Frontal tool changing method in narrow space micro shield hole

Abstract

The application provides a method for front-face cutter replacement in a narrow-space micro-shield hole, and relates to the technical field of shield construction, and comprises the following steps: three-layer protection of internal support fixation, gap filling and external protection isolation is performed on a shield tail brush; a water stop ring is filled in a gap between a shield body 10-15 m behind the shield tail and a hole wall, so as to form a water stop barrier; and the shield machine is retreated by a predetermined stroke through staged recovery of a pushing oil cylinder and posture adjustment of an articulated oil cylinder, so as to form a cutter replacement operation space in front of the cutter head. Through optimization of the connection process of shield retreat, protection and water stop procedures, the application reduces the waiting time between procedures, the water stop ring is assembled in a modularized mode, the shield tail brush is protected by using a prefabricated protection component, the operation time in the hole is greatly shortened, and the construction period is saved by more than 20% compared with the traditional cutter replacement process.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine (TBM) construction technology, specifically a method for frontal cutter replacement in a confined space within a micro-shield tunnel. Background Technology

[0002] During shield tunneling, the cutterhead often jams due to complex geology, cutter wear or damage. Cutter replacement at the front of the tunnel is a key operation to resume shield tunneling. However, the working environment for cutter replacement at the front is characterized by enclosed space, limited ventilation, narrow working face, and high safety risks.

[0003] Traditional cutterhead replacement requires manual excavation to allow personnel to enter the working space directly in front of the cutterhead. Because there are no specific technical measures for shield machine retreat control, shield tail brush protection, and water-stop ring construction, problems such as shield tail seal failure, face instability, and groundwater leakage are easily caused, seriously affecting the safety and efficiency of cutterhead replacement construction. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for frontal cutter replacement in confined spaces within micro-shield tunnels. This method solves the problems of high construction safety risks and low efficiency caused by the lack of specific technical measures in existing frontal cutter replacement construction within shield tunnels, which can easily lead to face instability, shield tail seal failure, and groundwater leakage.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The method for frontal cutterhead replacement in a confined space micro-shield tunnel includes the following steps:

[0007] Step 1: Construction Preparation

[0008] Clean up the working area inside the tunnel, configure and check the necessary personnel, equipment and materials, install ventilation, lighting and safety monitoring systems, and carry out advance reinforcement of the working face and set up monitoring points;

[0009] Step 2: Multi-layer protection construction at the tail of the shield

[0010] The shield tail brush is protected by three layers: internal support and fixation, gap filling, and external protection and isolation.

[0011] Step 3: Fill the hole with a water-stopping ring

[0012] Fill the gap between the shield and the tunnel wall 10-15m behind the shield tail with a water-stopping ring to form a water-stopping barrier.

[0013] Step 4: Tunnel Boring Machine Reverses

[0014] By advancing the hydraulic cylinder for graded recovery and adjusting the attitude of the articulated hydraulic cylinder, the tunnel boring machine can retreat a predetermined distance, creating a space for cutting tool changing in front of the cutterhead.

[0015] Step 5: Tool Change Operation

[0016] Tool box inspection, tool replacement, and welding operations are performed in the tool changing work area.

[0017] Step Six: Removal of Protective Components and Repositioning of the Tunnel Boring Machine

[0018] After the cutterhead replacement is accepted and approved, the tail shield brush protective components are removed, and the tunnel boring machine is reset by extending the propulsion cylinders in stages.

[0019] Preferably, step two: multi-layer protective construction at the tail of the shield, specifically as follows:

[0020] Internal support fixing: Precast steel internal support components are evenly arranged along the annular direction of the shield tail brush, and the internal support components are fixed to the inner wall of the shield tail with fastening bolts to support the shield tail brush to maintain its original opening angle;

[0021] Gap filling: Water-swellable rubber strips are continuously laid in a ring within the gap of the tail brush, with the filling depth reaching the root of the tail brush.

[0022] External protective isolation: A wear-resistant protective plate is laid along the ring outside the tail shield brush, and the wear-resistant protective plate is fixed to the tail shield steel plate, completely covering the tail shield brush area and isolating the tunnel wall debris and other materials from contact with the tail shield brush.

[0023] Preferably, step three: filling the hole with a water-stop ring, specifically:

[0024] Install grouting ball valves on the pre-reserved grouting holes of the tunnel segments;

[0025] Preparation of rapid-setting cement-water glass two-component slurry;

[0026] The method of "from bottom to top, symmetrical grouting" is adopted to inject fast-setting cement-water glass double liquid grout, which fills the gaps and forms a water-stop barrier.

[0027] Preferably, the fast-setting cement-water glass two-component grout comprises the following components by weight:

[0028] 100 parts cement;

[0029] 20-30 parts bentonite;

[0030] 100-130 parts water;

[0031] 30-45 parts of water glass.

[0032] Preferably, in step four: during the tunnel boring machine's retraction process,

[0033] Each stage of recovery has a stroke of 5cm, a pause time of ≥1min, and a backward speed controlled at 1-2cm / min.

[0034] During the retreat process, the deviation between the center of the shield and the center line of the tunnel is ≤5mm, and the uniform deviation of the gap between the shield and the tunnel wall is ≤2mm.

[0035] Preferably, in step six: the removal of protective components and shield repositioning, the following steps are taken to remove the protective components of the shield tail brush: first, remove the outer wear-resistant protective plate, then remove the water-swellable rubber strips in the gaps of the shield tail brush, and finally remove the prefabricated steel inner support components.

[0036] Preferably, in step six: the shield machine is reset by extending the propulsion cylinders in stages during the removal of protective components and shield resetting. The resetting speed is controlled at 1-2 cm / min, the propulsion cylinders are extended in stages, each stage has an extension stroke of 5 cm, the stage pause time is ≥1 min, and the shield attitude deviation after resetting is ≤5 mm.

[0037] This invention provides a method for frontal cutterhead replacement in a confined space within a micro-shield tunnel. It offers the following advantages:

[0038] 1. This invention, through precise reverse control of the tunnel boring machine, multi-layer protection of the tail brush, and overall construction of the water-stop ring, avoids core risks such as face instability, tail brush damage, and groundwater leakage from the source, achieving safe and controllable operation throughout the cutterhead replacement process and ensuring the safety of personnel and equipment working in the enclosed space inside the tunnel.

[0039] 2. This invention focuses on the three core difficulties of frontal cutter replacement in tunnels (shield retraction, shield tail brush protection, and water-stop ring construction) and formulates a special process. Each step has clear operating parameters and quality control standards, which are suitable for the narrow space and limited ventilation working environment inside shield tunnels, and the process has strong adaptability.

[0040] 3. This invention optimizes the connection process of shield retreat, protection, and water stopping, reduces the waiting time between processes, adopts modular assembly for water stopping ring construction, and uses prefabricated protective components for shield tail brush protection, which greatly shortens the operation time in the tunnel and saves more than 20% of the construction period compared with the traditional cutterhead replacement process. Attached Figure Description

[0041] Figure 1 This is a flowchart of the method for frontal cutter replacement in a confined space micro-shield tunnel proposed in this invention;

[0042] Figure 2 This is a schematic diagram of the three-layer protection structure of the frontal cutter replacement method for micro-shield tunnels in confined spaces proposed in this invention, which consists of internal support fixing, gap filling, and external protection isolation.

[0043] Among them, 1. Precast steel internal support components; 2. Water-swellable rubber strips; 3. Wear-resistant protective plates. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] like Figures 1-2 As shown, this embodiment takes the No. 1 shield tunnel project of the Yaxing South Main and Branch Canal of the Hainan Qiongxi North Water Supply Project as the application background, and provides a detailed description of the frontal cutter replacement method in a confined space micro shield tunnel as described in this invention.

[0047] Project Overview:

[0048] The No. 1 shield tunnel of the Yaxing South Main and Branch Canal of the Hainan Qiongxi North Water Supply Project is 1.4km long with a finished tunnel diameter of 2.0m. It is constructed using a slurry balance shield tunneling machine with an excavation diameter of 2.71m. The main geological strata it traverses are weakly weathered granite (strength 110-149MPa, RQD=82-90%, Grade VII hard rock) and weakly weathered granite (standard penetration 24-56 blows, Grade II hard soil). During shield tunneling, the cutterheads may be damaged, requiring cutterhead replacement operations inside the tunnel. The working space inside the tunnel is narrow, ventilation is limited, and the cutterhead replacement operation carries high safety risks.

[0049] I. Construction Preparation

[0050] 1. Personnel preparation

[0051] The site is staffed with one on-site supervisor, two full-time safety officers, two certified tunnel boring machine operators, two certified welding / cutting operators, three protective and water-stopping construction personnel, and two auxiliary personnel. The responsibilities of each position are clearly defined, and all workers receive specialized safety and technical briefings. Workers working in the enclosed space inside the tunnel undergo physical examinations and complete training for entering the tunnel.

[0052] 2. Equipment and Material Preparation

[0053] Tunnel boring machine control equipment: 1 shield machine attitude monitoring instrument and 1 hydraulic cylinder stroke detection instrument;

[0054] Tail shield protective materials: prefabricated steel internal support components, 3mm thick wear-resistant protective plate, Φ20mm water-swellable rubber strip, fastening bolts, etc.;

[0055] Materials for waterstop ring construction: prefabricated rubber waterstop ring (matching the shield diameter), quick-setting grout (early strength type, initial setting ≤ 2h), pre-embedded grouting pipe (DN25), ring fixing bracket, expansion bolts, etc.

[0056] Auxiliary equipment: 2 x 55kW explosion-proof ventilators, 36V safety lighting equipment, 1 pump-suction four-in-one gas detector, 2 x 1T manual hoists, 2 x 4kg dry powder fire extinguishers, 1 angle grinder, 1 x KBY-50 / 70 grouting pump;

[0057] Tool changing equipment: 1 550 gas gouging welding machine (output current 60-630A), 1 carbon dioxide gas shielded welding machine (with ER50-6 Φ1.2mm welding wire and gas cylinder).

[0058] 3. On-site preparation

[0059] The work area inside the tunnel was cleared, obstacles were removed, a warning zone was demarcated, and warning signs were set up.

[0060] Install a two-way explosion-proof ventilation fan with both air intake and exhaust functions to ensure that the air velocity inside the cave is ≥0.5m / s, the oxygen concentration inside the cave is ≥19.5%, and the concentration of harmful gases meets the standard requirements.

[0061] Install 36V safety lighting, with an illuminance of ≥100 lux in the work area, and use explosion-proof cables for the lighting circuits.

[0062] Advanced reinforcement of the working face: According to geological survey data, the working face of this project is weakly weathered granite with good surrounding rock stability. Small pipe reinforcement grouting is adopted. The φ42 small pipes are 2.5m long and 0.3m circumferentially spaced. The grouting material is cement-water glass double liquid grout, and the grouting pressure is 0.4MPa.

[0063] Install settlement and convergence monitoring points at the working face with a spacing of 1.0m. Set up a real-time monitoring system to monitor the entire tool change operation in real time with a monitoring frequency of ≥1 time / 30min. Set the warning values ​​as settlement ≥5mm / h and convergence ≥3mm / h.

[0064] Check the status of equipment such as the tunnel boring machine's propulsion cylinders, articulation cylinders, and cutterhead to ensure that the equipment can operate normally.

[0065] II. Construction of Multi-Layer Protection with Shield Tail Brush

[0066] With the tunnel boring machine locked, a three-layer protection system is implemented for the tail shield brush: internal support and fixation, gap filling, and external protection isolation. Touching the tail shield brush body must be avoided throughout the process. Specific procedures are as follows:

[0067] 1. Internal bracing fixation

[0068] Precast steel internal support components are evenly arranged along the circumferential direction of the shield tail brush, with a spacing of 0.5m. The internal support components are fixed to the inner wall of the shield tail with fastening bolts to support the shield tail brush and maintain its original opening angle (30° with the shield body), preventing the shield tail brush from deforming or collapsing due to its own weight or external disturbances.

[0069] The internal support components are prefabricated using Q235 steel, and their shape matches the back contour of the shield tail brush. One end is fixed to the inner wall of the shield tail with bolts, and the other end is pressed against the middle section of the back of the shield tail brush to form a reliable rigid support.

[0070] 2. Gap filling

[0071] Within the gaps of the tail brush, Φ20mm water-swellable rubber strips are continuously laid in a ring, filling to the root of the tail brush. The rubber strips are laid continuously in a ring without joints or gaps to prevent soil and groundwater from entering the gaps and abrading the root of the tail brush.

[0072] The water-swellable rubber strip is made of polyurethane-based water-swellable material, which can expand by more than 200% when exposed to water, and can automatically seal tiny seepage channels.

[0073] 3. External protective insulation

[0074] Wear-resistant protective plates are laid on the outside of the tail shield brush. The protective plates are made of 3mm thick steel plates, spliced ​​together in a ring, with a splice gap of ≤5mm. The protective plates are fixed to the tail shield steel plates with bolts, completely covering the tail shield brush area, isolating the tail shield brush from direct contact with the tunnel wall debris and soil, and preventing the tail shield brush from being scratched and damaged during the shield tunneling process.

[0075] 4. Protection Acceptance

[0076] After the protective construction is completed, check the firmness of the internal support components, the density of the rubber strip filling, and the integrity of the protective plate coverage to ensure that the shield tail brush is not exposed, deformed, or loose. Only after the acceptance is qualified can the next process be carried out.

[0077] 3. Fill the tunnel with a water-stopping ring.

[0078] The water-stop ring is installed after the shield tail brush protection is completed. The installation location is 12m behind the shield tail (this can be adjusted within 10-15m depending on the actual geological conditions). A fast-setting grout is used to fill the annular gap between the lining ring and the tunnel wall, forming a water-stop barrier to block water from behind the shield tail. The specific operation is as follows:

[0079] 1. Segment opening inspection

[0080] Install grouting ball valves on the pre-reserved grouting holes in the tunnel segments, and open the grouting holes to check the water volume behind the tunnel wall. Based on the tunnel diameter (the diameter of the formed tunnel in this project is 2.0m), open 4 holes circumferentially and check 3 rings longitudinally.

[0081] Upon inspection, the water volume behind the wall of this project is relatively small, with no pressurized water escaping, thus meeting the conditions for the installation of a water-stop ring.

[0082] 2. Slurry Preparation

[0083] Based on the water volume behind the tunnel lining segments, a fast-setting cement-water glass dual-liquid grout was selected, and the grout setting time was controlled within 30 seconds.

[0084] The two-component slurry formulations are shown in Table 1;

[0085] Table 1 shows the mix proportions of the two-component slurry (per cubic meter):

[0086]

[0087] During preparation, cement, bentonite, and water are first mixed and stirred evenly to form liquid A. Water glass is then mixed and stirred evenly with water to form liquid B. Liquid A and liquid B are then mixed at a volume ratio of 1:0.4 using the mixer of the grouting pump. According to on-site testing, the solidification time of the mixed grout is approximately 25 seconds.

[0088] 3. Grouting and filling

[0089] Before grouting, appropriately increase the pressure in the slurry chamber to prevent excessive grout pressure from causing grout to flow into the front of the shield. The grouting pressure should be controlled at 0.25 MPa (it can be adjusted within the range of 0.2-0.3 MPa).

[0090] The grouting method is "from bottom to top, symmetrical grouting". First, the bottom grouting hole is grouted, then the two side grouting holes are grouted symmetrically in sequence, and finally the top grouting hole is grouted. Each grouting hole is grouted until grout returns from the adjacent grouting hole, ensuring that the grouting material is filled densely and without gaps.

[0091] During the grouting process, designated personnel were assigned to monitor changes in the pressure of the slurry chamber to prevent grout from flowing to the front of the shield due to excessive grouting pressure. Simultaneously, a low-strain detector was used to monitor the grouting filling effect in real time, and any voids detected were immediately filled.

[0092] 4. Waterproofing Acceptance

[0093] After the grout has initially set (≥2 hours), the inspection hole is opened to check the water-stopping effect. In this embodiment, there was no leakage or seepage through the inspection hole, indicating that the water-stopping effect was satisfactory. Simultaneously, a water level observation hole was installed behind the water-stopping ring, and continuous observation for 24 hours showed no change in water level, confirming the reliability of the water-stopping barrier.

[0094] IV. Tunnel Boring Machine Retreat

[0095] 1. Determine the backoff parameters

[0096] Based on the requirements of tool changing operations, the standard is to leave 50cm of operating space in front of the tool turret, and the total backward travel is controlled at 60cm (which can be adjusted within the range of 55-60cm).

[0097] 2. Hydraulic cylinder graded recycling

[0098] Operated by the tunnel boring machine operator, the forward propulsion cylinders at the front of the cutterhead are retrieved first, followed by the retrieval of the remaining propulsion cylinders in stages. Each stage of retrieval involves a 5cm stroke, with a pause of 1.5 minutes (≥1 minute is acceptable). The reverse speed is controlled at 1.5cm / min (adjustable within the range of 1-2cm / min) to avoid sudden stops and reversals.

[0099] The cylinder recovery sequence is as follows: first, recover the four sets of propulsion cylinders in front of the cutterhead, then recover the propulsion cylinders on both sides symmetrically, and finally recover the propulsion cylinders at the rear to ensure that the overall force of the tunnel boring machine is balanced.

[0100] 3. Adjustment of the articulated hydraulic cylinder

[0101] During the retreat process, the shield attitude is adjusted in real time by the articulated hydraulic cylinder to control the deviation between the shield center and the tunnel centerline to be ≤3mm (the design allowable value is 5mm), and the uniform deviation between the shield and the tunnel wall to be ≤1mm (the design allowable value is 2mm), so as to prevent the shield from scraping against the tunnel wall.

[0102] An attitude check is performed every 10cm of retreat, and the stroke of the articulated hydraulic cylinder is finely adjusted based on the check data to ensure that the shield's attitude is always under control.

[0103] 4. Real-time monitoring

[0104] Designate specific personnel to monitor the stroke of the propulsion cylinders and articulation cylinders, as well as the shield's attitude and tunnel wall clearance, and keep detailed monitoring records. If any attitude deviation or uneven clearance is detected, immediately adjust the cylinder parameters and pause the retraction until the parameters meet the standards.

[0105] 5. Confirm completion of back navigation

[0106] After the tunnel boring machine (TBM) retreats to its designed stroke of 60cm, the propulsion cylinder and articulation cylinder are locked. The operating space in front of the cutterhead is checked again to confirm that the space dimensions meet the requirements for cutterhead changing (the actual operating space is approximately 52cm). At the same time, the condition of the tunnel face is checked, and there are no abnormalities such as settlement or collapse.

[0107] A backlash prevention and locking device is welded to the tail of the shield to connect the tail to the rear segments and prevent the shield from sliding back and forth during subsequent construction. In this embodiment, the backlash prevention and locking device uses four sets of 20# I-beams, evenly arranged in the circumferential direction. One end is welded to the tail steel plate, and the other end is connected to the grouting hole of the segment through bolts.

[0108] V. Tool Changing Operation

[0109] After the water-stop ring is installed and accepted, the cutter box is inspected, replaced, and welded. In this embodiment, it was confirmed that cutter box #3 was severely damaged and needed to be replaced entirely.

[0110] 1. Work environment protection

[0111] Throughout the cutterhead replacement operation, good ventilation was maintained, with the ventilation fan running continuously and the air velocity inside the tunnel kept above 0.5 m / s. Sufficient lighting was provided, with the illuminance in the work area not less than 100 lux. A gas detector monitored the operation in real time, recording data every 15 minutes to ensure the oxygen concentration remained between 19.5% and 23.5%, preventing the accumulation of harmful gases.

[0112] Assign dedicated personnel to monitor the working face, observe the monitoring data every 30 minutes, and report any abnormalities immediately.

[0113] 2. Removal of damaged tools

[0114] Damaged tools were removed using a 550 air gouging machine. The air gouging current was controlled at 400-500A, and the carbon rod was Φ8mm. During the air gouging operation, an assistant was present with fire extinguishers to monitor the process, and fire blankets were laid in the work area.

[0115] After cutting, use an angle grinder to clean the tool box mounting base, removing any residual welding slag and rust, and ensuring the base is flat and clean.

[0116] 3. Welding of new cutting tools

[0117] New tool positioning: Tool positioning is carried out according to the design drawings, and a laser line projector is used to assist in positioning to ensure installation accuracy.

[0118] Welding process: Carbon dioxide gas shielded welding is used, with a welding current of 220A (adjustable within the range of 200-250A) and a voltage of 28V (adjustable within the range of 26-32V). ER50-6 Φ1.2mm welding wire is used. Multi-layer, multi-pass welding is employed, with each weld thickness not exceeding 3mm, and the interpass temperature controlled at 150-250℃.

[0119] Weld inspection: After the weld appearance inspection is qualified, 100% magnetic particle testing is carried out. The test results meet the requirements of Class II weld in the "Code for Welding of Steel Structures" (GB50661), and there are no defects such as cracks, porosity, or slag inclusions.

[0120] 4. Installation accuracy acceptance

[0121] After the cutting tools are installed, check the installation positioning deviation:

[0122] Centerline deviation: 1.5mm (≤2mm, acceptable);

[0123] Levelness: 0.3mm / m (≤0.5mm / m, acceptable);

[0124] Verticality: 0.5mm / m (≤1mm / m, qualified).

[0125] VI. Removal of Protective Components and Repositioning of the Tunnel Boring Machine

[0126] 1. Removal of the protective components of the shield tail brush

[0127] After the cutter replacement operation is completed and passes inspection, the tail brush protective components are removed. The removal principle is "outside first, inside second, and handle with care" to avoid damaging the tail brush during the removal process.

[0128] The specific operation sequence is as follows:

[0129] First, remove the outer wear-resistant protective plate: loosen the fixing bolts and remove the protective plate piece by piece, being careful to handle it gently and avoid collision with the tail brush;

[0130] Next, remove the water-swellable rubber strips from the gaps in the tail brush: carefully hook out the rubber strips with a special hook, and do not forcibly pry them out;

[0131] Finally, remove the internal support components: loosen the fastening bolts and remove the internal support components.

[0132] The dismantled protective components should be promptly removed from the work area, categorized and stored, and can be reused after being inspected and found to be intact.

[0133] After dismantling, a comprehensive inspection of the tail brush was conducted. In this embodiment, the tail brush was intact, without wear, deformation, or detachment, and required no repair or replacement.

[0134] 2. Tunnel Boring Machine Reset

[0135] Before resetting the tunnel boring machine, check the status of the cutterhead, cutter box, tail brush and other equipment again to confirm that there are no abnormalities.

[0136] Operated by the tunnel boring machine (TBM) operator, the propulsion cylinders extend in stages, with each stage extending 5cm and pausing for 1.5 minutes (≥1min is acceptable). The resetting speed is controlled at 1.5cm / min (adjustable within the range of 1-2cm / min). Simultaneously, the TBM's attitude is adjusted via the articulated cylinders to ensure it repositions to its original tunneling axis.

[0137] During the repositioning process, the shield's attitude was checked every 10cm and adjusted in real time. After the final repositioning, the shield's attitude deviation was 4mm (≤5mm, acceptable).

[0138] After resetting, lock the propulsion cylinder and check the fit between the shield and the tunnel wall and water-stop ring. There should be no scraping or deformation.

[0139] 3. Remove the anti-reverse locking device.

[0140] After confirming the stability of the tunnel boring machine, remove the anti-backward locking device welded to the tail of the shield, clean the welding slag, and restore the tail of the shield to its original state.

[0141] VII. Working Face Monitoring and Tunneling Preparation

[0142] After the tunnel boring machine is reset, the face of the tunnel continues to be monitored. The monitoring frequency is adjusted to ≥1 time / 1 hour, and continuous monitoring is carried out for 24 hours. No abnormal data is found (cumulative settlement ≤3mm, cumulative convergence ≤2mm).

[0143] Clean the work area inside the tunnel, ensuring the site is clean and tidy upon completion. Inspect the status of all equipment on the tunnel boring machine, and test the cutterhead, propulsion system, and sealing system to ensure normal operation.

[0144] Temporary equipment such as ventilation, lighting, and monitoring systems were dismantled to restore the conditions for shield tunneling operations inside the tunnel. In this embodiment, the total time from the start of cutterhead replacement to the resumption of tunneling was 8 days, saving 7-12 days compared to the traditional cutterhead replacement process (15-20 days), and improving construction efficiency by more than 30%.

[0145] Summary of implementation results:

[0146] This embodiment successfully completed the cutterhead repair and replacement operation using the method of this invention, without any face instability, leakage, or safety accidents throughout the process. Calculations show that this embodiment saved approximately 850,000 yuan in total costs (including 147,000 yuan in labor costs, 180,000 yuan in excavation costs, 250,000 yuan in shield tail brush replacement costs, 200,000 yuan in management costs, and 73,000 yuan in material reuse costs).

[0147] Example 2

[0148] This embodiment uses the Hangzhou Damaowu-Renhe Avenue water supply pipeline project as an application background to illustrate the promotion and application of the construction method of this invention.

[0149] Project Overview:

[0150] The Hangzhou Damaowu-Renhe Avenue water supply pipeline project is an important component of the Qiandao Lake water supply and distribution project. It has a total length of 28.6 km, with a shield tunnel section of 20.2 km. The shield tunnel has an excavation diameter of 6.2 m and includes 8 wells and 7 sections, with an average section length of approximately 3.0 km. This project is a fully enclosed "underground water artery" with a water diversion capacity of 1.65 million tons per day, and is a key livelihood security project at both the provincial and municipal levels.

[0151] Construction conditions:

[0152] The tunnel sections of this project mainly traverse strata consisting of silty clay, silty soil, silt, and gravel layers, with some sections passing through completely weathered rock layers. The groundwater is abundant and highly permeable, resulting in poor tunnel face stability and extremely high risks associated with cutterhead replacement operations. Furthermore, while the tunnel diameter of 6.2m is larger than that of Example 1, it is still considered small compared to conventional subway tunnel boring machines (6.0-6.5m), limiting the available working space.

[0153] Construction process:

[0154] The method of this invention was applied in cutterhead replacement operations in multiple shield tunnel sections of this project. During specific implementation, some parameters were adapted to the geological characteristics of this project.

[0155] Face reinforcement: For water-rich soft soil strata, φ42 small guide pipes are used for pre-grouting reinforcement. The guide pipes are 3.0m long, with a circumferential spacing of 0.25m and a grouting pressure of 0.5MPa. The solidification time of the two-component grout is controlled within 20 seconds to ensure the stability of the face.

[0156] Tail shield protection: basically the same as in Example 1, except that the thickness of the protective plate is adjusted to 5mm to accommodate larger diameter shields.

[0157] Water-stop ring construction: Due to the large amount of groundwater, the water-stop ring construction position was adjusted to 10m behind the shield tail, the number of longitudinal inspection rings was increased to 5 rings, and the grouting pressure was increased to 0.3MPa.

[0158] Tunnel Boring Machine Retreat: The retreat stroke is determined to be 55cm, leaving a 45cm operating space in front of the cutterhead (due to geological conditions, a 50cm space is difficult to achieve, and 45cm is assessed to meet the operational requirements).

[0159] Tool changing operation: The welding process is the same as in Example 1, and the installation accuracy requirements remain unchanged.

[0160] Implementation results:

[0161] By adopting the construction method of this invention, the project smoothly and orderly completed multiple tool change and inspection operations while ensuring safety, quality, and schedule. Compared with traditional methods, each tool change operation saved an average of 10 days of construction time, resulting in cumulative cost savings of over 2 million yuan. No safety accidents or engineering quality problems occurred, effectively ensuring the smooth implementation of this key project for people's livelihood.

[0162] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for frontal cutter replacement in a confined space micro-shield tunnel, characterized in that, Includes the following steps: Step 1: Construction preparation; clean the working area inside the tunnel, configure and check the required personnel, equipment and materials, install ventilation, lighting and safety monitoring systems, and carry out advance reinforcement of the working face and layout of monitoring points; Step 2: Multi-layer protection construction of the shield tail brush; implement three layers of protection for the shield tail brush: internal support and fixation, gap filling, and external protection and isolation. Step 3: Fill the tunnel with water-stop rings; fill the gap between the shield and the tunnel wall 10-15m behind the shield tail with water-stop rings to form a water-stop barrier; Step 4: Tunnel Boring Machine Reverses; By using the staged recovery of the propulsion cylinders and the attitude adjustment of the articulated cylinders, the tunnel boring machine reverses by a predetermined stroke, creating a cutterhead changing work space in front of the cutterhead; Step 5: Tool changing operation; In the tool changing operation space, check the toolbox, replace the tool, and perform welding operations; Step Six: Removal of Protective Components and Reset of the Tunnel Boring Machine; After the cutterhead replacement is accepted, the protective components of the tail brush are removed, and the tunnel boring machine is reset by extending the propulsion cylinders in stages.

2. The method for frontal cutter replacement in a confined space micro-shield tunnel according to claim 1, characterized in that, Step two, the multi-layer protection construction of the shield tail, specifically involves: Internal support fixing: Precast steel internal support components are evenly arranged along the annular direction of the shield tail brush, and the internal support components are fixed to the inner wall of the shield tail with fastening bolts to support the shield tail brush to maintain its original opening angle; Gap filling: Water-swellable rubber strips are continuously laid in a ring within the gap of the tail brush, with the filling depth reaching the root of the tail brush. External protective isolation: A wear-resistant protective plate is laid along the ring outside the tail shield brush, and the wear-resistant protective plate is fixed to the tail shield steel plate, completely covering the tail shield brush area and isolating the tunnel wall debris and other materials from contact with the tail shield brush.

3. The method for frontal cutter replacement in a confined space micro-shield tunnel according to claim 1, characterized in that, Step three, filling the hole with a water-stop ring, specifically involves: Install grouting ball valves on the pre-reserved grouting holes of the tunnel segments; Preparation of rapid-setting cement-water glass two-component slurry; The method of "from bottom to top, symmetrical grouting" is adopted to inject fast-setting cement-water glass double liquid grout, which fills the gaps and forms a water-stop barrier.

4. The method for frontal cutter replacement in a confined space micro-shield tunnel according to claim 3, characterized in that, The quick-setting cement-water glass two-component grout comprises the following components by weight: 100 parts cement; 20-30 parts bentonite; 100-130 parts water; 30-45 parts of water glass.

5. The method for frontal cutter replacement in a confined space micro-shield tunnel according to claim 1, characterized in that, In step four: during the tunnel boring machine's retraction process, Each stage of recovery has a stroke of 5cm, a pause time of ≥1min, and a backward speed controlled at 1-2cm / min. During the retreat process, the deviation between the center of the shield and the center line of the tunnel is ≤5mm, and the uniform deviation of the gap between the shield and the tunnel wall is ≤2mm.

6. The method for frontal cutter replacement in a confined space micro-shield tunnel according to claim 2, characterized in that, In step six, the protective components are removed and the shield is reset. The following steps are taken to remove the protective components of the shield tail brush: first, remove the outer wear-resistant protective plate, then remove the water-swellable rubber strip in the gap of the shield tail brush, and finally remove the prefabricated steel inner support components.

7. The method for frontal cutterhead replacement in a confined space micro-shield tunnel according to claim 2, characterized in that, In step six, during the removal of protective components and the repositioning of the shield machine, the shield machine is repositioned by extending the propulsion cylinders in stages. The repositioning speed is controlled at 1-2 cm / min, the propulsion cylinders are extended in stages, each stage has a stroke of 5 cm, the stage pause time is ≥1 min, and the shield machine attitude deviation after repositioning is ≤5 mm.

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