Deformation and stress intelligent monitoring system for deep foundation pit supporting structure

Abstract

The invention discloses an intelligent monitoring system for deformation and stress of a deep foundation pit supporting structure, relates to the technical field of deep foundation pit supporting monitoring, and is used for solving the problem of poor early warning of the deformation risk of the supporting structure. According to the method, high-density acquisition of inclination angle, deformation and stress data of a key area of a deep foundation pit supporting structure is realized by constructing a sensitivity-driven measuring point layout mechanism; the method comprises the following steps: constructing an inversion model based on stress and strain rates, obtaining a structural equivalent modulus, extracting a change rate of the structural equivalent modulus, judging a rigidity evolution trend, further constructing a modulus change rate space field, setting a region threshold by combining a disturbance sensitivity factor, realizing abnormal region identification and spatial positioning, and extracting structural response behavior information on the basis. And driving a system to trigger a grading response strategy according to an analysis result of the structure response behavior information, thereby realizing intelligent early warning of local deformation and stress instability of the deep foundation pit supporting structure.

Description

Technical Field

[0001] The present invention relates to the technical field of deep foundation pit support monitoring. More specifically, the present invention relates to an intelligent monitoring system for the deformation and stress of a deep foundation pit support structure composed of double-row piles and front bracing steel pipes. Background Art

[0002] The deep foundation pit support structure is an indispensable safety protection system in major projects such as urban underground space development, subway construction, and high-rise building foundation engineering. The scale, depth, and construction complexity of deep foundation pit projects are also increasing significantly. The support structure often faces multiple challenges such as higher loads, complex geological conditions, and interference from adjacent buildings. The double-row piles plus front bracing steel pipes is an efficient composite support structure form commonly used in deep foundation pit projects, suitable for complex foundation pit environments with loose soil layers, rich groundwater, or dense adjacent buildings. This structure consists of two rows of parallelly arranged reinforced concrete piles (front row piles and rear row piles) to form the main support system, and the lateral earth pressure is jointly borne by the intermediate soil mass to form a soil-pile synergistic effect. The front row piles usually directly bear the main load on the excavation face side, and the rear row piles play an auxiliary role in strengthening the overall stiffness and deformation control.

[0003] Deficiencies of the prior art: The monitoring of deep foundation pit support structures mostly focuses on the absolute value judgment of stress or deformation, while ignoring the dynamic coupling relationship between stress and strain, resulting in the inability to accurately identify behaviors such as sudden changes in structural stiffness, non-linear responses, or response lags. Moreover, existing monitoring systems usually rely on fixed thresholds for early warning, lacking trend analysis of the structural state evolution process. Especially in the initial stage of local damage, it is often difficult to detect in time, making the identification of dangerous areas in deep foundation pit support lag behind the actual risk development process, thereby having an adverse impact on the project. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, there are the following solutions to solve the problem of poor early warning of the deformation risk of the support structure in the above-mentioned background art.

[0005] To achieve the above object, the present invention provides the following technical solutions: An intelligent monitoring system for the deformation and stress of a deep foundation pit support structure, including a support data acquisition module, a structural stiffness trend analysis module, an abnormal area identification module, and a grading strategy adjustment module, and the modules are connected by signals; The support data acquisition module is used to collect the deformation and stress monitoring data of the deep foundation pit support structure, determine the high-density layout area, and deploy the collection of tilt angle data in the high-density layout area; The structural stiffness trend analysis module is used to establish an inversion relationship based on the real-time stress change rate and strain rate of the structure, obtain the current equivalent modulus of the structure, extract the equivalent modulus change sequence to determine the modulus equivalent change rate, and judge the structural stiffness evolution trend; The abnormal area identification module is used to construct a modulus change rate field based on the equivalent modulus change rate, and set a partition threshold in combination with the perturbation sensitivity factor to identify and spatially locate the abnormal area of the structure; The grading strategy adjustment module is used to obtain the structural behavior information generated in the abnormal area and analyze it after spatially locating the abnormal area of the structure, and trigger a grading response strategy according to the results of the structural behavior analysis.

[0006] In a preferred embodiment, it is used to collect the deformation and stress monitoring data of the deep foundation pit support structure, determine the key measurement area, and deploy the collection of tilt angle data in the key measurement area. The specific steps are as follows: According to the theoretical principal stress ratio of the support structure position, the response intensity of perturbation or unloading, and the importance coefficient of the influence of local instability or failure of the structure on the overall structural safety, use the layout density distribution function to determine the key measurement area; In the key measurement area, use fiber Bragg grating strain sensors and laser displacement sensors to collect structural deformation data in real time, use Brillouin optical fiber stress sensors to collect data, and calculate the stress by inverse calculation of the measurement frequency change to obtain stress data. Deploy MEMS inclinometers for real-time monitoring to obtain the tilt angle data of the structural nodes.

[0007] In a preferred embodiment, it is used to establish an inversion relationship based on the real-time stress change rate and strain rate of the structure to obtain the current equivalent modulus of the structure. The specific steps include: Perform a first-order difference calculation on the strain data and stress data to obtain the structural strain rate and stress change rate; Determine the equivalent modulus according to the local approximate linear instantaneous response relationship between the structural strain rate and stress change rate on the continuous time series.

[0008] In a preferred embodiment, extract the equivalent modulus change sequence to determine the modulus equivalent change rate and judge the structural stiffness evolution trend. The specific steps are as follows: Determine the support structure according to the equivalent modulus change amplitude; If the equivalent modulus change amplitude is in a steady state, the support structure is in the normal elastic response stage; If the equivalent modulus shows a rapid decline, the support structure is in the non-linear, degraded or unstable stage; Obtain the equivalent modulus sequence obtained by the inversion process, and use the first derivative of the equivalent modulus with respect to time as the equivalent modulus change rate; Determine the structural stiffness evolution trend according to the change rate of the equivalent modulus.

[0009] In a preferred embodiment, determining the structural stiffness evolution trend according to the change rate of the equivalent modulus includes the following steps: If the change rate of the equivalent modulus is less than 0, it indicates that the stiffness of the deep foundation pit support structure is in a weakening trend. If the absolute value of the change rate of the equivalent modulus increases, it indicates a discontinuous trend in the stiffness evolution of the deep foundation pit support structure, and structural state mutations or external interference events are likely to occur. If the change rate of the equivalent modulus remains unchanged, it indicates that the structural stiffness maintains a stable trend and is in the safe response stage.

[0010] In a preferred embodiment, used to construct a modulus change rate field according to the change rate of the equivalent modulus, and set a partition threshold in combination with the disturbance sensitivity factor to identify and spatially locate the abnormal area of the structure. The specific steps are as follows: Merge the monitoring positions of the deep foundation pit support structure and the change rate of the equivalent modulus into a measurement point set. Use local structure-related interpolation to perform spatial interpolation on the measurement point set to determine the modulus change rate values of different monitoring points, and construct a modulus change rate spatial field according to the modulus change rate values. Set a regional modulus change rate determination threshold and compare it with the modulus change rate value to determine whether there is an abnormal change in the current state of the support structure.

[0011] In a preferred embodiment, set a regional modulus change rate determination threshold and compare it with the modulus change rate value to determine whether there is an abnormal change in the current state of the support structure. The specific steps are as follows: If the modulus change rate value exceeds the modulus change rate determination threshold, it indicates that there is a risk of abnormal structural performance in the detection area, and it is marked as an abnormal area. After performing the judgment on all monitoring points, generate a structural stiffness anomaly distribution map, mark the identified abnormal areas, and form a spatial anomaly mask layer or risk heat map.

[0012] In a preferred embodiment, used to obtain and analyze the structural behavior information generated in the abnormal area after spatially locating the structural abnormal area. The specific steps are as follows: Obtain the structural behavior information generated in the abnormal area after spatially locating the abnormal area of the structural modulus change. The structural behavior information includes a structural response distortion index and a structural response hysteresis index. The structural response distortion index represents the degree of deviation between the actual force response of the structure and the design theory response. The structural response hysteresis index represents the degree of time delay of the structural stress-strain response relative to the strain input; Compare and analyze the structural response distortion threshold and the structural response hysteresis threshold with the structural response distortion index and the structural response hysteresis index respectively.

[0013] In a preferred embodiment, a hierarchical response strategy is triggered according to the results of structural behavior analysis, and the specific steps are as follows: When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, the support structure does not need to be adjusted and continuous monitoring is maintained; When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, the overall structure is still in a fluctuating state, and the frequency of the change trend of the monitored support structure area is increased; When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, the data acquisition frequency is increased for key long-term monitoring; When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, it is necessary to immediately trigger an alarm and take measures such as strengthening detection or emergency assessment.

[0014] Technical effects and advantages of the intelligent monitoring system for the deformation and stress of the deep foundation pit support structure of the present invention: The present invention realizes the accurate acquisition of the inclination angle, deformation and stress data of the key areas of the deep foundation pit support structure by constructing a high-density measuring point layout mechanism based on sensitivity distribution analysis; establishes a dynamic inversion model based on the stress change rate and the strain rate, obtains the structural equivalent modulus in real time and extracts its change sequence to judge the structural stiffness evolution trend; further constructs a spatial field of the modulus change rate, fuses the disturbance sensitivity factor to set the regional judgment threshold, and realizes the accurate identification and spatial positioning of abnormal areas; based on the identified abnormal areas of the modulus change, extracts the structural response behavior information, calculates the structural response distortion and hysteresis characteristics, evaluates the local nonlinear and hysteretic energy dissipation behavior, and finally drives the structural intelligent monitoring system to trigger the response grading strategy, improving the timeliness and accuracy of the risk identification of the deep foundation pit support structure, thereby realizing the early warning and dynamic control of the local instability trend of the deep foundation pit support structure. Brief Description of the Drawings

[0015] Figure 1 It is a schematic structural diagram of the intelligent monitoring system for the deformation and stress of the deep foundation pit support structure of the present invention. Detailed Embodiments

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] To achieve the above object, Figure 1 The structural schematic diagram of the intelligent monitoring system for the deformation and stress of the deep foundation pit support structure of the present invention is given, which specifically includes a support data acquisition module, a structural stiffness trend analysis module, an abnormal area identification module, and a grading strategy adjustment module. The modules are connected by signals; The support data acquisition module is used to collect the deformation and stress monitoring data of the deep foundation pit support structure, determine the high-density layout area, and deploy the acquisition of tilt angle data in the high-density layout area; The structural stiffness trend analysis module is used to establish an inversion relationship based on the real-time stress change rate and strain rate of the structure, obtain the current equivalent modulus of the structure, extract the equivalent modulus change sequence to determine the modulus equivalent change rate, and judge the structural stiffness evolution trend; The abnormal area identification module is used to construct a modulus change rate field according to the equivalent modulus change rate, set a partition threshold in combination with the disturbance sensitivity factor, and perform the identification and spatial positioning of the structural abnormal area; The grading strategy adjustment module is used to obtain the structural behavior information generated in the abnormal area and analyze it after the spatial positioning of the structural abnormal area, and trigger a grading response strategy according to the results of the structural behavior analysis.

[0018] Step 1: Collect the deformation and stress monitoring data of the double-row pile plus front bracing steel pipe deep foundation pit support structure, obtain the real-time deformation and stress data of the support structure, and construct the deformation field and stress field of the support structure. The specific steps are as follows: Affected by the soil body and the construction process, there are obvious spatial differences in the stress concentration area and the deformation sensitive area of the support structure. According to the distribution law of the theoretical stress and deformation of the support structure and the finite element analysis results, determine the high-sensitivity conditions in different areas of the support structure as the key measurement areas of the support structure; According to the theoretical analysis and finite element simulation, predict the spatial sensitive distribution law of stress and strain. The specific process is as follows; The stress and strain dominant regions are divided according to the supporting structure type (such as row piles, diaphragm walls, supporting beams, and cut-off curtains) and construction stages (excavation, support installation, backfilling, etc.). First, the stress path of the structural system is analyzed to determine the stress and strain concentration regions of each component under typical working conditions. Theoretically, stress concentrations are likely to occur at the bottom corners of the structure, pile tops, turning points, etc., and the strain response is sensitive in the structural turning regions, boundary regions, etc. Through the analysis of these key structural features at the structural mechanics level, a preliminary sensitive zoning framework is obtained. The finite element simulation analysis is based on the in-situ geological parameters, structural design parameters, and excavation construction stages. A two-dimensional or three-dimensional finite element analysis model is constructed, typical load conditions (such as lateral earth pressure, self-weight, support reaction force, etc.) are set, and a linear or nonlinear constitutive model is used for simulation calculation to obtain the principal stress distribution field and principal strain distribution field of different regions of the structure at each stage. Based on the theoretical analysis and finite element simulation, the measuring point layout density distribution function is established as: , where represents the proportion of the theoretical principal stress at the position x of the supporting structure, obtained from finite element simulation or code-recommended values, with a numerical range of 0 to 1; represents the response intensity to disturbance or unloading at the position x, usually calculated and determined according to the structural stiffness and load distribution characteristics; represents the importance coefficient of the influence of local instability or failure of the structure on the overall structural safety, obtained through empirical formulas or expert evaluations. Higher values are given to key nodes such as corners, joints, and adjacent to columns; f represents the operation function; A specific example is as follows: The measuring point layout density distribution function is: , , , are the layout strategy weight coefficients of each parameter, used to adjust the influence degree of different factors in the layout decision-making, satisfying the normalization condition ; Assume that , used to emphasize the stress concentration area; , used to consider the geological inhomogeneity; , ensure key coverage, and for the bottom corners of the structure, obtained by simulation; respectively obtain , , are 0.9, 0.6, 1.0, and substituting into the measuring point layout density distribution function, the calculated value is 0.83; It shows that the measuring point density value of this point is 0.83, belonging to the high-density layout area, that is, the key measurement area. High-precision multi-source sensors should be preferentially arranged in the key measurement area.

[0019] Precisely measure and calculate the deformed data. During the construction period and service period of the support structure, displacement and strain may occur. Therefore, it is necessary to collect the structural deformation data in real time to reflect the dynamic behavior state of the structure. High-precision fiber Bragg grating strain sensors (FBG) and laser displacement sensors are used for collaborative measurement: When the structure deforms, the fiber Bragg grating undergoes strain, which is manifested as a change in the reflection center wavelength. The wavelength change is obtained through precise demodulation measurement, and then the structural strain is calculated: , where is the wavelength change measured by the sensor in real time; is the strain calibration coefficient, calibrated in the laboratory; is the initial wavelength of the fiber Bragg grating; The laser sensor accurately measures the surface displacement of the structure based on the triangulation principle, and reflects the displacement change of the whole or part of the structure in real time: , where is the initial calibration distance determined during installation; is the real-time distance measured actually; The two types of sensors are cooperated with each other to provide deformation information with multiple scales and multiple precisions, and form a deformation data set.

[0020] Carry out real-time measurement and calculation of the structural stress data. That is, the internal stress change of the structure is an important basis for judging the structural stability. Therefore, it is necessary to synchronously monitor the internal stress of the key areas of the structure, and use Brillouin optical fiber stress sensors for real-time measurement. The stress data is obtained by back-calculating the stress through measuring the frequency change; The change in the overall inclination of the support structure can indirectly reflect the stress state and potential instability trend of the structure. Therefore, MEMS inclinometers are deployed at key nodes for real-time monitoring, and the inclination angles of the structural nodes are calculated.

[0021] The inclination angle data, deformation data and stress data are jointly used for the joint evaluation of the overall state of the support structure.

[0022] Perform high-precision time synchronization and data adaptive compensation calibration on the collected sensor data.

[0023] Step 2: Carry out joint inversion of the deformation rate and stress change. According to the internal physical relationship between the stress and deformation data, analyze the dynamic evolution law of the actual bearing characteristics and safety performance of the support structure. The specific steps are as follows: Establish the combined inversion relationship of stress and strain rate. In the safety state assessment of deep foundation pit support structures, the actual stiffness of the structure is an important evaluation index. Since the actual stiffness of the on-site structure cannot be directly measured, indirect inversion technology is used. Based on the principles of elasticity mechanics, the current equivalent stiffness parameters of the structure are dynamically deduced through the real-time stress change rate and strain rate data of the structure, so as to reflect the actual bearing capacity and deformation characteristics of the structure; Extract the effective information of the structure change rate, perform a first-order difference calculation on the strain and stress data to obtain the structure strain rate and the stress change rate ; For any moment t in the continuous time series, assume that the instantaneous response relationship of the support structure at this moment is locally approximately linear, that is, the response of the stress change to the current strain rate approximately satisfies the following relationship: , where is the equivalent modulus of the support structure at the t-th moment; Rewrite it as an expression of the equivalent modulus: , where is a very small positive value to avoid numerical instability when the denominator approaches zero; The real-time state quantity of the structure stiffness (i.e., the equivalent modulus ) reflects the current bearing capacity of the structure, and the continuous-time change trend of this quantity reveals the evolution process of the structure stiffness. If the support structure is in the normal elastic response stage, the change range of its equivalent modulus should be relatively stable; if the equivalent modulus shows a rapid decline or short-term violent fluctuation, it usually indicates that the structure has entered the non-linear, degenerated or unstable stage; Obtain the equivalent modulus sequence obtained through dynamic inversion processing: , this modulus sequence corresponds to the discrete time points , where is the data sampling period to ensure the unified alignment of the time axis; The equivalent modulus change rate is defined as the first-order derivative with respect to time, and its discrete expression form is: , where represents the modulus evolution rate at the moment , that is, the change amount of the structure stiffness per unit time; If , it means that the stiffness of the deep foundation pit support structure is in a weakening trend, which may be due to cracks in the support members, soil unloading causing structural loosening, etc.; If suddenly increases, it means that the stiffness evolution of the deep foundation pit support structure is discontinuous, and it is necessary to pay attention to whether there is a sudden change in the structure state or an external interference event; If , it indicates that the structural stiffness maintains a stable trend and is in the safe response stage.

[0024] According to the sensitive data obtained on the changing trend of structural stiffness, local deterioration phenomena of the structure are captured in advance.

[0025] In deep foundation pit engineering, the safety risks of the retaining structure often first appear in local areas, such as corner areas, connection nodes, backfill boundaries, etc. Due to the local superposition of factors such as construction disturbance, geological inhomogeneity, and soil unloading, the structural stiffness is prone to sudden or continuous decline; Through the analysis of the modulus change rate, the stiffness change trends of each measuring point on the time axis have been obtained. A spatial recognition mechanism for abnormal modulus changes is constructed to identify the areas with sudden stiffness drops, hotspots of change trends, and abnormal propagation paths, and to conduct risk positioning and zonal early warning in space. The specific steps are as follows: Define the modulus change rate value G(x, y, t) in the two-dimensional spatial domain. Its construction method is to perform spatial interpolation on the measuring point set and use the local structure-related interpolation kernel to construct as follows: , where is the modulus change rate of the i-th measuring point; is the local weighted kernel function; is the weight adjustment coefficient related to the local structure type of the measuring point (the weight can be amplified in areas such as connection areas and pile tops); is the i-th monitoring position of the deep foundation pit retaining structure, represents the Euclidean space distance operation; The output modulus change rate value is a continuous spatio-temporal modulus change rate function, which can be used to construct a stiffness anomaly heat map, a combined regional threshold model for anomaly determination, etc.; By performing spatial interpolation on the dynamic modulus change rates at discrete measuring points, a continuous function field is constructed. The constructed modulus change rate spatial field determines the stiffness evolution trends of the deep foundation pit retaining structure at different times and different spatial positions. This spatial field can identify local stiffness drop areas and abnormal propagation paths of stiffness fluctuations.

[0026] The spatial function embeds and expands a physical structure of traditional RBF or spline interpolation by analyzing the inhomogeneity of the structural topology and geological conditions, and can more realistically restore the physical propagation characteristics of abnormal trends.

[0027] In the safety monitoring of the support structure, if only the rate of modulus change itself is used for global unified anomaly judgment, the design rationality differences and safety tolerance differences in different regions may be ignored. For example, in the support bottom corner area, due to structural stress redistribution and uneven foundation, a relatively large range of modulus fluctuations may be allowed, while in the structural corner or the area near high-risk construction units, the structure is extremely sensitive to stiffness changes, and even a small change may trigger structural imbalance. Therefore, the threshold of the rate of modulus change with regional differentiation discrimination ability is constructed to determine the abnormal area, and the specific process is as follows: Define the regional threshold for judging the rate of modulus change as: , where is the structural reference tolerance coefficient, which is a global adjustment parameter and reflects the average acceptance amplitude of the overall structure design for modulus fluctuations; is the theoretical modulus field provided by the structural design drawing or finite element model, which is used to define the stiffness baseline of each point. For example, it is set to 30 GPa at the pile top and may be 20 GPa in the middle of the wall, reflecting the quantitative expectation of the design model for the performance of different structural units; is the disturbance sensitivity factor, and its value range is [0, 1]; The constructed regional threshold for judging the rate of modulus change reflects the maximum allowable rate of modulus change at this position. Its design logic is that a relatively larger fluctuation range is allowed in the areas with a high stiffness baseline (such as structural piles and end trusses), and the overall threshold decreases in the disturbance-sensitive or key structural areas, making the monitoring more stringent. Moreover, the regional threshold for judging the rate of modulus change is not a constant, but changes with the spatial position, reflecting the actual needs of structural design and engineering environment.

[0028] After completing the construction of the spatial field of the rate of modulus change (i.e., clarifying the speed of stiffness change in each region of the structure at a certain moment) and the establishment of the regional modulus change judgment threshold field (i.e., the maximum allowable change rate at each spatial position), a logical judgment relationship is established between the two to identify whether there is an abnormal change in the current state of the support structure. The specific steps are as follows: Compare the value of the rate of modulus change with the modulus change judgment threshold point by point. That is, for each spatial position in the structural monitoring area, the system will automatically compare the value of the rate of modulus change at this position at the current moment with the modulus change judgment threshold corresponding to this position. If the value of the rate of modulus change exceeds the modulus change judgment threshold, it means that the stiffness change in this area has exceeded the acceptable range, indicating that there is a risk of abnormal structural performance at this position, and it is marked as an abnormal area; After performing the above judgment on all monitoring points, the system generates a structural stiffness anomaly distribution map. On this map, the areas identified as abnormal will be marked, forming a spatial anomaly mask layer or risk heat map, showing the areas where the local stiffness of the structure decays or fluctuates violently; In addition, the identification results of abnormal areas will also serve as one of the feedback conditions of the intelligent monitoring system to adjust the subsequent data sampling strategy. The system will give priority to increasing the monitoring frequency of these areas, activating redundant sensor nodes, and forming a spatially adaptive data collection mechanism, thereby achieving efficient resource allocation and dynamic risk focusing.

[0029] It should be noted that the structural benchmark tolerance coefficient is usually set according to the stiffness reduction limit index in the underground engineering structure design code, and the recommended value range is 0.02 to 0.10; the disturbance sensitivity factor can be constructed by combining the following information: geological disturbance level (such as 0.8 for weak clay areas and 0.2 for bedrock areas), surrounding construction activity density (such as large values for areas close to temporary buildings and traffic load sources), structural node characteristics (such as artificially amplifying the sensitivity of key structural unit nodes), support historical stability records (evaluating the fluctuation intensity based on the trend of the historical rate standard deviation curve), and the final disturbance sensitivity factor can be obtained by normalized superposition.

[0030] Step 3: Identify the structural response distortion, that is, identify the abnormal response area of the structure by analyzing the difference between the actual response behavior (stress-strain relationship) of the structure and the ideal theoretical response of the structure. The specific steps are as follows: After completing the stiffness change rate and spatial abnormal area identification, further analyze whether there is an abnormal stress-deformation behavior pattern in the local response of the structure, and obtain the structural behavior information generated by the abnormal area process after the abnormal area of structural modulus change is spatially located. The structural behavior information includes the structural response distortion index and the structural response hysteresis index. The structural response distortion index is an indicator used to quantify the degree of deviation between the actual force response of the structure and the design theoretical response. The structural response distortion index measures whether the structure has a nonlinear distortion behavior of the stress-strain rate response relationship at a certain moment. Under ideal conditions, the stress change of the support structure should show a stable and linear correspondence with the strain rate, and the ratio is close to the elastic modulus set in the structural design stage. However, during the construction or operation of deep foundation pits, the actual response of the structure may gradually deviate from this ideal relationship due to factors such as crack initiation, node loosening, component yielding or load mutation, showing abnormal phenomena such as sudden drop in stiffness, drastic response fluctuations or uneven deformation. The structural response distortion index is proposed in this context. It comprehensively measures this deviation by simultaneously considering multiple physical dimensions such as stress-strain rate ratio deviation, strain acceleration and dynamic stiffness fluctuations. The main object of measurement of the structural response distortion index is the response consistency between structural stiffness and deformation. The larger its value, the more significant the deviation of the current stress behavior of the structure from its theoretical design, indicating that the structure may be undergoing a non-linear response or damage development stage. The structural response distortion index can not only be used to identify local problems such as stiffness mutation, non-linear yield, and shear relaxation, but also capture early the trend of small but continuous stiffness disturbances. The introduction of the structural response distortion index enables the monitoring system to identify potential risks starting from the response behavior pattern rather than simply numerical anomalies, thus playing a key role in the intelligent early warning of deep foundation pit support structures and being used in the active identification scenarios of continuous evolution of structural performance and precursors of local instability; The steps to obtain the structural response distortion index are as follows: Obtain the historical stress sequence and strain time sequence read by the stress sensors in the abnormal area, and obtain the stress values at the current time point t and the next moment which are respectively 、 , and calculate the stress change rate: ; Obtain the strain values at the current time point t and the next moment which are respectively 、 , and calculate the strain rate: , and obtain the strain acceleration as: ; Calculate the abnormal equivalent modulus according to the strain rate and stress change rate at the current time point t, and the calculation expression is: , calculate the abnormal modulus fluctuation value between the two adjacent moments before and after the current moment: , obtain the theoretical modulus of the abnormal area, and calculate the structural response distortion index, and the calculation expression is: .

[0031] It should be noted that the theoretical modulus of the abnormal area is obtained from the deep foundation pit support structure design drawings, specification standards or finite element models. If it is a spatially distributed modulus, a corresponding modulus value can be set at each measuring point position and used as a static input item during the implementation process for comparison with the dynamic monitoring results.

[0032] The structural response hysteresis index is a time series index used to quantify whether there are obvious hysteresis and energy dissipation characteristics in the stress-strain response process of a structure. Its meaning is to measure whether there is a time delay, inconsistent path or inelastic hysteretic behavior in the stress response of the structure relative to the strain input within a certain time window. Under ideal elastic conditions, the stress of the structure should respond synchronously with the change of strain, and the loading and unloading paths should be exactly the same. However, in actual deep foundation pit support structures, factors such as soil disturbance, contact nonlinearity, interaction between the structure and soil, and local slip will cause the stress response to lag behind the strain or generate a hysteresis loop, manifested as energy loss and stiffness degradation; The structural response hysteresis index accumulates the magnitude of the stress response deviating from the linear relationship within the historical time window through integration, and at the same time combines the deviation between the true stress work per unit volume and the theoretical elastic work, comprehensively reflecting the degree of hysteresis and energy dissipation of the structure. What this index measures is the dynamic consistency and dissipation ability of the structural response process. The larger its value, the more it indicates that the structure not only deviates from the linear relationship, but may also be experiencing significant hysteretic response, shear slip, yield energy dissipation or contact loosening and other phenomena; The role of the structural response hysteresis index is to reveal historical degradation behaviors that are difficult to identify through instantaneous stiffness indicators, and is particularly suitable for analyzing the performance evolution trend of structures under long-term load or multiple disturbance conditions, enabling the monitoring system to identify the hidden risk state of the structure that seems stable but is actually hysteretic, providing key support for accurate early warning and early identification of delayed failure.

[0033] The acquisition logic of the structural response hysteresis index is as follows: Obtain the stress change rate at the moment and the strain rate in the abnormal area, construct a sliding time window with a local length of 2n + 1, and use the least squares method to calculate the fitting slope between the stress change rate and the strain rate as the local elastic modulus. The calculation formula is: where n represents the half-width of the fitting window; Within the hysteresis analysis time window , use the trapezoidal method to calculate the actual stress work within the time window to obtain the stress work: . Similarly, calculate the theoretical stress input work within the time window to obtain the calculated elastic work: where is the time window width of the hysteresis analysis; calculate the structural response hysteresis index: .

[0034] It should be noted that the stress change rate and strain rate of the structural response hysteresis index are obtained in the same way as those of the structural response distortion index; n represents the half-width of the fitting window, that is, Taking n sampling points before and after the center, a total of 2n + 1 points are used for least squares fitting; the total number of sampling moments within the time window is set according to the actual sampling requirements.

[0035] Set the structural response distortion threshold to judge whether there is an abnormal deviation in the stiffness response at the monitoring position at any moment, and set the structural response hysteresis threshold to judge whether there is obvious hysteretic behavior or energy dissipation process in the structure within a period of time, and conduct comparative analysis with the structural response distortion index and the structural response hysteresis index respectively; When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, it indicates that the ratio of the real-time stress-strain rate of the structure is close to its design modulus, indicating that there is no stiffness mutation or response nonlinearity in the structure. Therefore, the structural response distortion index is within the normal range. At the same time, the structure shows good response synchronization within the hysteresis analysis time window, and the deviation between the historical stress work and the theoretical elastic work is small.

[0036] When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, it indicates that the stress response of the structure at the current moment has deviated significantly from the theoretical design modulus, and there are phenomena such as local stiffness drop, microcrack development or response path mutation. Therefore, the structural response distortion index has exceeded the normal range. However, since the structural response hysteresis index is still lower than the hysteresis threshold, it indicates that this deviation behavior has not formed an obvious energy dissipation process or hysteresis accumulation, and the overall structure is still in a short-term fluctuation state. Increase the frequency of monitoring the change trend in this area; When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, it indicates that the current stiffness of the structure still remains near the design modulus and there is no instantaneous response deviation. Therefore, the structural response distortion index is in a normal state. However, within the hysteresis analysis time window, the structure shows obvious energy dissipation behavior, and there is a continuous deviation between the stress work and the elastic work, indicating that there are phenomena such as plastic slip, soil decoupling or contact interface creep. This state indicates that although there is no immediate stiffness mutation in the structure, it may be in a process of slow damage accumulation. Then increase the data acquisition frequency and it needs to be included in key long-term monitoring; When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, it indicates that the stress-strain response relationship of the structure not only deviates from the design modulus, showing obvious stiffness mismatch and nonlinear characteristics, but also there are significant response energy dissipation and path inconsistency within the hysteresis analysis time window, indicating that the structure is experiencing a double abnormal state of sudden inelastic behavior and hysteresis accumulation. At this time, high vigilance should be exercised as the structure may be at the local yield, contact failure or instability boundary, and it is necessary to immediately trigger an alarm and take measures to strengthen detection or emergency assessment.

[0037] In summary, the present invention realizes the accurate acquisition of the inclination angle, deformation and stress data of the key areas of the deep foundation pit support structure by constructing a high-density measuring point layout mechanism based on sensitivity distribution analysis; establishes a dynamic inversion model based on the stress change rate and strain rate to obtain the equivalent modulus of the structure in real time and extract its change sequence, and judges the evolution trend of the structural stiffness; further constructs a spatial field of the modulus change rate, fuses the disturbance sensitivity factor to set the regional judgment threshold, and realizes the accurate identification and spatial positioning of abnormal areas; based on the identified abnormal areas of the modulus change, extracts the structural response behavior information, calculates the structural response distortion and hysteresis characteristics, evaluates the local nonlinear and hysteretic energy dissipation behaviors, and finally drives the structural intelligent monitoring system to trigger the response grading strategy, improving the timeliness and accuracy of the risk identification of the deep foundation pit support structure, thereby realizing the early warning and dynamic control of the local instability trend of the deep foundation pit support structure.

[0038] The above formulas are all dimensionless and take their numerical calculations. The formulas are obtained by collecting a large amount of data for software simulation to obtain a formula closest to the actual situation. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0039] The above embodiments can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product.

[0040] Those of ordinary skill in the art can realize that the modules and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0041] In addition, the functional modules in each embodiment of the present application can be integrated into one processing module, or each module can exist physically alone, or two or more modules can be integrated into one module.

[0042] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0043] Finally, the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. Intelligent monitoring system for deformation and stress of deep foundation pit support structure, characterized in that: It includes a support data acquisition module, a structural stiffness trend analysis module, an abnormal area identification module, and a grading strategy adjustment module, and the modules are connected by signals; The support data acquisition module is used to collect the deformation and stress monitoring data of the deep foundation pit support structure, determine the high-density layout area, and deploy the acquisition of tilt angle data in the high-density layout area; The structural stiffness trend analysis module is used to establish an inversion relationship based on the real-time stress change rate and strain rate of the structure, obtain the current equivalent modulus of the structure, extract the equivalent modulus change sequence to determine the modulus equivalent change rate, and judge the structural stiffness evolution trend; The abnormal area identification module is used to construct a modulus change rate field based on the equivalent modulus change rate, set a partition threshold in combination with the disturbance sensitivity factor, and identify and spatially locate the abnormal area of the structure; The grading strategy adjustment module is used to obtain the structural behavior information generated in the abnormal area and analyze it after spatially locating the abnormal area of the structure, and trigger a grading response strategy according to the results of the structural behavior analysis.

2. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 1, characterized in that: It is used to collect the deformation and stress monitoring data of the deep foundation pit support structure, determine the key measurement area, and deploy the acquisition of tilt angle data in the key measurement area. The specific steps are as follows: According to the theoretical principal stress ratio of the support structure position, the response intensity of disturbance or unloading, and the importance coefficient of the impact of local instability or failure of the structure on the overall structural safety, use the layout density distribution function to determine the key measurement area; In the key measurement area, use fiber Bragg grating strain sensors and laser displacement sensors to collect structural deformation data in real time, use Brillouin fiber optic stress sensors to collect data, and calculate the stress by inverse calculation of the measurement frequency change to obtain stress data. Deploy MEMS inclinometers for real-time monitoring to obtain the tilt angle data of the structural nodes.

3. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 2, characterized in that: It is used to establish an inversion relationship based on the real-time stress change rate and strain rate of the structure, and obtain the current equivalent modulus of the structure. The specific steps include: Perform first-order difference calculation on the strain data and stress data to obtain the structural strain rate and stress change rate; Determine the equivalent modulus according to the local approximate linear instantaneous response relationship between the structural strain rate and stress change rate on the continuous time series.

4. The intelligent monitoring system for the deformation and stress of the deep foundation pit support structure according to claim 3, characterized in that: And extract the equivalent modulus change sequence to determine the modulus equivalent change rate, and judge the structural stiffness evolution trend. The specific steps are as follows: Determine the support structure according to the equivalent modulus change amplitude; If the equivalent modulus change amplitude is in a steady state, the support structure is in the normal elastic response stage; If the equivalent modulus shows a rapid decline, the support structure is in the non-linear, degraded or unstable stage; Obtain the equivalent modulus sequence obtained by the inversion process, and use the first derivative of the equivalent modulus with respect to time as the equivalent modulus change rate; Determine the structural stiffness evolution trend according to the equivalent modulus change rate.

5. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 4, characterized in that: Determine the structural stiffness evolution trend according to the equivalent modulus change rate, including the following steps: If the equivalent modulus change rate is less than 0, it means that the stiffness of the deep foundation pit support structure is in a weakening trend; If the absolute value of the equivalent modulus change rate increases, it means that the stiffness evolution of the deep foundation pit support structure is discontinuous, and structural state mutations or external interference events are likely to occur; If the change rate of the equivalent modulus remains unchanged, it indicates that the structural stiffness maintains a stable trend and is in the safe response stage.

6. The intelligent monitoring system for the deformation and stress of the deep foundation pit support structure according to claim 5, characterized in that: It is used to construct a modulus change rate field based on the change rate of the equivalent modulus, and set the partition threshold in combination with the disturbance sensitivity factor to identify and spatially locate the abnormal area of the structure. The specific steps are as follows: Merge the monitoring positions of the deep foundation pit support structure and the change rate of the equivalent modulus into a measurement point set; Use local structure-related interpolation to perform spatial interpolation on the measurement point set to determine the modulus change rate values of different monitoring points, and construct a modulus change rate spatial field based on the modulus change rate values; Set the regional modulus change rate determination threshold and compare it with the modulus change rate value to determine whether there is an abnormal change in the current state of the support structure.

7. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 6, characterized in that: Set the regional modulus change rate determination threshold and compare it with the modulus change rate value to determine whether there is an abnormal change in the current state of the support structure. The specific steps are as follows: If the modulus change rate value exceeds the modulus change rate determination threshold, it indicates that there is a risk of abnormal structural performance in the detection area, which is marked as an abnormal area; After performing the judgment on all monitoring points, generate a structural stiffness abnormality distribution map, mark the identified abnormal areas, and form a spatial abnormal mask layer or risk heat map.

8. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 7, characterized in that: It is used to obtain and analyze the structural behavior information generated in the abnormal area after spatially locating the structural abnormal area. The specific steps are as follows: Obtain the structural behavior information generated during the process of the abnormal area after spatially locating the abnormal area of the structural modulus change; The structural behavior information includes the structural response distortion index and the structural response hysteresis index; The structural response distortion index represents the deviation degree between the actual stress response of the structure and the design theoretical response; The structural response hysteresis index represents the time delay degree of the stress-strain response of the structure relative to the strain input; Compare and analyze the structural response distortion threshold and the structural response hysteresis threshold with the structural response distortion index and the structural response hysteresis index respectively.

9. The intelligent monitoring system for deformation and stress of deep foundation pit support structure according to claim 8, characterized in that: Trigger a hierarchical response strategy according to the results of the structural behavior analysis. The specific steps are as follows: When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, the support structure does not need to be adjusted and continues to be monitored; When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is less than the structural response hysteresis threshold, the overall structure is still in a fluctuating state, and the change trend frequency of the monitored support structure area is increased; When the structural response distortion index is less than the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, increase the data acquisition frequency and conduct key long-term monitoring; When the structural response distortion index is greater than or equal to the structural response distortion threshold and the structural response hysteresis index is greater than or equal to the structural response hysteresis threshold, it is necessary to immediately trigger an alarm and take measures such as strengthening detection or emergency assessment.

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