High-performance mortar tunnel in-situ 3D printing repairing method based on laser radar scanning modeling

Abstract

The invention discloses a high-performance mortar tunnel in-situ 3D printing repairing method based on laser radar scanning modeling, which comprises the following steps: step 1, scanning a defect part by a three-dimensional laser scanner to obtain original point cloud data; merging the original point cloud data into an overall point cloud number, and drawing a three-dimensional model of the defect part according to the overall point cloud data; 2, importing a file exported from the three-dimensional model of the defect part in the step 1 into a 3D printer to run; step 3, cleaning the surface of the defect part and brushing an adhesion agent; fourthly, high-performance repairing mortar is printed to the vacant position to be repaired in a layered mode at the in-situ position of the tunnel defect part through a 3D printer, and the defect part is completely filled till the defect part is flush with the original surface; and finally, covering the outer surface of the mortar with a plastic film, and fully curing to a corresponding age to finish repairing. The method overcomes the potential safety hazard that the overall 3D printing in-situ repair block is low in bonding strength with a damaged interface and is easy to fall off.

Description

Technical Field

[0001] This invention belongs to the field of tunnel damage repair technology, specifically involving a high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling. Background Technology

[0002] Complex and changeable climate and harsh geological conditions often cause tunnel lining cracks and frost heave damage, seriously impairing the safety of tunnel transportation. Existing tunnel reinforcement methods generally suffer from drawbacks such as high professional requirements, high construction intensity, high cost, long cycle, and poor durability. There is an urgent need to develop a new tunnel repair method to solve these problems.

[0003] Currently, common tunnel reinforcement and repair technologies can be divided into two main categories: internal lining surface reinforcement and external surrounding rock (or soil) grouting reinforcement. Internal lining surface reinforcement technologies include shotcrete reinforcement and arched hoop reinforcement, which aim to improve the overall strength and stiffness of the tunnel lining structure. After implementing internal lining surface reinforcement, the cross-sectional dimensions of the tunnel lining structure will increase, which will adversely affect the tunnel clearance. External surrounding rock (or soil) grouting reinforcement technology, on the other hand, directly seals cracks in the surrounding rock, fills cavities behind the lining, and addresses water leakage. External surrounding rock grouting reinforcement technology is highly dependent on the surrounding rock conditions, and the construction process is relatively complex, significantly impacting traffic operation. Improper grouting methods may not only fail to effectively treat the damage but could also exacerbate it. Summary of the Invention

[0004] The purpose of this invention is to provide a high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling, which overcomes the safety hazards of low bonding strength between the integral 3D printed in-situ repair block and the damaged interface, and easy detachment of the whole block.

[0005] This invention adopts the following technical solution: a high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling, comprising the following steps:

[0006] Step 1: Set up a 3D laser scanner at the lining defect in the tunnel and on the central axis of the tunnel section at the defect location to scan the defect and obtain the original point cloud data.

[0007] The original point cloud data are merged into a whole point cloud, and the whole point cloud data is used to draw a three-dimensional model of the missing part.

[0008] Step 2: Import the exported 3D model file of the missing part from Step 1 into the 3D printer and run it;

[0009] Step 3: Clean the surface of the damaged area and apply a bonding agent;

[0010] Step 4: Using a 3D printer, print high-performance repair mortar in layers to the area to be repaired at the original location of the tunnel defect, completely filling the defect until it is level with the original surface; finally, cover the outer surface of the mortar with a plastic film and allow it to cure fully to the appropriate age to complete the repair.

[0011] Furthermore, in step one, the scanning process is as follows: along the tunnel's central axis, a scanning station is set up at intervals of 5 to 10 meters before and after the defective part; additional scanning stations are set up within a 1 to 2-meter radius around the defective part; and a three-dimensional laser scanner is used to scan each scanning station.

[0012] Further, in step two, the specific process is as follows: the three-dimensional model of the missing part in step one is exported as an STL format file, and then the STL format file is imported into the UltiMaker Cura path planning software to obtain a path planning file, which is saved as a GCode format file. The file is imported into the 3D printer program compilation software, and after automatic compilation and simulation, an encoding file can be output. The encoding is exported as a MOD file, and this file is imported into the 3D printer to run.

[0013] Furthermore, the high-performance repair mortar comprises the following components in parts by weight: 961.8 parts cement, 83.6 parts silica fume, 209.1 parts water, 1045.5 parts quartz sand, 10.5 parts crystal nucleation early strength agent, 15.7 parts polycarboxylate superplasticizer, and 31.4 parts quick-setting agent.

[0014] The beneficial effects of this invention are as follows: By using high-performance repair mortar, 3D printing is performed directly at the in-situ location of tunnel damage to fill the gaps in layers. This not only overcomes the shortcomings of traditional mortar spraying repair methods, such as insufficient precision and aesthetics, but also eliminates the safety hazards of low bonding strength between the integral 3D printed in-situ repair block and the damaged interface, leading to easy detachment of the entire block. Furthermore, this method features small construction scale, high degree of automation, simple operation, material saving, and no impact on tunnel clearance, saving time consumed by conventional construction steps such as formwork erection, vibration, and formwork removal. Detailed Implementation

[0015] The present invention will now be described in detail with reference to specific embodiments.

[0016] This invention discloses a high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling, comprising the following steps:

[0017] Step 1: The 3D laser scanner is set to medium resolution and anti-interference mode and fixed on the central axis of the tunnel section at the defective part of the tunnel lining. The scanner is erected at a height of 1.5–2 meters and leveled. Scanning stations are set up at intervals of 5–10 meters before and after the defect, ensuring an overlap rate of ≥30% between the two stations. Additional scanning stations are set up within a 1–2 meter radius of the defect area. Each station is scanned for 5–10 minutes to obtain raw point cloud data. The raw point cloud data is then denoised to remove noise points caused by dust and vibration. Data from multiple stations is then stitched together using feature points or targets in the overlapping area to form a unified point cloud. Finally, the obtained unified point cloud data is used to create a 3D model of the defective area using software such as CloudCompare or Geomagic Wrap.

[0018] Step 2: Export the 3D model of the missing part from Step 1 as an STL file using software. Import this file into the UltraMaker Cura path planning software, adjust printing parameters such as mass, walls, top, infill, and speed to obtain a path planning file, and save it as a GCode file. Import this file into the 3D printer program compilation software. After automatic compilation and simulation, an encoded file will be output. Export the encoded file as a MOD file, import this file into the 3D printer, and run it to achieve automatic printing.

[0019] Step 3: Clean the surface of the damaged area and apply an interface agent to improve the adhesion between the first layer of repair mortar and the interface to be repaired;

[0020] Step 4: Using a 3D printer, high-performance repair mortar is printed layer by layer to the missing area in the original location of the tunnel defect, completely filling the defect until it is level with the original surface; finally, a plastic film is covered on the outer surface of the mortar, and the repair work is completed after it has been fully cured to the appropriate age.

[0021] The preparation method of the above-mentioned high-performance repair mortar is as follows:

[0022] At room temperature (24℃), dry powders of cement, silica fume, and quartz sand are slowly dry-mixed for 1 minute using a planetary cement mortar mixer to ensure thorough and uniform mixing, thus reducing silica fume agglomeration. In another mixing pot, a compound mixing water containing water, polycarboxylate (PCE) water-reducing agent, nucleation agent, and accelerator is added, followed by the powder material. The mixture is then slowly stirred for 1 minute until the powder and water are essentially mixed into a slurry. After a 90-second pause, the material adhering to the mixing blades and the inner wall of the container is scraped into the container. The mixture is then switched to a high-speed mixing setting, with a high-speed mixing time of 2 minutes. Once mixing is complete, the repair mortar is poured into a 3D printer for subsequent mortar printing and repair operations.

[0023] The mix proportions of high-performance repair mortar are as follows:

[0024]

[0025]

[0026] Mortar performance testing methods:

[0027] The compressive strength, flexural strength, and setting time of the repair mortar printed under this mix proportion were determined according to the standards of "GBT 17671-2021 Cement Mortar Strength Test Method (ISO Method)", "JGJ 70-90 Basic Performance Test Method of Building Mortar", and "GB / T 2419-2005 Cement Mortar Flowability Test Method". The test results are as follows:

[0028] Flexural strength (MPa) of repair mortar at various ages:

[0029] serial number 1d 2d 28d ① 12.4 15.4 20.7 ② 12.2 14.7 17.1 ③ 14.5 16.7 21.1 ④ 12.2 15.7 19.8 ⑤ 11.9 14.8 18.5 ⑥ 12.3 15.2 20.1 ⑦ 11.8 14.9 18.4 ⑧ 12.5 15.1 20.3

[0030] Compressive strength (MPa) of repair mortar at various ages:

[0031] serial number 8h 1d 2d 28d ① 44.7 63.7 69.0 94.6 ② 39.5 56.3 67.1 91.7 ③ 49.8 68.5 74.4 94.4 ④ 46.2 65.2 68.1 93.6 ⑤ 42.1 61.8 66.9 89.3 ⑥ 44.2 62.3 68.8 92.5 ⑦ 41.3 60.9 68.2 93.3 ⑧ 45.9 64.8 68.7 94.1

[0032] Repair mortar flowability (mm):

[0033] serial number ① ② ③ ④ ⑤ ⑥ ⑦ ⑧ Flowability 220 256 215 209 229 224 243 211

[0034] Repair mortar setting time (min):

[0035] serial number ① ② ③ ④ ⑤ ⑥ ⑦ ⑧ Condensation time 143 188 121 30 145 146 172 60

[0036] To further verify the technical solution and advantages of this invention, specific examples will be used to supplement the explanation of different mix proportions of the high-performance repair mortar and their corresponding workability:

[0037] Example 1

[0038] In this embodiment, the high-performance repair mortar is formulated as follows: 961.8 parts of P·II 52.5R cement, 83.6 parts of silica fume, 209.1 parts of water, 1045.5 parts of quartz sand, 10.5 parts of crystal nucleation early strength agent, and 15.7 parts of polycarboxylate superplasticizer.

[0039] High-performance repair mortar was prepared according to the method of this invention. The compressive / flexural strength, setting time, and fluidity of the repair mortar printed under this mix ratio were measured: 1-day flexural strength 12.4 MPa, 2-day flexural strength 15.4 MPa, 28-day flexural strength 20.7 MPa; 8-hour compressive strength 44.7 MPa, 1-day compressive strength 63.7 MPa, 2-day compressive strength 69.0 MPa, 28-day compressive strength 94.6 MPa; the mortar setting time was 143 min, and the fluidity was 220 mm.

[0040] Under this ratio, the high-performance repair mortar is applied to 3D printed tunnel repair. Its strength meets the performance indicators, its setting time is short, and its fluidity is moderate, making it suitable for conventional 3D printed tunnel repair.

[0041] Example 2

[0042] In this embodiment, the high-performance repair mortar uses a high water-reducing agent dosage, with the following formulation: 940.9 parts of P·II 52.5R cement, 104.5 parts of silica fume, 209.1 parts of water, 1045.5 parts of quartz sand, 10.5 parts of crystal nucleation early strength agent, and 26.1 parts of polycarboxylate water-reducing agent.

[0043] High-performance repair mortar was prepared according to the method of this invention. The compressive / flexural strength, setting time, and fluidity of the repair mortar printed under this mix ratio were measured: 1-day flexural strength 12.2 MPa, 2-day flexural strength 14.7 MPa, 28-day flexural strength 17.1 MPa; 8-hour compressive strength 39.5 MPa, 1-day compressive strength 56.3 MPa, 2-day compressive strength 67.1 MPa, 28-day compressive strength 91.7 MPa; mortar setting time was 188 min, and fluidity was 256 mm.

[0044] When the high-performance repair mortar in this embodiment is applied to 3D printing mortar repair, it can be seen that: with a high water-reducing agent content, the fluidity of the repair mortar increases significantly and the viscosity increases, but the setting time is prolonged under the action of the water-reducing agent, and the compressive and flexural strengths at all ages are slightly lower than the standard mix ratio; the high fluidity characteristics of the high-performance repair mortar in this embodiment make it suitable for fine 3D printing repair of micro-cracks in tunnels.

[0045] Example 3

[0046] In this embodiment, the high-performance repair mortar uses a high early strength agent dosage, with the following composition: 961.8 parts of P·II 52.5R cement, 83.6 parts of silica fume, 209.1 parts of water, 1045.5 parts of quartz sand, 15.6 parts of crystal nucleation early strength agent, and 15.7 parts of polycarboxylate superplasticizer.

[0047] High-performance repair mortar was prepared according to the method of this invention. The compressive / flexural strength, setting time, and fluidity of the repair mortar printed under this mix proportion were measured: the 1-day flexural strength of mix proportion ③ was 14.5 MPa, the 2-day flexural strength was 16.7 MPa, and the 28-day flexural strength was 21.1 MPa; the 8-hour compressive strength was 49.8 MPa, the 1-day compressive strength was 68.5 MPa, the 2-day compressive strength was 74.4 MPa, and the 28-day compressive strength was 94.4 MPa; the mortar setting time was 121 min, and the fluidity was 215 mm.

[0048] When the high-performance repair mortar in this embodiment is applied to 3D printing mortar repair, it can be seen that: under the high nucleation early strength agent dosage ratio, the setting time of the repair mortar is significantly shortened, the fluidity decreases, the early compressive and flexural strengths are significantly increased, and the 28-day strength does not change significantly; this ratio is suitable for rapid and emergency repairs of important projects; however, it should be noted that excessively high nucleation early strength agent dosage will lead to a sharp increase in the early hydration rate of cement and an increase in heat release, thereby causing adverse effects such as structural expansion and cracking.

[0049] Example 4

[0050] In this embodiment, an accelerator is added, and the proportions are as follows: 961.8 parts of P·II 52.5R cement, 83.6 parts of silica fume, 209.1 parts of water, 1045.5 parts of quartz sand, 10.5 parts of crystal nucleation early strength agent, 15.7 parts of polycarboxylate superplasticizer, and 31.4 parts of accelerator.

[0051] High-performance repair mortar was prepared according to the method of this invention. The compressive / flexural strength, setting time, and fluidity of the repair mortar printed under this mix proportion were measured: 1-day flexural strength 12.2 MPa, 2-day flexural strength 15.7 MPa, 28-day flexural strength 19.8 MPa; 8-hour compressive strength 46.2 MPa, 1-day compressive strength 65.2 MPa, 2-day compressive strength 70.1 MPa, 28-day compressive strength 94.0 MPa; the mortar fluidity was 209 mm, and it could achieve initial setting in 30 minutes.

[0052] Applying the high-performance repair mortar in this embodiment to 3D printing mortar repair demonstrates that the quick-setting agent can improve the early strength of the material while having almost no impact on later strength development. This formulation is suitable for projects requiring rapid repair, and its rapid setting characteristics give the repair mortar excellent anti-sagging properties, allowing it to adhere tightly to the damaged areas of the tunnel after 3D printing.

[0053] Taking a certain tunnel as an example, the specific steps for repairing a damaged section are as follows:

[0054] Step 1: Fix the scanner on a tripod and set up a scanning station at intervals of 5 to 10 meters before and after the defect location along the tunnel axis. Scan to obtain a three-dimensional model of the damaged or defective part inside the tunnel; obtain an irregular three-dimensional shape of the defect with a maximum length of 65cm, a maximum width of 43cm, and a maximum depth of 34cm.

[0055] Step 2: Export the 3D model of the missing part from Step 1 as an STL file using software. Import this file into the UltraMaker Cura path planning software, adjust printing parameters such as mass, walls, top, infill, and speed to obtain a path planning file, and save it as a Gcode file. Import the file into the corresponding program on the 3D printer.

[0056] Step 3: Clean the damaged surface and apply an interface agent to improve the adhesion between the first layer of repair mortar and the interface to be repaired;

[0057] The high-performance repair mortar comprises the following components in parts by weight: 1003.6 parts cement, 41.8 parts silica fume, 162.7 parts water, 1045.5 parts sand, 48.5 parts crystal nucleation early strength agent, and 10.5 parts water-reducing agent.

[0058] The performance indicators of the prepared high-performance repair mortar are as follows:

[0059] 8-hour compressive strength ≥ 15 MPa; 1-day compressive strength ≥ 40 MPa, 1-day flexural strength ≥ 7 MPa; 2-day compressive strength ≥ 60 MPa, 2-day flexural strength ≥ 10 MPa; 28-day compressive strength ≥ 80 MPa, 28-day flexural strength ≥ 14 MPa.

[0060] Step 4: Directly use 3D printer 1 to print high-performance repair mortar 2 in layers to the missing area to be repaired at the original site of the tunnel damage, completely filling the defect to be level with the original surface; that is, the maximum length of the filled repair mortar is 65cm, the maximum width is 43cm, and the maximum depth is 34cm.

[0061] Step 5: Cover the outer surface of the high-performance repair mortar 2 with a plastic film and allow it to cure fully to the appropriate age to complete the repair work.

[0062] The types and dosage ranges of materials in the high-performance repair mortar mix proportion of this invention are as follows: P·II 52.5R cement, 92% pure silica fume, polycarboxylate superplasticizer, and nucleation accelerator. The water-cement ratio is 0.2, the mortar-cement ratio is 1.0, the silica fume content of cement is 4.0–10.0%, the water superplasticizer content of cementitious materials is 1.5–2.5%, the nucleation accelerator content of cementitious materials is 1.0–1.5%, and the accelerator content of cementitious materials is 0–3.0%. Silica fume acts as a compact filler, with an optimal dosage of 8%. The dosage of water superplasticizer can be adjusted flexibly according to the actual project, but excessive water superplasticizer can cause bleeding and delayed setting. Both the nucleation accelerator and the accelerator accelerate the early hydration of cement and improve early strength; their specific dosages can be adjusted flexibly within the recommended range according to the actual project.

[0063] As an example, the composition includes 961.8 parts cement, 83.6 parts silica fume, 209.1 parts water, 1045.5 parts quartz sand, 10.5 parts crystal nucleation early strength agent, 15.7 parts polycarboxylate superplasticizer, and 31.4 parts quick-setting agent.

[0064] The high-performance repair mortar is directly 3D printed and layered to fill the tunnel damage in situ. This not only overcomes the shortcomings of traditional mortar spraying repair methods in terms of precision and aesthetics, but also overcomes the safety hazards of low bonding strength between the overall 3D printed in-situ repair block and the damaged interface, which makes it easy for the whole block to fall off.

Claims

1. A high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling, characterized in that, Includes the following steps: Step 1: Set up a 3D laser scanner at the lining defect in the tunnel and on the central axis of the tunnel section at the defect location to scan the defect and obtain the original point cloud data. The original point cloud data are merged into a whole point cloud, and the whole point cloud data is used to draw a three-dimensional model of the missing part. Step 2: Import the exported 3D model file of the missing part from Step 1 into the 3D printer and run it; Step 3: Clean the surface of the damaged area and apply a bonding agent; Step 4: Using a 3D printer, print high-performance repair mortar in layers to the area to be repaired at the original location of the tunnel defect, completely filling the defect until it is level with the original surface; finally, cover the outer surface of the mortar with a plastic film and allow it to cure fully to the appropriate age to complete the repair.

2. The high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling as described in claim 1, characterized in that, In step one, the scanning process is as follows: along the tunnel's central axis, a scanning station is set up at intervals of 5 to 10 meters before and after the defective part; additional scanning stations are set up within a 1 to 2-meter radius around the defective part; and a three-dimensional laser scanner is used to scan each scanning station.

3. The high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling as described in claim 2, characterized in that, In step two, the specific process is as follows: the three-dimensional model of the missing part in step one is exported as an STL format file, and then the STL format file is imported into the UltiMaker Cura path planning software to obtain a path planning file, which is saved as a GCode format file. The file is imported into the 3D printer program compilation software, and after automatic compilation and simulation, an encoding file can be output. The encoding is exported as a MOD file, and this file is imported into the 3D printer to run.

4. The high-performance in-situ 3D printing repair method for mortar tunnels based on lidar scanning modeling as described in claim 3, characterized in that, The high-performance repair mortar comprises the following components in parts by weight: 961.8 parts cement, 83.6 parts silica fume, 209.1 parts water, 1045.5 parts quartz sand, 10.5 parts crystal nucleation early strength agent, 15.7 parts polycarboxylate superplasticizer, and 31.4 parts quick-setting agent.

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