Foundation pit water inflow prediction and dewatering decision method based on hydrogeological parameter fusion

Abstract

The present application relates to the technical field of foundation pit water inflow prediction, in particular to a method for predicting foundation pit water inflow and making dewatering and drainage decisions based on hydrogeological parameter fusion, comprising the following steps: source-constrained water level-flow response of stable pumping and drainage section and pump stopping and recovery section, fusion of aquifer conduction characteristics, riverbed hydraulic connection characteristics, flow characteristics around the lower end of the suspended water stop curtain, and conduction characteristics of pit drainage facilities into recharge-permeation parameter field; calculation of different curtain penetration depths and drainage facility combinations to obtain stage source water inflow envelope, determination of stage dewatering and drainage decision sequence according to target control water level, allowable hydraulic gradient and available pumping capacity, and update of recharge-permeation parameter field according to source deviation, and then regeneration of stage source water inflow envelope and stage dewatering and drainage decision sequence. The present application avoids the traditional scheme of only increasing the total pumping capacity to control the water level, which intensifies the hydraulic gradient at the curtain outlet or the risk of local pipe heave.

Description

Technical Field

[0001] This invention relates to the field of foundation pit water inflow prediction technology, and in particular to a foundation pit water inflow prediction and dewatering decision-making method based on the fusion of hydrogeological parameters. Background Technology

[0002] When the excavation pit is excavated below the groundwater level, dewatering measures are needed to lower the water level in the pit to ensure the base is dry, the slope is stable, and to prevent seepage damage such as piping, quicksand, and sudden surges. For large semi-open excavation pits near rivers, especially those located in deep gravel layers, the aquifer has high permeability and obvious spatial heterogeneity. The hydraulic connection between the river and groundwater is close, and groundwater can enter the pit along the unclosed boundary, the lower end of the suspended cutoff curtain, and the highly permeable layer at the bottom of the pit, forming a complex seepage state with the combined effects of riverbed overflow, curtain flow, and lateral-bottom recharge of the aquifer.

[0003] Current methods for predicting water inflow typically involve determining the permeability coefficient through pumping tests, followed by calculating the total water inflow from the foundation pit using the large-well method, analytical formulas, or numerical models. However, the scales of pumping tests, injection tests, and regional hydrogeological data differ, resulting in significant parameter variations. Furthermore, relying solely on the drawdown during the steady pumping phase for parameter inversion can lead to issues where aquifer permeability, riverbed recharge capacity, and curtain flow capacity compensate for each other. This means that multiple sets of parameters can fit similar water levels but correspond to different water inflow volumes and seepage sources, impacting the reliability of the prediction.

[0004] Furthermore, existing numerical calculations often assume a fixed geometry for the foundation pit and drainage boundaries, making it difficult to reflect changes in the relative penetration depth of the curtain excavation and the reconstruction of seepage paths caused by phased deployment of drainage facilities. When open ditches and sump pits are treated as fixed-flow wells, calculated drainage volumes may continue to be generated even after the water level falls below the drainage elevation. Existing methods typically only output the total inflow of the foundation pit, making it difficult to distinguish between riverbed recharge, flow around the lower end of the curtain, and water from other aquifers, and also failing to identify local confluence locations and seepage stability risks. Adjustments to dewatering during construction often rely on empirical judgments based on total flow or single-point water levels, lacking the technical means to update hydrogeological parameters based on measured source deviations and to continuously correct subsequent decisions. Summary of the Invention

[0005] This invention provides a method for predicting the inflow of water into foundation pits and making decisions on dewatering based on the fusion of hydrogeological parameters.

[0006] The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters includes the following steps: S1: Within the same pumping disturbance cycle, the water level-flow response of the stable pumping section and the pump stop recovery section are constrained by different sources. The aquifer conduction characteristics, riverbed hydraulic connection characteristics, flow characteristics around the lower end of the suspended water-stop curtain, and conduction characteristics of the in-pit discharge facilities are integrated into a replenishment-seepage barrier parameter field. S2: Input the replenishment-seepage barrier parameter field into the transient seepage model that changes synchronously with the foundation pit excavation stage, set the open ditch and sump as threshold-type discharge boundaries that open and close as the water level exceeds the discharge elevation, calculate for different curtain penetration depths and discharge facility combinations, and obtain the stage-specific water inflow envelope. The stage-specific water inflow envelope is used to characterize the total water inflow, water source, spatial inflow location and seepage stability state of each excavation stage. S3: Using the phased source inflow envelope as input, determine the phased dewatering decision sequence based on the target control water level, allowable hydraulic gradient, and available pumping capacity. When executing the phased dewatering decision sequence, update the recharge-infiltration parameter field based on the source deviation between the measured water level-flow response and the phased source inflow envelope, and then regenerate the phased source inflow envelope and the phased dewatering decision sequence.

[0007] Optionally, S1 includes obtaining the quasi-steady-state drawdown and corresponding inflow of the observation wells in the foundation pit under different drainage flows in the stable drainage section, constructing a mixed water level-flow relationship that reflects the combined effect of horizontal conduction of the aquifer and flow around the lower end of the curtain, and using the equivalent permeability coefficient of the aquifer and the equivalent resistance coefficient of the flow around the curtain as parameters to be identified, and using least squares fitting to form the first constraint.

[0008] Optionally, S1 includes a pump shutdown recovery section where the recovery curve of the water level rising over time after pump shutdown is obtained. The recovery process is divided into an early rapid recovery section dominated by the hydraulic connection of the riverbed and a later slow stabilization section dominated by the curtain flow and the receding of the far-field aquifer. Based on the recovery rate and the recovery amplitude, the riverbed overflow supply coefficient and the curtain flow residual influence coefficient are identified to form a second constraint.

[0009] Optionally, S1 further includes combining the flow capacity coefficients of the open ditch and sump pit calibrated by field tests or design parameters, assigning the equivalent permeability coefficient of the aquifer, the equivalent resistance coefficient of the curtain flow, the riverbed overflow recharge coefficient, and the discharge facility flow capacity coefficient to the corresponding grid or partition of the transient seepage model according to their respective spatial ranges, and generating the recharge-seepage barrier parameter field that simultaneously reflects the differences in recharge sources and the spatial heterogeneity of the seepage barrier structure through interpolation or partition assignment.

[0010] Optionally, according to the excavation process of the foundation pit, S2 activates or deactivates the grid cells of the corresponding excavation area in the transient seepage model in stages, and synchronously updates the properties of the seepage medium given by the supply-barrier parameter field, forming a model domain that changes synchronously with the geometric and hydraulic characteristics of the excavation stage.

[0011] Optionally, both the open ditch and the sump are set as third-type mixed boundaries, and a threshold judgment is applied to their flow-head relationship: when the water head at the boundary node is lower than the discharge elevation, the discharge flow is zero, and the boundary automatically degenerates into a zero-flux boundary; when the water head at the boundary node exceeds the discharge elevation, the boundary activates flow discharge according to the discharge facility's flow capacity coefficient, and the discharge flow increases with the increase of the water head, forming the threshold-type discharge boundary.

[0012] Optionally, in the model domain, transient seepage calculations are performed on various working condition combinations defined by the curtain penetration depth, drainage facility layout density, and elevation, under the same pumping disturbance cycle. From the calculation results, the total amount of water entering the open ditch and sump in each excavation stage, the lateral-bottom inflow from the lower end of the curtain and the aquifer below it into the pit, and the amount of water that enters the model domain via riverbed recharge and finally flows into the pit are extracted. The seepage stability state at the curtain bypass outlet and the excavation face is evaluated according to the corresponding velocity head gradient. The above information is integrated into the stage-specific inflow envelope, which is indexed by the excavation stage and covers the total inflow, the water volume from different sources, the spatial distribution of the inflow location, and the seepage stability safety factor.

[0013] Optionally, S3 obtains the expected total water catchment in the pit, lateral-bottom flow inflow, riverbed overflow replenishment inflow, spatial distribution of inflow locations, and seepage stability safety factor from the inflow envelope corresponding to the current excavation stage; using the target control water level as a constraint, it back-calculates the lower limit of the total pumping flow rate to meet the water level requirements; combining the allowable hydraulic gradient and the seepage stability safety factor, it determines the upper limit of the pumping intensity at each inflow location to prevent seepage damage; within the available pumping capacity, and under the condition of simultaneously meeting the lower limit of the total pumping flow rate and the upper limit of the pumping intensity at each location, it generates the stage dewatering decision sequence consisting of the start-stop combination and flow allocation of open ditches, sump pits, and backup pumping facilities.

[0014] Optionally, when the staged dewatering decision sequence is executed, the measured water level of the observation well in the foundation pit and the measured flow rate of the discharge facility are collected simultaneously to obtain the measured water level-flow response; the measured water level-flow response is compared with the predicted time history of the source water volume in the staged source inflow envelope, and the source identification method based on water balance and response curve decomposition is used to calculate the source deviation from each recharge source, namely aquifer conduction, riverbed overflow and curtain flow.

[0015] Optionally, S3 further includes using the source deviation as a driving force, employing a parameter inversion algorithm to correct the aquifer equivalent permeability coefficient, riverbed overflow supply coefficient, and curtain flow equivalent resistance coefficient in the supply-barrier parameter field, to obtain an updated supply-barrier parameter field; re-inputting the updated supply-barrier parameter field into the transient seepage model, calculating the stage source inflow envelope for subsequent excavation stages, and using this to regenerate the stage dewatering decision sequence, forming a rolling closed-loop adaptive dewatering decision.

[0016] The beneficial effects of this invention are: This invention, by jointly utilizing the water level-flow response of the stable pumping section and the pump-stop recovery section within the same pumping disturbance cycle, constrains the horizontal conduction of the aquifer, the riverbed overflow recharge, the flow around the lower end of the suspended cutoff curtain, and the conduction characteristics of the in-pit discharge facilities, respectively, and forms a recharge-impermeability parameter field according to the actual spatial range of each parameter. Compared with existing methods that only use the stable pumping water level to invert a single permeability coefficient, this invention can use the fast recovery component and the slow recovery component to distinguish the residual influence of continuous riverbed recharge and curtain flow, reducing parameter compensation between the aquifer equivalent permeability coefficient, the riverbed overflow recharge coefficient, and the curtain flow equivalent resistance coefficient, and avoiding the non-uniqueness problem that multiple sets of parameters can fit the same water level but yield different inflow rates.

[0017] This invention updates the transient seepage model stage by stage as the foundation pit excavation progresses. By blunting the already excavated grid, activating newly exposed excavation faces, inheriting the termination head of the previous stage, and synchronously adjusting the curtain termination elevation, it can express the seepage path reconstruction caused by the descent of the excavation face, changes in the relative penetration depth of the curtain, and the stratified deployment of drainage facilities. In particular, by setting open ditches and sump pits as threshold-type discharge boundaries that automatically open and close as the node head exceeds the discharge elevation, it can avoid the false drawdown and false inflow caused by the fixed flow well model continuing to discharge after the water level is below the bottom of the ditch or the discharge elevation of the sump. This invention further adopts a dual-label source identification method that combines water source labels and inflow path labels. It can identify both the cross-flow replenishment water from the riverbed and the lateral-bottom inflow water entering the foundation pit through the lower end of the curtain and the aquifer below, and avoid duplicate statistics when the riverbed replenishment water enters the foundation pit through the lower end of the curtain. The resulting phased inflow envelope is no longer limited to providing a single total inflow volume, but can simultaneously reflect the time history of the inflow volume, the spatial location of the inflow, the local hydraulic gradient, and the seepage stability safety factor, providing a quantitative basis for determining the reasonable penetration depth of the curtain, the density of the discharge facilities, and the location of the risk of local seepage damage.

[0018] This invention takes the phased source inflow envelope as input, and simultaneously calculates the lower limit of the total pumping flow rate to meet the target control water level and the upper limit of the local pumping intensity to meet the seepage stability requirements. Under the constraints of available pumping capacity and backup capacity, it generates a phased dewatering decision sequence for open ditches, sump pits and backup pumping facilities, avoiding the risk of exacerbating the hydraulic gradient at the curtain outlet or local piping by simply increasing the total pumping volume to control the water level, as is the case with traditional schemes. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the execution steps of embodiment S3 of the present invention; Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. For some well-known technologies, those skilled in the art may also use other alternative methods to implement the invention. Moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0022] like Figures 1-2 As shown, the method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters includes the following steps: S1. Within the same pumping disturbance cycle, the water level-flow response of the stable pumping section and the pump stop recovery section are constrained by different sources. The aquifer conduction characteristics, riverbed hydraulic connection characteristics, flow characteristics around the lower end of the suspended cutoff curtain, and conduction characteristics of the in-pit discharge facilities are integrated into a recharge-seepage barrier parameter field.

[0023] S11. Conduct sampling and disturbance tests and generate response data for the same period.

[0024] Under the condition that the excavation form of the foundation pit, the state of the suspended cutoff wall, the river water level boundary, and the location of the discharge facilities remain unchanged, a complete pumping disturbance cycle is implemented. The pumping disturbance cycle includes no less than three stable pumping sections and one pump shutdown and recovery section.

[0025] The target drainage flow rates for the three stable drainage stages are preferably set at 40%, 70%, and 100% of the design drainage capacity, respectively. After each change in drainage flow rate, the corresponding drainage conditions are maintained until the water level in the observation wells within the foundation pit reaches a quasi-steady state. Drainage is then stopped, and the pump stop recovery stage begins, during which the water level is continuously recorded until the rate of water level recovery within the continuous recording period approaches the resolution capability of the observation instrument.

[0026] Observation wells should be located at least on the side facing the river, inside the suspended cutoff curtain, at the center of the foundation pit, and on the side away from the river, to ensure that different locations have different response sensitivities to riverbed recharge, flow around the lower end of the curtain, and horizontal conduction of the aquifer.

[0027] No. In the first stable extraction phase The quasi-steady-state drawdown of each observation well is: ; in, For the first In the first stable extraction phase Quasi-steady-state water level drawdown of each observation well; Before the start of the drainage disturbance The initial water level of each observation well; For the first In the first stable extraction phase Quasi-steady-state water level of one observation well; To ensure stable sampling and sorting segment numbering; Number the observation well.

[0028] The quasi-steady-state determination condition is: ; and: ; in, For the first The observation well in the first Water level at each sampling time; For the first Each sampling time; The water level stability threshold is set to three times the ratio of the water level sensor measurement uncertainty to the sampling interval. To determine the standard deviation of the pumping flow rate within the time period; This is the average value of the pumping flow rate within the specified time period; The larger of three times the relative measurement uncertainty of the flow meter and 3% is taken as the flow stability threshold.

[0029] The judgment period shall not be less than six consecutive sampling intervals, and shall not be less than 60 minutes. Using three times the measurement uncertainty as the threshold can eliminate random instrument errors; setting a 3% lower limit for flow stability avoids misjudging normal pump pulsation as changes in pumping conditions.

[0030] S12. Construct the mixed water level-flow relationship and form the first constraint.

[0031] Based on the geometry of the foundation pit, the location of the observation wells, the thickness of the aquifer, and the location of the suspended water-stop curtain, the horizontal conduction unit response of the aquifer and the flow around the lower end of the curtain are established respectively.

[0032] The unit response of the aquifer horizontal conduction is obtained by keeping the actual foundation pit boundary and the location of the observation well unchanged, applying the unit pumping flow rate to the location of the discharge facility, and calculating the unit water level response of each observation well without applying additional resistance to the curtain.

[0033] The unit response of the flow around the lower end of the curtain is obtained by the following method: keeping the aquifer foundation conduction capacity unchanged, applying a unit hydraulic resistance at the lower end of the suspended water-stop curtain, and calculating the additional water level response of each observation well caused by the unit hydraulic resistance.

[0034] No. In the first stable extraction phase The predicted drawdown of each observation well is expressed as follows: ; in, This corresponds to the predicted drawdown. For the first The measured total inflow of water in each stable pumping section; For the first The unit response coefficient of the horizontal conduction of the aquifer corresponding to each observation well is obtained by calculating the unit response of the horizontal conduction of the aquifer. The equivalent permeability coefficient of the aquifer to be identified; For the first The unit response coefficient of the flow around the lower end of the curtain corresponding to each observation well is obtained by calculating the unit response of the flow around the lower end of the curtain. The equivalent drag coefficient of the curtain flow to be identified.

[0035] The equivalent permeability coefficient of the aquifer and the equivalent drag coefficient of the curtain flow were identified by least squares fitting: ; in, The equivalent permeability coefficient of the aquifer obtained through the first constraint identification; The equivalent drag coefficient of the curtain flow obtained by the first constraint identification; For the first The combined measurement uncertainty of the drawdown of each observation well is obtained by taking the square root of the sum of the squares of the initial water level measurement uncertainty and the quasi-steady-state water level measurement uncertainty.

[0036] The residuals are normalized using measurement uncertainty, which gives high-precision observation wells a stronger constraint effect. This weight is directly determined by the instrument calibration results and is not manually set.

[0037] To ensure that the two parameters to be identified can be distinguished from each other, the unit response coefficient sequence of the aquifer horizontal conduction corresponding to the observation well must not be proportional to the unit response coefficient sequence of the flow around the lower end of the curtain. If the two are approximately proportional, observation wells should be added on both sides of the curtain or near the end of the curtain, and the pumping disturbance test should be carried out again.

[0038] S13. Construct a pump shutdown recovery model and form a second constraint.

[0039] The time of pump shutdown is recorded as the start time of the recovery process; the first... The remaining water level drawdown of each observation well after pump shutdown is: ; in, Time elapsed after pump shutdown Time The remaining drawdown of the observation well; Time elapsed after pump shutdown Time Measured water levels in each observation well; The recovery time is calculated from the moment the pump stops.

[0040] The remaining drawdown is fitted as a fast recovery component and a slow recovery component: ; in, This is the fitted value for the remaining drawdown. To quickly recover the initial amplitude of the component; To quickly recover the decay rate of the component; To slowly recover the initial amplitude of the component; The decay rate of the slowly recoverable component; It is a natural constant.

[0041] The following constraints are applied during parameter identification: ; By using the constrained nonlinear least squares method, the sum of squared errors between the measured residual water level drawdown and the fitted value at each sampling time is minimized.

[0042] The moment when the fast recovery component equals the slow recovery component is defined as the boundary moment of the recovery phase. ; in, For the first The boundary moment of the recovery phase for each observation well; It is the natural logarithm function.

[0043] exist At that time, the recovery process was determined to be a rapid uplift phase dominated by hydraulic connection replenishment of the riverbed; At that time, the recovery process was determined to be a slow stabilization phase dominated by the flow around the lower end of the curtain and the decline of far-field aquifer recharge.

[0044] The riverbed overflow replenishment coefficient is determined based on the rapid recovery component: ; in, For the first The riverbed overflow replenishment coefficient corresponding to each observation well; The specific yield of the unconfined aquifer is determined through on-site pumping tests, water level recovery tests, or indoor tests at the same stratum. For the first The effective water level response area of ​​each observation well is determined according to the area of ​​the Thiessen polygon formed by the perpendicular bisectors of adjacent observation wells.

[0045] The residual influence coefficient of the curtain flow is determined based on the proportion of the time integral formed by the two recovery components throughout the recovery period: ; in, For the first The residual influence coefficient of the curtain flow corresponding to each observation well ranges from 0 to 1.

[0046] The aforementioned time integral percentage utilizes both the recovery amplitude and the recovery rate. The larger this coefficient, the more pronounced the slow recovery memory caused by the flow around the lower end of the curtain and the far-field supply after pump shutdown.

[0047] When the rapid recovery component of the observation well on the riverside is not higher than that of the observation well on the side away from the river, or when the correlation between the rapid recovery component and the river level difference does not reach the 95% statistical level, the rapid recovery component should not be directly attributed to the riverbed replenishment. Instead, the recovery observation time should be extended or the observation wells on the riverside should be supplemented and re-identified.

[0048] S14. Use the second constraint to correct the spatial distribution of the equivalent drag around the curtain.

[0049] The first constraint yields the overall magnitude of the equivalent drag coefficient of the curtain flow, while the second constraint yields the degree of residual influence of the curtain flow at different locations.

[0050] First, calculate the area-weighted average of the residual influence coefficients of the curtain flow: ; in, This is the area-weighted average of the residual influence coefficients of the curtain flow.

[0051] Subsequently, the local equivalent drag coefficient of the curtain flow around each curtain zone was determined: ; in, In order to be with the first The equivalent drag coefficient of the local curtain flow around the affected area of ​​each observation well.

[0052] The more pronounced the slow recovery of memory, the smaller the equivalent drag of the local curtain flow, indicating that the region is more likely to form a continuous flow around it; conversely, the weaker the slow recovery of memory, the greater the equivalent drag of the local curtain flow. This correction simultaneously keeps the overall drag magnitude under the control of the first constraint, avoiding overall drag parameter drift caused solely by the recovery curve.

[0053] S15, Calibrate the flow capacity coefficient of the drainage facilities in the pit.

[0054] Staged water storage-drainage tests were conducted on both open ditches and sump pits, and the water level elevations within the drainage facilities and the corresponding actual drainage volumes were recorded. The flow rate relationship of the drainage facilities is expressed as follows: ; in, For the first The measured drainage volume of the drainage facility under standard operating conditions; The flow capacity coefficient of the discharge facility to be calibrated; For the first Water level elevation within the discharge facility under specified operating conditions; This refers to the elevation of the bottom of the open ditch or the control elevation for the start-up and drainage of the sump pit. Assign operating condition numbers to the drainage facilities; This is a function that takes the larger of the value inside the parentheses and zero.

[0055] Only calibration conditions where the water level is at least three times the water level measurement uncertainty above the discharge elevation are selected to avoid the influence of measurement noise when the discharge elevation is close to the start-up elevation.

[0056] The flow capacity coefficient of the drainage facility was determined by least squares fitting through the origin: ; in, The flow capacity coefficient of the drainage facility is obtained through on-site calibration.

[0057] For open ditches and sump pits with different structural dimensions, filter media conditions, or pump types, they should be calibrated separately and should not share the same flow capacity coefficient.

[0058] S16, Generation and replenishment—Insulation parameter field.

[0059] The identified and calibrated parameters are assigned to the transient seepage model according to the physical objects involved, forming a recharge-barrier parameter field: ; in, For position The replenishment-impermeability parameter field at the location; Spatial location coordinates; These are components of the aquifer conduction parameters; These are the components of the hydraulic connection parameters of the riverbed; The components of the flow parameters around the lower end of the suspended water-stop curtain; The transmission parameters of the drainage facilities in the pit.

[0060] For aquifer grids with multiple drainage test zones, inverse distance squared interpolation is used: ; ;

[0061] in, These are the aquifer conduction parameters or riverbed hydraulic connection parameters to be interpolated. For the first Parameter identification results for each test area; The number of test areas participating in the interpolation; For the first Each test area is located Interpolation weights; For position To the The distance between the centers of each test zone; For distance smoothing, take half of the minimum distance between adjacent test areas to avoid infinite amplification of a single test value when the distance is close to zero.

[0062] Parameter assignment follows these rules: 1. The equivalent permeability coefficient of the aquifer shall be assigned to the corresponding aquifer grid, and interpolation shall not be performed across the identified weakly permeable interlayers;

[0063] 2. The riverbed overflow replenishment coefficient is only assigned to the riverbed and the boundary grid directly hydraulically connected to the river channel; 3. The equivalent resistance coefficient of the local curtain flow is assigned to the flow grid at the lower end of the suspended water-stop curtain and the end of the curtain; 4. The flow capacity coefficient of the drainage facilities is only assigned to the drainage boundary grid corresponding to open ditches and sump pits; 5. Parameter components that do not belong to the corresponding physical action area are set to zero, the riverbed recharge parameters are not diffused into the aquifer interior, and the curtain flow parameters are not assigned to the boundary where no curtain is set.

[0064] S17. Perform independent verification of the recharge-barrier parameter field.

[0065] One flow condition that was not involved in parameter identification is retained from the stable pumping section. The supply-barrier parameter field is input into the transient seepage model to calculate the water level of each observation well and the total inflow of the foundation pit under this condition.

[0066] The water level verification error is expressed as: ; in, This represents the normalized root mean square error of water level. The total number of observation wells participating in the verification; Calculate the water level for the model; To verify the measured water level under operating conditions; To verify the measured water level drawdown under operating conditions.

[0067] The total inflow verification error is expressed as: ; in, This represents the relative error of the total inflow. Calculate the total inflow for the model; This represents the total water inflow measured on-site.

[0068] when and At that time, it was confirmed that the replenishment-infiltration parameter field met the requirements for the subsequent stage of source inflow envelope calculation; a 10% water level error limit was used to control the water level drawdown prediction deviation, and a 15% inflow error limit was determined based on the requirements of setting a reserve margin for the flow fluctuation of large riverside foundation pits and the pumping capacity of the project.

[0069] When any error exceeds the corresponding limit, the parameter partitions are re-divided according to the spatial location of the largest observation residual: when the residual on the riverside is the largest, the riverbed hydraulic connection partition is subdivided; when the residual near the curtain is the largest, the flow around the lower end of the curtain partition is subdivided; when the residual in the pit is the largest, the flow capacity coefficient of the discharge facility is recalibrated, and then steps S12 to S17 are executed again.

[0070] Traditional methods typically only utilize the drawdown during the steady pumping phase to invert the permeability coefficient. This leads to parameter compensation between riverbed recharge, aquifer conduction, and curtain flow, meaning multiple sets of parameters can yield similar water levels but predict significantly different inflow rates. This invention uses the steady pumping phase to constrain the overall relationship between aquifer conduction and curtain flow. Then, it uses the rapid and slow recovery components in the pump shutdown recovery phase to constrain the hydraulic connectivity of the riverbed and the residual effects of curtain flow, respectively. Simultaneously, it independently calibrates the actual flow capacity of open channels and sump pits. The resulting recharge-impermeability parameter field spatially distinguishes recharge boundaries, impermeable structures, and discharge facilities, reducing non-unique solutions caused by parameter compensation. It also provides a directly usable parameter basis for inflow source identification, spatial inflow location recognition, and threshold-type discharge boundary calculation in step S2.

[0071] S2. Input the replenishment-impermeability parameter field into the transient seepage model that changes synchronously with the foundation pit excavation stage. Set the open ditch and sump as threshold-type discharge boundaries that open and close as the water level exceeds the discharge elevation. Calculate the different curtain penetration depths and discharge facility combinations to obtain the stage-specific inflow envelopes that characterize the total inflow, inflow source, spatial inflow location, and seepage stability state of each excavation stage.

[0072] S21. Construct a transient seepage model that changes synchronously with the foundation pit excavation stage.

[0073] A three-dimensional model domain is established based on the aquifer bottom boundary, riverbed boundary, excavation area of ​​the foundation pit, location of the suspended cutoff curtain, and location of the drainage facilities revealed by the survey. The model covers the area beyond the influence of the foundation pit dewatering in the horizontal direction and the weakly permeable layer below the main seepage channel in the vertical direction. When a stable weakly permeable layer is not revealed, the bottom boundary of the model is set at a position not less than twice the design drawdown depth below the maximum excavation depth, and the boundary sensitivity is verified by expanding the model depth.

[0074] The model domain was discretized using a mesh. Locally finer meshes were used near the excavation face of the foundation pit, the lower end of the suspended cutoff wall, the riverbed connecting zone, open ditches, and sump pits; the remaining areas used progressively larger meshes. The local mesh size was no larger than one-fifth of the distance between adjacent drainage facilities and no larger than one-fifth of the difference in penetration depth between adjacent candidate cutoff walls.

[0075] The transient seepage model uses the following governing equations: ; in, Gradient and divergence operators; The permeability coefficient tensor, which varies with spatial location and excavation stage, is obtained by converting the aquifer conduction parameter components in the recharge-impermeability parameter field. Groundwater head; The unit volume source and sink terms formed by riverbed replenishment, curtain flow around the flow, and discharge boundaries; For aquifer storage parameters, the conversion value between specific yield and calculated layer thickness is used for unconfined aquifers, and the specific storage coefficient is used for confined aquifers. For calculating time.

[0076] When the field test only obtains the equivalent permeability coefficient of the aquifer but not the directional parameters, the vertical permeability coefficient is set to one-tenth of the horizontal permeability coefficient, and sensitivity calculations are performed using one-twentieth and one-fifth of these values, respectively. When the difference in total inflow corresponding to the three values ​​exceeds 10%, vertical hydraulic connection tests are conducted at observation wells at different depths, and the vertical permeability coefficient is re-determined. The 10% value is lower than the allowable error for inflow verification in step S1, and is used to avoid the uncertainty of the vertical parameters dominating the final prediction result.

[0077] The model parameters are obtained from the pumping test, pump shutdown and recovery test and discharge facility calibration results in step S1, and are verified through the independent operating conditions in step S1.

[0078] S22. Update the model domain and mesh status according to the excavation progress.

[0079] The foundation pit construction process is divided into... Each excavation stage corresponds to an actual excavation bottom elevation, the status of the constructed curtain wall, and the status of the drainage facilities already in operation.

[0080] No. The first excavation stage The state function of each grid cell is: ; in, For the grid cell state function; Numbering for each excavation stage; Number the grid cells; For the first The center coordinates of each grid cell; As of the date The space area that has been excavated in the excavation stage; a value of 0 indicates that the grid cell is passivated, and a value of 1 indicates that the grid cell is retained for seepage calculation.

[0081] Grid cells within the excavated area are deactivated and no longer participate in groundwater storage or inter-grid water exchange; grid cells located below the current excavation bottom or outside the pit slope remain active. As the excavation bottom descends, the newly exposed excavation face grid is set as an active boundary capable of receiving seepage flows.

[0082] The properties of the permeable medium for activating the mesh are represented as follows: ; in, For the first The first excavation stage The permeability coefficient tensor of each grid cell; The basic permeability coefficient tensor is assigned to the grid cell to supply the seepage barrier parameter field.

[0083] Initial conditions are determined by inheriting the head state between adjacent excavation stages: ; in, For the first At the start of the first excavation phase The initial head of each activated grid cell; This marks the start time of the excavation phase. This marks the end of the previous excavation phase.

[0084] For grids that have been removed in the previous excavation stage, head transfer will no longer be performed; for grids newly included in the calculation due to changes in construction zones, the distance-weighted head of adjacent unpassivated grids will be used as the initial head, and the static water level of the river corresponding to the grid will be used as the upper limit to avoid interpolation producing unrealistic high heads.

[0085] S23. Set the riverbed recharge boundary and the curtain flow around the boundary.

[0086] The hydraulic connection region of the riverbed is set as a type III mixed recharge boundary, and the inflow into the model domain is: ; in, For the first The replenishment flow into the model domain at each riverbed boundary node; Number the boundary nodes; These are the spatial coordinates of the boundary node; This represents the river level corresponding to the boundary node. This represents the groundwater head at this boundary node.

[0087] The river water level is determined by on-site measurements. For design prediction, the normal water level, the construction-controlled high water level, and the design-verification high water level are input separately. When the river water level is lower than the groundwater head, groundwater discharge into the river within the model domain is permitted to maintain the direction of water exchange at the riverbed boundary, which can change with the head difference.

[0088] The main body of the suspended cutoff wall is designed with a low-permeability interface. The cross-interface flow rate at the lower and upper ends of the wall is calculated based on the equivalent resistance coefficient of the local flow around the wall in the recharge-impermeability parameter field. ; in, For the first The flow rate from the outside of the curtain to the pit side at each curtain-around flow interface node; The water head is on the outside of the curtain; The water head is inside the curtain.

[0089] As the depth of the curtain penetration changes, the termination elevation of the low-permeability interface also changes synchronously. The grid below the lower end of the curtain restores the basic permeability properties of the aquifer, thereby allowing groundwater to flow around the lower end of the curtain, instead of incorrectly treating the suspended cutoff curtain as a completely closed boundary.

[0090] S24. Construct threshold-type discharge boundaries for open ditches and sump pits.

[0091] Set the grid nodes corresponding to open ditches and sump pits as the third type of mixed discharge boundary.

[0092] No. The discharge flow rate of each discharge boundary node is: ; in, For the first Discharge flow at each discharge boundary node; This refers to the elevation of the bottom of the open ditch or the starting elevation of the sump pit corresponding to this node.

[0093] In the nonlinear iteration at each time step, a set of activated nodes for the discharge boundary is established based on the current water head: ; in, For the first The set of nodes activated at the discharge boundary in the next iteration; This represents the number of iterations within the current time step. This represents the head of the boundary node at the corresponding iteration number.

[0094] For nodes belonging to the set of active nodes of the discharge boundary, the discharge facility flow capacity coefficient is written into the boundary conduction term of the system matrix; for nodes not belonging to the set of active nodes of the discharge boundary, the discharge flow rate is set to zero, degenerating them into zero-flux boundaries. The set of active nodes of the discharge boundary is regenerated after each head solution is completed, until the set of active nodes in two adjacent iterations is completely consistent.

[0095] The following head convergence conditions are also adopted: ; in, The threshold for convergence of the head iteration is the larger of 0.001m and half the resolution of the water level sensor.

[0096] A resolution of 0.001m is used to limit numerical iteration errors, and half the resolution of the water level sensor is used to avoid unnecessary calculations due to the numerical solution accuracy being much higher than the accuracy of the field parameter identification. The current time step is considered convergent only when the set of active nodes at the discharge boundary no longer changes and the above head convergence conditions are met.

[0097] This threshold-type discharge boundary does not generate discharge flow when the water head has not exceeded the discharge elevation, which can prevent the false drawdown caused by the traditional fixed flow well model continuing to pump water after the water level has been lower than the bottom of the ditch or the start-up elevation of the sump.

[0098] S25. Perform grid and time step convergence verification.

[0099] The transient seepage model is discretized using the finite volume method or the central node finite difference method.

[0100] No. Each grid cell satisfies the following between two adjacent time layers: ; in, For the first Water storage parameters of each grid cell; This is the volume of the grid cell; Assign time layer numbers; For the first One time step; In order to be with the first The set of adjacent grid cells; This represents the net source and sink flow rate acting on this grid cell at the current time level. For the first The grid cell and the first The hydraulic conductivity coefficient between grid cells is not measured directly on-site, but is calculated face-by-face based on the recharge-impermeability parameter field, grid geometry, and additional resistance between grid cells.

[0101] For adjacent th The first grid cell and the first For each grid cell, first calculate the normal permeability coefficient of each grid cell along the common surface: ; in, and These are the permeability coefficients of two adjacent grids along the normal to their common surface; For the first The grid points to the first The unit normal vector of the common face of each grid; This is a vector transpose identifier; and It is obtained from the aquifer conduction parameter components in the recharge-impermeability parameter field.

[0102] The hydraulic conductivity between the two grids is calculated based on the series hydraulic resistance: ; in, For the first The grid cell and the first Hydraulic conductivity coefficient between grid cells; and These are the normal distances from the centers of the two grids to the common surface, respectively. The effective flow area of ​​the common surface between two grids when they are in a saturated state; Add hydraulic resistance to the common surface.

[0103] The additional hydraulic resistance at the common surface is assigned a value according to the following rules: ; in, The coordinates of the center of the common surface; This indicates that no water exchange occurs between the two grids.

[0104] When no additional resistance is set at the common surface, the above hydraulic conductivity coefficient calculation is equivalent to the distance-weighted harmonic mean of the normal permeability coefficient, which can avoid overestimating the interfacial flow when using an arithmetic mean when high-permeability grids and low-permeability grids are adjacent. When the common surface is located near a suspended cutoff wall, the equivalent resistance of the flow around the wall is written as a series resistance, which allows the same hydraulic conductivity coefficient to simultaneously reflect the formation conduction resistance and the resistance of the flow around the wall.

[0105] For unconfined aquifers, the saturated effective flow area of ​​the common surface is recalculated based on the current head after each nonlinear iteration: ; in, For the first The saturated effective flow area of ​​the common surface in the next iteration; The horizontal width of the common surface; This is the elevation of the bottom of the common surface.

[0106] Therefore, the hydraulic conductivity coefficient is updated synchronously with the drop in groundwater level, grid passivation, and changes in the curtain state. The flow capacity coefficient of the drainage facilities in open ditches and sump pits is not included in the hydraulic conductivity coefficient, but is written into the system matrix as an independent conduction term of the threshold-type drainage boundary, avoiding the duplication of calculation between the formation conduction capacity and the drainage facility capacity. The initial time step is the measured sampling interval of the stable pumping section. Calculations are performed using the original grid, the locally halved grid, and the time step halving scheme, respectively. When the relative difference in total inflow before and after grid refinement is no greater than 2%, the relative difference in the maximum hydraulic gradient at the lower end of the curtain is no greater than 5%, and the relative difference in total inflow before and after halving the time step is no greater than 2%, the discrete scale convergence is confirmed. The 2% convergence threshold for total inflow is lower than the flow stability threshold in step S1 and the error of the on-site flow measurement, so that the numerical discrete error will not become the main source of error. The 5% convergence threshold for hydraulic gradient is used to limit the influence of local grids on the judgment of seepage stability. If any condition is not met, continue to densify the grid in the corresponding area or reduce the time step; each time step should also meet the requirement that the water balance error is no greater than 0.5%, and the value of 0.5% is lower than the allowable error for the prediction of the inflow volume in the field, in order to confirm that the difference in water volume from different sources comes from changes in operating conditions rather than numerical water loss.

[0107] S26, Combined working conditions of curtain penetration depth and drainage facilities.

[0108] Based on the capabilities of the construction equipment, determine the minimum and maximum penetration depths for curtain wall construction, and generate candidate curtain wall penetration depths between these two values. ; in, For the first Each candidate's curtain penetrates into depth; The penetration depth is required to meet the minimum seepage stability requirements of the cofferdam foundation; Number the candidate depths; The candidate depth interval is the smaller of 5m and 10% of the effective aquifer thickness. 5m corresponds to the commonly used curtain wall construction segmentation and engineering comparison scale; 10% of the effective aquifer thickness is used to prevent the depth interval from being too large when the aquifer is thin, thus missing the inflection point of the seepage barrier effect. If the last value of the candidate sequence is insufficient for the maximum penetration depth, the maximum penetration depth is used as an additional candidate value.

[0109] The density of drainage facilities is determined by four levels of candidate spacing based on the initial design spacing: ; in, For the first Candidate spacing for graded drainage facilities; The initial design spacing is determined based on the preliminary predicted inflow and the calibration capacity of individual discharge facilities; This is the spacing adjustment factor; Number the candidate spacing level.

[0110] Four spacing adjustment coefficients correspond to high-density, relatively high-density, design density, and low-density layouts, respectively, covering a variation range of up to 50% above and below the initial design spacing without excessively increasing the number of working conditions. The discharge elevation for each excavation stage is set as three candidate elevations: 0.5m, 1.0m, and 1.5m below the current excavation bottom. 0.5m corresponds to the minimum control requirement for dry site construction, while 1.0m and 1.5m are used to evaluate the impact of increased drawdown on water inflow and seepage stability. Candidate values ​​are deleted if they are lower than the allowable installation elevation of the discharge equipment.

[0111] The candidate curtain penetration depth, candidate drainage facility spacing, candidate drainage elevation, and drainage facility type are combined using Cartesian methods to form a set of working conditions. For the same working condition, transient calculations are performed at each excavation stage using the same duration, river water level process, and facility start-up and shutdown sequence as the on-site drainage disturbance cycle, ensuring that the results of different working conditions can be directly compared.

[0112] S27. Extract the water flow rate and perform dual-label source identification.

[0113] To avoid double counting of riverbed recharge water entering the foundation pit through the lower end of the curtain and being included in both the riverbed recharge volume and the curtain flow rate, both source and flow path labels are set for the water entering the pit.

[0114] Water source labels are categorized into riverbed recharge water and non-riverbed recharge water; inflow path labels are categorized into paths from the lower end of the curtain and the aquifer below, and paths from other excavation faces. This forms the first... The first excavation stage, the first Dual-label source matrix under combined operating conditions: ; in, This is a dual-label source matrix; Number the combined operating conditions; This refers to the volume of water originating from the riverbed and flowing into the pit via the lower end of the curtain and the aquifer below; This refers to the volume of water originating from the riverbed and flowing into the pit via other excavation faces; This refers to the volume of water originating from sources other than the riverbed and flowing into the pit via the lower end of the curtain and the aquifer below it; This refers to the volume of water originating from sources other than the riverbed and flowing into the pit via other excavation faces; subscript Indicates riverbed water source label, subscript This indicates a non-riverbed water source label; the subscript 'c' indicates the path label for the aquifer below and at the lower end of the curtain. This indicates the path label for other excavation faces.

[0115] Water source labels for each grid cell are transferred using a conservation-based water volume labeling method. Water entering the model domain from the riverbed boundary is assigned a riverbed water source label, while water from the initial aquifer, far-field boundary recharge, and other groundwater recharge is assigned a non-riverbed water source label. When water is exchanged between grids, the labels are transferred according to the proportion of the two types of water sources in the upstream grid.

[0116] The total amount of water collected in the pit is: ; in, The total amount of water collected in the open ditch and sump pit; For water source tag indexing; For import path label index.

[0117] The volume of water that flows across the riverbed and eventually into the pit is: ; in, This is to replenish the riverbed that eventually flows into the pit.

[0118] The lateral-bottom inflow rate from the lower end of the curtain and the aquifer below into the pit is: ; in, This refers to the lateral-bottom inflow of water into the pit via the path from the lower end of the curtain and the aquifer below.

[0119] By using dual-label source separation, the riverbed replenishment attributes and the curtain flow path attributes can be retained simultaneously, while each part of the water volume is only accumulated once when calculating the total inflow.

[0120] S28. Determine the location of spatial inflow and evaluate the stability of the infiltration.

[0121] The lower end of the curtain wall, the upper end of the curtain wall, the bottom surface of the foundation pit, and the slope of the foundation pit are divided into multiple flux statistical elements. For each element, the normal flow rate, normal hydraulic gradient, and corresponding water source label ratio in the direction of entry into the foundation pit are recorded to form a spatial distribution of the inflow location.

[0122] No. The normal hydraulic gradient of each surface element is: ; in, For the first Normal hydraulic gradient of each surface element; Numbering of flux statistics elements; This represents the head gradient at this surface element; This is the unit normal vector pointing into the pit.

[0123] The critical hydraulic gradient of the soil is: ; in, For the first The critical hydraulic gradient of the soil corresponding to each surface element; This represents the specific gravity of the soil particles at that surface element. The void ratio of the soil at this surface element is obtained through in-situ sampling or indoor tests at the same stratum.

[0124] The permeability stability safety factor is: ; in, For the first The permeability stability safety factor of each surface element.

[0125] when When the corresponding surface element is identified as a location of seepage stability risk, the safety factor threshold is set to 1.5 to reserve a safety margin for the uneven particle size distribution, local dominant channels, and detailed hydraulic gradients that cannot be fully expressed by the grid scale in the deep gravel layer. When the applicable engineering specifications require a higher safety factor, the specification value is used instead of 1.5.

[0126] For the curtain flow outlet, the safety factor should be calculated point by point along the lower end of the curtain towards the first grid layer in the pit; for the excavation face, the safety factor should be calculated along the bottom of the pit and all exposed surfaces of the slope, and the regional average gradient should not be used to replace the local maximum gradient.

[0127] S29, Generation stage source inrush envelope.

[0128] For each excavation stage, the total inflow volume, dual-label source matrix, spatial inflow location distribution, and seepage stability safety factor of all combined working conditions and all calculation times are collected to form a stage-specific source inflow envelope: ; in, For the first The phase-specific water inflow envelope of each excavation stage; The spatial distribution of the input location corresponding to the working condition and calculation time; For the first A set of combined working conditions for each excavation stage; This marks the end of the excavation phase. The minimum permeability stability safety factor is defined among all flux statistical elements. The determination of the minimum permeability stability safety factor includes:

[0129] At each excavation stage, for each combination of working conditions, and at each calculation time, the normal hydraulic gradient is calculated for all flux statistical surface elements at the lower end of the curtain flow outlet, the curtain end, the bottom of the foundation pit, and the slope of the foundation pit.

[0130] For flux statistics elements located between two active grids, the normal hydraulic gradient is: ; in, For the first The first excavation stage, the first The combined operating conditions at calculation time t are... Normal hydraulic gradient of each surface element; and These are the calculated water heads for the outer and inner sides of the element, respectively. Calculate the distance between the locations of the two water heads along the normal direction of the surface element.

[0131] For flux statistics elements located on the excavation face, the difference between the internal active grid head and the discharge head at the excavation face is used for calculation: ; in, For the internal active grid water head adjacent to the excavation face; The discharge head corresponding to the excavation face is taken when there is no water accumulation, and the measured water level is taken when local water accumulation occurs. This is the normal distance from the center of the internal active grid to the excavation face.

[0132] No. Calculation of the permeability stability safety factor for each surface element: ; in, For the first The seepage stability safety factor of each surface element under the corresponding excavation stage, combined working conditions and calculation time; For the first The critical hydraulic gradient of each surface element is calculated according to the soil particle specific gravity and void ratio described in S28.

[0133] When multiple sets of geotechnical test results are obtained for the same surface element, the 5% quantile of the critical hydraulic gradient of each set is used; when the number of test sets is less than five, the minimum test value is used to reduce the overestimation of the safety factor caused by local loose areas and uneven gradation of the gravel layer.

[0134] The minimum permeability stability safety factor at the current calculation time is: ; in, For the first The set of flux statistics for each excavation stage covers the flow outlet at the lower end of the curtain, the curtain end, the bottom of the pit, and the slope of the pit.

[0135] The minimum seepage stability safety factor during the excavation phase is: ; in: For the first The first excavation stage, the first The minimum permeability stability safety factor for each combination of operating conditions throughout the entire phase.

[0136] During the calculation, the element number, spatial coordinates, occurrence time, normal hydraulic gradient, and source water volume of the minimum value are recorded simultaneously. Therefore, the minimum seepage stability safety factor in the stage source inflow envelope is not the regional average value, but the most unfavorable value among all risk locations and all calculation times, which can directly determine the specific seepage failure risk location at the curtain bypass outlet or excavation face.

[0137] For any inflow index in the phased source inflow envelope, its upper and lower boundaries are as follows: ; in, For the first The first excavation stage The lower boundary of the inrush index; To correspond to the upper boundary; This is a category identifier for the total amount of water collected in the pit, the amount of water replenished by the riverbed, or the amount of water flowing from the side to the bottom of the curtain.

[0138] The phased water inflow envelope is stored according to the excavation phase, and the curtain penetration depth, drainage facility spacing, drainage elevation, maximum water inflow time, maximum water inflow location and minimum seepage stability safety factor are associated for each combination of working conditions, so that step S3 can directly generate the phased dewatering decision sequence based on the target control water level, allowable hydraulic gradient and available pumping capacity.

[0139] Existing transient seepage calculations typically treat open ditches and sump pits as equivalent to fixed-flow wells, and use a fixed model domain across different excavation stages. This approach leads to forced drainage after the water level falls below the discharge elevation and fails to represent the seepage path reconstruction caused by exposed excavation faces, changes in the relative penetration depth of the curtain, and the layered deployment of discharge facilities. This invention addresses this by using phased passivation of grid cells, synchronous activation of excavation face boundaries, and inheritance of head states to allow the model domain to change with the construction process; it achieves automatic opening and closing of threshold-type discharge boundaries through active set iteration; it solves the problem of repeated statistics when riverbed recharge water enters the foundation pit via the lower end of the curtain by simultaneously identifying the groundwater recharge source and the actual path into the foundation pit through dual-label source identification; and it links the predicted inflow volume with the local seepage stability safety factor, so that the phased source inflow envelope not only reflects the scale of pumping but also indicates the specific risk locations of the curtain bypass outlet and the excavation face.

[0140] S3. Using the phased source inflow envelope as input, determine the phased dewatering decision sequence based on the target control water level, allowable hydraulic gradient, and available pumping capacity. When executing the phased dewatering decision sequence, update the recharge-infiltration parameter field based on the source deviation between the measured water level-flow response and the phased source inflow envelope, and then regenerate the phased source inflow envelope and the phased dewatering decision sequence.

[0141] S31. Extract the predicted status of the current excavation stage.

[0142] Based on the current excavation bottom elevation, the completed curtain penetration depth, the drainage facilities already in operation, and the real-time river water level, the combined working conditions corresponding to the current project status are determined from the phased source inflow envelope.

[0143] When the current curtain penetration depth, drainage facility spacing, or river water level is between two previously calculated conditions, piecewise linear interpolation is performed along the curtain penetration depth, drainage facility spacing, and river water level directions, without crossing conditions with different drainage facility opening / closing states. For adjacent conditions with different drainage facility opening / closing states, the transient seepage model is called again to calculate the current state.

[0144] The predicted state vector for the current excavation stage is represented as: ; in, This is the predicted state vector for the current excavation stage; To estimate the total amount of water flowing into the pit; To predict the lateral-bottom flow rate; To estimate the amount of water flowing over the riverbed to replenish the inflow; The expected spatial inflow location distribution; The minimum expected permeability stability safety factor; superscript This represents the predicted value.

[0145] When multiple operating conditions that match the current engineering status exist, the upper boundary of the inflow rate is used to determine the pumping capacity requirement, and the lower boundary of the seepage stability safety factor is used to determine the local pumping limit, so as to avoid using the average value to cover up unfavorable operating conditions.

[0146] S32. Back-calculate the lower limit of the total pumping flow rate to meet the target control water level.

[0147] Extract the highest water level at the control point of the foundation pit corresponding to different total drainage flows from the phased source inflow envelope, and construct the drainage flow-control water level response function: ; in, For the first Pumping flow rate-control water level response function for each excavation stage; The total candidate pumping flow rate; This is a set of observation points that require water level control during the current excavation phase. The total pumping flow rate is Time Predicted water levels at each control point.

[0148] The pumping flow rate-control water level response function is constructed using monotonically piecewise cubic interpolation. First, the calculation results from the different water inflow sources are arranged in ascending order of pumping flow rate. When local calculation results do not satisfy the physical law that the control water level does not rise with increasing pumping flow rate, they are corrected to a monotonically ordered sequence using an adjacent point merging method. Subsequently, piecewise cubic interpolation is performed between adjacent calculation points. This process avoids unrealistic water level oscillations caused by ordinary high-order interpolation.

[0149] The lower limit of the total pumping flow rate to meet the target control water level is: ; in, For the first Lower limit of total drainage flow rate for each excavation stage; The target control water level for this excavation phase.

[0150] In the specific solution, the minimum drainage flow rate and available drainage capacity in the stage-based source inflow envelope are used as the search interval, and the lower limit of the total drainage flow rate is calculated by using the bisection method. The termination condition for the binary iteration is: ; in, This is the upper bound of the extraction flow for the current search interval; This is the lower bound of the pumping flow for the current search interval; The threshold for terminating the flow rate back-calculation is the larger of 1% of the available pumping capacity and three times the standard measurement uncertainty of the flowmeter. The value of 1% is used to ensure that the back-calculation error is less than the actual adjustment step size of the pumping facility; the three times the standard measurement uncertainty of the flowmeter is used to avoid the back-calculation accuracy exceeding the on-site flow rate identification capability.

[0151] S33. Determine the upper limit of local drainage intensity and generate a phased dewatering decision sequence.

[0152] Based on the hydraulic gradient and seepage stability safety factor at each spatial confluence location within the phased source inflow envelope, determine the first... Allowable hydraulic gradient at each inflow location: ; in, For the first The actual control gradient at each inflow location; The allowable hydraulic gradient as specified in the design documents or applicable standards; To achieve the required permeability stability safety factor, a value of 1.5 is used. If the applicable standard has higher requirements, the standard value shall be adopted.

[0153] For each inflow location, the minimum adjustable flow rate of the discharge facility is increased and decreased near the current reference pumping condition, and the change in hydraulic gradient is calculated using the transient seepage model to obtain the local gradient sensitivity coefficient: ; in, For the first The sensitivity coefficient of the hydraulic gradient at each inflow location to the local pumping intensity; To increase the normal hydraulic gradient after local pumping intensity; To reduce the normal hydraulic gradient after localized pumping intensity; This is to increase the localized drainage intensity; This is to reduce the intensity of localized drainage.

[0154] When the local gradient sensitivity coefficient is greater than zero, the upper limit of the extraction intensity at this merging location is: ; in, For the first The upper limit of the pumping intensity at each inflow point where no seepage damage occurs; This refers to the localized pumping intensity under reference operating conditions. The normal hydraulic gradient is for reference operating conditions.

[0155] When the local gradient sensitivity coefficient When the value is not greater than zero, it indicates that increasing the pumping intensity at that location has not caused an increase in the local hydraulic gradient. Therefore, no additional upper limit determined by the hydraulic gradient is set, and the rated capacity of the drainage facility is used as the upper limit. When the calculated upper limit of the pumping intensity is less than zero, the confluence location is determined to be an area that cannot be dealt with by continuing to increase pumping. In this case, priority is given to curtain reinforcement, reverse filtration protection, or relocation of the drainage facility.

[0156] The construction period is divided into several control periods, and constraints on facility start-up and shutdown and flow allocation are established: ; ; ; in, This represents the total number of dispatchable drainage facilities; Number the waste disposal facilities; Number the control period; For the first The flow rate allocated to each drainage facility during the ℓth control period; This is a variable for facility start-up and shutdown; it is set to 1 when starting and 0 when stopping. For the first The rated pumping capacity of each drainage facility; This refers to the location where the drainage facility enters the space. For backup pumping capacity; This represents the available pumping capacity during this control period.

[0157] The standby pumping capacity is determined and expressed as follows: ; in, This represents the maximum rated pumping capacity of a single unit among currently available drainage facilities.

[0158] A 10% reserve ratio is used to cope with local high permeability channels in the gravel layer and short-term fluctuations in river water levels; at the same time, at least one unit of maximum single-machine capacity is reserved so that the single-machine failure backup requirement can still be met after any operating equipment fails.

[0159] Among the feasible schemes that satisfy the above constraints, a hierarchical optimization approach is adopted to generate a phased dewatering decision sequence: first, minimize the exceedance of the target control water level and the exceedance of the hydraulic gradient; then, minimize the number of facility start-ups and shutdowns in schemes without safety exceedances; and finally, minimize the total pumping energy consumption when the number of start-ups and shutdowns is the same. Hierarchical optimization is used without setting artificial weighting coefficients to avoid altering the priority of safety constraints by selecting weights for indicators with different dimensions.

[0160] The phased dewatering decision sequence is represented as follows: ; in, For the first The decision sequence for dewatering during each excavation stage; This refers to the facility activation time for the corresponding control period; This refers to the facility's shutdown time during the corresponding control period.

[0161] S34. Obtain the measured water level-flow response and calculate the source deviation.

[0162] When executing the phased dewatering decision sequence, the water level of each observation well, the flow rate of the open ditch, the flow rate of the sump, the water level of the river, and the start / stop status of the facilities in the foundation pit are recorded synchronously at the same sampling interval as in step S1, forming a measured water level-flow response.

[0163] First, the unit responses of aquifer conduction, riverbed overflow, and curtain flow to the well water level and discharge facility flow rate were calculated using a transient seepage model, and then arranged according to the same sampling time to form a source response matrix: ; in, The source response matrix; This is the column vector of water level-flow response corresponding to a unit change in the conduction of the aquifer. This is the column vector of water level-discharge response corresponding to a unit change in riverbed flow; This is the column vector of water level-flow response corresponding to a unit change in the flow around the curtain; subscript These represent the aquifer conduction source, the riverbed overflow source, and the curtain flow source, respectively.

[0164] The source response matrix is ​​recalculated based on the current supply-barrier parameter field during each rolling update, without using a preset database or fixed feature library.

[0165] The measured water level changes and measured discharge flow rates were combined into an observation vector according to the sampling time, and the source was identified using the non-negative constrained least squares method. ; in, The response coefficients of the three identified supply sources; This is the observation vector composed of the measured water level and flow response; For the measurement uncertainty matrix; It is a 2-norm.

[0166] The measurement uncertainty matrix is ​​a diagonal matrix, with the water level observation term taking the reciprocal of the standard measurement uncertainty of the corresponding water level sensor, and the flow rate observation term taking the reciprocal of the standard measurement uncertainty of the corresponding flow meter.

[0167] This allows the water level and flow rate residuals to be normalized according to their respective measurement accuracy, without the need for additional manual weighting.

[0168] The measured water volumes of each identified recharge source are as follows: ; in, For the first Identification of different types of recharge sources and measurement of water volume; The corresponding predicted water volume is given for the phased source inflow envelope; For the supply source category index; The identification response coefficients for this recharge source are obtained through non-negative constrained least squares inversion, specifically including: First, based on the current recharge-impermeability parameter field and the actual implemented staged dewatering decision sequence, three unit perturbation calculations are performed using a transient seepage model. The first perturbation only affects the equivalent permeability coefficient of the aquifer to obtain the changes in water level in each observation well and the changes in flow rate of the discharge facilities caused by the aquifer conduction change; the second perturbation only affects the riverbed overflow recharge coefficient to obtain the water level-flow response corresponding to the riverbed recharge change; the third perturbation only affects the equivalent resistance coefficient of the curtain flow to obtain the water level-flow response corresponding to the curtain flow change. The three types of unit responses are arranged according to the same observation location and sampling time to form a sub-source response matrix; second, the water level changes in observation wells, open ditch flow, and sump flow measured synchronously on-site are arranged in the same order as the sub-source response matrix to form a measured response sequence. Water level data was normalized according to the standard measurement uncertainty of the water level sensor, and flow rate data was normalized according to the standard measurement uncertainty of the flow meter, so that data with different dimensions and measurement precisions could participate in the identification. Subsequently, a response coefficient was set for each of the aquifer conduction source, the riverbed overflow source, and the curtain flow source, requiring all three response coefficients to be no less than zero. A non-negative constrained least squares algorithm was used to repeatedly adjust the three response coefficients, minimizing the normalized square error between the calculated water level-flow response and the measured water level-flow response formed by superimposing the corresponding response coefficients for the three types of unit responses. The measured total discharge was also used as a water volume closure constraint during the solution process to prevent the sum of the water volumes corresponding to the three response coefficients from deviating significantly from the measured total discharge. The three coefficients obtained when the error is minimized are the identification response coefficients for each recharge source. A response coefficient greater than 1 indicates that the actual contribution of the recharge source is higher than the predicted contribution in the staged source inflow envelope; a response coefficient less than 1 indicates that the actual contribution is lower than the predicted contribution; and a response coefficient equal to 1 indicates that the actual contribution is consistent with the predicted contribution. Multiplying the identification response coefficient by the predicted water volume of the corresponding recharge source yields the identified measured water volume of that recharge source. After identification, the closure error and spatial distribution of the residuals for each source should be checked. If the closure error is no greater than 5% and the residuals are not continuously concentrated in the same direction in a certain observation area, the identification response coefficient is accepted; otherwise, issues such as missed drainage, rainwater entering pits, surface water mixing, or abnormal monitoring equipment should be checked, and re-identification should be performed after correcting the measured response sequence.

[0169] The source deviations for each supply source are: ; in, For the first Source bias of similar supply sources.

[0170] After source identification is completed, a water flow closure test is performed: ; in, This is the closure error for the water source distribution; The total flow rate of the drainage facility was measured. This represents the standard uncertainty of flow measurement.

[0171] The source identification result is accepted when the source water volume closure error is no greater than 5%. The 5% value is higher than the normal random error of the flow meter but lower than the inflow volume verification error in step S1, and is used to distinguish between measurement fluctuations and obvious source identification mismatches. If it exceeds 5%, check for missed flow measurements in the drainage facilities, rainwater entering the pit, or surface water mixing, and re-identify the source after replenishing the corresponding water volume items.

[0172] S35. Update the supply-barrier parameter field using source deviation.

[0173] The parameters to be updated are converted to logarithmic space to ensure that the updated equivalent permeability coefficient of the aquifer, the riverbed overflow recharge coefficient, and the equivalent drag coefficient of the curtain flow are always positive. ; in, Let be the logarithmic vector of the parameters to be inverted; This is the identifier for vector transpose.

[0174] Increment each parameter in the parameter vector by 1%, recalculate the source water volume and observation well water level using the transient seepage model, and construct the parameter sensitivity matrix: ; in, For the first The predicted response pair for the first Sensitivity to logarithmic parameters; For the first Individual water level response or source flow response; Number the response quantity; This is the parameter number to be updated.

[0175] A 1% disturbance amplitude is higher than the 0.5% water balance error of the transient seepage model, but falls within the range of local linear response. When the response change caused by the disturbance is less than three times the numerical solution error, the disturbance amplitude of this parameter is increased to 2%, and the corresponding sensitivity is recalculated.

[0176] The parameter correction is obtained through regularization inversion and is expressed as: ; in, The optimal parameter correction vector; It is a residual vector composed of water level residual and source deviation; For the parameter sensitivity matrix; This is the residual normalization matrix, and its values ​​are determined in the same way as the measurement uncertainty matrix; The regularization coefficient is used. It is a spatial smoothing matrix, with adjacent partitions of the same type of parameters subject to difference constraints, and no smoothing constraints are set between different physical boundaries.

[0177] The magnitude of a single update is limited to 0.67 to 1.5 times the original parameter to prevent sudden parameter changes caused by accidental measurement biases during the sampling and perturbation period. The regularization coefficient is determined using a bias principle: starting from zero and increasing incrementally, the smallest regularization coefficient is selected that ensures the normalized residual does not exceed the expected value corresponding to the degrees of freedom of the observed data for the first time, avoiding the need for manually assigning fixed weights.

[0178] The updated parameter vector is represented as follows: ; in, This is the updated actual parameter vector; This is the actual parameter vector before the update; This is an element-wise multiplication operation; It is an element-wise exponential function.

[0179] The aquifer conduction source bias is used to update the zone containing the aquifer's equivalent permeability coefficient; the riverbed overflow source bias is used to update the riverbed hydraulic connection boundary; and the curtain flow around source bias is used to update the flow around the lower and upper ends of the suspended cutoff curtain. Different recharge sources do not cross-update their main physical parameters to reduce non-unique solutions caused by parameter compensation. If the updated model reduces the normalized residual and the prediction errors for water level and flow rate in the next monitoring period are within three times the measurement uncertainty of the corresponding instrument, the update is accepted, and the updated recharge-impermeability parameter field is obtained; otherwise, the parameter update magnitude is reduced by half, and the model is inverted again.

[0180] S36. Regenerate the prediction results and implement rolling closed-loop decision-making.

[0181] The updated supply-barrier parameter field is re-input into the transient seepage model, keeping the completed excavation stage, curtain construction status, and drainage facility status unchanged, and the stage-specific inflow envelopes for the remaining time period of the current excavation stage and subsequent excavation stages are recalculated.

[0182] Following steps S31 to S33, the lower limit of the total drainage flow, the upper limit of the drainage intensity at each inflow location, and the reserve drainage capacity are recalculated to generate a new phased dewatering decision sequence. Control periods that have already been executed will not be retrospectively modified, and the new phased dewatering decision sequence will take effect from the next control period.

[0183] An early rolling update is triggered when any of the following conditions are met: the source deviation exceeds three times the standard uncertainty of the source water volume and occurs consecutively for three sampling times; or the expected minimum permeability stability safety factor is less than 1.5; or the difference between the current available pumping capacity and the lower limit of the total pumping flow is less than the standby pumping capacity.

[0184] The source deviation trigger condition is expressed as follows: ; in, For the first The standard uncertainty of the water volume by source is determined by the flow measurement uncertainty and the source identification residual.

[0185] Three times the standard uncertainty eliminates most random measurement fluctuations, and three consecutive sampling times are used to avoid single-point anomalies triggering model updates. If no premature update is triggered, a regular update is performed after each excavation stage.

[0186] This invention uses the phased source inflow envelope as the decision input, simultaneously incorporating the lower limit of the total pumping flow and the upper limit of the local pumping intensity into facility scheduling, thus enabling water level control and seepage stability constraints to work together. Through source response matrices and non-negative constraint source identification methods, measured deviations are attributed to aquifer conduction, riverbed overflow, and curtain flow, respectively. Then, the source deviations are used to directionally update the corresponding parameter zones, reducing mutual compensation between different parameters. The updated prediction results are directly used for facility start-up and shutdown and flow allocation in subsequent stages, achieving adaptive decision-making for dewatering and drainage that is continuously corrected as excavation progresses.

[0187] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0188] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters, characterized in that, Includes the following steps: S1: Within the same pumping disturbance cycle, the water level-flow response of the stable pumping section and the pump stop recovery section are constrained by different sources. The aquifer conduction characteristics, riverbed hydraulic connection characteristics, flow characteristics around the lower end of the suspended water-stop curtain, and conduction characteristics of the in-pit discharge facilities are integrated into a replenishment-seepage barrier parameter field. S2: Input the replenishment-seepage barrier parameter field into the transient seepage model that changes synchronously with the foundation pit excavation stage, set the open ditch and sump as threshold-type discharge boundaries that open and close as the water level exceeds the discharge elevation, calculate for different curtain penetration depths and discharge facility combinations, and obtain the stage-specific water inflow envelope. The stage-specific water inflow envelope is used to characterize the total water inflow, water source, spatial inflow location and seepage stability state of each excavation stage. S3: Using the phased source inflow envelope as input, determine the phased dewatering decision sequence based on the target control water level, allowable hydraulic gradient, and available pumping capacity. When executing the phased dewatering decision sequence, update the recharge-infiltration parameter field based on the source deviation between the measured water level-flow response and the phased source inflow envelope, and then regenerate the phased source inflow envelope and the phased dewatering decision sequence.

2. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters as described in claim 1, characterized in that, S1 includes obtaining the quasi-steady-state drawdown and corresponding inflow of the observation wells in the foundation pit under different drainage flow rates in the stable drainage section, constructing a mixed water level-flow relationship that reflects the combined effect of horizontal conduction of the aquifer and flow around the lower end of the curtain, and using the equivalent permeability coefficient of the aquifer and the equivalent resistance coefficient of the flow around the curtain as parameters to be identified, and using least squares fitting to form the first constraint.

3. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 2, characterized in that, S1 includes a pump shutdown recovery section, in which the recovery curve of the water level rising over time after pump shutdown is obtained, and the recovery process is separated into an early rapid recovery section dominated by the hydraulic connection of the riverbed and a later slow stabilization section dominated by the curtain flow and the receding of the far-field aquifer. Based on the recovery rate and the recovery amplitude, the riverbed overflow supply coefficient and the curtain flow residual influence coefficient are identified to form a second constraint.

4. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 3, characterized in that, The S1 further includes combining the flow capacity coefficients of the open ditch and sump pit calibrated by field tests or design parameters, assigning the equivalent permeability coefficient of the aquifer, the equivalent resistance coefficient of the curtain flow, the riverbed overflow recharge coefficient, and the discharge facility flow capacity coefficient to the corresponding grid or partition of the transient seepage model according to their respective spatial ranges, and generating the recharge-impermeability parameter field that simultaneously reflects the differences in recharge sources and the spatial heterogeneity of the impermeable structure through interpolation or partition assignment.

5. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 1, characterized in that, According to the excavation process of the foundation pit, S2 activates or deactivates the grid cells of the corresponding excavation area in the transient seepage model in stages, and updates the properties of the seepage medium given by the supply-impermeability parameter field in a synchronous manner, forming a model domain that changes synchronously with the geometric and hydraulic characteristics of the excavation stage.

6. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 5, characterized in that, Both the open ditch and the sump are set as the third type of mixed boundary, and a threshold judgment is applied to their flow-head relationship: when the water head at the boundary node is lower than the discharge elevation, the discharge flow is zero, and the boundary automatically degenerates into a zero-flux boundary; when the water head at the boundary node exceeds the discharge elevation, the boundary activates flow discharge according to the discharge facility's flow capacity coefficient, and the discharge flow increases with the increase of the water head, forming the threshold-type discharge boundary.

7. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 6, characterized in that, In the model domain, transient seepage calculations are performed on various working condition combinations defined by the curtain penetration depth, drainage facility layout density, and elevation, under the same pumping disturbance cycle. From the calculation results, the total amount of water entering the open ditch and sump in each excavation stage, the lateral-bottom inflow from the lower end of the curtain and the aquifer below it into the pit, and the amount of water that enters the model domain via riverbed recharge and finally flows into the pit are extracted. The seepage stability state at the curtain bypass outlet and the excavation face is evaluated based on the corresponding velocity head gradient. The above information is integrated into the stage-specific inflow envelope, indexed by the excavation stage and covering the total inflow, the water volume from different sources, the spatial distribution of the inflow location, and the seepage stability safety factor.

8. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 1, characterized in that, S3 obtains the expected total water catchment volume in the pit, the lateral-bottom flow inflow volume, the riverbed overflow replenishment inflow volume, and their spatial distribution at the inflow locations and the seepage stability safety factor from the inflow envelope corresponding to the current excavation stage; using the target control water level as a constraint, it back-calculates the lower limit of the total pumping flow rate that meets the water level requirements; and combines the allowable hydraulic gradient and the seepage stability safety factor to determine the upper limit of the pumping intensity at each inflow location where seepage failure will not occur. Within the range of available pumping capacity, and under the condition of simultaneously satisfying the lower limit of the total pumping flow and the upper limit of the pumping intensity at each location, the phased dewatering decision sequence is generated, consisting of the start-up and shutdown combination and flow allocation of open ditches, sump pits and backup pumping facilities.

9. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 8, characterized in that, When the phased dewatering decision sequence is executed, the measured water level of the observation wells in the foundation pit and the measured flow rate of the discharge facilities are collected simultaneously to obtain the measured water level-flow response. The measured water level-flow response is compared with the predicted water volume time history in the phased source inflow envelope. Using the source identification method based on water balance and response curve decomposition, the source deviations from each recharge source, namely aquifer conduction, riverbed overflow and curtain flow, are calculated.

10. The method for predicting foundation pit water inflow and making dewatering decisions based on the fusion of hydrogeological parameters according to claim 9, characterized in that, S3 further includes using the source deviation as a driving force, employing a parameter inversion algorithm to correct the aquifer equivalent permeability coefficient, riverbed overflow supply coefficient, and curtain flow equivalent resistance coefficient in the supply-barrier parameter field, thereby obtaining an updated supply-barrier parameter field; the updated supply-barrier parameter field is then re-inputted into the transient seepage model to calculate the stage source inflow envelope for subsequent excavation stages, and this is used to regenerate the stage dewatering decision sequence, forming a rolling closed-loop adaptive dewatering decision.

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