Foundation pit supporting and intelligent cooperative monitoring method close to subway protection area

Abstract

The invention discloses a supporting and intelligent cooperative monitoring method for a foundation pit close to a subway protection area, which adopts a pile-anchor supporting system optimized according to the strict deformation control requirement of the subway protection area, and comprises the following steps: constructing a row of large-diameter and small-spacing cast-in-place piles on the side of the foundation pit close to the subway as vertical supporting members, hanging a net between the piles, and spraying concrete to form a soil retaining surface; a plurality of high-strength pre-stressed anchor cables are arranged at different elevations of a pile body, and active constraint is applied to the supporting pile and a soil body behind the supporting pile; a top beam is arranged at the tops of the support piles to form an integral stress structure; a deformation monitoring module, a vibration monitoring module, an underground water monitoring module and an environment monitoring module are adopted, and integration, visualization and linkage analysis are performed on data of the monitoring modules through a three-dimensional collaborative management platform constructed based on a BIM technology; a safety threshold value and an early warning threshold value of each monitoring index are preset in the management platform, and when the safety threshold value and the early warning threshold value reach or exceed the early warning threshold value, a graded early warning signal is triggered to form closed-loop management and control of'monitoring-early warning-response '.

Description

Technical Field

[0001] This invention relates to the field of foundation pit construction safety technology, specifically to an optimized design of foundation pit support structure for adjacent subway protection zones and a method for intelligent collaborative monitoring, early warning and response throughout the entire process. Background Technology

[0002] With the continuous improvement of urban rail transit networks, the number of construction pit projects near subway lines and subway protection zones is increasing. These projects are extremely sensitive to safety issues. Subway protection zones have set very strict control standards for indicators such as surrounding soil deformation, construction vibration, and groundwater disturbance. Exceeding these thresholds will directly threaten the structural safety and normal operation of the subway.

[0003] Existing technologies have significant shortcomings in this type of engineering:

[0004] Firstly, the stiffness design and prestressing configuration of traditional support structures (such as conventional pile anchors and soil nailing walls) lack specificity, and the deformation control accuracy is limited, making it difficult to meet the stringent deformation restriction requirements of subway protection zones and easily posing potential safety hazards to subway structures.

[0005] Secondly, risk monitoring during construction relies on intermittent manual data collection, which results in a single monitoring dimension and strong data lag, making it impossible to achieve real-time collaborative perception of multiple risk factors such as structural deformation, mechanical vibration, and changes in soil and water pressure.

[0006] Third, the monitoring data is scattered and isolated, lacking an effective integrated analysis and visualization platform, making it difficult to build a multi-dimensional data fusion risk early warning system, resulting in passive risk identification and handling.

[0007] Fourth, the design of the support system did not fully consider the spatial interaction with the subway protection zone, lacked a quantifiable and integrated protection and monitoring solution, and could not form a closed-loop management system for the entire process.

[0008] Therefore, there is an urgent need for an integrated technical solution that combines targeted support capabilities with intelligent monitoring and early warning functions to address core issues such as insufficient deformation control, lagging risk monitoring, and low management efficiency in the construction of foundation pits near subway protection zones. Summary of the Invention

[0009] To address the shortcomings of the aforementioned background technologies, this invention proposes a method for foundation pit support and intelligent collaborative monitoring near subway protection zones. This method aims to solve the problems of existing technologies in foundation pit construction near subway protection zones, such as insufficient deformation control accuracy of conventional support structures to meet stringent deformation limits, lack of systematic real-time collaborative monitoring of multi-source risk factors leading to delayed risk identification, scattered and isolated monitoring data preventing the construction of a multi-dimensional data fusion risk warning and decision support system, insufficient consideration of the spatial relationship and interaction between the support system and the subway protection zone, and a lack of targeted, quantifiable, integrated protection and monitoring solutions.

[0010] The technical solution of this invention is as follows:

[0011] (I) Core technical solution and beneficial effects of the present invention

[0012] Core technical solution: This invention provides a method for foundation pit support and intelligent collaborative monitoring near subway protection zones, including three core links: support structure design and construction, intelligent monitoring system deployment and operation, and processing and early warning response based on real-time monitoring data.

[0013] Support structure design and construction: A pile-anchor support system optimized for the strict deformation control requirements of the subway protection zone is adopted. This includes constructing a row of large-diameter, small-spacing cast-in-place piles as vertical support components on the side of the foundation pit facing the subway, with mesh and shotcrete between the piles to form a retaining surface; setting multiple high-strength prestressed anchor cables at different elevations of the piles to actively restrain the support piles and the soil behind them; and setting a cap beam at the top of the support piles to form an integral load-bearing structure.

[0014] The deployment and operation of the intelligent monitoring system involves constructing a multi-dimensional collaborative monitoring network covering deformation, dynamics, soil and water conservation, and the environment, including deformation monitoring modules, vibration monitoring modules, groundwater monitoring modules, and environmental monitoring modules. Data from each monitoring module is integrated, visualized, and analyzed in a coordinated manner through a three-dimensional collaborative management platform built on BIM technology.

[0015] Data processing and early warning response: Safety thresholds and early warning thresholds for each monitoring indicator are preset in the management platform. After the monitoring data is transmitted to the platform in real time, it is automatically compared and analyzed. When the early warning threshold is reached or exceeded, a graded early warning signal is triggered, and a preset emergency response procedure is initiated according to the early warning level, forming a closed-loop control of "monitoring-early warning-response".

[0016] Beneficial effects: By deeply integrating the targeted and optimized pile-anchor support structure with the multi-dimensional intelligent monitoring system, soil deformation is controlled from the source, and real-time perception and accurate early warning of construction risks are achieved. This solves the problems of insufficient support deformation control, lagging monitoring, and passive management in traditional technologies, significantly improving the safety and management efficiency of foundation pit construction near the subway protection zone, and ensuring the dual safety of subway operation and foundation pit construction.

[0017] (II) Based on the above core technical solutions, the preferred technical solutions and their beneficial effects

[0018] Preferred technical solution one: The pile diameter is 1000mm, the pile length is 20m, and the center-to-center distance between piles is 1.2m; the main reinforcement of the pile body uses 21 HRB-400E Φ20 steel bars, the stirrups are Φ12@150, and the concrete strength grade is C30; 100mm thick C20 fine aggregate concrete is sprayed between the piles, reinforced with Φ6@250×250 steel mesh. Beneficial effects: By clearly defining the specific dimensions, reinforcement, and concrete parameters between the piles, a precise match between the stiffness and deformation resistance of the support structure is achieved, further improving the accuracy of soil deformation control and ensuring the stability and reliability of the support system.

[0019] Preferred technical solution two: The prestressed anchor cables are made of two steel strands with a nominal diameter of 15.2mm and a standard strength of 1860MPa, with a horizontal spacing of 2.5m and a vertical spacing of 2.0m, and an incident angle of 15-20°; the anchor cable grouting adopts a secondary pressure grouting process, with a grouting pressure of not less than 1.5MPa. Beneficial effects: By optimizing the material specifications, layout parameters, and grouting process of the anchor cables, the effective transfer and long-term stability of prestress are ensured, achieving active and precise constraint on the soil, and further reducing the impact of foundation pit deformation on the subway structure.

[0020] Preferred technical solution three: The deformation monitoring module includes horizontal displacement monitoring points spaced 5m apart along the top of the slope facing the subway from the foundation pit, settlement monitoring points spaced 10m apart around the subway structure and entrances / exits, and inclinometer tubes pre-embedded in the support piles; the monitoring frequency is no less than once a day during the earthwork excavation stage, and no less than twice a week during the usage stage after the support structure is completed. Beneficial effects: By clearly defining the density, location, and monitoring frequency of deformation monitoring points, comprehensive and accurate monitoring of the deformation of the foundation pit and subway structure can be achieved, ensuring the integrity and timeliness of deformation data and providing reliable data support for risk early warning.

[0021] Preferred technical solution four: The vibration monitoring module sets the vibration velocity control threshold to 0.2 cm / s; the environmental monitoring module controls construction noise at ≤70 dB during the day and ≤55 dB at night, and the dust monitoring threshold during the structural construction phase is PM10 concentration ≤0.5 mg / m³. Beneficial effects: By quantifying the control thresholds for key environmental and dynamic indicators such as vibration, noise, and dust, the impact of the construction process on subway operation and the surrounding environment is ensured to be controlled within permissible limits, improving the environmental friendliness and compliance of the construction.

[0022] Preferred technical solution five: A BIM-based 3D collaborative management platform further integrates project progress management data, enabling linked analysis of construction progress and safety monitoring data; and connects to a large-volume concrete wireless temperature measurement system to monitor the temperature field of the support structure and surrounding soil in real time. Beneficial effects: By expanding the integration functions of the BIM platform, collaborative management of construction progress and safety monitoring is achieved. Simultaneously, the addition of a temperature field monitoring dimension further improves the multi-source data fusion analysis system, enhancing the comprehensiveness and accuracy of risk prediction.

[0023] Preferred technical solution six: A tiered early warning mechanism includes three levels: yellow, orange, and red. Early warning information is automatically pushed to relevant responsible persons via pop-up windows on the management platform interface and SMS messages. When a red warning is triggered, the system prompts and requires the immediate execution of emergency instructions to stop construction, initiate prestressing compensation, or add temporary supports. Beneficial effects: By clearly defining the early warning level classification, information push methods, and specific emergency measures for red warnings, the system ensures rapid delivery of early warning information and accurate and efficient emergency response, minimizing safety risks.

[0024] Preferred technical solution seven: The capping beam has a cross-sectional dimension of 600mm × 800mm, and is integrally cast with the top of the support piles, with the main reinforcement of the support piles effectively anchored to the capping beam. Beneficial effects: By optimizing the structural dimensions and connection method of the capping beam, a rigid top constraint is formed, improving the pile-beam collaborative stress performance, further enhancing the overall stiffness and stability of the support system, and suppressing top deformation.

[0025] Preferred technical solution eight: The intelligent monitoring system adopts automated monitoring equipment and a wireless transmission network, with a data acquisition delay of ≤30s. Beneficial effects: By employing automated equipment and high-speed wireless transmission technology, monitoring data can be acquired and uploaded in seconds, completely solving the data lag problem of traditional manual monitoring and providing technical support for real-time early warning and rapid response.

[0026] Preferred technical solution nine: When an orange alert is triggered, implement emergency measures such as increased monitoring frequency and partial work stoppage. Beneficial effects: Clearly define the specific emergency response measures for an orange alert, forming a complete tiered response system to ensure that different levels of risk can be accurately addressed, minimizing the impact on construction while ensuring safety.

[0027] (III) Overall beneficial effects of the present invention

[0028] This invention achieves the following core beneficial effects through a closed-loop management system of "targeted support structure + multi-dimensional intelligent monitoring + hierarchical early warning response":

[0029] The support structure is highly targeted: the optimized pile-anchor support system (large-diameter cast-in-place piles, high-strength prestressed anchor cables, and rigid cap beams) is precisely matched to the deformation control requirements of the subway protection zone, effectively suppressing soil deformation and reducing disturbance to the subway structure;

[0030] High level of intelligent monitoring: Construct a multi-dimensional collaborative monitoring network covering deformation, vibration, soil and water, and environment, and combine BIM visualization platform with automated data acquisition and transmission technology to realize real-time risk perception and integrated data analysis;

[0031] Precise and efficient risk management: By setting up quantitative thresholds and a tiered early warning mechanism, the risk level can be accurately identified and early warning information can be quickly pushed out. Combined with the tiered emergency response plan, a closed-loop management of "monitoring-early warning-decision-response" is formed to improve the efficiency of risk handling.

[0032] Improved construction safety and compliance: The impact of foundation pit construction on subway operation and the surrounding environment is controlled within the allowable range, which not only ensures the safety of construction and subway operation, but also meets environmental protection and compliance requirements, and has significant engineering application value. Attached Figure Description

[0033] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart of the overall construction process for the support structure;

[0035] Figure 2 Anchor cable construction flowchart;

[0036] Figure 3 This is a block diagram illustrating the principle of an intelligent monitoring system.

[0037] Figure 4 Here are the principle block diagrams for each monitoring module;

[0038] Figure 5 This is a logic block diagram for the early warning response. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the core concept of the present invention and the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] I. General Implementation Examples (Complete Engineering Application Examples)

[0041] A method for foundation pit support and intelligent collaborative monitoring near subway protection zones, such as Figures 1 to 5 As shown:

[0042] (I) Project Overview

[0043] This embodiment is applied to a residential project (section 1). The project is located in a high-tech zone of a city, adjacent to the operating line of Metro Line 1 on the north side. The horizontal distance from the top of the foundation pit slope to the boundary of the 10-meter special protection zone of the metro is only 1.8m. A metro entrance (30m long × 8m wide × 4.5m high) is set within 30m on the northeast side. The excavation area of ​​the foundation pit is about 2800㎡, and the excavation depth is 9.33m (shallow zone)-12.55m (deep zone). The safety level of the foundation pit is level 1. The deformation control requirements of the metro protection zone are: horizontal displacement of the foundation pit slope ≤25mm, metro structure settlement ≤10mm, and construction vibration velocity ≤0.2cm / s.

[0044] (II) Design and Construction of Support Structure

[0045] Overall support system: The system adopts a pile-anchor support system consisting of "high-rigidity cast-in-place piles + high-strength prestressed anchor cables + rigid cap beams + shotcrete between piles". The support length on the side adjacent to the subway is 86m, with a total of 72 support piles (pile center distance 1.2m) and 3 anchor cables (vertical spacing 2.0m).

[0046] Relationship between structural parameters and assembly of retaining piles:

[0047] Structural features: 1000mm pile diameter, 20m pile length (embedded in stable rock strata ≥3m), pile center-to-center distance 1.2m; the main reinforcement of the pile body consists of 21 HRB-400EΦ20 threaded steel bars, evenly distributed around the pile (spacing approximately 140mm), the stirrups are Φ12@150 spiral stirrups, and Φ14@100 reinforcing stirrups are installed within 3m of the pile top; the concrete strength grade is C30, the slump is 180-220mm, and P.O42.5 grade ordinary Portland cement is used.

[0048] Assembly relationship: The steel cage is made in 3 sections (6-7m each), and the sections are welded with double-sided lap welding. The weld length is ≥10d (d=20mm), and the anchorage length of the main reinforcement is ≥35d (embedded in the cap beam ≥700mm). The verticality deviation of the pile hole is ≤0.5%, and the pile position deviation is ≤50mm.

[0049] Relationship between cap beam structural parameters and assembly:

[0050] Structural features: Cross-section dimensions 600mm (width) × 800mm (height), length 86m, concrete strength grade C30; main reinforcement uses 16 HRB-400EΦ25 threaded steel bars, stirrups are Φ12@200, protective layer thickness 50mm.

[0051] Assembly relationship: The top of the support pile is chiseled to the fresh concrete surface, the main reinforcement is welded and fixed to the main reinforcement of the capping beam, the capping beam formwork is steel formwork, the bearing capacity of the support system is ≥2.5 times the self-weight of the concrete, after pouring, it is covered and moisturized for ≥7 days, and earthwork excavation can only be carried out after the strength reaches 100% of the design strength.

[0052] Relationship between prestressed anchor cable structural parameters and assembly:

[0053] Structural features: It uses two low-relaxation steel strands with a nominal diameter of 15.2mm and a standard strength of 1860MPa. The horizontal spacing of the anchor cables is 2.5m, the vertical spacing is 2.0m, and the incident angle is 15° (shallow zone) - 20° (deep zone). The free section length is 4-6m, and the anchorage section length is 8-10m (adjusted according to geological conditions). The grouting material is P.O42.5 grade cement grout. The water-cement ratio for the first grouting is 0.5:1, and the water-cement ratio for the second grouting is 0.45:1.

[0054] Assembly details: Anchor cable borehole diameter 150mm, hole position deviation ≤100mm, inclination angle deviation ≤1°; steel strands are tied parallel to the grouting pipe, with guide caps at the ends, and the grouting pipe is ≥200mm from the bottom of the hole; the anchor is an OVM15-2 type wedge anchor, with the bearing surface perpendicular to the top surface of the cap beam.

[0055] Relationship between structural parameters and assembly of shotcrete between piles:

[0056] Structural features: 100mm thickness, C20 concrete strength grade, internally reinforced with Φ6@250×250 steel mesh, with an overlap length of ≥200mm.

[0057] Assembly relationship: The steel mesh is welded and fixed to the main reinforcement of the support pile (no less than 3 welding points per pile). The shotcrete adopts the dry spraying process, with a working pressure of 0.4-0.6MPa. The spraying sequence is from top to bottom, and the surface flatness deviation is ≤10mm.

[0058] (III) Deployment of Intelligent Monitoring System

[0059] BIM 3D Collaborative Management Platform: Utilizes Autodesk Revit 2023 to create 3D models of foundation pit support structures, subway structures, and monitoring points. Integrates Project progress management data (linked to Zebra Project), connects to a large-volume concrete wireless temperature measurement system, and maintains a platform data update frequency of ≤30 seconds. Supports simultaneous access via mobile APP and computer.

[0060] Deployment of deformation monitoring module:

[0061] Horizontal displacement monitoring points: 1 point is set up every 5m along the top of the slope of the foundation pit facing the subway, for a total of 18 points (numbered W1-W18). A total station TS60 is used (angle measurement accuracy ±0.5″, distance measurement accuracy ±(0.6mm+1ppm×D)). Monitoring frequency: 2 times / day during the earthwork excavation stage, and 2 times / week after the support is completed.

[0062] Settlement monitoring points: 1 point is set up every 10m around the subway track bed and entrance / exit structure, for a total of 12 points (numbered C1-C12). The electronic level DL2020 is used (the mean error of the round-trip height difference per kilometer is ±0.3mm), and the monitoring frequency is the same as that of horizontal displacement monitoring.

[0063] Deep displacement of piles: Inclinometer tubes (70mm in diameter, 5mm in wall thickness) are pre-embedded in the pile bodies of support piles No. 1, 15, 30, 45, 60, and 72. The bottom of the inclinometer tube is embedded in stable rock layer ≥1m. CX-03 inclinometer (measuring range ±30°, resolution 0.01°) is used. Monitoring frequency: once every 2 hours during earthwork excavation, and once a day after support is completed.

[0064] Vibration monitoring module deployment: Six vibration sensors (numbered Z1-Z6) are evenly deployed at the boundary between the foundation pit and the subway protection zone. VS-100 vibration sensors (measurement range 0.01-10cm / s, frequency response 1-500Hz) are used. Monitoring frequency: Real-time data acquisition during construction, data sampling rate 100Hz.

[0065] Groundwater monitoring module deployment: Three wireless water level gauges (numbered S1-S3) are installed 3m away from the slope toe on the outside of the foundation pit. The WL-2000 type wireless water level gauges (range 0-50m, accuracy ±2cm) are used. The monitoring frequency is once every 4 hours during the earthwork excavation stage and once a day after the support is completed.

[0066] Environmental monitoring module deployment: Three environmental monitoring stations (numbered H1-H3) are set up at the boundary of the construction site. Each monitoring station integrates a noise sensor (NZ-300, measurement range 30-130dB, accuracy ±1dB), a dust sensor (YC-500, measurement range 0-10mg / m³, accuracy ±0.01mg / m³), and a temperature sensor (T-100, measurement range -20-80℃, accuracy ±0.1℃). Monitoring frequency: noise and dust are collected in real time, and temperature is collected once per hour.

[0067] Data transmission and integration: The BIM platform adopts a GPRS+LoRa dual-mode wireless transmission network with a data transmission delay of ≤30s. The platform automatically receives, stores, and processes monitoring data, generates daily / weekly / monthly monitoring reports, and supports data export and anomaly tracing.

[0068] (iv) Early warning and response mechanism

[0069] Safety threshold and warning threshold settings:

[0070]

[0071] Working principle: The monitoring equipment collects data in real time and uploads it to the BIM platform via a wireless transmission network. The platform compares the monitoring data with preset thresholds in real time. When the data reaches or exceeds the warning threshold, it automatically determines the warning level and triggers the corresponding warning information push and emergency response procedures, forming a closed-loop workflow of "collection-transmission-analysis-warning-response".

[0072] How to use:

[0073] Early warning information push: Yellow warnings are sent via BIM platform pop-up and SMS notifications to project management personnel; orange warnings are also pushed to construction team leaders via APP; red warnings are simultaneously pushed to relevant personnel of the construction unit, supervision unit, and subway operation unit.

[0074] Emergency response procedures:

[0075] Yellow alert: On-site technicians shall arrive at the monitoring point within 1 hour to verify the data, confirm its authenticity, investigate factors affecting construction, record the verification results and upload them to the platform.

[0076] Orange Alert: Immediately halt earthwork excavation and anchor cable tensioning in the alerted area. Increase the monitoring frequency in the area to once per hour. The technical supervisor should organize a special meeting to analyze the cause and take measures such as adjusting the excavation sequence and slowing down the excavation speed. Construction can only be resumed after three consecutive monitoring data returns to the safe threshold.

[0077] Red Alert: All construction activities in the foundation pit shall be completely halted. Emergency plans shall be activated, personnel shall be evacuated, and reinforcement measures shall be taken, such as additional tensioning of anchor cables (tensioning stress of 100-150MPa) and the addition of temporary steel supports (spacing 3m, using I40b I-beams). Dedicated personnel shall be assigned to monitor the site 24 hours a day. Construction may only resume after the monitoring data has been stable within the safety threshold for 72 consecutive hours and has been approved by experts.

[0078] (V) Implementation Results

[0079] This embodiment achieves the following effects through the application of the above technical solution:

[0080] Deformation control of the support structure: The maximum horizontal displacement of the pit slope was 18.6 mm, and the maximum settlement of the subway structure was 6.8 mm, both of which met the safety threshold requirements of the subway protection zone and did not have an adverse impact on subway operation;

[0081] Monitoring system performance: The average data acquisition delay is 22 seconds, the data accuracy is 99.8%, and the BIM platform realizes integrated visualization of monitoring data, construction progress, and structural model, allowing managers to monitor the project status in real time.

[0082] Early warning response effect: During the construction period, a total of 3 yellow warnings and 1 orange warning were issued, and no red warnings occurred. Through timely response and handling, 2 potential risks of excessive deformation were effectively avoided, ensuring the safety of both foundation pit construction and subway operation.

[0083] Environmental compliance: The average daytime construction noise level is 65dB and the average nighttime noise level is 52dB. The average PM10 concentration is 0.35mg / m³, both of which meet environmental standards. No complaints have been received from nearby residents.

[0084] II. Specific Examples

[0085] Example 1: Technical solution for supporting cast-in-place piles and inter-pile concrete

[0086] (I) Project Background

[0087] This embodiment is a specific application of the support piles and shotcrete between the piles in the overall embodiment. It focuses on the structural design, construction technology and protective effect of the concrete between the piles, in response to the high rigidity support requirements of the subway protection zone.

[0088] (II) Structural Features and Assembly Relationships

[0089] Features of cast-in-place pile structure:

[0090] Dimensions: Pile diameter 1000mm, pile length 20m, pile center distance 1.2m, pile body concrete strength grade C30, using P.O42.5 grade cement, medium sand, 5-31.5mm crushed stone, mix ratio of cement:sand:stone:water = 1:1.8:3.2:0.52, slump 180-220mm.

[0091] Reinforcement parameters: 21 main bars of HRB-400E Φ20 threaded steel, with a cross-sectional area of ​​6600mm² and a reinforcement ratio of 0.85%; stirrups of Φ12@150 spiral stirrups, with Φ14@100 stirrups in the dense zone (3m from the top of the pile and 3m from the bottom of the pile); the protective layer thickness of the main bars is 70mm, and they are fixed with C30 fine stone concrete blocks at 1.5m intervals.

[0092] Characteristics of shotcrete structures between piles:

[0093] Dimensions: Thickness 100mm, concrete strength grade C20, mix ratio cement:sand:stone:water = 1:2.5:4.0:0.55, initial setting time ≤15min, final setting time ≤30min.

[0094] Reinforcement parameters: Internal reinforcement with Φ6@250×250 steel mesh, the steel mesh is connected by binding, the lap length is ≥200mm, and the distance between the mesh and the soil surface between piles is ≥30mm.

[0095] Assembly relationship:

[0096] Cast-in-place piles and capping beams: The main reinforcement of the support piles is embedded 700mm into the capping beam and is lapped with the main reinforcement (Φ25) of the capping beam on both sides. The weld length is 200mm (10d) and the weld thickness is ≥10mm.

[0097] Reinforcing mesh between piles and cast-in-place piles: The reinforcing mesh is fixed to the main reinforcement of the cast-in-place pile by welding with Φ12 positioning steel bars. The positioning steel bars are spaced 1.5m apart, with no less than 2 welding points on each side to ensure that the mesh is flat and firm.

[0098] (III) Construction methods and parameter control

[0099] Construction method of cast-in-place piles:

[0100] Hole Formation: An XR280D rotary drilling rig is used, with the drilling speed controlled at 0.5-1m / min. Mud slurry is used for wall protection (mud specific gravity 1.05-1.10, viscosity 18-22s). After hole formation, an ultrasonic tester is used to check the verticality of the hole wall, and the deviation is ≤0.5%.

[0101] Hole cleaning: Hole cleaning is carried out using the mud replacement method. After cleaning, the sediment thickness is ≤50mm, the mud specific gravity is ≤1.05, and the sand content is ≤2%.

[0102] Reinforcing cage installation: It is hoisted in 3 sections (6.5m each). The main reinforcement bars between sections are double-sided lap welded, with a weld length ≥200mm. The weld quality meets the requirements of Grade II weld in the "Code for Welding and Acceptance of Reinforcing Steel Bars" JGJ18-2012. The center deviation of the reinforcing cage installation is ≤50mm.

[0103] Concrete pouring: Use Φ250mm guide pipe, with the bottom of the guide pipe 300-500mm from the bottom of the hole. The initial concrete volume should be ≥1.5m³, and the guide pipe should be buried at a depth of ≥1.2m. During the pouring process, the depth of the guide pipe should be controlled between 2-6m, the pouring speed should be ≥2m / h, and the pouring should be continuous without interruption. The top of the pile should be over-poured by 500mm. After the pouring is completed, the floating slurry on the top of the pile should be cleaned in time.

[0104] Maintenance: Cover with geotextile and sprinkle water for maintenance. The maintenance period is ≥14 days. During the maintenance period, loads are prohibited before the pile top strength reaches 70% of the design strength.

[0105] Construction method of shotcrete between piles:

[0106] Soil cleaning: After the anchor cables are locked, the loose soil between the piles is cleaned manually to ensure that the soil surface is flat and free of loose soil and debris.

[0107] Reinforcing mesh installation: The reinforcing mesh is installed from bottom to top and welded to the positioning reinforcing bars. The overlap length at the mesh splice is ≥200mm.

[0108] Spraying application: Use a PZ-5 spraying machine with a working air pressure of 0.4-0.6MPa, a spraying distance of 0.8-1.2m, and a spraying angle of 70-90°. Spray in sections from top to bottom, with each section being 1.5m high. After spraying, the surface flatness deviation should be ≤10mm.

[0109] (iv) Working principle and implementation effect

[0110] Working principle: Large-diameter, small-spacing cast-in-place piles, through high-strength concrete and dense reinforcement, form high-rigidity vertical support components to resist the lateral pressure of the soil outside the foundation pit; the shotcrete between the piles and the steel mesh work together to prevent the soil between the piles from collapsing, forming a complete retaining system, jointly inhibiting soil deformation and ensuring the stability of the foundation pit slope.

[0111] Implementation results: The 28-day compressive strength of the cast-in-place piles reached 35.2 MPa, and the flexural bearing capacity reached 1200 kN·m, meeting the design requirements; there were no cracks or spalling in the shotcrete between the piles, and the maximum horizontal displacement of the foundation pit slope was 18.6 mm, achieving the deformation control target of the subway protection zone.

[0112] Example 2: Supporting Prestressed Anchor Cable Technology Solution

[0113] (I) Project Background

[0114] This embodiment is a specific application of prestressed anchor cables in the overall embodiments. It focuses on the material selection, layout parameters, construction technology and prestress transfer effect of anchor cables, in response to the requirements of actively restraining the soil in the subway protection zone.

[0115] (II) Structural Features and Assembly Relationships

[0116] Anchor cable structure features:

[0117] Material parameters: Two low-relaxation steel strands with a nominal diameter of 15.2 mm and a standard strength value of 1860 MPa (GB / T5224-2014) are used. The breaking tensile strength of a single steel strand is ≥260 kN and the elastic modulus is 195 GPa.

[0118] Layout parameters: horizontal spacing 2.5m, vertical spacing 2.0m, incident angle 15° (shallow area, excavation depth 9.33m)-20° (deep area, excavation depth 12.55m); free section length 4m (shallow area)-6m (deep area), anchorage section length 8m (shallow area)-10m (deep area), total anchor cable length 12m-16m.

[0119] Grouting material: P.O42.5 grade cement grout is used. The water-cement ratio is 0.5:1 for the first grouting and 0.45:1 for the second grouting. 3% of the cement weight of expansion agent (UEA) is added to the grouting material to improve the bond between the grout and the soil.

[0120] Anchorage and assembly relationship:

[0121] Anchorage: OVM15-2 type wedge anchorage is adopted, with anchor plate hole diameter of 15.9mm, wedge cone angle of 6°, anchorage breaking tensile force ≥520kN, and anchorage efficiency coefficient ≥0.95.

[0122] Assembly Relationship: The steel strands are tied parallel to the grouting pipes, with a tying point spacing of 1.5m, and are firmly tied with Φ1.2mm iron wire; the grouting pipes are Φ20mm PE pipes, the primary grouting pipes are ≥200mm from the bottom of the hole, and the secondary grouting pipes are equipped with grouting perforated pipes (8mm diameter, 200mm spacing) at the end, located in the middle of the anchoring section; when installing the anchor cables, ensure that the steel strands are not twisted and that the grouting pipes are unobstructed.

[0123] (III) Construction methods and parameter control

[0124] Anchor cable construction method:

[0125] Drilling: The XR220D-CAF drilling rig is used, with a drill bit diameter of 150mm. The drilling speed is controlled at 0.3-0.5m / min. Mud wall protection is used (mud specific gravity 1.03-1.05). The verticality deviation of the borehole is ≤1%, and the hole position deviation is ≤100mm.

[0126] Steel strand installation: The steel strand should be cut to a length 1.5m longer than the design length (for tensioning). Use an abrasive wheel saw for cutting; gas cutting is prohibited. Lower the steel strand slowly during installation to avoid scratching the steel strand or bending the grouting pipe.

[0127] One-time grouting: Use a UB-6 type grouting pump, grouting pressure 0.8-1.0MPa, grouting flow rate 30-50L / min until thick grout overflows from the orifice, stabilize the pressure for 5 minutes and then stop grouting.

[0128] Secondary high-pressure grouting: This is carried out 24 hours after the completion of the first grouting. A high-pressure grouting pump is used, with a grouting pressure ≥1.5MPa and a grouting flow rate of 20-30L / min. Grouting is stopped after stabilizing the pressure for 3 minutes to ensure that the grout penetrates into the soil pores and improves the anchoring force.

[0129] Curing: After grouting is completed, the anchor cables should be cured for 7 days. During the curing period, the anchor cables should not be disturbed. When the ambient temperature is below 5℃, heat preservation measures should be taken.

[0130] Prestressing tensioning: YCW250 tensioning equipment was used, with a tensioning control stress of 1320MPa (71% of the standard value of steel strand strength). The tensioning was carried out in stages: 10%σcon (pre-tensioning) → 30%σcon → 70%σcon → 100%σcon, with each stage held for 5 minutes. The elongation value of the steel strand was recorded, and the deviation between the actual elongation value and the theoretical elongation value was controlled within ±6%.

[0131] Locking and Anchoring: Anchors are used to lock the strands immediately after tensioning, and the exposed length of the strands after locking is ≥150mm; C30 fine aggregate concrete is used to seal the anchors, and the anchor thickness is ≥100mm.

[0132] (iv) Working principle and implementation effect

[0133] Working principle: By applying prestress to the steel strands, the tension is transferred to the grout in the anchoring section. The grout generates frictional resistance with the soil and the borehole wall, forming an anchoring force. This actively restrains the support piles and the soil behind them, limiting the lateral deformation of the soil and reducing the impact of the foundation pit deformation on the subway structure. Secondary high-pressure grouting further improves the density and adhesion of the grout, ensuring the long-term stable transmission of prestress.

[0134] Implementation results: The anchoring force test value of the anchor cable is ≥500kN, which meets the design requirements (design anchoring force 450kN); the prestress loss rate is ≤5% (10-day observation); the horizontal displacement of the foundation pit slope is reduced by 40% compared with the scheme without anchor cable support, effectively controlling soil deformation and ensuring the safety of the subway structure.

[0135] Example 3: Technical Solution Supporting Deformation Monitoring Module

[0136] (I) Project Background

[0137] This embodiment is a specific application of the deformation monitoring module in the overall embodiments. It focuses on the layout of deformation monitoring points, equipment selection, monitoring methods and data reliability in response to the requirements of accurate deformation monitoring in subway protection zones.

[0138] (II) Structural Features and Assembly Relationships

[0139] Structural characteristics of monitoring points:

[0140] Horizontal displacement monitoring point: adopts stainless steel forced centering base, buried at a depth of ≥500mm, with the top of the base flush with the top of the slope, and is surrounded by protective railings to prevent collision.

[0141] Settlement monitoring points: Stainless steel settlement observation markers are used, which are welded and fixed to the top of the subway track bed shoulder and entrance / exit structure. The top of the observation marker is polished smooth and protrudes 10mm above the structure surface.

[0142] Inclinometer tube: PVC-U inclinometer tube with a diameter of 70mm and a wall thickness of 5mm is used. Each section is 4m long and the sections are connected by a socket joint. The joints are sealed with sealant to prevent mud from seeping in. The inner wall of the inclinometer tube is equipped with a guide groove, which is parallel to the edge of the foundation pit.

[0143] Assembly relationship:

[0144] Horizontal displacement monitoring points: One point is set up every 5m along the top of the slope on the side of the foundation pit facing the subway, for a total of 18 points. The adjacent monitoring points have good visibility and are ≥1m away from the edge of the foundation pit.

[0145] Settlement monitoring points: 1 point is set up every 10m along the subway track bed (along the line direction), for a total of 8 points; 1 point is set up every 10m around the subway entrances and exits (3m from the edge of the entrances and exits), for a total of 4 points. The monitoring points avoid the areas where the track stress is concentrated.

[0146] Inclinometer tube: Pre-embedded during the construction of the support piles. The bottom of the inclinometer tube is embedded in the stable rock layer for ≥1m, and the top is 500mm above the top surface of the cap beam. It is sealed with a protective cap and the verticality deviation of the inclinometer tube is ≤0.5%.

[0147] (III) Monitoring Equipment and Parameter Control

[0148] Monitoring equipment:

[0149] Total station: Model TS60, angle measurement accuracy ±0.5″, distance measurement accuracy ±(0.6mm+1ppm×D), equipped with prism group for horizontal displacement monitoring.

[0150] Electronic level: Model DL2020, with a mean error of ±0.3mm per kilometer for round trip elevation measurement, equipped with an indium steel leveling rod, used for settlement monitoring.

[0151] Inclinometer: Model CX-03, measuring range ±30°, resolution 0.01°, sensitivity 0.001°, used for deep displacement monitoring of piles.

[0152] Parameter control:

[0153] Monitoring frequency: During the earthwork excavation stage (excavation of the foundation pit to the design depth), horizontal displacement and settlement are monitored twice a day (9:00 am and 4:00 pm), and deep pile displacement is monitored once every 2 hours; after the support structure is completed, horizontal displacement and settlement are monitored twice a week, and deep pile displacement is monitored once a day; when an early warning occurs, the monitoring frequency is increased to once every 1 hour.

[0154] Data accuracy: Horizontal displacement measurement error ≤ ±2mm, settlement measurement error ≤ ±0.5mm, deep pile displacement measurement error ≤ ±0.1mm / m.

[0155] (iv) Monitoring methods and working principles

[0156] Monitoring methods:

[0157] Horizontal displacement monitoring: Using the polar coordinate method, a plane control network is established with three stable control points outside the foundation pit (which have been certified by the subway operator) as the benchmark. During each monitoring, a total station is set up on the control points to observe each horizontal displacement monitoring point, record the horizontal angle and distance, calculate the plane coordinates of the monitoring points, and compare them with the initial coordinates to obtain the horizontal displacement.

[0158] Settlement monitoring: Second-order leveling method is adopted. Based on the elevation control points provided by the subway operator, an elevation control network is established. During each monitoring, the settlement monitoring points are observed along the forward and backward survey route. The elevation of the monitoring points is calculated and compared with the initial elevation to obtain the settlement amount.

[0159] Deep pile displacement monitoring: The inclinometer probe is placed at the bottom of the inclinometer tube along the guide groove. The probe is raised at 500mm intervals to measure the inclination angle of the pile at each point. The horizontal displacement of the pile at each depth is calculated based on the inclination angle and the measurement interval, and the pile displacement curve is plotted.

[0160] Working principle: By setting up monitoring points at key locations, high-precision monitoring equipment is used to collect displacement data of the foundation pit and subway structure in real time. Combined with preset thresholds, it is determined whether the structural deformation exceeds the allowable range, providing data support for risk warning. The continuity and accuracy of the monitoring data ensure accurate prediction of deformation trends.

[0161] (V) Implementation Results

[0162] Data reliability: Repeat observation error of horizontal displacement monitoring data ≤ ±1.5mm, repeat observation error of settlement monitoring data ≤ ±0.3mm, repeat observation error of deep pile displacement monitoring data ≤ ±0.08mm / m, data accuracy rate 99.8%.

[0163] Effectiveness of the early warning: During construction, deformation monitoring promptly detected two abnormal deformation trends (daily changes in horizontal displacement of 2.3 mm and 2.4 mm), allowing for early intervention and preventing the triggering of the early warning, thus ensuring the safety of the subway structure. The monitoring data fully recorded the entire process of foundation pit deformation, providing a reference for similar projects in the future.

[0164] Example 4: Technical Solution for Vibration and Environmental Monitoring Module

[0165] (I) Project Background

[0166] This embodiment is a specific application of the vibration monitoring module and environmental monitoring module in the overall embodiment. Addressing the stringent restrictions on construction vibration in subway protection zones (to avoid affecting subway track stability) and environmental compliance requirements (to control the impact of construction noise and dust on the surrounding environment), it focuses on threshold settings, monitoring equipment deployment, and control measures for indicators such as vibration velocity, noise, and dust. This solves the problems of traditional monitoring methods lacking clear quantitative standards for indicators and targeted control measures. The project overview is consistent with the overall embodiment.

[0167] (II) Structural Features and Assembly Relationships

[0168] Vibration monitoring module structural features:

[0169] Core equipment: VS-100 vibration sensor with built-in high-precision accelerometer, supports dual parameter acquisition of vibration velocity and acceleration, measurement range 0.01-10cm / s, frequency response 1-500Hz, output signal is 4-20mA standard signal, power supply voltage 12-24VDC, protection level IP67, adaptable to the harsh environment of foundation pit construction.

[0170] Auxiliary structure: The sensor is equipped with a stainless steel mounting base, which measures 200mm×200mm×100mm and is made of Q235 steel plate welded together. There are 4 M16 expansion bolt holes at the bottom.

[0171] Structural features of the environmental monitoring module:

[0172] Noise sensor: Model NZ-300, measurement range 30-130dB(A), frequency response 20-12500Hz, accuracy ±1dB, supports real-time equivalent continuous A-weighted sound level calculation;

[0173] Dust sensor: Model YC-500, based on the principle of laser scattering, measures particle size range of 0.3-10μm (PM10), measurement range of 0-10mg / m³, accuracy of ±0.01mg / m³, data sampling rate of 1 time / minute;

[0174] Integrated structure: Noise and dust sensors are integrated into an integrated environmental monitoring station. The main body of the monitoring station is a galvanized steel pipe support with a height of 2.5m. A rainproof and dustproof cover is installed on the top, and a fixed flange is set at the bottom.

[0175] Assembly relationship:

[0176] Vibration sensors: Six sensors are evenly distributed at the boundary of the 10-meter special protection zone between the foundation pit and the subway, 3m from the toe of the foundation pit slope and 10m from the center line of the subway track. The sensors are fixed to the mounting base with expansion bolts. The pre-embedded depth of the base is ≥300mm. The sensor axis is perpendicular to the horizontal plane to ensure accurate acquisition of vibration signals.

[0177] Environmental monitoring stations: A total of 3 stations are set up, located on the north side of the construction site (near the subway protection zone), the east side (near the residential area), and the south side (near the city road). The monitoring station flange is fixed to the concrete foundation (500mm×500mm×300mm) by 4 M20 expansion bolts. The sensor probes face the monitoring area to avoid building obstruction and strong electromagnetic field interference.

[0178] (III) Parameters

[0179] Vibration monitoring parameters:

[0180] Control thresholds: Safety threshold ≤ 0.15 cm / s, yellow warning threshold 0.18 cm / s, orange warning threshold 0.2 cm / s, red warning threshold 0.3 cm / s;

[0181] Data acquisition parameters: data sampling rate 100Hz, single acquisition duration 10s, acquisition interval synchronized with construction (real-time acquisition during mechanical operation, acquisition once every 30 minutes when no operation).

[0182] Environmental monitoring parameters:

[0183] Noise control standards: Daytime (6:00-22:00) ≤70dB(A), Nighttime (22:00-6:00 the next day) ≤55dB(A); Warning thresholds: Exceeding the standard for 10 minutes triggers an orange warning, and exceeding the standard for 30 minutes triggers a red warning;

[0184] Dust (PM10) control standards: Safety threshold during structural construction phase ≤ 0.3 mg / m³, yellow warning threshold 0.4 mg / m³, orange warning threshold 0.5 mg / m³, red warning threshold 0.8 mg / m³;

[0185] Data collection parameters: Noise is collected in real time, dust is collected once per minute, and the data storage period is ≥90 days.

[0186] (iv) Construction / Usage Method

[0187] Equipment installation:

[0188] Vibration sensor installation: First, pour a concrete foundation and pre-embed the installation base. After the foundation has cured for 7 days, fix the sensor to the base, calibrate the verticality of the sensor with a level (deviation ≤ 0.5°), connect the power supply and signal transmission line, and ensure waterproof sealing.

[0189] Environmental monitoring station installation: Pour concrete foundation and fix flange, install galvanized steel pipe support, hoist integrated sensor module, connect power supply (AC220V) and wireless transmission module, and adjust sensor orientation.

[0190] System debugging:

[0191] Vibration sensor: Calibrated using a standard vibration table, with a standard vibration signal of 0.2 cm / s input, the sensor output error is ≤ ±5%, and the data transmission stability is tested (no packet loss for 24 consecutive hours).

[0192] Environmental monitoring module: The noise sensor is calibrated using a sound level calibrator (accuracy ±0.1dB), and the dust sensor is calibrated using a standard dust source to ensure that the measurement accuracy meets the requirements.

[0193] Daily use:

[0194] Data Acquisition: The equipment automatically collects data and uploads it to the BIM collaborative management platform via GPRS wireless transmission network, with a transmission delay of ≤30s;

[0195] Equipment maintenance: Check the appearance and fixation of the sensor daily, clean the sensor probe weekly, calibrate the measurement accuracy monthly, and check the waterproof performance promptly after rain.

[0196] (V) Working Principle

[0197] Vibration sensors collect vibration signals from construction machinery (rotary drilling rigs, excavators, cranes, etc.) in real time, converting the mechanical vibration into electrical signals. After amplification and filtering, the signals are transmitted to the BIM platform, which automatically calculates the effective value of the vibration velocity and compares it with preset thresholds in real time. In the environmental monitoring module, noise sensors convert sound waves into electrical signals, and dust sensors detect dust particle concentration using laser scattering principles. Both types of data are uploaded to the platform simultaneously, and the equivalent sound level and average dust concentration are calculated separately for day and night. When the monitored data reaches or exceeds the corresponding warning threshold, the platform automatically triggers a tiered warning, pushes it to relevant responsible persons, and simultaneously initiates preset control measures (such as adjusting the operating time of construction machinery and increasing the use of mist cannons for dust suppression), achieving real-time control of vibration and environmental impact.

[0198] (vi) Implementation Results

[0199] During construction, vibration sensors collected over 120,000 data points, with a maximum vibration velocity of 0.19 cm / s (triggering a yellow alert once). By adjusting the excavator's operating hours (avoiding the subway's morning rush hour of 7:00-9:00 and evening rush hour of 17:00-19:00), the vibration velocity was stably controlled below 0.15 cm / s, without any adverse impact on the subway tracks. Noise monitoring showed an average daytime level of 65 dB(A) and a nighttime level of 52 dB(A), and the average PM10 concentration was 0.35 mg / m³, all meeting environmental control standards. No complaints were received from surrounding residents or the subway operator, achieving the dual goals of construction safety and environmental compliance.

[0200] Example 5: Technical Solution for Supporting BIM Platform Integration with Progress Management and Temperature Monitoring

[0201] (I) Project Background

[0202] This embodiment is an extended application of the BIM 3D collaborative management platform in the overall embodiment. Addressing the issues of disconnect between safety monitoring data and construction progress in traditional construction, and the tendency for cracks to occur due to the heat of hydration in the support structure concrete, it focuses on the integrated linkage between the BIM platform and the progress management system, as well as the integration of a wireless temperature monitoring system for large-volume concrete, to achieve integrated management and control of construction progress, safety monitoring, and temperature monitoring. The project overview is consistent with the overall embodiment.

[0203] (II) Structural Features and Assembly Relationships

[0204] BIM platform structural features:

[0205] Core software: Autodesk Revit 2023 is used to build 3D models of foundation pit support structures and subway structures, NavisworksManage is used for progress simulation, and Fuzor is used for visualization. The platform supports Windows 10 / 11 operating systems, and the database uses SQL Server 2019.

[0206] Functional modules include a model management module, a data integration module, a progress linkage module, a temperature monitoring module, and an early warning push module. These modules communicate with each other via API interfaces.

[0207] Structural features of the temperature monitoring module:

[0208] Temperature sensor: The T-100 wireless temperature sensor is used, with a measurement range of -20-80℃, an accuracy of ±0.1℃, a transmission distance of ≤500m (open environment), and a power supply of lithium battery (battery life ≥1 year).

[0209] Data acquisition unit: Model DC-800, supports simultaneous access to 32 temperature sensors, has data storage (capacity ≥ 100,000 records) and wireless transmission functions, and supports GPRS / 4G communication.

[0210] Assembly relationship:

[0211] BIM Platform and Schedule Management System: By connecting to the Zebra Project Management System through the API interface, the construction schedule (start and end times of sub-projects) is imported into the BIM platform to achieve the binding of the 3D model and the schedule.

[0212] Temperature sensors and support structure: Temperature sensors are pre-embedded in the support piles (1 out of every 10 piles) and the capping beam. One sensor is installed every 3m along the height of the support pile (7 sensors per pile), and one sensor is installed every 5m along the length of the capping beam (18 sensors in total). The sensors are tied and fixed to the steel cage to ensure close contact with the concrete.

[0213] Data acquisition unit and sensor: One data acquisition unit is installed in each temperature measurement area. The acquisition unit is fixed to the side of the crown beam and connected to the sensor via wireless signal. The acquisition unit communicates with the BIM platform via GPRS network.

[0214] (III) Parameters

[0215] BIM platform parameters:

[0216] Data update frequency: Safety monitoring data is updated once every 30 seconds; construction progress data is updated once a day; temperature monitoring data is updated once every 30 minutes.

[0217] Model accuracy: 3D model component size error ≤ ±1mm, progress simulation accuracy ≤ ±1 day;

[0218] Storage capacity: Supports data storage of ≥1 million monitoring records, with daily automatic backup.

[0219] Temperature monitoring parameters:

[0220] Monitoring indicators: internal temperature and surface temperature of the concrete in the support piles and capping beams, and ambient temperature;

[0221] Control thresholds: temperature difference between the inside and outside of concrete ≤25℃, cooling rate ≤2℃ / d;

[0222] Sampling interval: Sampling once every 30 minutes within 7 days after concrete pouring, and once every 2 hours after 7 days. Sampling will stop after the curing period (14 days).

[0223] (iv) Construction / Usage Method

[0224] BIM Platform Setup and Integration:

[0225] 3D model construction: Based on the design drawings, use Revit software to create 3D models of the support piles, capping beams, anchor cables, and subway structure, and define component properties (dimensions, materials, strength grades, etc.).

[0226] Importing the schedule: Export the construction schedule (XML format) from the Zebra Project Management System, import it into the BIM platform through the Navisworks interface, bind the schedule tasks to the 3D model components, and set the start and end times of the sub-items of the project;

[0227] System Integration: Data exchange between the BIM platform and the intelligent monitoring system and wireless temperature measurement system is achieved through API interfaces, and the data transmission protocol (TCP / IP) is configured to ensure real-time data synchronization.

[0228] Temperature monitoring system installation and use:

[0229] Sensor pre-embedding: When fabricating the support pile reinforcement cage, the temperature sensor is tied and fixed in the preset position, and the sensor cable is protected (covered with PVC pipe) to avoid damage during pouring; after the cap beam reinforcement is tied, the sensor is fixed in the design position.

[0230] Data acquisition unit debugging: Before concrete pouring, start the data acquisition unit, test the sensor communication status (communication success rate ≥99%), and calibrate the sensor measurement accuracy;

[0231] Platform configuration: Set temperature monitoring thresholds and early warning rules in the BIM platform. When the temperature difference between inside and outside exceeds 25°C, a yellow warning will be triggered.

[0232] Daily use:

[0233] Progress and monitoring linkage analysis: By viewing the construction progress and corresponding monitoring data through the BIM platform, the platform automatically marks the progress node when the monitoring data of a certain sub-item of the project is abnormal during construction.

[0234] Temperature control: Monitor the concrete temperature change curve in real time, and take measures such as covering with insulation blankets and watering for curing when a temperature warning is triggered, and adjust the curing plan accordingly.

[0235] (V) Working Principle

[0236] The BIM platform integrates multi-source data (safety monitoring, construction progress, and temperature monitoring) through interfaces, using the 3D structural model as the data carrier to achieve spatial positioning and visualization of monitoring data. When construction progress and monitoring data are linked, the platform automatically analyzes the risk change patterns at different construction stages, and simultaneously alerts management personnel when progress is delayed or monitoring data is abnormal. In the temperature monitoring system, embedded sensors collect concrete temperature data in real time, which is transmitted to the BIM platform via a data acquisition device. The platform automatically calculates the internal and external temperature difference and cooling rate, compares it with preset thresholds, and pushes maintenance adjustment suggestions when an early warning is triggered. Through integrated management, collaborative control of construction progress, safety risks, and structural quality is achieved, solving the problems of data dispersion and poor coordination in traditional management.

[0237] (vi) Implementation Results

[0238] In this embodiment, the BIM platform successfully achieved the linkage analysis of construction progress and safety monitoring data. Managers can intuitively view the correspondence between "construction stage - monitoring data - risk status" through the platform, and have identified three issues related to the correlation between progress and risk (such as excessively rapid earthwork excavation leading to increased deformation rate), and have adjusted the construction pace in a timely manner. The temperature monitoring system effectively controlled the heat of hydration of concrete. The maximum internal and external temperature difference of the support piles was 22℃, and the maximum internal and external temperature difference of the cap beam was 20℃, both of which did not exceed the control threshold, and no temperature cracks occurred. The concrete strength of the support structure met the standard rate of 100%, which significantly improved the efficiency of construction management and the quality of structural construction.

[0239] Example 6: Supporting a tiered early warning mechanism and a red alert emergency response technical solution

[0240] (I) Project Background

[0241] This embodiment is a specific application of the tiered early warning and coordinated response mechanism in the overall embodiment. Addressing the complex risk levels of construction near subway foundation pits and the need for precise and efficient emergency response, it focuses on the threshold settings for yellow, orange, and red early warning levels, information delivery methods, and specific emergency measures for red early warnings, solving the problems of vagueness and delayed response in traditional early warning mechanisms. The project overview is consistent with the overall embodiment.

[0242] (II) Structural Features and Assembly Relationships

[0243] Structural characteristics of early warning mechanisms:

[0244] Core components: BIM collaborative management platform early warning module, SMS push gateway, mobile APP client, emergency command terminal;

[0245] Warning levels are classified as follows: Yellow warning (general risk), Orange warning (relatively high risk), and Red warning (major risk). Each warning level corresponds to an independent threshold standard, notification scope, and response procedure.

[0246] Emergency response structural characteristics:

[0247] Prestressing compensation equipment: YCW250 tensioning jacks are used, equipped with ZB4-500 high-pressure oil pumps, with a tensioning range of 0-250kN and an accuracy of ±1%;

[0248] Temporary support components: I40b I-beams (section dimensions 400mm×142mm×10.5mm), with matching steel plate supports (dimensions 300mm×300mm×20mm) and high-strength bolts (M24).

[0249] Assembly relationship:

[0250] Early warning device linkage: The BIM platform's early warning module is connected to the SMS gateway and mobile APP client via the network, and a list of contact persons for each level of early warning is preset (yellow warnings are sent to project technical personnel, orange warnings are sent to the project manager, and red warnings are sent to the heads of construction, supervision, and subway operation units simultaneously).

[0251] Emergency equipment deployment: Prestressed compensation equipment is stored in a temporary warehouse on the west side of the foundation pit (≤50m from the edge of the foundation pit). Temporary support components are reserved at a rate of one set per 10m of foundation pit length and stored in designated areas around the foundation pit to ensure convenient emergency deployment.

[0252] (III) Parameters

[0253] Tiered early warning threshold parameters (core indicators):

[0254]

[0255] Emergency response parameters:

[0256] Prestress compensation: The additional tension stress is 100-150MPa, and the holding time for a single tensioning is ≥5min;

[0257] Temporary supports: I-beams spaced 3m apart, with both ends of the supports welded and fixed to the steel plate supports of the cap beam and the bottom beam of the foundation pit. The verticality deviation of the supports is ≤1°, and the bearing capacity is ≥500kN / m.

[0258] (iv) Construction / Usage Method

[0259] Early warning mechanism configuration:

[0260] Threshold setting: Enter the warning thresholds at all levels in the BIM platform, associate them with monitoring indicators (such as horizontal displacement, settlement, vibration, etc.), and set the warning trigger logic (single indicator exceeding the standard or multiple indicators exceeding the standard).

[0261] Push configuration: Bind contact's mobile phone number and APP account, set push priority (red alert is the highest and is pushed first), SMS push delay ≤10s, APP pop-up push in real time.

[0262] Red Alert Emergency Response Procedure:

[0263] Warning Trigger: When the monitoring data reaches the red warning threshold, the BIM platform automatically triggers a red warning, simultaneously pushes the warning information to all preset contacts, locks the construction progress, and displays emergency response procedure guidelines;

[0264] Emergency work stoppage: After receiving the warning, the project manager immediately issued a complete work stoppage order. The construction teams stopped all foundation pit operations and organized personnel to evacuate to a safe area.

[0265] Prestress compensation: Technicians deploy tensioning equipment to perform supplementary tensioning on the anchor cables in the warning area, and perform tensioning in stages according to "10%σcon→30%σcon→supplementary tensioning target stress", and record the elongation value of the steel strands to ensure that the stress meets the standard;

[0266] Temporary support addition: If the deformation is still not controlled after additional tensioning, immediately hoist the I40b I-beam, lay temporary supports at the preset intervals, weld and fix the steel plate supports, and monitor the deformation data until it stabilizes after the support installation is completed;

[0267] Resumption of work approval: After deformation data has remained stable within the safety threshold for 72 consecutive hours, experts will be organized to conduct an assessment, and an emergency response report will be prepared and submitted to the construction, supervision, and subway operation units for approval. Construction can only resume after the approval is granted.

[0268] (V) Working Principle

[0269] The tiered early warning mechanism is based on preset quantitative thresholds. The BIM platform compares monitoring data with threshold standards in real time, automatically determines the risk level, and triggers corresponding early warnings. Information is pushed through multiple channels (platform pop-ups, SMS, and apps) to ensure that responsible personnel at different levels receive risk information in a timely manner. The red alert emergency response is based on the principle of "stopping work first, then reinforcing, and finally resuming work." Prestressed compensation equipment is used to supplement anchor cable tension, and temporary supports are used to enhance the rigidity of the support system. These dual measures suppress soil deformation and prevent the risk from escalating. The entire process forms a closed loop of "early warning triggering - information push - emergency response - monitoring and verification - resumption of work approval," ensuring accurate and efficient emergency response.

[0270] (vi) Implementation Results

[0271] During construction, the system triggered 3 yellow alerts and 1 orange alert, with no red alerts. A simulated red alert emergency drill showed that from the triggering of the alert to the completion of temporary support installation, only 4 hours elapsed. After the anchor cables were tensioned, the deformation rate decreased from 3.2 mm / d to 0.8 mm / d, verifying the effectiveness of the emergency response measures. The tiered early warning mechanism clearly defines the handling procedures for different risk levels, avoiding over- or under-control issues, ensuring the safety of foundation pit construction and subway operation, and improving emergency response efficiency by 60% compared to the traditional model.

[0272] Example 7: Technical Solution for Supporting the Design and Construction of Crown Beam Structures

[0273] (I) Project Background

[0274] This embodiment is a specific application of the capping beam structure in the overall embodiment. Addressing the issues of insufficient top restraint and poor pile-beam synergistic stress performance in the pile-anchor support system, it focuses on the cross-sectional dimensions, reinforcement parameters, connection method with the support piles, and construction technology of the capping beam. By strengthening the overall rigidity of the support system through the rigid capping beam, it further controls the deformation at the top of the foundation pit. The project overview is consistent with the overall embodiment.

[0275] (II) Structural Features and Assembly Relationships

[0276] Features of the cap beam structure:

[0277] Cross-sectional dimensions: 600mm (width, perpendicular to the edge of the pit) × 800mm (height, parallel to the depth of the pit), with the length consistent with the length of the adjacent subway side support piles (86m).

[0278] Material parameters: Concrete strength grade C30, using P.O42.5 grade ordinary Portland cement, aggregate is 5-31.5mm crushed stone and medium sand, mix ratio is cement:sand:stone:water = 1:1.8:3.0:0.53;

[0279] Reinforcement parameters: The main reinforcement consists of 16 HRB-400E Φ25 threaded steel bars (8 bars in the top row and 8 bars in the bottom row), the stirrups are Φ12@200 spiral stirrups, and the corresponding position at the top of the pile is equipped with Φ14@100 reinforcing stirrups (500mm in length), and the protective layer thickness is 50mm.

[0280] Assembly relationship:

[0281] Crown beam and support piles: The main reinforcement of the support piles is embedded in the crown beam for ≥700mm. The main reinforcement of the support piles and the main reinforcement of the crown beam are lap welded on both sides, with a weld length ≥10d (d=20mm) and a weld thickness ≥10mm. The concrete of the crown beam and the concrete at the top of the support piles are poured as a whole. The laitance at the top of the piles is removed to the fresh concrete surface (removal thickness ≥50mm).

[0282] Template and support: The cap beam template is made of 15mm thick film-coated plywood, the back rib is made of 50mm×100mm timber (spacing 300mm), and double Φ48×3.5mm steel pipe supports are set on the outside with a support spacing of 600mm. The bottom is fixed to the concrete pad (thickness 100mm, strength grade C15).

[0283] (III) Parameters

[0284] Structural performance parameters:

[0285] Concrete strength: 28-day compressive strength ≥ 30 MPa, axial tensile strength ≥ 2.01 MPa;

[0286] Flexural bearing capacity: ≥1500kN・m, shear bearing capacity ≥500kN;

[0287] Deformation control: Horizontal displacement of the top of the crown beam ≤ 5mm, vertical settlement ≤ 3mm.

[0288] Construction parameters:

[0289] Rebar processing: Main bar cutting length error ≤ ±10mm, stirrup hook angle 135°, straight section length ≥10d;

[0290] Template installation: Axis deviation ≤ ±5mm, cross-sectional dimension deviation ≤ ±3mm, surface flatness deviation ≤ 5mm / m;

[0291] Concrete pouring: The pouring speed is ≥1.5m³ / h, and the pouring is continuous without interruption. The vibration is carried out by an immersion vibrator (50mm diameter vibrator rod), the vibration spacing is ≤500mm, and the vibration time is 15-20s / point.

[0292] (iv) Construction / Usage Method

[0293] Construction preparation:

[0294] Material inspection upon arrival: After steel bars, cement, sand and gravel arrive on site, mechanical performance tests shall be conducted in accordance with the specifications, and they may only be used after passing the tests.

[0295] Treatment of the top of the support pile: After the support pile has been cured to 70% of its design strength, use a pneumatic hammer to remove the laitance and loose concrete at the top of the pile to expose the fresh concrete surface, and clean up the debris and water at the top of the pile.

[0296] Measurement and layout: Use a total station to lay out the axis and edge lines of the cap beam, and mark the control lines for rebar tying and formwork installation.

[0297] Rebar tying:

[0298] Main reinforcement installation: Place the upper and lower rows of main reinforcement according to the design position, fix them with binding wire (500mm spacing), and set Φ25 steel bar supports (1.5m spacing) to ensure the thickness of the protective layer of the main reinforcement;

[0299] Stirrup installation: Insert the stirrups into the main reinforcement bars and tie them at 200mm intervals. Add reinforcing stirrups at the corresponding positions on the top of the support piles and weld them to the main reinforcement bars for fixation.

[0300] Reinforcing bar connection: When the main reinforcement bar is not long enough, flash butt welding shall be used for connection. The weld length shall be ≥10d. The joint position shall avoid the stress concentration area. The joint rate of the same section shall be ≤50%.

[0301] Template installation and reinforcement:

[0302] Template assembly: Assemble plywood according to the cross-sectional dimensions of the cap beam, and seal the joints with sealant to prevent grout leakage;

[0303] Support installation: Install timber back ribs and steel pipe supports, and set a pad (200mm×200mm×10mm) at the bottom of the support. Adjust the verticality and flatness of the formwork to meet the construction parameter requirements.

[0304] Acceptance: After the template installation is completed, check the axis, cross-sectional dimensions, and support rigidity. After the supervisor approves the installation, proceed to the next process.

[0305] Concrete pouring and curing:

[0306] Concrete is transported by tanker truck, poured through chutes, and compacted using an immersion vibrator. After pouring to the design elevation, the surface is smoothed with a wooden trowel.

[0307] Curing: Cover with geotextile and water within 12 hours after pouring, and cure for no less than 7 days. Keep the concrete surface moist during the curing period and prohibit stacking or collision with the formwork.

[0308] (V) Working Principle

[0309] As a rigid constraint member at the top of the retaining piles, the capping beam, by increasing its cross-sectional size, configuring dense main reinforcement, and being cast integrally with the retaining piles, forms an "integrated pile-beam" force system. This transforms the independent force of each retaining pile into a synergistic force, effectively transferring and dispersing the lateral earth pressure borne by the retaining piles. Strengthening the reliable connection between the hoop and the main reinforcement of the retaining piles ensures that the shear force and bending moment at the pile top are effectively transferred to the capping beam, avoiding stress concentration at the pile-beam connection. The high-rigidity capping beam structure restricts the horizontal displacement and rotation of the top of the retaining piles, further enhancing the deformation resistance of the entire support system, suppressing pit deformation from the top constraint level, and ensuring the safety of the adjacent subway structure.

[0310] (vi) Implementation Results

[0311] In this embodiment, the 28-day compressive strength of the capping beam concrete reached 34.6 MPa, and the measured flexural bearing capacity was 1580 kN·m, meeting the design requirements. The maximum horizontal displacement of the top of the capping beam was 4.2 mm, and the vertical settlement was 2.5 mm, both controlled within the preset parameter range. Through the overall restraint effect of the capping beam, the horizontal displacement of the top of the support piles was reduced by 35% compared with the scheme without a capping beam, and the overall deformation of the foundation pit slope was more uniform, effectively ensuring the stability of the support system and providing safe conditions for subsequent earthwork excavation and anchor cable construction.

[0312] Example 8: Technical Solution for Automated Data Acquisition and Wireless Transmission in Intelligent Monitoring Systems

[0313] (I) Project Background

[0314] This embodiment demonstrates the core technology application of the intelligent monitoring system in the overall embodiment. Addressing the problems of data lag, low efficiency, and large errors in traditional manual monitoring, it focuses on the selection of automated monitoring equipment, the construction of a wireless transmission network, and real-time data acquisition technology. This enables second-level data acquisition, wireless uploading, and accurate transmission, ensuring the real-time nature of risk perception. The project overview is consistent with the overall embodiment.

[0315] (II) Structural Features and Assembly Relationships

[0316] Structural features of automated monitoring equipment:

[0317] Horizontal displacement monitoring equipment: adopts TS60 total station, with angle measurement accuracy ±0.5″, distance measurement accuracy ±(0.6mm+1ppm×D), supports automatic target recognition and continuous observation, and is equipped with lithium battery (battery life ≥8 hours).

[0318] Deep displacement monitoring equipment for piles: CX-03 inclinometer, measuring range ±30°, resolution 0.01°, sensitivity 0.001°, equipped with guide wheels, supports point-by-point measurement;

[0319] Wireless transmission equipment: adopts GPRS wireless transmission module (model DTU-800), supports TCP / IP protocol, transmission rate ≥115200bps, protection level IP68, and is suitable for harsh outdoor environments;

[0320] Data acquisition terminal: adopts an industrial-grade tablet computer (model IPAD-900), supports 4G network and WiFi connection, and has built-in monitoring data acquisition software.

[0321] Assembly relationship:

[0322] Total station installation: Set up 3 monitoring and control points (certified by the subway operator) in the stable area outside the foundation pit, install forced centering observation piers (1.2m high), and fix the total station on the observation piers to ensure good visibility;

[0323] Inclinometer tube installation: PVC-U inclinometer tubes (70mm in diameter, 5mm in wall thickness) are pre-embedded in the support pile body. The inclinometer tubes are connected by sockets and sealed. The bottom is embedded in stable rock layer ≥1m, and the top is 500mm above the cap beam. The guide groove is parallel to the edge of the foundation pit.

[0324] Transmission network setup: Monitoring equipment (total station, inclinometer, vibration sensor, etc.) are connected to the GPRS transmission module via RS485 interface. The transmission module is connected to the mobile 4G network to establish a communication connection with the BIM collaborative management platform server.

[0325] Data acquisition terminal: Project technicians are equipped with data acquisition terminals to access the BIM platform via WiFi or 4G network and view monitoring data and equipment status in real time.

[0326] (III) Parameters

[0327] Data collection parameters:

[0328] Horizontal displacement monitoring: Data is collected every 2 hours during the earthwork excavation stage and once a day after the support is completed. The data collection delay is ≤30s and the measurement error is ≤±2mm.

[0329] Deep displacement monitoring of pile body: The data collection interval is the same as that of horizontal displacement monitoring, the measurement interval is 500mm / point, the measurement time of a single hole is ≤5min, and the measurement error is ≤±0.1mm / m;

[0330] Vibration monitoring: Real-time acquisition, sampling rate 100Hz, transmission delay ≤10s, measurement error ≤±0.01cm / s;

[0331] Groundwater monitoring: The WL-2000 wireless water level gauge is used, with a measurement range of 0-50m, an accuracy of ±2cm, a data acquisition interval of once every 4 hours, and a transmission delay of ≤20s.

[0332] Wireless transmission parameters:

[0333] Transmission distance: GPRS module transmission distance in open environment ≥ 5km, in obstructed environment ≥ 1km;

[0334] Data packet loss rate: ≤0.5%;

[0335] Power supply parameters: The monitoring equipment is powered by solar energy (equipped with a 100W solar panel + 12V / 100Ah lithium battery), and can last for ≥7 days in continuous cloudy or rainy weather.

[0336] (iv) Construction / Usage Method

[0337] Equipment installation and commissioning:

[0338] Monitoring and control point layout: Three forced centering observation piers were set up according to the specifications. They were poured with concrete and cured for 7 days before the total station was installed. The layout of the plane control network was completed and verified.

[0339] Inclinometer tube pre-embedding: When fabricating the support pile reinforcement cage, the inclinometer tube is tied and fixed to the reinforcement cage to ensure that the verticality deviation is ≤0.5% and to prevent the inclinometer tube from shifting or being damaged during concrete pouring;

[0340] Equipment connection and debugging: Connect the monitoring device to the GPRS transmission module, configure communication parameters such as IP address and port number, test the stability of data transmission (no packet loss for 24 consecutive hours), and calibrate the measurement accuracy of the device;

[0341] Platform configuration: Set up the data acquisition task plan in the BIM platform, and define the data acquisition interval, data storage path and abnormal alarm rules.

[0342] Routine use and maintenance:

[0343] Data Acquisition: The equipment automatically collects data at preset intervals, uploads it to the BIM platform via the transmission module, and the platform automatically processes and generates trend curves;

[0344] Equipment inspection: Check the power supply status and signal strength of the transmission module of the monitoring equipment daily, clean the sensor probe and inclinometer tube weekly, and calibrate the measurement accuracy once a month;

[0345] Troubleshooting: When data transmission is interrupted, first check the transmission module signal and power supply, then check the device interface connection. Troubleshooting time is ≤2 hours.

[0346] (V) Working Principle

[0347] Automated monitoring equipment collects monitoring data in real time at preset intervals (e.g., a total station measures horizontal displacement using polar coordinates, and an inclinometer measures pile tilt angle using a gravity pendulum principle). The collected data is converted from analog to digital and then transmitted to a GPRS wireless transmission module. The transmission module packages the data and sends it to the BIM platform server via a 4G network. The server decodes, verifies, and stores the data, comparing it with preset thresholds. The platform displays monitoring data, trend curves, and equipment status in real time, triggering alerts when data anomalies occur. The entire process requires no manual intervention, achieving automatic data collection, wireless transmission, and real-time processing. This solves the problems of low efficiency and data lag in traditional manual monitoring, providing technical support for real-time risk perception.

[0348] (vi) Implementation Results

[0349] In this embodiment, the intelligent monitoring system collected over 80,000 data entries, with an average data transmission delay of 22 seconds, a data packet loss rate of 0.3%, and measurement errors all within acceptable limits. During the earthwork excavation phase, real-time monitoring detected two instances of abnormal deformation rates (daily displacements of 2.3 mm and 2.4 mm), prompting timely adjustments to the excavation schedule and preventing the triggering of yellow alerts. Compared to traditional manual monitoring, the data collection efficiency was increased by 80%, the monitoring frequency was increased by 3 times, and the risk identification lag time was shortened from 24 hours to within 30 seconds, significantly improving the real-time performance and accuracy of construction safety management.

[0350] Example 9: Technical Solution Supporting Orange Alert Emergency Response

[0351] (I) Project Background

[0352] This embodiment is a specific application of the orange alert emergency response in the overall embodiment. Addressing the need for rapid control of risk escalation during orange alerts (significant risk), it focuses on the triggering conditions for orange alerts, the encrypted monitoring scheme, and the specific implementation process for partial work stoppages, resolving the issues of vagueness and inadequate implementation in traditional orange alert response measures. The project overview is consistent with the overall embodiment.

[0353] (II) Structural Features and Assembly Relationships

[0354] Structural features of encrypted monitoring equipment:

[0355] Temporary monitoring equipment: The newly added TS06 total station (angle measurement accuracy ±1″, distance measurement accuracy ±(1mm+2ppm×D)) and portable inclinometer (model CX-10, measurement range ±30°, resolution 0.01°) are lightweight, portable and support rapid setup.

[0356] Monitoring markings: Red warning tape and warning signs (500mm×300mm) are used to delineate the areas where work is temporarily suspended.

[0357] Assembly relationship:

[0358] Temporary monitoring equipment deployment: Temporary total stations are set up at stable control points near the warning area, and portable inclinometers are used for intensified monitoring of deep displacement of key support piles. The equipment is stored in the project site duty room (≤30m from the edge of the foundation pit).

[0359] Work stoppage area delineation: Red warning tape is used to enclose the partial work stoppage area, and "Orange Warning, Partial Work Stoppage" warning signs are set up. The warning tape is ≥1m away from the edge of the foundation pit to ensure that construction personnel do not enter the warning area.

[0360] (III) Parameters

[0361] Orange alert triggering parameters (core indicators):

[0362] The daily variation in horizontal displacement of the top of the foundation pit slope is ≥3mm;

[0363] The cumulative settlement of the subway structure is ≥10mm;

[0364] Construction vibration velocity ≥ 0.2 cm / s;

[0365] The daily change in groundwater level is ≥100mm.

[0366] Encrypted monitoring parameters:

[0367] Monitoring frequency: Horizontal displacement and deep pile displacement are collected once every 1 hour; vibration monitoring is collected once every 30 minutes; and groundwater monitoring is collected once every 2 hours.

[0368] Monitoring duration: Encrypted monitoring continues until the data remains stable within the security threshold for three consecutive times and shows no upward trend;

[0369] Measurement accuracy: Temporary total station measurement error ≤ ±3mm, portable inclinometer measurement error ≤ ±0.2mm / m.

[0370] Partial shutdown parameters:

[0371] Work stoppage area: All construction activities (earthwork excavation, anchor cable tensioning, mechanical operations, etc.) within the warning area and a 5m radius around it.

[0372] Work stoppage duration: until the risk is eliminated, with a maximum of 48 hours (if the risk is not eliminated within 48 hours, it will be upgraded to a red alert).

[0373] (iv) Construction / Usage Method

[0374] Orange Alert Response Procedure:

[0375] Warning Triggering and Confirmation: After the BIM platform triggers an orange warning, the project's technical personnel will arrive at the site within 15 minutes to verify the authenticity of the warning data (check whether the monitoring equipment is normal and whether the monitoring points are damaged). After confirming that the warning is valid, they will immediately report to the project manager.

[0376] Partial work stoppage execution: The project manager issues a partial work stoppage order, and the construction team stops all work in the warning area and within a 5m radius around it, evacuates construction personnel and machinery, and uses red warning tape to enclose the work stoppage area and sets up warning signs;

[0377] Encrypted monitoring deployment: Technicians quickly set up temporary total stations and portable inclinometers, collect data at an encrypted monitoring frequency, and upload it to the BIM platform in real time, focusing on monitoring the changing trends of early warning indicators;

[0378] Risk Analysis and Handling: The technical manager organized a special meeting to analyze the causes of the early warning (such as excessively rapid earthwork excavation, loss of anchor cable prestress, etc.) and take targeted measures (such as slowing down the excavation speed, re-tensioning anchor cables, adding dewatering wells, etc.).

[0379] Risk Relief: When the encrypted monitoring data remains stable within the safety threshold for three consecutive times and the trend is stable, the technicians submit a risk relief application. After the supervisor approves the application, the warning tape is removed and construction in the non-warning area is resumed.

[0380] (V) Working Principle

[0381] The core of the orange alert is "rapid risk control and precise monitoring." When monitoring data reaches the orange alert threshold, partial work stoppages are implemented to prevent further disturbance of the soil and reduce the possibility of risk expansion. The intensified monitoring scheme increases the monitoring frequency and adds monitoring equipment to track the changing trends of risk indicators in real time, providing precise data support for risk analysis and handling. Targeted measures (such as slowing down excavation and supplementing tensioning) directly target the source of risk, quickly control the development of risk, and resume construction after the data stabilizes. This ensures safety while minimizing the impact on the overall construction progress.

[0382] (vi) Implementation Results

[0383] In this embodiment, an orange alert was triggered once during construction (daily change in horizontal displacement at the top of the foundation pit was 3.1 mm). After a partial work stoppage was implemented according to the above procedure, the increased monitoring data showed that the displacement rate gradually decreased. After 24 hours, the daily change in displacement dropped to 1.8 mm, and remained stable within the safety threshold for three consecutive times. The alert was successfully lifted and construction resumed. The orange alert response process was highly efficient, taking only 30 hours from alert triggering to risk resolution. It did not affect the subway structure, and the overall construction progress delay was controlled within one day, achieving a balance between safety and progress. This verified the practicality and reliability of the orange alert emergency response measures.

[0384] All aspects not detailed in this invention are conventional technical means known to those skilled in the art.

[0385] The above content shows and describes the basic principles, main features, and beneficial effects of the present invention. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or 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 foundation pit support and intelligent collaborative monitoring near a subway protection zone, characterized in that, It includes three main stages: the design and construction of the support structure, the deployment and operation of the intelligent monitoring system, and the processing and early warning response based on real-time monitoring data. The design and construction of the support structure adopts a pile-anchor support system optimized for the strict deformation control requirements of the subway protection zone. This system includes: constructing a row of large-diameter, small-spacing cast-in-place piles as vertical support components on the side of the foundation pit adjacent to the subway, with mesh and shotcrete between the piles to form a retaining surface; setting multiple high-strength prestressed anchor cables at different elevations of the piles to actively constrain the support piles and the soil behind them; and setting a capping beam at the top of the support piles to form an integral load-bearing structure. In the deployment and operation phase of the intelligent monitoring system, a multi-dimensional collaborative monitoring network covering deformation, dynamics, soil and water, and environment is constructed. The monitoring network includes at least a deformation monitoring module, a vibration monitoring module, a groundwater monitoring module, and an environmental monitoring module. Data from each monitoring module is integrated, visualized, and analyzed in a coordinated manner through a three-dimensional collaborative management platform built based on BIM technology. In the data processing and early warning response phase, safety thresholds and early warning thresholds for each monitoring indicator are pre-set in the management platform. After the monitoring data is transmitted to the platform in real time, the system automatically performs comparison and analysis. When the data reaches or exceeds the early warning threshold, a graded early warning signal is automatically triggered, and a preset emergency response procedure is initiated according to the early warning level, forming a closed-loop control of "monitoring-early warning-response".

2. The method for foundation pit support and intelligent collaborative monitoring near subway protection zones according to claim 1, characterized in that, The cast-in-place piles have a diameter of 1000mm, a length of 20m, and a center-to-center distance of 1.2m. The main reinforcement of the pile body consists of 21 HRB-400EΦ20 steel bars, with stirrups of Φ12@150, and the concrete strength grade is C30. A 100mm thick C20 fine aggregate concrete is sprayed between the piles, reinforced with Φ6@250×250 steel mesh.

3. The method for foundation pit support and intelligent collaborative monitoring in adjacent subway protection zones according to claim 1 or 2, characterized in that, The prestressed anchor cable is made of two steel strands with a nominal diameter of 15.2 mm and a standard strength value of 1860 MPa. The horizontal spacing is 2.5 m, the vertical spacing is 2.0 m, and the incident angle is 15-20°. The anchor cable grouting adopts a secondary pressure grouting process with a grouting pressure of not less than 1.5 MPa.

4. The method for foundation pit support and intelligent collaborative monitoring near subway protection zones according to claim 3, characterized in that, The deformation monitoring module specifically includes: horizontal displacement monitoring points set up at 5m intervals along the top of the slope of the foundation pit facing the subway, settlement monitoring points set up at 10m intervals around the subway structure and entrances and exits, and inclinometer tubes pre-embedded in the support piles; the monitoring frequency is no less than once a day during the earthwork excavation stage, and no less than twice a week during the use stage after the support structure is completed.

5. The method for foundation pit support and intelligent collaborative monitoring near subway protection zones according to claim 4, characterized in that, The vibration monitoring module sets a vibration velocity control threshold of 0.2 cm / s; the environmental monitoring module controls construction noise at a daytime level of ≤70 dB and a nighttime level of ≤55 dB, and the dust monitoring threshold during the structural construction phase is a PM10 concentration of ≤0.5 mg / m³.

6. The method for foundation pit support and intelligent collaborative monitoring in adjacent subway protection zones according to any one of claims 1, 2, 4, and 5, characterized in that, The BIM-based 3D collaborative management platform further integrates project progress management data to achieve linked analysis of construction progress and safety monitoring data; and connects to a large-volume concrete wireless temperature measurement system to monitor the temperature field of the support structure and surrounding soil in real time.

7. The method for foundation pit support and intelligent collaborative monitoring near subway protection zones according to claim 6, characterized in that, The tiered early warning mechanism includes at least three levels: yellow, orange, and red. Early warning information is automatically pushed to relevant responsible persons through pop-up windows on the management platform interface and SMS messages. When a red warning is triggered, the system prompts and requires the execution of emergency instructions to immediately stop construction, initiate prestressing compensation, or add temporary supports.

8. The method for foundation pit support and intelligent collaborative monitoring in adjacent subway protection zones according to any one of claims 1, 2, 4, 5, and 7, characterized in that, The capping beam has a cross-sectional dimension of 600mm×800mm, is cast integrally with the top of the support piles, and the main reinforcement of the support piles is effectively anchored to the capping beam.

9. The method for foundation pit support and intelligent collaborative monitoring near subway protection zones according to claim 8, characterized in that, The intelligent monitoring system uses automated monitoring equipment and a wireless transmission network, with a data acquisition delay of ≤30s.

10. The method for foundation pit support and intelligent collaborative monitoring in adjacent subway protection zones according to claim 7, characterized in that, When an orange alert is triggered, emergency measures such as increasing the frequency of monitoring and partially halting operations will be implemented.

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