A method for adjusting the starting attitude of a large-diameter shield assisted by shield body grouting

Abstract

The present invention provides a method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting. The specific steps of the method are as follows: when the attitude is abnormal during the shield starting process, first inject bentonite with a viscosity greater than 60 s through the radial holes and advanced grouting holes of the shield to form a bentonite hoop at the front and middle shield positions for protection; after the injection of bentonite is completed, inject a double slurry of cement and water glass through the advanced grouting holes and radial grouting holes on the shield side of the deviation correction side, and form a bulge on the outside of the shield at the injection hole position; after the injection of the double slurry is completed, adjust the attitude of the shield machine during the shield tunneling process, and inject the double slurry again during the shield attitude adjustment process; after the shield machine attitude adjustment is completed, inject a dispersant to dissolve the double slurry bulge. The present invention changes the stress state by injecting slurry through the shield, without the need to add additional auxiliary equipment, quickly and effectively completes the attitude deviation correction treatment, and solves the problem of shield starting attitude adjustment.

Description

Technical Field

[0001] The present invention relates to the field of shield tunneling construction, and particularly to a method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting. Background Art

[0002] The shield attitude is an important part of the control of tunneling parameters and also an important standard for the acceptance of the formed tunnel. Therefore, during the tunneling process, great attention should be paid to the actual value and trend value of the shield attitude to avoid abnormal shield attitude caused by untimely control measures or equipment failures, which may lead to a chain reaction in the quality of the formed tunnel and even more seriously, lead to route relocation. In the construction process of a conventional shield, when an abnormal attitude occurs, because the self-weight of the shield structure is small and an articulated device is configured to assist in correcting the shield attitude, however, for a large-diameter shield machine, due to its large excavation section, large self-weight, large diameter-length ratio and no articulated device, it is very easy to have abnormal attitude phenomena during the construction process.

[0003] During the starting process of a large-diameter shield, a short sleeve is often used to extend the portal steel ring for a large-diameter slurry shield to provide the basic conditions for building pressure for the slurry and also the basic guarantee for reducing water and sand gushing during shield starting. However, the size design of the short sleeve needs to be consistent with the portal steel ring to avoid the phenomenon of the shield body being stuck. In order to ensure that the shield machine corresponds to the design center of the portal steel ring and at the same time prevent damage to the lower part of the starting portal sealing device due to pressure, the overall spatial position of the shield machine is specially increased by 2-3‰ on the basis of the design gradient. During the starting tunneling process of the shield, according to the principle of shield construction, it can be seen that the building void between the shield body entering the short sleeve and the steel ring part is relatively large, and at the same time, the reaction force is small, so the shield attitude is prone to large fluctuations. The common rolling angle is 15mm / m, the pitching angle is ±1mm / m, and the azimuth angle is ±2mm / m, resulting in difficult attitude control; when the shield machine has an abnormal attitude when entering the portal ring, it will cause the shield machine and the portal ring to be non-concentric, and the portal seal will fail due to uneven gaps. If the gap is too small, the hinge plate will be damaged, and if the gap is too large, the hinge plate will turn outwards, which may cause water and sand gushing, and even cause settlement or collapse of the end. As the shield machine advances forward, in the guide structure and the portal steel ring section, due to the lack of external formation constraints, the attitude continuously drops under the influence of the self-weight of the shield machine. When the reinforced section turns into the original soil layer section, the formation bearing capacity changes, and the vertical attitude often drops, and the common vertical trend becomes -2mm / m or greater, which is also often called the "diving" phenomenon. When the shield machine completely leaves the reinforced body and enters the original formation, due to the large overall weight of the shield machine and no articulated device, to prevent the deformation of the reaction frame and the leakage of the portal sealing device during the shield starting section, the tunneling parameters are controlled to be in a state of low propulsion pressure and low slurry tank pressure. At the same time, if the formation is some moderately weathered argillaceous siltstone and moderately weathered mudstone layers, their slurry-making ability is strong, resulting in high-concentration slurry infiltrating into the formation and generating an upward buoyancy force on the rear segments, increasing the segment floating amount, which jointly has a certain impact on the vertical attitude.

[0004] At present, due to the high strength of the reinforced stratum at the start of the shield, the friction generated by the stratum on the shield machine increases. If the posture of the shield machine is adjusted, the shield will be stuck, resulting in the inability of the shield machine to start normally. Therefore, during the start of the shield, the posture abnormalities in different areas are handled by some special methods. For example, the posture abnormality of the tunnel ring is generally handled by adding steel plates on the outside and continuing to weld. This method will increase the workload and have a greater safety risk. When the shield starts to plunge, the general treatment method is to increase the thrust of the lower cylinder or adjust the segment selection method to increase the advance amount of the lower segment and change the stress state of the shield machine. This method causes the formed tunnel to fail to be built according to the design axis, which may cause a change in line. In addition, the posture deviation of the existing shield is large during the start of the shield, and methods such as adding auxiliary cylinders to adjust, escape, or adding additional counterweights to change the center of gravity of the shield machine are also used. These methods have complex construction procedures and long cycles, and have a certain impact on the overall structural design of the shield machine. In order to avoid the impact of abnormal posture on construction progress and quality during the construction of large-diameter shield machines, corrective measures are needed specifically for the abnormal posture of the segments when the shield enters the original stratum from the reinforcement body during the initial stage of the shield machine. Summary of the invention

[0005] In view of the difficulty in adjusting the posture of a large-diameter shield machine, the present invention provides a method for adjusting the initial posture of a large-diameter shield machine by assisting shield grouting. The method mainly injects different slurries at different points on the shield body, and changes the friction between the shield body and the formation through the slurry, thereby achieving the purpose of adjusting the posture of the shield machine and solving the abnormal posture situation that occurs after the shield machine enters the formation from the reinforcement body at the initial stage of the shield machine.

[0006] In order to achieve the above technical purpose, the present invention provides a method for adjusting the posture of a large-diameter shield machine with the assistance of shield grouting. The method is a correction measure for the phenomenon of the shield machine posture falling down and drifting horizontally when the shield machine enters the clay layer from the reinforcement area during the shield starting process. The specific steps are as follows:

[0007] (1) During the initial start of the shield tunneling, the shield machine's excavation posture is monitored through the shield machine's guidance system. When the posture is abnormal, bentonite with a viscosity greater than 60s is first injected through the shield body's radial holes and advance grouting holes to form a bentonite hoop at the front middle shield position for protection; the bentonite is mixed 12 hours in advance to make it expand;

[0008] (2) After the injection of bentonite is completed, a double slurry of cement and sodium silicate is injected through the shield's advanced grouting holes and radial grouting holes on the deviation correction side, and a bulge is formed on the outside of the shield body at the injection hole position; the injection of the double slurry is carried out by on-site mixing and injection using a grouting machine and a mixing tank. The ratio of cement to sodium silicate in the double slurry is 1:1 to 1:1.3, the setting time is 20s to 25s, and the injection volume per point is 0.4m 3 ~0.6m 3 , and the grouting pressure is within 0.5 bar;

[0009] (3) After the injection of the double slurry is completed, during the shield tunneling process, the attitude of the shield machine is adjusted so that it deviates in the direction of the double slurry injection point. During the adjustment process, the friction between the shield body shell and the formation is increased on the double slurry injection side, thereby increasing the horizontal / vertical partition pressure difference. At the same time, the slurry blocks wrapped on the shield body are equivalent to an enlarged excavation section, causing the shield machine to shift towards the grouting position under the action of formation stress, jointly making the attitude approach the target value;

[0010] (4) During the shield attitude adjustment process, when an emergency occurs, before each ring of shield tunneling and during the tunneling process, the double slurry is injected again through the same shield advanced grouting holes and radial grouting holes in step (2) to further increase the friction generated by the slurry. The injection volume per point is controlled at 0.2 - 0.3m 3 ;

[0011] (5) After the shield machine attitude adjustment is completed, check the excavation of the formation by the shield slurry through the segment grouting hole in a timely manner, and inject a dispersant to dissolve the double slurry injected in steps (2) and (4) to avoid excessive disturbance to the formation or continuous influence on the shield attitude control.

[0012] The preferred technical solution of the present invention: In step (1), the difference is calculated according to the three-dimensional state of the shield machine tested by the shield machine guidance system and the tunnel design axis, and the shield attitude is controlled according to the horizontal front point, midpoint, rear point and vertical front point, midpoint, rear point given in the construction technical disclosure. When the difference is greater than 30 mm, bentonite injection starts.

[0013] The preferred technical solution of the present invention: The injection process of bentonite in step (1): Connect the bentonite injection pipeline to the shield's radial holes and advanced grouting holes. When the shield attitude is abnormal, continuously inject bentonite into the radial holes and advanced grouting holes as the shield tunnels, injecting while pushing, with the pressure controlled within 0.4 bar and the volume controlled at 1.5 times the construction building void, and inject and keep the shield tunneling forward continuously for 2m.

[0014] Preferred technical solution of the present invention: In step (2), during the injection of the double slurry, a friction reducer can be injected into the shield advanced grouting holes or radial grouting holes symmetric to the double slurry injection points. The friction reducer includes one of waste oil, foaming agent, bentonite or water.

[0015] Preferred technical solution of the present invention: In step (2), the grouting points of the double slurry are divided into four areas: up, down, left and right. During grouting, it is injected at the corresponding points of the shield tail according to the attitude correction requirements. The diffusion range of the slurry does not exceed 45°, and a frustum-shaped slurry block is formed by condensation outside the shield body. The reaction force of the friction with the formation acts on the shield attitude correction. According to the shield machine attitude adjustment requirements, the injection volume is increased or decreased by 0.1 - 0.2 m 3 each time.

[0016] Preferred technical solution of the present invention: The grouting process in step (2) includes the following steps: a. Prepare the grouting machine and the mixing tank in advance and move them to the operation area; b. Install the injection port ball valve, grouting head and four-way joint for grouting at the advanced grouting holes and radial grouting holes to be grouted. The four-way joint interfaces are respectively the cement slurry interface, the sodium silicate pipe interface, the pressure relief pipe and the ball valve, and connect the cement pipe and the sodium silicate pipe of the double-fluid grouting machine to the cement slurry interface and the sodium silicate pipe interface of the four-way joint through the grouting pipeline respectively; c. Mix the cement through the mixing tank, and at the same time reserve the corresponding volume in the sodium silicate storage tank according to the scale; d. After preparation, open the pressure relief ball valve, start debugging the grouting pump. After normal debugging, close the pressure relief valve, open the cement slurry pipe ball valve and the sodium silicate slurry pipe ball valve, and start grouting.

[0017] Preferred technical solution of the present invention: The injection of the double slurry in step (2) is carried out by a double-fluid grouting pump and a multi-functional slurry mixing tank; the multi-functional slurry mixing tank includes a cement mixing tank and a sodium silicate storage tank arranged on one side of the cement mixing tank. The sodium silicate storage tank is provided with a scale; the cement mixing tank is provided with a stirring mechanism. On the upper side of the cement mixing tank body, there is a tool cabinet and a cement placement platform. At the lower part of the cement mixing tank body, there is a cement slurry outlet tank. The inlet of the cement slurry outlet tank is communicated with the slurry outlet of the cement mixing tank, and a filter screen is provided at the slurry outlet; slurry outlet ball valves are respectively arranged at the bottoms of the sodium silicate storage tank and the cement slurry outlet tank. The sodium silicate storage tank and the cement slurry outlet tank are respectively connected to the double-fluid grouting pump through slurry pipes and are simultaneously injected through the sodium silicate grouting pipe and the cement grouting pipe respectively.

[0018] A preferred technical solution of the present invention: The emergency situations in step (4) include: ① the posture of the shield machine exceeds the control of the design specification by ±50mm; ② the deviation difference of the shield posture gradually increases, resulting in a trend growth rate of the shield machine greater than 1mm / m; ③ the minimum shield tail gap is less than 5mm and the maximum cylinder stroke difference is greater than 5cm, which seriously affects the selection of the segments; ④ the quality of the formed tunnel is damaged at 3 places / ring, the maximum misalignment is greater than 2cm, and there is 1 leakage at / ring.

[0019] A preferred technical solution of the present invention is as follows: in the step (5), the injection time of the dissolving liquid is when the shield machine is stopped after adjusting its posture, and the injection time of the dissolving liquid is controlled at the critical point where the posture begins to change to 2 mm / m according to the vertical posture trend of 0 to 1 mm / m; the dissolving liquid is injected into the grouting hole / radial hole above the position of the double slurry injection hole and the adjacent position, and the immersion time is controlled to be 8 to 12 hours, and then the excavation is resumed. After resuming the excavation, the excavation parameters are observed, including the total thrust, the partition pressure and the changes in the posture. At the same time, the slurry filling condition behind the shield segment is checked to be consistent with the normal section construction parameters. Otherwise, the above steps are repeated for adjustment again until the construction status is normal.

[0020] The preferred technical solution of the present invention is as follows: the ratio of cement to water glass in the double liquid slurry is 1:1, the setting time is 20s, the friction reducer is bentonite to water in a weight ratio of 3:20, and the viscosity is 50-60s after fermentation for 12 hours.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention changes the stress state by injecting slurry into the shield body, without adding additional auxiliary equipment, and quickly and effectively completes the posture correction process, avoiding the chain reaction of quality defects and line adjustments in the formed tunnel, solving the problem of shield initial posture adjustment, greatly saving construction costs and manpower, while ensuring the construction period nodes, and generating good social and economic benefits.

[0023] (2) In the present invention, bentonite is injected before grouting. After the bentonite is injected, it is filled in the entire gap between the shield body and the formation. The bentonite fills the formation gaps well, closes the groundwater channel, and blocks the groundwater in front of the cutter head and behind the shield tail, forming a bentonite hoop for protection, preventing the slurry from spreading over a large area and causing the shield to be wrapped, thereby affecting the normal start of the shield.

[0024] (3) The double slurry injection operation of the present invention is simple. With the special structure of the stirring tank, the slurry ratio can be better controlled to ensure the grouting quality and effect. The tools can also be collected together for easy management.

[0025] (4) The injection time of the double slurry in the present invention is carried out before tunneling and during tunneling, shortening the construction interval, being able to well exert the friction force, and during tunneling, according to the urgency of the situation, for example, in hard rock strata, it can be selected to inject while pushing, injecting double-fluid slurry on one side to increase the friction force, and injecting a friction reducer on the symmetric other side to reduce the friction force, preferably balancing the stress state;

[0026] (5) After the attitude adjustment of the present invention is completed, a dispersant is injected to dissolve the slurry, avoiding the existence of friction force of the double-fluid slurry in the formation, which affects the shield attitude and the filling density of the building void. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the grouting system of the present invention;

[0028] Figure 2 is a state diagram of bentonite injection in the present invention;

[0029] Figure 3 is a stress state diagram after double-slurry grouting in the present invention;

[0030] Figure 4 is a schematic diagram of the filling position of double-slurry grouting in the present invention.

[0031] In the figure: 1 - cement mixing tank, 2 - sodium silicate storage tank, 3 - mixing mechanism, 4 - tool cabinet, 5 - cement slurry discharge tank, 6 - filter screen, 7 - grouting pump, 8 - cement grouting pipe, 9 - sodium silicate grouting pipe, 10 - four-way joint, 11 - solidified double-slurry convex block, 12 - segment, 13 - cutter head, 14 - cleaning valve, 15 - cement placement platform, 16 - shield shell, 17 - formation, 18 - bentonite hoop, 19 - shield body advanced grouting hole and radial grouting hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described below with reference to the drawings and embodiments. The attached Figures 1 to 4 are all drawings of the embodiments, which are drawn in a simplified manner and are only used to clearly and concisely illustrate the purpose of the embodiments of the present invention. The following technical solutions shown in the drawings are the specific solutions of the embodiments of the present invention and are not intended to limit the scope of the present invention to be protected. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0034] The grouting device used in the embodiment, such as Figure 1 and Figure 2 shown, includes a double-fluid grouting pump 7, a multi-functional slurry mixing tank, and a grouting pipeline; the multi-functional slurry mixing tank includes a cement mixing tank 1 and a sodium silicate storage tank 2 provided on one side of the cement mixing tank 1. A stirring mechanism 3 is provided in the cement mixing tank 1. A support frame is provided at the bottom of the cement mixing tank 1, and a lifting lug is provided at the top. The sodium silicate storage tank 2 is fixed to the side of the cement mixing tank 1. The sodium silicate storage tank 2 is a transparent tank body, and a scale is provided on the tank body. The stirring mechanism 3 includes a stirring motor provided at the top of the cement mixing tank 1, a stirring shaft located in the cement mixing tank 1, and stirring blades dispersedly arranged at equal intervals along the stirring shaft. The stirring shaft extends from the top to the bottom of the cement mixing tank 1 and is rotationally connected to the tank body. A tool cabinet 4 and a cement placement platform 15 are provided on the upper side of the tank body of the cement mixing tank 1. The cabinet door of the tool cabinet 4 is opened on the side. The cement placement platform 5 is located on the top of the tool cabinet 4 and is flush with the top surface of the cement mixing tank 1. A tool placement rack is provided in the tool cabinet 4. A cement slurry outlet tank 5 is provided at the lower part of the tank body of the cement mixing tank 1. The cement slurry outlet tank 5 is integrated with the cement mixing tank 1, and the cement slurry outlet tank 5 and the sodium silicate storage tank 2 are arranged on the same side. The inlet of the cement slurry outlet tank 5 is communicated with the slurry outlet of the cement mixing tank 1, and a filter screen 6 is provided at the slurry outlet; slurry outlet ball valves are respectively provided at the bottoms of the sodium silicate storage tank 2 and the cement slurry outlet tank 5. The sodium silicate storage tank 2 and the cement slurry outlet tank 5 are respectively communicated with the double-fluid grouting pump 7 through slurry pipes. As Figure 1 shown, the grouting pipeline includes a cement grouting pipe 8, a sodium silicate grouting pipe 9, and a four-way joint 10. The first port of the four-way joint 10 is connected to the shield advanced grouting hole and the radial grouting hole 19, and a one-way valve is provided at the connection part. The second port and the third port of the four-way joint 10 are respectively communicated with the double-fluid grouting pump 7 through the cement grouting pipe 8 and the sodium silicate grouting pipe 9, and a pressure relief valve is connected to the fourth port of the four-way joint 10.

[0035] The present invention will be further described below in conjunction with embodiments. Taking the abnormal attitude during the tunneling process at the initial stage of a certain construction project as an example, this project uses a 12m large-diameter slurry shield for construction. The whole machine of the shield machine is heavy and there is no articulation device. When designing the shield starting guide platform for the construction project, the guide platform structure is raised by 2-3 cm according to the tunnel design axis. During the shield starting process, a short sleeve is used to extend the portal steel ring to provide basic conditions for building pressure for the slurry and at the same time reduce the basic guarantee of water and sand gushing during shield starting. According to the principle of shield construction, the building voids between the shield body and the short sleeve and the steel ring part are relatively large, and the reaction force is relatively small. Therefore, the shield attitude is prone to large fluctuations. The common rolling angle is 15mm / m, the pitch angle is ±1mm / m, and the azimuth angle is ±2mm / m. In this project, the pitch angle is -2mm / m and the azimuth angle is +4mm / m. At the same time, the current tunneling attitude shows that the horizontal front point exceeds 50mm, which jointly leads to the problem of attitude control. As the shield tunnels out of the solidified body and enters the original stratum, it is easy to have a diving phenomenon. During the shield starting process, the difference between the three-dimensional state of the shield machine measured by the shield machine guidance system and the tunnel design axis is calculated. When the shield starts tunneling to the 11th ring, the vertical and horizontal attitudes are abnormal. The azimuth angle changes from +3mm / m to +4mm / m, and the pitch angle changes from 0mm / m to -2mm / m, and it is in a 2‰ downhill section. After the project tunnels to the 11th ring, the horizontal attitude front point is 50mm and the middle point is 24mm; the vertical attitude front point is -7mm and the middle point is 3mm.

[0036] Calculated according to the length of the shield machine main body and the width of 11-ring segments, when the shield machine completely leaves the solidified body and enters the original stratum, the tunnel burial depth of this project is 11.31m - 24.46m, the geology is moderately weathered argillaceous siltstone and moderately weathered mudstone, the rock stratum strength is 0.96 - 9.17MPa, and the comprehensive surrounding rock classification of the tunnel is grade V. The groundwater includes upper stagnant water and bedrock fissure water, and the permeability is medium - strong. Based on the comprehensive analysis of the above stratum and tunneling progress, combined with the principle that the shield attitude correction control standard is less than 5mm, the shield attitude is corrected frequently and slowly, so that the trend value gradually decreases and reaches the special predetermined target value. This project formulates a correction plan by adjusting the horizontal attitude by 50mm and the vertical attitude by 10mm, and it is expected to return to the design value after 10 rings; due to the special situation of this project, it is impossible to directly adjust the attitude when the shield attitude is abnormal. To solve the above problems, the method in the present invention is used to adjust the abnormal situation of the shield attitude of this project, and the specific steps are as follows:

[0037] (1) During the shield starting process, calculate the difference between the three-dimensional state of the shield machine tested by the shield machine guidance system and the tunnel design axis, and control it according to the horizontal front point, midpoint, rear point and vertical front point, midpoint, rear point of the shield attitude given in the construction technical disclosure. When the difference is greater than 30 mm, first inject bentonite with a viscosity greater than 60 s through the shield body radial holes and advanced grouting holes to form a bentonite collar at the front and middle shield positions for protection; the bentonite is mixed 12 h in advance to make it expand. The injection process of the bentonite is to connect the bentonite injection pipeline to the shield body radial holes and advanced grouting holes. When the shield attitude is abnormal, continuously inject bentonite into the radial holes and advanced grouting holes as the shield advances, injecting while pushing, with the pressure controlled within 0.4 bar and the volume controlled at 1.5 times the construction building void. Inject and keep the shield advancing continuously for 2 m.

[0038] (2) After the bentonite injection is completed, inject a double slurry of cement and water glass through the shield advanced grouting holes and radial grouting holes on the deviation correction side, and form a bulge on the outside of the shield body at the injection hole position; the injection of the double slurry is carried out through the above grouting device. The ratio of cement to water glass in the double liquid slurry is 1:1, and the setting time is 20 s. The injection volume at each point is 0.4 m 3 ~0.6 m 3 , with the grouting pressure within 0.5 bar; during the injection process of the double slurry, a friction reducer can be injected into the shield advanced grouting holes or radial grouting holes symmetrical to the double slurry injection points. The friction reducer is selected with bentonite: water in a weight ratio of 3:20, and its viscosity is 50 - 60 s after fermentation for 12 h. The grouting points of the double slurry are divided into four areas: up, down, left and right. During grouting, inject at the corresponding points at the shield tail according to the attitude deviation correction requirements. For example, when the shield machine needs to correct to the left, inject the double slurry into the shield body radial holes and advanced grouting holes at the 9 o'clock position on the left. When the shield machine needs to correct to the upper left, inject the double slurry into the shield body radial holes and advanced grouting holes at the 9 o'clock position on the left and the 12 o'clock position above. The slurry diffusion range does not exceed 45°, and a frustum-shaped slurry block is formed by condensation on the outside of the shield body, and the shield attitude deviation correction is reacted by the friction force with the formation. According to the shield machine attitude adjustment requirements, the injection volume per time is increased or decreased according to 0.1 - 0.2 m 3 . The grouting process includes the following steps:

[0039] a. Prepare the grouting machine and mixing tank in advance to the operation area; before grouting, check the relevant materials and tools in the multi-functional mixing bucket, dredge the shield body radial injection holes and connect the grouting equipment and the cement and water glass slurry tanks through hoses;

[0040] b. Install ball valves, grouting heads and tees for grouting at the advanced grouting holes and radial grouting holes to be grouted. The interfaces of the tees are respectively the cement slurry interface, the sodium silicate pipe interface, the pressure relief pipe and the injection port ball valve, and connect the cement pipe and the sodium silicate pipe of the double-fluid grouting machine to the cement slurry interface and the sodium silicate pipe interface of the tee through the grouting pipeline;

[0041] c. Mix the cement in the mixing tank, and at the same time reserve the corresponding volume in the sodium silicate storage tank in advance according to the scale;

[0042] d. After preparation, open the pressure relief ball valve, inject 0.05m 3 of clear water into the formation to test the pressure of the radial holes, and at the same time ensure that the equipment is running normally. Start debugging the grouting pump. After normal debugging, close the pressure relief valve, open the cement slurry pipe ball valve and the sodium silicate slurry pipe ball valve, and start grouting; adjust and control according to the vertical attitude. At present, the trend of the shield attitude compared with the target attitude needs to be corrected to the second quadrant. Combined with the distribution form of the radial grouting holes of the shield machine, select to open the hole and grout at the 11 o'clock position, and ensure that the slurry solidifies above the radial grouting hole at the 11 o'clock position of the shield tail, showing a frustum-like shape. During the shield body grouting process, open a pressure relief hole on the segment behind the shield tail, and control the slurry flow direction to be backward according to the pressure connection principle to avoid the slurry spreading forward and causing the shield machine to be trapped; the shield body grouting is controlled by the method of slow tunneling, and the tunneling speed is controlled at 3-5mm / min to prevent the slurry from coagulating the formation and the shield body. In the present invention, the coagulation time of the injected slurry is short, and the four-way joint is designed with a one-way valve to prevent the slurry from flowing back into the pipeline and coagulating; after the grouting is completed, open the pressure relief valve and quickly clean the pipeline to the clear water state, stop the injection and carry out civilized construction on site.

[0043] (3) After the injection of the double grout is completed, during the shield tunneling process, the attitude of the shield machine is adjusted so that it deviates in the direction of the double grout injection point. During the adjustment process, the frictional force between the shield shell and the formation increases on the injection side of the double grout, thereby increasing the horizontal / vertical partition pressure difference. At the same time, the grout blocks wrapped on the shield body are equivalent to an enlarged excavation section, causing the shield machine to shift towards the grouting position under the action of formation stress, jointly making the attitude approach the target value. During the vertical attitude adjustment process, first measure the three values of the shield tail clearance, cylinder stroke difference, and segment lead. After analysis, the segment is 45 mm ahead at the upper part, and the shield tail clearance is larger at the lower part, with a maximum value of 110 mm. Therefore, increase the pressure components of the upper and lower propulsion cylinders to 80 - 120 bar. During the propulsion process, strengthen the segment selection. Specifically, use the segment selection card for rotation comparison to ensure that the wedge amount forms a favorable trend for the shield tail clearance and segment attitude; increase the measurement frequency of the shield tail clearance to three times, namely when the shield tunnels to one-third length, two-thirds length of the segment width, and after the segment is assembled. Measuring the clearance during the tunneling process is convenient for the control of the current ring tunneling and reference for segment selection. Measuring the clearance after assembly is convenient for analyzing the shield attitude, checking the assembly position, and the control plan for the next ring. Measure the lead of the formed tunnel segments in a timely manner, and at the same time use the automatic lead analysis table for verification to provide a reference basis for segment selection and axis control, ensuring that the lead on the correction side is less than 15 - 25 mm on the theoretical basis. According to the above-mentioned shield tunneling attitude correction situation after shield grout injection, the overall shield thrust increases and the upper and lower pressure differences decrease. This project controls the quality of the formed tunnel and the stability of the shield attitude. The vertical attitude is corrected at a speed of 0.8 - 1.2 mm / m. In this stage, 3 rings are tunneled while maintaining the horizontal attitude from getting continuously worse. The vertical attitude is -2 mm at the front point and 1 mm at the middle end. When the vertical attitude has the ability to maintain stability, due to the need to adjust the shield attitude to the right by 50 mm, it can be divided into 10 rings for correction, with an average of 2.5 mm / m. Double-fluid grout can be injected through the radial holes at the 9 positions of the shield body. The mixing ratio of the double-fluid grout can refer to the grout ratio at the 11 positions mentioned above, and the injection volume is 0.35 - 0.45 cubic meters. The matters needing attention during grouting are the same as those in the vertical attitude adjustment process.

[0044] (4) During the shield attitude adjustment process, in case of emergency according to the deviation correction plan, double grout is injected through the shield advanced grouting holes and radial grouting holes before each ring of shield tunneling and during the tunneling process. The injection volume at each point is controlled at 0.2 - 0.3 m 3 ; The emergency situations in step (4) include: ① The attitude of the shield machine exceeds ±50 mm controlled by the design specification; ② The deviation difference of the shield attitude gradually increases, resulting in the growth rate of the shield machine trend being greater than 1 mm / m; ③ The minimum value of the shield tail clearance is less than 5 mm, and the maximum value of the cylinder stroke difference is greater than 5 cm, seriously affecting segment selection; ④ There are 3 breaks / ring in the quality of the formed tunnel, the maximum value of the offset is greater than 2 cm, and there is 1 leakage / ring.

[0045] (5) After the attitude adjustment of the shield machine is completed, promptly check the excavation of the formation by the shield slurry through the segment grouting holes, and inject a dispersant for dissolution to avoid excessive disturbance of the formation or continuous influence on the shield attitude control. In step (5), the dissolution liquid is injected when the machine is stopped after the shield attitude adjustment is completed. The injection time of the dissolution liquid is controlled at the critical point when the attitude starts to change to 2 mm / m according to the vertical attitude trend control of 0 - 1 mm / m. The dissolution liquid is injected into the advanced grouting holes / radial holes above the position of the double-fluid grouting hole and the adjacent positions. The soaking time is controlled at 8 - 12 h, and then tunneling is resumed. After resuming tunneling, observe the tunneling parameters, including the total thrust, sectional pressure, and attitude changes. At the same time, check the slurry filling situation behind the shield segments. As long as it is consistent with the construction parameters in the normal section, otherwise repeat the above steps for readjustment until the construction state is normal.

[0046] As described above, this is only one embodiment of the present invention, and its description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A method for adjusting the initial attitude of a large-diameter shield tunneling assisted by shield body grouting, characterized in that: The described method is a rectification measure for the phenomenon that the shield machine dips downward and drifts horizontally when the shield machine enters the clay stratum from the solidified soil area during the shield starting process. The specific steps are as follows: (1) During the shield starting process, monitor the tunneling attitude of the shield machine through the shield machine guidance system. When the attitude is abnormal, first inject bentonite with a viscosity greater than 60 s through the shield body radial holes and advanced grouting holes to form a bentonite hoop at the front and middle shield positions for protection; the bentonite is prepared 12 h in advance to make it expand; (2) After the injection of bentonite is completed, inject a double slurry of cement and water glass through the shield body advanced grouting holes and radial grouting holes on the rectification side, and form a bulge on the outside of the shield body at the injection hole position; the injection of the double slurry is carried out by on-site mixing and injection through a grouting machine and a mixing tank. The ratio of cement to water glass in the double slurry is 1:1 to 1:1.3, the setting time is 20 s to 25 s, the injection volume per point is 0.4 m³ to 0.6 m³, and the grouting pressure is within 0.5 bar; (3) After the injection of the double slurry is completed, adjust the attitude of the shield machine during the shield tunneling process to make it deflect in the direction of the double slurry injection point. During the adjustment process, the friction force between the shield body shell and the stratum is increased on the side where the double slurry is injected, thereby increasing the horizontal partition / vertical partition pressure difference. At the same time, the slurry blocks wrapped on the shield body are equivalent to an enlarged excavation section, so that the shield machine deflects towards the grouting position under the action of the stratum stress, jointly making the attitude approach the target value; (4) During the shield attitude adjustment process, when an emergency occurs, inject the double slurry again through the same shield body advanced grouting holes and radial grouting holes as in step (2) before each ring of shield tunneling and during the tunneling process. The injection volume per point is controlled within 0.2 - 0.3 m³; (5) After the shield machine attitude adjustment is completed, check the excavation of the stratum by the shield body slurry through the segment grouting hole in time, and inject a dispersant to dissolve the double slurry injected in steps (2) and (4) to avoid excessive disturbance of the stratum or continuous influence on the shield attitude control.

2. A method for adjusting the initial attitude of a large-diameter shield during shield grouting assistance according to claim 1, characterized in that: In step (1), calculate the difference between the three-dimensional state of the shield machine tested by the shield machine guidance system and the tunnel design axis, and control it according to the horizontal front point, middle point, rear point and vertical front point, middle point, rear point of the shield attitude given in the construction technical disclosure. When the difference is greater than 30 mm, start injecting bentonite.

3. A method for adjusting the initial attitude of a large-diameter shield during shield grouting assistance according to claim 1, characterized in that: The injection process of bentonite in step (1): Connect the bentonite injection pipeline to the shield body radial holes and advanced grouting holes. When the shield attitude is abnormal, continuously inject bentonite into the radial holes and advanced grouting holes along with the tunneling of the shield, injecting while pushing, the pressure is controlled within 0.4 bar, the volume is controlled at 1.5 times the construction building void, and inject and keep the shield tunneling forward continuously for 2 m.

4. A method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting according to claim 1, characterized in that: In step (2), during the injection of the double slurry, inject a friction reducer through the shield body advanced grouting hole or radial grouting hole symmetric to the double slurry injection point. The friction reducer includes one of waste oil, foam agent, bentonite or water.

5. The method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting according to claim 1, characterized in that: In step (2), the grouting points of the double slurry are divided into four areas: upper, lower, left, and right. During grouting, it is injected at the corresponding points in the shield tail according to the requirements of attitude correction. The diffusion range of the slurry does not exceed 45°, and a frustum-shaped slurry block is formed by condensation outside the shield body, which acts on the shield attitude correction through the frictional force with the formation. According to the requirements of shield machine attitude adjustment, the injection volume is increased or decreased by 0.1 - 0.2 m³ each time.

6. A method for adjusting the initial attitude of a large-diameter shield during shield grouting assistance according to claim 1, characterized in that: The grouting process in step (2) includes the following steps: a. Prepare the grouting machine and mixing tank in advance and move them to the operation area; b. Install a ball valve, grouting head, and four-way joint for grouting at the advanced grouting holes and radial grouting holes to be grouted. The four-way joint interfaces are respectively the cement slurry interface, the sodium silicate pipe interface, the pressure relief pipe, and the injection port ball valve, and connect the cement pipe and sodium silicate pipe of the double-fluid grouting machine to the cement slurry interface and sodium silicate pipe interface of the four-way joint through the grouting pipeline; c. Mix the cement in the mixing tank, and at the same time, reserve the corresponding volume in the sodium silicate storage tank according to the scale; d. After preparation, open the pressure relief ball valve, start debugging the grouting pump. After normal debugging, close the pressure relief valve, open the cement slurry pipe ball valve and sodium silicate slurry pipe ball valve, and start grouting.

7. A method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting according to claim 1, characterized in that: The injection of the double slurry in step (2) is carried out by a double-fluid grouting pump and a multi-functional slurry mixing tank; the multi-functional slurry mixing tank includes a cement mixing tank and a sodium silicate storage tank arranged on one side of the cement mixing tank. A scale is provided on the sodium silicate storage tank; a stirring mechanism is provided in the cement mixing tank. A tool cabinet and a cement placement platform are provided on the upper side of the cement mixing tank body. A cement slurry outlet tank is provided at the lower part of the cement mixing tank body. The inlet of the cement slurry outlet tank is communicated with the outlet of the cement mixing tank, and a filter screen is provided at the outlet; slurry outlet ball valves are respectively provided at the bottoms of the sodium silicate storage tank and the cement slurry outlet tank. The sodium silicate storage tank and the cement slurry outlet tank are respectively connected to the double-fluid grouting pump through slurry pipes and are injected simultaneously through the sodium silicate grouting pipe and the cement grouting pipe.

8. A method for adjusting the initial attitude of a large-diameter shield during shield grouting assistance according to claim 4, characterized in that: The emergency situations in step (4) include: ① The shield machine attitude exceeds ±50 mm controlled by the design specification; ② The deviation difference of the shield attitude gradually increases, resulting in a growth rate of the shield machine trend greater than 1 mm / m; ③ The minimum value of the shield tail gap is less than 5 mm, and the maximum value of the cylinder stroke difference is greater than 5 cm, seriously affecting the segment selection; ④ There are 3 quality damages per ring in the formed tunnel, the maximum stagger is greater than 2 cm, and there is 1 leakage per ring.

9. A method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting according to claim 4, characterized in that: The injection time of the dissolving liquid in step (5) is injected when the shield machine attitude is adjusted and then stopped. According to the control of the vertical attitude trend of 0 - 1 mm / m, the injection time of the dissolving liquid is controlled at the critical point when the attitude starts to change to 2 mm / m for the injection of the dissolving liquid; the dissolving liquid is injected into the double-slurry injection hole position and the upper advanced grouting hole / radial hole adjacent to it. The soaking time is controlled at 8 - 12 h, and then tunneling is resumed. After resuming tunneling, observe the tunneling parameters, including the total thrust, sectional pressure, and attitude changes. At the same time, check the slurry filling situation behind the shield segments. If it is consistent with the construction parameters of the normal section, it is okay. Otherwise, repeat the above steps for readjustment until the construction state is normal.

10. A method for adjusting the starting attitude of a large-diameter shield assisted by shield grouting according to claim 4, characterized in that: In the double slurry, the ratio of cement to water glass is 1:1, and the setting time is 20 s. The selected friction reducer is bentonite and water mixed in a ratio of 3:20 by weight, and its viscosity after fermentation for 12 h is 50 - 60 s.

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