BIM-based foundation pit support excavation quality control method and system

Abstract

The application discloses a kind of based on BIM's foundation pit support excavation quality control method and system, and the present application relates to foundation pit monitoring technical field, including the following steps: by arranging monitoring point in BIM model and storing theoretical deformation curve, with fixed frequency acquisition real-time deformation data;The deformation rate in preset sliding time window is used to judge rate step event and determine candidate source point, the deformation sequence cross-correlation function value of candidate source point and other monitoring points is calculated, and the initial source point of support deformation is judged in combination with time lag value;According to the relative quantity of initial source point, using time lag value decay gradient and deformation amplitude relative change rate or time lag variance analysis method, the quality defect type of foundation pit support is divided, and BIM model parameter or support erection state is updated, and theoretical deformation curve is recalculated to guide subsequent quality monitoring, greatly reduce the security risk caused by deformation, to ensure the safety and stability of construction.

Description

Technical Field

[0001] This invention relates to the field of foundation pit monitoring technology, specifically to a BIM-based method and system for quality control of foundation pit support excavation. Background Technology

[0002] In underground engineering construction, foundation pit support is a crucial step in ensuring construction safety and the stability of the surrounding environment. Especially in densely populated urban areas, the design and construction quality of foundation pit support directly impacts the safety of surrounding buildings and facilities. With the increasing prevalence of Building Information Modeling (BIM) technology, more and more engineering projects are adopting BIM as a fundamental tool for foundation pit support design and monitoring. Based on BIM's visualization and information-based features, the management efficiency and safety of foundation pit support can be effectively improved. However, how to monitor and evaluate the deformation of foundation pit support in real time during construction and promptly identify potential quality problems remains a pressing technical challenge.

[0003] Current technologies primarily rely on traditional monitoring methods, such as periodic monitoring using leveling instruments and deformation gauges. While these methods can reflect the deformation of the foundation pit support to some extent, they typically suffer from low monitoring frequency, delayed data processing, and poor timeliness. Furthermore, existing monitoring technologies often struggle to achieve comprehensive real-time monitoring in complex construction environments, especially when the support structure exhibits non-uniform deformation and localized damage, lacking effective identification and analysis methods. This makes it difficult to detect safety hazards during construction in a timely manner, thereby increasing construction risks.

[0004] Specifically, existing technologies cannot effectively integrate monitoring data with BIM models, resulting in a lack of scientific basis and real-time timeliness in the analysis and decision-making of monitoring information. This limitation makes it difficult to identify and address potential quality defects and deformation problems in a timely manner, which may lead to serious safety accidents and economic losses.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a BIM-based method and system for quality control of foundation pit support excavation, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A BIM-based method for quality control of foundation pit support excavation includes the following steps: In the BIM model, monitoring points are arranged along the support structure and the theoretical deformation curves of each point are stored. Real-time deformation of each monitoring point is collected synchronously at a fixed frequency. Based on the deformation rate of the monitoring point within the preset sliding time window, it is determined whether a rate step event has occurred at the monitoring point. The monitoring point where the rate step occurs is recorded as the research source point. Based on the deformation difference, it is determined whether the research source point is a candidate source point. The time when the candidate source point experiences a rate step is recorded as the reference zero point. The deformation sequence of all monitoring points within the preset time step is extracted. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, a cross-correlation function with a preset time delay value is set as the independent variable. The cross-correlation function values ​​between the deformation sequence of the candidate source point and the deformation sequence of each other monitoring point are calculated respectively. Multiple time delay values ​​are traversed to determine the maximum value of the cross-correlation function and the corresponding time delay value. Based on the matching results of the preset discrimination rules, all monitoring points are traversed to determine the initial source point of the support deformation. Based on the relative number of initial source points of support deformation, select the method for judging the quality of foundation pit support. If there is only a single initial source point of support deformation, the quality defects of foundation pit support are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the quality defects of foundation pit support are classified by using the time delay variance between monitoring points. Based on the identified types of defects in the foundation pit support quality, the BIM model is updated and the theoretical curves for each monitoring point are recalculated for subsequent foundation pit support excavation quality monitoring.

[0008] Furthermore, a three-dimensional geometric model of the foundation pit support structure is established in BIM software. The specific method for arranging monitoring points is to arrange monitoring points at equal intervals along the horizontal and vertical directions on the surface of the support structure, according to a preset distance. Vibrating wire strain gauges were installed at all monitoring points, and the data acquisition process was synchronized using GPS timing.

[0009] Furthermore, the deformation rate at each monitoring point is defined as the difference in deformation between two adjacent sampling times; The specific steps for determining whether a rate step has occurred at a monitoring point include: Within the sliding time window, for any monitoring point, determine its deformation at different sampling times, and calculate the deformation rate of the monitoring point at the remaining sampling times, excluding the first sampling time, within the sliding time window; Based on the deformation rate at the remaining sampling time, calculate the mean and standard deviation of the deformation rate at the monitoring point within the sliding time window, and calculate the coefficient of variation based on the mean and standard deviation of the deformation rate. The deformation rate of the monitoring point at the remaining sampling time is compared with the coefficient of variation. If there is a deformation rate that is not less than the coefficient of variation, it is determined that the monitoring point has experienced a rate step. Otherwise, the sliding time window is maintained to continuously monitor the deformation of the support structure. The coefficient of variation is specifically set as the sum of the mean deformation rate and three times the standard deviation. The logic for determining whether a research source point is a candidate source point is as follows: if the absolute difference between the actual deformation of the research source point and the theoretical deformation at the corresponding moment in the theoretical deformation curve is not less than the preset acceptable deformation threshold, then it is regarded as a candidate source point.

[0010] Furthermore, a cross-correlation function with time delay values ​​as independent variables is set. The cross-correlation function value is used to characterize the consistency of deformation trends. The specific logic of setting the cross-correlation function is as follows: taking the reference zero point as the focus of the preset time step, determining its start and end points according to the width of the preset time step, extracting the deformation sequences of all monitoring points within the preset time step, comparing the deformation sequences of candidate source points with the deformation sequences of the remaining monitoring points, and using the preset time delay value as the independent variable. The time delay value is specifically the amount of time change.

[0011] Furthermore, based on the width of the preset time step, the range of time delay values ​​is set. Within the range of time delay values, for any time delay value, it is input into the cross-correlation function to obtain the corresponding cross-correlation function value. All values ​​of time delay values ​​are traversed to determine the maximum cross-correlation function value, and the time delay value input to the maximum cross-correlation function value is recorded. Based on the maximum cross-correlation function value and its corresponding input time delay value, the initial source point of support deformation is determined according to a preset discrimination rule. The preset discrimination rule specifically includes: For any monitoring point other than the candidate source point, if the time delay value input to its maximum cross-correlation function value is less than 0, and the maximum cross-correlation function value is not less than the preset correlation threshold, then the monitoring point is taken as a new candidate source point, and the sum of the reference zero point and the input time delay value is taken as the new reference zero point.

[0012] Furthermore, all monitoring points are traversed to determine the initial source point of support deformation. The logic for determining the relative number of initial source points of support deformation is as follows: If the time delay value of the maximum cross-correlation function between the initial source point of support deformation and the other monitoring points is not less than the preset time delay threshold, then the relative number of initial source points of support deformation is determined to be 1, that is, there is only a single initial source point of support deformation. Otherwise, the initial source point of the support deformation is not unique; For a single initial source point of support deformation, the specific calculation method for the attenuation gradient of its time delay value is as follows: Calculate the shortest distance between each monitoring point and the initial source point of support deformation, arrange each monitoring point in ascending and descending order according to the shortest distance to obtain the ascending sequence and descending sequence of monitoring points, select the same number of monitoring points in the two sequences according to the sequence order to form a neighborhood point set and a non-neighborhood point set, extract the time delay value and shortest distance between the corresponding monitoring point and the initial source point of support deformation in the set, and calculate the average time delay value and average distance in the set respectively; The ratio of the difference between the average time delay value in the non-territory point set and the average time delay value in the neighborhood point set is used as the numerator, and the difference between the average distance in the non-territory point set and the average distance in the neighborhood point set is used as the denominator. The resulting ratio is used as the time delay value decay gradient. The specific method for calculating the relative rate of change of deformation amplitude is as follows: calculate the average rate of the initial source point of support deformation and all monitoring points at several sampling times after the step event, and take the ratio of the average rate of the initial source point of support deformation to the average rate of all monitoring points as the relative rate of change of deformation amplitude.

[0013] Furthermore, for a single initial source point of support deformation, if the relative rate of change of its deformation amplitude and the attenuation gradient of its time delay value are not greater than the preset judgment threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type. If the initial source of support deformation is not unique, calculate the time-delay variance between all pairs of monitoring points. If the time-delay variance is less than the preset variance threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type, and there are multiple local deformation deviations.

[0014] Furthermore, for local deformation deviation types, support frames are installed at the corresponding initial source point of support deformation, and the support status is added to the BIM model simultaneously, adjusting the theoretical deformation curves of each monitoring point under the support status. For global parameter deviation types, the soil parameters in the BIM model are corrected using the Bayesian inversion method. The soil parameters include deformation modulus and cohesion. Specifically, the difference between the predicted deformation value and the actual deformation value of the monitoring point output by the BIM model under different soil parameters is calculated using the Bayesian inversion method. The soil parameter combination with the smallest difference is then used to replace the soil parameters in the BIM model, and the theoretical deformation curve of each monitoring point is adjusted according to the replaced soil parameters.

[0015] This invention also provides a BIM-based quality control system for foundation pit support excavation, used to execute the above-mentioned BIM-based quality control method for foundation pit support excavation, comprising: The deformation monitoring module is used to arrange monitoring points along the support structure in the BIM model and store the theoretical deformation curves of each point. It synchronously collects the real-time deformation of each monitoring point at a fixed frequency and determines whether a rate step event has occurred at the monitoring point based on the deformation rate of the monitoring point within a preset sliding time window. The deformation correlation module is used to record the monitoring point where the rate step occurs as the research source point, and to determine whether the research source point is a candidate source point based on the deformation difference. The time when the candidate source point experiences a rate step is recorded as the reference zero point. The deformation sequence of all monitoring points within the preset time step is extracted. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, a cross-correlation function with a preset time delay value is set as the independent variable. The source point determination module is used to calculate the cross-correlation function value between the deformation sequence of the candidate source point and the deformation sequence of each other monitoring point, traverse multiple time delay values, determine the maximum value of the cross-correlation function and the corresponding time delay value, and determine the initial source point of the support deformation by traversing all monitoring points through the matching results of the preset discrimination rules. The defect classification module is used to select the method for judging the quality of the foundation pit support based on the relative number of initial source points of support deformation. If there is only a single initial source point of support deformation, the foundation pit support quality defects are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the foundation pit support quality defects are classified by using the time delay variance between monitoring points. The quality monitoring module is used to update the BIM model and recalculate the theoretical curves of each monitoring point based on the determined types of quality defects in the foundation pit support, so as to carry out subsequent quality monitoring of foundation pit support excavation.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention arranges monitoring points based on a BIM model and stores the theoretical deformation curves of each point. It synchronously collects real-time deformation data from the monitoring points at a fixed frequency, enabling timely capture of dynamic changes in the support structure. By pre-setting a sliding time window and deformation rate to determine rate step events, it ensures rapid identification of potential deformation problems, thus providing an effective means to deal with emergencies during actual construction. The monitoring point where the first rate step occurred was identified as the research source point. Subsequent candidate source point screening and cross-correlation analysis of deformation sequences will further improve the accuracy of deformation source point identification and provide a scientific basis for construction management. By traversing multiple time delay values ​​to determine the maximum cross-correlation function value, not only is the statistical analysis capability of monitoring data enhanced, but the location of deformation source points is also made more accurate. Compared with traditional monitoring methods, this scheme can more effectively handle complex construction environments and variable material properties, identify potential local and global quality defects, and significantly reduce safety hazards caused by deformation, thereby ensuring the safety and stability of construction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 The fitted curve of the decay gradient of time delay value versus the relative rate of change of deformation amplitude; Figure 3 This is a schematic diagram of the overall system structure of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example: Please see Figures 1-2 The present invention provides a technical solution: A BIM-based method for quality control of foundation pit support excavation includes the following steps: Step 1: Arrange monitoring points along the support structure in the BIM model and store the theoretical deformation curves of each point. Collect the real-time deformation of each monitoring point synchronously at a fixed frequency. Based on the deformation rate of the monitoring point within the preset sliding time window, determine whether a rate step event has occurred at the monitoring point.

[0021] In BIM software, a three-dimensional geometric model of the foundation pit support structure is established. The specific method for arranging monitoring points is to arrange monitoring points at equal intervals along the horizontal and vertical directions on the surface of the support structure, according to a preset distance. The specific method for establishing a 3D geometric model of the foundation pit support structure in BIM software is as follows: Determine the design parameters of the foundation pit support structure, including soil type, support method (e.g., diaphragm wall, anchor bolt support), construction depth, and construction technology. Set the spatial coordinate system of the foundation pit support structure. Use the planar drawing tools in the BIM software to draw the planar outline of the foundation pit according to the foundation pit design drawings. Use the 3D modeling tools in the BIM software to select specific components, such as walls and columns, to establish the support structure. Create supporting walls around the perimeter of the foundation pit outline, setting the wall thickness and height. Arrange monitoring points on the surface of the support structure according to design requirements and construction technology. The spacing of the monitoring points should be set according to actual needs, specifically, for example, arranging monitoring points at a horizontal spacing of 2.0m along the top capping beam of the diaphragm wall or the connecting beam at the top of the pile capping beam. The specific method for obtaining the theoretical deformation curves at each point is as follows: collect geological exploration data, including the physical and mechanical properties of the soil layer, such as compressive strength, shear strength, and deformation modulus; based on soil characteristics and support structure parameters, select theoretical models, such as the finite element method and slope stability analysis, to perform deformation analysis; and extract the deformation values ​​of each monitoring point at different time steps through numerical simulation results; these deformation values ​​constitute the theoretical deformation curves of the monitoring points.

[0022] Vibrating wire strain gauges were installed at all monitoring points, and the data acquisition process was synchronized using GPS timing. Vibrating wire strain gauges or fixed inclinometers are installed at all monitoring points. The data acquisition instrument uses GPS time synchronization and the sampling frequency is set to once per second for continuous recording.

[0023] The deformation rate at each monitoring point is defined as the difference in deformation between two adjacent sampling times; The specific steps for determining whether a rate step has occurred at a monitoring point include: Within the sliding time window, for any monitoring point, the deformation amount at different sampling times is determined, and the deformation rate of the monitoring point at the remaining sampling times, excluding the first sampling time, is calculated within the sliding time window; the sliding time window is generally set between 10 and 30 minutes.

[0024] The specific formula used to calculate the deformation rate at each monitoring point is as follows: In the formula, Let be the deformation rate of the i-th monitoring point at time t. Let be the deformation at the i-th monitoring point at time t. For the i-th monitoring point at Deformation at any given time. t represents the sampling time interval, t represents the time variable within the sliding time window, and i represents the index of the monitoring point.

[0025] Based on the deformation rate at the remaining sampling time, calculate the mean and standard deviation of the deformation rate at the monitoring point within the sliding time window, and calculate the coefficient of variation based on the mean and standard deviation of the deformation rate. The deformation rate of the monitoring point at the remaining sampling time is compared with the coefficient of variation. If there is a deformation rate that is not less than the coefficient of variation, it is determined that the monitoring point has experienced a rate step. Otherwise, the sliding time window is maintained to continuously monitor the deformation of the support structure. The coefficient of variation is specifically set as the sum of the mean deformation rate and three times the standard deviation. The specific formula used to calculate the coefficient of variation is as follows: In the formula, Let be the coefficient of variation of the i-th monitoring point in the p-th sliding time window. Let be the average deformation rate of the i-th monitoring point within the p-th sliding time window. Let be the standard deviation of the deformation rate of the i-th monitoring point within the p-th sliding time window; p is the index of the sliding time window; It should be noted that in engineering monitoring, especially in important projects such as foundation pit support structures, a high safety factor is necessary. By setting the standard deviation to 3 times, the early warning capability for potential risks can be effectively improved. Therefore, setting it to the mean plus 3 times the standard deviation can raise the detection standard for outliers, ensuring that the detected deformation rate changes are more significant and reducing the possibility of false alarms. By utilizing a sliding time window design, the deformation rate of monitoring points can be monitored and analyzed in real time, enabling timely responses to potential structural problems. When the deformation rate exceeds the coefficient of variation, a rate step event can be identified at the monitoring point, allowing for appropriate measures to be taken.

[0026] Step 2: Record the monitoring point where the rate step occurs as the research source point, and determine whether the research source point is a candidate source point based on the deformation difference. Record the time when the candidate source point experiences a rate step as the reference zero point. Extract the deformation sequence of all monitoring points within the preset time step. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, set the cross-correlation function with the preset time delay value as the independent variable.

[0027] The logic for determining whether a research source point is a candidate source point is as follows: if the absolute difference between the actual deformation of the research source point and the theoretical deformation at the corresponding moment in the theoretical deformation curve is not less than the preset acceptable deformation threshold, then it is regarded as a candidate source point.

[0028] The preset acceptable deformation threshold is determined based on the actual excavation process of the foundation pit and in combination with expert experience.

[0029] A cross-correlation function is set with time delay values ​​as the independent variable. The cross-correlation function value is used to characterize the consistency of deformation trends. The specific logic for setting the cross-correlation function is as follows: Using the reference zero point as the focus of a preset time step, the start and end points are determined based on the width of the preset time step. Deformation sequences of all monitoring points within the preset time step are extracted. The deformation sequences of candidate source points are compared with the deformation sequences of the remaining monitoring points. A preset time delay value is used as the independent variable, specifically the time change. The formula used to calculate the cross-correlation function is: In the formula, For a time delay value At time, the cross-correlation function value between the j-th monitoring point and the candidate source point, For candidate source points in The deformation value at time t. This represents the average deformation of the candidate source points within a preset time step. This indicates that the j-th monitoring point is at time [time]. The deformation value, Let k be the average deformation of the j-th monitoring point within a preset time step, and k be the width of the preset time step. For time-delay variables, The reference zero point is represented by j, which is the index of the remaining monitoring points excluding the candidate source point; where the time delay value variable... The specific setting depends on the preset time window width, and its absolute value is generally set between 0.5 and 0.8 of the time window width.

[0030] It should be noted that the cross-correlation function can quantify the synchronicity of deformation between candidate source points and other monitoring points, thereby understanding whether the impact of a rate step at a candidate source point is transmitted to other monitoring points, improving the assessment of the stability and overall safety of the support structure. When the cross-correlation function value is large, it indicates that the deformation trend of the candidate source point is highly consistent with the deformation trend of the monitoring points. This means that within a certain time period, the deformation changes of the candidate source point and the deformation changes of the monitoring points are synchronized, possibly caused by the same internal or external factors. Time delay value The settings are used to analyze the propagation delay of deformation effects. Deformation may have a time delay due to various factors, such as soil properties and structure. In this scheme, the time delay value is used to calculate the moment when the deformation of other monitoring points is similar to that of the candidate source point, and the time delay value is updated step by step. This is to determine when the same deformation occurs at other monitoring points, and based on the time delay value corresponding to the maximum cross-correlation function, to determine whether it lags behind or leads the current candidate source point.

[0031] Based on the width of the preset time step, set the range of time delay values. Within the range of time delay values, for any time delay value, input it into the cross-correlation function to obtain the corresponding cross-correlation function value. Iterate through all the time delay values ​​to determine the maximum cross-correlation function value and record the time delay value input to the maximum cross-correlation function value. Step 3: Calculate the cross-correlation function value between the candidate source point deformation sequence and the deformation sequence of each other monitoring point, traverse multiple time delay values, determine the maximum value of the cross-correlation function and the corresponding time delay value, and determine the initial source point of support deformation by traversing all monitoring points through the matching results of the preset discrimination rules.

[0032] The specific methods include: ensuring that deformation time series data for candidate source points and all monitoring points have been collected, and defining the relevant time steps and time delay value ranges; for each monitoring point other than the candidate source points... Iterate through the preset time delay values Calculate candidate source points and monitoring points Record the cross-correlation function values ​​between the monitoring points, including the maximum cross-correlation function value and the corresponding time delay value at that monitoring point. Based on the maximum cross-correlation function value and its corresponding input time delay value, the initial source point of support deformation is determined according to a preset discrimination rule. The preset discrimination rule specifically includes: For any monitoring point other than the candidate source point, if the time delay value input by its maximum cross-correlation function value is less than 0, and the maximum cross-correlation function value is not less than the preset correlation threshold, which is generally set to 0.7, then the monitoring point is regarded as a new candidate source point, and the sum of the reference zero point and the input time delay value is regarded as the new reference zero point.

[0033] It should be noted that when the time lag value is less than zero, it means that the deformation change of the monitoring point precedes that of the current candidate source point in time. This indicates that the deformation of the candidate source point may be caused by the deformation of the monitoring point. Therefore, the monitoring point may be the initial source point. Thus, the monitoring point is taken as the new candidate source point, and the sum of the reference zero point and the input time lag value is taken as the new reference zero point. In this way, the monitoring point that first reaches the corresponding deformation value is determined.

[0034] Step 4: Based on the relative number of initial source points of support deformation, select the method for judging the quality of foundation pit support. If there is only a single initial source point of support deformation, the quality defects of foundation pit support are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the quality defects of foundation pit support are classified by the time delay variance between monitoring points.

[0035] The process iterates through all monitoring points to determine the initial source point of support deformation, i.e., the candidate source points obtained after iterating through all monitoring points. The specific logic for determining the relative number of initial source points of support deformation is as follows: If the time delay value of the maximum cross-correlation function between the initial source point of support deformation and the other monitoring points is not less than the preset time delay threshold, then the relative number of initial source points of support deformation is determined to be 1, that is, there is only a single initial source point of support deformation. Otherwise, the initial source point of the support deformation is not unique; For a single initial source point of support deformation, the specific calculation method for the attenuation gradient of its time delay value is as follows: Calculate the shortest distance between each monitoring point and the initial source point of support deformation, arrange each monitoring point in ascending and descending order according to the shortest distance, and obtain the ascending sequence and descending sequence of monitoring points. Select the same number of monitoring points in the two sequences according to the sequence order, generally 10 monitoring points are selected to form a neighborhood point set and a non-neighborhood point set. Extract the time delay value and shortest distance between the corresponding monitoring point and the initial source point of support deformation in the set, and calculate the average time delay value and average distance in the set respectively. The ratio of the difference between the average time delay value in the non-territory point set and the average time delay value in the neighborhood point set is used as the numerator, and the difference between the average distance in the non-territory point set and the average distance in the neighborhood point set is used as the denominator. The resulting ratio is used as the time delay value decay gradient. The specific formula used to calculate the decay gradient of the time delay value is as follows: In the formula, The attenuation gradient is the time delay value of the initial source point of a single support deformation. The average time delay value of the neighborhood point set. The average time delay value of the non-neighborhood point set. The average distance of the neighborhood point set. The average distance of the set of non-neighboring points; It should be noted that the formula measures the change in deformation response speed by comparing the average time delay and average distance between neighboring points and non-neighboring points. If the average time delay of neighboring points is higher than that of non-neighboring points, and the difference in distance between them is large, it indicates that the deformation may be propagating slowly, which is usually related to localized plastic deformation. The larger the value, the slower the deformation propagation speed. Slow propagation usually corresponds to local plastic deformation, such as local collapse caused by over-excavation, rather than overall elastic response. The average time delay value of the neighborhood point set reflects the deformation response time of the monitoring points closer to the initial source point, while the average time delay value of the non-neighboring point set represents the deformation response delay of the monitoring points farther away. The larger the difference, the more it indicates that they are not deforming synchronously and that there is a deformation transmission effect.

[0036] The specific method for calculating the relative rate of change of deformation amplitude is as follows: calculate the average rate of the initial source point of support deformation and all monitoring points at several sampling times after the step event. Generally, 10 sampling times are selected, and the ratio of the average rate of the initial source point of support deformation to the average rate of all monitoring points is taken as the relative rate of change of deformation amplitude. The specific formula used to calculate the relative rate of change of deformation amplitude is as follows: In the formula, The relative rate of change of deformation amplitude at the initial source point of a single support deformation. The average velocity of the initial source point of deformation of a single support after a step event. The average rate of all monitoring points after the step event.

[0037] It should be noted that, The value reflects the comparison between the degree of deformation at the initial source point and the overall deformation, and is used to determine whether there is localized deformation concentration. The larger the value, the more intense the deformation at the source point while the deformation is very small elsewhere, which is a characteristic of localized concentrated deformation. For a single initial source point of support deformation, if the relative rate of change of its deformation amplitude and the attenuation gradient of its time lag value are both not greater than the preset judgment threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type. The preset judgment threshold includes the deformation amplitude judgment threshold and the attenuation gradient judgment threshold. The deformation amplitude judgment threshold is generally set between 1.2 and 3, and the attenuation gradient judgment threshold is generally set between 0.1 and 0.4.

[0038] If the initial source of support deformation is not unique, calculate the time-delay variance between all pairs of monitoring points. If the time-delay variance is less than the preset variance threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type, and there are multiple local deformation deviations.

[0039] The specific formula used to calculate the time delay variance between any two monitoring points is as follows: In the formula, For the time lag variance of the monitoring points, Let u be the total number of monitoring points and u be the index of each monitoring point. This is the time delay value input to the maximum cross-correlation function value between the i-th and u-th monitoring points at the time of a rate step event. The mean of the time delay values ​​input for the maximum cross-correlation function values ​​of all monitoring points; It should be noted that if the entire support structure deforms slowly due to soft soil parameters, then the time lags of all monitoring points relative to the same reference point should be very close, resulting in approximately equal time lag values ​​for all monitoring points, thus increasing the variance. Very small; If there are multiple local disturbances at different locations, the monitoring points near each disturbance source will deform before other points. In this case, the time lag of monitoring points in different disturbance areas relative to the same fixed reference source point will be significantly different, resulting in a larger time lag variance. Therefore, if the time lag variance is less than the preset variance threshold, the foundation pit support quality defect is judged to be of the global parameter deviation type; otherwise, the foundation pit support quality defect is judged to be of the local deformation deviation type, and there are multiple local deformation deviations. The preset variance threshold is set according to the actual monitoring accuracy and combined with expert experience.

[0040] Step 5: Based on the determined types of defects in the foundation pit support quality, update the BIM model and recalculate the theoretical curves for each monitoring point to conduct subsequent foundation pit support excavation quality monitoring.

[0041] For local deformation deviation types, support frames are installed at the corresponding initial source point of support deformation, and the support status is added to the BIM model simultaneously, and the theoretical deformation curves of each monitoring point under the support status are adjusted. Based on the preliminary analysis, the location of the initial deformation source point requiring support is determined, a support erection plan is formulated, and appropriate support types and materials are selected to ensure effective support and reduction of local deformation. Supports are erected on-site according to the design plan, and the status of support erection is added to the BIM model, including information such as support type, location, and load-bearing capacity. Based on the deformation theoretical model under support status, the theoretical deformation curves of each monitoring point are adjusted. This can be achieved by inputting support erection information and performing simulation calculations.

[0042] For global parameter deviation types, the soil parameters in the BIM model are corrected using the Bayesian inversion method. These soil parameters include deformation modulus and cohesion. Specifically, the difference between the predicted deformation values ​​and actual deformation values ​​at monitoring points output by the BIM model under different soil parameters is calculated using the Bayesian inversion method. The soil parameter combination with the smallest difference is then used to replace the soil parameters in the BIM model. The theoretical deformation curves of each monitoring point are adjusted based on the replaced soil parameters. This process includes: determining the soil parameters that need correction, including deformation modulus and cohesion, and preparing an initial parameter set; establishing an inversion model in the BIM model corresponding to the monitoring data; setting the input parameters and the predicted deformation values ​​at monitoring points output by the model; and using appropriate Bayesian methods. Inversion algorithms, such as Markov chain Monte Carlo methods, are used for parameter estimation. Through the inversion model, the difference between the predicted deformation values ​​at monitoring points and the actual measured deformation values ​​under different combinations of soil layer parameters is calculated. Minimizing this difference, such as using the least squares method, is employed to find the optimal combination of soil layer parameters that minimizes the difference between the model predictions and actual values. This optimal combination of soil layer parameters is then replaced in the BIM model to ensure that the model reflects the latest geological and soil conditions. Based on the replaced soil layer parameters, the theoretical deformation curves for each monitoring point are recalculated and adjusted. Based on the updated BIM model, a new monitoring plan is set up to continue tracking and monitoring the deformation of the foundation pit support.

[0043] Please see Figure 3 The present invention also provides a BIM-based quality control system for foundation pit support excavation, used to execute the above-mentioned BIM-based quality control method for foundation pit support excavation, comprising: The deformation monitoring module is used to arrange monitoring points along the support structure in the BIM model and store the theoretical deformation curves of each point. It synchronously collects the real-time deformation of each monitoring point at a fixed frequency and determines whether a rate step event has occurred at the monitoring point based on the deformation rate of the monitoring point within a preset sliding time window. The deformation correlation module is used to record the monitoring point where the rate step occurs as the research source point, and to determine whether the research source point is a candidate source point based on the deformation difference. The time when the candidate source point experiences a rate step is recorded as the reference zero point. The deformation sequence of all monitoring points within the preset time step is extracted. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, a cross-correlation function with a preset time delay value is set as the independent variable. The source point determination module is used to calculate the cross-correlation function value between the deformation sequence of the candidate source point and the deformation sequence of each other monitoring point, traverse multiple time delay values, determine the maximum value of the cross-correlation function and the corresponding time delay value, and determine the initial source point of the support deformation by traversing all monitoring points through the matching results of the preset discrimination rules. The defect classification module is used to select the method for judging the quality of the foundation pit support based on the relative number of initial source points of support deformation. If there is only a single initial source point of support deformation, the foundation pit support quality defects are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the foundation pit support quality defects are classified by using the time delay variance between monitoring points. The quality monitoring module is used to update the BIM model and recalculate the theoretical curves of each monitoring point based on the determined types of quality defects in the foundation pit support, so as to carry out subsequent quality monitoring of foundation pit support excavation.

[0044] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0045] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0046] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A BIM-based method for quality control of foundation pit support excavation, characterized in that, The specific steps include: In the BIM model, monitoring points are arranged along the support structure and the theoretical deformation curves of each point are stored. Real-time deformation of each monitoring point is collected synchronously at a fixed frequency. Based on the deformation rate of the monitoring point within the preset sliding time window, it is determined whether a rate step event has occurred at the monitoring point. The monitoring point where the rate step occurs is recorded as the research source point. Based on the deformation difference, it is determined whether the research source point is a candidate source point. The time when the candidate source point experiences a rate step is recorded as the reference zero point. The deformation sequence of all monitoring points within the preset time step is extracted. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, a cross-correlation function with a preset time delay value is set as the independent variable. The cross-correlation function values ​​between the deformation sequence of the candidate source point and the deformation sequence of each other monitoring point are calculated respectively. Multiple time delay values ​​are traversed to determine the maximum value of the cross-correlation function and the corresponding time delay value. Based on the matching results of the preset discrimination rules, all monitoring points are traversed to determine the initial source point of the support deformation. Based on the relative number of initial source points of support deformation, select the method for judging the quality of foundation pit support. If there is only a single initial source point of support deformation, the quality defects of foundation pit support are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the quality defects of foundation pit support are classified by using the time delay variance between monitoring points. Based on the identified types of defects in the foundation pit support quality, the BIM model is updated and the theoretical curves for each monitoring point are recalculated for subsequent foundation pit support excavation quality monitoring.

2. The method for quality control of foundation pit support excavation based on BIM according to claim 1, characterized in that: In BIM software, a three-dimensional geometric model of the foundation pit support structure is established. The specific method for arranging monitoring points is to arrange monitoring points at equal intervals along the horizontal and vertical directions on the surface of the support structure, according to a preset distance. Vibrating wire strain gauges were installed at all monitoring points, and the data acquisition process was synchronized using GPS timing.

3. The method for quality control of foundation pit support excavation based on BIM according to claim 2, characterized in that: The deformation rate at each monitoring point is defined as the difference in deformation between two adjacent sampling times; The specific steps for determining whether a rate step has occurred at a monitoring point include: Within the sliding time window, for any monitoring point, determine its deformation at different sampling times, and calculate the deformation rate of the monitoring point at the remaining sampling times, excluding the first sampling time, within the sliding time window; Based on the deformation rate at the remaining sampling time, calculate the mean and standard deviation of the deformation rate at the monitoring point within the sliding time window, and calculate the coefficient of variation based on the mean and standard deviation of the deformation rate. The deformation rate of the monitoring point at the remaining sampling time is compared with the coefficient of variation. If there is a deformation rate that is not less than the coefficient of variation, it is determined that the monitoring point has experienced a rate step. Otherwise, the sliding time window is maintained to continuously monitor the deformation of the support structure. The coefficient of variation is specifically set as the sum of the mean deformation rate and three times the standard deviation. The logic for determining whether a research source point is a candidate source point is as follows: if the absolute difference between the actual deformation of the research source point and the theoretical deformation at the corresponding moment in the theoretical deformation curve is not less than the preset acceptable deformation threshold, then it is regarded as a candidate source point.

4. The BIM-based method for quality control of foundation pit support excavation according to claim 2, characterized in that: A cross-correlation function is set with time delay values ​​as independent variables. The cross-correlation function value is used to characterize the consistency of deformation trends. The specific logic of setting the cross-correlation function is as follows: the reference zero point is used as the focus of the preset time step. The start and end points are determined according to the width of the preset time step. The deformation sequences of all monitoring points within the preset time step are extracted. The deformation sequences of the candidate source points are compared with the deformation sequences of the remaining monitoring points. The preset time delay value is used as the independent variable. The time delay value is specifically the amount of time change.

5. The BIM-based method for quality control of foundation pit support excavation according to claim 4, characterized in that: Based on the width of the preset time step, set the range of time delay values. Within the range of time delay values, for any time delay value, input it into the cross-correlation function to obtain the corresponding cross-correlation function value. Iterate through all the time delay values ​​to determine the maximum cross-correlation function value and record the time delay value input to the maximum cross-correlation function value. Based on the maximum cross-correlation function value and its corresponding input time delay value, the initial source point of support deformation is determined according to a preset discrimination rule. The preset discrimination rule specifically includes: For any monitoring point other than the candidate source point, if the time delay value input to its maximum cross-correlation function value is less than 0, and the maximum cross-correlation function value is not less than the preset correlation threshold, then the monitoring point is taken as a new candidate source point, and the sum of the reference zero point and the input time delay value is taken as the new reference zero point.

6. The BIM-based method for quality control of foundation pit support excavation according to claim 5, characterized in that: The process iterates through all monitoring points to determine the initial source point of support deformation. The logic for determining the relative number of initial source points of support deformation is as follows: If the time delay value of the maximum cross-correlation function between the initial source point of support deformation and the other monitoring points is not less than the preset time delay threshold, then the relative number of initial source points of support deformation is determined to be 1, that is, there is only a single initial source point of support deformation. Otherwise, the initial source point of the support deformation is not unique; For a single initial source point of support deformation, the specific calculation method for the attenuation gradient of its time delay value is as follows: Calculate the shortest distance between each monitoring point and the initial source point of support deformation, arrange each monitoring point in ascending and descending order according to the shortest distance to obtain the ascending sequence and descending sequence of monitoring points, select the same number of monitoring points in the two sequences according to the sequence order to form a neighborhood point set and a non-neighborhood point set, extract the time delay value and shortest distance between the corresponding monitoring point and the initial source point of support deformation in the set, and calculate the average time delay value and average distance in the set respectively; The ratio of the difference between the average time delay value in the non-territory point set and the average time delay value in the neighborhood point set is used as the numerator, and the difference between the average distance in the non-territory point set and the average distance in the neighborhood point set is used as the denominator. The resulting ratio is used as the time delay value decay gradient. The specific method for calculating the relative rate of change of deformation amplitude is as follows: calculate the average rate of the initial source point of support deformation and all monitoring points at several sampling times after the step event, and take the ratio of the average rate of the initial source point of support deformation to the average rate of all monitoring points as the relative rate of change of deformation amplitude.

7. The method for quality control of foundation pit support excavation based on BIM according to claim 6, characterized in that: For a single initial source point of support deformation, if the relative rate of change of its deformation amplitude and the attenuation gradient of its time delay value are not greater than the preset judgment threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type. If the initial source of support deformation is not unique, calculate the time-delay variance between all pairs of monitoring points. If the time-delay variance is less than the preset variance threshold, then the quality defect of the foundation pit support is judged to be of the global parameter deviation type; otherwise, the quality defect of the foundation pit support is judged to be of the local deformation deviation type, and there are multiple local deformation deviations.

8. The BIM-based method for quality control of foundation pit support excavation according to claim 7, characterized in that: For local deformation deviation types, support frames are installed at the corresponding initial source point of support deformation, and the support status is added to the BIM model simultaneously, and the theoretical deformation curves of each monitoring point under the support status are adjusted. For global parameter deviation types, the soil parameters in the BIM model are corrected using the Bayesian inversion method. The soil parameters include deformation modulus and cohesion. Specifically, the difference between the predicted deformation value and the actual deformation value of the monitoring point output by the BIM model under different soil parameters is calculated using the Bayesian inversion method. The soil parameter combination with the smallest difference is then used to replace the soil parameters in the BIM model, and the theoretical deformation curve of each monitoring point is adjusted according to the replaced soil parameters.

9. A BIM-based quality control system for foundation pit support excavation, used to execute the BIM-based quality control method for foundation pit support excavation as described in any one of claims 1-8, characterized in that, include: The deformation monitoring module is used to arrange monitoring points along the support structure in the BIM model and store the theoretical deformation curves of each point. It synchronously collects the real-time deformation of each monitoring point at a fixed frequency and determines whether a rate step event has occurred at the monitoring point based on the deformation rate of the monitoring point within a preset sliding time window. The deformation correlation module is used to record the monitoring point where the rate step occurs as the research source point, and to determine whether the research source point is a candidate source point based on the deformation difference. The time when the candidate source point experiences a rate step is recorded as the reference zero point. The deformation sequence of all monitoring points within the preset time step is extracted. Based on the correlation between the deformation sequences of the candidate source point and other monitoring points within the preset time step, a cross-correlation function with a preset time delay value is set as the independent variable. The source point determination module is used to calculate the cross-correlation function value between the deformation sequence of the candidate source point and the deformation sequence of each other monitoring point, traverse multiple time delay values, determine the maximum value of the cross-correlation function and the corresponding time delay value, and determine the initial source point of the support deformation by traversing all monitoring points through the matching results of the preset discrimination rules. The defect classification module is used to select the method for judging the quality of the foundation pit support based on the relative number of initial source points of support deformation. If there is only a single initial source point of support deformation, the foundation pit support quality defects are classified into local deformation deviation type or global parameter deviation type by using the attenuation gradient of time delay value and the relative change rate of deformation amplitude at the initial source point. Otherwise, the foundation pit support quality defects are classified by using the time delay variance between monitoring points. The quality monitoring module is used to update the BIM model and recalculate the theoretical curves of each monitoring point based on the determined types of quality defects in the foundation pit support, so as to carry out subsequent quality monitoring of foundation pit support excavation.

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