Method for passing through reinforced concrete diaphragm wall in shield tunnel by continuous cutting

Abstract

SOLUTION: A method includes steps of: performing MJS cavity filling reinforcement for soil under the floor of an existing station; setting a required cutter head using hob cutter data obtained from an analysis, and setting tunneling parameters of a shield machine cutting in a stratum based on the tunneling parameters of a shield machine cutting in the air; performing secondary grout injection when cutting the diaphragm wall, in addition to synchronous grout injection and secondary grout injection; observing vertical displacement of a station ballast bed, vertical and horizontal displacement of a station side wall, and vertical displacement of a tunnel vault, and adjusting push speed and silo pressure in real time; performing secondary grout injection for segments within 10 rings from a door of a receiving shaft of a newly built station; and injecting grout from grout injection holes of porous segments after the shield machine has passed through.EFFECT: The present invention saves manpower and ensures the safety of an existing station structure above.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of shield tunnel technology, and particularly to a construction method for continuously cutting through a reinforced concrete diaphragm wall in a shield tunnel.

Background Art

[0002] The subway line network intersects. When building a new subway line, it is inevitable to encounter the obstacle of the reinforced concrete diaphragm wall as the protection structure of the existing subway station. To avoid this situation, in the route plan, the reinforced concrete within the range of the shield tunnel section is constructed by replacing it with a preliminary glass fiber rib reinforced wall that is convenient for direct cutting by the shield tunnel. Due to traffic guidance, there are no preliminary requirements when the shield tunnel passes under the existing station. Therefore, the shield tunnel needs to directly cut the reinforced concrete diaphragm wall instead of the glass fiber rib, and the net distance between the shield tunnel and the structure of the existing station is very close, and the safety management requirements for the upper existing structure are strict. Due to the densification of the line network, this situation will become more and more in the future.

[0003] Currently, the conventional method is to reinforce by means such as horizontal freezing or grouting injection, and then manually cut and remove the diaphragm wall. This method is costly, has a long construction period, and high risks. Also, in China, the shield tunneling method of directly cutting the reinforced concrete diaphragm wall is rarely used. Most of them are inventions for passing under existing stations or cutting pile foundation obstacles while tunneling by the shield method. For example, the existing invention patent CN112983441A only solves the safety problems when horizontally penetrating an existing subway line from a monitoring perspective and cannot solve the problem of reinforced concrete obstacles. The cutter head arrangement in invention CN103670428A can smoothly cut bridge piles. CN114991790A and CN112983446A can smoothly cut the pile foundation of a station at a short distance. However, in the case of the protective structure of the diaphragm wall where the volume of reinforced concrete is much larger than the pile foundation, the torque of its cutter head can only be controlled within 60% of the rated output. For the protective structure of the diaphragm wall where the reinforced concrete is much larger than the pile foundation, there are risks such as the cutter head torque being too large, the cutter being overly damaged, and the too-long steel bars clogging the screw. Invention patent CN116771363A provides a cutting method for a single-width reinforced concrete diaphragm wall, but the remaining diaphragm wall still needs to be manually cut off. Its cutter head arrangement cannot continuously cut through the reinforced concrete diaphragm wall, and there are safety risks.

[0004] Therefore, the above problems require urgent solutions.

Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a construction method for continuously cutting through the reinforced concrete diaphragm wall in a shield tunnel, which saves human resources and ensures the safety of the structure of the upper existing station.

[0006] Technical solution: To achieve the above object, the present invention discloses a construction method for continuously cutting through a reinforced concrete diaphragm wall in a shield tunnel. Inject MJS vertical isolation piles between the diaphragm wall of the newly built station and the second diaphragm wall of the existing station, determine the parameters of the horizontal MJS reinforcement construction, and perform MJS cavity filling reinforcement on the soil under the floor of the existing station from the position of the receiving shaft of the newly built station according to the parameters of the horizontal MJS reinforcement construction in step (1). Use finite element simulation software to simulate the numerical values of hob cutters for cutting reinforced concrete, obtain the optimal cutter spacing and optimal penetration of the hob cutters, and arrange the required cutter heads using the hob cutter data obtained from the analysis in step (2). Using the arranged cutter heads, conduct a cutting test of reinforced concrete by a shield machine in the air, obtain the tunneling parameters of the shield machine when cutting in the air, determine the ratio of the torque of the shield machine when cutting in the air to the rated output of the shield machine respectively, and set the tunneling parameters of the shield machine during stratum cutting according to the tunneling parameters of the shield machine when cutting in the air, and control the maximum total thrust and torque within 30% of the rated output in step (3). The shield machine performs synchronous grout injection during stratum excavation. During excavation, secondary grout injection is carried out at the upper position of the first ring segment or at the position with voids. Before the shield cutter head reaches the first diaphragm wall, secondary grout injection construction is carried out on the 5th to 7th rings behind the shield tunnel, that is, secondary grout injection is carried out on all segments within the first ring. The segments during the process of passing under the existing station adopt porous segments with ultra-deep grout injection holes buried deeply. When the cutter head of the shield machine reaches the second diaphragm wall, secondary grout injection construction is carried out on the segments of the 8th to 10th rings behind the shield tail in step (4). During the process of the shield machine cutting through an existing station, observe the vertical displacement of the ballast bed of the station, the vertical and horizontal displacements of the side wall of the station, and the vertical displacement of the tunnel vault, and feedback the data obtained from the observation to the shield unit. By adjusting the pushing speed and silo pressure in real time, maintain the vertical displacement of the ballast bed of the existing station, the vertical and horizontal displacements of the side wall of the station, and the vertical displacement of the tunnel vault within the set values (step 5); The shield machine performs secondary grouting injection on the segments within a 10-ring range from the door of the receiving shaft of the newly built station. After the construction is completed, the residual soil in the soil silo is emptied and the earth pressure drops to the normal pressure (step 6); After the shield machine has passed through, perform deep-hole grouting injection within 2 - 3 m from the periphery of the deep grouting holes provided in the porous segments that have passed through within the range of the existing station (step 7).

[0007] Here, in the above step (1), the horizontal MJS reinforcement construction parameters include the water-cement ratio of the cement slurry, the pressure of the cement slurry, the flow rate of the cement slurry, the main air pressure, the main air flow rate, the cement slurry additive, the water suction pressure, the pulling speed, the stepping time, the rotation speed, the ratio of the in-situ pressure coefficient to the in-situ pressure, the predicted cement mixing amount, the slurry flow rate, and the shaft deviation.

[0008] Preferably, in the above step (2), the specific simulation method for obtaining the optimal cutter spacing and the optimal penetration depth of the hob cutter by simulation is as follows.

[0009] (2.1) Establish a finite element analysis model of two hob cutters and reinforced concrete, and perform meshing on the finite element analysis model.

[0010] (2.2) Assign material properties to the concrete, steel bars, and hob cutters.

[0011] (2.3) Set the cutter interval and the penetration depth as independent variables, and simulate the ability of the hob cutter to cut reinforced concrete using the equivalent concrete stress distribution, the rolling force of the cutter, and the vertical force as indicators. Thus, obtain the optimal cutter interval and the optimal penetration depth. Here, when the rolling force and the vertical force of the hob cutter are less than the set values, both the ratio of the peak value to the average value of the rolling force of the hob cutter and the ratio of the peak value to the average value of the vertical force of the hob cutter are less than the set values. When selecting the optimal stress range for the equivalent concrete stress distribution, the hob cutter interval and the hob cutter penetration force are optimal.

[0012] Also, in step (2), the cutter head has a composite cutter head structure of 4 main beams + 4 secondary beams. The composite cutter head structure is equipped with 29 front hob cutters, 13 edge hob cutters, 40 front scrapers, 8 edge scrapers, 6 foam nozzles, and 2 bentonite nozzles along the Archimedes spiral. Here, 21 front hob cutters are installed on one side, and 8 front hob cutters are symmetrically arranged to form 4 center duplex disk hob cutters. The opening rate of the cutter head is 40%. Adopt 6 independent foam nozzles, of which 2 foam nozzles may be used as bentonite nozzles. By welding wear-resistant layers on the surfaces of the blades and the spiral shafts, the voids are shortened to 6 mm.

[0013] Furthermore, in step (3), when the shield machine cuts in the air, the tunneling parameters of the shield machine are set as follows: when the push speed is 2 - 4 mm / min and the rotation speed is 0.6 - 1.0 rpm, the maximum total thrust of the shield tunnel is 4493.8 kN, the maximum torque of the shield tunnel is 1155.8 kN·m. The maximum total thrust of the shield tunnel accounts for 10.3% of the rated output of the shield machine, and the maximum torque of the shield tunnel accounts for 15.2% of the rated output of the shield machine.

[0014] Preferably, in step (3), the tunneling parameters during the stratum cutting of the shield machine are specifically as follows: When the shield machine is within 5 cm from the first diaphragm wall, start the shield machine, control the pushing speed within the range of 2 - 4 mm / min, set the rotation speed to 0.8 - 1.0 rpm. When the shield machine is in the stratum, control the thrust to 10000 - 13000 kN, control the torque to 800 - 1000 kN·m, and control its maximum thrust and torque within 30% of the rated output. The deviation correction amount per time ≤ 2 mm, the total amount of each ring ≤ 5 mm. When the shield machine cuts the wall body, control the opening rate of the gate to stabilize it, keep the silo pressure at 1.6 bar - 1.8 bar, and control the torque of the screw to 40 - 50 kN·m.

[0015] Also, in step (4), the construction of the secondary grouting injection is specifically as follows: The start time of the grouting injection can be to inject grout after the segment has escaped from 5 rings behind the shield tail. The grouting holes of each ring are injected alternately, and the injection amount of each hole is 0.5 - 1 m 3 / hole, control the slurry flow rate to 10 - 15 L / min, and arrange the grouting injection pressure to be 0.3 MPa - 0.4 MPa.

[0016] Furthermore, in step (4), when the shield cutter head passes through the second diaphragm wall and reaches the MJS vertical isolation pile, cut and remove a certain thickness of reinforced concrete of the third diaphragm wall from the position of the receiving shaft of the newly built station. Then, attach a steel sleeve to the door of the receiving shaft of the newly built station, and backfill the residual soil inside so that the shield machine can enter the steel sleeve.

[0017] Preferably, in step (6), the construction of the secondary grouting injection is specifically as follows: It is necessary to inject grout into each hole of each ring to plug it. Control the grouting injection pressure of each hole to 0.2 - 0.4 mPa, and the grouting injection amount of each hole to 0.5 - 1 m 3It is arranged to be plugged with grout injection immediately after making a hole and completing the construction of one ring.

[0018] Also, in step (7), for deep-hole grout injection, specifically, internally, water glass diluted 1:3 with water and cement slurry with a water-to-cement ratio of 1:1 are adopted, the deep-hole grout injection rate is set at 20% - 30%, and during the grout injection process, for 10 rings before and after the grout injection position in the tunnel, in-tunnel settlement and convergence measurements are carried out in real time. The measurement index is that the change amount of one-time in-tunnel settlement and convergence is within ±1 mm. Otherwise, the grout injection is stopped and the grout injection pressure is arranged to be below 50 kPa of the earth pressure of the corresponding stratum.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages.

[0020] (1) In the present invention, in order for the cutter head to smoothly cut a large amount of reinforced concrete, cutter simulation is used to determine the optimal cutter spacing and the optimal penetration degree, and then the cutter head is arranged. Using the arranged cutter head, a test is carried out on the shield machine to cut reinforced concrete in the air. Therefore, the tunneling parameters of the shield machine in the stratum are determined, avoiding the risk of excessive load on the cutter head and serious damage to the cutter head tools, and greatly reducing human and material resources.

[0021] (2) Before the shield tunnel penetrates downward, the present invention mainly uses the MJS reinforcement technology. The reinforcement technology itself causes little disturbance to the stratum and the upper structure, and both the reinforcement strength and the range can meet the reinforcement requirements. This provides a good stratum environment before cutting through the diaphragm wall by the shield tunnel, reduces the response of the upper station structure when the shield tunnel passes through, and at the same time provides sufficient reaction force when cutting and passing through by the tunnel.

[0022] (3) The present invention uses the arrangement of a full hob spoke type composite cutter head, which can completely cover and cut the concrete wall surface, effectively cut the reinforcing bars. By changing the distance between the screw blade and the cylindrical wall, it can effectively prevent the reinforced concrete from clogging the screw, ensuring the safety of the shield tunnel construction and the progress of the construction period.

[0023] (4) The present invention can effectively control the load of the cutter head during cutting by a shield tunnel by reasonably selecting the tunneling parameters of the shield tunnel, avoiding the risk of cutter head clogging and excessive disturbance caused by the load of the cutter head on the structure of the upper station.

[0024] (5) In the present invention, in addition to synchronous grout injection and secondary grout injection, when the shield cutter head reaches in front of the first diaphragm wall, or reaches the second diaphragm wall, and when it is close to the door of the receiving shaft of the newly built station, secondary grout injection construction is carried out on the segments to reduce the settlement in the shield tunnel construction.

[0025] (6) After the shield machine passes through, deep hole grout injection is carried out around the holes of the ultra-deep grout injection holes provided in the porous segments to further ensure the safety of the tunnel structure and the stability of the upper structure.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying out the Invention

[0027] Next, the technical solution of the present invention will be further described with reference to the drawings.

[0028] As shown in FIG. 1, the method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel of the present invention includes the following steps.

[0029] (1) As shown in FIG. 5, inject the MJS vertical isolation pile between the diaphragm wall of the newly built station and the second diaphragm wall of the existing station, determine the parameters of the horizontal MJS reinforcement construction, and perform MJS cavity filling reinforcement on the soil under the floor of the existing station from the position of the receiving shaft of the newly built station according to the parameters of the horizontal MJS reinforcement construction. The parameters of the horizontal MJS reinforcement construction include the water-cement ratio of the cement slurry, the pressure of the cement slurry, the flow rate of the cement slurry, the main air pressure, the main air flow rate, the cement slurry additive, the water suction pressure, the pulling speed, the stepping time, the rotation speed, the ratio of the in-situ pressure coefficient to the in-situ pressure, the predicted cement mixing amount, the slurry flow rate and the shaft deviation. Before the shield tunnel penetrates downward, mainly use the MJS reinforcement technology. The reinforcement technology itself causes little disturbance to the formation and the superstructure, and both the reinforcement strength and the range can meet the reinforcement requirements. This provides a good formation environment before cutting through the diaphragm wall by the shield tunnel, reduces the response of the upper station structure when the shield tunnel passes through, and at the same time provides sufficient reaction force when cutting and passing through by the tunnel.

[0030] For the silty clay layer and silty sand layer of the soft soil layer with abundant water, large-scale in-situ tests and laboratory experiments were carried out to obtain the influence of various construction parameters on formation disturbance and pile strength. The results show that the minimum strength of the pile is 3 mPa, the permeability coefficient is less than E-7 cm / s, and the change amount of the soil disturbance structure and the change amount of the horizontal displacement are all less than 5 mm. As shown in Table 1, the parameters of the horizontal MJS reinforcement construction for the soft formation with abundant water were determined. As shown in Figure 2, vertical MJS isolation piles were installed between the diaphragm wall of the newly built station (the third diaphragm wall) and the second diaphragm wall of the existing station to reduce the disturbance caused by the horizontal MJS construction transmitted to the structure and provide a uniform force transmission path for the subsequent shield tunnel to pass through. Then, from the position of the receiving shaft of the newly built station, MJS cavity filling reinforcement was carried out under the floor of the existing station, and the parameters of the MJS reinforcement construction were carried out according to the recommended values in Table 1.

[0031]

Table 1

[0032] (2) Using finite element simulation software, the numerical values of the hob cutters for cutting reinforced concrete were simulated to obtain the optimal cutter spacing and the optimal penetration degree of the hob cutters. The necessary cutter heads were arranged using the data of the hob cutters obtained from the analysis.

[0033] As shown in Fig. 3, through the cutting test of the reinforced concrete wall in a large-scale shield tunnel site, the cutter head has a composite cutter head structure of 4 main beams + 4 secondary beams. The diameter of the cutter head is 6.84 m. In the composite cutter head structure, 29 front hob cutters, 13 edge hob cutters, 40 front scrapers, 8 edge scrapers, 6 foam nozzles, and 2 bentonite nozzles are equipped along the Archimedes spiral, and all of them are 18 inches in size and are used for cutting reinforced concrete. Here, 21 front hob cutters are installed on one side, and 8 front hob cutters are symmetrically arranged to form 4 center duplex disk hob cutters. Furthermore, 40 scrapers and 8 edge scrapers for assisting in cutting residual slag are arranged. The hob cutter is 187.7 mm higher than the panel, and the scraper is 135 mm higher than the panel. With the optimized design, the opening rate of the cutter head reaches 40%, which can enhance the sludge fluidity in the cutter head. 6 independent foam nozzles are adopted, and among them, 2 foam nozzles may be used as bentonite nozzles. Each nozzle is designed with a single tube and a single pump to avoid the risk of sludge solidification on the cutter head. When cutting the diaphragm wall, by injecting foam, the risk of excessive torque of the cutter head can be reduced, and by injecting bentonite into the shield shell, the frictional resistance of the shield shell can be reduced, thus playing a role in reducing the thrust. Optimize the gap between the spiral shaft and the cylinder segment, and weld a wear-resistant layer on the surface of the blade and the spiral shaft to shorten the gap to 6 mm. Finally, arrange 5 inspection windows around the body of the screw conveyor. In the present invention, the arrangement of the full hob spoke type composite cutter head is used, which can completely cover and cut the concrete wall surface, effectively cut the steel bars, and by changing the distance between the screw blade and the cylindrical wall, effectively prevent the reinforced concrete from clogging the screw.

[0034] Through tests, it is found that the cutter head and the cutter can cut through the entire cross-section of reinforced concrete. Among them, 95% of the concrete blocks have a particle size within 10 cm, and 70% of the broken steel bars have a length within 70 cm. The wear of the cutter is very small, all within 1 mm, and the vibration of the cutter head against the wall is less than 0.15 g. The specific settings of the cutter head are shown in Table 2.

[0035]

Table 2

[0036] As shown in Figure 4, by optimizing the gap between the spiral shaft and the cylinder segment and welding a wear-resistant layer on the surface of the blade and the spiral shaft, the gap can be shortened to 6 mm, the risk of clogging can be reduced, and the damage to the blade when the steel bar passes through the screw can be reduced. Finally, five inspection windows are installed around the body of the screw conveyor to prevent manual handling when the spiral shaft is clogged and cannot be pulled out.

[0037] As shown in Figure 2, the specific hob cutter simulation method is as follows.

[0038] (2.1) Establish a finite element analysis model of two hob cutters and reinforced concrete, and mesh the finite element analysis model.

[0039] (2.2) Assign material properties to the concrete, steel bars and hob cutters.

[0040] (2.3) Set the cutter interval and the penetration depth as independent variables, and simulate the ability of the hob cutter to cut reinforced concrete using the equivalent concrete stress distribution, the rolling force of the cutter, and the vertical force as indicators. Thus, obtain the optimal cutter interval and the optimal penetration depth. Here, when the rolling force and the vertical force of the hob cutter are less than the set values, the ratios of the peak value to the average value of the rolling force of the hob cutter and the ratio of the peak value to the average value of the vertical force of the hob cutter are both less than the set values. When the equivalent concrete stress distribution selects the optimal stress range, the hob cutter interval and the hob cutter penetration force are optimal. The equivalent concrete stress between the two cutters within the interval range is greater than 30 MPa, and the ridge of the concrete can be avoided. For an 18-inch hob cutter, when the cutting depth is 2 - 5 mm and the cutter interval is 80 - 100 mm, there exists an optimal cutter interval for the hob cutter to effectively break reinforced concrete with the highest efficiency.

[0041] (3) Using the arranged cutter head, conduct a cutting test of reinforced concrete in the air by a shield machine to obtain the tunneling parameters of the shield machine when cutting in the air. Through the test, when the push speed is set to 2 - 4 mm / min and the rotation speed is set to 0.6 - 1.0 rpm, the maximum total thrust and torque of the shield tunnel are 4493.8 kN and 1155.8 kN·m respectively, accounting for 10.3% and 15.2% of the rated output of the shield machine respectively. The load on the shield machine is small, which indicates that the shield machine can ensure smooth cutting through the reinforced concrete diaphragm wall.

[0042] According to the tunneling parameters of the shield machine for cutting in the air, set the tunneling parameters of the shield machine for cutting in the stratum. Specifically, when it is about 5 cm from the first diaphragm wall, based on the tunneling parameters of "stabilizing the load, controlling the posture, and ensuring the earth pressure", that is, when it is within 5 cm from the first diaphragm wall, start the shield machine. To enable the cutter head to effectively grind the steel bars, start the low-speed push mode of the shield tunnel technology, control the push speed within the range of 2 - 4 mm / min, set the rotation speed to 0.8 - 1.0 rpm. When the shield machine is in the stratum, control the thrust to 10000 - 13000 kN, control the torque to 800 - 1000 kN·m, and control the thrust and torque within 30% of the rated output. Pay attention to the phenomenon of emergency correction, especially vertical correction, and terminate it. The deviation correction amount per time ≤ 2 mm, the total amount per ring ≤ 5 mm. When the shield machine cuts the wall body, manually control and stabilize the opening rate of the gate, increase the amount of soil received, assist in discharging the steel bars, maintain the silo pressure at 1.6 bar - 1.8 bar, control the torque of the screw to 40 - 50 kN·m. When the torque is too large, the blockage can be avoided by reversing the screw. The present invention reasonably selects the tunneling parameters of the shield tunnel, effectively controls the load of the cutter head during the cutting period of the shield tunnel, and avoids the risks of cutter head blockage and excessive disturbance of the load of the cutter head on the structure of the upper station.

[0043] (4) While the shield machine performs synchronous grout injection during stratum excavation, at the same time, secondary grout injection is carried out at the upper position of the first ring segment or the position with voids. Here, synchronous grout injection means that when excavating the shield tunnel, slurry is injected outside the shield while excavating, and the voids behind the shield tail are firmly filled in a very short time. Therefore, the surrounding rock mass can be supported in a timely manner. Secondary grout injection means that when supporting the segment, grout injection is carried out on the segment to further fill the waterproof layer firmly and achieve the purpose of strengthening the tunnel lining. It is necessary to inject only at the upper position of the first ring segment or the position with voids.

[0044] As shown in Fig. 6, before the shield cutter head reaches the first diaphragm wall, the secondary grouting construction is carried out for 5 to 7 rings behind the shield tunnel, that is, the secondary grouting is carried out for all segments in the first ring. The start time of the grouting can be carried out after the segment has escaped from the shield tail for 5 rings. The grouting holes of each ring are alternately grouted, and the injection volume of each hole is 0.5 to 1 m 3 / hole, which is controlled according to the serious situation of surface settlement and tunnel leakage. In addition, in order to make the slurry penetrate more uniformly along the outer wall of the segment, the slurry flow rate is controlled at 10 to 15 L / min, so that it is possible to avoid dividing the soil to form a block-shaped reinforcement area. The grouting pressure needs to be determined after comprehensively considering the foundation conditions, segment strength, slurry performance, and earth pressure. The general grouting pressure is 0.3 MPa to 0.4 MPa. During the process of passing under the existing station, the segment adopts a porous segment with ultra-deep grouting holes buried deeply. The grouting holes are selected according to the principle of left-right symmetry from bottom to top, which is helpful for the subsequent implementation of deep-hole grouting.

[0045] When the cutter head of the shield machine reaches the second diaphragm wall, secondary grouting is carried out on the 8 - 10 ring segments behind the shield tail. The tunneling parameters are optimized in real time according to the propulsion parameters of the first diaphragm wall section. When the shield cutter head reaches the MJS vertical isolation pile, about 500 mm thick reinforced concrete of the third diaphragm wall is cut and removed from the position of the receiving shaft of the newly built station. Then, a steel sleeve is installed on the door of the receiving shaft of the newly built station, and backfilling of soil is carried out inside so that the shield machine can enter the steel sleeve. In addition to the conventional synchronous grouting and secondary grouting replenishment, the present invention performs grouting for the secondary grouting construction on the segments behind the shield tail before cutting the wall to block it, reducing the settlement during shield tunnel construction. After the cutting is completed, the steel sleeve is used to avoid the risk that the excavation surface becomes unstable during the acceptance of the shield machine, causing soil and groundwater to flow into the receiving shaft.

[0046] (5) During the period when the shield machine cuts through the existing station, a combination of manual monitoring and automatic monitoring is adopted. The vertical displacement of the ballast bed of the station, the vertical and horizontal displacements of the side wall of the station, and the vertical displacement of the tunnel vault are observed. Considering comprehensively the monitoring requirements of relevant specifications and combining the monitoring objects of this project, the layout of the monitoring points is optimized. During the period when the shield tunnel cuts through the existing station, the observed data is fed back to the shield unit in real time through the ground command side, and the push speed and silo pressure are adjusted in real time to avoid the risk that the disturbance in the superstructure is too large. The vertical displacement of the ballast bed of the existing station, the vertical and horizontal displacements of the side wall of the station, and the vertical displacement of the tunnel vault are all maintained within 4 mm. In the present invention, monitoring is carried out during the period of passing under the station, and the data is fed back to the ground command side in real time so that measures in the construction of the shield tunnel can be taken in real time, and the construction of the shield tunnel can be guided.

[0047] (6) The shield machine shall conduct the secondary grouting construction for the segments within the range of 10 rings from the door of the receiving shaft of the newly built station. Each hole in each ring shall be plugged with secondary grouting, and the grouting pressure of each hole shall be controlled at 0.2 - 0.4 mPa, and the grouting volume of each hole shall be 0.5 - 1 m 3 / hole. After the construction of one ring is completed, it shall be plugged with grouting immediately. After the completion of the secondary grouting construction, the soil in the soil silo shall be emptied, and the earth pressure shall drop to the normal pressure. Also, attention shall be paid to the sealing performance of the steel sleeve when the cutter head is pushed out from the reinforcement. When there is water leakage when the cutter head of the shield machine is pushed out from the reinforcement, polyurethane shall be injected using the emergency grouting hole on the ground to prevent the occurrence of water leakage phenomenon in the channel.

[0048] After the shield machine has passed through, for the porous segments that have passed through within the existing station area, deep-hole grouting is carried out within 2 - 3 m from the hole circumference of the deeply buried ultra-deep grouting holes provided in the porous segments. As shown in Figure 7, internally, water glass diluted 1:3 with water and a cement slurry with a water-to-cement ratio of 1:1 are adopted. The deep-hole grouting rate is set at 20% - 30%. During the grouting process, for the 10 rings before and after the grouting position of the tunnel, settlement and convergence measurements inside the tunnel are carried out in real time. The measurement frequency is 30 min / time. The measurement index is that the change amount of one-time settlement and convergence inside the tunnel is ±1 mm or less. Otherwise, stop the grouting, and the grouting pressure is set at 50 kPa or less of the earth pressure of the corresponding formation. When reinforcing by grouting, follow the injection principle of "uniformity, small quantity, multiple times, multiple injection points". In the present invention, after the shield tunnel has passed through, for the segments passing through within the existing Line 1 area, deep-hole grouting is carried out within 3 m from the hole circumference of the deeply buried ultra-deep grouting holes in the segments to further ensure the safety of the tunnel structure and the stability of the upper structure. The present invention uses the cutter head arrangement of the present invention during the double-line construction of the shield tunnel. During the construction period, no clogging phenomenon appears in the spiral excavator, and all settlements of the station structure are within 4 mm. After the construction is completed, there are only a few steel bars entangled around the cutter head, and no obvious phenomenon of sludge hardening appears. The maximum wear of the hob cutter is within 5 mm. The shield tunnel has smoothly completed the task of continuously cutting four reinforced concrete diaphragm walls underground.

Claims

Claim 1 Inject the MJS vertical isolation piles between the diaphragm wall of the newly built station and the second diaphragm wall of the existing station, determine the parameters of the horizontal MJS reinforcement construction, and perform MJS cavity filling reinforcement on the soil under the floor of the existing station from the position of the receiving shaft of the newly built station according to the parameters of the horizontal MJS reinforcement construction (Step 1); Use finite element simulation software to simulate the numerical values of the hob cutters for cutting reinforced concrete, obtain the optimal cutter spacing and optimal penetration of the hob cutters, and arrange the required cutter heads using the hob cutter data obtained from the analysis (Step 2); Use the arranged cutter heads to conduct a cutting test of reinforced concrete in the air by a shield machine, obtain the tunneling parameters of the shield machine when cutting in the air, determine the ratio of the torque of the shield machine when cutting in the air to the rated output of the shield machine respectively, set the tunneling parameters of the shield machine during stratum cutting according to the tunneling parameters of the shield machine when cutting in the air, and control the maximum total thrust and torque within 30% of the rated output (Step 3); During the stratum excavation, the shield machine performs synchronous grouting, and during excavation, secondary grouting injection is carried out at the upper position of the first ring segment or the position with voids. Before the shield cutter head reaches the first diaphragm wall, secondary grouting injection construction is carried out on the 5 - 7 rings behind the shield tunnel, that is, secondary grouting injection is carried out on all segments within the first ring. The segments during the process of passing under the existing station adopt porous segments with ultra - deep grouting holes buried deeply. When the cutter head of the shield machine reaches the second diaphragm wall, secondary grouting injection construction is carried out on the segments of 8 - 10 rings behind the shield tail (Step 4); During the process of the shield machine cutting through an existing station, observe the vertical displacement of the ballast bed of the station, the vertical and horizontal displacements of the side walls of the station, and the vertical displacement of the tunnel vault, and feedback the observed data to the shield unit. By adjusting the push speed and silo pressure in real time, maintain the vertical displacement of the ballast bed, the vertical and horizontal displacements of the side walls of the station, and the vertical displacement of the tunnel vault within the set values (step 5); The shield machine performs secondary grouting injection on the segments within a 10-ring range from the door of the receiving shaft of the newly built station. After the construction is completed, the soil in the soil silo is discharged empty and the earth pressure drops to the normal pressure (step 6); After the shield machine has passed through, perform deep-hole grouting injection within 2 - 3 m from the periphery of the deep-buried ultra-deep grouting holes provided in the porous segments that have passed through within the range of the existing station. The method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel is characterized by including this step (7).

2. The parameters of the horizontal MJS reinforcement construction in step (1) include the water-cement ratio of the cement slurry, the pressure of the cement slurry, the flow rate of the cement slurry, the main air pressure, the main air flow rate, the cement slurry additive, the water suction pressure, the pulling speed, the stepping time, the rotation speed, the ratio of the in-situ pressure coefficient to the in-situ pressure, the predicted cement mixing amount, the slurry flow rate, and the shaft deviation. The method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel according to claim 1 is characterized by this.

3. In step (2), the specific simulation method for obtaining the optimal cutter spacing and the optimal penetration depth of the hob cutter through simulation is as follows: (2.1) Establish a finite element analysis model of two hob cutters and reinforced concrete, and perform meshing on the finite element analysis model; (2.2) Assign material properties to the concrete, steel bars, and hob cutters; (2.3) Set the cutter interval and the penetration depth as independent variables, and simulate the ability of the hob cutter to cut reinforced concrete using the equivalent concrete stress distribution, the rolling force of the cutter, and the vertical force as indicators. Thus, obtain the optimal cutter interval and the optimal penetration depth. Here, when the rolling force and the vertical force of the hob cutter are less than the set values, the ratio of the peak value to the average value of the rolling force of the hob cutter and the ratio of the peak value to the average value of the vertical force of the hob cutter are both less than the set values. When selecting the optimal stress range for the equivalent concrete stress distribution, the cutter interval and the cutter penetration force of the hob cutter are optimal. A method for continuously cutting through a reinforced concrete underground continuous wall in a shield tunnel according to claim 1, characterized by including the above.

4. The cutter head in the step (2) has a composite cutter head structure of 4 main beams + 4 secondary beams. The composite cutter head structure is equipped with 29 front hob cutters, 13 edge hob cutters, 40 front scrapers, 8 edge scrapers, 6 foam nozzles, and 2 bentonite nozzles along the Archimedes spiral. Here, 21 front hob cutters are installed on one side, and 8 front hob cutters are symmetrically arranged to form 4 center duplex disk hob cutters. The opening rate of the cutter head is 40%. 6 independent foam nozzles are adopted, and among them, 2 foam nozzles may be used as bentonite nozzles. By welding wear-resistant layers on the surface of the blade and the spiral shaft, the void is shortened to 6 mm. A method for continuously cutting through a reinforced concrete underground continuous wall in a shield tunnel according to claim 3, characterized by the above.

5. The tunneling parameters of the shield machine when cutting in the air in step (3) are as follows: when the pushing speed is set to 2 - 4 mm / min and the rotation speed is set to 0.6 - 1.0 rpm, the maximum total thrust of the shield tunnel is 4493.8 kN, the maximum torque of the shield tunnel is 1155.8 kN·m. The maximum total thrust of the shield tunnel accounts for 10.3% of the rated output of the shield machine, and the maximum torque of the shield tunnel accounts for 15.2% of the rated output of the shield machine. A method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel according to claim 1, characterized in that.

6. In step (3), the tunneling parameters when the shield machine cuts the formation are specifically as follows: when it is within 5 cm from the first diaphragm wall, start the shield machine, control the pushing speed within the range of 2 - 4 mm / min, set the rotation speed to 0.8 - 1.0 rpm. When the shield machine is in the formation, control the thrust to 10000 - 13000 kN, control the torque to 800 - 1000 kN·m, control its maximum thrust and torque within 30% of the rated output, the deviation correction amount per time ≤ 2 mm, the total amount of each ring ≤ 5 mm. When the shield machine cuts the wall body, control the opening rate of the gate to make it stable, keep the silo pressure at 1.6 bar - 1.8 bar, and control the torque of the screw to 40 - 50 kN·m. A method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel according to claim 5, characterized in that.

7. The construction of the secondary grout injection in the step (4) is specifically as follows: the grout injection start time can be to inject grout after the segment has escaped from the 5 rings of the shield tail, and the grout injection holes of each ring are injected alternately, and the injection volume of each hole is 0.5 to 1 m ３ / hole, the slurry flow rate is controlled to 10 to 15 L / min, and the grout injection pressure is arranged to be 0.3 MPa to 0.4 MPa. A method for continuously cutting through a reinforced concrete underground continuous wall in a shield tunnel according to claim 1.

8. In step (4), when the shield cutter head passes through the second diaphragm wall and reaches the MJS vertical isolation pile, cut and remove the reinforced concrete with a certain thickness of the third diaphragm wall from the position of the receiving shaft of the newly built station. Then, attach a steel sleeve to the door of the receiving shaft of the newly built station, and backfill the soil inside so that the shield machine can enter the steel sleeve. A method for continuously cutting through the reinforced concrete diaphragm wall in the shield tunnel according to claim 1, characterized in that.

9. In the step (6), for the construction of the secondary grout injection, specifically, it is necessary to perform grout injection for each hole of each ring, control the grout injection pressure of each hole to 0.2 to 0.4 mPa, and control the grout injection volume of each hole to 0.5 to 1 m ３ / hole, and it is arranged to be blocked by grout injection immediately after the construction of one ring is completed. A method for continuously cutting through a reinforced concrete diaphragm wall in a shield tunnel according to claim 1.

10. In the step (7), for the deep-hole grout injection, specifically, internally, water glass diluted with water at a ratio of 1:3 and cement slurry with a water-to-cement ratio of 1:1 are adopted, the deep-hole grout injection rate is set at 20% to 30%, and during the grout injection process, for the 10 rings before and after the grout injection position of the tunnel, the settlement and convergence in the tunnel are measured in real time. The measurement index is that the change amount of one-time settlement and convergence in the tunnel is within ±1 mm. Otherwise, the grout injection is stopped, and the grout injection pressure is arranged to be 50 kPa or less than the earth pressure of the corresponding stratum. A construction method for continuously cutting through the reinforced concrete diaphragm wall in a shield tunnel according to claim 1.

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