Shield receiving construction method for water-rich soft stratum

Abstract

The invention relates to the technical field of shield construction, in particular to a shield receiving construction method for a water-rich soft stratum. Comprising the following steps of S1, ground vertical drilling and freezing pipe laying; s2, stratum freezing reinforcement and effect monitoring; s3, mounting and backfilling a receiving end steel sleeve; s4, performing a closed water test on the steel sleeve; s5, shield tunneling machine tunneling and receiving preparation; s6, the shield tunneling machine enters the steel sleeve and is shut down; s7, mounting an arc-shaped steel plate of the tunnel portal; and S8, dismounting the freezing system and carrying out thaw settlement treatment. Freezing pipes are arranged through vertical drilling on the ground, stratum freezing reinforcement is conducted, underground water can be effectively isolated, the stability of the end stratum is improved, the posture of the shield tunneling machine in the receiving process is accurately controlled, the shield tunneling machine is adaptive to complex construction scenes, operation safety and smooth construction of existing lines are guaranteed, and compared with a traditional manual underground excavation type receiving mode, construction is more convenient and faster, and construction efficiency is improved. And the construction requirements of water-rich soft stratums and existing line protection areas can be better met.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine (TBM) construction technology, specifically a method for receiving TBMs in water-rich, soft strata. Background Technology

[0002] With the accelerating pace of urbanization and the continuous growth of urban population, the pressure on surface transportation is becoming increasingly prominent. Underground rail transit, with its advantages of efficiency, convenience, and environmental friendliness, has become an important measure to improve urban transportation networks and alleviate traffic congestion. In the process of renovating old urban areas and upgrading transportation in large cities, the construction of new subway lines often requires construction near existing operating subway lines, inevitably involving the receiving operation after the tunnel boring machine passes under the protection zone of the existing line. The safety and stability of such construction scenarios are directly related to the normal operation of the existing lines and the safety of construction.

[0003] In urban underground engineering construction, soft strata such as water-rich silty soil and silty sand are widely distributed. These strata have high water content, low bearing capacity, and high permeability, and are prone to deformation and collapse. When a tunnel boring machine (TBM) receives the TBM in the protection zone of an existing railway line, controlling the stability of the strata at the tunnel end is quite difficult. If traditional receiving methods are used, problems such as water and sand inrush and excessive ground settlement are likely to occur, which may affect the track and box culvert structure of the existing operating line and cause operational safety hazards.

[0004] Currently, shield tunneling reception in existing railway protection areas still has many shortcomings. Traditional manual excavation methods are inefficient, costly, and lack mechanization, making them unsuitable for complex geological conditions. When conventional shield tunneling methods are applied in water-rich, soft strata, they struggle to effectively isolate groundwater, reinforce the end strata, and precisely control the shield machine's attitude, easily leading to problems such as portal leakage and structural deformation. These issues fail to adequately guarantee the operational safety of existing railway lines and the smooth progress of construction. Therefore, a shield tunneling reception technology adapted to such complex construction scenarios is urgently needed to address the numerous problems associated with existing methods. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a shield tunneling method for receiving and constructing shield tunnels in water-rich, soft strata with complex geological conditions.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for shield tunneling reception in water-rich, soft strata includes the following steps:

[0008] S1. Vertical drilling and freezing pipe installation: Vertical drilling is carried out on the ground at the shield receiving end in the existing line protection area. Freezing pipes are installed in the drilling, and the freezing pipes are connected to brine pipes and cooling water pipes. The brine pipes and cooling water pipes are connected to the freezing station on the first basement floor of the station. Temperature measuring holes and probe holes are installed around the freezing pipes.

[0009] S2. Ground freezing reinforcement and effect monitoring: Start the freezing station's refrigeration unit, transport brine to the freezing pipe, and reinforce the ground at the receiving end to form a frozen soil solidified with the underground continuous wall. Monitor the reinforcement status through temperature measurement holes and probe holes and adjust the unit parameters accordingly.

[0010] S3. Installation and backfilling of steel sleeve at the receiving end: Weld a transition ring onto the steel ring of the receiving end portal, install a steel sleeve on the outside of the transition ring, set a reaction frame at the bottom of the steel sleeve and fix it to the station structure, pour a mortar base into the steel sleeve and fill it with fluidized solidified soil.

[0011] S4. Water tightness test of steel sleeve: Conduct a water tightness test on the steel sleeve.

[0012] S5. Tunneling and Receiving Preparation of Tunnel Boring Machine: After calibrating the attitude of the tunnel boring machine, tunnel at a constant speed. When the cutterhead enters the frozen soil solidification body, add foaming agent to improve the soil and inject double liquid grout through the reserved grouting holes of the segment to form a water-tight ring.

[0013] S6. Tunnel Boring Machine Enters Steel Sleeve and Stops: Control the tunnel boring machine to enter the steel sleeve, adjust the propulsion parameters, and stop the machine after advancing to the preset position and empty the backfill material.

[0014] S7. Installation of curved steel plate at the tunnel portal: Remove the transition ring, install prefabricated curved steel plate at the tunnel portal, and bolt and weld the curved steel plate to the pipe segments and the tunnel portal steel ring.

[0015] S8. Dismantling of the freezing system and thawing settlement treatment: Stop the brine supply and remove the freezing pipes. After sealing the freezing holes, dismantle the freezing station and steel sleeve. Perform thawing settlement compensation grouting in the frozen soil thawing area and complete the shield tunneling reception.

[0016] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art:

[0017] By drilling vertical holes in the ground to lay freezing pipes and freezing and reinforcing the strata, groundwater can be effectively isolated and the stability of the strata at the end can be improved. Combined with the installation of steel sleeves, the sealing of prefabricated arc-shaped steel plates and the grouting for settlement compensation, the occurrence of problems such as water and sand inrush, ground settlement and leakage at the tunnel portal can be reduced. The attitude of the tunnel boring machine during the receiving process can be precisely controlled, adapting to complex construction scenarios, ensuring the safe operation of existing lines and the smooth progress of construction. Compared with the traditional manual tunneling receiving method, the construction is more convenient and can better adapt to the construction needs of water-rich soft strata and existing line protection areas.

[0018] As a preferred embodiment, a further technical solution of the present invention is:

[0019] Preferably, in S1, vertical drilling is performed using a drilling rig to open the hole, and after penetrating the structural layer, the freezing pipe is hoisted and drilled a second time to the designed depth. This ensures the accuracy and stability of the freezing pipe layout, guarantees that the freezing pipe can reach the depth required by the design, provides reliable support for subsequent stratum freezing and reinforcement, and reduces problems such as poor reinforcement effect caused by inadequate freezing pipe layout.

[0020] Preferably, in S3, the reaction frame is fixed to the station floor and middle plate by steel pipe support and box columns, and the steel sleeve is connected in sections by bolts, which enhances the firmness of the connection between the reaction frame and the station structure, improves the stability and convenience of steel sleeve installation, facilitates the assembly and disassembly of steel sleeve, and can better withstand the forces generated during the tunnel boring machine's advancement, reducing the hidden dangers of steel sleeve deformation and displacement.

[0021] Preferably, the shield machine attitude calibration in S5 includes portal retesting and shield machine attitude retesting. After calibration, the attitude deviation is controlled to meet the requirements, and the shield machine attitude can be precisely adjusted to ensure that the shield machine's tunneling direction matches the portal attitude, reducing problems such as shield machine jamming and portal damage caused by attitude deviation, and ensuring the smooth tunneling and reception of the shield machine.

[0022] Preferably, the secondary grouting in S5 adopts the ring grouting method, with additional grouting holes at the end segments and full-ring grouting, which can improve the sealing and integrity of the water-tight ring on the outside of the segments, enhance the grouting effect, effectively seal the leakage channels between the excavated soil and the outer shell of the segments, and reduce potential hazards such as leakage at the tunnel entrance.

[0023] Preferably, in S6, the attitude of the tunnel boring machine is controlled based on the center line of the steel sleeve, and the advancing speed and thrust are controlled. This can further improve the attitude accuracy of the tunnel boring machine during the process of entering the steel sleeve, avoid problems such as deformation and leakage of the steel sleeve caused by improper advancing speed and thrust, and ensure that the tunnel boring machine advances smoothly inside the steel sleeve.

[0024] Preferably, in S8, the freezing pipes are pulled out one at a time from the center outwards. When pulling them out, grout is injected into the freezing holes. This can reduce the deformation of the frozen soil solidified body caused by the removal of the freezing pipes. At the same time, by injecting grout to fill the gaps in the freezing holes, the risk of thaw settlement is reduced, and the stability of the strata is further guaranteed.

[0025] Preferably, when sealing the freezing hole in S8, the hole opening pipe and freezing pipe are cut off, and after filling with mortar or concrete, the hole is sealed with a steel plate. This sealing structure can enhance the sealing performance of the freezing hole, prevent groundwater from seeping through the freezing hole, avoid affecting the surrounding strata and existing line structures, and ensure the stability of the strata after construction.

[0026] Preferably, cement single-fluid grout is used for the settlement compensation grouting of thaw settlement in S8. Grouting is carried out at intervals in the order of first the lower part and then the upper part, which can specifically compensate for the formation settlement generated after the frozen soil melts, reduce the influence of thaw settlement on the existing line and the surrounding environment, further improve the stability of the formation after construction, and reduce potential safety hazards. Description of the Drawings

[0027] Figure 1 is a schematic diagram of the construction process of an embodiment of the present invention; Detailed Embodiments

[0028] The present invention will be further described below in conjunction with specific embodiments. The purpose is only to better understand the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0029] As Figure 1 shown, this embodiment provides a shield receiving construction method for a water-rich soft formation, including the following steps:

[0030] S1. Ground vertical drilling and freezing pipe layout: Conduct vertical drilling on the ground at the shield receiving end in the protection area of the existing line. Freezing pipes are arranged in the drilling holes. The freezing pipes are connected to the salt water pipeline and the cooling water pipeline. The salt water pipeline and the cooling water pipeline are connected to the freezing station on the first basement floor of the station. Temperature measurement holes and exploration holes are arranged around the freezing pipes; The pressure test leak detection standard is strictly implemented in accordance with the requirements of the technical disclosure. The salt water pipeline has a pressure resistance of 0.6 MPa, and the cooling water pipeline has a pressure resistance of 0.3 MPa. After the pressure test, it is maintained for 1 hour, and if the pressure drop is not more than 0.05 MPa, it is qualified; If leakage occurs, the pressure needs to be immediately relieved, and the leakage part is repaired and then the pressure test is carried out again until it meets the standard.

[0031] Among them, the hole positions of the vertical drilling need to be accurately positioned according to the geological exploration report of the receiving end, the position of the existing line and the size of the portal. The drilling spacing is strictly controlled within 0.8 - 1.2 m; The freezing pipes use 20# low-carbon seamless steel pipes, and the pipe diameter is selected as φ127×5 mm; The temperature measurement holes use steel pipes with a diameter of φ40~φ63 mm; The exploration holes are divided into "dead corner" exploration holes and front exploration holes within the portal circle. The "dead corner" exploration holes have a specification of φ63 mm, are arranged 350 mm away from the edge of the portal circle, 3 in the upper part and 5 in the lower part, and the inclined layout angle is 25 - 45°, and they penetrate into the reinforced soil body not less than 1.2 m; The front exploration holes within the portal circle are evenly arranged in a "field" shape, with the number not less than 9, and penetrate into the reinforced soil body not less than 1000 mm. The layout of the exploration holes needs to be combined with the formation where the reinforced body is located and the distribution of the confined water layer, and the number of exploration holes is appropriately increased at positions with higher risks to ensure that the freezing reinforcement effect can be comprehensively detected; After all the exploration holes and temperature measurement holes are installed, the pressure test for leak detection needs to be carried out synchronously with the freezing pipes to prevent the influence of hole leakage on the accuracy of monitoring data.

[0032] Vertical drilling was carried out using a GXY-2Q drilling rig equipped with a Ф168mm diamond core drill bit. After drilling through the structural layer, a crane was used to lift the freezing pipe. During lifting, the freezing pipe had to be kept vertical to avoid collision with the borehole wall and causing collapse. Subsequently, a second drilling was carried out using a drill bit matched to the freezing pipe to the designed depth, ensuring that the distance between the bottom of the pipe and the bottom of the borehole was controlled at 100-200mm after the freezing pipe was lowered to the designed depth. After the freezing pipe was installed, the gap between the freezing pipe and the borehole wall was sealed with cement mortar, with the sealing height not less than 500mm below the borehole opening, to ensure the accuracy and stability of the freezing pipe layout and provide reliable support for subsequent stratum freezing and reinforcement. During drilling, the verticality of the borehole had to be monitored throughout the drilling process, and the deviation had to be controlled within the allowable range of the specifications. If any deviation occurred, it had to be corrected in time. Special lifting equipment was used to lift the freezing pipe, and the lifting points were evenly distributed to prevent deformation of the freezing pipe. The cement mortar sealing had to be compacted in layers to ensure a tight seal and to prevent air and water leakage during the later freezing process.

[0033] In S1, vertical drilling is performed using a drilling rig to open the hole. After penetrating the structural layer, the freezing pipe is hoisted and drilled a second time to the designed depth. This ensures the accuracy and stability of the freezing pipe layout, guarantees that the freezing pipe can reach the depth required by the design, provides reliable support for subsequent ground freezing and reinforcement, and reduces problems such as poor reinforcement effect caused by improper freezing pipe layout.

[0034] S2. Ground Freezing and Reinforcement and Effect Monitoring: Start the freezing station's chiller unit, supply brine to the freezing pipe, and reinforce the ground at the receiving end to form a frozen soil solidified and bonded to the diaphragm wall. Monitor the reinforcement progress through temperature measurement holes and probe holes, and adjust unit parameters accordingly. During the freezing process, a dedicated person must be on duty 24 hours a day to record unit operating parameters, brine temperature, frozen soil temperature, and probe hole feedback in real time, and establish a complete monitoring log. If any abnormal data is found, the cause must be analyzed immediately and adjustment measures taken to prevent the freezing effect from failing to meet standards.

[0035] The freezing station uses two TBSD620.1J type refrigeration units (150kW cooling capacity) (one in operation, one on standby), equipped with four IS150-125-400A brine pumps, four IS150-125-250 clean water pumps, and three DLT-80 type cooling towers (one on standby). The brine is a calcium chloride solution, with a concentration adjusted to 28%-30%. When preparing the calcium chloride solution, impurities must be removed. First, fill the brine tank with about 1 / 4 clean water, then start the brine pumps and gradually add solid calcium chloride until the concentration reaches the design requirements. The brine tank level should be maintained at 100cm to prevent overflow during brine backflow. Before starting the refrigeration unit, refrigerant charging and oiling operations must be completed, strictly following the equipment instruction manual. First, the refrigeration system should be leak-checked and flushed with nitrogen to ensure there are no leaks before charging refrigerant and adding oil. After starting the refrigeration unit, the active freezing phase begins. During active freezing, the brine temperature must drop below -18℃ for 7 days, below -24℃ for 15 days, and below -28℃ before the tunnel portal is removed. The temperature difference between the outgoing and return brine should not exceed 2℃, and the flow rate of a single freezing hole should not be less than 5 m³ / h. Active freezing must last at least 30 days before proceeding to the tunnel portal removal preparation phase. If the brine temperature and flow rate do not meet design requirements, the active freezing time must be extended, and the unit's operating parameters adjusted until the standards are met.

[0036] Temperature monitoring wells are used to monitor the frozen soil temperature in real time. The frozen wall thickness at the tunnel entrance is designed to be 4.0m, with a freezing range of 2m on each side of the tunnel lining segments. The average temperature of the frozen wall must reach -10℃, and the average temperature at the junction of the frozen wall and the diaphragm wall must not exceed -5℃. The frozen soil strength must meet the design specifications: compressive strength not less than 3.5MPa, flexural strength not less than 1.5MPa, and shear strength not less than 1.5MPa (at -10℃). Simultaneously, the freezing reinforcement effect is checked through boreholes. During borehole testing, drilling must be slow. If unfrozen soil or water seepage is found, testing must be stopped immediately, the freezing intensity in that area increased, and the freezing time extended until the borehole test shows no abnormalities. This ensures that the frozen soil reinforcement can effectively isolate groundwater and withstand the forces of the tunnel boring machine. In addition, frost heave control measures must be taken during the freezing process. If the frost heave force is too large and causes the ground to rise, pressure relief holes need to be drilled above the tunnel entrance to relieve soil pressure. At the same time, horizontal hot brine circulation holes can be arranged for pressure relief circulation to prevent the frost heave force from affecting the existing railway structure and surrounding strata.

[0037] S3. Installation and Backfilling of the Receiving End Steel Sleeve: A transition ring is welded onto the steel ring of the receiving end portal. A steel sleeve is installed on the outside of the transition ring. A reaction frame is installed at the bottom of the steel sleeve and fixed to the station structure. A mortar base is poured inside the steel sleeve and filled with fluidized solidified soil. Before installation, the design centerline of the shaft portal tunnel must be determined to ensure that the steel sleeve is placed in place in one go and avoid repeated movement. The positioning of the transition ring must be aligned with the designed tunnel segment posture. The upper half of the transition ring bevel is opened on the outside of the sleeve, and the lower half bevel is opened on the inside. During welding, it is necessary to ensure that the weld is full, free of slag inclusions, and free of incomplete welds. After welding, weld inspection is required to ensure welding quality.

[0038] In S3, the reaction frame is fixed to the station's base slab and middle slab via steel pipe supports and box-type columns. The steel sleeves are connected in sections by bolts, enhancing the robustness of the connection between the reaction frame and the station structure, improving the stability and ease of installation of the steel sleeves, facilitating assembly and disassembly, and better bearing the forces generated during tunnel boring machine (TBM) advancement, reducing the risk of deformation and displacement of the steel sleeves. The specific fixing method for the reaction frame is as follows: six evenly distributed A530mm (8mm wall thickness) steel pipe supports and three box-type columns are installed. Three horizontal steel pipe diagonal supports are installed on the upper surface of the station structure's base slab. The bottom crossbeam of the reaction frame uses three A530mm (8mm wall thickness) steel pipes tightly pressed against the crossbeam of the station base slab steps. Three box-type steel supports are installed at the top of the reaction frame, supporting the middle slab. The welding of the middle slab, base slab supports, diagonal braces, and embedded parts of the base slab must be secure, and each weld position must be inspected to eliminate the risk of slag inclusions and incomplete welds. When connecting steel sleeve sections, the bolts must be tightened diagonally to ensure that each section is tightly connected and the force is evenly distributed. After the connection is completed, the bolts must be tightened again to prevent loosening during the later tunneling process.

[0039] After the steel sleeve is installed, a 150mm thick M5 mortar base is poured inside the sleeve. The mortar base is poured at a 60° angle to the bottom of the steel sleeve and must extend into the tunnel portal to connect with the reinforced soil. After pouring, curing is required to ensure the mortar strength meets design requirements and to prevent head-stabbing when the cutterhead exits the reinforced soil. After the mortar base is cured, fluidized solidified soil is filled into the steel sleeve. The fluidized solidified soil is transported into the steel sleeve through a ground funnel and conveying pipeline. During the transportation process, the conveying speed must be controlled to avoid clogging the pipeline. The filling must be uniform to ensure there are no gaps inside the steel sleeve. After filling, the compaction must be checked. If gaps exist, additional filling is required to ensure the steel sleeve can effectively withstand the tunnel boring machine's propulsion pressure.

[0040] S4. Steel Sleeve Water Tightness Test: A water tightness test is conducted on the steel sleeve. The test standards are strictly implemented in accordance with the instructions. The pressure that the steel sleeve can withstand is calculated as twice the earth pressure. After pressurizing the steel sleeve with air, maintain the pressure for 12 hours. If the air pressure remains above 90%, the steel sleeve acceptance requirements are met. If there is any leakage, the test must be stopped immediately, the sealing quality must be checked and repaired, and the pressure test must be repeated until the pressure test requirements are met to avoid leakage and pressure loss during the shield tunneling process.

[0041] S5. Tunneling and Receiving Preparation of the Tunnel Boring Machine: After calibrating the attitude of the tunnel boring machine (TBM), tunnel at a constant speed. When the cutterhead enters the frozen soil solidification area, foam agent is added to improve the soil, and double-liquid grout is injected through the pre-reserved grouting holes in the segments to form a watertight ring. The TBM attitude calibration needs to be carried out three times, at positions 100m, 50m, and 20m away from the tunnel portal. The calibration includes re-measurement of the tunnel portal and re-measurement of the TBM attitude. The re-measurement of the tunnel portal needs to confirm the center coordinates of the tunnel portal, the circumferential diameter of the tunnel portal, and the elevation of the receiving shaft. The re-measurement of the TBM attitude requires at least two main surveyors, and the measurement results should be promptly reported to the supervisor and a third-party measurement verification. After calibration, the attitude deviation should be controlled to meet the requirements, with the horizontal deviation within ±20mm, the vertical deviation within ±15mm, and the allowable deviation of the pitch angle controlled within 2mm / m to avoid a pitching attitude. At the same time, the shield tail clearance should be controlled to be equal, and the articulated jacks should be prevented from being in the limit stroke state to ensure that the TBM tunneling direction matches the tunnel portal attitude.

[0042] In S5, the tunnel boring machine (TBM) attitude calibration includes portal re-measurement and TBM attitude re-measurement. After calibration, the attitude deviation is controlled to meet requirements, allowing for precise adjustment of the TBM attitude. This ensures the TBM's tunneling direction matches the portal attitude, reducing problems such as TBM jamming and portal damage caused by attitude deviations, and guaranteeing smooth TBM tunneling and reception. If the re-measurement reveals an attitude deviation exceeding the allowable range, a specific correction plan must be developed to gradually adjust the TBM attitude. Large-scale corrections at once are strictly prohibited to prevent disturbance to surrounding strata and existing railway structures.

[0043] The secondary grouting in S5 adopts the ring grouting method, with additional grouting holes at the end segments and full-ring grouting. This can improve the sealing and integrity of the water-tight ring on the outside of the segments, enhance the grouting effect, effectively seal the leakage channels between the excavated soil and the outer shell of the segments, and reduce potential hazards such as leakage at the tunnel entrance. The specific grouting requirements are as follows: The two-component grout uses a cement-water glass grout, consisting of component A (water + cement) and component B (water glass + water). The water glass concentration is 40Be', the cement grout water-cement ratio is 0.8~1.0, and the volume ratio of components A and B is 3:1~1:1. The initial setting time is controlled at approximately 1 minute. Secondary grouting should begin after the tunnel segment has exited the shield tail 5 rings, using a method of grouting every other ring, with 6 points per ring. Ten additional grouting holes are added to the last 6 rings, for a total of 16 grouting holes. Each of these 6 rings requires full-ring grouting, with 16 points per ring. The grouting pressure is controlled at 0.4~0.5 MPa, and the grouting volume per hole is 0.5 m³, with a maximum of 1 m³. During grouting, the grouting pressure and volume must be monitored in real time. If a sudden increase in pressure or abnormal grouting volume occurs, grouting must be stopped immediately, and construction can only continue after identifying and addressing potential hazards. In addition, when the cutterhead enters the frozen soil solidification area, the advancing speed should be controlled at 10~20mm / min, the thrust should be <8000KN, the soil chamber pressure should be controlled at 0.6-0.8bar, and the amount of foam agent added should be adjusted in real time according to the soil improvement effect to ensure good soil fluidity and avoid the cutterhead getting stuck. During the advancement process, continuous and uniform construction is required to ensure a certain soil pressure in the soil chamber and prevent the tunnel boring machine from rising due to empty soil chamber. At the same time, the injection of grease at the tail of the shield should be strengthened to prevent grout leakage at the tail of the shield.

[0044] S6. Tunnel Boring Machine (TBM) Entering the Steel Sleeve and Shutting Down: Control the TBM to enter the steel sleeve, adjust the propulsion parameters, and stop the machine after advancing to the preset position, removing the backfill material. When the TBM enters the steel sleeve, the attitude must be controlled with the center line of the steel sleeve as the reference. The deviation of the center line should be controlled within ±20mm, the propulsion speed <5mm / min, and the thrust <4000KN. Adjust the propulsion pressure in a timely manner according to the pressure gauge reading installed on the top of the steel sleeve to avoid excessive pressure causing deformation and leakage of the steel sleeve. If leakage occurs, open the grout discharge port on the rear plate cover of the steel sleeve to relieve pressure, and continue propulsion after the problem is resolved.

[0045] In S6, the tunnel boring machine (TBM) attitude is controlled using the centerline of the steel sleeve as a reference, which controls the advance speed and thrust. This further improves the attitude accuracy of the TBM during its entry into the steel sleeve, avoiding problems such as deformation and leakage of the steel sleeve caused by improper advance speed and thrust, and ensuring the smooth advancement of the TBM within the steel sleeve. After the TBM advances to the preset position, the backfill material in the empty chamber is removed without rotating the cutterhead. At the same time, the grout discharge pipe at the bottom of the steel sleeve is opened to drain the remaining grout and check for grout leakage in the sleeve. If leakage is found, it must be sealed in time to ensure a good seal in the steel sleeve, laying the foundation for subsequent dismantling work. In addition, during the advancement process, a dedicated person must observe the stability and deformation of the steel sleeve, increase the measurement frequency, and verify the control points. If any abnormality is found, the machine must be stopped immediately for handling.

[0046] S7. Installation of Curved Steel Plates at the Tunnel Portal: Remove the transition ring and install prefabricated curved steel plates at the tunnel portal. Bolt and weld the curved steel plates to the pipe segments and the portal steel ring. Before removing the transition ring, separate the steel sleeve transition ring from the embedded steel ring and push it forward as a whole, leaving sufficient operating space for welding the curved steel plates. A total of 12 curved steel plates are used. During installation, bolt connections are achieved using the pipe segment bolt holes and sliding grooves. The sliding grooves ensure that the bolt connections are not affected by the rotation of the pipe segment bolt holes, allowing the bolts to pass smoothly through the grooves and connect to the curved steel plates. After bolting, double-sided welding is performed. The welding must ensure full, dense welds that are tightly fitted to the pipe segments and the portal steel ring. After welding, the welding quality must be checked to prevent incomplete or incomplete welds and to prevent leakage at the tunnel portal.

[0047] S8. Dismantling of the freezing system and thaw settlement treatment: Stop the brine supply and remove the freezing pipes. After sealing the freezing holes, dismantle the freezing station and steel sleeve. Perform thaw settlement compensation grouting in the frozen soil thawing area and complete the shield machine reception. After stopping the brine supply, the supply should be stopped according to the freezing pipe groups. When removing the freezing pipes, follow the principle of "removing one at a time from the center outwards". The removal should be completed two days before the shield machine reception. During removal, grout should be injected into the freezing holes to reduce the deformation of the frozen soil solidification caused by the removal of the freezing pipes, and at the same time fill the gaps in the freezing holes to reduce the risk of thaw settlement.

[0048] In S8, the freezing pipes are removed one at a time from the center outwards. During removal, grout is injected into the freezing holes to reduce deformation of the frozen soil solidification caused by the removal of the freezing pipes. Simultaneously, the grout fills the voids in the freezing holes, reducing the risk of thaw settlement and further ensuring formation stability. The grout used is cement-clay grout or fly ash grout, and the injection volume is determined based on the size of the freezing holes and the formation conditions to ensure a dense, void-free grouting.

[0049] When sealing the freezing holes in S8, the hole opening pipe and freezing pipe are cut off, and after filling with mortar or concrete, they are sealed with steel plates. This sealing structure can enhance the sealing of the freezing holes, prevent groundwater from seeping through the freezing holes, avoid affecting the surrounding strata and existing line structures, and ensure the stability of the strata after construction. The specific sealing procedures must be strictly followed according to the instructions: the depth of the freezing pipe cut should not be less than 60mm, and the depth of the pipe cut into the structure should not be less than 60mm; the freezing pipe should first be filled with cement mortar of M10 or higher or concrete of C20 or higher, and then filled with quick-drying cement. The cut-off part of the hole should be sealed with a 10mm thick steel plate and coated with a ring of water-swellable sealant; two M12 expansion bolts should be symmetrically installed in the gaps inside the hole, and the hole opening should be flush with the surface with C30 sulfoaluminate micro-expansion cement. A 300×300×12 steel plate should be attached to the inside of the structure and fixed with four M12 anchors embedded in the pipe segments. The gap between the steel plate and the structural surface should be filled with epoxy resin. All freezing holes should be dried with compressed air and filled with cement mortar of strength not lower than M10 or concrete of strength grade not lower than C15, and the filling length of the hole opening section should not be less than 1500mm.

[0050] S8 grouting for thaw settlement compensation uses single-component cement grout, and grouting is carried out intermittently in the order of bottom to top. This can specifically compensate for the ground settlement caused by the thawing of frozen soil, reduce the impact of thaw settlement on existing lines and the surrounding environment, further improve the stability of the ground after construction, and reduce safety hazards. Melt-settlement compensation grouting utilizes pre-reserved grouting holes on the shield tunnel segments as grouting holes, covering the entire frozen area. The cement grout has a water-cement ratio of 1:0.8, a grouting pressure of 0.4~0.5MPa, and the grouting sequence is from bottom to top, with grouting every 1~2 segments, following the principle of multiple small-batch uniform grouting. Melt-settlement compensation grouting must be carried out immediately when the ground settlement exceeds 0.5mm in a day or the cumulative ground settlement exceeds 3mm. Grouting must be suspended when the ground heave reaches 3mm. The grouting volume is controlled at 15% of the thawed frozen soil volume, which can be adjusted according to ground deformation monitoring. The cessation standard for thaw-settlement grouting is: when the frozen wall has completely thawed and grouting is not performed, if the measured ground settlement continues for one month and does not exceed 0.5mm every half month, grouting can be stopped. During the grouting process, ground deformation monitoring and frozen soil temperature monitoring must be strengthened, and grouting parameters should be adjusted according to the monitoring data to ensure the grouting effect.

[0051] This shield tunneling receiving method for water-rich, soft strata is highly targeted, safe, controllable, standardized, and practical. It is specifically designed for the construction needs of water-rich silty soil and silty sand soft strata within existing railway protection areas. The core method employs vertical freezing combined with steel sleeve receiving. Through precise placement of freezing pipes, temperature measuring holes, and probe holes, and strict adherence to pressure testing standards, coupled with standardized drilling and freezing pipe installation processes, the accuracy and stability of the strata freezing reinforcement are ensured. During the freezing process, specialized freezing equipment is used to strictly control the brine concentration, temperature, and freezing time, with simultaneous 24-hour monitoring and frost heave control. This effectively forms a dense frozen soil body that reliably isolates groundwater and withstands the forces of shield tunneling, avoiding safety hazards caused by substandard freezing results. The steel sleeve installation utilizes transition ring welding, reaction frame fixing, and segmented bolt connections, combined with mortar base pouring and... The use of fluidized solidified soil filling, combined with rigorous water tightness tests, significantly improves the sealing and stability of the receiving process, effectively resisting the pressure of the tunnel boring machine (TBM) and reducing problems such as steel sleeve deformation and leakage. During the TBM tunneling stage, three attitude calibrations, scientific control of propulsion parameters, and secondary grouting of the diaphragm ring are used to precisely match the portal attitude, reducing the risk of TBM jamming, portal damage, and leakage. After receiving the TBM, a standardized process of removing frozen pipes, sealing frozen holes, and grouting to compensate for thawing settlement is adopted to effectively control stratum thawing settlement and avoid disturbance to existing structures and the surrounding environment. Various monitoring methods are strengthened throughout the process, and a complete ledger is established to ensure full control over construction safety and quality. At the same time, the construction process is convenient, the equipment is reasonably matched, and it is easy to operate and disassemble. It can provide a reliable reference for subsequent similar TBM receiving projects in water-rich and soft strata, significantly reducing construction risks and improving construction efficiency and project quality.

[0052] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A method for shield tunneling reception in water-rich, soft strata, characterized in that: Includes the following steps: S1. Vertical drilling and freezing pipe installation: Vertical drilling is carried out on the ground at the shield receiving end in the existing line protection area. Freezing pipes are installed in the drilling, and the freezing pipes are connected to brine pipes and cooling water pipes. The brine pipes and cooling water pipes are connected to the freezing station on the first basement floor of the station. Temperature measuring holes and probe holes are installed around the freezing pipes. S2. Ground freezing reinforcement and effect monitoring: Start the freezing station's refrigeration unit, transport brine to the freezing pipe, reinforce the ground at the receiving end to form a frozen soil solidified with the underground continuous wall, monitor the reinforcement status through temperature measurement holes and probe holes and adjust the unit parameters accordingly. S3. Installation and backfilling of steel sleeve at the receiving end: Weld a transition ring onto the steel ring of the receiving end portal, install a steel sleeve on the outside of the transition ring, set a reaction frame at the bottom of the steel sleeve and fix it to the station structure, pour a mortar base into the steel sleeve and fill it with fluidized solidified soil. S4. Water tightness test of steel sleeve: Conduct a water tightness test on the steel sleeve; S5. Tunneling and Receiving Preparation of Tunnel Boring Machine: After calibrating the attitude of the tunnel boring machine, tunnel at a constant speed. When the cutterhead enters the frozen soil solidification body, add foaming agent to improve the soil and inject double liquid grout through the grouting holes reserved in the segment to form a water-tight ring. S6. Tunnel Boring Machine Enters Steel Sleeve and Stops: Control the tunnel boring machine to enter the steel sleeve, adjust the propulsion parameters, and stop the machine after advancing to the preset position and emptying the backfill material. S7. Installation of curved steel plate at the tunnel portal: Remove the transition ring, install prefabricated curved steel plate at the tunnel portal, and bolt and weld the curved steel plate to the pipe segments and the tunnel portal steel ring; S8. Dismantling of the freezing system and thawing settlement treatment: Stop the brine supply and remove the freezing pipes. After sealing the freezing holes, dismantle the freezing station and steel sleeve. Perform thawing settlement compensation grouting in the frozen soil thawing area and complete the shield tunneling reception.

2. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: In S1, vertical drilling is performed by drilling rigs to open holes, penetrating the structural layer, then hoisting the freezing pipe and drilling a second time to the designed depth.

3. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: In S3, the reaction frame is fixed to the station's base plate and middle plate by steel pipe support and box-type columns, and the steel sleeves are connected in sections by bolts.

4. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: The shield machine attitude calibration in S5 includes portal re-measurement and shield machine attitude re-measurement. After calibration, the attitude deviation is controlled to meet the requirements.

5. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: In S5, secondary grouting adopts a ring grouting method, with additional grouting holes added to the end segments and full-ring grouting.

6. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: In S6, the shield machine's attitude, propulsion speed, and thrust are controlled by using the centerline of the steel sleeve as a reference.

7. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: In S8, the freezing pipes are removed one at a time from the center outwards, and grout is injected into the freezing holes during removal.

8. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: When sealing the freezing hole in S8, cut off the hole opening pipe and freezing pipe, fill with mortar or concrete, and then seal with a steel plate.

9. The shield tunneling method for receiving tunnels in water-rich, soft strata according to claim 1, characterized in that: S8 grouting for settling compensation uses single-component cement grout, and grouting is performed intermittently in the order of bottom to top.

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