A construction method for ensuring safety of shield tunnel under-pipe

Abstract

The application relates to a construction method for ensuring the safety of a shield tunnel underpassing a pipeline, which comprises the following steps: determining the maximum tensile strain increment [Delta epsilon t ] of the pipeline bottom at the intersection position of the shield tunnel and the pipeline plane projection; excavating the foundation, making a turning platform and a tensioning pedestal; installing and fixing a steel strand after forming a working face and providing a pre-tightening force through a jack; pasting a bottom strain gauge for measuring the pipeline longitudinal strain on the pipeline bottom at the intersection position of the shield tunnel and the pipeline plane projection; stopping the shield machine when the strain change cumulative value epsilon t is greater than 0.5 times [Delta epsilon t ]; eliminating epsilon t by gradually tensioning the steel strand through the jack; stopping the strain observation when epsilon t is less than 0.05 times [Delta epsilon t ] within three days; and restoring the ground after grouting in the pipeline longitudinal axis direction for 7-10 days. The application forms an efficient and low-cost construction method for effectively ensuring the safety of the pipeline, and the construction method is unique in process, mature in technology and beneficial to popularization.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering technology, and in particular relates to a construction method to ensure the safety of shield tunnels passing under pipelines. Background Technology

[0002] Shield tunnels have become the preferred choice for underground construction due to their advantages such as convenience, speed, safety, and space saving. However, shield tunnels generally pass through densely populated, bustling city centers with numerous surface buildings and extensive underground pipe networks, making it difficult to avoid crossing various underground pipelines in the city.

[0003] Underground pipelines are the lifeblood of a city, containing various water pipes, gas pipes, oil pipes, and more, playing a vital role in the city's operation. However, the construction of shield tunnels can cause these pipelines to deform and become overly stressed, potentially leading to accidents such as gas leaks, explosions, and water pipe bursts.

[0004] To ensure the safety of shield tunnels passing under pipelines, the traditional technical methods are as follows:

[0005] (1) Before the construction of the shield tunnel, the soil around the pipeline is reinforced by methods such as jet grouting, deep mixing, and layered grouting to reduce soil deformation and thus reduce pipeline deformation, thereby protecting the pipeline.

[0006] (2) Chinese Patent (Publication No.: CN217421213U, Publication Date: September 13, 2022) proposes a reinforcement structure for a shallow-buried tunnel for subway transfers that closely crosses storm and sewage pipelines. The structure includes multiple parallel steel pipes connected below the pipelines, with the steel pipes horizontally positioned perpendicular to the pipelines. Adjacent steel pipes are connected by interlocking fasteners, and the steel pipes are filled with cement mortar. Multiple sets of support structures are fixed to the bottom of the steel pipes and spaced apart along their length. Each set of support structures includes a square steel bar located below the steel pipe and above the tunnel, and a support plate fixed between the square steel bar and the steel pipe. The square steel bar is horizontally positioned perpendicular to the steel pipe. This invention solves the technical problem of poor reinforcement support effect in shallow-buried tunnels that closely cross storm and sewage pipelines by setting up steel pipes and support structures between the storm and sewage pipelines and the tunnel.

[0007] However, the aforementioned traditional methods for ensuring the safety of shield tunnel pipelines have the following problems:

[0008] (1) The main problems with soil reinforcement methods are: First, the reinforcement range is wide and deep, the workload is large and the cost is high. Second, the cement soil formed by soil reinforcement has low tensile strength, generally only a few tenths of a megapascal of tensile stress, which is difficult to withstand large deformation and stress; it belongs to passive reinforcement and cannot be adjusted in real time according to the pipeline safety requirements.

[0009] (2) The main problems with the reinforcement structure for closely passing through rainwater and sewage pipelines in the shallow buried tunnel for subway transfer proposed in Chinese Patent (Publication No.: CN217421213U, Publication Date: September 13, 2022) are: First, it is only applicable to multiple small-diameter pipelines, and cannot be solved when the pipeline diameter is large and there is only one pipeline; Second, it is a passive reinforcement and cannot be adjusted in real time according to the pipeline safety requirements. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a construction method to ensure the safety of shield tunnels passing under pipelines. This method achieves the cumulative strain change ε ​​of the bottom strain gauges by tensioning steel strands throughout the entire shield tunneling process. t The maximum allowable tensile strain increment [Δε] at the bottom of pipe 2, controlled at the intersection of the shield tunnel 1 and pipe 2 planar projections at 0.5 times. t The purpose of this is to ensure the safety of the pipeline during the tunnel boring machine (TBM) construction process.

[0011] A construction method to ensure the safety of a shield tunnel passing under a pipeline specifically includes the following steps:

[0012] Step 1: Determine the maximum allowable tensile strain increment [Δε] at the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection during shield tunnel construction. t ];

[0013] Step 2: Excavate the foundation and construct and install the turntable and tensioning platform for fixing the steel strands;

[0014] Step 3: Excavate the overburden above the pipeline along the direction of the shield tunnel to form a working face for laying steel strands; install and fix both ends of the steel strands on the turntable and tensioning platform, and pass the middle of the steel strands through the bottom of the pipeline; install jacks at both ends of the steel strands and provide pre-tensioning force.

[0015] Step 4: Attach a bottom strain gauge to the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection to measure the longitudinal strain of the pipeline. After connecting the bottom strain gauge to the data acquisition instrument, backfill the soil.

[0016] Steps 2 through 4 above must be completed before the tunnel boring machine advances towards the pipeline and is 4 to 6 times the diameter of the tunnel boring machine.

[0017] Step 5: When the distance between the tunnel boring machine and the pipeline is 6 to 8 times the diameter of the tunnel, begin monitoring the strain of the bottom strain gauges and obtain the cumulative strain change value ε. t During the tunnel boring machine's excavation process, as the machine advances, the cumulative strain change ε... t Greater than 0.5 times [Δε] t At this point, the tunnel boring machine stops excavating, and the accumulated strain value ε is eliminated by gradually tensioning the steel strands using jacks. t This process is repeated, and throughout the entire tunnel boring machine excavation process, the cumulative strain change ε ​​is always recorded. t Controlled at 0.5 times [Δε] t ]Inside;

[0018] Step 6: After the tunnel boring machine passes under the pipeline, it drives away from the pipeline, and the cumulative value of strain change ε ​​is continuously monitored. t If the cumulative strain change ε ​​within three days is satisfied t Less than 0.05 times [Δε] t Under the conditions of [the specified conditions], stop strain observation and proceed to the next step; Step 7: Grout the bottom of the pipe obliquely and symmetrically with cement grout along the longitudinal axis of the pipe;

[0019] Step 8: After 7 to 10 days, remove and retrieve the jacks; cut and retrieve the steel strands above ground; remove the tensioning platform and turntable, and restore the ground.

[0020] In step one, the maximum allowable tensile strain increment at the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection is determined using the finite element method.

[0021] In step two, the foundation is excavated, and concrete bases are poured on both sides of the pipeline to form turning platforms for the steel strands. An arc-shaped chute is set in the turning platform. A chute steel plate is installed on the surface of the chute and lubricating oil is applied to the surface of the chute steel plate.

[0022] Meanwhile, a tensioning platform is formed by pouring concrete on the outer side of the two turning platforms, that is, the side away from the pipeline, and a channel for threading steel strands is reserved in the tensioning platform.

[0023] The turning platforms on both sides of the pipeline are arranged symmetrically.

[0024] The working surface in step three is a V-shaped working surface.

[0025] The installation and fixing method of the steel strand in step three is as follows: after passing the steel strand through the hole of the tensioning platform on one side of the pipe, it is laid in the chute, then passes through the bottom of the pipe, and after passing through the chute on the other side of the pipe, it passes through the hole of the tensioning platform. The steel strand is turned by the turning platform.

[0026] In step three, a jack is used to apply a force of 5kN to 10kN to pre-tighten the steel strand.

[0027] In step five, when the cumulative strain change ε t Greater than 0.5 times [Δε] t After the tunnel boring machine stops excavating, the steel strands are tensioned step by step using jacks at 5kN increments until the cumulative strain change ε ​​is reached. t After the tensioning is removed, the tunnel boring machine resumes excavation.

[0028] In step seven, grout is injected at an angle of 30° to 50° along the longitudinal axis of the pipeline using a pressure of 0.5 to 1.0 MPa.

[0029] In step seven, the length L of grouting along the longitudinal axis of the pipe is... zj It is 10 to 15 times the diameter of the pipe.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention enables active control of the longitudinal strain at the bottom of the pipeline during the entire tunnel boring machine excavation process, ensuring the safety of the pipeline during tunnel construction. The equipment is simple, the technology is mature, and the cost is low.

[0032] 2. The jacks and some steel strands used in this invention are recyclable, overcoming the shortcomings of traditional technologies such as passive reinforcement, large workload, and high cost.

[0033] 3. After the tunnel boring machine (TBM) passes under the pipeline and leaves the pipeline, what is the cumulative strain change ε ​​over 3 days? t Less than 0.05 times [Δε] t If the reading is positive, it indicates that the impact of the tunnel boring machine's excavation on the pipeline is minimal, and strain monitoring can be stopped to proceed with the next steps, effectively ensuring the safety of the pipeline.

[0034] 4. In step 7 of this invention, the length L of grouting along the longitudinal axis of the pipe is... zj Within a range of 10 to 15 times the pipe diameter, grouting is performed at an angle of 0.5 to 1.0 MPa at the bottom of the pipe. This effectively fills the gap between the bottom of the pipe and the soil formed when the steel strands are lifted upwards, preventing vertical displacement of the pipe after the tension of the steel strands is released, which would otherwise result in the pipe being in an unfavorable stress condition.

[0035] 5. This invention forms a set of efficient, low-cost construction methods that effectively ensure pipeline safety when tunneling under a shield tunnel, and allows for partial recovery of jacks and steel strands. This construction method has unique processes, mature technology, and is easy to promote. Attached Figure Description

[0036] Figure 1This is a schematic diagram showing the cross-sectional positional relationship between the pipeline and the shield tunnel;

[0037] Figure 2 This is a schematic elevation view of the steel strand arrangement in this invention;

[0038] Figure 3 This is a plan view of the steel strand arrangement in this invention;

[0039] Figure 4 This is a schematic diagram of the elevation after the ground has been restored during construction in this invention;

[0040] Figure 5 This is a schematic diagram of the ground surface after construction in this invention, where L is the ground surface after restoration. zj This indicates the length of grout injected along the longitudinal axis of the pipeline;

[0041] in,

[0042] 1-Shield tunnel, 2-Pipeline, 3-Steel strand, 4-Turntable, 4a-Base, 4b-Slide chute, 4c-Slide chute steel plate, 5-Tensioning platform, 5a-Drain, 6-Jack, 7-Working face, 8-Bottom strain gauge, 9-Pipeline grouting reinforcement. Detailed Implementation

[0043] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] A construction method to ensure the safety of a shield tunnel passing under a pipeline specifically includes the following steps:

[0045] Step 1: The cross-sectional positional relationship between pipe 2 and shield tunnel 1 is as follows: Figure 1 As shown, the finite element method is first used to determine the maximum allowable tensile strain increment [Δε] at the bottom of pipe 2 at the intersection of the plane projections of shield tunnel 1 and pipe 2 during the construction of shield tunnel 1. t ].

[0046] Step 2: Construct the turntable 4 and tensioning platform 5

[0047] Excavate the foundation, and use concrete to pour base 4a on both sides of the pipeline 2 to form the turning platform 4 of the steel strand 3. Set the arc-shaped chute 4b in the turning platform 4. The turning platforms 4 on both sides of the pipeline 2 are symmetrically arranged. Install the chute steel plate 4c on the surface of the chute 4b and apply lubricating oil to the surface of the chute steel plate 4c.

[0048] Meanwhile, a tensioning platform 5 is formed by pouring concrete on the outer side of the two turning platforms 4, that is, on the side away from the pipe 2, and a channel 5a for threading the steel strand 3 is reserved in the tensioning platform 5.

[0049] Step 3: Excavate the overburden above pipe 2 along the direction of shield tunnel 1 to form a V-shaped working face 7 for laying steel strands 3; after passing the steel strands 3 through the hole 5a of the tensioning platform 5 on one side of pipe 2, lay them in the chute 4b, then pass through the bottom of pipe 2, and after passing through the chute 4b on the other side of pipe 2, pass through the hole 5a of the tensioning platform 5, and achieve the turning of the steel strands 3 through the turning platform 4; then install jacks 6 at both ends of the steel strands 3, and use the jacks 6 to apply a force of 5kN to 10kN to pre-tighten the steel strands 3, using the tensioning platform 5 to provide the reaction force required for tensioning, and the tensioning platform 5 can provide the support required for the jacks 6 to tension the steel strands 3. Figures 2-3 As shown.

[0050] Step 4: At the intersection of the plane projections of shield tunnel 1 and pipe 2, attach a bottom strain gauge 8 to the bottom of pipe 2 to measure the longitudinal strain of pipe 2. After connecting the bottom strain gauge 8 to the data acquisition instrument, backfill the soil, monitor the strain of the bottom strain gauge 8, and obtain the cumulative strain change value ε. t .

[0051] Steps 2 through 4 above must be completed before the tunnel boring machine advances towards pipe 2 and is 4 to 6 times the diameter of tunnel 1.

[0052] Step 5: When the distance between the tunnel boring machine and the pipeline is 6 to 8 times the diameter of the tunnel 1, start monitoring the strain of the bottom strain gauge 8 and obtain the cumulative strain change value ε. t As the tunnel boring machine advances, the cumulative strain change ε t Greater than 0.5 times [Δε] t At this point, the tunnel boring machine stops excavating, and the steel strands are tensioned in stages using jacks at 5kN increments until the cumulative strain change ε ​​is reached. t After the tension is removed, the tunnel boring machine (TBM) resumes excavation; this process is repeated, and the cumulative strain change ε ​​is always recorded throughout the entire TBM excavation process. t Controlled at 0.5 times [Δε] t ]Inside.

[0053] Based on construction experience and finite element analysis, it was found that when the distance between the tunnel boring machine (TBM) and the pipeline is greater than 6 to 8 times the diameter of the tunnel 1, the vertical displacement of the soil at pipeline 2 is relatively small when the TBM advances towards pipeline 2. Therefore, a distance of 6 to 8 times the diameter of the tunnel 1 is used as the control distance for the TBM's excavation and its influence on the vertical displacement of the soil at pipeline 2.

[0054] Step 6: After the tunnel boring machine passes under pipe 2, it drives away from pipe 2, and the cumulative value of strain change ε ​​is continuously observed. t If the cumulative strain change ε ​​within 3 days is satisfied t Less than 0.05 times [Δε] tUnder the conditions specified, stop strain observation and proceed with the next steps.

[0055] Step 7: Using a pressure of 0.5–1.0 MPa, grout the bottom of pipe 2 at an oblique angle of 30°–50° along the longitudinal axis of pipe 2. The length L of grouting along the longitudinal axis of pipe 2 is... zj The diameter of pipe 2 is 10 to 15 times that of pipe 2, and a pipe grouting reinforcement body 9 is formed at the bottom of pipe 2, such as... Figures 4-5 As shown.

[0056] Step 8: After 7 to 10 days, the cement slurry strength has developed to 70% to 85%, so the next step can be carried out: remove and recycle the jack 6; cut and recycle the steel strand 3 above ground; remove the tensioning platform 5 and the turning platform 4, and restore the ground; thus achieving the protection of the pipeline 2 during the construction of the shield tunnel 1.

[0057] Among them, 6 jacks are used to tension the steel strands 3. The vertical upward force generated by the steel strands 3 at the pipe 2 is used to overcome the vertical displacement of the pipe 2 when the shield tunnel passes under the pipe 2. This achieves active and effective control over the vertical downward displacement of the pipe 2, and avoids accidents caused by excessive vertical displacement and excessive stress in the pipe 2 during shield tunneling.

Claims

1. A construction method for ensuring the safety of a shield tunnel passing under a pipeline, characterized in that, Specifically, the following steps are included: Step 1: Determine the maximum allowable tensile strain increment [Δε] at the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection during shield tunnel construction. t ]; Step 2: Excavate the foundation and construct and install the turntable and tensioning platform for fixing the steel strands; Step 3: Excavate the overburden above the pipeline along the direction of the shield tunnel to form a working face for laying steel strands; install and fix both ends of the steel strands on the turntable and tensioning platform, with the middle of the steel strands passing through the bottom of the pipeline; install jacks at both ends of the steel strands and provide pre-tensioning force. Step 4: Attach a bottom strain gauge to the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection to measure the longitudinal strain of the pipeline. After connecting the bottom strain gauge to the data acquisition instrument, backfill the soil. Steps two through four above must be completed before the tunnel boring machine advances towards the pipeline and is 4 to 6 times the diameter of the tunnel boring machine. Step 5: When the tunnel boring machine is 6 to 8 times the diameter of the tunnel boring machine, begin monitoring the strain of the bottom strain gauges and obtain the cumulative strain change value ε. t During the tunnel boring machine's excavation process, as the machine advances, the cumulative strain change ε... t Greater than 0.5 times [Δε] t At this point, the tunnel boring machine stops excavating, and the accumulated strain value ε is eliminated by gradually tensioning the steel strands using jacks. t This process is repeated, and throughout the entire tunnel boring machine excavation process, the cumulative strain change ε ​​is always recorded. t Controlled at 0.5 times [Δε] t ]Inside; Step Six: After the tunnel boring machine passes under the pipeline, it drives away from the pipeline, and the cumulative strain change ε ​​is continuously monitored. t If the cumulative strain change ε ​​within three days is satisfied t Less than 0.05 times [Δε] t Under the conditions of [the specified conditions], stop strain observation and proceed to the next step; Step 7: Grout the bottom of the pipe obliquely and symmetrically with cement grout along the longitudinal axis of the pipe; Step 8: After 7 to 10 days, remove and retrieve the jacks; cut and retrieve the steel strands above ground; remove the tensioning platform and turntable, and restore the ground.

2. The construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step one, the maximum allowable tensile strain increment at the bottom of the pipeline at the intersection of the shield tunnel and the pipeline's planar projection is determined using the finite element method.

3. The construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step two, the foundation is excavated, and concrete bases are poured on both sides of the pipeline to form turning platforms for the steel strands. An arc-shaped chute is set in the turning platform. A chute steel plate is installed on the surface of the chute and lubricating oil is applied to the surface of the chute steel plate. Meanwhile, a tensioning platform is formed by pouring concrete on the outer side of the two turning platforms, that is, the side away from the pipeline, and a channel for threading steel strands is reserved in the tensioning platform.

4. The construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 3, characterized in that: The turning platforms on both sides of the pipeline are arranged symmetrically.

5. A construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: The working surface in step three is a V-shaped working surface.

6. The construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: The installation and fixing method of the steel strand in step three is as follows: after passing the steel strand through the hole of the tensioning platform on one side of the pipe, it is laid in the chute, then passes through the bottom of the pipe, and after passing through the chute on the other side of the pipe, it passes through the hole of the tensioning platform. The steel strand is turned by the turning platform.

7. A construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step three, a jack is used to apply a force of 5kN to 10kN to pre-tighten the steel strand.

8. A construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step five, when the cumulative strain change ε t Greater than 0.5 times [Δε] t After the tunnel boring machine stops excavating, the steel strands are tensioned step by step using jacks at 5kN increments until the cumulative strain change ε ​​is reached. t After the tensioning is removed, the tunnel boring machine resumes excavation.

9. A construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step seven, grout is injected at an angle of 30° to 50° along the longitudinal axis of the pipeline using a pressure of 0.5 to 1.0 MPa.

10. A construction method for ensuring the safety of a shield tunnel passing under a pipeline according to claim 1, characterized in that: In step seven, the length L of grouting along the longitudinal axis of the pipe is... zj It is 10 to 15 times the diameter of the pipe.

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