Construction method for shield tunneling machine to penetrate through existing pile foundation

Abstract

The invention discloses a construction method for a shield to pass through an existing pile foundation, which belongs to the technical field of interval shield tunnel underpass, and comprises four parts of pile foundation underpinning design, pile foundation underpinning automatic monitoring and precision control, shield active direct grinding crossing and shield crossing automatic monitoring and cooperative control. According to the pile foundation underpinning design, the stratum disturbance influence of shield crossing is fully considered, and the strength, rigidity and node design of an underpinning structure are optimized; an automatic monitoring system is adopted for pile foundation underpinning and shield crossing, synchronous transmission and fusion analysis of monitoring data are achieved, high-precision control measures are combined, the construction state is fed back in real time, and automatic deviation correction is achieved. The method has the advantages that the problems that in the prior art, shield crossing influences are not considered in pile foundation underpinning design, the passive cutting risk of shield crossing is high, and cooperative control over the two is insufficient are solved, the construction safety, reliability and efficiency are improved, and the method is suitable for shield crossing pile foundation engineering in urban dense building areas.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine (TBM) construction technology, and in particular to a method for TBMs to pass through existing pile foundations, which is especially applicable to scenarios where TBM construction in urban subways, municipal tunnels, etc., requires passing through the pile foundations of existing buildings. Background Technology

[0002] With the continuous development of urban underground space, shield tunneling has been widely used in tunnel engineering due to its advantages of minimal disturbance to the surrounding environment and high construction efficiency. However, in densely built-up urban areas, shield tunnels inevitably need to pass through the pile foundations of existing buildings. In this case, reasonable technical means are needed to solve the spatial conflict between the pile foundations and the tunnel.

[0003] In existing technologies, the handling of tunnel boring machines (TBMs) crossing pile foundations mainly falls into two categories: one is to avoid the pile foundation by adjusting the tunnel route, but this method is limited by geological conditions and surrounding pipelines, and its applicability is relatively narrow; the other is to replace the pile foundation and then have the TBM pass through the replacement structure or the original pile foundation location. Among these, pile foundation replacement technology is relatively mature, but traditional replacement designs often do not fully consider the impact of ground disturbance and vibration generated during the TBM crossing process, leading to the risk of sudden stress changes in the replacement structure; at the same time, if the TBM adopts a passive cutting method for the pile foundation during the crossing, problems such as accelerated tool wear and TBM instability are likely to occur.

[0004] In addition, in existing combined construction, the monitoring of pile foundation replacement and shield tunneling is mostly carried out independently, and the monitoring data is not synchronized, making it difficult to achieve coordinated control between the two; moreover, the monitoring accuracy and automation level are low, and it is impossible to provide real-time feedback on key parameters such as deformation and stress during the construction process, which can easily lead to construction safety hazards. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a construction method for shield tunneling through existing pile foundations, which combines shield active direct grinding tunneling with pile foundation underpinning technology, clarifies the targeted design requirements for pile foundation underpinning, and achieves automated monitoring and high-precision control of both construction processes, thereby ensuring construction safety and project quality.

[0006] The objective of this invention is achieved through the following technical solutions: A method for tunneling a shield through an existing pile foundation, characterized in that the method includes: Including pile foundation underpinning design: Based on the influence of ground settlement, horizontal displacement and vibration load caused by shield tunneling, a combination structure of underpinning beam and temporary support is adopted. The connection nodes between the underpinning beam and the existing pile foundation and underpinning pile are rigidly connected and shear keys and anchoring steel bars are set. Automated monitoring and precision control of pile foundation underpinning: During shield tunneling, the process of pile foundation underpinning is automatically monitored, and the deformation and stress state of the underpinning structure under the influence of the underpinning process and shield tunneling are analyzed. Shield tunneling active direct grinding crossing design: Based on the monitoring results of pile foundation underpinning, the actual process of shield tunneling grinding crossing is adjusted through tool configuration optimization, construction parameter control and grinding path planning.

[0007] The concrete strength grade of the replacement beam shall not be lower than C40, the longitudinal reinforcement ratio shall not be lower than 1.5%, and the horizontal distance between the center of the replacement pile and the outer contour of the shield tunnel shall not be less than 1.5 times the tunnel diameter.

[0008] The length of the anchorage reinforcement at the connection node between the underpinning beam and the existing pile foundation and underpinning pile shall not be less than 35d, where d is the diameter of the reinforcement.

[0009] The monitoring parameters for pile foundation underpinning include the settlement, horizontal displacement, and strain of the underpinning beam, the axial force and bending moment of the existing pile foundation, the settlement of the underpinning pile, and the settlement of the surrounding strata.

[0010] By monitoring the shield's attitude, cutterhead vibration frequency, grinding resistance, settlement of the surrounding strata, and real-time deformation of the underpinning structure, the shield construction monitoring system and the pile foundation underpinning automated monitoring system are connected to achieve synchronous fusion and analysis of monitoring data. When the monitoring data is abnormal, the shield construction parameters are automatically adjusted.

[0011] The shield attitude monitoring uses inertial navigation monitoring equipment. When the shield attitude deviation exceeds ±3mm or the cutterhead vibration frequency exceeds 5Hz, the system automatically adjusts the shield construction parameters.

[0012] Vibration monitoring sensors are installed at the root of the tunnel boring machine cutter to provide real-time feedback on the cutter wear status.

[0013] The monitoring points for automated monitoring and precision control of pile foundation underpinning are arranged at the mid-span and support of the underpinning beam, the top of the existing pile foundation, the pile body, the top of the underpinning pile, and the strata within the influence range of the shield tunneling, with a spacing of no more than 2m between monitoring points.

[0014] The advantages of this invention are: 1) By fully considering the impact of shield tunneling in the pile foundation underpinning design, and optimizing the strength, stiffness and node design of the underpinning structure, the underpinning system's ability to resist shield tunneling disturbances has been effectively improved, and the risk of structural instability has been reduced.

[0015] 2) The shield tunneling active direct grinding crossing scheme is adopted, and the tool configuration and construction parameters are optimized. Compared with the traditional passive cutting, the crossing efficiency is improved, tool wear is reduced, and the shield attitude is stabilized.

[0016] 3) Both pile foundation replacement and shield tunneling adopt automated monitoring methods, realizing synchronous transmission and collaborative analysis of monitoring data. Combined with high-precision control measures, the construction status is fed back in real time and corrections are made in a timely manner, which greatly improves the construction accuracy and safety.

[0017] 4) This combined technical solution is highly applicable and can be widely used in shield tunneling through pile foundation projects in densely built urban areas, reducing the impact on existing buildings and lowering construction costs and schedule risks. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the planar layout of the present invention. Detailed Implementation

[0019] The features and other related features of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so as to facilitate understanding by those skilled in the art: like Figure 1 As shown in the figure, the markings represent: 1. Pier, 2. Original bridge pile connecting beam, 3. Replaced bridge pile, 4. Part of the replaced bridge pile to be broken, 5. Drill hole, 6. Steel pipe pile, 7. Concrete pile core, 8. Enlarged head, 9. Isolation layer, 10. Replacement beam, 11. Self-locking jack, 12. Pile cap, 13. Drilled pile, 14. Reinforced concrete slab support, 15. C20 plain concrete cushion layer.

[0020] Example: In this example, the construction method for shield tunneling through existing pile foundations adopts a combined construction mode of shield active direct grinding tunneling and pile foundation underpinning. The combined design fully considers the impact of shield tunneling on pile foundation underpinning, optimizing the pile foundation underpinning scheme from the perspectives of monitoring design and precision control. Simultaneously, the shield active grinding tunneling scheme is optimized, and both construction processes utilize automated monitoring for coordinated control. Specifically, this includes: 1) Pile foundation underpinning design (considering the impact of shield tunneling): Based on the tunnel boring machine's crossing path, geological conditions, and existing pile foundation parameters, a targeted design for pile foundation replacement was carried out.

[0021] Design of the strength and stiffness of the underpinning structure: Based on the ground settlement, horizontal displacement and vibration load generated during the tunnel boring machine's passage, the additional stress on the underpinning structure is calculated. A combined structure of "underpinning beam + temporary support" is adopted. The concrete strength grade of the underpinning beam is not lower than C40, and the longitudinal reinforcement ratio is not lower than 1.5%, to ensure that the underpinning structure can withstand the additional load caused by the tunnel boring machine's passage and avoid excessive structural deformation.

[0022] Design of replacement pile layout: The replacement piles should avoid the shield tunnel crossing path, and the horizontal distance between their center and the outer contour of the shield tunnel should not be less than 1.5 times the tunnel diameter; at the same time, based on the characteristics of stress redistribution in the strata during shield tunnel crossing, the spacing of the replacement piles should be optimized, and the spacing should be controlled at 3-5m to ensure the overall stability of the replacement system.

[0023] Design of the underpinning node: The connection node between the underpinning beam and the existing pile foundation and underpinning pile adopts rigid connection, and shear keys and anchoring steel bars are set. The anchoring length is not less than 35d (d is the diameter of the steel bar) to ensure reliable force transmission at the node and avoid loosening of the node due to shield tunneling vibration.

[0024] 2) Automated monitoring and precision control scheme for pile foundation underpinning: To monitor the deformation and stress state of the underpinning structure in real time during the underpinning process and under the influence of the tunnel boring machine (TBM) crossing, and to achieve high-precision control, an automated monitoring system is adopted. The specific scheme is as follows: Monitoring parameters and measurement point layout: The monitoring parameters include the settlement, horizontal displacement, and strain of the replacement beam, the axial force and bending moment of the existing pile foundation, the settlement of the replacement pile and the settlement of the surrounding strata; monitoring points are arranged at the mid-span and support of the replacement beam, the top and body of the existing pile foundation, the top of the replacement pile and the strata within the shield tunneling influence range (3 times the tunnel diameter on both sides of the tunnel center), with a measurement point spacing of no more than 2m.

[0025] Automated monitoring equipment selection: Fiber optic grating sensors (for strain monitoring), automated total stations (for displacement monitoring), and vibrating wire axial force gauges (for pile foundation axial force monitoring) are selected. All equipment achieves real-time data transmission through data acquisition terminals, with a transmission frequency of no less than once per 5 minutes.

[0026] Precision control standards and measures: The settlement control accuracy of the replacement beam is ±2mm, and the horizontal displacement control accuracy is ±1mm; when the monitoring data approaches the warning value (80% of the control accuracy), the warning is automatically triggered, and the deviation is corrected by adjusting the jacking force of the replacement jack (adjustment accuracy is ±5kN) and adding temporary supports, etc., to ensure that the replacement accuracy meets the requirements.

[0027] 3) Shield tunneling active direct grinding crossing scheme: For existing pile foundation remnants or obstacle piles that need to be traversed, an active grinding method using a tunnel boring machine (TBM) will be adopted. The TBM cutter configuration and construction parameters will be optimized. The specific plan is as follows: Cutting tool configuration optimization: Wear-resistant alloy grinding tools are added to the shield cutterhead, with the cutting edge angle set to 30-45° and the tool spacing adjusted according to the pile foundation reinforcement spacing (not greater than 20cm); the tools are densely arranged in the center and edge areas of the cutterhead to improve the grinding efficiency of the pile foundation concrete and reinforcement. At the same time, vibration monitoring sensors are installed at the root of the tools to provide real-time feedback on the tool wear status.

[0028] Construction parameter control: The shield tunneling speed is controlled at 5-10 mm / min, the cutterhead rotation speed is controlled at 1.5-2.5 r / min, and the propulsion force is adjusted in real time according to the grinding resistance (not exceeding 70% of the rated propulsion force); synchronous grouting uses early-strength grout, and the grouting pressure is controlled at 0.3-0.5 MPa to ensure that the grouting fills the voids generated by grinding in time and reduces ground settlement.

[0029] Grinding path planning: The location, size and depth of the existing pile foundation are detected in advance by three-dimensional ground radar. Combined with the shield attitude monitoring data, a precise grinding path is planned to ensure that the shield passes through along the design axis and avoids uneven stress on the supporting structure due to deviation from the axis.

[0030] 4) Automated monitoring solution for active grinding tunneling of shield tunnels: To control the shield tunneling attitude in real time, monitor ground deformation and the affected state of the underpinning structure, and achieve coordination with pile foundation underpinning monitoring, the following automated monitoring scheme is adopted: Monitoring parameters and measurement point layout: Monitoring parameters include shield attitude (horizontal deviation, vertical deviation, roll angle), cutterhead vibration frequency, grinding resistance, settlement of the surrounding strata and real-time deformation of the underpinning structure; inertial navigation monitoring equipment is installed on the shield machine body, and monitoring points are added to the surrounding strata and underpinning structure (linked with the pile foundation underpinning monitoring points).

[0031] Automated monitoring and collaborative control: Through data docking between the shield tunneling monitoring system and the pile foundation underpinning automated monitoring system, the monitoring data can be synchronously integrated and analyzed; when the shield attitude deviation exceeds ±3mm, the cutterhead vibration frequency exceeds 5Hz, or the deformation of the underpinning structure approaches the warning value, the system automatically adjusts parameters such as the shield advance speed and cutterhead rotation speed to ensure that the construction of both is coordinated and controllable.

[0032] In practical implementation, this embodiment includes the following application scenarios: A subway shield tunnel project in a certain city has a tunnel diameter of 6.2m and is being constructed using an earth pressure balance shield tunneling machine. It needs to pass through the reinforced concrete pile foundations of an existing multi-story residential building. The piles are 1.2m in diameter, 25m long, and have a top elevation of -2.5m. The strata in the traversing area are mainly silty clay with a bearing capacity characteristic value of 180kPa and a groundwater level of -4.0m.

[0033] Preliminary survey and design: Three-dimensional ground-penetrating radar was used to detect the accurate location, size and burial depth of the existing pile foundations. Combined with the shield tunnel axis, the pile foundation replacement range and shield grinding path were determined. Based on the calculation of ground disturbance during shield tunneling, the replacement beam size was determined to be 1.2m×1.5m (width×height), using C40 concrete, with HRB400 longitudinal reinforcement and a reinforcement ratio of 1.8%. The replacement piles were 1.0m diameter bored piles with a spacing of 4m.

[0034] Construction and Automated Monitoring of Pile Foundation Replacement: Construction of replacement piles and replacement beams, installation of fiber optic strain sensors at the mid-span and supports of the replacement beams, installation of vibrating wire axial force gauges at the top and body of existing piles, and deployment of automated total station measuring points in the strata within a range of 3 times the tunnel diameter on both sides of the top of the replacement piles and the center of the tunnel; all monitoring equipment is connected to the data acquisition terminal, with a settlement warning value of 1.6 mm and a horizontal displacement warning value of 0.8 mm set.

[0035] Loading and precision adjustment of the underpinning system: The underpinning beam is loaded in stages using jacks to simulate the additional load of the shield tunneling, and the deformation and stress of the underpinning structure are monitored in real time; when the mid-span settlement of the underpinning beam is monitored to be 1.5mm, the jacking force is adjusted to the design value to ensure that the underpinning precision meets the requirements.

[0036] Active grinding tunneling construction and collaborative monitoring: The shield cutterhead was modified by adding 12 wear-resistant alloy grinding tools with a cutting edge angle of 35° and a tool spacing of 18cm; the shield advance speed was controlled at 8mm / min, the cutterhead rotation speed at 2.0r / min, and the thrust force was controlled at 65% of the rated thrust force; the shield attitude monitoring system and the pile foundation underpinning monitoring system were activated simultaneously, and the data were integrated and analyzed in real time; during construction, when the horizontal deviation of the shield attitude was detected to be 2.8mm, the system automatically adjusted the thrust cylinder pressure to correct the shield attitude.

[0037] Post-construction monitoring: After the shield tunneling is completed, the deformation of the underpinning structure and surrounding strata will be continuously monitored for 30 days to ensure that the deformation is stable and there is no risk of subsequent settlement.

[0038] In the above-mentioned application conditions, the maximum settlement during the pile foundation replacement process was 1.7 mm and the horizontal displacement was 0.9 mm, both of which were controlled within the accuracy requirements; the shield active grinding crossing efficiency reached 8 m / day, which is 50% higher than the traditional passive cutting and the tool wear is reduced by 30%; no problems such as instability of the replacement structure or loss of shield attitude occurred during the entire construction process, and the settlement of surrounding buildings was controlled within 3 mm, which meets the engineering safety requirements.

[0039] Although the above embodiments have described the concept and embodiments of the present invention in detail with reference to the accompanying drawings, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.

Claims

1. A method for tunneling a shield through an existing pile foundation, characterized in that: The construction method includes: Including pile foundation underpinning design: Based on the influence of ground settlement, horizontal displacement and vibration load caused by shield tunneling, a combination structure of underpinning beam and temporary support is adopted. The connection nodes between the underpinning beam and the existing pile foundation and underpinning pile are rigidly connected and shear keys and anchoring steel bars are set. Automated monitoring and precision control of pile foundation underpinning: During shield tunneling, the process of pile foundation underpinning is automatically monitored, and the deformation and stress state of the underpinning structure under the influence of the underpinning process and shield tunneling are analyzed. Shield tunneling active direct grinding crossing design: Based on the monitoring results of pile foundation underpinning, the actual process of shield tunneling grinding crossing is adjusted through tool configuration optimization, construction parameter control and grinding path planning.

2. The construction method for shield tunneling through existing pile foundations according to claim 1, characterized in that: The concrete strength grade of the replacement beam shall not be lower than C40, the longitudinal reinforcement ratio shall not be lower than 1.5%, and the horizontal distance between the center of the replacement pile and the outer contour of the shield tunnel shall not be less than 1.5 times the tunnel diameter.

3. A construction method for shield tunneling through existing pile foundations according to claim 1 or 2, characterized in that: The length of the anchorage reinforcement at the connection node between the underpinning beam and the existing pile foundation and underpinning pile shall not be less than 35d, where d is the diameter of the reinforcement.

4. The construction method for shield tunneling through existing pile foundations according to claim 1, characterized in that: The monitoring parameters for pile foundation underpinning include the settlement, horizontal displacement, and strain of the underpinning beam, the axial force and bending moment of the existing pile foundation, the settlement of the underpinning pile, and the settlement of the surrounding strata.

5. The construction method for shield tunneling through existing pile foundations according to claim 1, characterized in that: By monitoring the shield's attitude, cutterhead vibration frequency, grinding resistance, settlement of the surrounding strata, and real-time deformation of the underpinning structure, the shield construction monitoring system and the pile foundation underpinning automated monitoring system are connected to achieve synchronous fusion and analysis of monitoring data. When the monitoring data is abnormal, the shield construction parameters are automatically adjusted.

6. The construction method for shield tunneling through existing pile foundations according to claim 5, characterized in that: The shield attitude monitoring uses inertial navigation monitoring equipment. When the shield attitude deviation exceeds ±3mm or the cutterhead vibration frequency exceeds 5Hz, the system automatically adjusts the shield construction parameters.

7. A construction method for shield tunneling through existing pile foundations according to claim 5, characterized in that: Vibration monitoring sensors are installed at the root of the tunnel boring machine cutter to provide real-time feedback on the cutter wear status.

8. The construction method for shield tunneling through existing pile foundations according to claim 1, characterized in that: The monitoring points for automated monitoring and precision control of pile foundation underpinning are arranged at the mid-span and support of the underpinning beam, the top of the existing pile foundation, the pile body, the top of the underpinning pile, and the strata within the influence range of the shield tunneling, with a spacing of no more than 2m between monitoring points.

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