Soft soil foundation pit preloading inclined pile support deformation control method and system

Abstract

The application relates to a soft soil foundation pit preloading inclined pile support deformation control method and system, and relates to the inclined pile support field, which comprises the following steps: a support data acquisition step, which is configured to collect monitoring data in a foundation pit excavation process by configuring axial force, displacement and force transmission monitoring elements; a hierarchical preloading collaborative regulation step, which is configured to determine preloading axial force target values of each support unit according to foundation pit design parameters, and gradually apply preloading axial force and maintain pressure stability according to a multi-level gradient loading process; a force transmission analysis and dynamic compensation step, which is configured to analyze force transmission loss according to pressure transmission data collected by the force transmission monitoring elements, calculate support force effectively acting on the support structure, and dynamically adjust axial force of each support unit in combination with real-time displacement data; and a deformation repair result output step, which is configured to start multi-unit hierarchical supplementary load repair to generate a deformation control curve when support displacement exceeds a warning threshold. The application has the reliability of improving the inclined pile support structure to offset displacement caused by soft soil foundation pit deformation.

Description

Technical Field

[0001] This application relates to the field of inclined pile support technology, and in particular to a method and system for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits. Background Technology

[0002] Deep foundation pit support in soft soil areas is a core geotechnical engineering technology for urban underground space development. Inclined pile support, as a green support method that avoids large-scale concrete demolition waste and is easy to construct, is widely used in foundation pit engineering in coastal soft soil areas. Conventional inclined pile support uses steel pipe composite piles as inclined force transmission components, forming a support force system through integral casting of the capping beam. It relies on the soil and piles to jointly resist the active earth pressure of the foundation pit, offering significant advantages such as short construction period and recyclable components. Existing conventional inclined pile supports are mainly non-preloaded integrated structures, with the core components of the inclined piles directly anchored and cast to the capping beam. This makes it impossible to actively apply preloaded axial force to the inclined support independently; it only relies on the earth pressure after excavation to passively stimulate the support resistance, thus belonging to a passive support system.

[0003] In related technologies, to improve the defects of traditional inclined pile deformation control, existing improved technologies propose a simplified manual preloaded inclined pile structure. A simple hydraulic jacking device is added to the top of the inclined pile. Before excavation, a fixed preloaded axial force is applied once and then the cylinder is locked to complete the pressure holding, thereby offsetting part of the later creep deformation of the soil in advance. Ordinary non-preloaded inclined pile support relies only on the passive force of soil load. Under the high compression and high creep characteristics of soft soil, the lateral deformation of the support pile is significant during the foundation pit excavation process, and the control effect of deep soil horizontal displacement and wall top displacement is poor. It cannot meet the control requirements of deformation-sensitive areas such as surrounding roads, pipelines, old buildings and structures, and rail transit. Although the simplified manual preloaded inclined pile can apply an initial preloaded axial force, after the preloaded axial force is applied, it is affected by multiple factors such as soft soil creep, disturbance of adjacent inclined pile loading, and changes in ambient temperature. The support axial force continues to decrease over time. It is difficult to apply the preloaded axial force again in the middle and late stages of foundation pit excavation, the deformation control effect is reduced and cannot be repaired.

[0004] Regarding the aforementioned technologies, traditional non-preloaded inclined pile supports lack active force control methods, making it difficult to manage foundation pit deformation under soft soil creep. Conventional manual preloaded inclined piles lack real-time monitoring, dynamic axial force compensation, and displacement repair functions, and the long-term attenuation of preloaded axial force cannot be offset. For deep foundation pits with stringent surrounding environmental protection requirements, asymmetrical high and low spans, and deep silty soft soil, the deformation control precision is insufficient, and the support safety redundancy is difficult to accurately control. Summary of the Invention

[0005] To improve the reliability and stability of preloaded inclined pile support structures in offsetting displacements caused by deformation in soft soil foundation pits, this application provides a method and system for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits.

[0006] Firstly, this application provides a method for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits: A method for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits, applied to preloaded inclined pile support structures equipped with coordinated servo systems in soft soil foundation pits, includes: The support data acquisition steps involve configuring axial force sensing, displacement sensing, and force transmission monitoring elements in a pre-set multi-set axial force servo inclined pile support system, and collecting axial force monitoring data, support lateral displacement monitoring data, and force transmission path pressure monitoring data of each support unit during the foundation pit excavation process, while simultaneously acquiring foundation pit excavation condition information and spatial arrangement information of each monitoring sensing element. The graded preloading and coordinated control steps are configured with a graded preloading and coordinated pressure stabilization strategy. The target value of the preloaded axial force of each support unit is determined according to the design parameters of the foundation pit. The preloaded axial force is applied step by step according to the multi-level gradient loading process and pressure is maintained to eliminate the gaps in component assembly and the initial creep deformation of the soil. The force transmission analysis and dynamic compensation steps are configured with force transmission efficiency analysis and axial force closed-loop control strategy. Based on the pressure transmission data collected by the force transmission monitoring element, the force transmission loss is analyzed, the effective support force acting on the support structure is calculated, and the axial force of each support unit is dynamically adjusted in combination with real-time displacement data to suppress the development of foundation pit displacement. The deformation repair result output steps are configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, a multi-unit graded loading repair program is started. Based on the axial force, force transmission efficiency and displacement data after repair, a time-series correlated deformation control curve is generated to reflect the deformation control effect.

[0007] By adopting the above technical solution, the support control of soft soil foundation pits is carried out through four coordinated steps: support data acquisition, graded preloading and coordinated control, force transmission analysis and dynamic compensation, and deformation repair result output. Multi-dimensional data of support axial force, lateral displacement, and force transmission path are collected simultaneously. Based on the whole cycle control process of pre-excavation preloading, quantitative calculation of force transmission loss, closed-loop dynamic force adjustment of axial force, and graded repair of excess force, the support control of soft soil foundation pits is carried out. Unlike the traditional inclined pile servo solution that only relies on the theoretical axial force control of hydraulic cylinders, lacks pre-deformation pre-control, and cannot quantify the actual support output, this solution inhibits the displacement of soft soil foundation pits in multiple layers from multiple dimensions, including pre-offsetting creep deformation in the early stage of excavation, real-time dynamic constraint during excavation, and active repair of excess deformation. This multi-layered approach weakens the problem of continuous deformation growth caused by the high creep characteristics of soft soil, thereby improving the reliability of the inclined pile support structure in offsetting the deformation displacement of soft soil foundation pits, reducing the cumulative deformation of foundation pits, and reducing the impact of disturbance on surrounding structures and pipelines caused by the lateral deformation of foundation pits.

[0008] Optionally, the multi-group axial force servo inclined pile support system includes two groups of zonal servo adjustment units: a shallow span main adjustment axial force servo inclined pile support group and a deep span auxiliary servo inclined pile support group. The two groups of zonal servo adjustment units are respectively set in support sections with different high and low spans, and a reinforcing force transmission truss is set at the junction of the high and low spans. The reinforcing force transmission truss is equipped with force transmission monitoring elements. When the force transmission efficiency analysis and axial force closed-loop control strategy are executed, the internal force value transmitted at the high and low span junction is collected in real time through the force transmission monitoring element. The loss change during the cross-zone pressure transmission process is analyzed and converted into the effective support force distribution data of the deep and shallow span support structure.

[0009] By adopting the above technical solution, a two-part servo unit arrangement with shallow and deep spans combined with a boundary reinforcement force transmission truss is used. Force transmission monitoring elements are installed inside the truss to collect the cross-zone internal forces in real time. Compared with the existing support scheme that only sets independent servos in each zone and cannot quantify the force transmission loss at the boundary, this solution can accurately distinguish between the theoretical axial force output by the hydraulic cylinder and the effective support reaction force actually acting on each section of the retaining wall. It eliminates the deviation in cross-zone force transmission control caused by truss node deformation and cap beam deflection, providing real force data support for coordinated force adjustment between high and low span zones, and adapting to the precise zone control requirements under asymmetric excavation conditions.

[0010] Optionally, the graded preloading collaborative voltage stabilization strategy is further configured with a cross-regional support force supplementation and regulation sub-strategy, including: Based on the difference between the total horizontal load requirement of the deep span support and the resistance calculation value of the deep span auxiliary servo inclined pile support group, the target transmission supplementary axial force of the shallow span main adjusting axial force servo inclined pile support group is determined. When deep excavation causes an increase in horizontal earth pressure and the deep span support resistance approaches the preset critical value of lateral constraint, the excess axial force of the shallow span main adjusting support group is transmitted to the deep side through the reinforcement force transmission truss to offset the lateral deformation increment of the deep span support structure. When the adjustment of the axial force of the shallow span support causes fluctuations in the internal force of the junction truss, the deep span auxiliary servo inclined pile support group simultaneously fine-tunes the axial force to maintain the force balance at the junction of the high and low spans.

[0011] By adopting the above technical solution, the deep side support load gap is calculated by using the cross-zone support force supplementary sub-strategy. The transmission gradient of the shallow side surplus axial force is synchronously adjusted according to the change of soil pressure. When the internal force at the junction fluctuates, it is synchronously fine-tuned to maintain the force balance. Compared with the conventional servo system that relies solely on the deep side single zone support to bear all the horizontal load, it can cross-zone share the increase of deep side soil pressure, weaken the deformation trend of deep span retaining wall shifting into the pit, and reduce the investment in later deformation repair.

[0012] Optionally, the graded preloading and coordinated pressure stabilization strategy is further configured with a preloading displacement preset sub-strategy before excavation, including: Before the excavation of the foundation pit is started, the target pre-loaded axial force value of the composite inclined pile is set in advance. The pre-loaded axial force is applied step by step using a multi-level gradient. After each loading is completed, the axial force attenuation range and the close contact state of the force transmission component are observed statically. During the progressive loading process, the axial force setting value is compensated by combining the axial force attenuation coefficient of the adjacent inclined piles loading sequentially, so as to offset the axial force attenuation caused by the loading disturbance of the adjacent piles. During the pressure holding stage, the creep deformation and axial force change rate of the pile body are continuously monitored. After the pressure holding time reaches the set time and the axial force decay tends to stabilize and the creep rate of the pile body drops to the set limit, it is confirmed that the axial preload displacement of the composite inclined pile has been fully formed. Then the foundation pit excavation process is started, so that the pre-generated axial preload displacement can offset the increase in lateral displacement of the support caused during the excavation process.

[0013] By adopting the above technical solution, multi-level gradient preloading is performed before the foundation pit is excavated to compensate for the axial force loss caused by the loading of adjacent piles. Excavation is started after the creep and axial force decay tend to stabilize. The axial preloading displacement is formed in advance to offset the subsequent excavation deformation increment. Compared with the existing inclined pile servo technology that only carries out support control after excavation and has no preloading measures, it can offset the displacement increment caused by soft soil creep in advance, reduce the cumulative amount of support lateral deformation throughout the excavation process, and reduce the frequency of foundation pit deformation exceeding the warning threshold.

[0014] Optionally, the force transmission efficiency analysis and axial force closed-loop control strategy includes: Pre-set the early warning threshold and control threshold for the top displacement of the crown beam, and use the displacement control value that reaches the set proportion as the dynamic compensation start condition; The direction of displacement development is matched with the daily increment to determine the corresponding gradient level for adjusting the support axial force. When the displacement increases towards the pit, the axial force is increased, and vice versa. The upper limit of axial force compensation adjustment is monitored in real time to keep it within the range of the corresponding composite inclined pile ultimate bearing capacity test value of the set safety ratio.

[0015] By adopting the above technical solution, two levels of displacement thresholds are set as compensation trigger conditions. The support axial force is adjusted in stages according to the direction of displacement development, while limiting the safe range of axial force adjustment. Compared with traditional servo support without a graded trigger mechanism and only fixed axial force output, the force can be dynamically matched and adjusted according to the real-time deformation state of the foundation pit, taking into account both deformation constraint requirements and the safety of the support structure itself, and avoiding excessive loading that causes local stress concentration in the pile and cap beam.

[0016] Optionally, a special sub-strategy for asymmetric load control is also configured, including: For asymmetric excavation pits at the junction of high and low spans, axial force servo inclined pile supports are installed at the junction, and the difference in earth pressure on both sides is calculated in advance. Before deep excavation, a pre-applied axial force is applied at the junction based on the asymmetric load difference and automatically stabilized to reduce the harmful displacement on the deep side of the edge.

[0017] By adopting the above technical solution, a special control logic is set up for asymmetric foundation pits with high and low spans. Servo supports are deployed at the junction and preloaded and stabilized in advance based on the load difference. The deformation of the unbalanced system is transformed into controllable displacement at the junction. Compared with conventional support schemes that do not have targeted control and allow harmful displacement to continue to occur on the deep side, this can weaken the unbalanced soil pressure effect caused by the difference in excavation depth on the deep and shallow sides, significantly reduce the total lateral deformation of the deep side retaining structure, and reduce the difficulty of protecting surrounding sensitive facilities.

[0018] Optionally, a regional axial force ratio calibration sub-strategy is also configured, including: The calculation units are divided into three categories according to the plane position of the foundation pit: normal area, external corner area, and long and short inclined pile area. For the external corner area with different support forms, the calculation span is corrected by the corresponding reduction coefficient. For the long and short inclined pile area, the calculation span is allocated according to the ultimate bearing capacity of a single pile, and the axial force design value of the inclined pile support at each position is matched with the actual stress characteristics.

[0019] By adopting the above technical solution, the foundation pit is divided into three types of stress units. The calculation span is modified differently for different corner supports and long and short pile conditions. The actual stress characteristics of each location are matched. Compared with the traditional design method that uses a single span for calculation and ignores the local stress differences, the deviation between the design value of the inclined pile support axial force and the actual on-site force can be reduced, the matching degree of servo axial force control can be improved, and the phenomenon of excessive deformation of local support sections can be reduced.

[0020] Optionally, the multi-support linkage displacement repair optimization strategy includes: After the foundation pit deformation stabilizes, the axial force of the support is gradually increased according to the set gradient. After each load level stabilizes, the deep horizontal displacement of the foundation pit soil and the displacement of the cap beam are collected. Identify the elastic and plastic repair components in the displacement repair amount and evaluate the permanent repair effect; After the repair is completed, the load is gradually reduced to the normal operating axial force value, and the displacement rebound amount after unloading is recorded.

[0021] By adopting the above technical solution, axial force is applied in stages after deformation stabilizes. The elastic and plastic repair components are distinguished by the displacement difference before and after loading and unloading. The permanent repair effect is quantified by the proportion of plasticity and verified by rebound data. Compared with existing repair methods that only roughly observe the reduction in displacement and cannot distinguish between permanent and temporary repair effects, the long-term governance capacity of the control measures can be accurately evaluated. This provides quantitative data basis for subsequent operation and maintenance of foundation pit support and adjustment of excavation procedures, avoiding the risk of secondary deformation caused by short-term rebound.

[0022] Optionally, the axial force servo inclined pile support system has a built-in working condition adaptive parameter library for use in two types of strategies: graded preloading and closed-loop control. The parameter library pre-stores graded loading templates and axial force compensation coefficients corresponding to different strata, foundation pit depths, and inclined pile types; When construction begins, the system automatically matches the corresponding graded loading module and axial force compensation coefficient, and collects measured deformation data during construction in real time to update the parameter library, continuously optimizing the control accuracy of subsequent projects.

[0023] By adopting the above technical solution, configuring a bidirectional iterative adaptive parameter library for working conditions, pre-storing multiple types of working condition control templates, automatically matching parameters during construction and continuously updating and optimizing based on on-site measured data, compared with servo control systems with fixed parameters that cannot adapt to different soft soil and foundation pit working conditions, it can continuously optimize the accuracy of control parameters with engineering measured data, reducing the workload of repeatedly calculating parameters for different projects.

[0024] Secondly, this application provides a deformation control system for preloaded inclined pile supports in soft soil foundation pits, employing the following technical solution: A deformation control system for preloaded inclined pile supports in soft soil foundation pits includes: The data acquisition module is equipped with an axial force sensing unit, a displacement sensing unit, and a hydraulic force transmission monitoring unit embedded in the reinforced force transmission truss. It is used to synchronously collect axial force data, support lateral displacement data, and pressure change data of the force transmission path of the main and auxiliary servo support units. The graded preloading module is equipped with a graded preloading and coordinated pressure stabilization strategy, which is used to apply preloaded axial force to each support unit in a multi-level gradient and maintain pressure stability, eliminate component assembly gaps and initial creep deformation of soil, and complete the pre-setting of axial preload displacement before excavation. The force transmission analysis and closed-loop control module is equipped with force transmission efficiency analysis and axial force closed-loop control strategy. It is used to analyze force transmission loss and calculate effective support force based on the pressure data of the force transmission path, and dynamically adjust the axial force of the main and auxiliary support units in combination with real-time displacement data to suppress the development of foundation pit displacement. The multi-support linkage repair module is configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, it is used to start multi-unit hierarchical reloading repair, generate periodic deformation control curves and output deformation control feedback information.

[0025] By adopting the above technical solution, four corresponding hardware modules are configured for data acquisition, graded preloading, closed-loop force transmission control, and multi-support linkage repair. This allows for the simultaneous acquisition of multi-source data on axial force, displacement, and force transmission pressure from dual servo units, and the full-process automated execution of preloading, dynamic force adjustment, and quantitative repair. Compared with traditional foundation pit servo equipment that only has a single servo loading function, the hardware modules are deeply matched with the soft soil-specific control strategy, resulting in a higher degree of automated management. This eliminates the need for extensive manual monitoring and parameter adjustment, reducing the manpower required for foundation pit support deformation control.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. By constructing a closed-loop process for support data acquisition, support control, dynamic compensation, and deformation repair results, the cycle of soft soil foundation excavation is controlled, and the servo adjustment unit of the inclined pile support is adjusted to compensate the support force. Compared with the traditional servo inclined pile scheme that relies solely on the output axial force of the hydraulic cylinder for direct control and does not distinguish the actual effective support force, it can take into account multiple needs such as pre-loading suppression before excavation, dynamic force adjustment during excavation, and active repair of excessive deformation. It adapts to the creep characteristics of deep soft soil, gradually weakens the continuous development of foundation pit displacement, broadens the adaptability of the support system to complex foundation pit conditions such as high and low spans and external corners, and reduces the impact of foundation pit deformation disturbance on surrounding pipelines and buildings. 2. By using two groups of servo units for shallow and deep spans in conjunction with reinforced force-transmitting trusses at the junction of high and low spans, and equipping the trusses with force-transmitting monitoring elements, the internal forces transmitted across the spans are collected in real time and converted into effective support force distribution data of the shallow and deep span support structures. Compared with existing support schemes that only set up servo units independently in each zone and cannot quantify the force transmission loss at the junction, this method can accurately distinguish between the theoretical axial force output by the hydraulic cylinder and the actual effective support reaction force of each section of the retaining wall, eliminate the deviation in cross-zone force transmission control caused by truss nodes and crown beam deflection, provide real force data support for coordinated force adjustment of high and low span zones, and adapt to the precise control requirements of asymmetric excavation pit zones. 3. By performing multi-level gradient preloading and compensating for axial force loss caused by adjacent pile loading before excavation, and then starting excavation after creep and axial force decay have stabilized, the axial preloading displacement is pre-formed to offset the subsequent excavation deformation increment. Compared with the existing inclined pile servo technology that only carries out support control after excavation and has no preloading measures, this technology can offset the displacement increment caused by soft soil creep in advance, reduce the cumulative amount of lateral deformation of support throughout the excavation process, and reduce the frequency of excavation deformation exceeding the warning threshold. Attached Figure Description

[0027] Figure 1 This is the overall flowchart of the method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits in this application.

[0028] Figure 2 This is a schematic diagram of the vertical structure of the preloaded inclined pile support for the soft soil foundation pit spanning the height of this application.

[0029] Figure 3 This is a flowchart of the horizontal support force supplementation and control sub-strategy in the embodiments of this application.

[0030] Figure 4 This is a flowchart of the pre-excavation displacement pre-setting sub-strategy in the embodiments of this application.

[0031] Figure 5 This is a graph showing the force transmission efficiency versus input axial force in an embodiment of this application.

[0032] Figure 6 This is a flowchart of the force transmission efficiency analysis and axial force closed-loop control strategy in the embodiments of this application.

[0033] Figure 7 This is a flowchart of the regional axial force ratio calibration sub-strategy in the embodiments of this application.

[0034] Figure 8 This is a flowchart of the multi-support linkage displacement repair optimization strategy in the embodiments of this application.

[0035] Explanation of reference numerals in the attached drawings: A1, shallow span main adjustable axial force servo inclined pile support group; A2, deep span auxiliary servo inclined pile support group; B, reinforced force transmission truss. Detailed Implementation

[0036] To make the purpose, technical solution, and advantages of this application clearer, the following description is provided in conjunction with the appendix. Figures 1-8 The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the application.

[0037] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0038] This application discloses a method for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits. It manages the excavation cycle of soft soil foundations and adjusts the servo adjustment unit of the inclined pile supports to compensate for the support force. It can take into account multiple needs such as preloading suppression before excavation, dynamic force adjustment during excavation, and active repair of excessive deformation. It adapts to the creep characteristics of deep soft soil, gradually weakens the continuous development of foundation pit displacement, broadens the adaptability of the support system to complex foundation pit conditions such as high and low spans and external corners, and reduces the impact of foundation pit deformation disturbance on surrounding pipelines and buildings.

[0039] Reference Figure 1 The method for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits includes the following steps: S100: Support data acquisition steps, using a preset multi-set axial force servo inclined pile support system to configure axial force sensing, displacement sensing and force transmission monitoring elements, and collect axial force monitoring data, support lateral displacement monitoring data and force transmission path pressure monitoring data of each support unit during the foundation pit excavation process, and simultaneously obtain foundation pit excavation condition information and spatial arrangement information of each monitoring sensing element. The axial force sensing element is a pressure acquisition module built into each servo cylinder. The axial force monitoring data is the axial load time sequence value of the inclined pile obtained by calibrating and converting the real-time output oil pressure of the cylinder. The displacement sensing elements are divided into two types: one type is pre-embedded in the inclinometer tube of the retaining pile to collect the horizontal displacement of the deep soil, and the other type is deployed on the top surface of the capping beam to collect the surface lateral displacement. The lateral displacement monitoring data of the support is a displacement time sequence record continuously collected throughout the entire excavation cycle.

[0040] The force transmission monitoring element uses an embedded hydraulic force measuring component, assembled inside the reinforced force transmission truss between two sets of servo units. The pressure monitoring data of the force transmission path is the real-time pressure timing parameters transmitted from the main regulating inclined piles to the steel beams. The foundation pit excavation condition information includes engineering foundation parameters such as excavation layer depth, foundation pit zoning, height difference between basement spans, arrangement of external corners and long and short piles, and type of support piles. The spatial layout information of the sensing elements records the installation parameters of various sensors, such as the embedment depth, horizontal spacing, inclination angle of the servo inclined piles, span of the reinforced steel beams, and sensor installation protection conditions.

[0041] In practice, staff enter the project's geological survey data, support construction drawings, and servo support layout plan into the system operation terminal to complete the initial configuration. Before the earthwork excavation operation starts, the system automatically drives three types of sensors—axial force, displacement, and force transmission—to synchronously and continuously collect raw monitoring data. All data are timestamped and stored in the local database, and are also bound to the corresponding excavation construction condition tags. For foundation pits with multiple sections being excavated simultaneously, multiple sets of main and auxiliary servo acquisition channels are independent of each other, and each set of hydraulic control circuits does not interfere with each other, avoiding mutual influence during the pressure adjustment process.

[0042] S200: The graded preloading and coordinated control steps are configured with a graded preloading and coordinated pressure stabilization strategy. The target value of the preloaded axial force of each support unit is determined according to the design parameters of the foundation pit. The preloaded axial force is applied step by step according to the multi-level gradient loading process and pressure is maintained to eliminate the gap between component assembly and the initial creep deformation of the soil. Multi-level gradient loading is divided into three pressure levels: low, medium, and high. After each level of loading is completed, a fixed pressure stabilization observation period is set. The component assembly gap refers to the tiny gaps existing at the splicing positions of inclined piles, cap beams, and reinforcing steel beams. The initial creep deformation of the soil is the slow compressive displacement generated by the continuous preloading of the Ningbo soft soil.

[0043] In practice, the system retrieves the built-in adaptive parameter library of working conditions and matches the target value of pre-applied axial force corresponding to the soil layer and inclined pile specifications of this project; it automatically executes the graded pressurization process, continuously monitors the axial force fluctuation value in each pressurization stage, and enters the next level of loading after the pressure tends to stabilize. It eliminates splicing gaps by compacting step by step, and induces soil creep in advance to reduce the deformation increment during the excavation stage.

[0044] S300: Force transmission analysis and dynamic compensation steps, equipped with force transmission efficiency analysis and axial force closed-loop control strategy. Based on the pressure transmission data collected by the force transmission monitoring element, it analyzes the force transmission loss, calculates the effective support force acting on the support structure, and dynamically adjusts the axial force of each support unit in combination with real-time displacement data to suppress the development of foundation pit displacement. The force transmission loss is the difference between the output shaft of the main hydraulic cylinder and the measured pressure of the steel beam. The effective support force is the actual load acting on the retaining structure after eliminating the loss. The harmful lateral displacement is the excessive deformation of the foundation pit retaining structure that causes it to shift out of the pit and easily damage surrounding pipelines and buildings.

[0045] In practice, the system calculates the force transmission loss and effective support force in real time, reads the deep layer and crown beam displacement monitoring data simultaneously, and automatically increases or decreases the main and auxiliary servo axial forces according to the preset displacement index, thereby constraining the harmful deformation generated in the pit from the source.

[0046] S400: Deformation repair result output steps, configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, a multi-unit graded loading repair program is started. Based on the repaired axial force, force transmission efficiency and displacement data, a time-series correlated deformation control curve is generated to reflect the deformation control effect.

[0047] Multi-unit graded loading refers to the synchronous control of the main and auxiliary servo inclined piles to gradedly increase the axial force and reverse the excessive lateral displacement that has been generated; the deformation control curve integrates three types of time-series change data: support axial force, deep displacement, and cap beam displacement throughout the excavation process.

[0048] In practice, after the monitored displacement exceeds the warning limit, the system synchronously controls two sets of servo supports to gradually increase pressure for repair. After the repair is completed, the full-cycle monitoring and control data are summarized, and a traceable foundation pit deformation control curve is automatically generated and stored for archiving.

[0049] Reference Figure 2 The multi-set axial force servo inclined pile support system includes two zonal servo adjustment units: shallow-span main adjustable axial force servo inclined pile support group A1 and deep-span auxiliary servo inclined pile support group A2. Specifically, the shallow-span main adjustable axial force servo inclined pile support group A1 is spaced along the first-floor basement support capping beam, bearing the main lateral earth pressure in the shallow excavation section; the deep-span auxiliary servo inclined pile support group A2 is spaced along the second-floor basement support capping beam, bearing the lateral earth pressure in the deep excavation section.

[0050] Two sets of zonal servo adjustment units are respectively set in support sections with different spans (high and low). A reinforcing force transmission truss B is set at the junction of the high and low spans. The two ends of the reinforcing force transmission truss B are rigidly connected to the shallow span cap beam and the deep span cap beam, respectively, forming a continuous cross-zone force transmission path. Force transmission monitoring elements are installed inside the reinforcing force transmission truss B. In this embodiment, an embedded hydraulic force measuring unit is used, which is deployed at the connection nodes between the truss and the cap beams on both sides to collect internal force transmission data at the junction throughout the entire process.

[0051] When the force transmission efficiency analysis and axial force closed-loop control strategy are executed, the measured value of the transmitted internal force of the reinforced force transmission truss B at the junction of the high and low spans is collected in real time through the force transmission monitoring element. The system simultaneously reads the theoretical output axial force of each servo inclined pile of the shallow span main adjustment axial force servo inclined pile support group A1 and the deep span auxiliary servo inclined pile support group A2.

[0052] The difference between the measured internal force and the theoretical axial force at the interface is determined as the cross-span force transmission loss. The sources of this loss include elastic deformation of truss nodes, deflection deformation of the cap beam, gaps in the contact surfaces of components, and axial force attenuation caused by soil creep. After deducting the force transmission loss, the effective support force distribution data for the shallow and deep span support structures are calculated separately, serving as the calculation benchmark for subsequent dynamic adjustment of axial force.

[0053] Based on this structure, the system can further implement cross-regional support force supplementation and control sub-strategies and asymmetric load special control sub-strategies: when deep excavation causes an increase in soil pressure and the resistance of the deep-span auxiliary servo inclined pile support group A2 is insufficient to restrain lateral displacement, the reinforcement force transmission truss B transmits the surplus axial force of the shallow-span main adjusting axial force servo inclined pile support group A1 to the deep side, assisting the deep-span support group in jointly bearing the horizontal load and offsetting the lateral deformation increment of the deep-span support; when there is a significant asymmetric load difference, by pre-applying axial force at the junction and automatically stabilizing the pressure, the systematic deformation and unbalanced system deformation of the support system are transformed into controllable displacement at the junction.

[0054] Reference Figure 3 The graded preloading collaborative voltage stabilization strategy is also equipped with a horizontal support force supplementary regulation sub-strategy, which adopts the following steps and methods: S210: Determine the target supplementary axial force of the auxiliary horizontal servo inclined pile support based on the difference between the calculated horizontal component force of the main adjusting axial force servo inclined pile support and the total horizontal load requirement of the support. The horizontal component of the main adjustable axial force servo inclined pile support is the horizontal load value calculated based on the effective support force and the inclination angle of the inclined piles. The total horizontal load requirement of the support is the total horizontal resistance required for the entire retaining section calculated based on the excavation depth of the foundation pit and the water and soil pressure of the soft soil. The difference between the two represents the load gap that the existing inclined support cannot cover. The target supplementary axial force is the preset load range of the auxiliary support required to fill the gap.

[0055] In practice, the system relies on the effective support force obtained by force transmission monitoring elements, and combines the inclination angle of the inclined pile to complete the real-time calculation of the horizontal component force. Simultaneously, it retrieves the soil and water pressure parameters of the excavation layer to calculate the total horizontal load, automatically solves the load difference, and generates the supplementary axial force for auxiliary support matching, providing a control benchmark for subsequent graded loading.

[0056] S220: When the excavation of the foundation pit causes an increase in horizontal earth pressure and the horizontal component of the main support approaches the preset critical value of lateral constraint, the auxiliary horizontal servo inclined pile support is gradually loaded according to the set gradient, and works with the main adjustment unit to jointly bear the horizontal load and offset the lateral deformation increment of the support structure. The excavation of the foundation pit will gradually release the lateral water and soil pressure of the soft soil, causing the retaining wall to deform laterally into the pit. The horizontal component of the inclined main support alone is not enough to completely offset this deformation trend. The step-by-step loading refers to dividing the load increment into multiple levels to gradually increase the axial force of the auxiliary support, so as to avoid sudden stress changes in a single loading.

[0057] In practice, the displacement sensor continuously monitors the lateral displacement of the retaining wall. When the displacement continues to expand outward and the horizontal component of the main support cannot match the increased earth pressure, the system automatically increases the axial force of the auxiliary servo cylinder in different gears to work with the main support to share the lateral earth pressure and reduce the deformation increment of the retaining wall as it continues to move outward.

[0058] S230: When the adjustment of the main support axial force causes fluctuations in the horizontal component force of the force transmission structure, the auxiliary horizontal servo inclined pile support synchronously fine-tunes the axial force to maintain the horizontal force balance of the support structure.

[0059] The fluctuation of the horizontal component force in the force transmission structure refers to the instantaneous increase or decrease of the horizontal load transmitted by the reinforcing force transmission steel beam during the pressurization and unloading operations of the main support. The balanced force means that the difference in the horizontal load borne by the left and right sides and the long and short sections of the foundation pit is controlled within a reasonable range to prevent concentrated deformation on one side.

[0060] In practice, the system captures sudden pressure signals on the steel beams through force transmission monitoring elements, and simultaneously adjusts the axial force of the auxiliary supports slightly upward or downward to offset the load fluctuations caused by the main supports, so as to keep the overall enclosure horizontal force stable and avoid large displacements on one side.

[0061] Reference Figure 4 The graded preloading and coordinated pressure stabilization strategy is also configured with a preloading displacement pre-positioning sub-strategy before excavation, which adopts the following steps and methods: S240: Before starting the foundation pit excavation process, the target pre-loaded axial force value of the composite inclined pile is set in advance. The pre-loaded axial force is applied step by step using multi-level gradient gears. After each loading is completed, the axial force attenuation range and the close contact state of the force transmission components are observed statically. The target preload axial force is the design preload load adapted to the soft soil layer, inclined pile cross-section size, and inclination angle of this project. Multi-level gradient loads decompose the total preload axial force into multiple load stages, applied step-by-step to avoid instantaneous stress concentration in the support components caused by a single full-load pressurization. The axial force attenuation range represents the natural loss of preload axial force during the pressure stabilization stage. The tight fit status of the force transmission components is used to determine whether the assembly gaps between the inclined piles, capping beams, and reinforced force transmission trusses are completely compacted and fitted. In practice, the system calls the adaptive parameter library to match the engineering foundation parameters to determine the target preload axial force and automatically completes the step-by-step pressurization operation according to the multi-level gradient. After each load stage is completed, the system maintains a stable pressure state and synchronously reads the real-time pressure data from the force transmission monitoring elements. If the pressure fluctuation exceeds the allowable range, the static observation time is extended until the component splicing gaps are completely compacted.

[0062] Compared to the traditional inclined pile servo support scheme that only carries out support force adjustment after excavation and has no pre-stage preloading process, this step eliminates assembly gaps in advance through progressive stage preloading, avoiding sudden lateral deformation caused by gap closure during the excavation stage, and can reduce the generation of foundation pit displacement increment from the source.

[0063] S250: During the progressive loading process, the axial force setting value is compensated by combining the axial force attenuation coefficient of the adjacent inclined piles loading sequentially, so as to offset the axial force loss caused by the loading disturbance of the adjacent piles. The axial force attenuation coefficient of adjacent inclined piles is a dimensionless correction parameter obtained from statistical analysis of multiple sets of field tests on soft soil foundation pits. The capping beam has continuous force transmission characteristics. The pressure application of adjacent inclined piles will transfer the load through the capping beam, causing the preloaded axial force of the inclined piles that have been preloaded to be lost. The axial force loss is the value of the decrease in preloaded axial force caused by the construction disturbance of adjacent piles.

[0064] In practice, the system retrieves the axial force attenuation coefficient measured from the existing inclined piles in the same section, and superimposes a compensating load on top of the pre-applied axial force at this level to compensate for the load loss caused by disturbance from adjacent piles. Compared with conventional preloading processes that do not have a pre-applied axial force compensation mechanism for adjacent piles, this step can reduce the effective axial force loss after preloading, ensure that the pre-set reverse deformation before excavation meets the design standard, and improve the reliability of offsetting displacement in soft soil foundation pits.

[0065] The standard adjacent pile loading attenuation coefficient ranges from 0.87 to 0.9, and the pre-applied axial force compensation correction calculation model is as follows: ; In the formula, To compensate for the actual applied preload axial force, For uncompensated reference preload axial force, This is the attenuation coefficient of the axial force of adjacent inclined piles.

[0066] S260: During the pressure holding stage, continuously monitor the creep deformation of the pile body and the rate of change of axial force. After the pressure holding time reaches the set time and the axial force decay tends to be stable and the creep rate of the pile body drops to the set limit, confirm that the axial preload displacement of the composite inclined pile has been fully formed, and then start the foundation pit excavation process to offset the increase in lateral displacement of the support caused during the excavation process with the pre-generated axial preload displacement.

[0067] The creep deformation of the pile body refers to the slow compression deformation of the soil under the long-term constant preload axial force; the axial preload displacement is the reverse reserve deformation formed by the inclined pile squeezing the soil during the preload stage; the lateral displacement increment is the deformation value caused by the retaining structure shifting out of the pit after the earthwork excavation releases the lateral water and soil pressure.

[0068] In practice, during the pressure holding period, the system simultaneously collects the timing data of the axial force of the support and the monitoring data of the deep displacement of the retaining wall. Once both the axial force decay rate and the soil creep rate reach the stability judgment criteria, the system outputs an excavation permit command. The reverse deformation of the axial preloading formed before excavation counteracts the tendency of the retaining wall to shift into the pit due to the release of earth pressure during subsequent excavation. Existing conventional servo-driven inclined pile support can only passively adjust the axial force after deformation occurs during excavation, and cannot release the creep deformation of soft soil in advance. This step, by consuming the soil creep potential in advance through long-term pressure stabilization before excavation, can significantly reduce the total cumulative deformation during the entire excavation process and inhibit the continuous development of pit displacement.

[0069] Reference Figure 5 As the input axial force of the support unit gradually increases, continuous pressure loss occurs in the reinforced force transmission truss, component connection nodes, and internal force transmission paths, causing the force transmission efficiency η to decrease with increasing input axial force. Sampling data shows that as the input axial force increases from 200kN to 700kN, the force transmission efficiency decreases from 94.0% to 87.4%. The greater the axial force, the more significant the difference between the theoretical output value of the hydraulic cylinder and the actual effective support force of the enclosure.

[0070] By utilizing force transmission monitoring elements installed within the reinforced force transmission truss to collect real-time measured pressure, and by calculating the effective support force based on the loss characteristics corresponding to the force transmission efficiency curve, the control deviation caused by directly using hydraulic cylinder output axial force adjustment is avoided, achieving precise closed-loop adjustment of axial force. This force transmission efficiency variation law is applicable not only to the same support edge arrangement mode but also to the cross-regional force transmission loss variation characteristics of the reinforced force transmission truss B under the high-low span foundation pit conditions of this embodiment.

[0071] Reference Figure 6 The force transmission efficiency analysis and axial force closed-loop control strategy adopts the following steps and methods: S300: Pre-set the early warning threshold and control threshold for the top displacement of the crown beam, and use the displacement control value that reaches the set proportion as the dynamic compensation start condition; The warning threshold is the initial warning deviation value of the foundation pit deformation development, and the control threshold is the maximum allowable lateral deviation of the retaining structure determined based on the environmental protection level of the surrounding pipelines and buildings. The set ratio is the early intervention trigger node, without waiting for the deformation to develop to the control limit before remediation.

[0072] In practice, staff input two levels of displacement limit parameters based on the protection levels of the surrounding objects. The system accumulates the horizontal displacement value of the top surface of the capping beam in real time. When the accumulated displacement reaches a preset proportion of the control threshold, the dynamic axial force compensation and control process is automatically initiated. Compared with traditional servo control systems that only carry out repair and treatment after deformation exceeds the standard, this step achieves early intervention in deformation, avoiding the construction difficulties caused by large-scale repairs after the foundation pit displacement continues to expand, and reducing the impact of foundation pit deformation disturbance on surrounding protective facilities.

[0073] S301: Match the displacement development direction with the daily increment to determine the corresponding gradient gear, adjust the support axial force and make adjustments. When the displacement increases into the pit, increase the axial force, and vice versa. The increase in displacement into the pit indicates that the retaining structure is continuously undergoing inward displacement deformation; the daily displacement increment is used to assess the rate of deformation development; multiple gradient levels enable refined and graded adjustment of loads, avoiding excessive single pressure adjustment from impacting the support system.

[0074] In practice, the system statistically analyzes the daily changes in retaining displacement and the direction of displacement, matches the corresponding pressurization and depressurization gradients, and adjusts the output load of the main and auxiliary horizontal servo cylinders in stages. Traditional servo inclined piles mostly use a fixed axial force output mode, which cannot adaptively adjust the load according to the deformation trend. This step relies on real-time deformation data to finely match and control the force, resulting in a more stable restraint effect on the continuous lateral displacement caused by long-term creep of soft soil.

[0075] S302: Real-time monitoring of the upper limit of axial force compensation adjustment, keeping it within the range of the corresponding composite inclined pile ultimate bearing capacity test value of the set safety ratio.

[0076] The upper limit of axial force compensation is a safe load range defined based on the ultimate bearing capacity of the composite inclined pile. It is used to prevent the axial force from exceeding the bearing capacity of the component during the adjustment process, which could cause structural damage such as local stress concentration cracking in the support pile and the cap beam.

[0077] In practice, before each axial force adjustment operation, the system automatically compares the target adjustment load with the upper limit of the bearing capacity. If the target load is close to the safety limit, the pressure gradient is reduced to ensure the structural safety of the support structure throughout the process. Compared with conventional servo control schemes that do not set an upper limit for axial force, this step simultaneously considers displacement constraint requirements and the safety reserve of the support structure, avoids the risk of structural damage caused by excessive pressure, and improves the long-term operational stability of the entire support system.

[0078] It also includes a special sub-strategy for asymmetric load control, employing the following steps and methods: S303: For asymmetric excavation pits at the junction of high and low spans, axial force servo inclined pile supports are installed at the junction location, and the difference in earth pressure on both sides is calculated in advance. The high-low span foundation pit is a foundation pit construction condition in which there is a height difference between the deep and shallow excavation surfaces of the basement. There is a significant difference in the earth pressure load on the deep and shallow sides. This load difference is the core cause of the harmful deformation of the edge retaining structure by large outward displacement. The difference in earth pressure on both sides is the difference between the total horizontal load on the deep side and the total horizontal load on the shallow side. It is the core calculation basis for the pre-applied axial force design of the junction servo support.

[0079] In practice, the system calculates the unit length support reaction force on the deep and shallow sides based on the excavation depth, physical properties of each soil layer, and ground surcharge. Then, it combines the support calculation span to obtain the total horizontal load on both sides and calculates the difference in unbalanced force.

[0080] The formula for the standard value of horizontal earth pressure per unit length on one side is: ; ; ; ; In the formula, , , respectively, are the standard values ​​of active and passive earth pressure strength of the i-th soil layer. , These are the standard values ​​of vertical stress in the i-th soil layer on the active and passive sides, respectively. , These are the active earth pressure coefficient and passive earth pressure coefficient of the i-th soil layer, respectively. Let be the standard value of the effective cohesion of the i-th soil layer. Let be the standard value of the effective internal friction angle of the i-th soil layer.

[0081] Compared to the conventional servo control method that uses uniform preloading without distinguishing between high and low span loads, this step first quantifies the difference in unbalanced loads to provide quantitative parameters for targeted preloading balance, thus avoiding the occurrence of excessive deep displacement caused by the continuous action of the deep and shallow soil pressure difference.

[0082] S304: Before deep excavation, apply pre-loaded axial force based on the asymmetric load difference and automatically stabilize the pressure to convert the systematic deformation and unbalanced system deformation of the support system into controllable displacement at the interface, thereby reducing the amount of harmful displacement at the deep edge.

[0083] Systemic deformation of the support system is uniform and minute deformation caused by the support itself being compressed and temperature-induced; unbalanced system deformation is caused by the difference in earth pressure between deep and shallow areas, resulting in large-scale displacement deformation on one side of the retaining wall; controllable displacement refers to transferring the large-scale harmful deformation concentrated on the deep side to the servo support control section at the boundary, allowing only controllable displacement at the boundary location.

[0084] In practice, the system calculates the matching preload based on the load difference, and the calculation formula is as follows: ; in, To obtain the pre-applied axial force for the conversion, The inclined piles at the junction are set with an inclination angle, and after being loaded in stages to the target preload, they are automatically stabilized for a long period of time. The preload offsets the load difference between the deep and shallow pits, and the unbalanced deformation is constrained to a controllable area at the junction, thereby reducing the harmful displacement of the deep side support structure. The difference in total horizontal load between the deep and shallow sides of the high and low span foundation pit is calculated by combining the unit length support reaction force on the deep and shallow sides with the corresponding support calculation span. The formula for determining the transformation of a variable is: ; in, This represents the reduction in harmful displacement on one side. This represents the maximum horizontal displacement at the deep side edge under unbounded preloading conditions. The maximum horizontal displacement of the deep side adjacent edge after adjustment by this strategy is quantified by this formula to control deformation.

[0085] Existing conventional inclined pile servo schemes do not have a specific preloading mechanism for high and low spans. The load difference between deep and shallow pits will continue to cause large deformation of the perimeter retaining wall. This step uses the load difference to match a specific preloaded axial force, thereby directionally balancing the asymmetric soil and water load and achieving the purpose of reducing the harmful displacement of the deep perimeter.

[0086] Reference Figure 7 It also features a regional axial force ratio calibration sub-strategy, employing the following steps: S305: The calculation units are divided into three categories according to the plane position of the foundation pit: normal area, external corner area, and long and short inclined pile area. The normal area is a straight retaining section of the foundation pit with uniform soil pressure distribution; the retaining section at the external corner is subjected to superimposed soil pressure from both directions, resulting in complex stress; the long and short inclined areas are restricted by site obstacles, and the ultimate bearing capacity of single piles is inconsistent. The stress benchmarks of the three types of areas are very different, and uniformly calculating the span will cause the axial force design to deviate from the actual stress on site.

[0087] In practice, the system reads the foundation pit support plan drawings, automatically divides the area according to the retaining line type, corner nodes, and inclined pile length parameters, and independently performs axial force calibration calculations for each unit to achieve refined control of the area. The zoning is based on the following criteria: straight and continuous sections without corners are classified as normal units; internal and external corners of the foundation pit are classified as external corner units; and sections with obstacles or inconsistent pile lengths are classified as long and short inclined pile units.

[0088] S306: For the external corner area with different support forms, the calculation span is corrected by the corresponding reduction coefficient. For the long and short inclined pile area, the calculation span is allocated according to the ultimate bearing capacity of a single pile, and the axial force design value of the inclined pile support at each position is matched with the actual stress characteristics.

[0089] The reduction factor is used to correct the stiffness difference caused by the superposition of two-way earth pressure at the external corner. The calculated span is the horizontal width of the retaining load shared by a single inclined pile. The load span of the long and short pile sections is calculated back based on the ultimate bearing capacity to achieve the matching of load and pile bearing capacity.

[0090] In practice, the system first performs a calculation to correct the span of the external corner: the formula for calculating the span after the external corner correction is as follows: In the formula , The horizontal spacing between adjacent inclined piles. b is the calculated result of the span correction for the external corner; b is the vertical center distance of the external corner from the foundation pit. This is a preset reduction factor; The formula for calculating the distribution of long and short inclined piles is as follows: ; The formula for calculating the remaining span of a long pile is: ; Based on the revised zoning calculation span, the following formula for axial load of inclined piles is applied: The standard preload axial force for each section is calculated. in, Calculate the span for the load distributed to the short inclined pile; This represents the ultimate bearing capacity of a single inclined pile. To provide a comprehensive safety factor for the support structure; This represents the standard value of the horizontal soil and water pressure at this calculation unit of the foundation pit; The angle of inclination for the inclined piles; The total span is calculated for this support section; Calculate the span for the load distribution on the long inclined pile; Calculate the span for the corrected partition; An axial force is pre-applied for the axial design of the inclined pile.

[0091] Compared with the traditional method of designing a uniform span for the entire foundation pit, this step reduces the deviation between the designed axial force and the measured axial force on site by modifying the span differently, improves the matching degree of dynamic adjustment of servo axial force, and reduces the probability of deformation exceeding the standard in local sections.

[0092] Reference Figure 8The multi-support linkage displacement repair optimization strategy adopts the following methods and steps: S401: After the foundation pit deformation stabilizes, the axial force of the support is gradually increased according to the set gradient. After each load level stabilizes, the deep horizontal displacement of the soil and the displacement of the cap beam are collected. Foundation pit deformation stability refers to the period within which the rate of increase in retaining displacement drops below a predetermined threshold, and the lateral earth pressure and support resistance tend to reach dynamic equilibrium. At this point, repair work can eliminate the interference of continuously increasing earth pressure, resulting in more accurate calculations of the repair volume. Setting a gradient loading stepwise involves dividing the total repair axial force into multiple load increments and applying them in stages, avoiding stress abrupt damage to the support components caused by a single full-load loading.

[0093] In practice, the system first continuously collects displacement monitoring data over several days. When the daily increase in deep horizontal displacement is less than the stability limit, the deformation is determined to have entered a stable phase. Subsequently, the axial force output of the main and auxiliary horizontal servo inclined pile supports is synchronously increased according to the preset axial force gradient. After each loading stage is completed, the system maintains a stable pressure state. After the fluctuations in axial force and displacement data converge, the deep inclinometer displacement and the horizontal displacement data of the top surface of the cap beam are synchronously collected at the full depth in the horizontal direction as the basic sample for quantitative analysis of the repair effect.

[0094] Compared to the traditional approach of directly applying pressure during the deformation development period, this step involves tiered loading after the deformation has stabilized. This method ensures that the repair volume is not affected by the continuous increase in soil pressure, resulting in higher calculation accuracy. Furthermore, the tiered loading mode avoids the impact of sudden load increases on the support structure, making the operation safer.

[0095] The formula for determining deformation stability is as follows: ,and In the formula For displacement rate, This represents the displacement increment within the statistical period. To calculate the duration, For stable rate limits, 0.1–0.2 mm / d can be used in soft soil areas.

[0096] S402: Identify the elastic and plastic repair components in the displacement repair amount and evaluate the permanent repair effect; The elastic repair component is a temporary displacement correction that rebounds synchronously with the decrease of axial force after unloading and cannot be retained for a long time; the plastic repair component is a displacement correction that is permanently retained after unloading and represents the long-term repair and treatment effect. Distinguishing between the two types of repair components can accurately assess the long-term effectiveness of the repair and avoid overestimating the overall treatment effect based solely on the peak pressure displacement retreat.

[0097] In practice, the system records three sets of benchmark data: the initial displacement before repair, the displacement corresponding to the peak loading, and the displacement after unloading to normal operating axial force. The difference between the peak loading displacement and the initial displacement is the total repair amount, and the difference between the displacement after unloading and the initial displacement is the plastic repair component. The total repair amount minus the plastic component is the elastic repair component. At the same time, the repair area of ​​the deep displacement curve can be calculated by integration to quantify the degree of repair of the overall soil deformation.

[0098] Existing conventional repair solutions only focus on the maximum displacement retreat during peak pressurization, ignoring the unloading rebound effect, which easily overestimates the long-term repair effect. This step separates the repair into two types of components, which can accurately assess the effectiveness of permanent treatment and provide a reliable basis for deformation control in the subsequent operation and maintenance phase of the foundation pit.

[0099] S403: After the repair is completed, gradually unload to the normal operating axial force value and record the displacement rebound after unloading.

[0100] Gradual unloading refers to reducing the axial force of the support step by step according to the gradient corresponding to the loading, so as to avoid the rapid rebound of the support displacement caused by the sudden drop in load; the amount of displacement rebound corresponds to the elastic repair component, which can be used to verify the accuracy of the calculation of plastic repair amount, and at the same time monitor the displacement stability throughout the unloading process.

[0101] In practice, after the repair effect is deemed satisfactory, the system synchronously and progressively reduces the axial force of the main and auxiliary servo supports according to the corresponding loading gradient. After each unloading and stabilization period is fixed, displacement data is collected, and the entire displacement rebound process is recorded. After unloading to the daily operating axial force, the displacement change is continuously monitored for several cycles. Once it is confirmed that there is no continuous rebound trend, the repair process ends, and the complete repair data is archived and stored.

[0102] Compared to the conventional method of direct unloading in one go, this step of staged unloading can control the rebound rate, avoid sudden changes in the stress on the support structure, and record the rebound data throughout the process to ensure a smooth transition of the stress on the support system after repair.

[0103] In addition, the axial force servo inclined pile support system has a built-in working condition adaptive parameter library for two types of strategies: graded preloading and closed-loop control. The parameter library pre-stores graded loading templates and axial force compensation coefficients corresponding to different geological strata, foundation pit depths, and inclined pile specifications; When construction begins, the system automatically matches the corresponding graded loading module and axial force compensation coefficient, and collects measured deformation data during construction in real time to update the parameter library, continuously optimizing the control accuracy of subsequent projects.

[0104] The adaptive parameter library is a database that integrates various engineering measured data, calculated parameters, and control templates. It is used to quickly match the optimal control parameters for foundation pits with different geological and excavation conditions, reduce the workload of repeated trial calculations, and improve the control accuracy and implementation efficiency. The graded loading template includes control parameters such as the loading ratio of each level, the stabilization time, and the stability judgment criteria. The axial force compensation coefficient covers various correction parameters such as the adjacent pile attenuation coefficient, the external corner reduction coefficient, the creep compensation coefficient, and the asymmetric load correction coefficient.

[0105] In practice, before the project starts, staff enter basic information such as stratum parameters, excavation depth, inclined pile type, and support type. The system automatically searches for engineering cases with the highest similarity to the working conditions, retrieves the corresponding graded loading template and axial force compensation coefficient, and uses them as the initial control parameters for this project. Throughout the entire foundation pit construction process, axial force and displacement measurement data are continuously collected, the actual compensation coefficient on site is calculated, and the parameters for the corresponding working conditions in the parameter library are updated iteratively with weighting. Subsequent similar foundation pit projects can directly call the optimized parameters, and the regional adaptability of the entire method is gradually improved as engineering cases are accumulated.

[0106] Compared to traditional servo systems that use fixed parameters, this parameter library dynamically iterates based on measured data, and the parameter adaptability continuously improves with the accumulation of engineering projects. It can better adapt to complex working conditions in soft soil areas and reduce the workload of manual parameter debugging.

[0107] The working condition similarity matching uses the weighted distance method: ; In the formula Let i be the feature parameter of the working condition to be matched. For the parameters corresponding to the samples in the library, Assign weights to each parameter and select the sample with the smallest distance D as the matching condition.

[0108] The formula for dynamically updating parameters is: ; In the formula, This is the compensation coefficient obtained from actual measurements in this project. These are the original coefficients in the parameter library. To update the weights and ensure smooth convergence of parameter iteration.

[0109] Based on the same inventive concept, embodiments of the present invention provide a deformation control system for preloaded inclined pile supports in soft soil foundation pits, comprising: The data acquisition module is equipped with an axial force sensing unit, a displacement sensing unit, and a hydraulic force transmission monitoring unit embedded in the reinforced force transmission truss. It is used to synchronously collect axial force data, support lateral displacement data, and pressure change data of the force transmission path of the main and auxiliary servo support units. The graded preloading module is equipped with a graded preloading and coordinated pressure stabilization strategy, which is used to apply preloaded axial force to each support unit in a multi-level gradient and maintain pressure stability, eliminate component assembly gaps and initial creep deformation of soil, and complete the pre-setting of axial preload displacement before excavation. The force transmission analysis and closed-loop control module is equipped with force transmission efficiency analysis and axial force closed-loop control strategy. It is used to analyze force transmission loss and calculate effective support force based on the pressure data of the force transmission path, and dynamically adjust the axial force of the main and auxiliary support units in combination with real-time displacement data to suppress the development of foundation pit displacement. The multi-support linkage repair module is configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, it is used to start multi-unit hierarchical reloading repair, generate periodic deformation control curves and output deformation control feedback information.

[0110] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0111] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A method for controlling the deformation of preloaded inclined pile supports in soft soil foundation pits, applied to a preloaded inclined pile support structure equipped with cooperative servo in soft soil foundation pits, characterized in that... include: The support data acquisition steps involve configuring axial force sensing, displacement sensing, and force transmission monitoring elements in a pre-set multi-set axial force servo inclined pile support system, and collecting axial force monitoring data, support lateral displacement monitoring data, and force transmission path pressure monitoring data of each support unit during the foundation pit excavation process, while simultaneously acquiring foundation pit excavation condition information and spatial arrangement information of each monitoring sensing element. The graded preloading and coordinated control steps are configured with a graded preloading and coordinated pressure stabilization strategy. The target value of the preloaded axial force for each support unit is determined according to the design parameters of the foundation pit, and the preloaded axial force is applied step by step according to the multi-level gradient loading process and the pressure is kept stable. The force transmission analysis and dynamic compensation steps are configured with force transmission efficiency analysis and axial force closed-loop control strategy. Based on the pressure transmission data collected by the force transmission monitoring element, the force transmission loss is analyzed, the effective support force acting on the support structure is calculated, and the axial force of each support unit is dynamically adjusted in combination with real-time displacement data. The deformation repair result output steps are configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, a multi-unit graded loading repair program is started. Based on the axial force, force transmission efficiency and displacement data after repair, a time-series correlated deformation control curve is generated to reflect the deformation control effect.

2. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 1, characterized in that, The multi-group axial force servo inclined pile support system includes two groups of zonal servo adjustment units: a shallow span main adjustment axial force servo inclined pile support group and a deep span auxiliary servo inclined pile support group. The two groups of zonal servo adjustment units are respectively set in support sections with different high and low spans, and a reinforcing force transmission truss is set at the junction of the high and low spans. The reinforcing force transmission truss is equipped with force transmission monitoring elements. When the force transmission efficiency analysis and axial force closed-loop control strategy are executed, the internal force value transmitted at the high and low span junction is collected in real time through the force transmission monitoring element. The loss change during the cross-zone pressure transmission process is analyzed and converted into the effective support force distribution data of the deep and shallow span support structure.

3. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 2, characterized in that, The graded preloading collaborative voltage stabilization strategy is also configured with a cross-regional support supplementary regulation sub-strategy, including: Based on the difference between the total horizontal load requirement of the deep span support and the resistance calculation value of the deep span auxiliary servo inclined pile support group, the target transmission supplementary axial force of the shallow span main adjusting axial force servo inclined pile support group is determined. When deep excavation causes an increase in horizontal earth pressure and the deep span support resistance approaches the preset critical value of lateral constraint, the excess axial force of the shallow span main adjusting support group is transmitted to the deep side through the reinforcement force transmission truss to offset the lateral deformation increment of the deep span support structure. When the adjustment of the axial force of the shallow span support causes fluctuations in the internal force of the junction truss, the deep span auxiliary servo inclined pile support group simultaneously fine-tunes the axial force to maintain the force balance at the junction of the high and low spans.

4. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 1, characterized in that, The graded preloading and coordinated pressure stabilization strategy is also configured with a preloading displacement preset sub-strategy before excavation, including: Before the excavation of the foundation pit is started, the target pre-loaded axial force value of the composite inclined pile is set in advance. The pre-loaded axial force is applied step by step using a multi-level gradient. After each loading is completed, the axial force attenuation range and the close contact state of the force transmission component are observed statically. During the progressive loading process, the axial force setting value is compensated by combining the axial force attenuation coefficient of the adjacent inclined piles loading sequentially, so as to offset the axial force loss caused by the loading disturbance of the adjacent piles. During the pressure holding stage, the creep deformation of the pile body and the rate of change of axial force are continuously monitored. After the pressure holding time reaches the set time and the axial force decay tends to be stable and the creep rate of the pile body drops to the set limit, it is confirmed that the axial preload displacement of the composite inclined pile has been fully formed before the foundation pit excavation process is started.

5. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 1, characterized in that, The force transmission efficiency analysis and axial force closed-loop control strategy includes: Pre-set the early warning threshold and control threshold for the top displacement of the crown beam, and use the displacement control value that reaches the set proportion as the dynamic compensation start condition; The direction of displacement development is matched with the daily increment to determine the corresponding gradient level for adjusting the support axial force. When the displacement increases towards the pit, the axial force is increased, and vice versa. The upper limit of axial force compensation adjustment is monitored in real time to keep it within the range of the corresponding composite inclined pile ultimate bearing capacity test value of the set safety ratio.

6. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 5, characterized in that, It also includes a special sub-strategy for asymmetric load control, including: For asymmetric excavation pits at the junction of high and low spans, axial force servo inclined pile supports are installed at the junction location, and the difference in earth pressure on both sides is calculated in advance. Before deep excavation, a pre-applied axial force is applied based on the asymmetric load difference and automatically stabilized to reduce harmful displacement on the deep side near the edge.

7. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 5, characterized in that, It also features a regional axial force ratio calibration sub-strategy, including: The calculation units are divided into three categories according to the plane position of the foundation pit: normal area, external corner area, and long and short inclined pile area. For the external corner area with different support forms, the calculation span is corrected by the corresponding reduction coefficient. For the long and short inclined pile area, the calculation span is allocated according to the ultimate bearing capacity of a single pile, and the axial force design value of the inclined pile support at each position is matched with the actual stress characteristics.

8. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 1, characterized in that, The multi-support linkage displacement repair and optimization strategy includes: After the foundation pit deformation stabilizes, the axial force of the support is gradually increased according to the set gradient. After each load level stabilizes, the deep horizontal displacement of the foundation pit soil and the displacement of the cap beam are collected. Identify the elastic and plastic repair components in the displacement repair amount and evaluate the permanent repair effect; After the repair is completed, the load is gradually reduced to the normal operating axial force value, and the displacement rebound amount after unloading is recorded.

9. The method for controlling deformation of preloaded inclined pile supports in soft soil foundation pits according to claim 1, characterized in that, The axial force servo inclined pile support system has a built-in working condition adaptive parameter library for use in two types of strategies: graded preloading and closed-loop control. The parameter library pre-stores graded loading templates and axial force compensation coefficients corresponding to different strata, foundation pit depths, and inclined pile types; When construction begins, the system automatically matches the corresponding graded loading module and axial force compensation coefficient, and collects measured deformation data during construction to update the parameter library in real time.

10. A deformation control system for preloaded inclined pile supports in soft soil foundation pits, employing the control method described in any one of claims 1-9, characterized in that, include: The data acquisition module is equipped with an axial force sensing unit, a displacement sensing unit, and a hydraulic force transmission monitoring unit embedded in the reinforced force transmission truss. It is used to synchronously collect axial force data, support lateral displacement data, and pressure change data of the force transmission path of the main and auxiliary servo support units. The graded preloading module is equipped with a graded preloading and coordinated pressure stabilization strategy, which is used to apply preloaded axial force to each support unit in a multi-level gradient and maintain pressure stability, eliminate component assembly gaps and initial creep deformation of soil, and complete the pre-setting of axial preload displacement before excavation. The force transmission analysis and closed-loop control module is equipped with force transmission efficiency analysis and axial force closed-loop control strategy. It is used to analyze force transmission loss and calculate effective support force based on the pressure data of the force transmission path, and dynamically adjust the axial force of the main and auxiliary support units in combination with real-time displacement data to suppress the development of foundation pit displacement. The multi-support linkage repair module is configured with a multi-support linkage displacement repair optimization strategy. When the support displacement exceeds the warning threshold, it is used to start multi-unit hierarchical reloading repair, generate periodic deformation control curves and output deformation control feedback information.

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