A construction method for a slurry shield river channel

Abstract

The present invention discloses a construction method for a slurry shield in a river channel, which includes drilling an advanced borehole by a drill rig, preparing slurry, preparing a slurry agent, grouting and reinforcing and testing, building a mud film with the slurry agent, and performing an operation of opening the chamber. The beneficial effects of the present invention are as follows: By using in-tunnel advanced reinforcement grouting, the disadvantages of traditional grouting being restricted by river water and the surrounding environment are avoided, a protective body is formed above the face and the cutterhead, the stability of the face is ensured for a period of time, and a stable operation environment is provided for the cutter-changing operation. At the same time, a new material slurry agent is used to inject around the shield and into the soil chamber to form a dense mud film with good airtightness on the face, which ensures that groundwater inflow is cut off during the operation, protects the stability of the face, and provides a feasible scheme for opening the chamber under adverse conditions at the river bottom.

Description

Technical Field

[0001] The invention relates to a construction method for a shield river channel, in particular to a construction method for a slurry shield river channel, and belongs to the technical field of river channel construction. Background Art

[0002] Opening operations at the riverbed are technically difficult and dangerous, so the shield machine should be fully inspected before crossing the river. At the same time, the riverbed strata should be surveyed in detail to fully understand the construction environment and formulate targeted safety construction plans. In short, good strata and surrounding environment should be selected actively to avoid adverse situations such as changing cutters at the riverbed.

[0003] Slurry balance shield machines are mainly suitable for geological conditions with high groundwater pressure and high soil permeability coefficient. They are widely used in the construction of subway tunnels across rivers and seas. After the shield machine stops unexpectedly at the bottom of the river, directly building a mud membrane and opening the chamber under pressure usually fails; and traditional ground reinforcement methods are difficult to carry out due to the restrictions of river water. Forcing construction often takes a long time, is costly, and is difficult to guarantee the effect. Summary of the invention

[0004] The purpose of the present invention is to provide a construction method for a slurry shield river channel in order to solve the problem.

[0005] The present invention achieves the above-mentioned purpose through the following technical scheme: A construction method for a slurry shield river channel, comprising the following steps

[0006] Step 1: Drilling advance holes with a drilling rig. Place the drilling rig on the platform of the scaffolding, drill holes on the shield, and set flanges at the hole openings for connection and fixing.

[0007] Step 2: Prepare slurry. The grouting slurry uses cement-water glass slurry. The cement uses PO.42.5 ordinary Portland cement. The water-cement ratio of the cement slurry is 1:1. The concentration of the water glass stock slurry is 40 degrees Baume. Water is used to prepare the water glass dilution; cement slurry: water glass dilution = 1:1;

[0008] Step 3: Prepare the pulping agent, add clean water to the pulp truck, and start the agitator; start the pulping pump, and after it runs normally, slowly add 1.5 to 2 packs of shield pulping agent HS-1 into the funnel, and then add 1.5 to 2 packs of shield pulping agent HS-3. After the shield pulping agent HS-1 and the shield pulping agent HS-3 are fully dissolved without lumps, add 8 packs of shield pulping agent HS-2. After the addition is completed, the pulping pump runs for 10 minutes and then stops;

[0009] Step 4: Grouting reinforcement and testing. The backstepping grouting method is adopted. After the drilling is completed, first inject phosphoric acid sodium silicate for sealing to prevent the slurry from gushing and flowing away during the grouting process. After the sealing slurry has solidified, start injecting the cement-sodium silicate double-fluid slurry. After the pressure reaches 2 - 2.5 MPa, retract the drill pipe and carry out the grouting operation for the next section. Repeat this cycle until the hole is completed. After all the drilling and grouting operations are completed, conduct a pressure-holding test.

[0010] Step 5: Build a mud film with the grouting agent. Inject the prepared grouting agent slurry through the injection port in the middle shield of the shield machine to fill and wrap the soil pores around the entire shield machine body.

[0011] Step 6: Open the chamber operation. After the pressure-holding test is successful, carry out the operation in accordance with the pressure-controlled chamber opening procedure.

[0012] As a further scheme of the present invention: In the above-mentioned Step 1, it specifically includes:

[0013] ① Adjust the scaffolding platform according to the actual site conditions. Use the oil cylinders extended on both sides, the segments on both sides, and the bridge in the middle as the support points for the operation platform. The platform board is fully covered with stainless steel walkway boards. To counteract the impact force during drilling, it is necessary to set platform braces at the rear of the platform according to the actual conditions. After the platform is erected, set safety fences around the platform.

[0014] ② Place the drill on the platform and pad square timbers at the bottom of the drill to adjust to meet the drilling angle, that is, ensure that the direction of the drill pipe is consistent with the direction of the hole reserved in the shield body. Before drilling, debug the drill to make the equipment operate normally.

[0015] ③ The diameter of the hole reserved on the shield body of the shield machine is 125 mm, the diameter of the drill pipe and the drill bit of the drill is 42 mm, and the drilling depth is 15 m. When the drill pipe retracts near the cutting edge, it is necessary to closely monitor the change of the soil chamber pressure. If the soil chamber pressure rises, stop injecting and retract the drill pipe. At the same time, rotate the cutter head 1 - 2 circles to prevent the slurry from entering the soil chamber and jamming the cutter head.

[0016] As a further scheme of the present invention: In the above-mentioned Step 2, it specifically includes:

[0017] ① The grouting equipment is a vane mixer. To ensure the uniformity of the slurry and prevent precipitation during the grouting interval, two self-made mixing and storage slurry tanks with a capacity of 0.4 cubic meters are provided. To facilitate slurry suction, more than two slurry extraction ports are set on the outer side of the storage slurry tank to ensure the supply of slurry during large-flow grouting.

[0018] ② Mix the slurry according to the selected slurry ratio parameters. After the cement slurry is mixed, it is filtered through a 1×1 mm mesh sieve to ensure the uniformity of the slurry. The end standard for single-hole grouting is controlled by combining fixed quantity and fixed pressure.

[0019] As a further scheme of the present invention: The grouting agent in the above-mentioned Step 3 specifically includes:

[0020] Shield slurry agent HS-1: It is composed of large and medium molecular weight polyacrylic acid salts, cellulose salts, polyacrylonitrile salts, anti-calcification agents, modified soils, synergistic additives, etc., and is used to prepare the initial basic slurry;

[0021] Shield slurry agent HS-2: It is composed of inert minerals with different particle gradations, raw plant fibers, rubber powder, single seal, asbestos particles and other substances;

[0022] Shield slurry agent HS-3: It is composed of different large and medium molecular weight polyacrylates, polyacrylonitrile salts, cellulose salts, vinyl multi-monomer copolymers, positive electrode gel, micropore plugging expansion agent, modified soil and synergistic additives.

[0023] As a further solution of the present invention: in the step 4, the grouting operation specifically includes:

[0024] ① After the grouting operation of the upper 4 holes is completed from top to bottom, the pressure holding test can be carried out. Turn on the automatic pressure holding system, adjust the pressure to the theoretical opening pressure value calculated in the confirmation preparation stage, use the reserved holes in the soil bin to discharge the mud in the bin, stop discharging the mud when the liquid level drops to the 3-9 o'clock position, and start recording the air compressor loading data to test the pressure holding capacity;

[0025] ② The pressure test needs to be continued for 2 hours. If the air compressor loading time / air compressor unloading time + air compressor loading time is less than 10% within 2 hours, it proves that the air tightness is good. During the process, the river surface inspection is strengthened. If no mud or obvious bubbles appear on the river surface during the inspection, it means that the pressure test is successful, and the shield machine can continue to excavate or carry out pressure-carrying operations;

[0026] ③If the pressure holding test fails, continue grouting into the remaining lower holes until the pressure holding test succeeds.

[0027] As a further solution of the present invention: in the step 4, the grouting standard specifically includes:

[0028] ① Quantitative standard: When the grouting volume reaches 1.5 to 2 times of the designed grouting volume and the pressure still does not rise, measures such as quick-setting slurry can be taken to end the grouting of the hole;

[0029] ② Constant pressure standard: During the grouting process, the pressure gradually increases and the flow rate gradually decreases. When the grouting pressure reaches the designed grouting pressure and the amount of grouting is very little or no, the grouting of this hole can be ended.

[0030] As a further solution of the present invention: in the step 5, the slurrying agent injection specifically includes:

[0031] ①Injection into the soil bin: The injection point is first selected to inject the slurry into the mud bin from the upper grouting port of the shield machine. When grouting, the sizing agent can be injected while discharging a part of the original slurry in the mud bin, but the discharged amount must be less than the injected amount, and part of the slurry is squeezed into the formation.

[0032] ②When the amount of the injected sizing agent reaches the capacity of the soil bin or the mud pressure rises to be greater than the formation pressure, start the cutter head to rotate slowly for several circles and then stop. If the mud pressure can be kept stable, the injection can be stopped. If the pressure can be maintained without dropping for 2 hours, the slurry can be discharged into the bin.

[0033] The beneficial effects of the present invention are as follows: By using the advanced reinforcement grouting in the tunnel, the disadvantages of the traditional grouting restricted by the river water and the surrounding environment are avoided. A protective body is formed above the heading face and the cutter head, ensuring the stability of the heading face for a period of time and providing a stable working environment for the cutter changing operation. At the same time, a new type of sizing agent is used to inject around the shield and into the soil bin to form a dense mud film with good airtightness at the heading face, ensuring that the groundwater inflow is blocked during the operation and protecting the stability of the heading face, providing a practical and feasible solution for opening the bin under the adverse conditions at the river bottom. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the construction process of the present invention. Detailed Embodiments

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] Please refer to Figure 1 , a construction method for a slurry shield in a river channel, including the following steps

[0038] Step 1: The drill rig drills an advanced borehole. Place the drill rig on the platform of the scaffolding, drill a borehole on the shield body, and set a flange at the hole position for connection and fixation.

[0039] Step 2: Prepare the slurry. The grouting slurry uses a cement-sodium silicate slurry. The cement uses PO.42.5 ordinary Portland cement, and the water-cement ratio of the cement slurry is 1:1; the original concentration of the sodium silicate is 40 Baume degrees, and the sodium silicate dilution is prepared by mixing with water; cement slurry: sodium silicate dilution = 1:1.

[0040] Step 3: Configure the pulp-making agent. Add clean water into the pulp truck and start the agitator. Start the pulp-making pump. After it operates normally, slowly add 1.5 - 2 packages of shield pulp-making agent HS-1 into the funnel, and then add 1.5 - 2 packages of shield pulp-making agent HS-3. After the shield pulp-making agent HS-1 and shield pulp-making agent HS-3 are fully dissolved without lumps, add 8 packages of shield pulp-making agent HS-2. After the feeding is completed, let the pulp-making pump run for 10 minutes and then stop it;

[0041] Step 4: Grout reinforcement and testing. Adopt the backward grouting method. After the drilling is completed, first inject phosphoric acid sodium silicate for sealing to prevent the slurry from gushing and flowing away during the grouting process. After the sealing slurry coagulates, start injecting the cement-sodium silicate double-fluid slurry. After the pressure reaches 2 - 2.5 MPa, retract the drill rod and carry out the grouting operation for the next section. Repeat this process until the hole is completed, and conduct a pressure-holding test after all the drilling and grouting operations are completed;

[0042] Step 5: Build a mud film with the pulp-making agent. Inject the prepared pulp-making agent slurry through the injection port in the middle shield of the shield machine to fill and wrap the soil pores around the entire shield body;

[0043] Step 6: Open the chamber operation. After the pressure-holding test is successful, carry out the operation in accordance with the pressure-holding chamber opening procedure.

[0044] In the embodiment of the present invention, in the said Step 1, it specifically includes:

[0045] ① Adjust the scaffolding platform according to the actual situation on site. Use the oil cylinders extended on both sides, the segments on both sides and the bridge in the middle as the support points for the operation platform. The platform board is fully covered with stainless steel walkway boards. To offset the impact force during drilling, it is necessary to set platform bracing at the rear of the platform according to the actual conditions. After the platform is erected, set safety guardrails around the platform;

[0046] ② Place the drill on the platform and pad square timbers at the bottom of the drill to adjust to meet the drilling angle, that is, ensure that the direction of the drill rod is consistent with the direction of the hole reserved on the shield body; and debug the drill before drilling to make the equipment operate normally;

[0047] ③ The diameter of the hole reserved on the shield body of the shield machine is 125 mm, the diameter of the drill rod and drill bit of the drill is 42 mm, and the drilling depth is 15 m. When the drill rod retracts to near the cutting edge, it is necessary to closely monitor the change of the soil chamber pressure. If the soil chamber pressure rises, stop injecting and retract the drill rod, and at the same time rotate the cutter head 1 - 2 circles to prevent the slurry from entering the soil chamber and jamming the cutter head.

[0048] In the embodiment of the present invention, in the said Step 2, it specifically includes:

[0049] ①The pulping equipment is a vane mixer. To ensure the uniformity of the slurry and prevent precipitation during the grouting interval, two self-made mixing and storage tanks with a capacity of 0.4 cubic meters are provided. To facilitate slurry suction, more than two slurry extraction ports are provided on the outer side of the storage tank to ensure the supply of slurry during large-flow grouting;

[0050] ②Mix the slurry according to the selected slurry mixing ratio parameters. After the cement slurry is mixed, it is filtered through a 1×1mm mesh sieve to ensure the uniformity of the slurry. The end standard of single-hole grouting is controlled by combining fixed quantity and fixed pressure.

[0051] In the embodiment of the present invention, in the third step, the pulp-making agent specifically includes:

[0052] Shield pulp-making agent HS-1: It is composed of polyacrylate salts, cellulose salts, polyacrylonitrile salts, calcium anti-agent, modified soil, synergistic additives, etc. with large and medium molecular weights, and is used to prepare the initial basic slurry; between the polymer materials with large and medium molecular weights and the beneficial particles (active soil or bentonite cut), the particles adsorb each other to form a network structure framework covering the entire mud space, surrounding the free water and soil particles in its structure to increase the viscosity and shear force of the mud and reduce the filtration loss, and complete the initial slurry for slurry making and shaft protection.

[0053] Shield pulp-making agent HS-2: It is composed of inert minerals with different particle size distributions, raw plant fibers, rubber powder, single seal, asbestos particles, etc.; its use is to block the pores of sandy soil layers, gravel layers, weathered rock layers, etc., and cooperate with other materials to form a dense mud film to prevent collapse and stabilize the excavation face.

[0054] Shield pulp-making agent HS-3: It is composed of polyacrylate salts, polyacrylonitrile salts, cellulose salts, vinyl multi-monomer copolymers, positive electric gum, micropore-blocking swelling agent, modified soil, synergistic additives, etc. with different large and medium molecular weights. During tunneling, it combines with the beneficial particles in the cutter head and the cut soil body to enhance the structural and rheological properties inside the mud, which is beneficial to suspending and carrying drill cuttings, and the micropore-blocking material enters the soil pores, and the slight swelling effect enhances the shaft protection and stabilizes the excavation face.

[0055] In the embodiment of the present invention, in the fourth step, for the grouting operation, it specifically includes:

[0056] ①After the grouting process completes the grouting operation of the upper 4 holes from top to bottom, the pressure holding test can be carried out. Open the automatic pressure holding system, adjust the pressure to the theoretical opening pressure value calculated in the preparation stage, use the reserved hole in the soil bin to discharge the slurry in the bin, stop discharging the slurry when the liquid level drops to the 3-9 o'clock position, and start recording the air compressor loading data for the pressure holding capacity test;

[0057] ②The pressure holding test needs to be continuously carried out for 2 hours. If the air compressor loading time / (the air compressor unloading time + the air compressor loading time) within 2 hours is less than 10%, it proves good airtightness. During the process, strengthen the inspection of the river surface. If no mud gushing or obvious bubbles appear on the river surface are found during the inspection, it indicates that the pressure holding test is successful, and the shield machine can continue to advance or the operation of entering the chamber under pressure can be carried out subsequently;

[0058] ③If the pressure holding test fails, continue to grout the remaining lower holes until the pressure holding test is successful.

[0059] In the embodiment of the present invention, in the fourth step, for the grouting standard, it specifically includes:

[0060] ①Quantitative standard: When the grouting volume reaches 1.5 - 2 times of the designed grouting volume and the pressure still does not rise, measures such as using quick-setting slurry can be taken to end the grouting of this hole;

[0061] ②Constant pressure standard: During the grouting process, the pressure gradually rises and the flow rate gradually decreases. When the grouting pressure reaches the designed grouting pressure and the slurry absorption volume is very small or there is no slurry absorption, the grouting of this hole can be ended.

[0062] In the embodiment of the present invention, in the fifth step, for the injection of the grouting agent, it specifically includes:

[0063] ①Injection into the soil chamber: The injection point is first selected to inject into the slurry chamber from the upper grouting port of the shield machine. During injection, the grouting agent can be injected while discharging a part of the original slurry in the slurry chamber, but the discharged amount must be less than the injected amount, and part of the slurry is squeezed into the formation;

[0064] ②When the injected amount of the grouting agent reaches the capacity of the soil chamber or the slurry pressure rises to be greater than the formation pressure, start the cutter head to rotate slowly for several circles and then stop. If the slurry pressure can be kept stable, the injection can be stopped. If the holding pressure does not drop for 2 hours, the slurry can be discharged and the chamber can be entered.

[0065] Embodiment 2

[0066] Please refer to Figure 1 , a construction method for a slurry shield in a river channel. Taking the 8.8 - meter slurry shield tunneling construction of the section from the No. 1 intermediate ventilation shaft to the No. 2 shield shaft of the Hengfan section of Guangzhou Metro Line 18 as an example, the shield length of the section from the No. 1 intermediate ventilation shaft to the No. 2 shield shaft of the Hengfan section of Guangzhou Metro Line 18 is 2834.957 m. It needs to cross the Jiaomen Waterway (the river surface width is about 330 m, the crossing length is about 505 m, and the tunnel top is about 16 m away from the riverbed), the Xili Waterway (the river surface width is about 200 m, the crossing length is about 471 m, and the tunnel top is about 17 m away from the riverbed). The buried depth of the shield tunnel is 19.2 m - 27.8 m, the line is generally north - south, the shield excavation section is 8.8 m, and the maximum operating speed reaches 160 km / h.

[0067] Hydrogeological Overview

[0068] The shield machine stopped under the Xili Waterway. The geological map shows that the strata from top to bottom are: <2-2> silty fine and medium sand, <2-3> silty medium and coarse sand, <2-1B> silty soil, <2-3> silty medium and coarse sand. The main strata traversed by the tunnel body are: <2-3> silty medium and coarse sand, <7H> strongly weathered granite. The distance from the tunnel roof to the Xili Waterway riverbed is about 17m, and the water depth is about 5-7m. Water-related activities such as navigation and fishing in the river channel are frequent, and vertical reinforcement conditions are not available. Therefore, it is necessary to use the pre-reserved advanced grouting holes of the shield machine for in-tunnel advanced reinforcement.

[0069] The pre-reserved advanced grouting holes designed for the shield machine have played an important role. The protection of the shield advanced holes is crucial. Usually, high-quality tail shield grease is injected into all the reserved grouting holes until the grease extrudes from the outside of the shield body before the start. A small amount of quick-setting cement can be applied at the outside outlet of the shield body to level the hole opening to prevent sundries in the strata from entering the reserved grouting hole channel.

[0070] During the advanced grouting process, attention should be paid to the reverse spraying of the grout from the hole opening, which may pollute the equipment. After the drill pipe penetrates into the hole channel, phosphoric acid sodium silicate should be injected first for sealing. During the grouting process, the operator should closely monitor the pressure change to prevent gushing. At the same time, the equipment on the shield machine should be covered with tarpaulin to prevent pollution and damage when the grout gushes.

[0071] During the grouting process, the grout will inevitably flow into the soil chamber. Therefore, the cutter head should rotate intermittently, and the original slurry in the soil chamber should be replaced with newly prepared slurry according to the actual situation on-site to prevent a large amount of double-fluid grout from solidifying and jamming the cutter head in the chamber. At the same time, the sealing slurry of phosphoric acid sodium silicate is corrosive, and the personnel entering the chamber should wear protective clothing to avoid being corroded and injured by the residual acidic slurry.

[0072] Strata such as silt strata, sand strata (water-rich silty fine sand), cobble-gravel strata, strata with uneven hardness, fault zones, and composite strata have poor self-stability, are prone to collapse, and are difficult to open the chamber. This technology is also applicable to opening the chamber and changing the cutter for such poor strata.

[0073] Working principle: Through the pre-reserved advanced grouting holes of the shield machine, double-fluid grout is injected into the soil in front of and above the cutter head to play a reinforcement role, and the chamber opening operation is carried out under the protection of the reinforced body. First, high-concentration bentonite is injected into the excavation chamber for pressure maintenance; bentonite slurry is injected around the shield body through the pre-reserved radial holes of the shield body to protect the shield body and avoid difficulties in re-pushing caused by the grout wrapping the shield body; the advanced grouting holes reserved at the top of the shield body are used to grout and reinforce the strata in front of the cutter head.

[0074] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0075] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A construction method for a muddy water shield river channel, characterized in that: It includes the following steps Step 1: The drilling rig drills advanced boreholes. Place the drilling rig on the platform of the scaffolding, drill holes on the shield body, and set up a flange at the orifice for connection and fixation; Step 2: Prepare the slurry. The grouting slurry uses cement-sodium silicate slurry. The cement uses PO.42.5 ordinary Portland cement, and the water-cement ratio of the cement slurry is 1:1; the original concentration of the sodium silicate slurry is 40 Baume degrees, and the sodium silicate dilution is prepared by mixing with water; cement slurry: sodium silicate dilution = 1:1; Step 3: Prepare the slurry agent. Add clean water to the slurry truck and start the agitator; start the slurry pump. After normal operation, slowly add 1.5 - 2 bags of shield slurry agent HS-1 to the funnel, and then add 1.5 - 2 bags of shield slurry agent HS-3. After the shield slurry agent HS-1 and shield slurry agent HS-3 are fully dissolved without lumps, add 8 bags of shield slurry agent HS-2. After the feeding is completed, stop the slurry pump after running for 10 minutes; Step 4: Grouting reinforcement and testing. Use the backward grouting method. After the borehole is completed, first inject phosphoric acid sodium silicate for sealing to prevent the slurry from gushing and flowing away during the grouting process. After the sealing slurry sets, start injecting the cement-sodium silicate double-fluid slurry. After the pressure reaches 2 - 2.5 MPa, retract the drill pipe and carry out the grouting operation for the next section. Repeat this cycle until the hole is completed, and conduct a pressure-holding test after all borehole grouting is completed; Step 5: Build a mud film with the slurry agent. Inject the prepared slurry agent slurry through the injection port in the middle shield of the shield machine to fill and wrap the soil layer pores around the entire shield body; Step 6: Open the chamber operation. After the pressure-holding test is successful, carry out the operation according to the pressure-controlled chamber opening procedure.

2. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In the said Step 1, it specifically includes: ① Adjust the scaffolding platform according to the actual situation on site. The operation platform uses the oil cylinders extended on both sides, the segments on both sides, and the bridge in the middle as support points. The platform board is fully covered with stainless steel walkway boards. To offset the impact force during drilling, it is necessary to set platform braces at the rear of the platform according to the actual conditions. After the platform is erected, set up safety guardrails around the platform; ② Place the drilling rig on the platform and pad wooden blocks at the bottom of the drilling rig to adjust to meet the drilling angle, that is, ensure that the direction of the drill pipe is consistent with the direction of the reserved hole in the shield body; and debug the drilling rig before drilling to make the equipment operate normally; ③ The diameter of the reserved hole on the shield body of the shield machine is 125 mm, the diameter of the drill pipe and drill bit of the drilling rig is 42 mm, and the drilling depth is 15 m. When the drill pipe retracts to near the cut, it is necessary to closely monitor the change of the soil chamber pressure. If the soil chamber pressure rises, stop injecting and retract the drill pipe, and at the same time rotate the cutter head 1 - 2 circles to prevent the slurry from entering the soil chamber and jamming the cutter head.

3. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In the said Step 2, it specifically includes: ① The slurry preparation equipment is a vane mixer, and two self-made mixing and storage slurry barrels with a capacity of 0.4 cubic meters are set up. There are more than two slurry taking ports on the outside of the storage slurry barrels to ensure the supply of slurry during large-flow grouting; ② Mix the slurry according to the selected slurry ratio parameters. After the cement slurry is mixed, it is filtered through a 1×1 mm mesh sieve to ensure the uniformity of the slurry. The end standard of single-hole grouting is controlled by combining fixed quantity and fixed pressure.

4. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In the said Step 3, the slurry agent specifically includes: Shield slurry agent HS-1: It is composed of large and medium molecular weight polyacrylic acid salts, cellulose salts, polyacrylonitrile salts, anti-calcium agent, modified soil, and synergistic additives, and is used to prepare the initial base slurry; Shield slurry agent HS-2: It is composed of inert minerals with different particle gradations, raw plant fibers, rubber powder, single seal, and asbestos particles; Shield slurry agent HS-3: It is composed of different large and medium molecular weight polyacrylates, polyacrylonitrile salts, cellulose salts, vinyl multi-monomer copolymers, positive gel, micropore plugging expansion agent, modified soil and synergistic additives.

5. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In the step 4, the grouting operation specifically includes: ① After the grouting operation of the upper 4 holes is completed from top to bottom, the pressure holding test can be carried out. Turn on the automatic pressure holding system, adjust the pressure to the theoretical opening pressure value calculated in the confirmation preparation stage, use the reserved holes in the soil bin to discharge the mud in the bin, stop discharging the mud when the liquid level drops to the 3-9 o'clock position, and start recording the air compressor loading data to test the pressure holding capacity; ② The pressure test needs to be continued for 2 hours. If the air compressor loading time / air compressor unloading time + air compressor loading time is less than 10% within 2 hours, it proves that the air tightness is good. During the process, the river surface inspection is strengthened. If no mud or obvious bubbles appear on the river surface during the inspection, it means that the pressure test is successful, and the shield machine can continue to excavate or carry out pressure-carrying operations; ③If the pressure holding test fails, continue grouting into the remaining lower holes until the pressure holding test succeeds.

6. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In the step 4, the grouting standard specifically includes: ① Quantitative standard: When the grouting volume reaches 1.5 to 2 times of the designed grouting volume and the pressure still does not rise, the quick-setting slurry measures are taken to end the grouting of the hole; ② Constant pressure standard: During the grouting process, the pressure gradually increases and the flow rate gradually decreases. When the grouting pressure reaches the designed grouting pressure and the amount of grouting is very little or no, the grouting of this hole can be ended.

7. The construction method for a muddy water shield river channel according to claim 1, characterized in that: In step 5, the injection of the pulping agent specifically includes: ① Injection of soil bunker: The injection point is first selected from the grouting port on the upper part of the shield machine to inject into the mud water bunker. During grouting, you can inject the slurry agent while discharging part of the mud in the mud water bunker, but the amount of discharge must be less than the amount of injection, so that part of the mud is squeezed into the formation; ② When the amount of injected slurrying agent reaches the capacity of the soil bin or the mud water pressure rises to be greater than the formation pressure, turn on the cutter head and rotate it slowly for a few circles and then stop. If the mud water pressure can remain stable, the injection can be stopped. When the pressure does not drop for 2 hours, the slurry can be discharged into the bin.

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