A method for rectifying torsion of a rectangular top pipe tunnel

Abstract

The application discloses a torsion rectifying method for a rectangular top pipe tunnel, which comprises the following steps: S1, measuring the torsion angle alpha of the tunnel; S2, determining the model of a pipe jacking machine and the pipe jacking machine tunneling route; S3, according to the tunneling route, the soil body hindering the tunnel rotation is cleaned; S4, after the pipe jacking machine tunnels to the receiving well ground wall, the pipe is retreated, and during the pipe retreating process, the post-retreating grouting slurry is injected to be filled; S5, the mixed slurry is used to seal the starting well portal; S6, the unbalanced grouting is carried out on the periphery of the rectangular tunnel, after the torsion force generated by the grouting reaction force of the unbalanced grouting pushes the tunnel to rotate to the design posture, the balanced grouting is used and the pressure is maintained; S7, after the tunnel is rectified, the double-liquid slurry is used to replace the post-retreating grouting slurry and the unbalanced grouting slurry. The formed tunnel after the torsion can be completely rectified, the normal function of the tunnel is not affected due to the tunnel torsion, the stability of the soil body above the tunnel during the construction can be ensured, and the construction safety is ensured.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a method for correcting torsion in a rectangular pipe jacking tunnel. Background Technology

[0002] Pipe jacking technology is a non-excavation pipeline laying construction technology used in various fields. Compared with the open-cut method, it has attracted much attention for scientifically solving the problems of damaging existing surface structures and causing traffic congestion during pipeline laying or tunnel construction. It also has advantages in environmental protection, such as minimal or no impact on the surrounding environment, small construction site, and low noise.

[0003] Pipe jacking can be classified into circular pipe jacking and irregular-shaped pipe jacking based on its cross-sectional shape, with rectangular pipe jacking being the most widely used irregular-shaped pipe jacking. Rectangular pipe jacking technology is frequently used in underground spaces and rail transit. It was first applied to the Tokyo Underground Connector in the early 1970s. In 1995, the first domestically developed rectangular pipe jacking machine (2.5m x 2.5m cross-section) was deployed and applied to the pedestrian access tunnels of Shanghai Metro Lines 2 and 5. Later, with the maturation of soil improvement technology, rectangular pipe jacking technology became applicable to various non-rock strata. However, during rectangular pipe jacking operations, due to the complexity of the strata and changes in ground overload, the soil within the jacking area is prone to uneven hardness. Under the cutting action of the cutterhead, the pipe jacking machine will experience torsional force, causing twisting of the machine and the subsequent jacking tunnel. This is usually addressed during excavation by changing the direction of the cutterhead rotation or by applying weight to one side of the machine to generate a rotational torque, such as... Figure 1 As shown, under the action of torque, the tunnel boring machine head may begin to slowly rotate. However, in most rectangular pipe jacking tunnels, after twisting, it cannot effectively cut the soil at the designed cross-section, resulting in the inability to rotate or the remaining jacking distance not being able to fully rotate. This causes the formed tunnel to exhibit a certain degree of twisting angle, such as... Figure 2 As shown, this has caused significant quality problems and even affected the normal functioning of the tunnel. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for correcting the torsion of a rectangular pipe jacking tunnel. This method is applicable to correcting the torsion of a formed tunnel. It involves clearing the soil that obstructs the rotation of the formed tunnel using a small circular pipe jacking, and then providing rotation torque through uneven grouting to drive the tunnel to rotate slowly. After the tunnel is straightened, a double grout is used to solidify the voids around the tunnel to prevent further torsion and settlement.

[0005] This invention is achieved through the following technical solution:

[0006] A method for correcting torsion in a rectangular pipe jacking tunnel includes the following steps:

[0007] S1. Measurement: The torsion angle α of the tunnel is obtained by measuring the posture of the formed tunnel;

[0008] S2. Determine the pipe jacking machine model and tunneling route: Determine the range of soil around the tunnel that hinders the tunnel's rotation based on the tunnel's torsion angle α, and select a suitable circular pipe jacking machine and tunneling route based on the range and type of soil that hinders the tunnel's rotation.

[0009] S3. Pipe jacking excavation: Based on the selected circular pipe jacking machine and excavation route, the soil that hinders the tunnel rotation is excavated and cleared;

[0010] S4. Pipe Removal and Filling: After the circular pipe jacking machine has advanced to the diaphragm wall of the receiving well, appropriate pipe removal technology is used for pipe removal. During the pipe removal process, back-removal grout is injected for filling, and the back-removal grouting pressure is ensured to be greater than the static water and soil pressure to ensure complete filling.

[0011] S5. Tunnel Portal Sealing: The tunnel portal of the launching shaft is sealed with a mixed grout. When the circular pipe jacking machine retracts to the position of the launching shaft portal, it stops retracting, allowing the pipe jacking machine to block the portal. After the mixed grout solidifies, the pipe jacking machine is withdrawn. After the pipe jacking machine is completely withdrawn, the portal is sealed with quick-setting cement.

[0012] S6. Tunnel straightening: Unbalanced grouting is performed outside the rectangular tunnel. The torsional force generated by the reaction force of the unbalanced grouting is used to push the tunnel to rotate to the design posture. After the tunnel is straightened, balanced grouting is switched to pressure maintenance to maintain the tunnel posture and ensure the stability of the soil above the tunnel.

[0013] S7. Slurry replacement: After the tunnel is straightened, a dual-liquid slurry is used to replace the grouting slurry from step S4 and the unbalanced grouting slurry from step S6.

[0014] Furthermore, taking the centerline of each outer side of the rectangular tunnel as the limit, the side that hinders the tunnel's rotation is within the circular jacking pipe area, and the other side is outside the circular jacking pipe area. The soil within the circular jacking pipe area is the soil that hinders the tunnel's rotation. During the tunnel straightening process in step S6, grouting and pressure maintenance are continuously carried out within the circular jacking pipe area to ensure the stability of the soil above. Grouting is carried out outside the circular jacking pipe area to provide rotation torque. The grouting pressure P1 outside the circular jacking pipe area is initially slightly higher than the grouting pressure P2 within the circular jacking pipe area, and then gradually increases until the tunnel is completely straightened, and then decreases to be consistent with the grouting pressure P2 within the circular jacking pipe area. During unbalanced grouting, the grouting pressures outside the four outer sides of the rectangular tunnel are P1, P2, P1, P2, P1, P2, P1, P2, P1, P2. Since P1 > P2, the outer side of the tunnel can be subjected to torsional force, thereby straightening the tunnel.

[0015] Furthermore, two grouting systems are installed inside the rectangular tunnel: one for grouting within the circular jacking pipe area, including the pipe retraction filling in step S4, and the other for grouting outside the circular jacking pipe area.

[0016] Furthermore, during the tunneling process of the circular pipe jacking machine in step S3, the grouting system of the circular pipe jacking machine itself and the grouting system inside the tunnel are used to maintain pressure, so as to ensure the stability of the soil above the tunnel after the circular pipe jacking machine has tunneled.

[0017] Furthermore, the grouting slurry mentioned in step S4 includes mud, cement and calcium chloride, with a weight ratio of (1000-1200):1:(0.1-0.3). The mud has a specific gravity of 1.1 and a viscosity of 23s at room temperature.

[0018] More preferably, the weight ratio of mud, cement and calcium chloride is 1100:1:0.2.

[0019] Furthermore, the mixed grout used for sealing the tunnel portal in step S5 includes bentonite, cement, and calcium chloride, with a weight ratio of 1:(2-4):(0.3-0.5).

[0020] More preferably, the weight ratio of bentonite, cement and calcium chloride is 1:3:0.4.

[0021] Further, the two-component slurry in step S7 includes cement slurry and water glass solution, with a weight ratio of cement slurry to water glass solution of 1:(1.5-2.5), a weight ratio of cement to water in the cement slurry of 1:(0.8-1.2), and a Baume degree of 40 in the water glass solution.

[0022] Furthermore, the weight ratio of cement slurry to water glass solution is 1:2, and the weight ratio of cement to water in the cement slurry is 1:1.

[0023] The beneficial effects of this invention are as follows: During the construction of rectangular pipe jacking, if twisting occurs, resulting in a certain angle of twist after the tunnel is formed, a small-sized circular pipe jacking machine is used to clear the soil obstructing the tunnel's rotation and provide rotation space. The rotation torque generated by unbalanced grouting propels the formed tunnel to rotate. Simultaneously, after the tunnel is straightened, a mixed grout is used to replace and solidify the mud in the gaps around the tunnel, achieving the effect of completely straightening the twisted formed tunnel and avoiding any impact on the tunnel's normal function or quality problems caused by tunnel twisting. Furthermore, grouting and pressure maintenance are continuously carried out during the excavation of the rotating soil and the unbalanced grouting process to ensure the stability of the soil above the tunnel and guarantee construction safety. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the rotation measures during the pipe jacking construction stage according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the torsion of a rectangular pipe jacking tunnel according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the rectangular jacking tunnel hindering the rotation of the soil, and a schematic diagram of the dimensions and path of the circular jacking pipe, according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of circular pipe jacking in an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of the installation of grouting pipes inside the molded tunnel according to an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of unbalanced grouting and rotational torque in an embodiment of the present invention.

[0030] Figure 7 This is a schematic diagram of the straightening of the formed tunnel according to an embodiment of the present invention.

[0031] Figure 8 This is a schematic diagram of mud replacement in an embodiment of the present invention. Detailed Implementation

[0032] like Figure 1 As shown, during the construction of a rectangular tunnel using pipe jacking, if tunnel twisting is detected, measures such as reversing the rotation direction of the cutterhead and adding weights at corresponding positions within the tunnel are generally adopted. Through the reaction force of the soil on the cutterhead and the rotational torque generated by the weight of the weights, the pipe jacking machine and the tunnel under construction can be slowly straightened or the twisting trend can be effectively controlled. However, because the rectangular pipe jacking twists, the excavation becomes at a certain angle relative to the designed tunnel cross-section, resulting in some blind spots that cannot be cut. The cutterhead cannot effectively cut the soil according to the designed cross-section, and the surrounding soil will compress the tunnel, hindering its rotation. This results in poor twist correction during construction, and a twist angle α will appear after the tunnel is formed. Figure 2 As shown.

[0033] A method for correcting torsion in a rectangular pipe jacking tunnel includes the following steps:

[0034] S1. Measurement: By measuring the orientation of the formed tunnel, and based on the relevant drawings, such as... Figure 2 As shown, the torsion angle α of the tunnel is obtained.

[0035] S2. Determine the pipe jacking machine model and tunneling route: Based on the tunnel's torsion angle α, determine the extent of soil outside the tunnel that hinders its rotation. The extent of the soil can be as follows: Figure 3As shown, the tunnel's design orientation, actual orientation, torsion angle α, and dimensions are determined based on the drawings. A suitable circular pipe jacking machine and its excavation route are selected based on the extent (size, shape, etc.) and type of soil obstructing tunnel rotation. The selection principle is to clear as much soil as possible that obstructs rotation, ensuring no dead zones at any tunnel angle, thus providing space for tunnel rotation. The size of the circular pipe jacking machine must be selected according to the size of the soil to be cleared. If the machine is too small, more jacking passes are required, affecting construction efficiency; if the machine is too large, it will increase the impact on the surrounding soil, which is detrimental to soil stability.

[0036] The extent of soil outside the tunnel that obstructs tunnel rotation can be determined using the following method: (e.g.) Figure 3 With the centerline of each outer side of the rectangular tunnel as the limit, the side that hinders the tunnel's rotation is within the circular jacking pipe area, and the other side is outside the circular jacking pipe area. The soil within the circular jacking pipe area is the soil that hinders the tunnel's rotation.

[0037] S3. Pipe jacking excavation: Based on the selected circular pipe jacking machine and excavation route, such as... Figure 4 The process involves excavating and clearing soil that obstructs tunnel rotation. During the excavation of the circular pipe jacking machine, pressure is maintained using both the machine's own grouting system and the tunnel's internal grouting system to ensure the stability of the soil above the tunnel after excavation. The grout used for pipe jacking can be conventional pipe jacking grout, such as mud.

[0038] S4. Pipe Retraction and Filling: After the circular pipe jacking machine reaches the diaphragm wall of the receiving shaft, appropriate pipe removal technology is used for pipe removal. During the pipe removal process, backfill grout is injected for filling, and the backfill grouting pressure is greater than the static soil and water pressure. The backfill grouting pressure should be 20 kPa higher than the groundwater and soil pressure, and pressure gauges can be used for real-time monitoring to ensure complete filling and ensure soil stability. Backfill grouting is mainly to ensure the stability of the soil layer above the tunnel and to ensure that it does not hinder tunnel rotation. The backfill grout is determined through testing, and grout mixing ratio tests are conducted in advance. Grout filling is crucial during the pipe removal process.

[0039] The grouting fluid for retreating includes mud, cement, and calcium chloride, with a weight ratio of (1000-1200):1:(0.1-0.3), preferably 1100:1:0.2. The mud has a specific gravity of 1.1 and a viscosity of 23s at room temperature. This grout has a certain degree of self-supporting properties, resisting the pressure of the surrounding soil layers and maintaining soil stability, while not completely solidifying, thus reducing the impact on subsequent circular pipe jacking and subsequent mud replacement.

[0040] S5. Tunnel Portal Sealing: The tunnel portal of the launching shaft is sealed with a mixed grout. When the circular pipe jacking machine retreats to the position of the launching shaft portal, it stops retreating, allowing the pipe jacking machine to block the portal. After the mixed grout solidifies, the pipe jacking machine is withdrawn. After the pipe jacking machine has completely withdrawn, the portal is sealed with quick-setting cement.

[0041] The mixed slurry includes bentonite, cement and calcium chloride, with a weight ratio of bentonite, cement and calcium chloride of 1:(2-4):(0.3-0.5), preferably 1:3:0.4.

[0042] S6, Tunnel Correction: (e.g., ...) Figure 6 Unbalanced grouting is performed outside the rectangular tunnel. The torsional force generated by the reaction force of the unbalanced grouting propels the tunnel to its designed orientation. Figure 7 Once the tunnel is straightened, the process switches to balanced grouting and pressure maintenance to maintain the tunnel's orientation and ensure the stability of the soil above the tunnel.

[0043] Uneven grouting here refers to the imbalance of grouting pressure on the outer sides of a rectangular tunnel. Specifically, it refers to the imbalance between the grouting pressure within the circular jacking pipe area and the grouting pressure outside the circular jacking pipe area on each outer side. During tunnel straightening, grouting and pressure maintenance are continuously carried out within the circular jacking pipe area to ensure the stability of the soil above. The grouting uses the aforementioned retreating grouting slurry. Grouting is carried out outside the circular jacking pipe area to provide rotational torque. The grouting pressure P1 outside the circular jacking pipe area is initially slightly higher than the grouting pressure P2 within the circular jacking pipe area, and then gradually increases until the tunnel is completely straightened, at which point it decreases to match the grouting pressure P2 within the circular jacking pipe area. During unbalanced grouting, the grouting pressures on the four outer sides of the rectangular tunnel are, in order, P1, P2, P1, P2, P1, P2, P1, P2. Since P1 > P2, the outer side of the tunnel can be subjected to torsional force, thus straightening the tunnel.

[0044] The grout outside the circular jacking pipe area (grout for unbalanced grouting) can be conventional mud, and its specific gravity needs to be determined based on the strata and field tests. It is generally thick mud.

[0045] like Figure 5 Two grouting systems are installed inside the rectangular tunnel. One system is used for grouting within the circular jacking pipe area, including the pipe retraction filling in step S4. The grout used is the retraction grout. The other system is used for grouting outside the circular jacking pipe area. The grout used is a conventional grout, such as mud.

[0046] S7, Mud Replacement: (e.g.) Figure 8 After the tunnel is straightened, a dual-liquid grout is used to replace the retreat grout in step S4 and the unbalanced grout in step S6.

[0047] The two-component grout consists of cement slurry and water glass solution, with a weight ratio of cement slurry to water glass solution of 1:(1.5-2.5). The cement slurry contains cement with a water weight ratio of 1:(0.8-1.2), and the water glass solution has a Baume degree of 40. Preferably, the water-cement ratio of the cement slurry is 1:1, and the weight ratio of the water glass solution to the cement slurry is 2:1. Using a two-component grouting method results in a short gel time, achieving rapid reinforcement and filling of soil voids, improving the soil's bearing capacity and shear strength, and providing excellent waterproofing and seepage prevention.

[0048] Slurry replacement can be carried out using the same method as in normal pipe jacking. Grouting replacement is performed every three pipe sections (4.5m) at intervals, with the intervals increased as needed. The grouting sequence is from bottom to top. During the grouting process, the replaced slurry can flow out from the hole closest to the grouting pipe (by injecting cement slurry to drive the original slurry to nearby holes). The standard for successful replacement is that when the replaced slurry has the same flow rate as the injected slurry and is the same as the injected slurry, grouting can be stopped and the process can be moved to the next hole.

[0049] The technical solution of this invention was applied to the construction of an underground tunnel in a certain city. The rectangular tunnel is approximately 7m × 5m in size, with a soil cover of 9.81m and a torsion angle of approximately 1.7°. During the torsion correction construction, a circular pipe jacking machine was first used to remove the soil on the four sides of the rectangular tunnel that caused its torsion, while grouting was simultaneously injected to maintain pressure. The pressure was maintained at a level 20kPa higher than the soil and water pressure, approximately 170kPa. During the tunnel straightening process, thick mud was used for unbalanced grouting on the other side of the four sides of the rectangular tunnel. The grouting pressure was slowly increased from the initial 170kPa to 200kPa. During the straightening process, the torsion angle of the tunnel was closely monitored until it was controlled below 1.3° (within the allowable range of the tunnel specifications). The grouting pressure was then reduced to 170kPa, and mud replacement was then carried out.

[0050] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. A method for correcting torsion in a rectangular pipe jacking tunnel, characterized in that, Includes the following steps: S1. Measurement: The torsion angle α of the tunnel is obtained by measuring the posture of the formed tunnel; S2. Determine the pipe jacking machine model and tunneling route: Determine the range of soil around the tunnel that hinders the tunnel's rotation based on the tunnel's torsion angle α, and select a suitable circular pipe jacking machine and tunneling route based on the range and type of soil that hinders the tunnel's rotation. S3. Pipe jacking excavation: Based on the selected circular pipe jacking machine and excavation route, the soil that hinders the tunnel rotation is excavated and cleared. S4. Pipe Removal and Filling: After the circular pipe jacking machine has advanced to the diaphragm wall of the receiving well, appropriate pipe removal technology is used for pipe removal. During the pipe removal process, back-removal grout is injected for filling, and the back-removal grouting pressure is ensured to be greater than the static water and soil pressure to ensure complete filling. S5. Tunnel Portal Sealing: The tunnel portal of the launching shaft is sealed with a mixed grout. When the circular pipe jacking machine retracts to the position of the launching shaft portal, it stops retracting, allowing the pipe jacking machine to block the portal. After the mixed grout solidifies, the pipe jacking machine is withdrawn. After the pipe jacking machine is completely withdrawn, the portal is sealed with quick-setting cement. S6. Tunnel straightening: Unbalanced grouting is performed outside the rectangular tunnel. The torsional force generated by the reaction force of the unbalanced grouting is used to push the tunnel to rotate to the design posture. After the tunnel is straightened, balanced grouting is switched to pressure maintenance to maintain the tunnel posture and ensure the stability of the soil above the tunnel. S7. Slurry replacement: After the tunnel is straightened, the grouting slurry in step S4 and the unbalanced grouting slurry in step S6 are replaced with two-liquid slurry.

2. The torsion correction method for a rectangular pipe jacking tunnel according to claim 1, characterized in that, With the centerline of each outer side of the rectangular tunnel as the limit, the side that hinders the tunnel's rotation is within the circular jacking pipe, and the other side is outside the circular jacking pipe. The soil within the circular jacking pipe is the soil that hinders the tunnel's rotation. During the tunnel straightening process in step S6, grouting and pressure maintenance are continuously carried out within the circular jacking pipe to ensure the stability of the soil above. Grouting is carried out outside the circular jacking pipe to provide rotation torque. The grouting pressure P1 outside the circular jacking pipe is initially slightly higher than the grouting pressure P2 within the circular jacking pipe, and then gradually increases until the tunnel is completely straightened, and then decreases to be consistent with the grouting pressure P2 within the circular jacking pipe.

3. The torsion correction method for a rectangular pipe jacking tunnel according to claim 2, characterized in that, Two grouting systems are installed inside the rectangular tunnel: one for grouting within the circular jacking pipe area, including the pipe retraction filling in step S4, and the other for grouting outside the circular jacking pipe area.

4. The torsion correction method for a rectangular pipe jacking tunnel according to claim 1, characterized in that, In step S3, during the excavation of the circular pipe jacking machine, the machine's own grouting system and the tunnel's internal grouting system are used to maintain pressure, ensuring the stability of the soil above the tunnel after the circular pipe jacking machine has excavated.

5. The torsion correction method for a rectangular pipe jacking tunnel according to claim 1, characterized in that, The grouting fluid mentioned in step S4 includes mud, cement and calcium chloride, with a weight ratio of (1000-1200):1:(0.1-0.3). The mud has a specific gravity of 1.1 and a viscosity of 23s at room temperature.

6. The torsion correction method for a rectangular pipe jacking tunnel according to claim 5, characterized in that, The weight ratio of mud, cement and calcium chloride is 1100:1:0.

2.

7. The torsion correction method for a rectangular pipe jacking tunnel according to claim 1, characterized in that, The mixed grout used for sealing the tunnel portal in step S5 includes bentonite, cement, and calcium chloride, with a weight ratio of 1:(2-4):(0.3-0.5).

8. The method for correcting torsion in a rectangular pipe jacking tunnel according to claim 7, characterized in that, The weight ratio of bentonite, cement and calcium chloride is 1:3:0.

4.

9. The method for correcting torsion in a rectangular pipe jacking tunnel according to claim 1, characterized in that, The two-component slurry in step S7 includes cement slurry and water glass solution, with a weight ratio of cement slurry to water glass solution of 1:(1.5-2.5). The weight ratio of cement to water in the cement slurry is 1:(0.8-1.2), and the Baume degree of the water glass solution is 40.

10. The method for correcting torsion in a rectangular pipe jacking tunnel according to claim 9, characterized in that, The weight ratio of cement slurry to water glass solution is 1:2, and the weight ratio of cement to water in the cement slurry is 1:1.

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