Protection operation method and protection device for construction bearing platform beside existing pipeline

Abstract

The invention discloses a protection operation method and protection device for a construction bearing platform beside an existing pipeline. The method comprises the steps that detailed investigation and evaluation are conducted on the pipeline in a construction area; a bearing platform foundation pit is excavated in a layered mode according to the designed elevation, and a steel casing is used for supporting the foundation pit; cleaning a main beam mounting ground surface, and pouring a concrete layer; a protection device is installed, and a main beam is installed on the corresponding concrete layer; secondary beams are vertically mounted on the main beams, and joists are mounted at the bottoms of the pipelines according to the secondary beam layout; a monitoring assembly is installed to conduct real-time monitoring on pipeline displacement and protection device component stress, real-time monitoring data and the initial digital model are fused, a dynamically-calibrated digital twinborn model is constructed, and prospective risk prediction and active early warning are conducted on subsequent construction steps; according to the prospective risk prediction and active early warning results, the part below the bottom of the pipeline is excavated within a safety threshold value, and a pouring bearing platform is constructed; after the bearing platform is poured, the protection device is dismantled; and backfilling the foundation pit layer by layer.

Description

Technical Field

[0001] This invention belongs to the field of subway construction technology, and more specifically, relates to a method and device for protecting construction piers next to existing pipelines. Background Technology

[0002] During the deep underground construction of subway projects, systematically protecting the existing intricate network of underground pipelines is not only a technical challenge but also a crucial task in safeguarding the city's lifeline. Urban underground space, as densely packed as its surface urban landscape, is filled with a network of pipelines delivering critical functions such as electricity, communications, water, gas, and drainage; these pipelines are the absolute core for maintaining the city's economic pulse, social order, and the normal functioning of residents' daily lives. Any pipeline damage caused by construction can trigger a catastrophic chain reaction: widespread power or communication outages will severely impact business activities and financial services; burst water pipes will cause traffic paralysis and water waste; and damage to gas pipelines could even lead to serious safety accidents.

[0003] The relocation of some affected pipelines presents the following problems: (1) The relocation process is complex, time-consuming, and requires a large amount of coordination work, which has a significant impact on the project schedule; (2) The relocation costs are high, affecting the overall project cost; (3) The pipeline relocation and on-site construction are carried out simultaneously, resulting in many overlapping work areas and a high safety risk.

[0004] Therefore, there is an urgent need for a method of constructing a protective platform next to existing pipelines, which can provide suspended protection for existing pipelines without affecting construction, avoid pipeline relocation, and greatly shorten the construction period of underground projects. Summary of the Invention

[0005] In view of the problems of complex construction, high cost and high risk in the relocation of pipelines in existing subway projects, the present invention provides a method and device for protecting the construction platform next to existing pipelines to solve these problems.

[0006] To achieve the above objectives, the present invention provides a method for protecting the construction cap next to existing pipelines, comprising the following steps: S100: Conduct a detailed survey and assessment of pipelines in the construction area; simulate and verify the construction plan based on the survey and assessment results, and construct an initial digital model of the construction area; S200: Excavate the foundation pit in layers according to the design elevation, and use steel casing for foundation pit support; S300: Clean the ground surface for main beam installation and pour concrete layer; S400: Install protective devices and install the main beam on the corresponding concrete layer; install secondary beams vertically on the main beams, and install support beams at the bottom of the pipeline according to the layout of the secondary beams; S500: Install monitoring components to monitor pipeline displacement and stress of protective device components in real time, and integrate the real-time monitoring data with the initial digital model to construct a dynamically calibrated digital twin model for forward-looking risk prediction and proactive early warning of subsequent construction steps; S600: Based on the results of the aforementioned forward-looking risk prediction and proactive early warning, within the safety threshold, excavate the portion below the bottom of the pipeline and construct the foundation. S700: After the foundation is poured, the protective device is removed; S800: Layered backfilling of foundation pit; installation of pipeline warning signs; regular monitoring of soil settlement; grouting reinforcement when settlement exceeds 10mm.

[0007] Furthermore, in step S100, the detailed survey and evaluation of pipelines in the construction area includes the following steps: S101: Using a combination of ground-penetrating radar and manual exploration pits, we conducted a detailed survey of existing pipelines and drew up a precise distribution map of their locations. S102: Assess the pipeline's operational status based on the survey results.

[0008] Further, in step S100, constructing the initial digital model includes the following steps: S103: Utilize BIM technology to construct a three-dimensional model that includes existing pipelines, foundations, protective devices, and the surrounding environment; S104: Perform structural mechanics calculations and analysis on the protection device, simulate the stress and strain distribution of each component of the device and the displacement of the pipeline under different working conditions, verify whether the structural strength and stiffness of the device meet the design requirements, and use the structural mechanics calculation model as the basis of the initial digital model.

[0009] Further, in step S400, the installation of the protection device includes the following steps: S401: Install two main beams on the top of the steel casing, parallel to the pipeline direction, to ensure that the installation position matches the relative distance between the foundation and the pipeline as marked in the survey. S402: Install secondary beams on top of the main beam in a direction perpendicular to the main beam, and adjust the installation spacing of the secondary beams according to the type and density of pipelines. S403: Install support beams at the bottom of the pipeline according to the secondary beam layout, use high-strength tie rods to connect the secondary beams and support beams, and use a level to adjust the levelness of the support beams.

[0010] Further, in step S500, the installation of the monitoring component for pipeline displacement and stress on the protective device components includes the following steps: S501: Install displacement sensors and stress sensors, and map the physical positions of the sensors to the nodes in the initial digital model using spatial coordinates; S502: Compare the real-time monitoring data obtained in step S501 with the simulation output value of the initial digital model, and automatically calibrate the key parameter vector P of the model through the inversion analysis algorithm to minimize the error between the simulation value and the real monitoring value, thereby obtaining the dynamically calibrated digital twin model. S503: Before performing the excavation in step S600, convert the excavation action into an incremental load vector. And based on the dynamically calibrated digital twin model The predicted displacement and stress values ​​that will result from the excavation are calculated in advance. ; S504: The predicted value The system compares the data with preset multi-level safety thresholds and automatically generates proactive control commands such as "allow construction," "decelerate construction," or "stop immediately" to guide the execution of step S600.

[0011] Furthermore, in step S502, the dynamic calibration is implemented in the following ways: Define an objective function Its form is:

[0012] in, This is the optimal state estimate of the real-time monitoring data. These are the simulation output values ​​of the structural mechanics model. This is a vector of parameters to be calibrated, including soil elastic modulus and contact stiffness. The observation matrix; And solve iterative optimization algorithms such as gradient descent or Gauss-Newton method. To obtain the optimal calibration parameters.

[0013] Furthermore, in step S503, the forward-looking prediction is implemented in the following ways: Solve the incremental finite element equations:

[0014] in, The global stiffness matrix is ​​updated using the optimal calibration parameters. This is the incremental load vector for the excavation action. The predicted displacement and stress increments; And calculate the final predicted value .

[0015] Further, in step S800, the layered backfilling of the foundation pit includes the following steps: S801: Graded sand and gravel are used for backfilling in layers up to the bottom of the pipeline, with each layer having a thickness of ≤300mm, and compaction is carried out using a vibrator; S802: The remaining part of the foundation pit is backfilled with the original soil in layers and compacted. The degree of compaction is adjusted according to the requirements of the surrounding environment.

[0016] According to another aspect of the present invention, a protective device for a construction pier next to an existing pipeline is also provided, comprising two sets of main beams arranged parallel to the top of a steel casing, the main beams being arranged along the pipeline direction; multiple sets of secondary beams spaced apart on the top of the main beams, the secondary beams being arranged perpendicular to the main beams; a support beam for supporting the bottom of the pipeline; and a tie rod for connecting and fixing the corresponding support beams and secondary beams at both ends respectively. The top of the support beam is fixed with an arc-shaped support plate to support the rigid pipeline. The arc of the support plate is adapted to the outer diameter of the pipeline, and a rubber buffer pad is provided on its arc-shaped part. The protection device is also equipped with a monitoring component to monitor pipeline displacement and settlement. This monitoring component includes displacement sensors and stress sensors; the displacement sensors are respectively installed on the supporting beams and the main beam; the stress sensors are installed on the stress-bearing nodes of the device. Furthermore, a flexible support pad is laid on top of the support beam to support the flexible pipeline, and the distance between adjacent support beams is ≤1m.

[0017] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The protection operation method of the present invention does not require relocation of existing pipelines. It directly achieves in-situ protection of pipelines through the support beam and tie rod suspension system. With the help of displacement sensors and stress monitoring modules, the displacement and stress status of pipelines are monitored in real time, which avoids accidental contact during construction, pipeline deformation or damage from the source and ensures the stable operation of the city's lifeline.

[0018] 2. The protection operation method of the present invention optimizes the construction process and reduces process conflicts through BIM simulation in the early stage. Layered control is adopted in the excavation stage to avoid over-excavation and rework. The device installation does not require complicated processes, the core components can be quickly assembled, and the coordination and construction time for pipeline relocation are eliminated, which greatly shortens the overall construction period of underground projects.

[0019] 3. The protective operation method of the present invention uses common construction materials such as I-beams and high-strength bolts as the core materials of the device, which can be sourced locally and have low procurement costs; the device can be reused after dismantling, testing and repair, reducing material waste; at the same time, it saves the high cost of pipeline relocation, and the overall project cost is controllable, making it suitable for large-scale promotion.

[0020] 4. The protection operation method of the present invention can be adjusted according to different geological conditions, adapt to rigid pipelines and flexible pipelines, and the component parameters can be adjusted as needed to meet diverse construction needs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a protective device for a construction foundation next to an existing pipeline, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the process steps for a protection operation method for a construction pier next to an existing pipeline, according to an embodiment of the present invention.

[0022] In all the accompanying drawings, the same reference numerals indicate the same technical features, specifically: 1-proposed foundation, 2-existing pipeline, 3-steel casing, 4-main beam, 5-secondary beam, 6-tie rod, 7-support beam. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] like Figure 1-2 As shown, the present invention provides a method for protecting the construction cap next to existing pipelines, comprising the following steps: S100: Conduct a detailed survey and assessment of pipelines in the construction area; simulate and verify the construction plan based on the survey and assessment results, and construct an initial digital model of the construction area; S200: Excavate the foundation pit in layers according to the design elevation, and use steel casing for foundation pit support; S300: Clean the ground surface for main beam installation and pour concrete layer; S400: Install protective devices and install the main beam on the corresponding concrete layer; install secondary beams vertically on the main beams, and install support beams at the bottom of the pipeline according to the layout of the secondary beams; S500: Install monitoring components to monitor pipeline displacement and stress of protective device components in real time, and integrate the real-time monitoring data with the initial digital model to construct a dynamically calibrated digital twin model for forward-looking risk prediction and proactive early warning of subsequent construction steps; S600: Based on the results of the aforementioned forward-looking risk prediction and proactive early warning, within the safety threshold, excavate the portion below the bottom of the pipeline and construct the foundation. S700: After the foundation is poured, the protective device is removed; S800: Layered backfilling of foundation pit; installation of pipeline warning signs; regular monitoring of soil settlement; grouting reinforcement when settlement exceeds 10mm.

[0025] In step S100, the detailed survey and evaluation of pipelines in the construction area includes the following steps: S101: Using a combination of ground-penetrating radar and manual exploration pits, we conducted a detailed survey of existing pipelines and drew up a precise distribution map of their locations. S102: Assess the pipeline's operational status based on the survey results.

[0026] In step S101, the ground-penetrating radar used has a detection depth of ≥5m and a resolution of ≤5cm. Combined with artificial pits, it conducts a detailed survey of the location, direction, diameter, material, burial depth of existing pipelines and the properties of the surrounding soil (soil type, moisture content, compaction degree), thereby drawing a precise distribution map of the pipeline location and marking key parameters such as the relative distance and angle between the pipeline and the proposed construction pier, so as to avoid accidentally touching the pipeline during construction due to unclear survey.

[0027] In step S102, the pipeline's operational status is assessed, including using specialized equipment to detect the pressure and flow rate of the medium within the pipeline (for water and gas pipes) or signal strength (for communication lines and cables) to determine if there are any issues such as leaks, damage, or aging. If potential hazards are found, relevant units are coordinated to carry out repairs or reinforcement before proceeding with the foundation construction and equipment installation to prevent the pipeline fault from escalating during construction.

[0028] In step S100, constructing the initial digital model includes the following steps: S103: Utilize BIM technology to construct a three-dimensional model that includes existing pipelines, foundations, protective devices, and the surrounding environment; S104: Perform structural mechanics calculations and analysis on the protection device, simulate the stress and strain distribution of each component of the device and the displacement of the pipeline under different working conditions, verify whether the structural strength and stiffness of the device meet the design requirements, and use the structural mechanics calculation model as the basis of the initial digital model.

[0029] In step S103, a three-dimensional model is constructed to visualize and simulate the installation process of the device, the excavation sequence of the foundation, and the pipeline protection process. This allows for the checking of whether the connection between each process is smooth and whether there are any conflicts in the spatial positions of the device components, pipelines, and foundation. It also helps to identify and adjust any unreasonable aspects of the construction plan in advance.

[0030] In step S104, structural mechanics calculations and analyses are performed on the protective device. If the calculation results show that the stress of the components exceeds the allowable value or the pipeline displacement is too large, the component parameters are adjusted in a timely manner (such as increasing the cross-sectional size of the main beam and increasing the spacing of the secondary beams) or the device structure is optimized (such as adding auxiliary support components) to ensure the safety and reliability of the device.

[0031] In this embodiment of the invention, when excavating the foundation pit in layers in step S200, the foundation pit is excavated in 3-5 layers, with each layer having an excavation depth of ≤1.5m, to avoid the collapse of the foundation pit sidewalls due to excessive excavation depth at one time; during the excavation process, a total station is used to monitor the foundation pit excavation elevation in real time to ensure accurate control when excavating to the top elevation of the pipeline, and to prevent over-excavation from damaging the pipeline; When carrying out foundation pit support, positioning benchmark piles are first set around the perimeter of the foundation pit. The verticality (verticality deviation ≤ 1‰) and position (planar position deviation ≤ 50mm) of the steel casing are calibrated using the benchmark piles. The steel casings are connected and fixed together using connecting plates (material consistent with the steel casings, thickness ≥ 8mm). The connecting plates are welded to the steel casings (weld height ≥ 6mm, weld quality grade up to level two) to enhance the overall stability of the foundation pit support structure.

[0032] In this embodiment of the invention, during the concrete pouring operation in step S300, the ground surface is first cleaned to remove loose soil and debris. If the surface soil moisture content is too high (moisture content > 25%), quicklime (3%-5% of the soil mass) is added to the soil for drying and mixing to reduce the soil moisture content and improve the bearing capacity of the foundation. During the plain concrete pouring process, an immersion vibrator (vibration frequency ≥ 2000 r / min) is used for layered vibration, with the vibration time controlled at 20-30 seconds per layer to ensure concrete density (density ≥ 95%) and avoid settlement after the main beam is installed due to insufficient concrete density. After the plain concrete is poured, concrete test blocks are made according to the specifications. They are cured for 28 days under standard curing conditions (temperature 20±2℃, relative humidity ≥95%). The compressive strength of the test blocks is tested using a pressure testing machine. The main beam can only be installed when the compressive strength of the test blocks reaches 100% of the design strength (design strength grade not lower than C20). Construction is strictly prohibited before the concrete strength meets the standard to prevent the ground surface from collapsing after the main beam is installed.

[0033] In step S400, the installation of the protection device includes the following steps: S401: Install two main beams on the top of the steel casing, parallel to the pipeline direction, to ensure that the installation position matches the relative distance between the foundation and the pipeline as marked in the survey. S402: Install secondary beams on top of the main beam in a direction perpendicular to the main beam, and adjust the installation spacing of the secondary beams according to the type and density of pipelines. S403: Install support beams at the bottom of the pipeline according to the secondary beam layout, use high-strength tie rods to connect the secondary beams and support beams, and use a level to adjust the levelness of the support beams.

[0034] In step S403, when installing support beams for rigid pipelines (such as cast iron pipes, steel water pipes, and gas pipes), an arc-shaped support plate with a rubber buffer layer is fixed at the top to increase the contact area between the support beam and the pipeline, reducing local pressure (contact pressure ≤ 0.5 MPa) and preventing the rigid pipeline from cracking due to excessive local stress. Simultaneously, limit baffles (height ≥ 1 / 3 pipeline diameter, thickness ≥ 5 mm) are installed on both sides of the support plate to prevent the pipeline from sliding horizontally. Pressure sensors (measuring range 0-2 MPa, accuracy ±0.01 MPa) are installed at the pipeline valves to monitor changes in the pressure of the medium inside the pipeline in real time. If the pipeline is squeezed during the foundation construction due to earthwork excavation or equipment installation, and the pressure sensor detects an abnormal increase (exceeding 10% of the normal operating pressure) or decrease (below 5% of the normal operating pressure), construction should be stopped immediately. The pipeline should be checked for deformation or leakage, and pressure relief and repair measures should be taken promptly to prevent pipeline rupture and potential safety accidents.

[0035] When installing support beams for flexible pipelines (such as PE water pipes, communication optical cables, and electrical cables), a multi-point uniform support method should be adopted, with the distance between support beams ≤1m. Flexible support pads (made of sponge, thickness ≥10mm, density ≥30kg / m³) should be laid on the support beams to prevent local sagging of the flexible pipelines due to insufficient support points (the sagging amount of the pipeline should be ≤20mm). Preferably, for communication optical cables and electrical cables, cable trays (the width of the tray is determined according to the number of pipelines, generally ≥200mm, made of galvanized steel plate) should be installed on the support beams to place the pipelines in an orderly manner inside the trays to prevent the pipelines from tangling or being squeezed. For electrical cable pipelines, insulating tape (tape thickness ≥0.5mm, insulation resistance ≥100MΩ) should be wrapped around the contact points between the support beams and the cables to prevent electrical contact between the support beams (metal material) and the cables, and to prevent leakage accidents caused by damage to the cable insulation layer. Meanwhile, a rain cover (made of PVC board, thickness ≥2mm) is installed on the outside of the device to prevent rainwater and dew from soaking the flexible pipeline, which would cause the pipeline to age and corrode, affecting its service life.

[0036] In step S500, the installation of the monitoring component for pipeline displacement and stress on the protective device components includes the following steps: S501: Install displacement sensors and stress sensors, and map the physical positions of the sensors to the nodes in the initial digital model using spatial coordinates; S502: Compare the real-time monitoring data obtained in step S501 with the simulation output value of the initial digital model, and automatically calibrate the key parameter vector P of the model through the inversion analysis algorithm to minimize the error between the simulation value and the real monitoring value, thereby obtaining the dynamically calibrated digital twin model. S503: Before performing the excavation in step S600, convert the excavation action into an incremental load vector. And based on the dynamically calibrated digital twin model The predicted displacement and stress values ​​that will result from the excavation are calculated in advance. ; S504: The predicted value The system compares the data with preset multi-level safety thresholds and automatically generates proactive control commands such as "allow construction," "decelerate construction," or "stop immediately" to guide the execution of step S600.

[0037] In step S501, when installing displacement sensors and stress sensors, displacement sensors are installed on the support beam and main beam respectively to detect whether the pipeline of the device has horizontal displacement and vertical settlement; stress plates are installed on key stress nodes of the device, such as the connection between the main beam and the steel casing, the vertical connection between the secondary beam and the main beam, the connection of the tie rod, and the support section where the support beam contacts the pipeline, to promptly check for problems such as component deformation and pipeline load shift.

[0038] In step S502, the dynamic calibration is implemented in the following ways: Define an objective function Its form is:

[0039] in, This is the optimal state estimate of the real-time monitoring data. These are the simulation output values ​​of the structural mechanics model. This is a vector of parameters to be calibrated, including soil elastic modulus and contact stiffness. The observation matrix; And solve iterative optimization algorithms such as gradient descent or Gauss-Newton method. To obtain the optimal calibration parameters.

[0040] In step S503, the forward-looking prediction is implemented in the following ways: Solve the incremental finite element equations:

[0041] in, The global stiffness matrix is ​​updated using the optimal calibration parameters. This is the incremental load vector for the excavation action. The predicted displacement and stress increments; And calculate the final predicted value .

[0042] In step S700, the removal of the protective device includes the following steps: The device is removed according to the principles of auxiliary components first, then core components; top to bottom; and outside to inside. The specific order is: tie rod → support beam → secondary beam → main beam → steel casing. During the removal process, unauthorized operations (such as premature removal of core load-bearing components or rough removal) are strictly prohibited to prevent device collapse or pipeline fall. When removing tie rods, support beams, and other components in direct contact with the pipeline, the pipeline displacement is continuously monitored using displacement sensors. Each time a tie rod or section of support beam is removed, the pipeline displacement data is recorded. If the displacement exceeds the allowable value, the removal work is immediately stopped, and temporary support measures (such as placing timber or steel blocks under the pipeline) are taken to fix the pipeline. An adjusted removal plan is then formulated after the pipeline has stabilized.

[0043] In step S800, the layered backfilling of the foundation pit includes the following steps: S801: Graded sand and gravel are used for backfilling in layers up to the bottom of the pipeline, with each layer having a thickness of ≤300mm, and compaction is carried out using a vibrator; S802: The remaining part of the foundation pit is backfilled with the original soil in layers and compacted. The degree of compaction is adjusted according to the requirements of the surrounding environment.

[0044] After backfilling is completed, warning signs should be set up above the pipeline to indicate its location, direction, diameter, and other information to prevent accidental excavation of the pipeline during subsequent construction. At the same time, the soil settlement around the pipeline should be monitored regularly (once a day for the first week after backfilling, once every three days thereafter, once a week after one month, and continuously monitored for three months). If the soil settlement exceeds 10 mm, grouting (cement grout with a water-cement ratio of 1:1.5) should be used to reinforce the settlement area in a timely manner to prevent the pipeline from being damaged by soil settlement.

[0045] The present invention also provides a protective device for a construction pier next to an existing pipeline, comprising two sets of main beams arranged parallel to the top of a steel casing, the main beams being arranged along the pipeline direction; multiple sets of secondary beams spaced apart on the top of the main beams, the secondary beams being arranged perpendicular to the main beams; a support beam for supporting the bottom of the pipeline; and a tie rod connecting and fixing the corresponding support beams and secondary beams at both ends.

[0046] The protection device is also equipped with a monitoring component to monitor pipeline displacement and settlement. The monitoring component includes a displacement sensor and a stress sensor. The displacement sensor is installed on the support beam and the main beam, respectively. The stress sensor is installed on the stress node of the device.

[0047] The protection method of this invention does not require relocation of existing pipelines. It directly achieves in-situ protection of pipelines through a support beam and tie rod suspension system. In conjunction with displacement sensors and stress monitoring modules, it monitors the displacement and stress status of pipelines in real time, thereby avoiding accidental contact during construction, pipeline deformation or damage from the source and ensuring the stable operation of the city's lifeline.

[0048] The protection operation method of the present invention optimizes the construction process and reduces process conflicts through BIM simulation in the early stage. Layered control is adopted in the excavation stage to avoid over-excavation and rework. The device installation does not require complicated processes, the core components can be quickly assembled, and the coordination and construction time for pipeline relocation are eliminated, which greatly shortens the overall construction period of underground projects.

[0049] The protective operation method of the present invention uses common construction materials such as I-beams and high-strength bolts as the core materials of the device, which can be sourced locally and have low procurement costs. After the device is dismantled, it can be reused after inspection and repair, reducing material waste. At the same time, it saves the high cost of pipeline relocation, and the overall project cost is controllable, making it suitable for large-scale promotion.

[0050] The protection operation method of the present invention can be adjusted according to different geological conditions, adapt to rigid pipelines and flexible pipelines, and the component parameters can be adjusted as needed to meet diverse construction requirements.

[0051] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for protecting a construction work of a pile cap beside an existing pipeline, characterized by, Comprise the following steps: S100: detailed investigation and evaluation of the pipeline in the construction area; according to the investigation and evaluation results, construction scheme simulation and verification are carried out, and the initial digital model of the construction area is constructed; S200: excavate the pile cap foundation pit according to the design elevation, and use the steel casing to support the foundation pit; S300: clean the ground surface of the main beam installation, and pour the concrete layer; S400: install the protection device, install the main beam on the corresponding concrete layer; install the secondary beam vertically on the main beam, and install the joist at the bottom of the pipeline according to the secondary beam layout; S500: install the monitoring assembly to monitor the pipeline displacement and the stress of the protection device component in real time, and fuse the real-time monitoring data with the initial digital model to construct a dynamically calibrated digital twin model for prospective risk prediction and active early warning of subsequent construction steps; S600: according to the results of the prospective risk prediction and active early warning, excavate the part below the pipeline bottom within the safety threshold, and construct and pour the pile cap; S700: after the pile cap is poured, the protection device is removed; S800: backfill the foundation pit in layers; Set up pipeline warning signs, regularly observe soil settlement, and grout and reinforce when the settlement exceeds 10mm.

2. The method for protecting the construction of a pile cap alongside an existing pipeline according to claim 1, characterized in that, In step S100, the detailed investigation and evaluation of the pipeline in the construction area comprises the following steps: S101: adopt the combination of geological radar and manual exploration to investigate the existing pipeline in detail, and draw the accurate distribution map of the pipeline position; S102: according to the investigation results, evaluate the operation state of the pipeline.

3. The method of claim 2, wherein the method further comprises: In step S100, the initial digital model is constructed, comprising the following steps: S103: use BIM technology to construct a three-dimensional model including existing pipelines, pile caps, protection devices and surrounding environment; S104: perform structural mechanics calculation and analysis on the protection device, simulate the stress, strain distribution of each component of the device under different working conditions and the displacement of the pipeline, verify whether the structural strength and stiffness of the device meet the design requirements, and take the structural mechanics calculation model as the basis of the initial digital model.

4. The method for protecting the construction of a pile cap beside an existing pipeline according to any one of claims 1-3, characterized in that, In step S400, the installation of the protection device comprises the following steps: S401: install two main beams on the top of the steel casing in parallel to the pipeline direction to ensure that the installation position matches the relative distance of the pile cap and the pipeline marked by the investigation; S402: install the secondary beam on the top of the main beam in the direction perpendicular to the main beam, and adjust the installation spacing of the secondary beam according to the type and density of the pipeline; S403: install the joist at the bottom of the pipeline according to the secondary beam layout, connect the secondary beam and the joist with high-strength tie rods, and use the level to control the levelness of the joist.

5. The method for protecting the construction of a pile cap beside an existing pipeline according to any one of claims 1-3, characterized in that, In step S500, the installation of the monitoring assembly for pipeline displacement and protection device component stress comprises the following steps: S501: install displacement sensors and stress sensors, and map the physical position of the sensors to the node in the initial digital model. S502: comparing the real-time monitoring data obtained in step S501 with the simulation output value of the initial digital model, and automatically calibrating the key parameter vector P of the model by an inversion analysis algorithm to minimize the error between the simulation value and the real monitoring value, so as to obtain the dynamically calibrated digital twin model; S503: before performing the step S600 of excavation, convert the excavation action into an incremental load vector , and based on the dynamically calibrated digital twin model , calculate in advance the predicted values of displacement and stress caused by the upcoming excavation ; S504: compare the predicted value with the preset multi-level safety threshold, and automatically generate the active control instruction of "allow construction", "slow down construction" or "stop immediately" according to the comparison to guide the execution of step S600.

6. The method of claim 5, wherein the method further comprises: In the step S502, the implementation mode of the dynamic calibration comprises: defining an objective function in the form of: wherein, is an optimal state estimation value of the real-time monitoring data, is a simulation output value of the structural mechanics model, is a vector of parameters to be calibrated including soil elastic modulus and contact stiffness, is an observation matrix; And through the gradient descent method or Gauss-Newton method and other iterative optimization algorithm, solve To get the optimal calibration parameters.

7. The method of claim 5, wherein the method further comprises: In the step S503, the implementation mode of the forward prediction comprises: Solving the incremental finite element equation: wherein, is the updated global stiffness matrix using the optimal calibration parameters, is the incremental load vector of the excavation action, is the predicted displacement and stress increment; and calculating the final prediction value .

8. The method for protecting the construction of a pile cap beside an existing pipeline according to any one of claims 1-3, characterized in that, In step S800, the layered backfill foundation pit comprises the following steps: S801: graded sand is used for layered backfill to the pipeline bottom, the thickness of each layer is ≤300mm, and a vibrator is used for compaction; S802: original soil is used for layered backfill to the rest of the foundation pit, and compaction is performed, and the compaction degree is adjusted according to the requirements of the surrounding environment.

9. A protection device for a construction platform beside an existing pipeline, characterized in that Two groups of main beams are arranged in parallel on the top of the steel casing, the main beams are arranged along the pipeline direction; a plurality of groups of secondary beams are arranged at intervals on the top of the main beams, the arrangement direction of the secondary beams is perpendicular to the main beams; the support beams support the pipeline bottom; And the pull rods respectively connect and fix the corresponding support beams and secondary beams at both ends; An arc-shaped support plate is fixedly arranged on the top of the support beam to support the rigid pipeline, the arc of the arc-shaped support plate is matched with the outer diameter of the pipeline, and a rubber buffer layer is arranged on the arc-shaped part of the arc-shaped support plate; A monitoring assembly is further arranged on the protection device to monitor the displacement and settlement of the pipeline, the monitoring assembly comprises a displacement sensor and a stress sensor; the displacement sensor is respectively installed on the support beam and the main beam; the stress sensor is installed on the stress node of the device.

10. A protection device for a construction platform alongside an existing pipeline according to claim 9, characterized in that A flexible support pad is arranged on the top of the support beam to support the flexible pipeline, and the distance between adjacent support beams is ≤1m.

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