A soft soil layer foundation pit excavation stability simulation analysis system

Abstract

The application relates to the technical field of computer-aided simulation application, and discloses a soft soil layer foundation pit excavation stability simulation analysis system, which comprises the following steps: a digital twin three-dimensional space model containing a retaining wall body, a waterproof curtain, a dewatering well group and soft soil is constructed under a unified coordinate system; earthwork excavation and dewatering operation data are integrated into working condition data packages; a potential influence area of residual pressure unloading on the inner side of the curtain toe is constructed according to the working condition data packages; a space distribution field of unloading residual pressure influence coefficients is calculated based on effective stress release, superstatic pore pressure residual and consolidation time effect reduction in the area; then, the anti-heave resistance and unloading driving stress are comprehensively considered to obtain a distribution field of anti-heave safety coefficients of the foundation pit bottom; finally, coupled simulation is performed on the unified grid, a critical safety isosurface and a maximum dangerous through area core line are extracted and spatial projection rendering is performed, and corresponding foundation pit excavation stability simulation analysis graphs are output.

Description

Technical Field

[0001] This invention relates to the field of computer-aided simulation application technology, and more specifically, to a stability simulation and analysis system for foundation pit excavation in soft soil strata. Background Technology

[0002] In deep foundation pit engineering in soft soil strata, excavation and unloading often trigger a significant redistribution of stress and seepage fields. Soft soil itself exhibits high water content, high compressibility, and low permeability, which leads to a rapid decrease in the effective vertical stress of the soil under excavation and unloading, while the dissipation of pore water pressure exhibits a significant time lag. In engineering environments facing high groundwater levels, diaphragm walls are typically used for retaining walls in conjunction with deep impermeable curtains for water stoppage, while dewatering well groups are deployed inside and outside the pit to control groundwater.

[0003] When such retaining and water-stopping systems are deeply embedded in the strata, the head distribution of the underlying confined aquifer is blocked or altered, forming a complex hydraulic flow boundary at the bottom of the curtain. As excavation progresses downwards, the descent rate of the local pumping funnel often does not match the movement rate of the soil unloading surface. Current commonly used three-dimensional numerical simulation or digital twin analysis processes mostly use "completion of excavation at a certain depth and corresponding support installation" as the basis for discrete stage division, and mainly rely on comparing the horizontal displacement inclinometer data of the diaphragm wall and surface settlement records to invert and update stratum parameters.

[0004] However, due to the delayed dissipation effect of pore water pressure in soft soil and the non-uniformity of the dewatering well group's effect, a hidden residual pressure zone objectively exists in the spatial region inside the diaphragm wall, above the bottom of the curtain wall, and below the excavation surface of the foundation pit. This zone is constrained by unloading release, lag in confined water head, and hydraulic boundary offset. Existing engineering finite element simulation models, if focusing only on wall surface displacement or pit settlement indicators and failing to separately extract and quantify the residual pressure influence zone with its temporal and spatial misalignment, can easily misjudge the lag in pore pressure and the recovery of lower water head on the heave at the bottom of the foundation pit as a result of low shallow soil modulus or insufficient lateral support stiffness. This mechanistic confusion leads to a delayed misjudgment of the overall heave resistance safety state of the foundation bottom when simulating subsequent working conditions near the pit bottom, making it difficult to objectively reveal the true risks hidden deep within the pit bottom due to the spatiotemporal misalignment of seepage and stress. Summary of the Invention

[0005] This invention provides a simulation and analysis system for the stability of foundation pit excavation in soft soil strata, which solves the technical problems mentioned in the background art.

[0006] This invention provides a simulation and analysis system for the stability of foundation pit excavation in soft soil strata. It is applied to simulation operations involving diaphragm walls, wall toe anchorages, impermeable curtains, dewatering well groups inside and outside the pit, the bottom of the soft soil pit, and the underlying confined aquifer. The system is configured to execute:

[0007] The model building module is used to build a digital twin 3D spatial model containing a composite structure in a unified coordinate system and divide it into a unified mesh to generate finite element calculation units.

[0008] The data encoding module is used to uniformly encode earthwork excavation, support formation, dewatering operation and monitoring sampling data to form an integrated construction hydraulic condition data package;

[0009] The influence zone construction module is used to construct the potential influence zone of unloaded residual pressure inside the curtain toe located inside the underground continuous wall or water-resistant curtain within the digital twin three-dimensional spatial model.

[0010] The field solving module is used to solve the spatial distribution field of the unloading residual pressure influence coefficient in the potential influence zone of the unloading residual pressure inside the curtain toe by finite element calculation element, and to calculate the distribution field of the pit bottom anti-heave safety factor based on the spatial distribution field of the unloading residual pressure influence coefficient.

[0011] The stage simulation module is used to write the spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom anti-heave safety factor into the finite element simulation result layer, and perform staged stability simulation of each construction condition containing the unloading residual pressure field on a unified mesh to form a construction condition safety factor profile cloud map.

[0012] The core line extraction module is used to extract the core line of the maximum dangerous penetration area based on the safety factor profile cloud map of the construction working condition, the critical isosurface of the safety factor and the spatial distribution field of the unloading residual pressure influence coefficient, and to perform spatial projection positioning.

[0013] The rendering output module is used to visualize and render the results of spatial projection positioning, and output the stability simulation analysis diagram of the foundation pit excavation.

[0014] The beneficial effects of this invention are as follows: This invention does not require the addition of new data acquisition equipment with manual intervention on site, nor does it rely on subjective high-precision parameter adjustment. By establishing a digital twin three-dimensional spatial model that includes the hysteresis time of soft soil pore pressure, the flow boundary around the curtain, and the movement of the unloading surface, it directly converts the unloading residual pressure drive of the deep part of the continuous wall and the bottom of the water-resistant curtain, as well as the pore pressure memory time delay, into a spatial distribution field that can be solved by a computer. This outputs a simulation analysis cloud map that directly points to the anti-heave safety factor at the bottom of the foundation pit, providing an intuitive, quantitative, and engineering-guided visual evaluation basis for the safety evolution of deep foundation pits under complex water-soil coupling conditions. Attached Figure Description

[0015] Figure 1This is a schematic diagram of the unloading residual pressure influence coefficient and the anti-heave risk identification mechanism of the present invention;

[0016] Figure 2 This is a first schematic diagram of the soft soil stratum foundation pit composite structure and the potential influence zone of unloading residual pressure according to the present invention;

[0017] Figure 3 This is a second schematic diagram of the soft soil stratum foundation pit composite structure and the potential influence zone of unloading residual pressure according to the present invention;

[0018] Figure 4 This is a third schematic diagram of the soft soil stratum foundation pit composite structure and the potential influence zone of unloading residual pressure according to the present invention. Detailed Implementation

[0019] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0020] The following is combined with Figure 1 and Figure 1 This paper provides a detailed description of a simulation and analysis system for the excavation stability of foundation pits in soft soil strata. Figure 1 This is a schematic diagram illustrating the influence coefficient of unloading residual pressure and the mechanism for identifying the risk of heave. Figure 1 This is a schematic diagram of the potential impact zone of the composite structure of the foundation pit in soft soil strata and the residual pressure after unloading. Figure 1 It is used to demonstrate the calculation and identification relationship between the spatial distribution field of the unloading residual pressure influence coefficient, the distribution field of the pit bottom anti-heave safety factor, the critical isosurface of the safety factor, and the core line of the maximum dangerous penetration zone; Figure 1 It is used to demonstrate the spatial relationship between the underground continuous wall, the wall toe embedded section, the water-tight curtain, the dewatering well group inside and outside the pit, the soft soil pit bottom, the underlying confined aquifer, the unloading boundary, and the potential impact zone of the unloading residual pressure inside the curtain toe.

[0021] A simulation and analysis system for the stability of foundation pit excavation in soft soil strata is applied to simulation operations involving diaphragm walls, wall toe embedded sections, impermeable curtains, dewatering well groups inside and outside the pit, the bottom of the soft soil pit, and the underlying confined aquifer. The system is configured to execute the following steps sequentially: Establishing a digital twin three-dimensional spatial model containing the composite structure in a unified coordinate system and dividing it into a unified mesh to generate finite element calculation units; uniformly encoding earthwork excavation, support formation, dewatering operations, and monitoring sampling data to form an integrated construction hydraulic condition data package; constructing a potential influence zone of unloaded residual pressure inside the curtain toe located within the digital twin three-dimensional spatial model; and performing finite element analysis within the potential influence zone of unloaded residual pressure inside the curtain toe. The computational unit solves for the spatial distribution field of the unloading residual pressure influence coefficient and calculates the distribution field of the pit bottom heave safety factor based on the spatial distribution field of the unloading residual pressure influence coefficient. The spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom heave safety factor are written into the finite element simulation result layer. The staged stability simulation of each construction condition containing the unloading residual pressure field is performed on a unified mesh to form a safety factor profile cloud map of the construction condition. Based on the safety factor profile cloud map of the construction condition, the core line of the maximum danger penetration zone between the critical isosurface of the safety factor and the spatial distribution field of the unloading residual pressure influence coefficient is extracted and spatially projected and located. The results of the spatial projection and location are visualized and rendered to output the pit excavation stability simulation analysis diagram.

[0022] This application adopts the first... The construction condition number and the first Each finite element calculation unit serves as a calculation index. and This only indicates a calculation index. All calculated values ​​below are converted to the same engineering measurement system before being used in calculations, ensuring that the objects being added, subtracted, multiplied, and divided correspond in numerical scale. (The following text...) Indicates taking and The larger value in Indicates taking and The smaller value in This indicates exponentiation with the natural logarithm base.

[0023] Example 1:

[0024] In one embodiment, the system uses the design control points of the foundation pit as the plane reference of the unified coordinate system and the site elevation reference as the vertical reference of the unified coordinate system. The system converts the plane boundary of the foundation pit, the axis and thickness of the diaphragm wall, the toe elevation of the wall, the thickness and bottom elevation of the waterproof curtain, the coordinates of the dewatering well group inside and outside the pit, the starting and ending elevations of the dewatering well filter pipes, the stratum interface of the soft soil layer, the weakly permeable layer and the underlying confined aquifer where the soft soil pit bottom is located, the coordinates of the internal support and the column piles, and the excavation surface at the bottom of the pit to this unified coordinate system.

[0025] When dividing the grid into a unified grid, the system performs local densification within the spatial range of the wall toe elevation, the waterstop bottom elevation, and the excavation depth below the pit bottom excavation surface, which is one times the current working depth. Let... This represents the mesh edge length of a finite element calculation unit. Let the thickness of the diaphragm wall be the given value. Then, the mesh edge length of the finite element calculation unit within this space satisfies the following condition:

[0026]

[0027] In the vertical direction, the system divides each soil layer into at least five computational soil layers. Let... The number of calculated soil layers obtained by dividing each soil layer vertically is given by the following condition:

[0028]

[0029] Obtained by uniform grid division, The thickness of the diaphragm wall was obtained. It is obtained by uniform meshing in the vertical direction. The above local refinement is only used to improve the calculation resolution near the wall toe elevation, waterstop bottom elevation, and unloading boundary, and does not change the spatial position of the composite structure in the digital twin 3D spatial model.

[0030] S201, read the plane boundary of the foundation pit, the axis and thickness of the underground continuous wall, the wall toe elevation, the thickness of the water-resistant curtain and the bottom elevation of the water-stopping surface, and generate the soil-retaining and water-stopping surface;

[0031] The system reads the plane boundary of the foundation pit and obtains the coordinate sequence of the plane boundary nodes of the foundation pit; reads the axis and thickness of the diaphragm wall and obtains the spatial position of the diaphragm wall in the unified coordinate system; reads the wall toe elevation and determines the position of the lowest point of the diaphragm wall; reads the thickness and bottom elevation of the water-stop curtain and determines the spatial position of the water-stop curtain and the bottom position of the water-stop in the unified coordinate system.

[0032] The system topologically merges the foundation pit planar boundary, the axis and thickness of the diaphragm wall, the wall toe elevation, the thickness of the waterproof curtain, and the bottom elevation of the waterstop to generate a retaining and water-stopping surface. This retaining and water-stopping surface is used to represent both the retaining force boundary of the diaphragm wall and the water-stopping boundary of the waterproof curtain. Figure 1 The combined structure of the underground continuous wall, the wall toe embedded section, and the water-resistant curtain corresponds to the retaining and water-stopping surface generated in this step.

[0033] When generating the retaining wall and water-stopping surface, the system first extracts the inner and outer surface meshes of the diaphragm wall, the inner and outer surface meshes of the water-stopping curtain, and then transforms the coordinates of the above mesh nodes to a unified coordinate system. The system uses the minimum mesh side length The coordinate difference is set as the node alignment tolerance; when the coordinate difference between two nodes is less than the node alignment tolerance, they are determined to be the same node and merged.

[0034] For the overlapping section of the diaphragm wall and the waterproof curtain, the system deletes the overlapping surfaces within the overlapping area, retaining the continuous outer waterproof boundary and the continuous inner retaining force boundary. After merging, the system performs a topological stitching check on the retaining waterproof surface to ensure that there are no free edges or overlapping surfaces, and that the normal direction uniformly points to the outside of the foundation pit. If the diaphragm wall and the waterproof curtain intersect or are misaligned, the system prioritizes merging nodes at the same location according to the node alignment tolerance, and divides the intersection boundaries that cannot be merged into independent boundary segments before writing them into the retaining waterproof surface.

[0035] S202, read the coordinates of the dewatering well group inside and outside the pit, the start and end elevations of the dewatering well filter pipes and the pumping period, and generate the hydraulic boundary;

[0036] The system reads the coordinates of the dewatering well group inside and outside the pit to determine the planar position of the dewatering well group inside and outside the pit in a unified coordinate system; reads the start and end elevations of the dewatering well filter pipes to determine the hydraulic action range of the dewatering well group inside and outside the pit in the vertical direction; and reads the pumping period to determine the operating time of the dewatering well group inside and outside the pit within each construction condition number.

[0037] For each dewatering well belonging to the dewatering well group inside and outside the pit, the system combines the coordinates of the dewatering well with the start and end elevations of the dewatering well filter pipe to form a set of hydraulic boundary nodes, and binds the pumping period to this set of hydraulic boundary nodes. If there are different pumping periods in the dewatering well group inside and outside the pit within the same construction condition number, the system writes the hydraulic boundary segments into the integrated construction hydraulic condition data package according to the timestamp, so that the dewatering operation corresponds with the earthwork excavation, support formation and monitoring sampling data. Figure 1 The elevations of the dewatering well groups inside and outside the pit, as well as the starting and ending elevations of the dewatering well filter pipes, correspond to the hydraulic boundaries generated in this step.

[0038] S203, read the stratigraphic interface of the soft soil layer, the weakly permeable layer and the underlying confined aquifer where the soft soil pit bottom is located, and form a stratigraphic body;

[0039] The system reads the stratigraphic interfaces of the soft soil layer, the weakly permeable layer, and the underlying confined aquifer at the bottom of the soft soil pit, generates a three-dimensional spatially separated surface in a unified coordinate system, and forms a stratigraphic volume by the three-dimensional spatially separated surface. Each finite element calculation unit in the stratigraphic volume records the geological properties of its associated soft soil layer, the geological properties of its weakly permeable layer, or the relevant positional relationship of its underlying confined aquifer.

[0040] The stratum provides the consolidation coefficient of soft soil, the undrained shear strength field of the current construction condition, the buoyant unit weight of the soil under the current construction condition, and the permeability parameters corresponding to the low-permeability boundary conditions of the retaining wall and water-stopping surface for subsequent calculations. The consolidation coefficient of soft soil, the undrained shear strength field of the current construction condition, and the buoyant unit weight of the soil under the current construction condition are read from the physical and mechanical property parameters corresponding to the stratum; the permeability parameters corresponding to the low-permeability boundary conditions of the retaining wall and water-stopping surface are read from the material parameters of the diaphragm wall and the impermeable curtain or from the engineering input data.

[0041] S204, read the coordinates of the internal support and column piles and set them as the structural constraint surface, and set the excavation surface at the bottom of the pit as the unloading boundary that moves with the construction conditions;

[0042] The system reads the coordinates of the internal supports and columns, and generates structural constraint surfaces according to their spatial positions in a unified coordinate system. These structural constraint surfaces are used to express the constraint effect of the internal supports and columns on the diaphragm wall, the toe anchorage, and the surrounding soil.

[0043] The system sets the excavation surface at the bottom of the pit as the unloading boundary that moves with the construction conditions. For each construction condition number, the unloading boundary corresponds to the excavation surface at the bottom of the pit after the elevation of the pit bottom surface for that construction condition number is completed. Figure 1 The excavation unloading boundary in the text corresponds to the unloading boundary in this step.

[0044] S205 integrates the retaining and water-stopping surface, hydraulic boundary, stratum, unloading boundary and structural constraint surface to form a digital twin three-dimensional spatial model.

[0045] The system integrates the retaining surface, hydraulic boundary, stratum, unloading boundary, and structural constraint surface according to their spatial positions in a unified coordinate system. During integration, the system merges topological nodes of common boundaries and records the adjacency relationship between each finite element calculation unit and the retaining surface, hydraulic boundary, stratum, unloading boundary, and structural constraint surface.

[0046] After integration, the system forms a digital twin three-dimensional spatial model. Each finite element calculation unit of the digital twin three-dimensional spatial model records at least the geometric centroid coordinates, node number, the stratum to which it belongs, the spatial relationship with the retaining wall and water-stopping surface, the spatial relationship with the hydraulic boundary, the spatial relationship with the unloading boundary, and the spatial relationship with the structural constraint surface.

[0047] Example 2:

[0048] S301, Generate construction condition number according to construction log;

[0049] The system reads the construction log and arranges the earthwork excavation, support formation, dewatering operation, and monitoring sampling data according to the event timeline. The system uses the time of change in pit bottom elevation, internal support reaching the recording activation state, change in dewatering well pumping status, or monitoring sampling data entering a stable recording state as the basis for segmentation, and generates construction condition numbers in chronological order.

[0050] When generating the construction condition number, the elevation of the pit bottom surface changes so that the difference between the actual elevation of the pit bottom and the design elevation after excavation does not exceed [a certain value]. The determination node is determined by the meter; changes in the pumping status of the dewatering well are determined by the timestamp corresponding to the pump start / stop command; the internal support reaches the recording activation state when the fluctuation range of the support axial force for three consecutive sampling periods does not exceed the average value of the corresponding support axial force. And the supporting axial force value reaches the design pre-applied axial force. The above are the determination points; the time when the monitoring and sampling data enters a stable recording period is when the range of six consecutive sampling data for the corresponding monitoring item does not exceed the full scale of the monitoring and sampling equipment. Furthermore, there is no continuous upward or downward trend as a determining factor.

[0051] The construction condition number is used to index the pit bottom elevation, condition duration, dewatering well pumping status, diaphragm wall displacement, support axial force, water level record, and pore water pressure record within the same construction phase, so that each construction condition number corresponds to a condition data package.

[0052] S302, for each construction condition number, read the pit bottom elevation, condition duration, dewatering well pumping status, diaphragm wall displacement, support axial force, water level record and pore water pressure record.

[0053] For each construction condition number, the system reads the pit bottom elevation to determine the unloading boundary, reads the condition duration to determine the calculation time for pore water pressure dissipation lag, reads the dewatering well pumping status to determine the hydraulic boundary, reads the diaphragm wall displacement to determine the deformation record of the retaining and water-stopping surface, reads the support axial force to determine the force record of the structural constraint surface, and reads the water level record and pore water pressure record to determine the actual pore water pressure of the current construction condition and the target pore water pressure of the dewatering under the same condition.

[0054] If multiple monitoring and sampling data exist within the same construction condition number, the system selects the monitoring and sampling data with complete timestamps, complete spatial coordinates, and non-empty sampling values. If time interpolation is required, the system only performs linear interpolation within the same construction condition number using monitoring and sampling data with adjacent timestamps, without crossing different construction condition numbers.

[0055] S303 binds multi-source data read within the same construction condition number to the corresponding digital twin three-dimensional spatial model according to the timestamp;

[0056] The system timestamps and binds the pit bottom elevation, duration of the condition, dewatering well pumping status, diaphragm wall displacement, support axial force, water level record, and pore water pressure record read within the same construction condition number to the corresponding digital twin 3D spatial model. The pit bottom elevation is bound to the unloading boundary, the dewatering well pumping status is bound to the hydraulic boundary, the diaphragm wall displacement is bound to the retaining wall surface, the support axial force is bound to the structural constraint surface, and the water level record and pore water pressure record are bound to the corresponding finite element calculation unit or adjacent finite element calculation unit node.

[0057] For finite element calculation units where monitoring and sampling data are not directly deployed, the system performs interpolation based on the spatial distance within a unified grid. This interpolation is only used to map the monitoring and sampling data to the digital twin 3D spatial model and does not alter the monitoring and sampling data itself.

[0058] For finite element calculation units that do not directly deploy monitoring and sampling data, the system uses inverse distance weighted interpolation to map discrete monitoring and sampling data onto each finite element calculation unit. Let... Indicates the first Interpolation results for each finite element calculation unit. Indicates the first The sampling values ​​of each monitoring point Indicates the first The geometric centroid of the finite element calculation unit and the first The three-dimensional straight-line distance between the monitoring points This represents the distance weighting index, with a preferred value of [value missing]. ,but:

[0059]

[0060] The interpolation search radius is three times the average grid side length, and only monitoring points within the search radius participate in the calculation. If there are no valid monitoring points within the search radius, the system takes the values ​​of adjacent finite element calculation units in the same stratum and performs linear interpolation to supplement them. If the sampling value of a monitoring point is empty, the timestamp is missing, or the spatial coordinates are missing, then the monitoring point does not participate in the interpolation.

[0061] S304, after the construction phase corresponding to the construction condition number is completed, it is encapsulated to form a condition data packet;

[0062] After the construction phase corresponding to the construction condition number is completed, the system encapsulates the pit bottom elevation, condition duration, dewatering well pumping status, diaphragm wall displacement, support axial force, water level record, and pore water pressure record that have been bound to the digital twin 3D spatial model within the construction condition number into a condition data package.

[0063] The starting point for analyzing the working condition data package is set to the unloading boundary stabilization recording time of the previous construction condition. The unloading boundary stabilization recording time is the moment when the excavation face at the bottom of the pit stops moving in the previous construction condition, and the unloading boundary does not undergo a spatial positional change exceeding the monitoring accuracy within the preset monitoring duration. The preset monitoring duration is six consecutive monitoring sampling intervals. The monitoring accuracy is read from the factory calibration parameters or calibration records of the sampling equipment corresponding to the monitoring sampling data; the accuracy threshold for displacement and stress monitoring is taken as the full-scale measurement range of the corresponding sampling equipment. The accuracy threshold for water level monitoring is taken as follows: Meters. When the fluctuation range of the displacement monitoring data corresponding to the unloading boundary does not exceed the monitoring accuracy within the preset monitoring time, the system determines that this moment is the stable recording moment of the unloading boundary.

[0064] The analysis endpoint of the working condition data package is set as the moment when the pit bottom elevation corresponding to this working condition is reached and the internal support reaches the recording activation state. The moment when the internal support reaches the recording activation state is the moment when the axial force of the internal support in this construction working condition forms a stable record and can be bound to the structural constraint surface; in one embodiment, the criterion for determining that the internal support reaches the recording activation state is that the fluctuation amplitude of the support axial force of the corresponding internal support in three consecutive sampling periods does not exceed the average value of the corresponding support axial force. Furthermore, the axial force value of the support reaches the design pre-applied axial force. That's all. If the current construction condition number does not involve internal support construction, the analysis endpoint for the condition data package will be the moment when the pit bottom excavation is completed and the dewatering well pumping status is stable.

[0065] Example 3:

[0066] S401, scan segment by segment along the inner side of the diaphragm wall to extract the wall toe elevation and the bottom elevation of the water-stop curtain.

[0067] The system scans the inner surface of the diaphragm wall segment by segment. The endpoints of each segment are determined by the boundary nodes of a unified grid. When there are corners, curves, or thickness changes in the axis of the diaphragm wall, the system uses the corner points, curve control points, or thickness change points as the endpoints of the segments.

[0068] During segment-by-segment scanning, the length of a single straight segment does not exceed twice the side length of the grid along the thickness direction of the diaphragm wall. For locations where the diaphragm wall axis has corners, the system generates vertical sections perpendicular to the tangent directions of the axis on both sides of the corner, using the corner vertex as the dividing point. For locations where the diaphragm wall axis has curved segments, the system generates vertical sections per segment... A central angle corresponds to a segment for generating a vertical cross section; for locations where the thickness changes, the system uses the point of thickness change as the endpoint of the segment and generates the corresponding vertical cross section.

[0069] Within each section of the diaphragm wall, the system extracts the toe elevation and the bottom elevation of the waterproof curtain. The toe elevation is used to determine the location of the toe anchoring section, and the bottom elevation of the waterproof curtain is used to determine the location of the bottom of the waterproof curtain's waterproof seal. Figure 1 The wall toe embedment section and the bottom of the waterproof curtain together define the space range of the potential impact zone of unloading residual pressure on the inner side of the curtain toe, close to the lower part.

[0070] S402, generate a vertical section intersecting the unloading boundary on the inner side of each section, and determine the horizontal inner extension distance extending into the pit according to the excavation depth of the current working condition.

[0071] The system generates a vertical section on the inner side of each section of the diaphragm wall. The vertical section intersects with the unloading boundary corresponding to the current construction condition and extends downward through the bottom elevation of the waterstop and near the top surface of the underlying confined aquifer.

[0072] The planar direction of each vertical section is perpendicular to the tangent direction of the corresponding segment's diaphragm wall axis and extends along the inner side of the diaphragm wall toward the interior of the excavation pit. The vertical extent of all vertical sections covers the area from the site elevation datum to at least one excavation depth below the top surface of the underlying confined aquifer, allowing the vertical sections to simultaneously pass through the unloading boundary, the bottom elevation of the waterstop, the location of the wall toe elevation, and the top surface of the underlying confined aquifer.

[0073] The system determines the horizontal extension distance into the foundation pit based on the current excavation depth. Let... This indicates the excavation depth under the current working conditions. This represents the horizontal straight-line distance from the inner side of the diaphragm wall to the center line of the foundation pit. Let represent the horizontal inward extension distance extending into the foundation pit, then:

[0074]

[0075] The elevation of the pit bottom is determined by the current construction conditions and the site elevation benchmark. The plane position of the foundation pit's plane boundary and the inner surface of the diaphragm wall in a unified coordinate system is determined.

[0076] S403 is a finite element calculation unit that meets the geological properties of soft soil or weakly permeable layer and is located above the boundary of the underlying confined aquifer. It is marked as the potential influence zone of unloading residual pressure inside the curtain toe.

[0077] Within the space defined by the underground continuous wall or water-resistant curtain, the vertical section intersecting with the unloading boundary, the horizontal extension distance extending into the foundation pit, the location of the wall toe elevation, the bottom elevation of the water-stopping curtain, and the upper boundary of the underlying confined aquifer, the system reads the geological properties and spatial location of each finite element calculation unit.

[0078] set up Indicates the first The potential impact zone of residual pressure unloading inside the curtain toe within each construction condition number. Indicates the first Geological properties of each finite element calculation unit This represents a set of geological properties of soft soil layers or weakly permeable layers. Indicates the first The geometric centroid elevation of each finite element calculation unit. This indicates the elevation of the upper boundary of the underlying confined aquifer. Indicates the first The horizontal inner extension distance of each finite element calculation element relative to the inner surface of the diaphragm wall Indicates the first The distance from each finite element calculation unit to the location of the wall toe elevation. Indicates the first The distance from each finite element calculation unit to the unloading boundary. Indicates the first The distance from each finite element calculation unit to the starting and ending elevations of the dewatering well filter pipe is used to mark the potential influence zone of the unloading residual pressure inside the curtain toe as follows:

[0079] ;

[0080] Geological attributes bound to the stratigraphic body are read. Read from the geometric centroid coordinates of the finite element calculation unit. Read from the upper boundary of the underlying confined aquifer. , , and All are calculated from spatial geometric relationships in a unified coordinate system. Figure 1 The area enclosed by the dashed line corresponds to the potential impact zone of unloading residual pressure inside the toe of the curtain.

[0081] in, For the first The vertical distance from the geometric centroid of each finite element calculation element to the horizontal plane where the wall toe elevation is located. The value is positive when the finite element calculation element is above the wall toe elevation and negative when it is below the wall toe elevation. For the first The geometric centroid of the finite element calculation unit is... Each construction condition number corresponds to the vertical distance on the horizontal plane where the unloading boundary is located. The value is positive when the finite element calculation unit is below the unloading boundary and negative when it is above the unloading boundary. Therefore, This indicates that the finite element calculation unit is located above or at the same level as the wall toe elevation. This indicates that the finite element calculation unit is located below or flush with the unloading boundary.

[0082] For the first The spatial seepage path length from the geometric centroid of a finite element unit to the starting and ending elevations of the filter pipe of the nearest precipitation well is calculated. Let... Indicates from the first Candidate seepage paths from the geometric centroid of a finite element unit to the starting and ending elevations of the filter pipe in the dewatering well. This represents the set of candidate seepage paths that are continuously distributed along the formation permeability coefficient and follow the direction of the hydraulic gradient. Let the path coordinates on the candidate seepage path be represented, then:

[0083]

[0084] If a candidate seepage path crosses different formations, the system connects the candidate seepage paths at the formation interface according to the head continuity condition, and uses the shortest seepage path as the boundary path. The final value is determined by the path integral. This indicates that a finite element calculation unit has a computable seepage path; if no computable seepage path exists, the finite element calculation unit is not marked as the potential influence zone of unloaded residual pressure inside the curtain toe.

[0085] S404, for each finite element calculation unit in the potential influence zone of unloading residual pressure inside the curtain toe, record the spatial geometric relationship between the finite element calculation unit and the position of the wall toe elevation, the unloading boundary and the position of the start and end elevation of the dewatering well filter pipe.

[0086] For each finite element calculation unit within the potential influence zone of unloading residual pressure inside the curtain toe, the system records the three-dimensional straight-line distance and vertical height difference from the finite element calculation unit to the wall toe elevation, the shortest vertical distance from the finite element calculation unit to the unloading boundary, and the spatial seepage path length from the finite element calculation unit to the starting and ending elevations of the dewatering well filter pipe.

[0087] The aforementioned spatial geometric relationships are written into the attribute fields of the finite element calculation unit for subsequent calculations of drainage path length, the deviation between the actual pore water pressure under the current construction condition and the target pore water pressure under the same condition, and for forming the wall toe projection line generated by the wall toe elevation, the pit bottom projection line generated by the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit.

[0088] Example 4:

[0089] The system calculates the spatial distribution field of the unloading residual pressure influence coefficient in the potential influence zone of the unloading residual pressure inside the curtain toe, and calculates the distribution field of the pit bottom anti-heave safety factor based on the spatial distribution field of the unloading residual pressure influence coefficient. Figure 2 The process of forming the spatial distribution field of the unloading residual pressure influence coefficient by coupling the effective stress release coefficient, the residual coefficient of excess pore pressure and the consolidation time effect reduction coefficient; Figure 3 This corresponds to the process of calculating the distribution field of the pit bottom heave safety factor based on the passive heave resistance and the driving stress of pit bottom heave.

[0090] In this embodiment, the unloading residual pressure refers to the additional unloading effect formed in the soil inside the wall toe during the unloading process of soft soil foundation pit excavation, due to the coupling of the effective stress release of the soil and the residual excess pore pressure caused by the lag in precipitation. The unloading residual pressure differs from both the stress release from excavation and the residual excess pore pressure alone; rather, it is a coupled effect jointly defined by the effective stress release, the residual excess pore pressure, and the reduction due to consolidation time. The spatial distribution field of the unloading residual pressure influence coefficient is used to quantify the spatial strength of this additional unloading effect; a larger value indicates a more significant additional unloading effect at the corresponding location.

[0091] S501, combined with stress calculation tolerance, calculates the effective stress release coefficient based on the change in the initial vertical effective stress before excavation and the current vertical effective stress under construction conditions;

[0092] The system reads the initial effective vertical stress before excavation and the effective vertical stress under the current construction condition. The initial effective vertical stress before excavation is determined by the self-weight stress of the stratum and the pore water pressure before excavation; the effective vertical stress under the current construction condition is determined by the coupled field of stress and seepage under the current construction condition or by the inversion results of monitoring and sampling data under the current construction condition. Let... This represents the initial effective vertical stress before excavation. This indicates the effective vertical stress under the current construction conditions. Indicates the tolerance for stress calculation. Let the effective stress relief coefficient be:

[0093]

[0094] The stress calculation tolerance is used to prevent division by zero when the initial effective vertical stress before excavation is close to zero. The preferred range for the stress calculation tolerance is as follows: kPa to kPa. If the initial effective vertical stress before excavation is not greater than zero, the system uses the stress calculation tolerance as the denominator correction term; if the current effective vertical stress is not less than the initial effective vertical stress before excavation, the effective stress release coefficient is zero.

[0095] S502, combined with the tolerance of pore pressure calculation, calculates the residual coefficient of excess pore pressure based on the deviation between the actual pore water pressure under the current construction conditions and the target pore water pressure under the same conditions.

[0096] The system reads the actual pore water pressure under the current construction condition and the target pore water pressure for the same construction condition. The actual pore water pressure under the current construction condition is determined by the pore water pressure record, the result of the coupled field solution of stress and seepage, or the spatial interpolation result of both; the target pore water pressure for the same construction condition is determined by the pumping status of the dewatering well, the water level record, and the dewatering operation target. Let... This indicates the actual pore water pressure under the current construction conditions. This indicates the pore water pressure of the target precipitation under the same working conditions. This indicates the elevation of the pit bottom corresponding to the current construction conditions. Indicates the first The geometric centroid elevation of each finite element calculation unit. Indicates the specific gravity of water. This indicates the tolerance for pore pressure calculation. Let represent the residual coefficient of excess pore pressure, then:

[0097]

[0098] The preferred value for water density is Thousand Newtons per cubic meter. The pore pressure calculation tolerance is used to prevent the denominator from being zero; the preferred range for the pore pressure calculation tolerance is... kPa to kPa. If the actual pore water pressure under the current construction conditions is not greater than the target pore water pressure under the same conditions, then the residual coefficient of excess pore pressure is taken as zero.

[0099] The target pore water pressure for precipitation under the same operating conditions is determined according to the following rules. First, the system determines the pore water pressure based on the first rule. Calculate the design drawdown corresponding to the pumping status of each dewatering well within each construction condition number, and calculate the target pore water pressure at the filter pipe location of each dewatering well. This indicates the target pore water pressure at the location of the filter pipe in the dewatering well. This indicates the elevation of the midpoint of the filter pipe in the dewatering well. Indicates the first For each construction condition number corresponding to the design precipitation water level elevation, then:

[0100]

[0101] For finite element calculation units without directly deployed dewatering wells, the system employs a method combining steady-state seepage analytical solutions with spatial linear interpolation. Using the target pore water pressure of each dewatering well as known points, the system calculates the target pore water pressure of the corresponding finite element calculation unit under the same working condition, weighted by the horizontal distance between the finite element calculation unit and the dewatering well. Interpolation calculations are performed only within the same formation body; when crossing formation bodies, the system uses the hydraulic head continuity condition at the formation interface for connection, and assigns the target pore water pressure after connection to the specified value. .

[0102] S503, based on the consolidation coefficient of soft soil, the length of the drainage path and the duration of the current construction conditions, calculates the reduction factor of the consolidation time effect that reflects the lag of pore water pressure dissipation;

[0103] The system reads the soft soil consolidation coefficient, drainage path length, and the duration of the current construction condition. The soft soil consolidation coefficient is read from the physical and mechanical properties of the strata; the drainage path length is determined by the... The spatial distance from each finite element calculation unit to the nearest free drainage surface or the start and end elevations of the filter pipe in the dewatering well is determined; the duration of the current construction condition is read from the condition data packet. Let... This represents the consolidation coefficient of soft soil. Indicates the length of the drainage path. Indicates the duration of the current construction condition. This represents the calculation tolerance for the square of the drainage path length. Let represent the consolidation time effect reduction factor, then:

[0104]

[0105] The tolerance for calculating the square of the drainage path length is used to avoid division by zero when the drainage path length is zero. The preferred range for the tolerance of the square of the drainage path length is... to The coefficient is determined based on the square of the minimum recognizable drainage path length in the unified grid. The longer the duration of the current construction condition or the shorter the drainage path length, the smaller the consolidation time effect reduction factor; the shorter the duration of the current construction condition or the longer the drainage path length, the closer the consolidation time effect reduction factor is to one.

[0106] The tolerance for calculating the square of the drainage path length is determined based on the smallest element size of the uniform mesh, preferably taking the square of the smallest mesh side length. The factor is used as the benchmark value for calculating tolerance, and is limited to... to Within the range. When the distance between the finite element calculation unit and the nearest free drainage surface or the start and end elevations of the dewatering well filter pipe is zero, the system uses the calculation tolerance of the square of the drainage path length instead of the square of the drainage path length to participate in the calculation of the consolidation time effect reduction factor; when the square of the drainage path length is greater than the calculation tolerance of the square of the drainage path length, the system directly uses the actual calculated value to participate in the calculation.

[0107] S504, coupled with the effective stress release coefficient, the residual coefficient of excess pore pressure and the consolidation time effect reduction coefficient, constructs the spatial distribution field of the unloading residual pressure influence coefficient;

[0108] The system couples the effective stress release coefficient, residual excess pore pressure coefficient, and consolidation time effect reduction coefficient within the potential influence zone of unloaded residual pressure inside the curtain toe. Let... This indicates the area determination value for the potential impact zone of unloading residual pressure inside the curtain toe; when the... When a finite element calculation element belongs to the potential influence zone of unloaded residual pressure inside the curtain toe When the first When the finite element calculation element does not belong to the potential influence zone of unloading residual pressure inside the curtain toe .set up Indicates the first The finite element calculation unit in the first The spatial distribution field values ​​of the unloading residual pressure influence coefficient within each construction condition number are as follows:

[0109]

[0110] The system will include all finite element calculation units. The spatial distribution field of the unloading residual pressure influence coefficient is written according to the spatial position in a unified coordinate system. Let... Indicates the first Spatial distribution field of the unloading residual pressure influence coefficient within each construction condition number. Indicates the first The geometric centroid coordinates of a finite element calculation element are then:

[0111]

[0112] The results were obtained from the marking of the potential influence zone of unloaded residual pressure inside the curtain toe. Calculated from the effective stress relief coefficient, It was obtained from the residual coefficient of excess pore pressure. It is obtained from the consolidation time effect reduction factor.

[0113] S505, the stress release effect of the spatial distribution field of the comprehensive excavation depth load, residual pore water pressure and unloading residual pressure influence coefficient is used to determine the driving stress of pit bottom heave.

[0114] The system determines the stress release effect of the spatial distribution field of excavation depth load, residual pore water pressure, and unloading residual pressure influence coefficient. Let... This indicates the buoyant unit weight of the soil under the current construction conditions. If the load represents the excavation depth, then:

[0115]

[0116] From the The stratum to which the finite element calculation unit belongs is in the... Reading physical and mechanical property parameters under each construction condition number; The elevation of the pit bottom is determined by the current construction conditions. The residual pore water pressure is determined by... Confirmed. To avoid double-counting the changes in excavation depth load, initial vertical effective stress before excavation, and current vertical effective stress under construction conditions, the stress release effect of the spatial distribution field of the unloading residual pressure influence coefficient is calculated using the non-negative residual stress release amount after deducting the excavation depth load. Let... Let the driving stress of the pit bottom heave be:

[0117]

[0118] In the above formula, the first term is the excavation depth load, the second term is the residual pore water pressure, and the third term is the stress release effect of the spatial distribution field of the unloading residual pressure influence coefficient. Figure 3 The driving stress for the heave at the bottom of the pit corresponds to this calculated relationship. Figure 1 The spatial location of residual pore pressure and confined water around or uplift after the lag of precipitation corresponds to the second and third items.

[0119] The mechanical logic for the third deduction of the excavation depth load is as follows: The difference between the initial effective vertical stress before excavation and the effective vertical stress under the current construction conditions already includes the stress release corresponding to the self-weight of the soil removed during excavation; this stress release has already been included in the pit bottom heave driving stress by the first item, the excavation depth load. If all effective stress release is directly multiplied by the spatial distribution field value of the unloading residual pressure influence coefficient and then superimposed, the stress release corresponding to the self-weight of the soil removed during excavation will be repeatedly included. Therefore, the system deducts the excavation depth load from the total effective stress release, and only includes the remaining additional stress release caused by the unloading residual pressure and the additional unloading effect in the pit bottom heave driving stress. This is used to ensure that the residual stress release amount does not take a negative value, thus avoiding unreasonable results that offset the excavation depth load.

[0120] S506, based on the bearing capacity coefficient of soft clay foundation, the undrained shear strength field under the current construction conditions and the shear resistance of the wall-soil interface, determine the passive resistance to heave at the bottom of the pit;

[0121] The system reads the bearing capacity coefficient of the soft clay foundation, the undrained shear strength field under the current construction conditions, and the shear resistance at the wall-soil interface. The optimal value for the bearing capacity coefficient of the soft clay foundation is [value to be inserted here]. The undrained shear strength field under the current construction conditions is obtained from the physical and mechanical properties of the stratum, monitoring and sampling data, or the results of solving the coupled field of stress and seepage. The shear resistance at the wall-soil interface is read from the finite element calculation units at the contact positions between the diaphragm wall, the wall toe embedded section, and the stratum, and mapped to the finite element calculation units participating in the heave resistance calculation.

[0122] The shear resistance at the wall-soil interface is the shear strength value of the interface between the diaphragm wall or impermeable curtain and the soil mass, and it consists of the interfacial cohesion and the frictional resistance corresponding to the interfacial friction angle. Let... This indicates the cohesion at the wall-soil interface at the corresponding location. This represents the effective normal stress at the corresponding location. Let represent the friction angle of the wall-soil interface at the corresponding location. The shear resistance of the wall-soil interface is then calculated using the following formula:

[0123]

[0124] During spatial mapping, the system assumes the heave slip path at the pit bottom is a circular arc sliding surface centered at the wall toe. Based on the proportion of the wall-soil contact section length traversed by the heave slip path to the total slip path length, the system weighted interpolates the wall-soil interface shear resistance to each finite element unit involved in the heave calculation. During numerical conversion, the system converts the wall-soil interface shear resistance according to the ratio of the slip surface area to the bottom area of ​​the finite element unit, ensuring that the converted wall-soil interface shear resistance is comparable to... Perform algebraic addition directly.

[0125] set up This represents the bearing capacity coefficient of soft clay foundation. This indicates the undrained shear strength field under the current construction conditions in the [missing information - likely a specific location or event]. The values ​​at each finite element calculation element Indicates the shear resistance at the wall-soil interface. If the bottom of the pit passively resists the uplift resistance, then:

[0126]

[0127] Before entering the above formula, the system performs spatial interpolation based on the wall-soil contact range traversed by the anti-uplift slippage path, and converts it into a form that can be compared with... The values ​​that are directly added together. Figure 3The passive resistance to uplift at the bottom of the pit corresponds to this calculated relationship.

[0128] S507, based on the passive resistance to heave at the bottom of the pit, the driving stress of heave at the bottom of the pit, and the safety factor calculation tolerance, calculate and obtain the distribution field of the safety factor for heave at the bottom of the pit;

[0129] The system calculates the value of the pit bottom heave resistance, pit bottom heave driving stress, and safety factor calculation tolerance based on the passive heave resistance at the pit bottom, the driving stress at the pit bottom, and the safety factor calculation tolerance. Let... This indicates the tolerance for safety factor calculation. Indicates the first The finite element calculation unit in the first The distribution field values ​​of the pit bottom heave safety factor within each construction condition number are as follows:

[0130]

[0131] The safety factor calculation tolerance is used to avoid division by zero when the driving stress of pit bottom heave approaches zero. The preferred range for the safety factor calculation tolerance is as follows: kPa to kPa. The system will use all finite element calculation elements. The distribution field of the pit bottom heave resistance safety factor is written according to the spatial location in a unified coordinate system. Let... Indicates the first The distribution field of the pit bottom heave safety factor within each construction condition number is as follows:

[0132]

[0133] When the passive resistance to heave at the bottom of the pit is greater than the driving stress of heave at the bottom of the pit, the distribution field of the safety factor for heave resistance at the bottom of the pit is greater than one; when the passive resistance to heave at the bottom of the pit is close to the driving stress of heave at the bottom of the pit, the distribution field of the safety factor for heave resistance at the bottom of the pit is close to the critical threshold of the safety factor; when the passive resistance to heave at the bottom of the pit is less than the driving stress of heave at the bottom of the pit, the distribution field of the safety factor for heave resistance at the bottom of the pit is less than one.

[0134] The preferred value for the critical threshold of the safety factor is This corresponds to a state of ultimate equilibrium between the passive resistance to heave at the bottom of the pit and the driving stress of heave at the bottom. When the value of the safety factor distribution field for heave resistance at the bottom of the pit is less than the critical threshold, the system determines that there is a risk of heave instability at the corresponding location; when the value of the safety factor distribution field for heave resistance at the bottom of the pit is not less than the critical threshold, the system determines that the corresponding location is not below the ultimate equilibrium state. The preferred value for the bearing capacity coefficient of soft clay foundation is [value missing]. Suitable for aspect ratios greater than For elongated foundation pits; for square or circular foundation pits, the preferred bearing capacity coefficient for soft clay foundations is [value missing]. For rectangular foundation pits, the bearing capacity coefficient of soft clay foundation is determined based on the aspect ratio. to Linear interpolation is used to determine the relationship between them.

[0135] Example 5:

[0136] In this embodiment, the system first writes the spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom heave safety factor into the finite element simulation result layer based on the calculation results of S501 to S507. Then, it performs staged stability simulation of each construction condition containing the unloading residual pressure field on a unified mesh. After the solution is completed, the inputs of S501 and S502 are updated with the vertical effective stress and actual pore water pressure of the current construction condition obtained from the solution, and S501 to S507 are executed again to update the pit bottom heave safety factor distribution field under the same construction condition number. Thus, the pit bottom heave safety factor distribution field has both the initial calculation results written into the finite element simulation result layer and the updated calculation results after solving the coupled field of stress and seepage, both of which are distinguished by the construction condition number and the finite element calculation unit index.

[0137] S601, according to the time sequence of the data packets of each working condition, applies the low permeability boundary conditions of the unloading boundary, hydraulic boundary and retaining water-stop surface to the current construction working condition in sequence.

[0138] The system reads the data packets for each construction condition in chronological order according to their construction condition numbers. For the current construction condition, the system first applies an unloading boundary, releasing the finite element calculation units above the current pit bottom elevation that have been removed by earthwork excavation from the load-bearing calculation, and then applies a change in the excavation depth load at the unloading boundary location.

[0139] The release of finite element calculation elements corresponding to earthwork excavation is achieved using the element birth and death method. For the first... For each construction case number, the system multiplies the stiffness matrix of the finite element calculation unit to be excavated above the pit bottom elevation in the first iteration step of that construction case number. The reduction factor is used to exclude this finite element calculation unit from subsequent load-bearing calculations. Stress release for the excavation unit is performed in a step-by-step manner, with all stress release completed in three iterations within a single construction case number. The stress release ratio in each step is as follows: , and The released stress is applied to the nodes of the finite element calculation unit corresponding to the unloading boundary in the form of equivalent nodal forces, serving as the external load input of the unloading boundary.

[0140] Subsequently, the system applies hydraulic boundaries. Based on the pumping status of the dewatering wells, the coordinates of the dewatering well group inside and outside the pit, the start and end elevations of the dewatering well filter pipes, and the pumping period, the system applies hydraulic boundaries to the corresponding finite element calculation unit nodes.

[0141] Finally, the system applies low-permeability boundary conditions to the retaining wall and water-stopping surface. The permeability parameters corresponding to the low-permeability boundary conditions of the retaining wall and water-stopping surface are read from the material parameters or engineering input data of the diaphragm wall and water-stopping curtain, and written into the boundary of the finite element calculation unit corresponding to the retaining wall and water-stopping surface. Figure 1 The spatial relationship between the underground continuous wall, the impermeable curtain, and the dewatering well group inside and outside the pit corresponds to the combination relationship of the low permeability boundary conditions of the unloading boundary, hydraulic boundary, and retaining and water-stopping surface in this step.

[0142] S602 solves the coupled field of stress and seepage on a unified grid, and performs numerical coupled simulation of the unloading and heave at the bottom of the pit, the passive zone pressure at the toe of the wall, and the uplift effect of the confined water.

[0143] In the numerical coupling simulation, the soft soil layer, weakly permeable layer, and underlying confined aquifer soil in the strata were all modeled using a modified Cambridge constitutive model with eight-node hexahedral reduced integral solid elements. The diaphragm wall, impermeable curtain, internal supports, and piles were all modeled using a linear elastic constitutive model, with the diaphragm wall and impermeable curtain using four-node shell elements, and the internal supports and piles using two-node beam elements. Surface-to-surface contact elements were used at the contact points between the diaphragm wall / impermeable curtain and the surrounding strata. The normal direction of the contact elements used a hard contact algorithm, while the tangential direction used a Coulomb friction algorithm. The friction coefficient was determined by the friction angle at the wall-soil interface. These element types and contact relationships were used to assemble the displacement-related discrete matrix, the coupling discrete matrix, and the pore water pressure-related discrete matrix.

[0144] The system solves for the coupled stress and seepage field on a uniform grid. Let... Indicates the first The soil skeleton displacement increment under each construction condition number Indicates the first The increase in pore water pressure under each construction condition number This represents the displacement-related discrete matrix assembled from the formation volume, structural constraint surfaces, and unloading boundaries. This represents the discrete matrix indicating the coupling between stress and seepage. This represents the discrete matrix related to pore water pressure, assembled from the hydraulic boundary, the low-permeability boundary conditions of the retaining wall, and the permeability parameters of the formation. This represents the external action term corresponding to the stress release effect of the spatial distribution field of the unloading boundary, pit bottom heave driving stress, and unloading residual pressure influence coefficient. Let the external action terms corresponding to the hydraulic boundary and residual pore water pressure be represented. Then, the coupled field of stress and seepage can be solved by the following formula:

[0145]

[0146]

[0147] To clarify the formation mechanism of the unloaded residual pressure field, the stress release effect of the spatial distribution field of the unloaded residual pressure influence coefficient is incorporated into the system. And write the residual pore water pressure into .set up This indicates the external action term when the stress release effect of the spatial distribution field of the unloading residual pressure influence coefficient is not included. This indicates the external action term when the residual pore water pressure is not included. This represents the stress driven by the bulge at the bottom of the pit by each finite element calculation element. The assembled column vector, This represents the residual pore water pressure calculated from each finite element unit. The assembled column vector, and Let the mapping matrix be formed by the unified grid topology, then:

[0148]

[0149]

[0150] It is formed by the external forces acting on the foundation under the current construction conditions, including the unloading boundary, structural constraint surface, and retaining and water-stopping surface. The foundation is formed by the low permeability boundary conditions of the hydraulic boundary and the retaining and water-stopping surface under the current construction conditions; Used to distribute the driving stress of pit bottom heave to the nodes of finite element calculation units involved in displacement solving; Used to distribute the residual pore water pressure to the nodes of the finite element calculation units involved in solving the pore water pressure problem.

[0151] Mapping matrix and Both are used to distribute the scalar physical quantities at the center of the finite element calculation unit to each node of the finite element calculation unit. The distribution weights are calculated using the trilinear shape function of the eight-node hexahedral element. For the first... Each finite element calculation unit, driving stress of pit bottom heave. pass Mapped to the eight nodes of this finite element computational unit, the weight assigned to each node is the value of the corresponding node's shape function at the geometric centroid of the finite element computational unit, and the sum of all node weights is... .

[0152] Mapping matrix of pore water pressure residual Adopted and The same shape function weighting construction rule is used, except that the assigned physical quantities are replaced with the residual pore water pressure of the finite element calculation unit. Therefore, the driving stress of pit bottom heave and the residual pore water pressure of the finite element calculation element are both applied to the nodes of the finite element calculation element participating in the solution according to the unified mesh topology.

[0153] The system employs an iterative approach to solve for the coupled field of stress and seepage, using residual convergence as the stopping condition. Let... Indicates the first The residual of the next iteration Represents the initial iteration residual. This indicates the tolerance for residual calculation. Let the convergence threshold be denoted as:

[0154]

[0155] The residual calculation tolerance is used to avoid division by zero when the initial iteration residual is close to zero. The preferred range of values ​​for the residual calculation tolerance is... to The convergence threshold is used to determine whether the iteration has stopped. The preferred range for the convergence threshold is... to When the above equation is satisfied, the system determines that the coupled field of stress and seepage has converged.

[0156] The coupled field of stress and seepage is solved using a fully coupled implicit iterative algorithm. The displacement field and pore water pressure field are updated synchronously during the iteration process within each construction case number. The initial values ​​for iteration are the displacement field and pore water pressure field after convergence in the previous construction case number; the initial values ​​for the first construction case number are the calculation results corresponding to the initial ground stress equilibrium and initial hydrostatic pressure state. After each coupled iteration, the system synchronously updates the vertical effective stress and actual pore water pressure of the current construction case, and recalculates the spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom heave safety factor. The updated results are then substituted into the external action terms of the next iteration.

[0157] After solving for the coupled field of stress and seepage, the system... and Read the first The effective stress increment and pore water pressure increment corresponding to each finite element calculation element. Let... This indicates the increase in effective vertical stress under the current construction conditions. The value represents the actual increase in pore water pressure under the current construction condition. Therefore, the updated effective vertical stress and the updated actual pore water pressure under the current construction condition are as follows:

[0158]

[0159]

[0160] The system will As the effective vertical stress under the current construction conditions, As the actual pore water pressure under the current construction conditions, S501 to S507 were re-executed, and the corresponding data in the finite element simulation result layer under the same construction condition number was covered with the newly obtained pit bottom anti-heave safety factor distribution field.

[0161] S603, after the solution is completed, extract the distribution data of the pit bottom heave safety factor distribution field of the inner side of the underground continuous wall, the center position of the unloading boundary, the depth of the internal support, and the position of the top surface of the underlying confined aquifer.

[0162] After the solution is completed, the system locates the inner side of the diaphragm wall, the center of the unloading boundary, the depth of the internal support, and the top surface of the underlying confined aquifer in the digital twin 3D spatial model. The inner side of the diaphragm wall is determined by the boundary of the finite element calculation unit on the side of the diaphragm wall facing the inside of the pit; the center of the unloading boundary is determined by the bottom elevation of the pit and the planar boundary of the pit corresponding to the current construction condition; the depth of the internal support is determined by the elevation of the internal support in the coordinates of the internal support and the column pile; the top surface of the underlying confined aquifer is determined by the stratum interface of the underlying confined aquifer.

[0163] The system extracts the distribution data of the pit bottom heave safety factor at the aforementioned locations from the finite element simulation result layer. If no finite element calculation element nodes completely overlap at the aforementioned locations, the system uses the spatial interpolation results of adjacent finite element calculation elements as the distribution data of the pit bottom heave safety factor at that location.

[0164] S604, the distributed data is spatially projected along the inner side of the underground continuous wall and the unloading boundary to form a construction condition safety factor profile cloud map corresponding to the current construction condition.

[0165] The system spatially projects the distribution data of the pit bottom heave safety factor at the center of the diaphragm wall, the unloading boundary, the depth of the internal support, and the top surface of the underlying confined aquifer along the inner side of the diaphragm wall and the unloading boundary. The profile of the spatial projection passes through the inner side of the diaphragm wall, the unloading boundary, the bottom elevation of the waterstop, and the top surface of the underlying confined aquifer.

[0166] The system interpolates the discrete distribution data of the pit bottom heave resistance safety factor field within the projected profile into a continuous two-dimensional matrix, and renders it with continuous color bands to form a construction condition safety factor profile cloud map corresponding to the current construction condition. The construction condition safety factor profile cloud map also saves its corresponding construction condition number, projected profile position, and backtracking relationship with the pit bottom heave resistance safety factor distribution field in the unified grid. This allows for subsequent extraction of the critical isosurface of the safety factor to trace back from the construction condition safety factor profile cloud map to the three-dimensional pit bottom heave resistance safety factor distribution field.

[0167] The spatial projection of the safety factor profile cloud map under construction conditions adopts orthographic projection, with the projection direction perpendicular to the plane containing the vertical section. The projection scale maintains a one-to-one correspondence with the unified coordinate system. Continuous color bands use a blue, green, yellow, and red gradient. The lower limit of the color band value is taken as the minimum value of the pit bottom heave resistance safety factor distribution field, and the upper limit of the color band value is taken as the maximum value of the pit bottom heave resistance safety factor distribution field. For rendering the spatial distribution field of the unloading residual pressure influence coefficient, the color band value range is... The maximum value of the spatial distribution field of the influence coefficient of the corresponding unloading residual pressure is obtained. Linear interpolation is used for the color band interpolation, and the color transition between adjacent numerical nodes is continuous. The numerical intervals marked in the legend are divided into ten intervals according to the color band range.

[0168] Example 6:

[0169] Figure 4 This illustrates the relationship between the boundary of the critical isosurface of the safety factor, the core line of the maximum danger penetration zone, the wall toe projection line generated from the wall toe elevation, the pit bottom projection line generated from the unloading boundary, the dewatering well projection lines of the dewatering well group inside and outside the pit, and spatial projection positioning. In this embodiment, the system determines the construction condition number and projection profile position to be processed based on the construction condition safety factor profile cloud map, and calls the three-dimensional pit bottom anti-heave safety factor distribution field under the same construction condition number through the backtracking relationship saved in the construction condition safety factor profile cloud map. Thus, the critical isosurface of the safety factor is extracted from the three-dimensional pit bottom anti-heave safety factor distribution field, and the construction condition safety factor profile cloud map is used to provide projection index and visual positioning, and is not used as two-dimensional data to directly generate a three-dimensional isosurface.

[0170] S701, scan the construction condition safety factor profile cloud map in the potential influence zone of unloading residual pressure inside the curtain toe, interpolate the boundary of the finite element calculation unit with the safety factor value equal to the safety factor critical threshold as a continuous isosurface, and extract to form the safety factor critical isosurface.

[0171] The system scans the safety factor profile cloud map of the construction conditions within the potential influence zone of the unloaded residual pressure inside the curtain wall toe, and reads the distribution field of the pit bottom heave safety factor under the same construction condition number based on the backtracking relationship saved in the construction condition safety factor profile cloud map. Let... This represents the critical threshold of the safety factor, and the preferred critical threshold of the safety factor is... ;set up This represents a continuous function obtained by interpolating the distribution field of the pit bottom heave safety factor. Let the critical isosurface of the safety factor be represented, then:

[0172]

[0173] In a unified mesh, if the safety factor distribution field values ​​of the pit bottom heave resistance of adjacent finite element calculation units are located on both sides of the critical threshold of the safety factor, the system performs three-dimensional linear interpolation on the boundaries of adjacent finite element calculation units to obtain the position where the safety factor value equals the critical threshold of the safety factor. If the safety factor distribution field value of the pit bottom heave resistance of a certain finite element calculation unit is equal to the critical threshold of the safety factor, then the boundary of that finite element calculation unit is considered as part of the critical isosurface of the safety factor. The boundary of the critical isosurface of the safety factor is formed by the intersection of the critical isosurface of the safety factor with the projected profile or the pit bottom plane.

[0174] S702, scan the spatial distribution field of the unloading residual pressure influence coefficient, extract the largest connected region with a volume not less than three adjacent finite element calculation units, and generate the corresponding core line of the largest dangerous through area;

[0175] The system scans the spatial distribution field of the unloading residual pressure influence coefficient, identifies finite element calculation elements whose spatial distribution field of the unloading residual pressure influence coefficient has a value greater than zero, and forms several connected regions using a three-dimensional six-connectivity determination rule. The three-dimensional six-connectivity determination rule states that two finite element calculation elements are considered connected only if they have coplanar contact; otherwise, they are not considered connected if they only have edge contact or node contact. Let... Indicates the first A connected region, This indicates the number of finite element units contained in the connected region. Only connected regions that satisfy the following formula are included in the extraction of the core line of the maximum dangerous penetration zone:

[0176]

[0177] During connected region identification, the system uses a region growing algorithm to group finite element calculation units that meet the three-dimensional six-connectivity judgment rule into the same connected region. Only connected regions containing three or more finite element calculation units participate in the subsequent screening of the maximum dangerous connected area in the spatial distribution field of unloading residual pressure influence coefficient. Connected regions with fewer than three finite element calculation units are ignored as local isolated points and are not included in the extraction range of the core line of the maximum dangerous connected area.

[0178] The system extracts the maximum dangerous penetrating zone of the spatial distribution field of the unloading residual pressure influence coefficient in a connected region with a volume not less than three adjacent finite element calculation units. Let... This represents the area of ​​maximum danger in the spatial distribution field of the unloading residual pressure influence coefficient. Indicates the first The cumulative value of the volume of each finite element calculation element in a connected region is then:

[0179]

[0180] The system calculates the geometric centroid of the maximum dangerous penetration zone in the spatial distribution field of the unloading residual pressure influence coefficient according to vertical elevation layers, and connects the geometric centroids of each layer in elevation order to generate the core line of the maximum dangerous penetration zone. The layer thickness is consistent with the vertical element layer thickness of the unified mesh, and each finite element calculation element corresponds to one calculation layer; the elevation range of the layer starts from the elevation of the unloading boundary and extends downward to the bottom elevation of the potential influence zone of unloading residual pressure inside the curtain toe, i.e., the top surface of the underlying confined aquifer. Let... This indicates the maximum dangerous penetration zone in the spatial distribution field of the unloading residual pressure influence coefficient at elevation. The set of finite element computational elements within a horizontally layered structure. Indicates the first The volume of a finite element calculation unit Let the geometric centroid of this elevation layer be represented, then:

[0181]

[0182] when When empty, the system skips the elevation layer and does not generate its geometric centroid; when there is a gap between two adjacent valid elevation layers, the system only connects the geometric centroids corresponding to the adjacent valid elevation layers. The core line of the maximum danger penetration zone is used to represent the skeleton of the risk path that satisfies the connectivity condition and has the largest spatial range in the spatial distribution field of the unloading residual pressure influence coefficient.

[0183] S703 superimposes the boundary of the critical isosurface of the safety factor, the core line of the maximum danger penetration zone, the wall toe projection line generated by the wall toe elevation, the pit bottom projection line generated by the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit onto the same coordinate layer and arranges them according to the construction condition sequence.

[0184] The system establishes a common coordinate layer. The system projects the boundary of the critical isosurface of the safety factor onto the same coordinate layer, projects the core line of the maximum danger penetration zone onto the same coordinate layer, projects the wall toe projection line generated by the wall toe elevation onto the same coordinate layer, projects the pit bottom projection line generated by the unloading boundary onto the same coordinate layer, and projects the dewatering well projection lines of the dewatering well group inside and outside the pit onto the same coordinate layer.

[0185] For each construction condition number, the system generates a corresponding coordinate layer and arranges the coordinate layers corresponding to each construction condition number according to the construction condition time sequence. By arranging them according to the construction condition time sequence, the system can display the relative position evolution between the boundary of the critical isosurface of the safety factor, the core line of the maximum danger penetration zone, the wall toe projection line generated by the wall toe elevation, the pit bottom projection line generated by the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit.

[0186] S704, in which the planar projection scale of the coordinate layer is consistent with the unified coordinate system, and the vertical profile of the projection penetrates the inner side of the diaphragm wall, the bottom elevation of the waterstop, the unloading boundary and the top surface of the underlying confined aquifer.

[0187] The system sets the planar projection scale of the coordinate layer to be consistent with the unified coordinate system. This indicates the mapping ratio from the horizontal coordinates of the unified coordinate system to the horizontal coordinates of the coordinate layer. To represent the mapping ratio from the vertical coordinates of the unified coordinate system to the vertical coordinates of the coordinate layer, then:

[0188]

[0189] and This is determined by the projection settings of the coordinate layer. The system sets the vertical profile of the projection to penetrate the inner side of the diaphragm wall, the bottom elevation of the waterstop, the unloading boundary, and the top surface of the underlying confined aquifer. Through this setting, Figure 4 The projection lines of the wall toe generated from the wall toe elevation, the projection lines of the pit bottom generated from the unloading boundary, and the projection lines of the dewatering wells of the dewatering well group inside and outside the pit can all be compared with those of the wall toe elevation generated from the wall toe elevation, the projection lines of the pit bottom generated from the unloading boundary, and the projection lines of the dewatering wells of the dewatering well group inside and outside the pit. Figure 1 The spatial correspondence between the underground continuous wall, the water-resistant curtain, the unloading boundary, the top surface of the underlying confined aquifer, and the dewatering well group inside and outside the pit is established.

[0190] Example 7:

[0191] The system visualizes and renders the spatial projection positioning results, outputting a stability simulation analysis diagram of the foundation pit excavation. This diagram uses a three-panel layout, including a first panel, a second panel, and a third panel. The first panel displays the spatial topological relationship of the composite structure; the second panel displays the distribution of the safety factor distribution field at the bottom of the pit on the pit bottom plane, superimposed with the boundary of the critical isosurface of the safety factor; and the third panel displays the vertical cross-sectional shape of the spatial distribution field of the unloading residual pressure influence coefficient inside the wall toe, as well as the spatial geometric relationship between the spatial distribution field of the unloading residual pressure influence coefficient and the top surface of the underlying confined aquifer.

[0192] S801 reads the coordinate layers arranged according to the construction condition time sequence, and performs visualization rendering of the digital twin three-dimensional spatial model and the construction condition safety factor profile cloud map in a three-view layout.

[0193] The system reads coordinate layers arranged chronologically according to construction conditions, and also reads the digital twin 3D spatial model, the safety factor profile cloud map of construction conditions, the spatial distribution field of the unloading residual pressure influence coefficient, the distribution field of the pit bottom heave safety factor, the critical isosurface of the safety factor, and the core line of the maximum danger penetration zone. The system creates a three-panel layout in the output canvas and loads the above data into each of the three layouts.

[0194] Each of the three-panel layouts retains the construction condition number, the projection scale of a unified coordinate system, and the corresponding legend. The system generates corresponding foundation pit excavation stability simulation analysis diagrams one by one according to the construction condition number, allowing the foundation pit excavation stability simulation analysis diagrams of different construction condition numbers to be viewed continuously according to the construction condition time sequence.

[0195] S802, Generate the first drawing to show the spatial topological relationship of the composite structure;

[0196] The system generates the first drawing. The first drawing shows the spatial topology of the composite structure, including at least the underground continuous wall, the wall toe embedded section, the water-tight curtain, the dewatering well group inside and outside the pit, the soft soil pit bottom and the underlying confined aquifer, and, as needed, the soft soil layer, the weakly permeable layer, the internal support, the column piles, the retaining and water-stopping surface, the hydraulic boundary, the stratum, the unloading boundary and the structural constraint surface.

[0197] The spatial representation of the first image and Figure 1 The composite structure of the foundation pit in the soft soil layer shown corresponds to the potential impact zone of the unloading residual pressure. Figure 1 The relative positions of the underground continuous wall, the wall toe embedded section, the water-tight curtain, the dewatering well group inside and outside the pit, the bottom of the soft soil pit, and the underlying confined aquifer are expressed in the first drawing by the rendering results of the digital twin three-dimensional spatial model.

[0198] S803, generate the second map, use continuous color bands to show the distribution of the safety factor distribution field of the pit bottom heave on the pit bottom plane, and superimpose the boundary of the critical isosurface of the safety factor;

[0199] The system generates a second map. This second map uses the pit bottom plane as its display plane, reads the pit bottom heave resistance safety factor distribution field at that location, and converts this distribution field into displayed values ​​using continuous color bands. The closer the pit bottom heave resistance safety factor distribution field value is to the critical safety factor threshold, the more prominent the corresponding area is in the second map; the higher the value of the pit bottom heave resistance safety factor distribution field, the more relatively stable the corresponding area appears in the second map.

[0200] The system overlays the boundary of the critical isosurface of the safety factor onto the second map. The boundary of the critical isosurface and the distribution of the pit bottom heave resistance safety factor distribution field on the pit bottom plane are displayed together, allowing the observer to directly identify locations where the pit bottom heave resistance safety factor distribution field values ​​approach the critical threshold. The calculation logic of the second map is consistent with... Figure 3 and Figure 4 Correspondingly.

[0201] S804 generates the third image, showing the vertical cross-sectional shape of the spatial distribution field of the unloading residual pressure influence coefficient on the inner side of the wall toe, as well as the spatial geometric relationship between the spatial distribution field of the unloading residual pressure influence coefficient and the top surface of the underlying confined aquifer.

[0202] The system generates a third map. The third map uses a vertical cross-section penetrating the inner side of the diaphragm wall, the bottom elevation of the waterstop, the unloading boundary, and the top surface of the underlying confined aquifer as the display plane. The spatial distribution field of the unloading residual pressure influence coefficient is read on this vertical cross-section, and the spatial distribution field of the unloading residual pressure influence coefficient is converted into the map display value according to the continuous color band.

[0203] The system overlays the top surface of the underlying confined aquifer, the toe projection line generated from the toe elevation, the pit bottom projection line generated from the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit onto the third view. The third view is used to illustrate the spatial distribution field of the unloading residual pressure influence coefficient and its spatial geometric relationship with the top surface of the underlying confined aquifer, and to... Figure 2 and Figure 1 The spatial location of the potential impact zone of unloading residual pressure on the inner side of the middle curtain toe corresponds to this.

[0204] S805 combines the first, second, and third drawings into an image file and outputs it as a simulation analysis diagram of the foundation pit excavation stability.

[0205] The system combines the first, second, and third drawings into an image file, outputting a stability simulation analysis diagram of the foundation pit excavation. During the synthesis process, the system maintains a unified coordinate system scale for each drawing in the three-drawing layout and writes the construction condition number, pit bottom elevation, condition duration, continuous color band legend, and critical safety factor threshold into the image file.

[0206] In the three-view layout, the heights of the first, second, and third views are consistent, and the coordinate axes of the second and third views are aligned vertically. The viewing direction of the first view is tilted along the long side of the foundation pit's planar boundary. The second view uses an orthographic projection perpendicular to the bottom plane of the pit, and the third view uses an orthographic projection perpendicular to the inner vertical section of the wall toe. When synthesizing image files, the system maintains the consistent positions of the continuous color band legend, construction condition number, and unified coordinate system identifier across the three views, enabling cross-referencing among the views in the foundation pit excavation stability simulation analysis diagram.

[0207] After the output is completed, the system retains the index relationship between the finite element simulation result layer, the construction condition safety factor profile cloud map, the same coordinate layer and the foundation pit excavation stability simulation analysis diagram, so that the first, second and third maps of the foundation pit excavation stability simulation analysis diagram can all be traced back to the finite element calculation unit and the integrated construction hydraulic condition data package in the digital twin three-dimensional space model.

[0208] It should be noted that if water level records and pore water pressure records are missing, the system will not supplement them across construction condition numbers; the system will prioritize interpolation using water level records and pore water pressure records with adjacent timestamps within the same construction condition number. If there are insufficient water level records and pore water pressure records within the same construction condition number, the system will retain the read pit bottom elevation, condition duration, dewatering well pumping status, diaphragm wall displacement, and support axial force, and will stop the automatic calculation of the residual coefficient of excess pore pressure under that construction condition number, waiting for the water level records and pore water pressure records to be supplemented before executing S502 to S507.

[0209] It should be noted that if the effective stress release coefficient, residual excess pore pressure coefficient, consolidation time effect reduction coefficient, spatial distribution field of unloading residual pressure influence coefficient, pit bottom heave driving stress, pit bottom passive heave resistance, or pit bottom heave safety factor distribution field show non-numerical results, the system will return to the corresponding finite element calculation unit and reread the initial vertical effective stress before excavation, the current construction condition vertical effective stress, the current construction condition actual pore water pressure, the target pore water pressure of the same construction condition, the soft soil consolidation coefficient, the drainage path length, the current construction condition duration, the soft clay foundation bearing capacity coefficient, the current construction condition undrained shear strength field, and the wall-soil interface shear resistance.

[0210] It should be noted that if the boundary of the critical isosurface of the safety factor in the second drawing is inconsistent with the backtracking relationship of the distribution field of the anti-uplift safety factor at the bottom of the pit, the system will re-execute S701; if the spatial distribution field of the unloading residual pressure influence coefficient in the third drawing is inconsistent with the construction condition number, the system will re-execute S504 and S804; if the wall toe projection line generated by the wall toe elevation, the pit bottom projection line generated by the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit are not superimposed on the same coordinate layer, the system will re-execute S703; if the planar projection scale of the coordinate layer is inconsistent with the unified coordinate system, the system will re-execute S704.

[0211] The embodiments of this example have been described above. However, this example is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms based on the guidance of this example, and all of them are within the protection scope of this example.

Claims

1. A simulation and analysis system for the stability of foundation pit excavation in soft soil strata, applied to simulation operations including diaphragm walls, wall toe anchorages, impermeable curtains, dewatering well groups inside and outside the pit, the bottom of the soft soil pit, and the underlying confined aquifer, characterized in that, Configured for execution: A digital twin 3D spatial model containing a composite structure is established in a unified coordinate system, and a unified mesh is generated to produce finite element calculation units. The data on earthwork excavation, support formation, dewatering operation, and monitoring sampling are uniformly coded to form an integrated hydraulic construction condition data package. Within the digital twin three-dimensional spatial model, construct the potential impact zone of unloading residual pressure located inside the curtain toe of the underground continuous wall or water-resistant curtain. Within the potential influence zone of unloading residual pressure inside the curtain toe, the spatial distribution field of the unloading residual pressure influence coefficient is solved element by element using finite element calculations. Based on the spatial distribution field of the unloading residual pressure influence coefficient, the distribution field of the pit bottom heave safety factor is calculated, including: Combined with the stress calculation tolerance, the effective stress release coefficient is calculated based on the change in the initial effective vertical stress before excavation and the effective vertical stress under the current construction conditions; Combined with the pore pressure calculation tolerance, the residual coefficient of excess pore pressure is calculated based on the deviation between the actual pore water pressure under the current construction conditions and the target pore water pressure under the same conditions. Based on the consolidation coefficient of soft soil, the length of the drainage path, and the duration of the current construction conditions, calculate the reduction factor of the consolidation time effect that reflects the lag in the dissipation of pore water pressure. By coupling the effective stress release coefficient, the residual coefficient of excess pore pressure, and the consolidation time effect reduction coefficient, a spatial distribution field of the unloading residual pressure influence coefficient is constructed. The stress release effect of the spatial distribution field of the combined excavation depth load, residual pore water pressure, and unloading residual pressure influence coefficient is used to determine the driving stress of pit bottom heave. Based on the bearing capacity coefficient of soft clay foundation, the undrained shear strength field under the current construction conditions and the shear resistance of the wall-soil interface, the passive resistance to heave at the bottom of the pit is determined. Based on the passive resistance to heave at the bottom of the pit, the driving stress of heave at the bottom of the pit, and the calculation tolerance of the safety factor, the distribution field of the safety factor for heave resistance at the bottom of the pit is calculated and obtained. The spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom anti-heave safety factor are written into the finite element simulation result layer. The staged stability simulation of each construction condition containing the unloading residual pressure field is performed on a unified grid to form a construction condition safety factor profile cloud map. Based on the safety factor profile cloud map of the construction working condition, the core line of the maximum dangerous penetration area of ​​the spatial distribution field of the critical isosurface of the safety factor and the influence coefficient of the unloading residual pressure is extracted and spatially projected and located. The spatial projection positioning results are visualized and rendered to output a stability simulation analysis diagram of the foundation pit excavation.

2. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 1, characterized in that, A digital twin 3D spatial model containing a composite structure is established in a unified coordinate system, and a unified mesh is generated to produce finite element computational elements, including: Read the plane boundary of the foundation pit, the axis and thickness of the diaphragm wall, the wall toe elevation, the thickness of the waterproof curtain and the bottom elevation of the water-stopping surface, and generate the soil retaining and water-stopping surface; Read the coordinates of the dewatering well group inside and outside the pit, the start and end elevations of the dewatering well filter pipes, and the pumping period to generate the hydraulic boundary; Read the stratigraphic interface of the soft soil layer, the weakly permeable layer and the underlying confined aquifer where the soft soil pit bottom is located to form a stratigraphic body; Read the coordinates of the internal support and column piles and set them as the structural constraint surface, and set the excavation surface at the bottom of the pit as the unloading boundary that moves with the construction conditions; The retaining surface, hydraulic boundary, stratum, unloading boundary, and structural constraint surface are integrated to form a digital twin three-dimensional spatial model.

3. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 2, characterized in that, The data from earthwork excavation, support formation, dewatering operations, and monitoring sampling are uniformly coded to form an integrated construction hydraulic condition data package, including: Generate construction condition numbers based on the construction log; For each construction condition number, read the pit bottom elevation, condition duration, dewatering well pumping status, diaphragm wall displacement, support axial force, water level record, and pore water pressure record. Data from multiple sources read within the same construction condition number is bound to the corresponding digital twin 3D spatial model according to timestamps; After the construction phase corresponding to the construction condition number is completed, a condition data package is formed. The starting point for the analysis of the condition data package is set to the unloading boundary stabilization record time of the previous construction condition, and the ending point for the analysis is set to the time when the pit bottom elevation corresponding to this condition is completed and the internal support reaches the record activation state.

4. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 3, characterized in that, Within the digital twin 3D spatial model, a potential impact zone of unloaded residual pressure is constructed on the inner side of the curtain toe, located inside the underground continuous wall or waterproof curtain, including: Scan the inner side of the underground continuous wall segment by segment to extract the wall toe elevation and the bottom elevation of the water-stop curtain; A vertical section intersecting the unloading boundary is generated on the inner side of each section, and the horizontal extension distance into the pit is determined according to the excavation depth under the current working conditions. Finite element calculation elements that meet the geological properties of soft soil or weakly permeable layer and are located above the boundary of the underlying confined aquifer are marked as the potential influence zone of unloading residual pressure inside the curtain toe. For each finite element calculation unit within the potential influence zone of unloading residual pressure inside the curtain toe, record the spatial geometric relationship between the finite element calculation unit and the position of the wall toe elevation, the unloading boundary, and the starting and ending elevations of the dewatering well filter pipe.

5. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 4, characterized in that, The spatial distribution field of the unloading residual pressure influence coefficient and the distribution field of the pit bottom heave safety factor are written into the finite element simulation result layer. Staged stability simulations of each construction condition, including the unloading residual pressure field, are performed on a unified mesh to generate a safety factor profile cloud map of the construction condition, including: According to the time sequence of the data packets for each working condition, the low permeability boundary conditions of the unloading boundary, hydraulic boundary and retaining water-stop surface are applied sequentially to the current construction working condition. The coupled field of stress and seepage is solved on a unified grid, and numerical coupled simulations of the unloading and heave at the bottom of the pit, the passive zone pressure at the toe of the wall, and the uplift effect of the confined water are performed. After the solution is completed, the distribution data of the safety factor distribution field of the pit bottom heave resistance are extracted from the inner side of the diaphragm wall, the center position of the unloading boundary, the depth of the internal support, and the position of the top surface of the underlying confined aquifer. The distributed data is spatially projected along the inner side of the diaphragm wall and the unloading boundary to form a construction condition safety factor profile cloud map corresponding to the current construction condition.

6. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 5, characterized in that, Based on the safety factor profile cloud map of the construction conditions, the core line of the maximum dangerous penetration area of ​​the spatial distribution field of the critical isosurface of the safety factor and the influence field of the unloading residual pressure coefficient is extracted, and spatial projection positioning is performed, including: Scan the construction condition safety factor profile cloud map in the potential influence zone of unloading residual pressure inside the curtain toe, and interpolate the boundary of the finite element calculation unit with the safety factor value equal to the safety factor critical threshold as a continuous isosurface, and extract it to form the safety factor critical isosurface. Scan the spatial distribution field of the unloading residual pressure influence coefficient, extract the largest connected region with a volume not less than three adjacent finite element calculation units, and generate the corresponding core line of the largest dangerous through zone; The boundary of the critical isosurface of the safety factor, the core line of the maximum danger penetration zone, the wall toe projection line generated by the wall toe elevation, the pit bottom projection line generated by the unloading boundary, and the dewatering well projection lines of the dewatering well group inside and outside the pit are superimposed on the same coordinate layer and arranged according to the construction condition sequence. The planar projection scale of the coordinate layer is consistent with the unified coordinate system, and the vertical profile of the projection penetrates the inner side of the diaphragm wall, the bottom elevation of the waterstop, the unloading boundary, and the top surface of the underlying confined aquifer.

7. A stability simulation and analysis system for foundation pit excavation in soft soil strata according to claim 6, characterized in that, The spatial projection positioning results are visualized and rendered to output a stability simulation analysis diagram of the foundation pit excavation, including: Read the coordinate layers arranged according to the construction conditions and render the digital twin 3D spatial model and the construction condition safety factor profile cloud map in a three-view layout. Generate the first drawing to show the spatial topological relationships of the composite structure; A second map is generated, which uses continuous color bands to show the distribution of the safety factor distribution field at the bottom of the pit on the bottom plane, and superimposes the boundary of the critical isosurface of the safety factor. A third image is generated, showing the vertical cross-sectional shape of the spatial distribution field of the unloading residual pressure influence coefficient on the inner side of the wall toe, as well as the spatial geometric relationship between the spatial distribution field of the unloading residual pressure influence coefficient and the top surface of the underlying confined aquifer. The first, second, and third images are combined into an image file, which is then output as a simulation analysis diagram of the foundation pit excavation stability.

Images