Construction method for super-large-diameter earth pressure balance shield to penetrate through water area in permeable stratum

Abstract

A water area crossing construction method for a permeable stratum ultra-large-diameter earth pressure balance shield comprises the following steps that targeted model selection is conducted on a shield tunneling machine, and improvement design is conducted on the structure in the tunneling process of the shield tunneling machine according to the stratum and potential construction risks; after the shield tunneling machine enters the water area environment for tunneling, stopping the machine, filling the soil bin with thick slurry, filling the soil bin of the shield tunneling machine with inert slurry such as the thick slurry, and pressing the inert slurry into the tunnel face crack; in-hole advanced grouting reinforcement is carried out for the stratum section with uneven hardness, and a WSS retreating type grouting technology is adopted; if the advanced grouting reinforcement inspection is qualified, the shield tunneling machine conducts tunneling forwards, and in the tunneling process, tunneling is conducted in an air pressure auxiliary mode; if the advanced grouting reinforcement inspection is not qualified, returning to the step 2 to fill the soil bin; and after the shield tunneling machine completes three rings of tunneling, stopping tunneling, and circulating the steps until the tunneling of the water area section is successfully completed. By means of the construction method, earth pressure balance shield construction of the large-diameter complex stratum penetrating through the water area can be achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of shield tunneling, and specifically relates to a method for constructing ultra-large diameter earth pressure balance shield tunnels through water bodies in permeable strata. Background Technology

[0002] Because large-diameter earth pressure balance (EPB) shield tunneling machines may encounter problems such as turbine blowouts when crossing rivers, slurry balance shield tunneling machines are currently the primary method used for long-distance crossings of major rivers in complex geological formations in China. However, for geological formations suitable for both slurry balance and EPB shield tunneling machines, EPB shield tunneling machines offer advantages such as smaller construction footprint, higher tunneling efficiency, and better environmental protection, demonstrating better adaptability in conditions such as tunneling through complex geological formations, limited land resources, and sensitive surrounding environments.

[0003] However, large-diameter earth pressure balance shield tunneling faces multiple technical challenges during its passage: First, in highly permeable strata and composite strata such as soft upper and hard lower layers, the tunnel face is prone to instability, collapse, or river water penetration; second, auger blowout accidents are frequent, and the traditional double gate design is prone to failure to close effectively in emergency situations due to rock jamming or electrical faults, causing safety hazards; third, surface and building settlement control is difficult during construction, making it difficult to meet millimeter-level settlement requirements; fourth, the shield machine's cutting tools wear out quickly and require frequent replacement during tunneling, and the soil chamber is prone to mud cake formation, affecting the continuity of construction. Summary of the Invention

[0004] This invention provides a construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata, in order to solve the problem of high risk in the construction of earth pressure balance shield tunneling through water in large-diameter complex strata.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: Construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata includes the following steps: Step 1: Targeted selection of tunnel boring machine (TBM) and improvement design of the structure of the TBM during the tunneling process based on the geological conditions and potential construction risks; Step 2: After the tunnel boring machine (TBM) enters the water environment for tunneling, it stops and uses thick grout to fill the soil chamber. The soil chamber of the TBM is filled with thick grout or other inert grout, and the inert grout is pumped into the cracks at the tunnel face. Step 3: For sections with uneven strata, advance grouting reinforcement is carried out inside the tunnel, using the WSS retreat grouting process; Step 4: If the pre-grouting reinforcement inspection is qualified, the tunnel boring machine will advance forward. During the tunneling process, air pressure assisted mode will be used for tunneling. If the pre-grouting reinforcement inspection is unqualified, return to Step 2 to fill the soil chamber. Step 5: After the tunnel boring machine has completed 3 rings, stop tunneling and carry out soil filling and pre-grouting reinforcement in the tunnel according to Step 2 and Step 3 respectively. After the reinforcement is completed and the effect is accepted, complete 3 rings of tunneling again. Repeat the construction cycle until the tunneling of the water section is successfully completed.

[0006] Furthermore, the improved design of the tunnel boring machine structure in step one includes: installing telescopic cameras on the soil chamber wall for real-time monitoring of the soil chamber condition, designing an active soil mixer for the soil chamber, designing a detachable cover plate at the bottom of the screw conveyor, and configuring a synchronous dual-liquid slurry system.

[0007] Furthermore, in step two, before the tunnel boring machine enters the aquatic environment, the soil chamber is filled with double high pressure at multiple points. The filling process is divided into two stages of thick grout injection. In the first stage, thick grout with large diffusion is injected slowly at low pressure. In the second stage, thick grout with small diffusion is injected until the soil chamber pressure stabilizes. The grout is injected synchronously through multiple injection holes in the soil chamber wall.

[0008] Furthermore, in step three, advance grouting reinforcement is carried out inside the tunnel. The reinforcement range is the 120° area of ​​the shield arch top and multiple grouting holes are set up. The cement and water glass dual-liquid grout and the backward segmented grouting process are adopted. One reinforcement cycle is completed every 3 rings of tunneling.

[0009] Furthermore, in step three, when carrying out pre-grouting reinforcement inside the tunnel, five grouting holes within a 120° range of the shield arch are selected for grouting reinforcement. The grouting sequence is as follows: holes #1 and #4, holes #2 and #5, and holes #3 are grouted alternately. After stopping the machine, the soil chamber is filled.

[0010] Furthermore, in step four, when tunneling in pneumatic-assisted mode, the air pressure accuracy of the soil chamber is controlled by an independent automatic air pressure compensation system, in conjunction with a multi-level grouting system, which includes pre-grouting, shield grouting, synchronous grouting, and secondary grouting.

[0011] Furthermore, the secondary grouting is carried out after the segments have exited the shield tail for a certain number of rings, including a single-component grout for filling the formation and a two-component grout for water stopping. The combination of the two grouts achieves the dual effect of filling formation voids and water stopping protection.

[0012] Furthermore, in step one, the improvement of the tunnel boring machine structure also includes: adding a mechanical emergency gate to the original two rear gates of the spiral shaft. The emergency gate is mechanically opened and closed by a hand-operated hoist, and can be quickly closed in an emergency to block the risk of spiral shaft gushing.

[0013] Furthermore, in step three, when carrying out pre-grouting reinforcement inside the tunnel, if it is necessary to pause grouting, first take out the water glass suction pipe and put it into a bucket of clean water, then take out the cement pipe, and at the same time pull out the grouting pipe by 1m, inject clean water into the hole, and then stop grouting; during grouting, rotate the cutter head intermittently.

[0014] Furthermore, when configuring the cutters for the tunnel boring machine, the diameter-maintaining cutter is equipped with a wedge-shaped toothed hob, the front cutter uses a smooth welded hob, and the center cutter is equipped with a double wedge-shaped toothed hob.

[0015] The present invention can achieve the following beneficial effects: 1. The construction method of this invention adopts in-tunnel pre-reinforcement instead of traditional vertical reinforcement on the water surface, which avoids the damage to the aquatic ecological environment caused by water surface construction, simplifies the construction process, greatly improves construction efficiency, and is suitable for the needs of long-distance tunneling construction of large-diameter shield tunnels.

[0016] 2. The construction method of this invention innovatively adds a mechanical emergency gate for the spiral machine, which, together with the original two gates, forms a triple protection, allowing for emergency closure in a short time and effectively eliminating the risk of spiral machine gushing. Combined with the dual high-pressure multi-point soil chamber filling technology and WSS backward advanced grouting process, it significantly enhances the stability of the working face and avoids collapse and river water penetration accidents.

[0017] 3. The construction method of this invention adopts a combination of pneumatic-assisted tunneling mode and a combined multi-layer grouting system. Through the synergistic effect of advanced grouting, radial grouting of the shield body, synchronous grouting and secondary grouting, it can achieve millimeter-level settlement control of the ground surface and buildings, and even achieve zero settlement effect. It is especially suitable for construction scenarios where tunnels pass under buildings.

[0018] 4. The construction method of this invention is based on the conventional configuration of the tunnel boring machine and is specifically modified to optimize the selection and configuration of the cutting tools. Special cutting tools such as smooth welded cutting tool rings are used to reduce the frequency of cutting tool replacement. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the construction method of the ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to the present invention; Figure 2 This invention relates to a tool holder and cutting tool configuration diagram; Figure 3 This is a schematic diagram of the earthwork filling process of the present invention. Figure 4 This is a schematic diagram of the arrangement of the advanced grouting holes in this invention; Figure 5 This is a cross-sectional design drawing of the advanced reinforcement inside the tunnel according to the present invention; Figure 6 This is a schematic diagram of the pneumatic-assisted tunneling principle of the present invention; Figure 7 This is a schematic diagram of the multi-layer grouting system in step four of the present invention. Detailed Implementation

[0020] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be more thorough and complete.

[0021] Large-diameter earth pressure balance shield tunneling machines (EPBs) crossing rivers may cause problems such as turbine blowouts. Due to insufficient shield tunneling technology and safety considerations, slurry balance shield tunneling machines are currently the primary method used for long-distance crossings of major rivers in complex geological conditions in China. However, slurry shield tunneling is relatively expensive, costing at least 10% more than EPB shield tunneling. This application provides a method for constructing ultra-large-diameter EPB shield tunnels across waterways in permeable strata. This method significantly reduces the cost of long-distance shield tunneling across waterways, lowers the safety risks for construction personnel, and minimizes project cost-benefit losses.

[0022] Construction method of ultra-large diameter earth pressure balance shield tunneling through water in permeable strata, refer to Figure 1 Specifically, it includes the following steps: Step 1: Targeted selection of tunnel boring machine (TBM) – Based on the geological conditions and potential construction risks, the structure of the TBM during the tunneling process is modified and designed.

[0023] Based on the characteristics of large-diameter earth pressure balance shield tunneling and the challenges of traversing water environments, the shield machine underwent targeted design during the selection and design phase. To monitor the soil improvement and tunnel face conditions, telescopic cameras were specifically installed on the soil chamber walls for real-time monitoring. To improve the soil improvement effect, an active soil mixer was designed to enhance soil fluidity and reduce the risk of mud cake formation. To improve the repair efficiency of the auger after wear during long-distance tunneling, a detachable cover plate was designed at the bottom of the auger, connected to the auger cylinder wall with bolts for quick replacement after cylinder wall wear. A synchronous dual-liquid grout system was also specifically configured to ensure timely and full filling behind the tunnel segments, preventing segment floating.

[0024] Furthermore, the original shield tunneling machine's auger rear gate design had two gates. In the event of a auger blowout, the auger could easily become jammed due to the slag and debris between the gates, or an electrical fault could prevent it from closing. To prevent the risks caused by auger blowouts, the shield tunneling machine structure was improved by adding a mechanical emergency gate to the original two rear gates. The mechanical emergency gate is made of Q235 steel plate. In an emergency, it can be mechanically opened and closed using a hand-operated hoist to prevent a blowout. The gate opens in about 60 seconds, effectively reducing the risk of auger blowouts during shield tunneling.

[0025] When configuring cutterheads for tunnel boring machines (TBMs), especially in areas where the TBM passes under major rivers, the geological formations often exhibit uneven hardness. Cutterheads in these uneven formations wear out quickly, leading to long replacement intervals and high risks. To reduce abnormal cutter damage and frequent replacements, based on geological conditions and experience in similar formations, the cutterheads are configured according to the following principles: For cutterheads with a high diameter, wedge-tooth hobbing cutters are used to enhance wear resistance; the front cutters utilize smooth-surface welded hobbing cutters to ensure rock-breaking efficiency while enhancing wear resistance; and the center cutter is equipped with double wedge-tooth hobbing cutters to further enhance wear resistance.

[0026] In this embodiment, the strata inside the tunnel are soil-like strongly weathered granite, massive strongly weathered granite, and moderately weathered granite. Therefore, the cutting tool needs to have good wear resistance. Considering the dense nature of the granite, the tool's penetration capability is also a crucial parameter. (Refer to...) Figure 2 Based on the experience gained from trial tunneling and the results of cutter trials, the cutter configuration for shield tunneling under the river is as follows: 5 diameter-maintaining cutters using toothed roller cutters; 55 large cutters in the frontal area and edge areas using smooth welded roller cutters; 22 small cutters in the frontal area using toothed roller cutters; and 4 center cutters using double toothed roller cutters.

[0027] Step Two: After the tunnel boring machine (TBM) enters the aquatic environment for excavation, it is stopped and the soil chamber is filled with thick grout. Thick grout or other inert grout is used to fill the soil chamber of the TBM, and the inert grout is then injected into the cracks at the tunnel face. Filling the soil chamber with thick grout prevents grout from flowing into the soil chamber during the grouting process.

[0028] Thick slurry is prepared at the ground mortar station to ensure sufficient slurry volume. The consistency of the thick slurry is controlled during the process. The thick slurry is continuously introduced into the slurry tank of the trolley through pump pipes and slurry trucks. The thick slurry in the trolley slurry tank is injected into the soil chamber and the radial holes of the shield body. The earth pressure sensor determines whether it is full. The injection volume is generally 130m³ to 140m³. Considering the diffusion coefficient, it should be about 140m³ to 150m³.

[0029] Reference Figure 3 For thick grout filling, a grout with a diffusion degree of 15-18cm is first used for long-distance diffusion, injected slowly at low pressure, controlled according to 1.2 times the earth pressure at the tunneling location. At this stage, the grout concentration is low and the diffusion is good, thus diffusing the grout into the soil fissures and enhancing the airtightness of the soil. After the pressure reaches the preset pressure, a thicker grout with a diffusion degree of ≤14cm is used to continue filling until the predetermined pressure is reached. It is observed that the pressure drop in the soil chamber is less than 0.1 bar within half an hour of settling; otherwise, thicker grout is injected. At this stage, the grout concentration is high and the density is good, which is used to further enhance the airtightness of the soil. During both injection processes, the injection holes on the soil chamber wall at positions 9 to 12 o'clock are used for simultaneous injection at multiple points.

[0030] Step 3: For sections with uneven strata, advance grouting reinforcement is carried out inside the tunnel, using the WSS retreat grouting process.

[0031] Riverbed strata typically consist of a soft upper layer and a hard lower layer. To ensure the safe and smooth passage of the tunnel boring machine (TBM) through this soft-lower-hard section and to avoid issues such as soil pressure loss or over-excavation during tunneling, pre-grouting reinforcement is employed to assist in the excavation. The pre-grouting reinforcement width extends to a 120-degree range around the tunnel crown, increasing the number of holes from 1-2 to 5 compared to conventional diameter TBMs. The reinforcement thickness is 4 meters. A backward-retreating segmented grouting process is used, reinforcing the soil from 7.5 meters to 1.5 meters in front of the cutterhead each time. Every three rings constitute one reinforcement cycle, and this cycle is repeated to complete the tunneling through the soft-lower-harder strata.

[0032] Five grouting holes within a 120-degree range of the shield arch crown were selected for grouting reinforcement, referring to... Figure 4 and Figure 5 The grouting fluid used is a cement-water glass grout. The grouting sequence is as follows: holes #1 and #4, holes #2 and #5, and holes #3 are grouted alternately. After the machine stops, the soil chamber is filled according to the above steps. Near the shield assembly machine, a retractable support platform is erected using steel profiles, utilizing the space near the shield auger and connecting bridge, for pre-grouting operations inside the tunnel.

[0033] During the grouting process, the grouting pressure must be strictly controlled, and the grouting volume must be closely monitored. If the pressure suddenly rises or grout overflows from the borehole wall or cross-section, grouting should be stopped immediately. After identifying the cause, measures such as adjusting the grouting parameters or withdrawing the drill rod should be taken to restart the grouting process. If grouting needs to be paused, the water glass suction pipe must first be removed and placed in a bucket of clean water, and then the cement pipe must be removed. At the same time, the grouting pipe should be pulled out 1m, and clean water should be injected into the borehole before stopping the grouting. This ensures that the pipeline remains unobstructed and that the grouting section is not affected by water injection. During grouting, the cutterhead must be rotated intermittently to prevent the grout from flowing into the working face and solidifying, which could jam the cutterhead. The pneumatic drilling rig should be used intermittently to prevent the drill rod from seizing.

[0034] After the pre-grouting reinforcement is completed, the stability of the air pressure in the soil chamber is observed in the subsequent pneumatic-assisted mode of the tunnel boring machine (TBM). This indicates that the TBM's air compressor can maintain stable pressure under the set soil chamber pressure, meeting operational requirements, thus demonstrating the effectiveness of the pre-grouting. If the predetermined effect cannot be achieved after pre-grouting, the grouting parameters will be further optimized.

[0035] Step 4: If the pre-grouting reinforcement inspection is qualified, the tunnel boring machine will advance forward. During the tunneling process, air pressure assisted mode will be used for tunneling. If the pre-grouting reinforcement inspection is unqualified, return to Step 2 to fill the soil chamber.

[0036] Specifically, pneumatic-assisted tunneling mode refers to a semi-pneumatic tunneling mode in which air is automatically injected into the upper part of the tunnel chamber during closed-loop shield tunneling to replace the excavated soil in the soil chamber through an automatic gas compensation system. This lowers the excavated soil level in the soil chamber of the earth pressure balance shield to a certain height, and balances the water and soil pressure at the tunnel face by setting a pressure. Lowering the excavated soil level in earth pressure balance shields can effectively increase the difficulty of excavated soil improvement and better protect the cutting tools. At the same time, the stable pneumatic mode provides better support for the tunnel face compared to the earth pressure mode. However, large-diameter earth pressure balance shields have a large tunnel face area and a large soil chamber volume, making it easier for gas to escape through stratum fissures. Precise control of the soil chamber pressure is more difficult than in conventional shields.

[0037] Reference Figure 6 In this embodiment, an independent automatic air pressure compensation system is used to ensure the stability of air pressure in the soil chamber under air pressure assist mode, while improving the accuracy to 0.1 bar, so that the shield air pressure assist mode can achieve better results.

[0038] Based on the tunneling situation of the large shield tunnel, multi-level grouting with different grout forms is carried out in the section where the shield tunnels pass under water. After the shield tunnel passes, radar scanning behind the tunnel wall or monitoring inside the tunnel is carried out. Supplementary grouting is carried out in areas with abnormalities to ensure that the grouting is dense and to reduce delayed settlement.

[0039] The multi-level grouting system specifically includes pre-grouting, shield grouting, synchronous grouting, and secondary grouting, such as... Figure 7 As shown, advanced grouting is used to achieve ground reinforcement grouting, shield grouting is used to fill the gap between the shield and the surrounding soil layer, synchronous grouting is used to fill the gap between the tunnel excavation and the lining structure, and secondary grouting is used to reinforce the lining structure and the tunnel soil layer.

[0040] The specific steps for advance grouting are as described in step three. If the excavation diameter of the shield cutterhead is larger than the shield body diameter, there will be building gaps around the shield body. When the settlement requirements are high, such as when the shield passes under a risk source, shield body grouting is required. Shield body grouting uses inert grout injected into the radial holes of the shield body of the shield machine to fill the building gaps around the shield body and control the ground settlement when the shield body passes through.

[0041] The grouting type used in the synchronous injection is cement mortar. In this embodiment, the tunnel boring machine (TBM) has a void volume V = 18 cubic meters. In silt and completely weathered granite strata, the synchronous grouting volume is 27 m³ / ring, the synchronous grouting coefficient is 1.5, and the grouting pressure is 0.3–0.5 MPa. In moderately weathered granite strata across the entire cross-section, the synchronous grouting volume is 32.4 m³ / ring, the synchronous grouting coefficient is 1.8, and the grouting pressure is 0.3–0.5 MPa. The gelling time is generally 4–6 hours. Depending on the geological conditions and tunneling speed, the gelling time is adjusted by adding accelerators and changing the mix proportions through field tests. For highly permeable strata and sections requiring grouting to provide higher early strength, the mix proportions are further adjusted and early-strength agents are added through field tests to further shorten the gelling time.

[0042] To avoid excessive ground settlement caused by shield tunneling construction, and considering that the grouting filling effect behind the large-diameter shield wall is lower than that of conventional diameter shields, timely supplementary grouting is necessary, followed by secondary grouting. This grouting occurs 8-10 rings after the shield tail. Secondary grouting is divided into single-component and double-component grouting. Single-component grout is mainly used for ground filling, with a water-cement ratio of 1:1. Double-component grout is mainly used as a ground sealing ring, applied every 5-10 rings, and consists of cement grout and water glass. The grout mix ratio is as follows: the cement grout uses 42.5R ordinary Portland cement with a water-cement ratio of 1:1; the water glass is a 35 Baume solution diluted with water at a ratio of 1.5:1. The grouting pressure is controlled to be 1-2 bar higher than the soil and water pressure at that location, ensuring the grout has sufficient diffusion capacity without significantly impacting the surrounding soil and the grouting body.

[0043] Step 5: After the tunnel boring machine has completed 3 rings, stop tunneling and carry out soil filling and pre-grouting reinforcement in the tunnel according to Step 2 and Step 3 respectively. After the reinforcement is completed and the effect is accepted, complete 3 rings of tunneling again. Repeat the construction cycle until the tunneling of the water section is successfully completed.

[0044] This construction method is applicable to large-diameter tunnel boring machines (TBMs) with a diameter of 8 meters or more crossing large rivers and other water-related environments. It is also applicable to highly permeable strata and can effectively improve construction safety. Its technical advantages are particularly prominent in the following scenarios: First, when tunneling under long distances of water, it enables the TBM to safely and smoothly pass under the water by relying on key technologies; second, when tunneling under buildings and structures, it can effectively control the settlement of buildings and structures at the millimeter level; third, it can effectively control the risk of surface settlement in composite strata such as soft upper and hard lower layers.

[0045] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for constructing a large-diameter earth pressure balance shield tunnel through water in permeable strata, characterized in that: Includes the following steps: Step 1: Targeted selection of tunnel boring machine (TBM) and improvement design of the structure of the TBM during the tunneling process based on the geological conditions and potential construction risks; Step 2: After the tunnel boring machine (TBM) enters the water environment for tunneling, it stops and uses thick grout to fill the soil chamber. The soil chamber of the TBM is filled with thick grout or other inert grout, and the inert grout is pumped into the cracks at the tunnel face. Step 3: For sections with uneven strata, advance grouting reinforcement is carried out inside the tunnel, using the WSS retreat grouting process; Step 4: If the pre-grouting reinforcement inspection is qualified, the tunnel boring machine will advance forward. During the tunneling process, air pressure assisted mode will be used for tunneling. If the pre-grouting reinforcement inspection is unqualified, return to Step 2 to fill the soil chamber. Step 5: After the tunnel boring machine has completed 3 rings, stop tunneling and carry out soil filling and pre-grouting reinforcement in the tunnel according to Step 2 and Step 3 respectively. After the reinforcement is completed and the effect is accepted, complete 3 rings of tunneling again. Repeat the construction cycle until the tunneling of the water section is successfully completed.

2. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: The improvements made to the shield machine structure in step one include: installing telescopic cameras on the soil chamber wall for real-time monitoring of the soil chamber conditions, designing an active soil mixer for the soil chamber, designing a detachable cover plate at the bottom of the screw conveyor, and configuring a synchronous dual-liquid slurry system.

3. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: In step two, before the tunnel boring machine enters the aquatic environment, the soil chamber is filled with double high pressure at multiple points. The filling process is divided into two stages of thick grout injection. The first stage is low-pressure slow injection of thick grout with a large diffusion. The second stage is injection of thick grout with a small diffusion until the soil chamber pressure stabilizes. The grout is injected synchronously through multiple injection holes in the soil chamber wall.

4. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: In step three, advance grouting reinforcement is carried out inside the tunnel. The reinforcement area is a 120° area at the top of the shield arch, and multiple grouting holes are set up. The cement and water glass dual-liquid grout and the backward segmented grouting process are adopted. One reinforcement cycle is completed every 3 rings of tunneling.

5. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 4, characterized in that: In step three, when carrying out pre-grouting reinforcement inside the tunnel, five grouting holes within a 120° range of the shield arch are selected for grouting reinforcement. The grouting sequence is as follows: holes #1 and #4, holes #2 and #5, and holes #3 are grouted alternately. After stopping the machine, the soil chamber is filled.

6. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: In step four, when tunneling in pneumatic-assisted mode, the air pressure accuracy of the soil chamber is controlled by an independent automatic air pressure compensation system, in conjunction with a multi-level grouting system, which includes pre-grouting, shield grouting, synchronous grouting and secondary grouting.

7. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 6, characterized in that: The secondary grouting is carried out after the segments have exited the shield tail for a certain number of rings. It includes a single-component grout for filling the formation and a two-component grout for water stopping. The combination of the two grouts achieves the dual effect of filling formation voids and water stopping protection.

8. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: In step one, the improvement of the tunnel boring machine structure also includes: adding a mechanical emergency gate to the original two rear gates of the auger. The emergency gate is mechanically opened and closed by a hand-operated hoist, and can be quickly closed in an emergency to block the risk of auger jetting.

9. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: In step three, when carrying out pre-grouting reinforcement inside the tunnel, if it is necessary to pause grouting, first take out the water glass suction pipe and put it into the clean water bucket, then take out the cement pipe, and at the same time pull out the grouting pipe 1m, inject clean water into the hole and then stop grouting; during grouting, rotate the cutter head intermittently.

10. The construction method for ultra-large diameter earth pressure balance shield tunneling through water in permeable strata according to claim 1, characterized in that: When configuring the cutters for a tunnel boring machine, the diameter-maintaining cutter is equipped with a wedge-shaped toothed hob, the front cutter uses a smooth welded hob, and the center cutter is equipped with a double wedge-shaped toothed hob.

Images