. The main reason for success is that creep causes the deformation of concrete structure to increase, which is detrimental to the structure. For example, it increases the deflection of bending members, which is particularly obvious in the upper part of the circumferential reinforcement. If no measures are taken, the upper part of the circumferential reinforcement made of homogeneous material will be separated from the original inner wall of the pipe under the action of creep and gravity to form a cavity. When there is groundwater outside the pipe, the air bubbles attached to the cavity will burst under the vibration of road vehicles, thereby causing damage to the reinforcement structure. Therefore, how to overcome the above defects and successfully reinforce the inner wall of the existing concrete pipe with homogeneous materials has become an urgent problem to be solved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a trenchless repair method of a prestressed reinforcement shield for a concrete drainage pipe, so as to overcome the deficiencies in the above-mentioned prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A trenchless repair method for pre-stressed tendon shield of concrete drainage pipes, comprising the following steps:

[0008] S1. Perform surface pretreatment on the inner wall of the concrete drainage pipe to be repaired, chisel the inner wall of the pipe to an appropriate depth for the repair polymer mortar, repair the holes, and chisel shallow grooves for placing the ends of the galvanized steel wire mesh along the circumferential surface at the pipe ends;

[0009] S2. Lay the galvanized steel wire mesh along the pipe axis on the inner wall of the pipe and fix it;

[0010] S3. Add mortar pads as supports on the inner wall of the pipe, install a plurality of closed annular pre-stressed steel bars at a predetermined spacing along the pipe axis, and then adjust the closed annular pre-stressed steel bars to generate a predetermined compressive stress;

[0011] S4. Bind and position the galvanized steel wire mesh and the closed annular pre-stressed steel bars, so that the bound galvanized steel wire mesh is in a taut state, to form an external tension force towards the pipe wall, and form a pre-stressed tendon shield that can resist the initial circumferential pressure with the closed annular pre-stressed steel bars;

[0012] S5. Spray cement slurry on the inner wall of the pipe, then plaster and repair it with polymer mortar in layers, and use a tire support plate and an adjustable support frame to support in layers and blocks during the hardening process of the polymer mortar;

[0013] S6. Remove the tire support plate and the adjustable support frame, and cure the polymer mortar.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Further, the surface pretreatment in S1 includes: cleaning scale, removing carbonized layer and surface roughening. Among them, the scale is cleaned by a high-pressure water cleaning vehicle, the carbonized layer is removed by manual or mechanical methods, and the surface is roughened by sandblasting or shot peening to reach a roughness convenient for the bonding of the later plaster layer; the chiseling is carried out by an electric pick or a pneumatic pick to make the surface repair polymer mortar reach an appropriate depth.

[0016] Further, for the plastering thickness not greater than 10 mm in S1, it should be chiseled to a plastering thickness not less than 10 mm; the holes are repaired with polymer mortar or mortar with wire mesh to repair the holes in the pipe.

[0017] Further, in S2, the lap width between the mesh sheets of the galvanized steel wire mesh laid on the inner wall of the pipe is not less than 100 mm, and the ends of the galvanized steel wire mesh in the pipe axis direction are buried in the shallow grooves and fixed densely at the ends.

[0018] Furthermore, the processing method of the closed-loop prestressed steel bar in S3 is as follows: the steel bar wire rod is cut into two sections according to the inner circumference of the pipeline, and is divided into upper and lower sections of prestressed steel bars; the two front ends of each section of prestressed steel bars are straightened and threaded; the two ends of the upper and lower sections of prestressed steel bars are fully connected by threading a positive and negative thread connecting sleeve to form a closed-loop prestressed steel bar; the closed-loop prestressed steel bar can be adjusted to generate a predetermined compressive stress by rotating the positive and negative thread connecting sleeve; and the steel bar joints between two adjacent closed-loop prestressed steel bars are staggered in the circumferential position of the pipeline.

[0019] Furthermore, if the surface moisture content of the pipe wall is ≤4% before spraying cement slurry in S5, water should be sprinkled to moisten it. Plastering construction can only be carried out when the surface moisture content is ≤6%. When plastering in layers, the next layer of plastering should be carried out only after the previous layer of mortar has finally set, and the circumferential gaps between layers should be staggered.

[0020] Furthermore, the layered polymer mortar plastering in S5 includes: using layered mortar plastering in the center upper half of the pipe cross section, and using fine stone concrete for one-time pouring or fine stone concrete + surface polymer mortar in the center lower half of the pipe cross section, and also includes a solution in which the total plastering thickness is only one layer of polymer mortar.

[0021] Furthermore, in S5, a permeable template cloth is pasted on the surface of the tire support plate before the tire support is carried out on the surface layer polymer mortar. If the total thickness of the plastering polymer mortar is ≥30mm, a layer of hanging mesh is added before the construction of the surface layer polymer mortar.

[0022] Furthermore, the tire support plate in S5 is an elastic plate, and the pressure that the elastic plate can provide when it is supported to the pipe diameter is ≥0.1Mpa and <0.5Mpa.

[0023] Furthermore, if there is a gap between the joints of the upper and lower tire support plates in S5, tire support plates of the same quality and width can be used as temporary pads; arc-shaped fir board strips are used at the expansion joints as side templates for the repair mortar to support it, and at the same time, a layer of permeable template cloth pasted on the surface of the tire support plate during the construction of the mortar surface layer is used to absorb excess water in the mortar through the template cloth and the fir board, and at the same time, water seepage from the pipe wall can also be discharged, and a hardened layer can be formed on its surface after the mortar solidifies.

[0024] The beneficial effects of the present invention are:

[0025] 1) Using homogeneous materials for trenchless repair of corrosion and shedding of existing concrete pipes can enhance the ring stiffness of the original pipes, protect the steel bars in the concrete of the existing pipes from rust or continued rust, and extend the service life;

[0026] 2) Galvanized steel wire mesh (anti-crack steel wire mesh) is used to bind the prestressed steel bars in the axial direction of the pipeline. The upper and lower sections of the prestressed steel bars are connected at both ends with positive and negative wire connection sleeves, which is more secure than overlapping. There is no need to drill holes in the existing pipeline to plant the bars for fixing. It is simple, labor-saving and cost-saving without destroying the original structure. The prestressed steel bars are evenly distributed around the inner wall of the pipeline to form a shield structure with an external arch force, which overcomes the creep and gravity de-airing effects of concrete materials during the reinforcement and repair of homogeneous materials, ensures the bonding strength between the reinforcement material and the inner wall of the pipeline, and prevents shrinkage cracks in the reinforced concrete materials, corrosion of the existing pipeline steel bars, and expansion and continued carbonization damage of the alkali aggregate expansion of the existing pipeline concrete;

[0027] 3) Since the aggregates used in domestic concrete pipes are generally alkali-active, it is more likely that alkali-aggregate expansion damage and inner wall shedding will occur when the sewage quality is alkaline. Repairing with homogeneous materials can prevent the alkali-aggregate expansion damage of existing pipes from continuing to expand;

[0028] 4) When the concrete pipe is operated under the condition of weak acid sewage quality, the acid water will neutralize the alkaline material of the concrete pipe. If other methods are used instead of using homogeneous materials for repair, the original pipe will continue to be carbonized and damaged. Therefore, in theory, homogeneous materials should be used for repair, and the polymer mortar repair used in the present invention is a more ideal solution;

[0029] 5) It can be used to repair pipelines in wet concrete conditions, and can also be used to repair concrete pipelines in conditions of small amounts of water seepage;

[0030] 6) Adopt layered polymer mortar (concrete) for layered and block support, and timely support can be carried out during the period from initial setting to final setting of polymer mortar (concrete), which is conducive to flow construction, with low cost, fast construction period and good quality.

[0031] 7) It is applicable to both circular concrete drainage pipes and special-shaped concrete drainage pipes. It can be used for local repair or overall repair to save investment. Of course, it does not rule out its application in box culverts. In this case, the repair object can be replaced with the box culvert. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the arrangement of the closed-loop prestressed steel bars in the concrete drainage pipe in the present invention;

[0033] Figure 2 It is a cross-sectional view of the concrete drainage pipe, the closed-loop prestressed steel bar, the mortar pad, and the polymer mortar in the present invention;

[0034] Figure 3 It is a schematic diagram of the polymer mortar tire support in the present invention;

[0035] Figure 4 This is a diagram showing the connection status of the upper and lower prestressed tendons and the positive and negative wire connecting sleeves in the present invention.

[0036] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0037] 1. Concrete drainage pipe, 2. Galvanized steel wire mesh, 3. Mortar pad, 4. Closed ring prestressed steel bar, 410, prestressed bar, 420, positive and negative wire connecting sleeve, 5. Polymer mortar, 6. Tire support plate, 7. Adjustable support frame. DETAILED DESCRIPTION

[0038] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0039] Example 1

[0040] like Figures 1 to 4 As shown, a trenchless repair method for a prestressed reinforcement shield of a concrete drainage pipe comprises the following steps:

[0041] S1. Pre-treat the inner wall of the concrete drainage pipe 1 to be repaired, chisel the inner wall of the pipe until the repair polymer mortar reaches an appropriate depth, repair the hole, and dig a shallow groove along the circumference of the end of the pipe for placing the end of the galvanized steel wire mesh 2;

[0042] S2. Lay galvanized steel wire mesh 2 on the inner wall of the pipeline and fix it. In most cases, the coarse aggregate of the concrete on the inner wall of the pipeline is exposed. If cement slurry is sprayed first and then the mesh is hung, it is difficult to avoid the coarse aggregate when the mesh is hung and nailed, resulting in failure of fixation at this point. Therefore, it is advisable to hang the mesh first;

[0043] S3, adding a mortar pad 3 as a support to the inner wall of the pipeline, and installing a plurality of closed-loop prestressed steel bars 4 at a predetermined interval along the axis of the pipeline, that is, installing the plurality of closed-loop prestressed steel bars 4 at the designed position, and then adjusting the closed-loop prestressed steel bars 4 to generate a predetermined compressive stress;

[0044] S4, tying and positioning the galvanized steel wire mesh 2 and the closed ring prestressed steel bar 4, so that the tied galvanized steel wire mesh 2 is in a taut state to form an external tension force toward the pipe wall, and forms a prestressed steel bar shield with the closed ring prestressed steel bar 4 that can resist the initial annular pressure, so as to resist the creep and gravity degassing of the repair concrete material, and enhance the bonding effect of the repair material;

[0045] S5, spraying cement slurry on the inner wall of the pipeline, and then plastering and repairing with polymer mortar 5 in layers, and using tire support plates 6 and adjustable support frames 7 to support the tire in layers and blocks during the hardening process of the polymer mortar 5;

[0046] S6. When the strength of the surface polymer mortar 5 reaches 70%, remove the tire support plate 6 and the adjustable support frame 7. According to the strength test data, remove the tire support plate 6 of the surface polymer mortar 5 48h to 72h after plastering the surface polymer mortar 5, then grind the surface of the joint and clean up the fallen residues, and cure until the strength value of the polymer mortar 5 reaches 100%. For example, adopt room temperature curing, monitor the humidity at any time during curing, and spray curing when the humidity is lower than 90%.

[0047] Example 2

[0048] like Figure 1 , Figure 2 As shown, this embodiment is a further improvement on the basis of embodiment 1, and the details are as follows:

[0049] If the quality of the surface pretreatment of the inner wall of the concrete drainage pipe 1 to be repaired in S1 is not good, it is very easy to cause the repair failure. In this embodiment, the surface pretreatment includes: cleaning scale, removing the carbonized layer and roughening the surface, wherein the cleaning of scale adopts a high-pressure water cleaning vehicle, the carbonized layer is removed by manual or mechanical methods, and the roughening adopts sandblasting or shot blasting to achieve the roughness that is convenient for the subsequent plaster layer to adhere; the repair and chiseling adopts an electric pick or a pneumatic pick to make the surface repair polymer mortar reach an appropriate depth.

[0050] Before cleaning the scale on the pipeline, the adjacent pipe sections of the pipe section are first sealed with air bags. After draining the water and desilting, a drainage pipe cleaning vehicle is used for high-pressure cleaning.

[0051] If the inner wall of the concrete drainage pipe 1 is severely peeled off and the original pipe concrete pebble aggregate is completely exposed, in order to ensure the bonding effect of the plaster layer, quartz sand is used for sandblasting and roughening. The holes are first repaired with hanging wire mesh and then with polymer mortar, and a layer of carbon fiber cloth is added on the surface to prevent water from seeping in due to shrinkage cracks at the holes.

[0052] For plastering thickness not more than 10mm, it should be chiseled until the plastering thickness is not less than 10mm; the holes are repaired by manually repairing the pipe holes with polymer mortar 5 or mortar hanging net at the holes.

[0053] Example 3

[0054] like Figure 2 As shown, this embodiment is a further improvement on the basis of Embodiment 1 or 2, and the details are as follows:

[0055] The overlap width between the galvanized steel wire mesh 2 laid on the inner wall of the pipe in S2 is not less than 100mm. The end of the galvanized steel wire mesh 2 in the axial direction of the pipe is buried in a shallow groove and fixed at the end. For example, the width of the shallow groove can be 30mm, the depth is 20mm, the center of the shallow groove is 60mm away from the pipe end, choose a 10×10×0.6mm galvanized steel wire mesh, and fix it with cement nails.

[0056] Example 4

[0057] like Figures 1 to 4 As shown, this embodiment is a further improvement on any one of Embodiments 1 to 3, and the details are as follows:

[0058] The processing method of the closed ring prestressed steel bar 4 in S3 is as follows:

[0059] The steel wire rod is cut into two sections according to the inner circumference of the pipeline, and is divided into upper and lower sections of prestressed tendons 410. The two front ends of each section of prestressed tendons 410 are straightened and threaded, and then the two ends of the upper and lower sections of prestressed tendons 410 are fully connected by threading with a positive and negative thread connecting sleeve 420 to form a closed ring prestressed steel bar 4. The closed ring prestressed steel bar 4 can be adjusted to generate a predetermined compressive stress by rotating the positive and negative thread connecting sleeve 420. The steel bar joints between two adjacent closed ring prestressed steel bars 4 in all closed ring prestressed steel bars 4 arranged in the pipeline are staggered in the circumferential position of the pipeline. For example, the inner diameter of the pipeline is 1200mm, the steel bar is a round bar with a diameter of 6mm, the spacing between the closed ring prestressed steel bars 4 is 150mm, the length of the positive and negative thread connecting sleeve 420 is 70mm, and the prestress is the torque of the positive and negative thread connecting sleeve 420 is 13.5Nm.

[0060] If the concrete drainage pipe 1 is a circular pipe, then the closed ring prestressed steel bar 4 is circular, and the upper and lower sections of prestressed steel bars 410 are semicircular. If the concrete drainage pipe 1 is a special-shaped pipe or a rectangular pipe, then the closed ring prestressed steel bar 4 is special-shaped or rectangular.

[0061] Two adjacent closed-loop prestressed steel bars 4 among all closed-loop prestressed steel bars 4 are connected by longitudinal ribbed steel bars along the inner wall of the original pipeline in the direction of the pipeline axis.

[0062] When the upper and lower sections of prestressed tendons 410 are combined into a closed ring prestressed steel bar 4 through the positive and negative wire connecting sleeve 420, the plane of the closed ring prestressed steel bar 4 is obliquely intersected with the pipeline axis. The upper and lower sections of prestressed tendons 410 are connected to the positive and negative wire connecting sleeve 420 and then pushed into the installation position.

[0063] Creep causes the deformation of concrete structures to increase, which is detrimental to the structure. For example, it increases the deflection of bending members, which is particularly obvious in the upper part of the circular reinforcement. If no measures are taken, the upper part of the reinforcement will be detached from the original inner wall of the pipe under the action of creep and gravity to form a cavity. When there is groundwater outside the pipe, the air bubbles attached to the cavity will burst under the vibration of road vehicles, thereby causing damage to the reinforcement structure. For the reinforcement steel bars on the inner wall of the pipe, a positive and negative wire connecting sleeve 420 is used to apply prestress to the upper and lower sections of prestressed tendons 410 arranged circumferentially, so that the closed ring prestressed steel bars 4 have a certain external arch force, forming a shield structure with external arch force, which can effectively overcome the influence of creep and gravity and also play a certain anti-cracking role.

[0064] The mortar pad 3 can make the closed ring prestressed steel bar 4 be located in the middle of the polymer mortar 5, so that the prestressed steel bar shield can play a better role and form a steel bar protective layer at the same time.

[0065] Use a ruler to measure the inner diameter, inner circumference and other parameters of the pipe to be repaired, and the measurement process is carried out after surface pretreatment.

[0066] Example 5

[0067] like Figure 2 As shown, this embodiment is a further improvement on any one of Embodiments 1 to 4, and the details are as follows:

[0068] In S4, tying and positioning the galvanized steel wire mesh 2 and the closed-loop prestressed steel bars 4 specifically refers to: tying and positioning the closed-loop prestressed steel bars 4 and the galvanized steel wire mesh 2 with a tie wire at a position deviating from the mortar pad 3. Since a mortar pad 3 is provided between the closed-loop prestressed steel bars 4 and the inner wall of the pipe, the galvanized steel wire mesh 2 and the closed-loop prestressed steel bars 4 are separated by the mortar pad 3, so a position deviating from the mortar pad 3 is selected for tying.

[0069] Example 6

[0070] like Figure 2 As shown, this embodiment is a further improvement on any one of Embodiments 1 to 5, and the details are as follows:

[0071] In S5, before spraying cement slurry, if the surface moisture content of the pipe wall is small, such as ≤4%, sprinkle water to moisten it. Wait until the surface is dry, such as if the surface moisture content is ≤6%, before plastering construction can be carried out. When plastering in layers, wait until the previous layer of mortar is finally set before plastering the next layer, and the circumferential gaps between layers should be staggered.

[0072] The layered polymer mortar 5 plastering in S5 includes: using layered mortar plastering in the center upper half of the pipe cross section, and using fine stone concrete for one-time pouring or fine stone concrete + surface polymer mortar in the center lower half of the pipe cross section, and also includes a solution in which the total plastering thickness is only one layer of polymer mortar.

[0073] Before the surface polymer mortar 5 in S5 is supported, a permeable template cloth is pasted on the surface of the tire support plate 6. The number of layers of the permeable template cloth can be one layer. If the total thickness of the plastering polymer mortar 5 is ≥30mm, a layer of hanging mesh is added before the construction of the surface polymer mortar 5. For example, the repair thickness of the polymer mortar 5 is 30mm, and the plastering is constructed in three layers, each layer is 10mm. In order to stagger the second layer of plastering, the width of the first and last tire support plates 6 of the second layer is 150mm, and the rest are 300mm wide. The tire support plates 6 are removed 8-10h after the first or second layer of plastering to proceed to the next step of construction.

[0074] The tire support plate 6 in S5 is an elastic plate. When the elastic plate is supported to the pipe diameter, the pressure it can provide is ≥0.1Mpa and <0.5Mpa. The tire support plate 6 is made of metal or plastic. If the concrete drainage pipe 1 is a circular pipe, then the tire support plate 6 in S5 is an arc-shaped elastic plate with an arc radius greater than the radius of the concrete drainage pipe 1 to be repaired. When the arc-shaped elastic plate is supported to the pipe diameter, the pressure it can provide is ≥0.1Mpa and <0.5Mpa. The tire support plate 6 is made of metal or plastic. For example, the tire support plate 6 is a 1.5mm thick and 300mm wide cold-rolled steel plate that has been rolled. If the concrete drainage pipe 1 is a special-shaped pipe or a rectangular pipe, then the shape of the tire support plate 6 will change accordingly.

[0075] When there is a gap between the joints of the upper and lower tire support plates 6, the tire support plates 6 of the same material and width can be temporarily used for padding; arc-shaped fir board strips are used at the expansion joints as side templates for the repair mortar for support. At the same time, a layer of permeable template cloth pasted on the surface of the tire support plate 6 during the construction of the mortar surface layer is used to absorb excess moisture in the mortar through the template cloth and the fir board, and at the same time, water seepage from the pipe wall can also be discharged. After the mortar solidifies, a hardened layer with a thickness of about 2 mm can be formed on its surface, which plays a role in resisting erosion and wear.

[0076] For example, the adjustable support frame 7 is made of wood squares and wooden wedges, and the length is adjusted on site for support. The horizontal support effect of each support is checked on site, and the support is increased laterally if necessary. Before the construction of the surface polymer mortar, a 10×10×0.6mm galvanized steel wire mesh is added.

[0077] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A trenchless repair method for prestressed reinforcement shield of concrete drainage pipes, characterized in that: The steps include: S1. Pre-treat the inner wall of the concrete drainage pipe (1) to be repaired, chisel the inner wall of the pipe until the repair polymer mortar reaches an appropriate depth, repair the hole, and dig a shallow groove along the circumference of the end of the pipe for placing the end of the galvanized steel wire mesh (2); S2, laying a galvanized steel wire mesh (2) on the inner wall of the pipeline along the pipeline axis and fixing it; S3, adding a mortar pad (3) as a support to the inner wall of the pipeline, and installing a plurality of closed-loop prestressed steel bars (4) at a predetermined interval along the axis of the pipeline, and then adjusting the closed-loop prestressed steel bars (4) to generate a predetermined compressive stress; S4, tying the galvanized steel wire mesh (2) and the closed ring prestressed steel bar (4) to position them, so that the tied galvanized steel wire mesh (2) is in a taut state to form an external tension force toward the pipe wall, and forms a prestressed steel bar shield with the closed ring prestressed steel bar (4) that can resist the initial annular pressure; S5, spraying cement slurry on the inner wall of the pipeline, and then plastering and repairing it in layers with polymer mortar (5), and using tire support plates (6) and adjustable support frames (7) to support the tire in layers and blocks during the hardening process of the polymer mortar (5); S6, removing the tire support plate (6) and the adjustable support frame (7), and curing the polymer mortar (5).

2. A trenchless repair method for prestressed reinforcement shields for concrete drainage pipes according to claim 1, characterized in that: The surface pretreatment in S1 includes: cleaning scale, removing carbonized layer and roughening the surface. Among them, high-pressure water cleaning vehicle is used for cleaning scale, manual or mechanical methods are used for removing carbonized layer, and sandblasting or shot blasting is used for roughening to achieve the roughness that is convenient for the subsequent plaster layer to adhere. Electric pick or pneumatic pick is used for chiseling to make the surface repair polymer mortar reach an appropriate depth.

3. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: In S1, if the plaster thickness is not more than 10 mm, the thickness should be chiseled until the plaster thickness is not less than 10 mm; the holes are repaired by using polymer mortar (5) or mortar mesh to repair the holes in the pipes.

4. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: The overlap width between the mesh pieces of the galvanized steel wire mesh (2) laid on the inner wall of the pipeline in S2 is not less than 100 mm, and the end of the galvanized steel wire mesh (2) in the pipeline axis direction is buried in a shallow groove and is densely fixed at the end.

5. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: The processing method of the closed ring prestressed steel bar (4) in S3 is as follows: the steel bar wire rod is cut into two sections according to the inner circumference of the pipeline, and is divided into upper and lower sections of prestressed steel bars (410); the two front ends of each section of prestressed steel bars (410) are straightened and threaded; the two ends of the upper and lower sections of prestressed steel bars (410) are fully threaded with a positive and negative thread connection sleeve (420) to form a closed ring prestressed steel bar (4); the closed ring prestressed steel bar (4) can be adjusted to generate a predetermined compressive stress by rotating the positive and negative thread connection sleeve (420); and the steel bar joints between two adjacent closed ring prestressed steel bars (4) are staggered in the circumferential position of the pipeline.

6. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: In S5, if the surface moisture content of the pipe wall is ≤4% before spraying cement slurry, sprinkle water to moisten it. When the surface moisture content is ≤6%, plastering construction can be carried out. When plastering in layers, wait until the previous layer of mortar is finally set before plastering the next layer, and the circumferential gaps between layers should be staggered.

7. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: The layered polymer mortar (5) plastering in S5 includes: using layered mortar plastering in the center upper half of the pipe cross section, and using fine stone concrete for one-time pouring or fine stone concrete + surface polymer mortar in the center lower half of the pipe cross section, and also includes a solution in which the total plastering thickness is only one layer of polymer mortar.

8. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: In S5, before the surface polymer mortar (5) is supported, a permeable template cloth is pasted on the surface of the support plate (6). If the total thickness of the plastering polymer mortar (5) is ≥30mm, a layer of hanging mesh is added before the construction of the surface polymer mortar (5).

9. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: The tire support plate (6) in S5 is an elastic plate. When the elastic plate is supported to the diameter of the pipe, the pressure it can provide is ≥0.1Mpa and <0.5Mpa.

10. The method for trenchless repair of prestressed reinforcement shield for concrete drainage pipe according to claim 1, characterized in that: If there is a gap between the joints of the upper and lower tire support plates (6) in S5, a tire support plate (6) of the same material and width can be used as a temporary cushion; arc-shaped fir board strips are used as side templates for repair mortar at the expansion joints for support, and a layer of permeable template cloth pasted on the surface of the tire support plate (6) during the construction of the mortar surface layer is used to absorb excess water in the mortar through the template cloth and the fir board, and at the same time, water seepage from the pipe wall can be discharged, and a hardened layer can be formed on the surface of the mortar after solidification.

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