River bottom super deep high water pressure shield maintenance and repulsion construction method

Abstract

The application provides a kind of river bottom super deep high water pressure shield maintenance and re-pushing construction method, and relates to the technical field of shield construction.When shield machine is forced to stop during tunneling in river due to equipment failure, especially when serious failure such as disassembling cutter head or taking out bearings for maintenance occurs, sink well is sunk to design elevation, the soil between sink well and cutter head and the soil around shield is frozen and reinforced from sink well to shield direction, the portal is broken and the frozen soil in front of cutter head is removed by using underground excavation method, and annular lining is constructed, and shield machine is pushed into sink well from annular lining for maintenance and then launched for the second time;The application can provide safe working space for shield equipment maintenance in water bottom environment with water depth of more than 20 meters, so that it can re-tunnel, and the tunnel can continue construction.

Description

Technical Field

[0001] This invention relates to the field of shield tunneling technology, specifically a method for the repair and re-pushing of ultra-deep, high-water-pressure shield tunnels under rivers. Background Technology

[0002] Shield tunneling offers advantages such as high industrialization, minimal environmental disturbance, and no impact on ground activities. With the development of shield tunneling technology and machinery, these advantages are becoming increasingly apparent, leading to a growing number of tunnels being constructed using this method. However, the trend in my country's shield tunneling construction is shifting from simple soft soil strata to complex strata, from large-diameter to ultra-large-diameter tunnels, from medium water pressure to high and ultra-high water pressure, and from short-distance excavation to long and ultra-long-distance excavation, all of which increase the difficulty of construction.

[0003] Since tunnel boring machines (TBMs) are mainly composed of mechanical equipment such as the shield shell, cutterhead system, drive system, hydraulic system, segment assembler, piping system, and supporting trolleys, malfunctions are unavoidable during operation. Faults in the assembler and piping can be repaired directly from within. Severely worn cutterheads can be repaired using pressurized or atmospheric pressure cutterhead replacement, technologies that are currently relatively mature. However, serious failures in the main drive or main bearings require disassembling the main drive, which weighs hundreds of tons, making repairs generally impossible inside the tunnel. The main drive and main bearings are core components for the cutterhead rotation; damage to them prevents the cutterhead from rotating, forcing the TBM to shut down. This is especially problematic for underwater shield tunnels crossing rivers and seas, potentially leading to project failure.

[0004] Currently, there are several global engineering cases where tunnel boring machines (TBMs) are trapped underground due to equipment failures, unable to be excavated or repaired. These include being trapped underwater, especially in deep water exceeding 20 meters in depth, where there is still no satisfactory solution. When a TBM is trapped in deep water, and the main bearing, main drive, or other malfunctions force it to stop, the cutterhead cannot rotate, preventing it from cutting through the soil and thus hindering its forward progress. Generally, the TBM must be disassembled for repair. Firstly, there is no space in the ground; the main drive weighs over 500 tons, and there is insufficient internal space to provide sufficient lifting capacity and replacement parts to support the water and soil pressure. Current technology allows for repairs via a working shaft. However, in deep riverbeds, ensuring the working shaft can withstand significant water and soil loads, maintain stability, and provide good waterproofing is a challenge. Secondly, the working shaft is not easily positioned above the tunnel lining segments behind the tail section and the TBM itself. If it is located in front of the cutterhead, pushing the TBM into the working shaft is also a problem. Finally, all aspects need to ensure that the structure can withstand water and soil loads and has sufficient water-stopping effect to prevent water and sand inrush.

[0005] Therefore, there is a need to provide a feasible repair and restart solution for shield tunnels that cannot continue tunneling due to main drive failure, main bearing failure, or other factors in deep water conditions such as riverbeds or seabeds, to fill the gap in existing technology. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems and shortcomings of the existing technology by designing a method for the maintenance and re-pushing of ultra-deep, high-water-pressure shield tunneling machines at the bottom of rivers. When the shield tunneling machine is forced to stop due to equipment failure during the tunneling process, especially when serious failures such as the need to disassemble the cutterhead or remove the bearings for maintenance are required, a safe working space can be provided for the maintenance of the shield equipment in an underwater environment with a water depth of more than 20 meters, so that the tunnel can continue to be constructed and can be re-excavated.

[0007] A method for repairing and re-pushing ultra-deep, high-water-pressure shield tunneling machines under a riverbed includes the following steps:

[0008] Step 1: Prefabricate caissons in sections;

[0009] Step 2: Construct a temporary construction platform on the water surface, transport the first section of the caisson to the shield machine stop location, sink the first section of the caisson in front of the shield cutterhead, and place it on the bed;

[0010] Step 3: Segment the height and lower the caisson to the design elevation, complete the bottom sealing, and construct the shield machine guide rails;

[0011] Step 4: Drilling and active freezing of the freezing pipes are carried out inside the pre-embedded orifice pipes along the outer ring of the shield shell and within the portal area on the well wall at the receiving point to form a stable frozen wall;

[0012] Step 5: Cut off the receiving well wall, chisel away the frozen soil towards the cutterhead and simultaneously construct the circumferential lining. During the chiseling process, the remaining frozen soil in front of the cutterhead within the tunnel portal area must be kept frozen. After the remaining frozen soil length does not exceed 2 meters, remove the freezing pipe within the tunnel portal area and install a slide rail inside the circumferential lining.

[0013] Step 6: The tunnel boring machine is pushed into the circumferential lining, and the tunnel segments are assembled and grouting is carried out synchronously to fill the gap between the tunnel segments and the circumferential lining until the tunnel boring machine is completely inside the caisson. Water-stopping measures are taken at the receiving portal, freezing construction is stopped, freezing equipment is removed, and steel plates are welded at the pipe cutting point at the orifice to seal it.

[0014] Step 7: Disassemble and repair the tunnel boring machine inside the caisson;

[0015] Step 8: Cut away the internal steel shell of the secondary starting tunnel portal layer by layer from bottom to top, backfill the caisson simultaneously, backfill the area about 2 meters away from the tunnel portal with mortar, and backfill the remaining area with soil;

[0016] Step 9: The repaired tunnel boring machine continues to excavate forward along the route from the backfilled caisson, and leaves the caisson after cutting mortar and reinforcing the concrete caisson wall with glass fiber reinforcement.

[0017] Step 10: Remove the caisson structure above the waterline.

[0018] Preferably, the caisson has a circular plan shape, and its internal net dimensions are determined using the following formula to meet the space requirements for shield tunneling reception, secondary launching and maintenance, and freezing construction:

[0019]

[0020] In the formula: D i r is the diameter of the inner wall of the caisson; T 'a' represents the maximum radius of the tunnel boring machine; 'a' represents the radial clearance, not less than 2 meters; 'l' represents the maximum radius of the tunnel boring machine. T b is the length of the tunnel boring machine; b is the longitudinal clearance width, not less than 3 meters.

[0021] A further preferred method is to construct the caisson in sections, with the height of the first section not less than the water depth. The total height of the caisson is calculated using the following formula to ensure that river water does not enter the caisson from the top and to provide sufficient construction space at the bottom:

[0022] H = H W +H S +2r T +H O +H B

[0023] Where H is the total height of all sections of the caisson; H S H represents the thickness of the soil cover at the top of the tunnel boring machine. O The required construction space height from the bottom of the shield tunnel to the top of the caisson bottom slab shall not be less than 1 meter; H B H represents the thickness of the base plate. W Height from the riverbed to the top of the caisson:

[0024] H W =H W1 +H W2

[0025] Among them, H W1 The height from the riverbed to a flood level that occurs once every twenty years; H W2 To account for wave climb and safety height adjustment, the height should be no less than 2 meters.

[0026] Furthermore, in step 2, the caisson wall adopts a combined steel and concrete structure, with the main body being a concrete structure and a steel shell installed in the inner wall. The steel shell is connected to the main body by cylindrical head weld studs. The steel shell in the inner wall improves waterproof performance, increases the load-bearing capacity of the caisson wall, and enhances safety. At the same time, no steel shell is installed on the outer wall to reduce the amount of work required for subsequent tunnel opening removal.

[0027] Preferably, in step 4, the longitudinal reinforcement length of the frozen wall outside the tunnel segment and shield shell is calculated according to the following formula to meet the soil excavation needs within the tunnel range between the cutterhead and the caisson wall. Under the special working condition of excavating frozen soil, the frozen wall needs to withstand external water and soil loads to support and form a passage for the underground excavation, ensuring the special scenario of sealing and water-stopping the tunnel, shield machine, and caisson.

[0028] l = l1 + l T +l2

[0029] Where l is the longitudinal reinforcement length of the frozen wall outside the tunnel segment and shield shell; l1 is the distance from the longitudinal shaft wall to the cutterhead along the tunnel, and since the shaft wall is circular, the distance varies at different station numbers; l2 is the length of the frozen wall wrapping the shield tail segment, which is not less than 5 meters.

[0030] Preferably, in step 4, the frozen wall needs to wrap around the tunnel segments behind the shield tail to ensure that even if the tunnel boring machine disturbs the frozen wall, the tunnel segments and the frozen wall remain bonded together and no water or sand inrush will occur.

[0031] Preferably, step 5 involves removing frozen soil from the cutterhead in longitudinal sections, with each section not exceeding 2 meters in length to control the load-bearing capacity of the frozen wall and reduce excavation risks. A circumferential lining is then promptly installed inside to assist the frozen wall in bearing external loads, isolate the frozen wall from disturbance during tunnel construction, prevent the frozen wall from bonding with the shield machine's outer shell during air-pushing, and provide installation space for the sliding rails of the subsequent air-pushing shield.

[0032] Furthermore, in step 8, the layer height should not exceed 2 meters to ensure safety when dismantling the secondary starting portal, while layered backfilling can better control the backfill quality.

[0033] Preferably, in step 2, the net distance between the caisson and the cutterhead is not less than 2 meters. Before sinking, the soil between the caisson and the cutterhead is reinforced to avoid disturbing the tunnel boring machine and the tunnel during the caisson sinking construction.

[0034] Furthermore, in step 5, the circumferential lining is 1.5-2.5 cm thick when steel is used and 35-45 cm thick when concrete is used, to bear the load generated by the weight of the tunnel boring machine and its own weight.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] A method for repairing and restarting ultra-deep, high-pressure shield tunneling machines under rivers is designed. When a shield tunneling machine is forced to stop due to equipment failure during excavation, especially when serious failures such as disassembling the cutterhead or removing the bearings are required for repair, a safe working space can be provided for the shield equipment repair in an underwater environment with a water depth of more than 20 meters, allowing it to restart excavation and enabling the tunnel construction to continue. Attached Figure Description

[0037] Figure 1 This is a flowchart of the construction process of this invention;

[0038] Figure 2 This is a schematic diagram of the freezing tube arrangement of the present invention;

[0039] Figure 3 This is a schematic diagram of the pre-embedded orifice pipe of the present invention;

[0040] Figure 4 This is a plan view of the caisson after it has been lowered into place according to the present invention;

[0041] Figure 5 This is a longitudinal cross-sectional view of the caisson after it has been lowered into place according to the present invention;

[0042] Figure 6 This is a plan view of the water-stop steel ring installed at the construction receiving tunnel entrance of the present invention;

[0043] Figure 7 This is a longitudinal section diagram of the water-stop steel ring installed at the construction receiving tunnel entrance of the present invention. Detailed Implementation

[0044] The following description, in conjunction with the accompanying drawings and specific implementation methods, provides a more detailed explanation of the present invention: a method for repairing and re-pushing ultra-deep, high-water-pressure shield tunnels under rivers.

[0045] This patent is based on the conventional caisson design and is specifically designed for the special working conditions of tunnel boring machines (TBMs) undergoing maintenance and re-pushing under ultra-deep, high-water-pressure conditions at the bottom of rivers. In addition, the caisson design of this invention needs to take into account the disturbance to the TBM caused by the sinking construction.

[0046] The caissons in this patent differ somewhat from conventional working shafts used in shield tunneling. Firstly, conventional working shafts are typically diaphragm walls constructed on land. This invention, however, is designed for underwater environments, replacing diaphragm walls with caissons. In water, caissons offer better structural quality and load-bearing capacity than diaphragm walls. Diaphragm walls are constructed in sections, each a flat plate, making waterproofing at joints difficult and involving moment transfer. Prefabricated circular caissons offer superior waterproofing and load-bearing capacity. Caissons, prefabricated in a factory, possess sufficient roundness to convert external soil and water loads into axial forces, reducing bending moments. Furthermore, the horizontal joints are constructed on the water surface, resulting in higher connection quality, better waterproofing, and superior force transfer.

[0047] Secondly, conventional working shafts are located during the design phase based on geological conditions and surface environment. These working shafts are generally shallower and can be constructed in advance, ready for the tunnel boring machine (TBM) to advance. In this invention, the TBM is stopped first, and then the caisson is constructed at a selected location in front of the cutterhead. The construction of the caisson must consider the disturbance to the TBM, determine the distance between the caisson and the cutterhead, and address the soil excavation issues within the tunnel area between the cutterhead and the caisson.

[0048] Third, conventional working shafts are all located on land, where groundwater control is relatively easy. The tunnel portal is typically reinforced with mixing piles, jet grouting piles, and freezing, and can also be supplemented with water-stop curtains and dewatering wells. Even if a water-stopping failure occurs and a water inrush happens, a new water-stop curtain can be installed on the surface to remedy the situation. However, this patent is designed for underwater tunnels, such as deep riverbed tunnels, where surface water and groundwater are abundant. Constructing mixing piles and jet grouting piles from the water surface involves significant depth and compromises quality. Water-stop curtains and dewatering wells are ineffective, and these operations are difficult to perform from the water surface. If a water inrush occurs, it is more difficult to handle. Therefore, a caisson with better water-stopping performance is used.

[0049] Fourth, conventional freezing construction can usually be carried out from the ground, without needing to drill holes in the working shaft wall to install freezing pipes. The soil in front of the tunnel portal can be frozen and reinforced before the tunnel boring machine (TBM) arrives, making construction relatively convenient. However, here, since the TBM is already stationary, although freezing construction can be carried out from the water surface above and on both sides of the tunnel if the space constraints of water surface construction are not a concern, it is impossible to drill freezing pipes directly below the tunnel from the water surface. Therefore, the only option is to drill freezing pipes from inside the working shaft. This raises questions about how to arrange the freezing pipes and how to install them on the approximately 2-meter-thick shaft wall. Since the reinforcement effect from inside the TBM into the strata and from the water surface into deeper strata is difficult to guarantee, and the soil in the lower part of the tunnel cannot be reinforced from the water surface, the reliance on freezing is much higher, making freezing construction extremely critical. The freezing range and intensity must ensure the safety of the working shaft opening, the safety of soil excavation between the cutterhead and the working shaft, and the effectiveness of water sealing at the shield tail, shield shell, and tunnel portal.

[0050] Specifically, this invention provides a method for the repair and re-pushing of ultra-deep, high-water-pressure shield tunneling machines on the riverbed. This method can be used in both shallow and deep water, but it has greater advantages in deep water exceeding 20 meters in depth, such as... Figure 1 As shown, it includes the following steps:

[0051] Step 1: Complete the prefabrication of the caisson in the factory.

[0052] Preferably, the caisson has a circular plan shape. The net internal dimensions of the caisson must meet the space requirements for shield tunneling reception, secondary launching, maintenance, and frost-free construction. The net internal dimensions of the caisson are determined by the following formula:

[0053]

[0054] In the formula: D i The diameter of the inner wall of the caisson;

[0055] r T This represents the maximum radius of the tunnel boring machine.

[0056] 'a' represents the radial clearance, which shall not be less than 2 meters.

[0057] l T The length of the tunnel boring machine;

[0058] b represents the longitudinal clearance width, which shall not be less than 3 meters.

[0059] Furthermore, the caisson walls utilize a steel-concrete composite structure, with a steel shell installed in the inner wall. The steel shell is connected to the concrete structure using cylindrical head welded studs. Fiberglass reinforced concrete is used to reinforce the secondary launch portal area. This fiberglass reinforced concrete reinforcement facilitates direct cutting by the tunnel boring machine cutterhead, unlike reinforced concrete which requires breaking through the portal before advancement.

[0060] Preferably, a steel shell is installed on the inner wall of the caisson for two reasons. First, it improves waterproofing performance because the caisson is constructed section by section, and horizontal construction joints exist during concrete pouring. These joints are weak in load-bearing capacity and prone to water seepage. The internal steel plates are connected by welding during the construction process. Second, the portal area of ​​the secondary launch site uses glass fiber reinforced concrete, which has slightly weaker flexural strength than reinforced concrete. The internal steel shell increases the load-bearing capacity of the caisson wall, making it safer. A steel shell is not needed on the outer wall of the caisson. First, the caisson wall mainly experiences axial forces, with relatively small bending moments. The largest bending moment occurs at the portal, where the internal tension is also present. Second, removing two layers of steel plates at the portal would be a significant undertaking, and since the launch site is planned to be backfilled before the tunnel boring machine directly cuts the portal, the cutterhead cannot cut through the steel plates.

[0061] Preferably, a pre-drilled orifice pipe for freezing construction is left on the well wall to facilitate the subsequent installation of freezing pipes, such as... Figure 2 Because freezing construction beneath the tunnel can only be carried out by drilling freezing pipes from inside the working shaft, the freezing pipes along the entire circumference of the tunnel in this invention are all drilled from inside the caisson outwards. Before drilling the freezing pipes, orifice pipes need to be embedded in the caisson wall. These orifice pipes are mainly used for positioning and fixing the freezing pipes. Drilling holes in steel plates and nearly 2 meters thick concrete structures is quite difficult, so during the prefabrication of the caisson, the orifice pipes are pre-embedded in the caisson wall, such as... Figure 3 As shown.

[0062] The height of the first section of the caisson shall not be less than the water depth.

[0063] The first section of the caisson is prefabricated, while the rest can be either prefabricated or cast on-site.

[0064] The total height of the caisson is calculated using the following formula to ensure that river water will not enter the caisson from the top and to provide sufficient construction space at the bottom:

[0065] H = H W +H S +2r T +H O +H B

[0066] H W =HW1 +H W2

[0067] H is the total height of all sections of the caisson;

[0068] H W The height from the riverbed to the top of the caisson;

[0069] H S The thickness of the soil cover at the top of the tunnel boring machine;

[0070] H O The required construction space height from the bottom of the shield tunnel to the top of the roof, such as guide rail construction and freezing construction, shall not be less than 1 meter;

[0071] H B The thickness of the top plate;

[0072] H W1 This refers to the height from the riverbed to a flood level that occurs once every twenty years.

[0073] H W2 To account for wave climb and safety height adjustment, the height should be no less than 2 meters.

[0074] The thickness of the caisson wall is determined after structural calculations according to specifications.

[0075] Step 2: Construct a temporary construction platform on the water surface and transport the first section of the caisson to the shield machine's stopping point. Sink the first section of the caisson a certain distance in front of the shield cutterhead and place it on the bed.

[0076] Temporary construction platforms can be constructed using trestle bridges or floating cranes.

[0077] The clearance between the caisson and the cutterhead should be no less than 2 meters. To prevent the caisson's sinking from disturbing the tunnel boring machine (TBM), the caisson should be as far away from the cutterhead as possible. However, the farther the caisson is from the cutterhead, the longer the distance the TBM needs to travel to push into the caisson without load. A longer distance results in two problems: firstly, the length of the freezing and reinforcement process increases, making freezing more difficult; secondly, the risks of excavating soil within the frozen wall and pushing the TBM without load increase.

[0078] Before sinking, grouting reinforcement can be carried out on the ground around the tunnel boring machine (TBM) and in front of the cutterhead. This reinforcement can be performed from inside the TBM or from the water surface. However, reinforcement cannot be performed within the sinking area of ​​the caisson. The main purpose of reinforcement is to prevent disturbance to the TBM during caisson construction, which could cause displacement. Reinforcement within the sinking area is prohibited because it would prevent the caisson from sinking, or partial reinforcement might lead to skewed sinking. Grouting from inside the TBM relies on its built-in grouting system, such as radial grouting or pre-grouting, which are generally available on most TBMs. Reinforcement can also be performed from the water surface using mixing piles or jet grouting piles. Since this reinforcement requirement is not high and is mainly an auxiliary measure, mixing piles and jet grouting piles can also be used.

[0079] Step 3: Segment the height and lower the caisson to the design elevation, complete the bottom sealing, and construct the tunnel boring machine guide rails.

[0080] Plan view after sinking the caisson Figure 4 and Figure 5 As shown, the segment height of the caisson is determined based on the caisson depth, with a recommended segment height of 5-10 meters. This height primarily considers the hoisting or concrete pouring height.

[0081] For caissons other than the first section, if they are prefabricated in the factory and transported to the site for heightening, steel reinforcement joints are reserved on the prefabricated components, and concrete or grout is poured or grouted at the contact surface; if they are cast-in-place on site, formwork is erected and concrete is poured on site. The inner steel shell is welded on site, and the inner steel shell can also be used as formwork during cast-in-place construction.

[0082] Step 4: Drilling and active freezing of the freezing pipes are carried out inside the pre-embedded orifice pipes along the outer ring of the shield shell and within the portal area on the well wall at the receiving point to form a stable frozen wall.

[0083] Traditional working shaft freezing construction only requires ensuring that the tunnel entrance does not collapse and that there is no water seepage. Since the tunnel boring machine cuts through from the inside, the frozen soil bears virtually no load. However, in the working conditions described in this patent, the soil within the tunnel area between the cutterhead and the shaft wall needs to be excavated. Even if each excavation distance is required to be no more than 2 meters longitudinally, the frozen wall needs to withstand external water and soil loads in a space with a diameter exceeding the outer diameter of the shield shell and a length of 2 meters, in order to support and form a passage for the cut-and-cover construction. It is essentially a circular frozen wall, somewhat similar to a tunnel segment, but with a greater thickness, to withstand the external water and soil loads.

[0084] The longitudinal reinforcement length of the segment and outer frozen wall of the shield is calculated using the following formula:

[0085] l = l1 + l T +l2

[0086] l represents the longitudinal reinforcement length of the segment and the outer frozen wall of the shield.

[0087] l1 is the distance from the longitudinal shaft wall to the cutterhead along the tunnel. Since the shaft wall is circular, the distance varies at different station numbers.

[0088] l2 is the length of the shield tail section wrapped by the frozen wall, which is not less than 5 meters.

[0089] The frozen wall must form a reliable water-stopping barrier between the tunnel segments, shield shell, and shaft wall behind the shield tail. Particular attention must be paid to enclosing a certain range of tunnel segments behind the shield tail, because the tunnel boring machine (TBM) will advance within the frozen wall. If the shield tail segments are not enclosed and freezing only extends to the shield tail, this will be a weak point in the freezing process. Once the TBM advances, the frozen wall at the shield tail is disturbed, and water from the strata will flow from the shield tail along the gaps between the tunnel segments and the shield shell. If the soil in front of the cutterhead has been excavated, the water from the shield tail will flow into the channel in front of the cutterhead and into the caisson, causing freezing failure. However, if a certain range of tunnel segments behind the shield tail is enclosed, even if the frozen wall is disturbed during the TBM's movement, the tunnel segments and the frozen wall will remain bonded, forming a closed space between the tunnel segments, the frozen wall, and the caisson wall, preventing water and sand inrush.

[0090] The entire area inside the shield, from the tunnel entrance to the cutterhead, is reinforced. The soil in front of the cutterhead also needs to be frozen and reinforced, mainly to ensure the stability of the soil in front of the cutterhead during later excavation.

[0091] Freezing can be achieved using methods such as brine freezing, liquid nitrogen freezing, and dry ice freezing.

[0092] Step 5: Remove the receiving shaft wall, excavate the frozen soil towards the cutterhead in sections, and construct circumferential lining. Each excavation should not exceed 2 meters in length. During the excavation process, maintain the freezing between the shaft wall and the cutterhead until the remaining frozen soil length does not exceed 2 meters. Remove the freezing pipes within the tunnel portal area, excavate the remaining frozen soil, and construct the remaining lining up to the cutterhead. Install sliding rails within the lining. Excavate the frozen soil between the cutterhead and the shaft wall in sections. After the frozen soil is removed, this space will bear the external water and soil pressure from the frozen wall outside the shield. To reduce the load-bearing range of the frozen wall and improve safety, the frozen soil is excavated in sections longitudinally, and lining is constructed inside in a timely manner. This can assist the frozen wall in bearing external loads, isolate the frozen wall from disturbance during construction within the tunnel, prevent the frozen wall from bonding with the shield machine shell during air-pushing, and provide installation space for the sliding rails of the subsequent air-pushing shield. During this process, ensure that the freezing construction in front of the cutterhead continues until the remaining unexcavated frozen soil length does not exceed 2 meters. In fact, based on the above, reinforcement measures such as mixing piles and jet grouting piles can also be adopted in front of the cutterhead. However, freezing reinforcement is the most effective and has the best quality control. The height of the soil layer exposed during excavation reaches the diameter of the shield, and the strength of the frozen soil can ensure that it will not be damaged.

[0093] The inner diameter of the circumferential lining should not be less than the diameter of the shield shell, and it can be made of steel shell or reinforced concrete. The circumferential lining should be reliably connected to the portal structure. The inner diameter of the lining should not be less than the outer diameter of the shield shell, and the lining should be equipped with sliding rails to ensure that the tunnel boring machine can pass through the lining. The circumferential lining can be constructed by welding sections of steel shell or by using cast-in-place reinforced concrete. A reliable connection must be formed between the circumferential lining and the portal of the caisson to prevent structural displacement. Since the circumferential lining is not the main component bearing external soil and water loads, it only needs to withstand the weight of the tunnel boring machine and the load generated by its own weight. If a steel shell is used, the thickness is about 2 cm; if reinforced concrete is used, the thickness is about 40 cm.

[0094] Manual or small-scale machinery should be used to remove the well wall to avoid damaging the frozen outer ring of the lining.

[0095] During the process of removing frozen soil, the freezing pipes inside the tunnel portal must be secured. As mentioned earlier, when excavating frozen soil in front of the cutterhead, it is essential to ensure that the remaining frozen soil remains frozen; therefore, the freezing operation cannot be stopped.

[0096] Step 6: The tunnel boring machine (TBM) is pushed into the lining without resistance, and tunnel segments are assembled simultaneously until the TBM is completely inside the caisson. Waterproofing measures are implemented at the receiving portal, such as... Figure 6 and Figure 7 A water-stop steel ring is installed at the receiving portal. Freezing operations are halted, the freezing equipment is removed, and a steel plate is welded to the cut end of the orifice pipe to create a seal.

[0097] If the frozen wall becomes cemented to the shield shell during the air-pushing process and cannot be pushed forward, methods such as controlled heating inside the shield shell and excavation of the frozen soil adjacent to the shield shell can be used to achieve air-pushing. This mainly addresses the situation at the beginning of the air-pushing process, during active freezing and when the shield stops to assemble the segments, when the frozen wall develops and cements to the shield shell, thus fixing the shield machine in place. This problem does not exist after the shield machine enters the circumferential lining.

[0098] Water-stopping measures can be achieved using conventional water-stopping steel rings.

[0099] Step 7: Disassemble and repair the tunnel boring machine inside the caisson.

[0100] During maintenance and repair, equipment and instruments can be hoisted in and out of the wellhead.

[0101] Step 8: Cut away the inner steel shell of the secondary starting portal layer by layer from bottom to top, backfill the caisson simultaneously, backfill the area about 2 meters away from the portal with mortar, and backfill the remaining area with soil.

[0102] The layer height should not exceed 2 meters. This is to ensure safety when dismantling the secondary starting portal, and layered backfilling also allows for better control of backfill quality.

[0103] Backfill to the original or planned seabed elevation.

[0104] Backfill can be made from treated mud generated during the sinking of the caisson.

[0105] Step 9: The repaired tunnel boring machine continues to excavate forward along the route from the backfilled caisson, and leaves the caisson after cutting mortar and reinforcing the concrete caisson wall with fiberglass reinforcement.

[0106] Step 10: Remove the caisson structure above the waterline.

[0107] Demolition by explosives can be used.

[0108] This invention proposes a method for the repair and re-launch of ultra-deep, high-water-pressure shield tunneling machines (TBMs) in riverbeds. This method can solve the problem of project stagnation in deep-water areas of rivers and seas due to TBM shutdown and the inability to repair inside the tunnel. It has a wide range of applications, including water depths of 30-40 meters and highly permeable sand layers. It can be applied to most underwater tunnels in China. By setting up an underwater waterless working face and enabling hoisting and transportation through the wellhead, various equipment failures of the TBM can be repaired inside the well or transported to the project site. The internal steel shell greatly improves the waterproof and load-bearing performance of the caisson. The secondary launch after backfilling greatly reduces the risk of the initial launch. It can be widely used in shield tunnel construction where the tunneling length exceeds the TBM's tunneling life or where major parts must be replaced in the sea or river.

[0109] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed, characterized in that, Includes the following steps: Step 1: Prefabricate caissons in sections; Step 2: Construct a temporary construction platform on the water surface, transport the first section of the caisson to the shield machine stop location, sink the first section of the caisson in front of the shield cutterhead, and place it on the bed; Step 3: Segment the height and lower the caisson to the design elevation, complete the bottom sealing, and construct the shield machine guide rails; Step 4: Drilling and active freezing of the freezing pipes are carried out inside the pre-embedded orifice pipes along the outer ring of the shield shell and within the portal area on the well wall at the receiving point to form a stable frozen wall; Step 5: Cut off the receiving well wall, chisel away the frozen soil towards the cutterhead and simultaneously construct the circumferential lining. During the chiseling process, the remaining frozen soil in front of the cutterhead within the tunnel portal area must be kept frozen. After the remaining frozen soil length does not exceed 2 meters, remove the freezing pipe within the tunnel portal area and install a slide rail inside the circumferential lining. Step 6: The tunnel boring machine is pushed into the circumferential lining, and the tunnel segments are assembled at the same time. Grouting is carried out synchronously to fill the gap between the tunnel segments and the circumferential lining until the tunnel boring machine is completely inside the caisson. Water-stopping measures are taken at the receiving portal, freezing construction is stopped, freezing equipment is removed, and steel plates are welded at the pipe cutting point at the orifice to seal it. Step 7: Disassemble and repair the tunnel boring machine inside the caisson; Step 8: Cut away the internal steel shell of the secondary starting tunnel portal layer by layer from bottom to top, backfill the caisson simultaneously, backfill the area about 2 meters away from the tunnel portal with mortar, and backfill the remaining area with soil; Step 9: The repaired tunnel boring machine continues to excavate forward along the route from the backfilled caisson, cutting through the caisson wall and leaving the caisson; Step 10: Dismantle the caisson structure above the waterline; In step 2, the caisson wall adopts a combination structure of steel and concrete. The main body is a concrete structure, and a steel shell is set in the inner wall. The steel shell is connected to the main body by cylindrical head weld studs. The steel shell in the inner wall improves waterproof performance, increases the load-bearing capacity of the caisson wall, and improves safety. At the same time, no steel shell is set in the outer wall to reduce the amount of work required for subsequent tunnel portal demolition.

2. The method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed according to claim 1, characterized in that: The caisson has a circular plan shape, and its internal net dimensions are determined using the following formula to meet the space requirements for shield receiving, secondary launching and maintenance, and freezing construction: In the formula: D i r is the diameter of the inner wall of the caisson; T 'a' represents the maximum radius of the tunnel boring machine; 'a' represents the radial clearance, not less than 2 meters; 'l' represents the maximum radius of the tunnel boring machine. T b is the length of the tunnel boring machine; b is the longitudinal clearance width, not less than 3 meters.

3. The method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed according to claim 1, characterized in that, The caisson is constructed in sections, with the height of the first section not less than the water depth. The total height of the caisson is calculated using the following formula to ensure that river water does not enter the caisson from the top and to provide sufficient construction space at the bottom: H=H W +H S +2r T +H O +H B Where H is the total height of all sections of the caisson; H S H represents the thickness of the soil cover at the top of the tunnel boring machine. O The required construction space height from the bottom of the shield tunnel to the top of the caisson bottom slab shall not be less than 1 meter; H B H represents the thickness of the base plate. W Height from the riverbed to the top of the caisson: H W =H W1 +H W2 Among them, H W1 The height from the riverbed to a flood level that occurs once every twenty years; H W2 To account for wave climb and safety height adjustment, the height should be no less than 2 meters.

4. The method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed according to claim 1, characterized in that, In step 4, the longitudinal reinforcement length of the frozen wall outside the tunnel segment and shield shell is calculated according to the following formula to meet the soil excavation needs within the tunnel range between the cutterhead and the caisson wall. Under the special working condition of excavating frozen soil, the frozen wall needs to withstand the external water and soil loads to support and form a passage for the underground excavation, ensuring the special scenario of sealing and water-stopping the tunnel, shield machine, and caisson: l＝l1+l T +l2 Where l is the longitudinal reinforcement length of the frozen wall outside the tunnel segment and shield shell; l1 is the distance from the longitudinal shaft wall to the cutterhead along the tunnel, and since the shaft wall is circular, the distance varies at different station numbers; l2 is the length of the frozen wall wrapping the shield tail segment, which is not less than 5 meters.

5. The method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed according to claim 1, characterized in that, Step 4: The frozen wall needs to wrap around the tunnel segments behind the shield tail to ensure that even if the tunnel boring machine disturbs the frozen wall, the tunnel segments and the frozen wall remain bonded together and there will be no water or sand inrush.

6. The method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed according to claim 5, characterized in that, Step 5 involves removing frozen soil from the cutterhead in longitudinal sections, with each section not exceeding 2 meters in length to control the load-bearing capacity of the frozen wall and reduce excavation risks. A circumferential lining is then promptly installed inside to assist the frozen wall in bearing external loads, isolate the frozen wall from disturbance during tunnel construction, prevent the frozen wall from bonding with the shield machine's outer shell during air-pushing, and provide installation space for the sliding rails of the subsequent air-pushing shield.

7. A method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed, as described in claim 6, is characterized in that... Step 8: The layer height should not exceed 2 meters to ensure safety when dismantling the secondary starting portal. At the same time, layered backfilling can better control the backfilling quality.

8. A method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed, as described in claim 7, is characterized in that... Step 2: The net distance between the caisson and the cutterhead shall not be less than 2 meters. Before sinking, the soil between the caisson and the cutterhead shall be reinforced to avoid disturbing the tunnel boring machine and the tunnel during the caisson sinking construction.

9. A method for repairing and re-pushing ultra-deep high-water-pressure shield tunneling machines under a riverbed, as described in claim 8, is characterized in that... Step 5: When steel is used for the circumferential lining, the thickness is 1.5-2.5 cm; when concrete is used, the thickness is 35-45 cm. The lining bears the load generated by the weight of the tunnel boring machine and its own weight.

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