A method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment

Abstract

This invention discloses a method for controlling grouting in foundation pits based on multi-source data fusion and dynamic risk assessment, belonging to the fields of geotechnical engineering and foundation pit engineering technology. It includes: establishing a multi-source monitoring system to collect data on groundwater level, surface settlement, deep horizontal displacement, support axial force, and displacement rate; standardizing data based on preset control values ​​and then weighting and summing them to construct a comprehensive risk index, dynamically classifying risk levels from I to IV; dividing the foundation pit space into key deformation zones, general impact zones, and deformation-stable zones according to deformation and surrounding protection requirements; combining risk levels with spatial zoning to determine grouting pressure, grouting volume, and borehole spacing, and implementing grouting; updating data after grouting to reassess the risk and determine whether to continue grouting, forming a closed loop. This invention integrates multi-source monitoring data to achieve dynamic risk assessment and adaptive grouting control, solving the problems of monitoring fragmentation, static early warning, empirical estimation, and lack of closed-loop feedback, thus improving the safety and economy of foundation pit reinforcement.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and foundation pit engineering technology, specifically relating to a foundation pit grouting control method based on multi-source data fusion and dynamic risk assessment. Background Technology

[0002] With the accelerating pace of urbanization, the development of urban underground space is deepening, leading to increasingly larger and deeper foundation pit projects and more complex construction environments. Foundation pit projects involve numerous risk factors and complex construction procedures, making them highly susceptible to instability, resulting in project delays, economic losses, and even casualties. Grouting, as a crucial means of controlling foundation pit deformation and ensuring the safety of the foundation pit and its surrounding environment, has been widely used in foundation pit projects. However, existing foundation pit grouting control methods still have significant shortcomings in the following aspects: First, foundation pit monitoring methods are limited and lack effective integration of multi-source data. Traditional foundation pit monitoring mainly relies on single water level observations or manual measurements, which cannot obtain real-time and accurate information on the deformation, leakage, and dynamic changes in the seepage field of the foundation pit retaining structure. Existing monitoring methods rely on post-event data comparison, resulting in limited early warning and a lack of proactive management. Although some studies in recent years have attempted to introduce multi-source information into foundation pit risk early warning, these studies have mostly remained at the risk assessment level and have not yet effectively applied multi-source monitoring data to real-time decision-making for grouting control. There is a lack of organic connection between monitoring data and grouting control measures.

[0003] Second, foundation pit risk assessment lacks dynamism and comprehensiveness. Existing foundation pit risk early warning methods mainly rely on manual inspections and static threshold judgments, which suffer from shortcomings such as response lag and insufficient early warning accuracy. Most methods judge risk based solely on whether a single indicator (such as displacement) exceeds a preset threshold, failing to comprehensively consider the synergistic effects of multiple indicators such as groundwater level changes, surface settlement, retaining structure displacement, and support axial force. Furthermore, existing risk assessments are mostly one-off or intermittent assessments, lacking a dynamic update mechanism based on real-time monitoring data, making it difficult to reflect continuous changes in the foundation pit risk status in a timely manner.

[0004] Third, the determination of grouting parameters lacks specificity and adaptability. Existing grouting control methods rely heavily on engineering experience or rough estimations of single indicators to determine key parameters such as grouting pressure, grouting volume, and grouting hole spacing. There is a lack of systematic quantitative basis for determining which combination of grouting parameters should be used under different risk levels, and what differentiated grouting strategies should be adopted for different spatial areas. The concealed nature of grouting construction and the irregular and uneven diffusion of grout make it difficult for existing methods to dynamically adjust grouting parameters according to the risk level of different areas of the foundation pit. This results in either insufficient grouting reinforcement (ineffective deformation control) or excessive grouting reinforcement (leading to material waste and increased costs).

[0005] Fourth, the grouting process lacks real-time monitoring and feedback mechanisms. Existing grouting effect evaluation methods suffer from strong lag and insufficient representativeness, making it difficult to provide timely and effective guidance for on-site grouting construction. Current technologies lack effective real-time monitoring methods to determine whether grout leakage occurs, whether the actual grout diffusion range reaches expectations, and whether the grouting reinforcement achieves the target effect. After grouting is completed, there is often a lack of quantitative evaluation and closed-loop feedback of the grouting effect, making it impossible to decide whether to continue grouting or adjust the grouting plan based on the actual post-grouting effect, thus hindering the formation of a closed-loop control system of monitoring-evaluation-decision-implementation-re-evaluation.

[0006] In summary, existing methods for controlling foundation pit grouting have significant shortcomings in terms of monitoring data fusion, dynamic risk assessment, differentiated grouting decision-making, and real-time feedback of grouting effects. There is an urgent need for a full-process control method that can integrate multi-source monitoring data, dynamically assess foundation pit risks, and adaptively adjust grouting parameters accordingly. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a grouting control method for foundation pits based on multi-source data fusion and dynamic risk assessment. By integrating multi-source monitoring data such as groundwater level outside the pit, surface settlement, deep horizontal displacement of the retaining structure, axial force of the support, and deformation development rate, a foundation pit deformation risk assessment model is constructed to achieve dynamic identification and graded early warning of foundation pit deformation risk. Combined with the spatial zoning characteristics of the foundation pit, an adaptive adjustment mechanism for grouting parameters corresponding to different risk levels is established to achieve active control and precise reinforcement of foundation pit deformation.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment includes the following steps: S1. Establish a multi-source monitoring system for the foundation pit to collect data on changes in groundwater level outside the pit, surface settlement, deep horizontal displacement of the retaining structure, changes in support axial force, and the rate of change of deep horizontal displacement. S2. For each monitoring indicator collected in S1, standardize it based on the preset control value corresponding to each indicator to obtain the standardized value of each monitoring indicator. S3. Based on the standardized values ​​of each monitoring indicator and the corresponding weight indicators, a weighted sum is performed to construct a comprehensive risk index. Multiple numerical intervals are divided according to multiple preset thresholds. The numerical interval in which the comprehensive risk index is located is determined to identify the corresponding foundation pit risk level. S4. Based on the differences in monitoring data of different areas of the foundation pit and the requirements for environmental protection in the surrounding area, the foundation pit is spatially divided into a key deformation zone, a general impact zone, and a deformation stability zone. S5. Based on the risk level divided in S3 and the spatial partition divided in S4, combine each spatial partition with each risk level, determine the grouting parameters corresponding to each combination condition, and implement corresponding adaptive grouting reinforcement for the corresponding area under each combination condition. S6. After grouting reinforcement, update the monitoring data, recalculate the comprehensive risk index and reclassify the risk level. Determine whether to continue grouting based on the reclassified risk level to form a closed-loop control system.

[0009] As a further preferred embodiment of the present invention, the preset control value in S2 is the alarm limit value of each monitoring indicator pre-set during the foundation pit engineering design stage; the standardization process is as follows: the measured value of groundwater level change is divided by its control value, the measured value of surface settlement is divided by its control value, the measured value of deep horizontal displacement is divided by its control value, the measured value of support axial force change is divided by its control value, and the measured value of deep horizontal displacement change rate is divided by its control value to obtain the standardized value of each monitoring indicator.

[0010] As a further preferred embodiment of the present invention, the comprehensive risk index in S3 is obtained by weighting the standardized values ​​of each monitoring indicator and then summing them up, with the sum of the weights of each monitoring indicator being 1. In S3, the risk level of the foundation pit is divided into four levels: Level I risk, Level II risk, Level III risk, and Level IV risk, where Level I risk is the lowest risk level and Level IV risk is the highest risk level. The criteria for classifying the risk levels are as follows: when the comprehensive risk index is less than 0.70, it is classified as Level I risk; when the comprehensive risk index is greater than or equal to 0.70 and less than 0.85, it is classified as Level II risk; when the comprehensive risk index is greater than or equal to 0.85 and less than 1.00, it is classified as Level III risk; and when the comprehensive risk index is greater than or equal to 1.00, it is classified as Level IV risk.

[0011] As a further preferred embodiment of the present invention, in S3, when the rate of change of deep horizontal displacement within a continuous monitoring period exceeds 1.5 times the historical average rate, the current risk level is automatically increased by one level; if the current risk level is the highest, it remains unchanged.

[0012] As a further preferred embodiment of the present invention, S4 specifically includes: Acquire monitoring data for each area of ​​the foundation pit, and sort the cumulative values ​​of deep horizontal displacement at each monitoring point; Areas with a cumulative deep horizontal displacement of 40 mm or more and surrounding buildings or important pipelines that require special protection are designated as key deformation zones. Areas with a cumulative deep horizontal displacement value greater than or equal to 20 mm and less than 40 mm, and which are surrounded by buildings or pipelines with preset general protection requirements, are designated as general impact zones. Areas with a cumulative deep horizontal displacement of less than 20 mm and no surrounding buildings or pipelines requiring protection are designated as deformation-stable zones.

[0013] As a further preferred embodiment of the present invention, in S5, for the key deformation zone, the grouting parameters are determined as follows: When classified as Level II risk, the grouting pressure is 0.4 to 0.6 MPa, the grouting volume is 50 to 80 liters, and the grouting hole spacing is 2.0 meters; When classified as Level III risk, the grouting pressure is 0.6 to 1.0 MPa, the grouting volume is 80 to 100 liters, and the spacing between grouting holes is 1.5 meters. When classified as Level IV risk, the grouting pressure is 1.0 to 1.5 MPa, the grouting volume is 100 to 180 liters, and the grouting hole spacing is 1.0 meter; For areas of general influence, grouting parameters are determined as follows: When classified as Level II risk, the grouting pressure is 0.2 to 0.4 MPa, the grouting volume is 30 to 50 liters, and the spacing between grouting holes is 2.5 meters; When classified as Level III risk, the grouting pressure is 0.4 to 0.8 MPa, the grouting volume is 50 to 80 liters, and the spacing between grouting holes is 2.0 meters; When classified as Level IV risk, the grouting pressure is 0.8 to 1.0 MPa, the grouting volume is 80 to 120 liters, and the spacing between grouting holes is 1.5 meters.

[0014] As a further preferred embodiment of the present invention, in S5, earth pressure monitoring points are set up at different depths of the retaining structure; during the grouting process, the earth pressure changes at each depth are monitored in real time, and a response curve of grouting pressure-earth pressure increment-depth is established; when the ratio of the shallow earth pressure increment at 0-5m below the ground surface to the deep earth pressure increment at 10m below the ground surface exceeds 2.0, it is determined that grout has flowed along the side wall of the retaining structure, and the grouting pressure is immediately reduced to 60% of the current pressure and the grouting pipe depth is adjusted to 2-3m below the location where the flow occurred before grouting is restarted.

[0015] As a further preferred embodiment of the present invention, in S5, the grouting quantity in the grouting parameters is determined according to the compensation grouting quantity. The calculation method of the compensation grouting quantity is as follows: obtain the real-time cumulative settlement value of the surface settlement monitoring point within the grouting influence range, and at the same time, determine the predicted settlement value under the non-grouting condition based on the excavation depth, stratum parameters and previous deformation rate of the area, calculate the difference between the real-time cumulative settlement value and the predicted settlement value, and use the difference as the current undercompensation amount. The grouting volume is determined as follows: the grouting influence area and the formation volume expansion coefficient are obtained. The formation volume expansion coefficient is determined based on the soil compression modulus of the area. The under-compensation amount is multiplied by the grouting influence area and then by the formation volume expansion coefficient to obtain the foundation grouting volume. The foundation grouting volume is then multiplied by the over-compensation coefficient to obtain the final grouting volume. The over-compensation coefficient ranges from 1.2 to 1.5 and is used to offset the diffusion loss of grout to non-target areas. The grouting influence area is calculated and determined based on the grouting hole spacing and the designed diffusion radius of the grout.

[0016] As a further preferred embodiment of the present invention, in S5, temperature sensors are deployed in and around the area to be grouted to form a three-dimensional temperature monitoring network covering the grouting influence range; the three-dimensional temperature monitoring network is arranged radially in the horizontal direction with the grouting hole as the center, and in the depth direction, a layer of temperature sensors is deployed from the ground surface downwards at preset intervals. During the grouting process, the temperature monitoring network collects data on the temperature changes over time at each sensor in real time. Based on the initial temperature values ​​measured by each sensor before grouting, the temperature increment at each time after grouting is calculated, and the rate of temperature change at each location is calculated based on the temperature increment changes at adjacent time points. Locations where the temperature increment exceeds a preset temperature increment threshold or the temperature change rate exceeds a preset rate threshold are identified as locations affected by the thermal influence of the slurry; spatial interpolation is performed on all locations identified as affected by heat to form a thermal influence front of the slurry; the spatial envelope of the thermal influence front is used as the basis for determining the actual diffusion boundary of the slurry. When the actual diffusion boundary of the grout reaches the preset target reinforcement boundary in any direction, the grouting pressure is reduced and maintained for a preset grouting time after the pressure is reduced, so that the grout forms a compaction zone at the target reinforcement boundary and then the grouting stops.

[0017] As a further preferred embodiment of the present invention, the three-dimensional temperature monitoring network is arranged as follows: with the grouting hole as the center, temperature sensors are respectively arranged at distances of 0.5m, 1.0m, 1.5m, 2.0m, 2.5m and 3.0m from the wall of the grouting hole, and no less than 4 temperature sensors are evenly arranged in each layer along the circumference; in the depth direction, a temperature sensor is arranged every 1.0m from the ground surface until 3.0m below the bottom of the foundation pit; the spatial interpolation adopts the Kriging interpolation method or the inverse distance weighted interpolation method; the criterion for determining the compaction zone is: during the continuous grouting under the reduced grouting pressure, when the temperature change rate at the target reinforcement boundary drops to within 1.2 times the initial temperature change rate before grouting, the compaction zone is determined to have formed, and grouting is stopped.

[0018] The beneficial effects of this invention are as follows: 1. This invention establishes a multi-source monitoring system for foundation pits, simultaneously collecting multi-dimensional indicators such as changes in groundwater level outside the pit, surface settlement, deep horizontal displacement of the retaining structure, changes in axial force of the supports, and the rate of change of deep horizontal displacement. These indicators are standardized using preset control values ​​as a benchmark, ensuring comparability of monitoring data across different dimensions. Furthermore, a comprehensive risk index is constructed through weighted summation, organically integrating multiple monitoring indicators. This overcomes the shortcomings of traditional methods that rely on single indicators and suffer from fragmented information, providing a comprehensive and accurate data foundation for grouting decisions.

[0019] 2. This invention changes the existing static threshold judgment mode, dynamically classifying risk levels I to IV based on the numerical range of the comprehensive risk index, and introduces an abnormal deformation rate adjustment mechanism—automatically raising the risk level when the rate of change of deep horizontal displacement exceeds 1.5 times the historical average rate, enabling risk assessment to reflect the dynamic evolution trend of foundation pit deformation. Simultaneously, monitoring data is updated and the risk index is recalculated after grouting, achieving continuous tracking and real-time updates of risk status, effectively solving the problems of delayed response and insufficient early warning accuracy in existing methods.

[0020] 3. Based on the differences in monitoring data from various regions and the requirements of surrounding environmental protection, this invention divides the foundation pit space into key deformation zones, general impact zones, and deformation-stable zones. It then combines these spatial zones with risk levels, determining specific grouting pressure, grouting volume, and grouting hole spacing for different combinations, thus establishing a quantitative mapping relationship between risk level, spatial zone, and grouting parameters. This mechanism changes the traditional practice of relying on experience-based estimations, enabling precise matching of grouting reinforcement strength with the actual risk level of each zone, avoiding under- or over-reinforcement, ensuring both safety and cost savings.

[0021] 4. This invention monitors the changes in soil pressure at different depths of the retaining structure in real time during grouting, establishing a grouting pressure-soil pressure increment-depth response curve, enabling timely detection and handling of grout leakage accidents. Simultaneously, a temperature monitoring network tracks the grout's thermal impact front in real time, using the spatial envelope of the thermal impact front to determine the actual grout diffusion boundary. After reaching the target reinforcement boundary, the pressure is reduced to form a compaction zone before grouting is stopped, achieving visualized real-time monitoring of the grout diffusion range. Furthermore, the grouting volume is precisely calculated based on real-time settlement undercompensation, the formation volume expansion coefficient, and the overcompensation coefficient. After grouting, the risk is reassessed to determine whether to continue grouting, forming a complete closed-loop control system of monitoring-assessment-decision-grouting-reassessment, significantly improving the precision and reliability of grouting construction.

[0022] In summary, this invention effectively overcomes the shortcomings of existing foundation pit grouting control methods in terms of monitoring data fusion, dynamic risk assessment, differentiated grouting decision-making, and real-time feedback of grouting effects. It realizes intelligent and refined control of the entire process of foundation pit grouting reinforcement, which can significantly improve the safety and economy of foundation pit engineering. Attached Figure Description

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will now be described in detail and completely with reference to the accompanying drawings and preferred embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the present invention provides a method for controlling grouting in foundation pits based on multi-source data fusion and dynamic risk assessment, comprising the following steps executed sequentially: S1 to S6. The following detailed explanation of each step is provided using a specific engineering example (a deep foundation pit project with an excavation depth of 18m, a retaining structure consisting of a diaphragm wall with a thickness of 1.0m and a depth of 35m, surrounded by high-rise buildings and municipal pipelines).

[0026] I. Detailed Implementation of Step S1 S1. Establish a multi-source monitoring system for the foundation pit to collect data on changes in groundwater level outside the pit, surface settlement, deep horizontal displacement of the retaining structure, changes in support axial force, and the rate of change of deep horizontal displacement.

[0027] In this embodiment, according to the foundation pit design documents and monitoring specifications (such as the "Technical Standard for Monitoring of Building Foundation Pit Engineering" GB 50497), various monitoring instruments are deployed within the influence area of ​​the foundation pit: Groundwater level monitoring: Groundwater level observation wells are installed outside the pit, with a depth of 5m below the bottom of the pit. Automatic water level gauges are used to collect real-time water level changes, which are recorded as follows: (Unit: m), the sampling frequency is not less than 1 time / hour.

[0028] Surface settlement monitoring: Surface settlement observation points are set up around the perimeter of the foundation pit at 20m intervals. The cumulative settlement value at each point is obtained using an electronic level or a hydrostatic leveling system. (Unit: mm)

[0029] Horizontal displacement of the building envelope: Inclinometer tubes are pre-embedded within the building envelope. Using either a movable or fixed inclinometer, the horizontal displacement at different depths is measured, and the maximum displacement value among all measuring points below the top of the wall is recorded. (Unit: mm)

[0030] Support axial force variation: Install axial force gauges on the main supports (reinforced concrete supports or steel supports) to monitor the axial force variation in real time. (Unit: kN)

[0031] The rate of change of deep horizontal displacement is calculated by dividing the displacement difference between adjacent monitoring periods by the time interval, based on the inclinometer data. (Unit: mm / d).

[0032] All monitoring data are collected by automated data acquisition devices and sent to the central control platform. After preprocessing (filtering and noise reduction, outlier removal), the data is used as input variables for subsequent evaluation.

[0033] By establishing a multi-source monitoring system covering groundwater level, surface deformation, retaining structure displacement, support stress and deformation rate, a comprehensive real-time perception of the working status of the foundation pit was achieved. This overcomes the shortcomings of incomplete information in traditional single monitoring methods and provides a rich and reliable data foundation for subsequent risk quantification assessment.

[0034] II. Detailed Implementation of Step S2 S2. For each monitoring indicator collected in S1, standardize it based on the preset control value corresponding to each indicator to obtain the standardized value of each monitoring indicator.

[0035] The preset control values ​​are determined by the foundation pit design unit before construction based on geological conditions, environmental levels, and engineering experience, and serve as alarm limits for each monitoring indicator. In this embodiment, the control values ​​are as follows: Groundwater level change control values: Surface settlement control values: Deep horizontal displacement control values: Support axial force variation control value: Deep horizontal displacement rate control value: The standardization process uses the following formula: in, For the first The measured values ​​of each monitoring indicator This is the preset control value for this indicator. This is the corresponding standardized value (dimensionless).

[0036] Specifically, the standardized values ​​are calculated as follows: in, ~ These correspond to the standard values ​​for groundwater level, surface subsidence, deep horizontal displacement, change in support axial force, and displacement rate, respectively.

[0037] By normalizing based on the control value, the impact of differences in the dimensions and magnitudes of different monitoring indicators is eliminated, enabling the indicators to be compared and integrated on the same scale, thus creating a unified data foundation for subsequent weighted fusion.

[0038] III. Detailed Implementation of Step S3 S3. Based on the standardized values ​​of each monitoring indicator and the corresponding weight indicators, a weighted sum is performed to construct a comprehensive risk index. Multiple numerical intervals are divided according to multiple preset thresholds. The numerical interval in which the comprehensive risk index is located is determined to identify the corresponding foundation pit risk level.

[0039] (1) Calculation of comprehensive risk index Based on the importance of the project and expert experience, different weights were assigned to each monitoring indicator. ,satisfy In this embodiment, the weights are allocated as follows: groundwater level 0.15, surface settlement 0.25, deep horizontal displacement 0.30, support axial force 0.20, and displacement rate 0.10.

[0040] Overall Risk Index Calculate using the following formula: Right now: The higher the value, the higher the overall risk of the foundation pit.

[0041] (2) Risk level classification Based on a preset threshold, Divided into four numerical ranges, corresponding to four risk levels: when At that time, it was classified as Level I risk (low risk). when At that time, it was classified as Level II risk (medium risk). when At that time, it was classified as Level III risk (higher risk). when At that time, it was classified as Level IV risk (high risk).

[0042] (3) Deformation rate abnormal adjustment mechanism Within a continuous monitoring period (e.g., three consecutive periods), if the rate of change of deep horizontal displacement... Exceeding the historical average rate If the rate is 1.5 times higher than the average, the deformation acceleration is considered abnormal, and the currently calculated risk level is automatically increased by one level (if the current level is IV, it remains unchanged). For example, if the comprehensive risk index corresponds to level II, but the rate is abnormal, it will ultimately be classified as level III.

[0043] This step generates a comprehensive risk index through weighted fusion of multiple indicators, overcoming the limitations of single-indicator early warning. Simultaneously, it introduces a dynamic adjustment mechanism for deformation rate, enabling risk assessment to capture sudden accelerated deformation trends and improving the sensitivity and timeliness of early warning. The dynamically classified risk levels provide a clear and quantitative basis for subsequent grouting decisions.

[0044] IV. Detailed Implementation of Step S4 S4. Based on the differences in monitoring data of different areas of the foundation pit and the requirements for environmental protection in the surrounding area, the foundation pit is spatially divided into a key deformation zone, a general impact zone, and a deformation stability zone.

[0045] The specific division method is as follows: (1) Obtain the cumulative value of deep horizontal displacement in each area of ​​the foundation pit (divided by support segment or monitoring section). (j is the region number), and sort them.

[0046] (2) Based on the "Standard for Safety Assessment of Surrounding Environment of Foundation Pit Engineering" and design documents, determine the protection requirement level: Key deformation area: simultaneously meets the following two conditions—① ② The area is surrounded by buildings requiring special protection (such as high-rise residential buildings or ancient buildings) or important pipelines (such as gas lines or high-voltage cables). This area is designated as a key deformation zone.

[0047] General impact area: meets the requirements Furthermore, there are buildings or pipelines in the surrounding area that require general protection (such as ordinary multi-story buildings or rainwater pipes).

[0048] Deformation stability region: satisfies Furthermore, there are no buildings or pipelines in the vicinity that require protection.

[0049] In practical engineering, if a certain area experiences significant deformation but lacks surrounding protected objects, the zoning level can be appropriately lowered; conversely, if the deformation is minor but the protection requirements are extremely high, the zoning level can be appropriately raised. In this embodiment, the east side of the foundation pit is adjacent to a high-rise building, where the maximum inclinical displacement reaches 45mm, and is designated as a key deformation zone; the south side is adjacent to roads and pipelines, with a displacement of approximately 30mm, and is designated as a general impact zone; the west and north sides are open spaces, with a displacement of approximately 15mm, and are designated as deformation-stable zones.

[0050] Spatial zoning based on measured deformation values ​​and the importance of the protected objects achieves the refined goal of differentiated management of different areas, laying a spatial basis for subsequent customized grouting parameters for each zone, and avoiding waste or inadequacy caused by uniform reinforcement in a one-size-fits-all manner.

[0051] V. Detailed Implementation of Step S5 S5. Based on the risk levels defined in S3 and the spatial zones defined in S4, combine each spatial zone with each risk level, determine the grouting parameters corresponding to each combination condition, and implement corresponding adaptive grouting reinforcement for the corresponding areas under each combination condition.

[0052] This step is the core implementation phase, and it includes the following sub-items: 5.1 Determination of Grouting Parameters The risk levels (Levels I to IV, but Level I risks are usually not grouted, so only Levels II to IV are considered) are combined with spatial zones (key deformation zones and general impact zones) to form a total of 6 combinations. The grouting parameters (grouting pressure P, grouting volume Q, grouting hole spacing L) corresponding to each combination are determined according to Table 1 (no grouting is performed in the deformation stability zone).

[0053] Table 1 Grouting Parameter Combination Table During grouting, specific values ​​are selected within a given range based on actual geological conditions and construction experience. For example, in a key deformation zone with a risk level of III, a grouting pressure of 0.8 MPa, a grouting volume of 90 L, and a hole spacing of 1.5 m are selected.

[0054] 5.2 Refined Calculation of Grouting Volume (Compensation Grouting Volume Method) Regarding the grouting volume, in addition to selecting according to the range in Table 1, this invention also provides a calculation method based on real-time settlement compensation, which can accurately determine the grouting volume. The specific steps are as follows: (1) Calculate the amount of undercompensation: Obtain the real-time cumulative settlement value of surface settlement monitoring points within the grouting influence area. Simultaneously, based on the excavation depth, geological parameters (compression modulus, Poisson's ratio, etc.), and the initial deformation rate, the settlement value under the ungrouted condition is predicted using the Peck formula or numerical fitting method. Amount of unpaid compensation for: when When the actual settlement is greater than the predicted value, grouting compensation is required.

[0055] (2) Calculation of basic grouting volume: Obtain the grouting-affected area (Based on the grouting hole spacing and the designed diffusion radius of the grout) calculate, (or estimated according to specifications) and formation volume expansion coefficient (Based on soil compression modulus) Determined, usually (Unit: MPa⁻¹) Grouting volume of the foundation. for: (3) Final grouting volume: To account for the diffusion loss of slurry into non-target areas, an excess compensation coefficient is introduced. (Value range 1.2~1.5), final grouting volume: In this embodiment, a key deformation area Area affected Soil compression modulus ,but , ,Pick ,but The value falls within the corresponding range (50-80L) in Table 1, and is ultimately set to 50L.

[0056] 5.3 Real-time monitoring and handling of slurry leakage During the grouting process, in order to prevent grout from flowing along the side wall of the retaining structure (abnormal loss of grout or entry into unreinforced areas), this invention deploys earth pressure gauges at different depths of the retaining structure (such as 2m, 5m, 8m, 12m, 18m below the ground surface) to monitor the earth pressure increment at each depth in real time.

[0057] Establish grouting pressure -Increment of earth pressure -depth The response curve. When the shallow (0-5m) soil pressure increment... Increment of earth pressure in deep layers (below 10m) When the ratio exceeds 2.0, that is: If this indicates that grout is leaking along the sidewall (excessive shallow pressure indicates that grout is flowing upwards along the crack), immediate action should be taken: reduce the grouting pressure to 60% of the current value, and lower the grouting pipe to 2-3m below the location where the leak occurred for re-grouting to block the leaking channel and ensure that the grout effectively diffuses at the target depth.

[0058] 5.4 Real-time determination of grouting diffusion boundary based on temperature field monitoring To monitor the actual diffusion range of the grout in the formation in real time, this invention deploys a three-dimensional temperature monitoring network around the grouting hole. Specifically, temperature sensors are deployed at distances of 0.5m, 1.0m, 1.5m, 2.0m, 2.5m, and 3.0m from the hole wall, with four sensors evenly distributed circumferentially in each ring (a total of 24 horizontal measuring points). In the depth direction, a sensor is deployed every 1.0m from the ground surface, up to 3.0m below the bottom of the pit.

[0059] Before grouting, record the initial temperature of each sensor. During the grouting process, the temperature difference between the grout and the ambient temperature is used as the heat source, and the temperature at each measuring point is collected in real time. Calculate the temperature increment: Simultaneously, calculate the rate of temperature change: in, The sampling interval is denoted as .

[0060] Set temperature increment threshold (e.g., 2°C) and rate threshold (e.g., 0.5℃ / min). At a certain location or When the point is affected by the thermal influence of the slurry, it is determined that the point is affected by the thermal influence of the slurry. Spatial interpolation is performed on all affected points (using Kriging interpolation or inverse distance weighted interpolation) to generate the three-dimensional envelope of the thermal influence front of the slurry. This envelope is the actual diffusion boundary of the slurry.

[0061] When the actual diffusion boundary of the grout reaches the preset target reinforcement boundary (e.g., 1.8m from the grouting hole) in any direction, immediately reduce the grouting pressure to half of the current pressure (or adjust according to experience), and continue grouting at this low pressure for a period of time (e.g., 5-10 minutes). During this period, continuously monitor the temperature change rate at the target boundary. When the temperature change rate at the target boundary drops to within 1.2 times the initial temperature change rate before grouting (i.e., the background ground temperature change rate), that is: If the compaction zone has been formed (the grout has fully filled and compacted the soil), then grouting should be stopped.

[0062] This step quantifies and adaptively determines grouting parameters, avoiding the arbitrariness of empirical estimations. Real-time earth pressure monitoring promptly identifies and quickly addresses grout leakage incidents, improving construction safety. The three-dimensional diffusion boundary determination method based on temperature field monitoring overcomes the lag of traditional empirical estimations or post-operative core sampling verification, enabling real-time visual monitoring of grouting effects and ensuring precise control over the reinforcement range. Simultaneously, the compensating grouting volume formula directly links the grouting volume to actual deformation requirements, avoiding over-grouting or under-grouting, significantly improving the economy and reliability of grouting.

[0063] VI. Specific Implementation Method of Step S6 S6. After grouting reinforcement, update the monitoring data, recalculate the comprehensive risk index and reclassify the risk level. Determine whether to continue grouting based on the reclassified risk level to form a closed-loop control system.

[0064] After grouting is completed and the grout has initially set (usually 24–48 hours), real-time data for each monitoring indicator is collected again, and S2–S3 are repeated to calculate the comprehensive risk index after grouting. And reassess the risk level. If If it remains at Level III or IV (or if deformation anomalies still exist), then S5 should be executed again for supplementary grouting based on the new risk level and spatial zoning; if If the deformation rate drops to Level I or II and stabilizes, grouting can be suspended while monitoring continues.

[0065] In this embodiment, after the initial grouting in the key deformation zone, the deep horizontal displacement decreased from 45mm to 32mm, the comprehensive risk index decreased from 0.92 (Level III) to 0.78 (Level II), and the rate returned to normal. Therefore, grouting was stopped and the routine monitoring stage was entered.

[0066] By re-evaluating after grouting, a complete closed loop is formed: monitoring → evaluation → decision-making → grouting → re-monitoring → re-evaluation, ensuring that the risk of the foundation pit remains under control. This feedback mechanism overcomes the shortcomings of existing technologies, enabling dynamic adjustments to subsequent construction plans based on the actual reinforcement effect, thus enhancing the continuity and reliability of control.

[0067] VII. Verification of Typical Examples A deep foundation pit project in downtown Shanghai, with a depth of 17.95m, involved four concrete supports and was excavated in five layers. During the excavation of the third layer, monitoring data showed that the water level outside the pit had dropped by 2.1m, corresponding to a settlement of 43mm. The incline measurement of deep horizontal displacement inside the pit reached 48mm. The water level drop had reached the alarm threshold, and both the settlement and incline measurement outside the pit were close to the alarm values. After implementing this method of zoned grouting, the settlement and deep incline deformation were reduced by 35% compared to the expected values.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0069] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for controlling foundation pit grouting through multi-source data fusion and dynamic risk assessment, characterized in that, Includes the following steps: S1. Establish a multi-source monitoring system for the foundation pit to collect data on changes in groundwater level outside the pit, surface settlement, deep horizontal displacement of the retaining structure, changes in axial force of the support, and the rate of change of deep horizontal displacement. S2. For each monitoring indicator collected in S1, standardize it based on the preset control value corresponding to each indicator to obtain the standardized value of each monitoring indicator. S3. Based on the standardized values ​​of each monitoring indicator and the corresponding weight indicators, a weighted sum is performed to construct a comprehensive risk index. Multiple numerical intervals are divided according to multiple preset thresholds. The numerical interval in which the comprehensive risk index is located is determined to identify the corresponding foundation pit risk level. S4. Based on the differences in monitoring data of different areas of the foundation pit and the requirements for environmental protection in the surrounding area, the foundation pit is spatially divided into a key deformation zone, a general impact zone, and a deformation stability zone. S5. Based on the risk level divided in S3 and the spatial partition divided in S4, combine each spatial partition with each risk level, determine the grouting parameters corresponding to each combination condition, and implement corresponding adaptive grouting reinforcement for the corresponding area under each combination condition. S6. After grouting reinforcement, update the monitoring data, recalculate the comprehensive risk index and reclassify the risk level. Determine whether to continue grouting based on the reclassified risk level to form a closed-loop control system.

2. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: In S2, the preset control values ​​are the alarm limits of each monitoring indicator pre-set during the foundation pit engineering design stage; the standardization process is as follows: the measured values ​​of groundwater level change, surface settlement, deep horizontal displacement, support axial force change, and deep horizontal displacement rate change are divided by their control values ​​to obtain the standardized values ​​of each monitoring indicator.

3. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: The comprehensive risk index described in S3 is obtained by assigning weights to the standardized values ​​of each monitoring indicator and then summing them up. The sum of the weights of each monitoring indicator is 1. In S3, the risk level of the foundation pit is divided into four levels: Level I risk, Level II risk, Level III risk and Level IV risk, with Level I risk being the lowest risk level and Level IV risk being the highest risk level. The standard for classifying risk levels is as follows: when the comprehensive risk index is less than 0.70, it is classified as Level I risk; When the comprehensive risk index is greater than or equal to 0.70 and less than 0.85, it is classified as Level II risk; when the comprehensive risk index is greater than or equal to 0.85 and less than 1.00, it is classified as Level III risk; when the comprehensive risk index is greater than or equal to 1.00, it is classified as Level IV risk.

4. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: In S3, when the rate of change of deep horizontal displacement exceeds 1.5 times the historical average rate within a continuous monitoring period, the current risk level will be automatically increased by one level; if the current risk level is the highest, it will remain unchanged.

5. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: S4 specifically includes: Acquire monitoring data for each area of ​​the foundation pit, and sort the cumulative values ​​of deep horizontal displacement at each monitoring point; Areas with a cumulative deep horizontal displacement of 40 mm or more and surrounding buildings or important pipelines that require special protection are designated as key deformation zones. Areas with a cumulative deep horizontal displacement value greater than or equal to 20 mm and less than 40 mm, and which are surrounded by buildings or pipelines with preset general protection requirements, are designated as general impact zones. Areas with a cumulative deep horizontal displacement of less than 20 mm and no surrounding buildings or pipelines requiring protection are designated as deformation-stable zones.

6. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 3, characterized in that: In S5, for key deformation zones, the grouting parameters are determined as follows: When classified as Level II risk, the grouting pressure is 0.4 to 0.6 MPa, the grouting volume is 50 to 80 liters, and the grouting hole spacing is 2.0 meters; When classified as Level III risk, the grouting pressure is 0.6 to 1.0 MPa, the grouting volume is 80 to 100 liters, and the spacing between grouting holes is 1.5 meters. When classified as Level IV risk, the grouting pressure is 1.0 to 1.5 MPa, the grouting volume is 100 to 180 liters, and the grouting hole spacing is 1.0 meter; For areas of general influence, grouting parameters are determined as follows: When classified as Level II risk, the grouting pressure is 0.2 to 0.4 MPa, the grouting volume is 30 to 50 liters, and the spacing between grouting holes is 2.5 meters; When classified as Level III risk, the grouting pressure is 0.4 to 0.8 MPa, the grouting volume is 50 to 80 liters, and the spacing between grouting holes is 2.0 meters; When classified as Level IV risk, the grouting pressure is 0.8 to 1.0 MPa, the grouting volume is 80 to 120 liters, and the spacing between grouting holes is 1.5 meters.

7. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: In S5, earth pressure monitoring points are set up at different depths of the retaining structure. During the grouting process, the earth pressure changes at each depth are monitored in real time, and a response curve of grouting pressure-earth pressure increment-depth is established. When the ratio of the shallow earth pressure increment at 0-5m below the surface to the deep earth pressure increment at 10m below the surface exceeds 2.0, it is determined that grout has flowed along the side wall of the retaining structure. The grouting pressure is immediately reduced to 60% of the current pressure, and the grouting pipe depth is adjusted to 2-3m below the location where the flow occurred before grouting is restarted.

8. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: In S5, the grouting quantity in the grouting parameters is determined according to the compensation grouting quantity. The calculation method of the compensation grouting quantity is as follows: obtain the real-time cumulative settlement value of the surface settlement monitoring point within the grouting influence range, and at the same time, determine the predicted settlement value under the non-grouting condition based on the excavation depth, stratum parameters and previous deformation rate of the area, calculate the difference between the real-time cumulative settlement value and the predicted settlement value, and use the difference as the current undercompensation amount. The grouting volume is determined as follows: the grouting influence area and the formation volume expansion coefficient are obtained. The formation volume expansion coefficient is determined based on the soil compression modulus of the area. The under-compensation amount is multiplied by the grouting influence area and then by the formation volume expansion coefficient to obtain the foundation grouting volume. The foundation grouting volume is then multiplied by the over-compensation coefficient to obtain the final grouting volume. The over-compensation coefficient ranges from 1.2 to 1.5 and is used to offset the diffusion loss of grout to non-target areas. The grouting influence area is calculated and determined based on the grouting hole spacing and the designed diffusion radius of the grout.

9. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 1, characterized in that: In S5, temperature sensors are deployed in and around the grouting area to form a three-dimensional temperature monitoring network covering the grouting influence range. The three-dimensional temperature monitoring network is arranged radially in the horizontal direction with the grouting hole as the center, and in the depth direction, a layer of temperature sensors is deployed from the ground surface downwards at preset intervals. During the grouting process, the temperature monitoring network collects data on the temperature changes over time at each sensor in real time. Based on the initial temperature values ​​measured by each sensor before grouting, the temperature increment at each time after grouting is calculated, and the rate of temperature change at each location is calculated based on the temperature increment changes at adjacent time points. Locations where the temperature increment exceeds a preset temperature increment threshold or the temperature change rate exceeds a preset rate threshold are identified as locations affected by the thermal influence of the slurry; spatial interpolation is performed on all locations identified as affected by heat to form a thermal influence front of the slurry; the spatial envelope of the thermal influence front is used as the basis for determining the actual diffusion boundary of the slurry. When the actual diffusion boundary of the grout reaches the preset target reinforcement boundary in any direction, the grouting pressure is reduced and maintained for a preset grouting time after the pressure is reduced, so that the grout forms a compaction zone at the target reinforcement boundary and then the grouting stops.

10. The method for controlling foundation pit grouting based on multi-source data fusion and dynamic risk assessment according to claim 9, characterized in that: The three-dimensional temperature monitoring network is deployed as follows: with the grouting hole as the center, temperature sensors are deployed at distances of 0.5m, 1.0m, 1.5m, 2.0m, 2.5m, and 3.0m from the grouting hole wall, with no fewer than four temperature sensors evenly deployed circumferentially in each layer; in the depth direction, a temperature sensor is deployed every 1.0m from the ground surface until 3.0m below the bottom of the foundation pit; the spatial interpolation adopts Kriging interpolation or inverse distance weighted interpolation; the criterion for determining the compaction zone is: during continuous grouting under the reduced grouting pressure, when the rate of temperature change at the target reinforcement boundary drops to within 1.2 times the initial rate of temperature change before grouting, the compaction zone is determined to have formed, and grouting is stopped.

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