A method for controlling stratum deformation of a tunnel under an airport runway by a pipe curtain method

Abstract

The present application relates to a pipe curtain tunnel underpass construction technology field, specifically to a pipe curtain tunnel underpass airport runway stratum deformation control method, thixotropic mud resistance reduction, in order to reduce the jacking resistance, increase the jacking force, and in order to prevent the occurrence of collapse, during pipe jacking, according to the needs, the injection of thixotropic mud between the gap of pipe wall and soil wall should be considered, forming mud jacket, reducing the friction between pipe wall and soil wall, the beneficial effect is: during pipe jacking, thixotropic mud is injected between the gap of pipe wall and soil wall, forming mud jacket, mud film is formed between slurry and pipe outer wall soil particles, this mud film not only can avoid the exosmosis of mud, but also shield the infiltration of soil pore water, grouting makes the outer wall of pipe form mud lubricating sleeve, thereby reducing the friction resistance during jacking, and further avoiding collapse, improving the deformation protection and control of stratum.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology using the pipe jacking method, specifically a method for controlling the deformation of the strata under an airport runway using the pipe jacking method. Background Technology

[0002] In the existing technology, during the construction of underpass tunnels using the pipe jacking method, the pipe jacking is affected by resistance. The thrust of the pipe jacking is the resistance that the steel pipe experiences during the jacking process, including the cutting pressure of the tool pipe, the frictional resistance of the pipe wall, and the air and water pressure of the tool pipe.

[0003] In existing technologies, due to the resistance to jacking during the jacking process, as the jacking head moves forward, the volume of the mud sleeve continuously expands. If grouting is not performed in time, the pressure of the mud sleeve will decrease and a suction effect will be generated, which can easily cause the collapse of the gap in the outer wall of the pipe, and the soil will collapse into the mud sleeve, making the mud sleeve incomplete. This will then cause changes in the tunnel soil layers, resulting in problems such as collapse and geological deformation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the deformation of the strata under an airport runway using the pipe jacking method, so as to solve the problems mentioned in the background art.

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

[0006] A method for controlling deformation of ground strata under an airport runway using a pipe-jacking method, the method comprising:

[0007] Step 1: Reinforcement construction. Launch and receiving shafts are installed on both sides of the main runway, and the retaining structure of the working pit is reinforced.

[0008] Step 2: Waterproofing treatment. Drainage ditches and drainage devices are set up in the working pit. An integral collar is installed at the opening inside the retaining pile, and a water-stopping device is welded and installed.

[0009] Step 3: Jacking construction. Destroy the retaining pile structure at the jacking inlet end. After demolition, quickly push the jacking machine head into the tunnel so that the cutterhead cuts into the solidified body. According to the data of the machine head deflection sensor, confirm the slight deflection of the machine head and adjust it by changing the direction of the cutterhead. Control the twist angle of the machine head to be less than ±0.2° until it enters the original soil or the receiving hole.

[0010] Step 4: When the tunneling machine starts and advances to the original soil, pay attention to the deviation data of the machine head axis. Confirm the slight deviation of the machine head axis and correct it by adjusting the resultant force center of the rear main jack to ensure that the axis deviation is less than ±2mm.

[0011] Step 5: When the pipe jacking machine is about to reach the receiving well, measure and adjust the steel pipe axis, accurately measure the machine head posture and position, ensure that the pipe jacking machine accurately enters the receiving tunnel, and control the tunneling speed and excavation face pressure. Before the formal jacking, a trial jacking must be carried out. The elevation and direction of the guide pipe falling onto the rail and derailing into the soil should be strictly controlled within 5mm before the formal jacking construction is carried out.

[0012] Step Six: Thixotropic Mud Drag Reduction. To reduce the resistance of the jacking process, increase the jacking force, and prevent collapse, thixotropic mud should be injected into the gap between the pipe wall and the soil wall during the pipe jacking process, forming a mud sheath to reduce the friction between the pipe wall and the soil wall.

[0013] S1: Materials for thixotropic mud

[0014] The main components of thixotropic mud include bentonite, alkali and water, and the auxiliary agents include lime paste, retarder and plasticizer.

[0015] S2: Mixing procedure for thixotropic mud

[0016] Put a measured amount of water into the mixing tank, and take a portion of the water to dissolve the alkali; during the mixing process, slowly add a measured amount of bentonite into the mixing tank and mix evenly; pour the dissolved alkali water into the mixing tank, mix evenly again, and let it stand for 12 hours before use.

[0017] S3: Initial Grouting

[0018] The arrangement of grouting holes is determined according to the pipe diameter. 3-4 grouting holes can be set in each section. The grouting holes have an air venting function. The well-mixed mud should be left to stand for a certain period of time before grouting. Before grouting, the grouting equipment should be checked by water injection. Grouting can only be carried out after confirming that the equipment is normal. The grouting pressure should be increased starting from 0.1 MPa. During grouting, the grouting should be carried out in the front and back order of the grouting hole section and should be synchronized with the pipe jacking.

[0019] S4: Slurry solidification

[0020] After the jacking is completed, the mud sleeve outside the pipe curtain should be cured. The curing grout can generally be made by adding an appropriate amount of fly ash to cement mortar to increase the consistency. After the grout has solidified (more than 24 hours), the pipeline should be removed and the cap should be replaced to seal the orifice. After the grouting is completed, all equipment should be cleaned.

[0021] S6: Slurry Transportation and Disposal

[0022] The mud conveying device consists of a mud pump for conveying mud and water, a mud pump for conveying cut soil and sand, a working shaft bypass device located in the propulsion shaft, mud delivery and discharge pipes, and mud and water hoses.

[0023] Preferably, the retaining structure in step one includes retaining piles and jet grouting piles. The foundation of the starting well and receiving well ends is pre-reinforced. Before the pipe curtain construction, the soil within 1.2m of the working well entrance and exit section is reinforced with double-pipe jet grouting piles. The reinforced foundation ensures good uniformity and self-support, with an unconfined compressive strength of not less than 1.0 MPa and a bearing capacity of not less than 250 kPa.

[0024] Preferably, the drainage construction in step two includes: setting up drainage ditches around or in the middle of the excavated foundation pit, and setting up a collection well every 25 meters or so, so that the seepage water and construction wastewater in the foundation pit can be collected in them, and then pumped into the surface sedimentation tank for treatment by sedimentation and other methods before being discharged into the municipal pipe network. Before the subbase is constructed, the lower half of the drainage ditch should be backfilled with clay in sections, and the upper half should be backfilled with permeable materials such as sand and gravel to form a drainage blind ditch, which is used to drain the seepage water in the flexible permeable pipe with the waterproof membrane.

[0025] Preferably, during the initial jacking in step three, since the tunneling machine is in the reinforced soil area and the soil on the front is relatively hard, the reinforced soil is cut slowly during construction, the rotation speed is maintained at 2-3 r / min, and the balance pressure setting value should be lower than the theoretical value, which is 0.5-1 cm / min.

[0026] Preferably, if mechanical failure, pipeline blockage, or joint leakage occurs during grouting in step six, the jacking can continue only after the problem is resolved. In long-distance pipe jacking construction, grouting forms a mud lubrication sleeve on the outer wall of the pipe, thereby reducing the frictional resistance during jacking.

[0027] Preferably, the mixing of drag-reducing mud in step six must be carried out strictly in accordance with the operating procedures. Catalysts, chemical additives, etc., must be stirred evenly to ensure uniform dissolution. After adding bentonite, it must be stirred thoroughly to ensure full hydration. After the mud is mixed, it should be left to stand for a certain period of time before use. Grouting is carried out by a grouting pump at the grout storage tank to press the mud into the main pipe inside the pipeline, and then press it out of the pipe wall through the grouting hole. During construction, pressure gauges are installed at the grouting pump, the tail of the pipe jacking machine, etc., to facilitate observation, control and adjustment of the grouting pressure.

[0028] Preferably, in step six of the jacking construction, the amount of drag-reducing mud used mainly depends on the size of the gap around the pipeline and the characteristics of the surrounding soil layer. Due to the loss of mud and the effect of groundwater, the actual amount of mud used is greater than the theoretical amount, generally reaching 4-5 times the theoretical value. However, appropriate adjustments should be made during construction based on soil conditions, jacking conditions, and ground settlement requirements.

[0029] Preferably, in step six, the mud pump rotates at a constant speed, but the mud discharge pump can change its speed through frequency modulation control. Together with the pressure regulating valve in the bypass device of the working well, the flow rate and pressure of the mud and water are controlled. At the engineering site, due to the long advance distance, there is an intermediate pump on the mud discharge side. The discharged mud is loaded onto trucks and transported after sedimentation.

[0030] Preferably, in step six, grouting of the grouting holes needs to be done synchronously. Synchronous grouting must be done before jacking. After synchronous grouting, the grout and the soil particles on the outer wall of the pipe form a mud film. During the jacking process, grout needs to be continuously replenished along the line.

[0031] Preferably, in step six, the mud conveying device is equipped with a flow meter and a density meter in the mud delivery and discharge pipes inside the working well, and the data are input into the calculation loop for mud and water management.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] To prevent collapse, this invention involves injecting thixotropic mud into the gap between the pipe wall and the soil wall during the pipe jacking process. This forms a mud sheath, and the slurry forms a mud film with the soil particles on the outer wall of the pipe. This mud film not only prevents the mud from seeping out but also shields the soil from pore water infiltration. Especially in long-distance pipe jacking construction, the key to controlling the jacking force is to minimize the jacking resistance. The most effective way to reduce jacking resistance is through grouting. Grouting forms a mud lubrication sleeve around the outer wall of the pipe, thereby reducing the frictional resistance during jacking, thus preventing collapse and improving the protection and control of stratum deformation. Attached Figure Description

[0034] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Please see Figure 1 The present invention provides a technical solution:

[0037] A method for controlling the deformation of ground strata under an airport runway using the pipe jacking method, the method comprising:

[0038] Pre-construction reinforcement for pipe jacking:

[0039] For reinforcement construction, launching and receiving shafts are set up on both sides of the main runway. The retaining structure of the working pit is reinforced. The retaining structure includes retaining piles and jet grouting piles. The foundation at the ends of the launching and receiving shafts is pre-reinforced. Before the pipe jacking construction, the soil within 1.2m of the section of the working shaft entering and exiting the tunnel is reinforced using double-pipe jet grouting piles. The reinforced foundation is ensured to have good uniformity and self-supporting properties, with an unconfined compressive strength of not less than 1.0 MPa and a bearing capacity of not less than 250 kPa.

[0040] By constructing a retaining wall for reinforcement, the stability during the jacking process is increased, the settlement problem during the jacking process is reduced, and the stability of the tunnel soil layer during the jacking process is improved.

[0041] Pre-implementation waterproofing treatment for pipe jacking:

[0042] Drainage ditches and drainage devices are set up in the working pit. An integral collar is installed at the opening inside the retaining pile, and a water-stopping device is welded and installed. The drainage construction includes: setting up open drainage ditches around or in the middle of the excavated pit, and setting up a collection well every 25 meters or so, so that the seepage water and construction wastewater in the pit can be collected in them. Then, the water is pumped into the surface sedimentation tank and treated by sedimentation and other methods before being discharged into the municipal pipe network. Before the subbase is constructed, the lower half of the drainage ditch should be backfilled with clay in sections, and the upper half should be backfilled with permeable materials such as sand and gravel to form a drainage blind ditch, which is used to drain the seepage water in the flexible permeable pipe with waterproof membrane.

[0043] By pre-installing drainage devices, the drainage efficiency during the jacking process can be improved, thus avoiding the risk of flooding.

[0044] jacking construction using the pipe jacking method:

[0045] After the tunnel portal retaining structure is demolished and it is confirmed that there are no steel bars or obstacles at the tunnel entrance, the tunnel boring machine (TBM) head should be pushed into the tunnel as soon as possible so that the cutterhead can cut into the reinforced soil, thereby shortening the exposure time of the front soil. Initially, because the TBM is in the reinforced soil area and the soil on the front is relatively hard, the TBM should cut the reinforced soil slowly in this area, maintaining a speed of 2-3 r / min. The balance pressure setting should be slightly lower than the theoretical value, and the advance speed should not be too fast, at 0.5-1 cm / min. When the TBM is tunneling in the reinforced soil area, the torque is relatively large, and the steel pipe is prone to twisting. Therefore, during the tunneling process, the data from the TBM head deflection sensor should be constantly monitored to confirm any slight deflection of the TBM head. Adjustments should be made by changing the cutterhead direction. The alarm value for the twist angle is ±0.2°, and the TBM head twist should not exceed ±0.2° until it enters the undisturbed soil or the receiving tunnel entrance. When the TBM first advances into the undisturbed soil, it is prone to head-knocking. To prevent the machine head from bumping, always pay attention to the deviation data of the machine head axis. Confirm even the slight deviation of the machine head axis. The axis deviation should not exceed ±2mm. Adjust the resultant force center of the rear main jack in time. If a downward bumping trend is found, immediately use the rear jack to correct the deviation.

[0046] When the pipe jacking machine is about to reach the receiving shaft, the axis of the steel pipe must be measured and adjusted to accurately determine the position of the machine head and ensure that the pipe jacking machine enters the receiving tunnel accurately. The tunneling speed and the pressure at the excavation face must be controlled. On the receiving working shaft side, after the concrete at the tunnel entrance is cleared, the pipeline should be advanced as soon as possible to shorten the tunnel entry time. The elevation and direction of the guide pipe (first section of pipe) restrict the jacking quality. Therefore, before the formal jacking, trial jacking must be carried out. The elevation and direction of the guide pipe falling onto the rail and derailing into the soil should be strictly controlled within 5mm.

[0047] By strictly limiting the initial precision of jacking, the accurate cutting of the soil layer during jacking can be ensured, thereby improving the stability of construction and reducing the magnitude of soil layer displacement and deformation.

[0048] Thixotropic mud drag reduction:

[0049] The thrust of pipe jacking is the resistance that the steel pipe experiences during the jacking process, including the cutting pressure of the tool pipe, the frictional resistance of the pipe wall, and the air and water pressure of the tool pipe. In order to reduce the jacking resistance, increase the jacking force, and prevent collapse, during the pipe jacking process, thixotropic mud should be injected into the gap between the pipe wall and the soil wall as needed to form a mud sheath, thereby reducing the friction between the pipe wall and the soil wall. The mud has fluidity and pumpability during transportation and injection.

[0050] ① Materials for thixotropic mud

[0051] Thixotropic mud is mainly composed of bentonite, mixed with alkali and water. In order to solidify and strengthen the thixotropic mud after jacking, lime paste can be added. However, in order to maintain fluidity during construction, retarders and plasticizers must also be added.

[0052] ② Mixing procedure for thixotropic mud

[0053] Put a measured amount of water into the mixing tank, and take a portion of the water to dissolve the alkali; during the mixing process, slowly add a measured amount of bentonite into the mixing tank and mix evenly; pour the dissolved alkali water into the mixing tank, mix evenly again, and let it stand for 12 hours before use.

[0054] ③ Precautions for thixotropic mud

[0055] The arrangement of grouting holes should be determined according to the pipe diameter. Generally, 3-4 holes can be set for each section, and they should have an air venting function. The well-mixed mud should be left to stand for a certain period of time before grouting. Before grouting, the grouting equipment should be checked by water injection. Grouting can only be carried out after confirming that the equipment is normal. The grouting pressure can be started at 0.1 MPa and adjusted according to the actual situation during the grouting process. During grouting, the grouting should be carried out in the order of the grouting hole positions and should be synchronized with the pipe jacking. If mechanical failure, pipe blockage, or joint leakage occurs during grouting, the jacking can only continue after the problem is solved. In long-distance pipe jacking construction, the key to jacking force control is to minimize the jacking resistance. The most effective way to reduce the jacking resistance is to carry out grouting. Grouting forms a mud lubricating sleeve on the outer wall of the pipe, thereby reducing the frictional resistance during jacking.

[0056] The mixing of drag-reducing mud must be carried out strictly in accordance with the operating procedures. Catalysts and chemical additives must be stirred evenly to ensure uniform dissolution. After adding bentonite, it must be stirred thoroughly to ensure full hydration. After the mud is mixed, it should be left to stand for a certain period of time before use. Grouting is carried out by a grouting pump at the grout storage tank to press the mud into the main pipe inside the pipeline, and then press it out of the pipe wall through the grouting hole. During construction, pressure gauges are installed at the grouting pump, the tail of the pipe jacking machine, etc., to facilitate observation, control and adjustment of the grouting pressure.

[0057] During jacking construction, the amount of drag-reducing slurry used depends mainly on the size of the voids around the pipeline and the characteristics of the surrounding soil layers. Due to slurry loss and the effects of groundwater, the actual amount of slurry used is much larger than the theoretical amount, generally reaching 4-5 times the theoretical value. However, during construction, appropriate adjustments must be made based on soil conditions, jacking progress, and ground settlement requirements.

[0058] During the jacking process of steel pipe, as the jacking head moves forward, the volume of the slurry sleeve continuously expands. If grouting is not performed in time, the pressure of the slurry sleeve will decrease, creating a suction effect. This can easily cause the collapse of the gaps in the outer wall of the pipe, allowing soil to fall into the slurry sleeve and leaving it incomplete. Therefore, synchronous grouting must be performed before jacking. After synchronous grouting, the grout and soil particles on the outer wall of the pipe form a mud film. This mud film not only prevents the slurry from seeping out but also shields the soil from pore water infiltration. However, some slurry is still lost during actual construction. Therefore, grouting needs to be continuously replenished along the jacking line during the jacking process.

[0059] ④ Slurry solidification

[0060] After the jacking is completed, the mud sleeve outside the pipe curtain should be cured. The curing grout can generally be made by adding an appropriate amount of fly ash to cement mortar to increase its consistency. After the grout has solidified (generally more than 24 hours), the pipeline should be removed and replaced with a cap to seal the borehole. After grouting is completed, all equipment should be thoroughly cleaned.

[0061] ⑤ Slurry transportation and disposal

[0062] The mud conveying device consists of a mud pump for conveying mud and water, a mud pump for conveying cut soil and sand, a working well bypass device located in the propulsion working well, mud delivery and discharge pipes, and mud and water hoses. A flow meter and a density meter are installed in the mud delivery and discharge pipes in the working well, and their data are input into the calculation loop for mud and water management.

[0063] In addition, the mud pump rotates at a constant speed, but the mud discharge pump can change its speed through frequency modulation control. Together with the pressure regulating valve in the bypass device of the working well, it controls the flow and pressure of mud and water. Furthermore, at this project site, due to the long advance distance, there is an intermediate pump on the mud discharge side. The discharged mud is then loaded onto trucks and transported off-site after sedimentation.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for controlling ground deformation when a pipe-jacking tunnel passes under an airport runway, characterized in that: The control method includes: Step 1: Reinforcement construction. Launching shafts and receiving shafts are set up on both sides of the main runway. The retaining structure of the working pit is reinforced. The retaining structure includes retaining piles and jet grouting piles. The foundation at the ends of the launching shaft and receiving shaft is pre-reinforced. Before the pipe jacking construction, the soil within 1.2m of the section of the working shaft entering and exiting the tunnel is reinforced using double-pipe jet grouting piles. The reinforced foundation is ensured to have good uniformity and self-supporting properties, with an unconfined compressive strength of not less than 1.0MPa and a bearing capacity of not less than 250kPa. Step 2: Waterproofing treatment. Drainage ditches and drainage devices are set up in the working pit. An integral collar is installed at the opening inside the retaining pile, and a water-stopping device is welded and installed. Step 3: Jacking construction. Destroy the retaining pile structure at the jacking inlet end. After demolition, quickly push the jacking machine head into the tunnel so that the cutterhead cuts into the solidified body. According to the data of the machine head deflection sensor, confirm the slight deflection of the machine head and adjust it by changing the direction of the cutterhead. Control the twist angle of the machine head to be less than ±0.2° until it enters the original soil or the receiving hole. Step 4: When the tunneling machine starts and advances to the original soil, pay attention to the deviation data of the machine head axis. Confirm the slight deviation of the machine head axis and correct it by adjusting the resultant force center of the rear main jack to ensure that the axis deviation is less than ±2mm. Step 5: When the pipe jacking machine is about to reach the receiving well, measure and adjust the steel pipe axis, accurately measure the machine head posture and position, ensure that the pipe jacking machine enters the receiving tunnel accurately, and control the tunneling speed and excavation face pressure. Before the formal jacking, a trial jacking must be carried out. The elevation and direction of the guide pipe falling off the rail and derailing into the soil should be strictly controlled within 5mm before the formal jacking construction is carried out. Step Six: Thixotropic Mud Drag Reduction. To reduce jacking resistance, increase jacking force, and prevent collapse, during pipe jacking, thixotropic mud should be injected into the gap between the pipe wall and the soil wall as needed to form a mud sheath, reducing friction between the pipe wall and the soil wall. Specific steps are as follows: S1: Materials for thixotropic mud Thixotropic mud is prepared from bentonite, alkali and water, and the auxiliary agents include: lime paste, retarder and plasticizer; S2: Mixing process for thixotropic mud Add a measured amount of water to the mixing tank, and use a portion of the water to dissolve the alkali. During the mixing process, slowly add a measured amount of bentonite to the mixing tank and mix well. Pour the dissolved alkali solution into the mixing tank, mix well again, and let it stand for 12 hours before use. S3: Initial Grouting The arrangement of grouting holes is determined according to the pipe diameter. 3-4 grouting holes are set for each section. The grouting holes have an air venting function. The thixotropic mud that is mixed evenly should be left to stand for a certain period of time before grouting. Before grouting, the grouting equipment should be checked by water injection. Grouting can only be carried out after the equipment is confirmed to be normal. The grouting pressure should be increased starting from 0.1 MPa. During grouting, the grouting should be carried out in the front and back order of the grouting hole section and should be synchronized with the pipe jacking. S4: Slurry solidification After the jacking is completed, the mud sheath outside the pipe curtain should be cured. The curing grout should be made of cement mortar with an appropriate amount of fly ash to increase the consistency. After the grouting body has solidified, the pipeline should be removed and replaced with a cap to seal the orifice. After the grouting is completed, all equipment should be cleaned. S5: Slurry Transportation and Disposal The mud conveying device consists of a mud pump for conveying mud and water, a mud pump for conveying cut soil and sand, a working shaft bypass device located in the propulsion shaft, mud delivery and discharge pipes, and mud and water hoses.

2. The method for controlling ground deformation under an airport runway using the pipe jacking method according to claim 1, characterized in that: The drainage construction in step two includes: setting up drainage ditches around or in the middle of the excavated foundation pit, and setting up a collection well every 25 meters or so, so that the seepage water and construction wastewater in the foundation pit can be collected in them, and then pumped into the surface sedimentation tank for sedimentation treatment before being discharged into the municipal pipe network. Before the subbase is constructed, the lower half of the drainage ditch should be backfilled with clay in sections, and the upper half should be backfilled with sand and gravel permeable material to form a drainage blind ditch, which is used to drain the seepage water in the flexible permeable pipe with the waterproof membrane.

3. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 1, characterized in that: If mechanical failure, pipeline blockage, or joint leakage occurs during grouting in step six, the jacking can only continue after the problem is resolved. In long-distance pipe jacking construction, grouting forms a mud sleeve around the outer wall of the pipe, thereby reducing the frictional resistance during jacking.

4. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 3, characterized in that: In step six, the mixing of thixotropic mud must be carried out strictly according to the operating procedures. The catalyst and chemical additives must be stirred evenly to ensure uniform dissolution. After adding bentonite, it must be stirred thoroughly to ensure full hydration. After the thixotropic mud is mixed, it should be left to stand for a certain period of time before use. Grouting is carried out by a grouting pump at the grouting tank to press the thixotropic mud into the main pipe inside the pipeline, and then press it out of the pipe wall through the grouting hole. During construction, pressure gauges are installed at the grouting pump and the tail of the pipe jacking machine to facilitate observation, control and adjustment of the grouting pressure.

5. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 4, characterized in that: In step six of the jacking construction, the amount of thixotropic mud used depends on the size of the voids around the pipeline and the characteristics of the surrounding soil layers. Due to the loss of thixotropic mud and the effect of groundwater, the actual amount of thixotropic mud used is greater than the theoretical amount, reaching 4-5 times the theoretical value. However, appropriate adjustments should be made during construction based on soil conditions, jacking conditions, and ground settlement requirements.

6. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 5, characterized in that: In step six, the mud pump rotates at a constant speed, but the mud discharge pump can change its speed through frequency modulation control. Together with the pressure regulating valve in the bypass device of the working well, it controls the flow rate and pressure of the mud and water. At the engineering site, due to the long advance distance, there is an intermediate pump on the mud discharge side. The discharged thixotropic mud is loaded onto trucks and transported after sedimentation.

7. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 6, characterized in that: In step six, grouting must be done synchronously. Synchronous grouting must be done before jacking. After synchronous grouting, the grout and the soil particles on the outer wall of the pipe form a mud film. During the jacking process, grout needs to be continuously replenished along the line.

8. The method for controlling ground deformation of a pipe-jacking tunnel under an airport runway according to claim 1, characterized in that: In step six, the mud conveying device is equipped with a flow meter and a density meter in the mud delivery and discharge pipes inside the working well. The data detected by the flow meter and density meter are input into the calculation loop for mud and water management.

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