Automatic water level control system for combined well arrangement inside and outside of deep foundation pit

Abstract

The present application relates to the field of automation control technology, in particular to a deep foundation pit inner and outer combined well arrangement automatic precipitation water level control system, the system comprises a well arrangement monitoring unit, a control unit and a pump set execution unit, the well arrangement monitoring unit determines the well position in and outside the pit according to the equivalent radius of the pit, the aquifer thickness, the permeability coefficient and the design drawdown, and collects the water level in the well, the control unit compares the water level with the target and the upper limit deviation through PLC, forms start-stop and alarm interlocking instructions, and the pump set execution unit receives the instructions, adjusts the frequency according to the water level change rate and rotates the submersible pump. In the present application, through the inner and outer combined well arrangement and water level feedback, the dewatering and pressure reduction are matched, the start-stop judgment is combined with the deviation threshold and the stable time, the water level oscillation and frequent start-stop are reduced, the pumping intensity changes with the water level change rate, the running time is rotated to share the pump set load, the water level control response and precipitation stability are improved, and the risks of sudden gushing, settlement, idling, energy consumption and fault disposal lag are reduced.

Description

Technical Field

[0001] This invention relates to the field of automation control technology, and in particular to an automated dewatering and water level control system for combined internal and external well placement in deep foundation pits. Background Technology

[0002] The field of automation control technology involves data processing methods that utilize computer equipment to collect, calculate, store, and retrieve field-acquired data, and generate corresponding control commands. Specifically, the water level control for automated dewatering with combined well placement inside and outside deep foundation pits refers to a system where a server receives water level data, pump operation data, and timestamp data uploaded from well points inside and outside the foundation pit, writes the corresponding data into a database, and the control program reads the database records according to a preset sampling period, calculates the water level change value, and then sends the corresponding pumping control command to the field controller.

[0003] With the acceleration of urbanization, the scale of underground space development is constantly expanding, and deep foundation pit projects are increasing. In water-rich areas, especially under geological conditions where the groundwater level is shallow and the aquifer permeability is poor, how to safely, efficiently, and economically control the groundwater level and ensure the safety of dry trench operations and the surrounding environment has become a key aspect of construction technology.

[0004] Existing deep foundation pit dewatering control mainly relies on experience-based well placement combined with manual inspection or decentralized control of single wells. It focuses on single well water level display or local alarms. There is a lack of unified linkage between pit drainage, external pressure reduction, observation well feedback and pump operation. The pump start-up and shutdown and operating frequency are mostly executed according to fixed thresholds or manual commands.

[0005] The main technical problems are as follows: First, the well location layout and pump operation control are separated from each other. It is difficult for the drainage wells inside the pit and the depressurization wells outside the pit to form a coordinated pumping relationship based on the pit size, aquifer conditions and design drawdown, which can easily lead to insufficient drawdown or excessive pumping in some areas. Second, water level monitoring relies on manual patrols or intermittent data collection, which is not real-time. When the groundwater level rises rapidly or the water level in the observation well fluctuates abnormally, on-site response is often delayed, increasing the risk of sudden surges, piping, and subsidence of the surrounding strata.

[0006] Third, the operation of multiple submersible pumps lacks balanced scheduling based on operating status. Some pumps operate at high load for a long time, while others are idle and on standby, resulting in uneven wear of the pump set, increased maintenance pressure in the later stage, and difficulty in timely interlocking and handling after failure. Therefore, existing schemes characterized by experience-based well placement, manual inspection, decentralized start-up and shutdown, and local control are insufficient to meet the requirements of deep foundation pit dewatering projects for stable water level control, coordinated pumping from internal and external wells, balanced equipment operation, and timely risk management. Summary of the Invention

[0007] The purpose of this invention is to provide an automated dewatering water level control system for deep foundation pits, which integrates internal and external well placement. This system enables the internal dewatering wells, external depressurization wells, observation wells, water level monitoring, PLC judgment, pump start / stop, frequency conversion regulation, and alarm interlocking to form a corresponding control relationship. This allows for automated monitoring and control during the dewatering process of deep foundation pits, based on different well locations, target water levels, and operating states.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: an automated dewatering level control system for combined internal and external well placement in deep foundation pits includes: The well monitoring unit determines the well locations based on the equivalent radius of the foundation pit, the thickness of the aquifer, the permeability coefficient, and the design drawdown. It arranges in-pit dewatering wells inside the foundation pit and out-of-pit depressurization wells outside the foundation pit to form a dewatering well group. Submersible water level sensors are arranged in the dewatering well group and the observation wells to collect real-time water level Hc. The control unit, connected to the combined well placement unit, reads the real-time water level Hc via a PLC and compares the real-time water level with the target water level and the upper limit deviation. When the real-time water level is greater than the sum of the target water level and the upper limit deviation, the PLC issues a start command to pump water from the corresponding well. When the real-time water level is not greater than the sum of the target water level and the upper limit deviation, and continues to stabilize for a set time, the PLC issues a stop command and generates an alarm interlock command when an alarm water level, pump failure, or communication interruption is triggered. The pump unit execution unit is connected to the control decision unit. The remote terminal receives the start command, the stop command and the alarm interlock command. It dynamically adjusts the inverter output frequency according to the real-time water level change rate and prioritizes starting the submersible pump with the shortest cumulative running time.

[0009] Specifically, the drainage well inside the pit is used to drain the groundwater within the excavation area, and the pressure-reducing well outside the pit is used to intercept lateral runoff and reduce the water pressure outside the pit.

[0010] Specifically, the well monitoring unit collects the equivalent radius of the foundation pit, the thickness of the aquifer, the permeability coefficient, and the design drawdown to obtain the foundation parameters for well placement; Read the basic parameters of the well layout and distinguish the effective range of the drainage wells inside the pit and the pressure reduction wells outside the pit. Calculate the total water inflow of the pit and the water output of a single well, and determine the theoretical number of wells to form a group of dewatering wells. Submersible water level sensors are installed in the drainage well inside the pit, the pressure reduction well outside the pit, and the observation well. The water level sampled by the submersible water level sensors is converted to a unified elevation benchmark and the real-time water level is output. Among them, the installation depth of the submersible water level sensor should be lower than the target water level of the corresponding well and higher than the sand settling section at the bottom of the well.

[0011] Specifically, the total inflow of the foundation pit and the output of a single well are calculated using the standard incomplete well formula. The theoretical number of wells is calculated according to the formula n=1.1Q / q, where Q represents the total inflow of the foundation pit, q represents the output of a single well, and n represents the theoretical number of wells. The theoretical number of wells is checked by rounding up the safety margin coefficient.

[0012] Specifically, the control unit receives the real-time water level collected by the submersible water level sensor through the PLC, and reads the corresponding target water level, upper limit deviation and stabilization setting time according to the well number of each well in the precipitation well group; When the real-time water level is greater than the sum of the target water level and the upper limit deviation, i.e., Hc > H + ΔH, where Hc represents the real-time water level, H represents the target water level, and ΔH represents the upper limit deviation, the PLC sends a start command to the corresponding well. When the real-time water level is not greater than the sum of the deviations between the target water level and the upper limit, i.e., Hc≤H+ΔH, and continues to reach the set stable time, the PLC sends a shutdown command to the corresponding well.

[0013] Specifically, when the PLC issues a stop command to the corresponding well, it needs to continuously read the real-time water level corresponding to the same well number, and compare the real-time water level with the sum of the target water level and the upper limit deviation after each reading; If any reading satisfies the condition Hc > H + ΔH again, the PLC clears the accumulated stabilization time and restarts the timer; if consecutive readings all satisfy Hc ≤ H + ΔH, and the accumulated time reaches the set stabilization time, the PLC issues the stop command.

[0014] Specifically, the control unit also reads the alarm water level, the pump operation feedback signal and the communication status signal, compares the real-time water level with the alarm water level, and verifies the pump operation feedback signal with the start command or stop command issued by the PLC. When the real-time water level reaches the alarm water level, the pump operation feedback signal is inconsistent with the start or stop command issued by the PLC, or the communication status signal is interrupted, the PLC issues the alarm interlock command.

[0015] Specifically, the control unit stores the target water level, upper limit deviation, alarm water level, and stabilization setting time according to the well numbers of the drainage wells inside the pit, the pressure-reducing wells outside the pit, and the observation wells, and reads the corresponding target water level, upper limit deviation, alarm water level, and stabilization setting time according to the well number when receiving the real-time water level. The PLC only performs a joint judgment on the real-time water level corresponding to the same well number, the corresponding target water level, the upper limit deviation, the alarm water level, and the stable set time.

[0016] Specifically, the pump unit execution unit consists of a remote terminal, a frequency converter, and a submersible pump. The remote terminal receives start commands, stop commands, and alarm interlock commands from the PLC and sends the corresponding commands to the corresponding frequency converter according to the well number of each well in the dewatering well group. When the frequency converter receives a start command, it drives the corresponding submersible pump to run; when it receives a stop command, it stops the corresponding submersible pump from running; and when it receives an alarm interlock command, it stops executing the start-stop regulation of the corresponding submersible pump. The remote terminal continuously reads the real-time water level corresponding to the same well number, and calculates the water level change rate based on the difference between the real-time water levels read before and after and the reading time interval. When the water level change rate is less than the preset descent rate value, the remote terminal increases the output frequency of the strain gauge frequency converter; when the water level change rate is greater than the preset descent rate value and the real-time water level is close to the target water level, the remote terminal decreases the output frequency of the strain gauge frequency converter; the frequency converter drives the corresponding submersible pump to operate according to the adjusted output frequency.

[0017] Specifically, before executing the start command, the pump unit execution unit reads the cumulative running time and operating status of each submersible pump under the same well type, and selects the submersible pump with the shortest cumulative running time from the submersible pumps that are in the startable state as the submersible pump to be started. When the frequency converter corresponding to the submersible pump to be started is in an operational state, the remote terminal will send a start command to the corresponding frequency converter. When the frequency converter corresponding to the submersible pump to be started is in a fault state, the remote terminal excludes the submersible pump to be started and reselects the submersible pump with the shortest cumulative running time from the remaining submersible pumps that are in the startable state.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows: In this invention, well locations are determined based on the equivalent radius of the foundation pit, the thickness of the aquifer, the permeability coefficient, and the designed drawdown depth. This allows for a coordinated pumping relationship between the drainage within the pit and the depressurization outside the pit. Real-time water levels in the dewatering wells and observation wells are continuously acquired. The water levels are then compared with the target water level and deviation threshold. This is combined with measures such as stabilization time to suppress frequent start-stop cycles, triggering pumping when the limit is exceeded, stopping pumping when the target is reached, alarm water levels, pump failures, and communication anomalies, all of which are synchronously interlocked. The pumping intensity is adjusted according to the rate of change of water level. Simultaneously, submersible pumps are rotated evenly according to their cumulative running time, ensuring timely control of water level fluctuations. This reduces the risk of sudden subsidence and idling losses in water-rich urban areas, alleviates energy consumption and maintenance pressure, and makes the construction dewatering process more stable and reliable. Attached Figure Description

[0019] Figure 1 Flowchart of the automated dewatering and water level control system for combined internal and external well placement in deep foundation pits; Figure 2 A schematic diagram for determining the start / stop of water level for the same well number; Figure 3 This is a schematic diagram showing the signal flow of the frequency conversion control unit of the pump set. Figure 4 This is a schematic diagram of alarm interlocking and operational feedback state transitions. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Data from each well is managed by well number, which serves as the binding field for water level data, control parameters, command outputs, pump status, and feedback signals. Submersible water level sensors are installed in the drainage wells inside the pit, the pressure-reducing wells outside the pit, and the observation wells. After the submersible water level sensors output the sampled water level, the well monitoring unit converts it into a real-time water level Hc under a unified elevation benchmark. The target water level H, upper limit deviation ΔH, alarm water level, and stabilization set time are pre-stored in the control unit according to the well number. The PLC reads data from the well with the same well number as the current real-time water level Hc each time.

[0022] Please see Figures 1 to 4 This embodiment provides an automated dewatering water level control system for combined internal and external well placement in deep foundation pits, including a well placement monitoring unit, a control unit, and a pump execution unit.

[0023] The well monitoring unit receives the equivalent radius of the foundation pit, aquifer thickness, permeability coefficient, and design drawdown, generates layout data for the dewatering well group, and receives the sampled water level uploaded by the submersible water level sensors in each well. The control unit receives the real-time water level Hc output by the well monitoring unit. The PLC reads the target water level H, upper limit deviation ΔH, alarm water level, and stabilization set time according to the well number, and outputs start command, stop command, or alarm interlock command. The pump execution unit receives the commands output by the PLC, and the remote terminal sends the commands to the corresponding frequency converter according to the well number. The frequency converter drives or stops the corresponding submersible pump.

[0024] The equivalent radius of the foundation pit is calculated from its planar dimensions and used as the planar scale input for well placement and inflow calculation. The aquifer thickness is derived from the thickness data of the aquifer corresponding to the dewatering design and used as the vertical scale input for groundwater entering the dewatering control area. The permeability coefficient is derived from geological survey or dewatering design data and used as the aquifer's permeability input. The design drawdown is derived from the foundation pit's dewatering control requirements and used as the target drawdown depth input. After reading the above data, the well placement monitoring unit first distinguishes the functional areas of the in-pit dewatering wells and the out-of-pit pressure reduction wells. The in-pit dewatering wells are placed within the foundation pit excavation area to drain groundwater within that area; the out-of-pit pressure reduction wells are placed outside the foundation pit to intercept lateral runoff and reduce water pressure outside the pit.

[0025] When determining the number of wells, the well monitoring unit uses the equivalent radius of the foundation pit, aquifer thickness, permeability coefficient, and design drawdown to calculate the total inflow Q of the foundation pit, and also calculates the output q of a single well. The total inflow Q of the foundation pit serves as the input for the water volume that the dewatering well group needs to discharge, while the output q of a single well serves as the input for the pumping capacity of a single well. The theoretical number of wells n is determined by the ratio of the safe-amplified total inflow Q of the foundation pit to the output q of a single well, with a safety amplification factor of 1.1, i.e., n = 1.1Q / q. The resulting theoretical number of wells is then rounded up, and the rounded number of wells corresponds to the number of drainage wells inside the pit and the number of pressure-reducing wells outside the pit, respectively.

[0026] Submersible water level sensors are installed in the corresponding wells at a depth below the target water level H and above the sedimentation zone at the bottom of the well. The water level collected by the sensor is the original sampling water level. After receiving the original sampling water level, the well monitoring unit converts it to a unified elevation benchmark to obtain the real-time water level Hc. The real-time water level Hc is sent to the control unit along with the well number. After receiving the data, the control unit first identifies the well number, and then reads the target water level H, upper limit deviation ΔH, alarm water level, and stabilization set time for the same well number from the parameter table. If the real-time water level Hc is missing, the well number is missing, or the well number does not correspond to the parameter table, the PLC will not use the data to generate normal start / stop commands; if the communication status signal is interrupted, the PLC enters the alarm interlock branch.

[0027] When the PLC performs water level start / stop judgment, the input data includes the real-time water level Hc, target water level H, upper limit deviation ΔH, and stabilization set time for the same well number. The PLC first compares the real-time water level Hc with the control limit (H+ΔH) after adding the upper limit deviation ΔH to the target water level H. When the real-time water level Hc is greater than this control limit, i.e., Hc > H+ΔH, the PLC generates a start command for that well number. The start command is output to a remote terminal, which sends the start command to the corresponding frequency converter according to the well number. After receiving the start command, the frequency converter drives the corresponding submersible pump to run. After the submersible pump starts running, the submersible water level sensor in that well continues to collect water level data, and the next real-time water level Hc is sent to the PLC for judgment.

[0028] When the real-time water level Hc is not greater than the target water level H plus the upper limit deviation ΔH (i.e., Hc ≤ H + ΔH), the PLC does not directly stop the pump. Instead, it reads the stabilization set time for the same well number and begins accumulating the stabilization time. During the accumulation period, the PLC continuously reads the real-time water level Hc for the same well number, and after each read, it re-compares the real-time water level Hc with the target water level H plus the upper limit deviation ΔH. If any read result again satisfies that the real-time water level Hc is greater than the control limit, the PLC clears the accumulated stabilization time and re-enters the start-up judgment branch. If the continuous read results all satisfy that the real-time water level Hc is not greater than the control limit, and the accumulated time reaches the stabilization set time, the PLC generates a stop command for that well number. The stop command is output to the remote terminal, which sends it to the corresponding frequency converter, and the frequency converter stops the corresponding submersible pump.

[0029] The PLC also reads the alarm water level, pump operation feedback signal, and communication status signal. The alarm water level is bound to the well number and used for water level alarm judgment within the same well number. The pump operation feedback signal is fed back to the control unit by the corresponding submersible pump or frequency converter, indicating whether the submersible pump is currently running or stopped. The communication status signal indicates whether the communication link between the PLC, remote terminal, and frequency converter remains valid. The PLC compares the real-time water level Hc with the alarm water level; simultaneously, it checks the pump operation feedback signal against the issued start or stop commands. If the real-time water level Hc reaches the alarm water level, or the pump operation feedback signal is inconsistent with the commands issued by the PLC, or the communication status signal is interrupted, the PLC outputs an alarm interlock command.

[0030] After the alarm interlock command is output, the remote terminal receives the command and sends it to the frequency converter under the corresponding well number. Upon receiving the alarm interlock command, the frequency converter stops executing the start / stop regulation of the corresponding submersible pump. If the alarm is triggered by the real-time water level Hc reaching the alarm level, the PLC retains the alarm status for that well number and continues to receive subsequent real-time water level Hc data uploaded by the submersible water level sensor. If the alarm is triggered by a discrepancy between the pump operation feedback signal and the start command, the PLC uses this feedback anomaly as a pump failure trigger condition for the corresponding well number. If the alarm is triggered by a discrepancy between the pump operation feedback signal and the stop command, the PLC uses this feedback anomaly as a stop anomaly trigger condition for the corresponding well number. If the alarm is triggered by a communication status signal interruption, the PLC will no longer use the unreturned pump operation feedback signal as normal feedback data.

[0031] The pump unit execution unit includes a remote terminal, a frequency converter, and a submersible pump. The remote terminal receives start commands, stop commands, and alarm interlock commands from the PLC. Command data includes at least a start number and command type. After identifying the start number, the remote terminal sends the command to the corresponding frequency converter. When the frequency converter receives a start command, it outputs a drive signal to the corresponding submersible pump; when it receives a stop command, it stops outputting the drive signal; and when it receives an alarm interlock command, it stops executing the start / stop regulation of the submersible pump.

[0032] The remote terminal also reads the real-time water level Hc for the same well number. The input for the water level change rate is the previous real-time water level Hc, the next real-time water level Hc, and the time interval between the two readings. The previous real-time water level Hc comes from the previous sampling period for that well number, and the next real-time water level Hc comes from the current sampling period for that well number. The reading time interval is determined by the remote terminal based on the two reading times. The remote terminal determines the water level change rate based on the difference between the two real-time water levels Hc and the reading time interval. After the water level change rate is generated, the remote terminal compares it with a preset rate of decline value.

[0033] When the water level change rate is less than the preset descent rate, the remote terminal generates adjustment data to increase the output frequency and writes it to the corresponding frequency converter. The frequency converter drives the submersible pump at the adjusted output frequency. After the submersible pump starts running, the water level in the well continues to be collected by the submersible water level sensor, and the subsequent real-time water level Hc is returned to the remote terminal as input for the next round of water level change rate calculation. When the water level change rate is greater than the preset descent rate and the real-time water level Hc is close to the target water level H, the remote terminal generates adjustment data to decrease the output frequency and writes it to the corresponding frequency converter. The frequency converter drives the submersible pump at the decreased output frequency. If the remote terminal only obtains the real-time water level Hc once and cannot form the difference between the two real-time water levels, the water level change rate will not be generated in this cycle. The remote terminal will first execute the start or stop command issued by the PLC, and then calculate the water level change rate after obtaining the next real-time water level Hc.

[0034] Before executing the start command, the pump unit reads the cumulative runtime and operating status of each submersible pump under the same well type. The same well type includes submersible pump sets corresponding to in-pit drainage wells and submersible pump sets corresponding to out-of-pit pressure reduction wells. The cumulative runtime comes from the pump operation records stored in the remote terminal, and the operating status comes from feedback from the pump or frequency converter. The remote terminal first eliminates submersible pumps that are not in a startable state, then compares the cumulative runtimes among the remaining submersible pumps, and selects the submersible pump with the shortest cumulative runtime as the submersible pump to be started.

[0035] Once the submersible pump to be started is identified, the remote terminal reads the status of the inverter corresponding to that pump. If the inverter is in an operable state, the remote terminal sends a start command to the inverter, which then drives the submersible pump to be started. If the inverter is in a faulty state, the remote terminal excludes the submersible pump to be started and returns to the set of remaining operable submersible pumps to re-compare the cumulative running time, selecting the new submersible pump with the shortest cumulative running time as the next to be started. After re-selection, the remote terminal continues to read the status of the inverter. This path ensures that the start command is not sent to the submersible pump that has been identified as having an inverter fault.

[0036] During system operation, data flows into the corresponding processing path according to the well number. The submersible water level sensor outputs the sampled water level; the well monitoring unit converts the sampled water level into a real-time water level Hc; the control unit reads the real-time water level Hc, target water level H, upper limit deviation ΔH, alarm water level, and stabilization set time according to the well number; the PLC outputs start, stop, or alarm interlock commands; the remote terminal receives the commands and sends them to the corresponding frequency converter; the frequency converter drives or stops the corresponding submersible pump; the pump operation feedback signal and communication status signal are returned to the PLC for verification in the next cycle. After each round of control is completed, the next real-time water level Hc continues to enter the judgment path for the same well number.

[0037] When the real-time water level Hc reaches the alarm level, the PLC outputs an alarm interlock command, and the remote terminal stops executing start / stop adjustments to the corresponding strain gauge. If the PLC has issued a start command but the pump operation feedback signal does not display the operating status, the PLC outputs an alarm interlock command. If the PLC has issued a stop command but the pump operation feedback signal does not display the stop status, the PLC outputs an alarm interlock command. When the communication status signal is interrupted, the PLC outputs an alarm interlock command, and the remote terminal stops executing start / stop adjustments to the corresponding submersible pump. In cases where the real-time water level Hc is missing, the well number cannot be matched, or the feedback signal is not returned, the PLC does not use the missing data as a source of data to meet normal start / stop conditions; instead, it enters an anomaly judgment based on the communication status signal or feedback status.

[0038] In the above implementation, after the basic well layout parameters are entered into the well layout monitoring unit, well locations and well numbers are generated; the submersible water level sensor collects the water level and outputs the real-time water level Hc; the PLC calls the target water level H, upper limit deviation ΔH, alarm water level, and stabilization set time according to the well number; the remote terminal forwards PLC instructions according to the well number and calculates the water level change rate; the frequency converter receives instructions or frequency adjustment data output by the remote terminal; the submersible pump performs operation or stop actions; the pump operation feedback signal and communication status signal are returned to the PLC. The source, processing location, and output destination of each data are all bound to the well number.

[0039] Example For example, a deep foundation pit project with three underground levels has a plan dimension of 80m × 60m and a foundation pit area A = 4800m². 2 The perimeter of the foundation pit is approximately 280m, and the excavation depth is 18.0m. The initial groundwater level at the site is -2.50m, and the design elevation of the bottom of the foundation pit is -18.00m. According to the dewatering control requirements for the foundation pit, the controlled water level inside the pit needs to be lowered to 1.00m below the bottom of the pit; therefore, the target water level H inside the pit is taken as -19.00m.

[0040] During the well placement parameter input phase, the well placement monitoring unit receives data such as the equivalent radius of the foundation pit, aquifer thickness, permeability coefficient, and design drawdown. The equivalent radius r0 of the foundation pit is calculated using a circle of equal area, and the formula is: r0= = ≈39.09m.

[0041] The main dewatering control target at the site is a confined aquifer consisting of fine sand interbedded with medium sand. The aquifer's top elevation is approximately -7.00m, its bottom elevation is approximately -25.00m, and its thickness is M=18.00m. Based on field pumping tests and geological survey data, the permeability coefficient K is taken as 6.0m / d. The design drawdown S within the pit is calculated from the initial groundwater level to the target water level within the pit, S=19.00-2.50=16.50m. The depressurization well outside the pit is designed with a drawdown Southeast=13.50m to reduce the water pressure outside the pit without excessively depressurizing the surrounding groundwater.

[0042] During the well type classification phase, the in-pit dewatering wells are arranged within the excavation area of ​​the foundation pit to handle groundwater drainage within the excavation area; the external pressure reduction wells are arranged approximately 3.0m outside the retaining structure to intercept lateral runoff and reduce water pressure outside the pit. The in-pit dewatering wells are designed to have a depth of 26.0m, with filter pipes mainly located between -8.00m and -24.00m; the external pressure reduction wells are designed to have a depth of 32.0m, with filter pipes mainly located between -10.00m and -30.00m.

[0043] During the well count phase, the radius of influence R is calculated using the empirical formula for dewatering in water-rich sand layers: R= .

[0044] Substituting S=16.50m, K=6.0m / d, and M=18.00m, we get: R= =342.95m.

[0045] The total inflow Q of the foundation pit is calculated using the equivalent well formula for a group of wells in a confined aquifer: Q = 2πKMS / ln[(R+r0) / r0].

[0046] Substituting K=6.0m / d, M=18.00m, S=16.50m, R=342.95m, and r0=39.09m, we get: Q=2×3.1416×6.0×18.00×16.50 / ln[(342.95+39.09) / 39.09]=4911.5m 3 / d.

[0047] The single-well water output q was determined based on the results of on-site test pumping and the effective continuous operation capability of the submersible pump. The stable test pumping output was taken as 220 m³ / s. 3 / d, and simultaneously select a rated flow rate of 15m³ / d. 3 For a submersible pump with a capacity of / h, calculated based on an effective operating coefficient of 0.61: q = 24 × 15 × 0.61 = 219.6m 3 / d.

[0048] Therefore, the single well water output is taken as q=220m³. 3 / d. The theoretical number of wells n is determined by the ratio of the total inflow Q of the foundation pit after safety amplification to the single well output q. The safety amplification factor is taken as 1.1, and the calculation formula is: n = 1.1Q / q.

[0049] Substituting Q=4911.5m 3 / d、q=220m 3 / d, resulting in: n = 1.1 × 4911.5 / 220 = 24.56.

[0050] After rounding up, 25 dewatering wells were selected. Of these, 13 were in-pit drainage wells and 12 were external pressure-reducing wells. The average service area of ​​the in-pit drainage wells is: 4800 / 13=369.2m 2 / mouth, The calculated well spacing is approximately: ≈19.2m.

[0051] External pressure relief wells are arranged around the perimeter of the foundation pit, with an average well spacing of approximately: 280 / 12 = 23.3m.

[0052] The above well spacing matches the commonly used well spacing control range of 18m to 25m in deep foundation pits with water-rich sand layers in urban areas.

[0053] During the water level monitoring phase, the target water level H of the drainage well inside the pit is set at -19.00m, the sensor installation elevation is set at -21.00m, the sedimentation section at the bottom of the well is located between -24.50m and -26.00m, and the sensor is 3.50m above the sedimentation section. For the pressure-reducing well outside the pit, the target water level H is set at -16.00m, the sensor installation elevation is set at -18.00m, the sedimentation section at the bottom of the well is located between -30.50m and -32.00m, and the sensor is 12.50m above the sedimentation section. The submersible water level sensor has a range of 0m to 30m, a measurement accuracy of ±0.05%FS, and a maximum water level error of no more than ±0.015m.

[0054] Water level data is uniformly converted to the project's ±0.000 elevation datum. If the water depth value collected by the sensor is d, and the sensor installation elevation is Zs, then the real-time water level Hc is calculated using the following formula: Hc = Zs + d.

[0055] For example, if the sensor installation elevation of well No. 1 in the pit is Zs=-21.00m and the sampling water depth is d=2.20m, then the real-time water level is: Hc = -21.00 + 2.20 = -18.80m.

[0056] During the control parameter configuration phase, the system establishes a parameter table for each well. The parameter table includes at least the well number, well type, target water level H, upper limit deviation ΔH, alarm water level, stabilization setting time, sensor installation elevation, frequency converter address, and submersible pump number. For the in-pit dewatering wells, the target water level H is set to -19.00m, the upper limit deviation ΔH to 0.50m, the start / stop control limit H+ΔH=-18.50m, the alarm water level to -17.50m, and the stabilization setting time to 600s. For the external depressurization wells, the target water level H is set to -16.00m, the upper limit deviation ΔH to 0.50m, the start / stop control limit H+ΔH=-15.50m, the alarm water level to -14.80m, and the stabilization setting time to 900s.

[0057] Each of the 25 wells corresponds to one of the 25 frequency converters, with each converter address and well number individually linked. The wells inside the pit are numbered JN-01 to JN-13, and the wells outside the pit are numbered JW-01 to JW-12. The sampling cycle for the submersible water level sensor is 60 seconds, the PLC program scan cycle is 1 second, and the communication heartbeat cycle between the remote terminal and the frequency converter is 5 seconds. Communication is considered interrupted if no valid communication status is returned after 6 consecutive heartbeat cycles; that is, the communication interruption determination time is 30 seconds.

[0058] During the normal start-up and shutdown control phase, the PLC reads the real-time water level Hc, target water level H, upper limit deviation ΔH, and stabilization set time according to the well number, and compares the real-time water level Hc with the control limit H+ΔH. For drainage wells within the pit, the control limit is: -19.00 + 0.50 = -18.50m.

[0059] For external depressurization wells, the control limits are: -16.00 + 0.50 = -15.50m.

[0060] For example, when the real-time water level Hc of well JN-01 inside the pit is -18.20m, since -18.20m > -18.50m, it indicates that the water level is 0.30m above the allowable control limit, and the PLC generates a start command for well JN-01. When the real-time water level Hc of well JW-01 outside the pit is -15.20m, since -15.20m > -15.50m, the PLC generates a start command for well JW-01.

[0061] The start command data frame includes a hash symbol, command type, initial target frequency value, and timestamp. The initial target frequency value is 35Hz, and the inverter's allowable adjustment range is 30Hz to 50Hz. The submersible pump should return a running feedback signal within 30 seconds of starting. If it does not return to running status within 30 seconds, the PLC enters the feedback abnormality alarm interlock branch.

[0062] When the real-time water level Hc is not greater than the control limit H+ΔH, the PLC does not directly stop the pump, but starts accumulating stabilization time. For example, when Hc = -18.70m in well JN-01 inside the pit, since -18.70m ≤ -18.50m, the PLC enters stabilization timing, with a stabilization set time of 600s. When Hc = -15.80m in well JW-01 outside the pit, since -15.80m ≤ -15.50m, the PLC enters stabilization timing, with a stabilization set time of 900s.

[0063] The PLC reads valid water level data every 60 seconds. For wells inside the pit, if 10 consecutive samples consistently meet the condition Hc ≤ -18.50m, the cumulative stabilization time reaches 600s; for wells outside the pit, if 15 consecutive samples consistently meet the condition Hc ≤ -15.50m, the cumulative stabilization time reaches 900s. If well JN-01 inside the pit has been stable for 420s, and the next sample Hc = -18.30m, since -18.30m > -18.50m, the PLC resets the 420-second cumulative value and either maintains or re-outputs the start control. If all consecutive readings meet the shutdown conditions and the cumulative time reaches the set stabilization time, the PLC generates a shutdown command for that well number. A stop feedback signal should be returned within 30 seconds of the shutdown command being issued; if the feedback is still in running state, the PLC determines it as a shutdown anomaly and outputs an alarm interlock command.

[0064] During the alarm interlock control phase, the alarm water level of the drainage well inside the pit is set to -17.50m, which is 1.00m higher than the start / stop control limit of -18.50m; the alarm water level of the pressure-reducing well outside the pit is set to -14.80m, which is 0.70m higher than the start / stop control limit of -15.50m. The alarm judgment condition for wells inside the pit is Hc ≥ -17.50m, and the alarm judgment condition for wells outside the pit is Hc ≥ -14.80m. For example, when the real-time water level of well JN-01 inside the pit is Hc = -17.40m, since -17.40m is higher than the alarm water level of -17.50m, the PLC outputs an alarm interlock command.

[0065] The pump operation feedback signals include the inverter's operating position, fault position, current feedback value, and output frequency feedback value. When the operating position is 1 and the current feedback value is greater than 20% of the rated current, the PLC determines that the submersible pump is in an effective operating state. If, after the PLC has issued a start command, the operating position is still 0 within 30 seconds, or the operating position is 1 but the current feedback value is less than 20% of the rated current, it is determined that the start feedback is abnormal. If, after the PLC has issued a stop command, the operating position is still 1 within 30 seconds, or the output frequency feedback value is still greater than 5Hz, it is determined that the stop feedback is abnormal.

[0066] The communication link uses RS485 or industrial Ethernet. The remote terminal sends a heartbeat signal to the PLC every 5 seconds. If no heartbeat signal is sent for 30 consecutive seconds, the communication status signal is considered interrupted, the PLC outputs an alarm interlock command, and the remote terminal stops executing the start / stop adjustment of the corresponding submersible pump. After communication is restored, it must remain stable and effective for 3 consecutive heartbeat cycles (15 seconds) before the communication anomaly flag can be removed.

[0067] After an alarm interlock occurs, the corresponding frequency converter remains in a state where automatic start / stop is prohibited. The remote terminal only retains the functions of water level acquisition and feedback upload, and no longer executes frequency increase / decrease commands for that well number. If the alarm is triggered by the real-time water level Hc reaching the alarm level, the water level alarm state will remain until the real-time water level Hc is 0.30m below the alarm level for 5 consecutive sampling cycles before manual reset is allowed. For example, if the alarm water level in the pit is -17.50m, a reset is allowed only after 5 consecutive sampling cycles where Hc ≤ -17.80m. If the alarm is triggered by a startup feedback abnormality, the system records fault code F01 and writes the submersible pump for that well number as not startable. If the alarm is triggered by a shutdown feedback abnormality, the system records fault code F02 and prohibits the automatic restart of that well number until manual confirmation that the frequency converter output has been cut off. If the alarm is triggered by a communication status signal interruption, the system records fault code F03. The PLC retains the last valid water level value before the interruption but does not use it for subsequent normal start / stop judgments.

[0068] During the frequency conversion regulation phase, the remote terminal reads the real-time water level Hc twice for the same well number, and calculates the water level drop rate v based on the time interval between the two readings. The water level drop rate is calculated using the following formula: v = (Hc before - Hc after) / Δt, The unit is m / h. Here, Hc represents the real-time water level before the previous sampling period, and Hc represents the real-time water level after the current sampling period. Δt is the interval between two sampling periods. In this example, the sampling interval is 60 seconds, i.e., Δt = 1 / 60h.

[0069] For example, in well JN-01, the initial Hc value before the current cycle is -18.20m, and the subsequent Hc value after the current cycle is -18.24m. Therefore: v=[-18.20-(-18.24)] / (1 / 60)=2.40m / h.

[0070] To balance precipitation efficiency and surrounding settlement control, the preset descent rate is set at 1.50 m / h; when the water level is less than 0.30 m from the target water level, the preset descent rate is automatically reduced to 0.60 m / h to avoid over-pumping when approaching the target water level.

[0071] When v < 1.50 m / h and the real-time water level Hc is still higher than the control limit H + ΔH, the remote terminal increases the inverter output frequency by 2 Hz each time, with a maximum of 50 Hz. For example, if the inverter's current frequency is 35 Hz and v = 0.80 m / h is calculated, the adjusted frequency will be 37 Hz. When v > 0.60 m / h and |Hc - H| ≤ 0.30 m, the remote terminal decreases the inverter output frequency by 2 Hz each time, with a minimum of 30 Hz. For example, if the well in the pit has H = -19.00 m, Hc = -18.80 m, |Hc - H| = 0.20 m, and v = 1.20 m / h, the inverter frequency will be reduced from 40 Hz to 38 Hz.

[0072] If the system only obtains the real-time water level Hc once after startup, and cannot form the difference between the two real-time water levels, then the water level change rate will not be generated in this cycle. In the first sampling cycle after system startup, only Hc0 and the sampling time t0 are recorded. After obtaining Hc1 and t1 in the second sampling cycle, v = (Hc0 - Hc1) / (t1 - t0) is calculated.

[0073] During the pump rotation control phase, the remote terminal accumulates the pump running time every 10 minutes, with the accumulated value accurate to 0.1 hours. The drainage well groups JN-01 to JN-13 inside the pit are independently sorted, and the pressure-reducing well groups JW-01 to JW-12 outside the pit are also independently sorted to avoid mixed rotation of wells inside and outside the pit. The remote terminal first removes submersible pumps that are not in a startable state, then compares the accumulated running time among the remaining submersible pumps, selecting the submersible pump with the shortest accumulated running time as the submersible pump to be started.

[0074] For example, in the pit drainage well group, JN-01 has accumulated 186.4 hours of operation, JN-02 has accumulated 172.8 hours of operation, JN-03 has accumulated 194.1 hours of operation, and JN-04 is in a fault state. Then, after the remote terminal removes JN-04, it will prioritize JN-02, which has the shortest accumulated running time, as the submersible pump to be started from among the startable pumps.

[0075] Once the submersible pump is confirmed to start, the remote terminal reads the status of the frequency converter corresponding to that pump. The operable status of the frequency converter includes no fault codes, normal DC bus voltage, no overcurrent alarm at the output, and the remote control enable bit being 1. If all conditions are met, the remote terminal allows the issuance of a start command. If JN-02 has the shortest cumulative running time, but its frequency converter returns an overcurrent fault code E.OC, the remote terminal removes JN-02 from the current set of startable pumps and selects JN-05 from the remaining pumps with the second shortest cumulative running time. If the frequency converter of JN-05 is in normal condition, the start command is sent to the frequency converter corresponding to JN-05.

[0076] The submersible pump has a power rating of 11kW and a rated flow rate of 15m³ / h. 3 / h, rated head 35m, inverter output frequency range is 30Hz to 50Hz, normal starting frequency is 35Hz.

[0077] During system operation, the complete control cycle is 60 seconds. Within a single cycle, water level acquisition, elevation conversion, PLC judgment, remote terminal distribution, inverter feedback, and data recording are completed sequentially. Historical data is saved at least for real-time water level Hc, pump operating status, inverter frequency, cumulative runtime, alarm codes, and communication status, with a saving interval of 60 seconds. After 24 hours of continuous operation, 1440 sets of water level and pump control data can be generated for each well, which are used to verify the water production capacity of a single well and to optimize the start-up and shutdown strategy of the well group.

[0078] In deep foundation pit engineering in water-rich urban areas, the number and spacing of wells to be jointly placed inside and outside the pit can be determined by parameters such as equivalent radius, aquifer thickness, permeability coefficient, design drawdown, and single well water output capacity. By controlling parameters such as target water level, upper limit deviation, alarm water level, stable setting time, sampling cycle, and feedback time limit, automatic start-up and shutdown, alarm interlocking, frequency conversion regulation, and pump group rotation control of each well can be realized, thereby forming a continuous, verifiable, and traceable automated dewatering control process for the drainage inside the pit and the depressurization outside the pit.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An automated dewatering water level control system for deep foundation pits, comprising internal and external well layouts, used for water level monitoring and pump control between a group of dewatering wells, observation wells, and a remote terminal, wherein the group of dewatering wells includes internal drainage wells and external pressure-reducing wells, characterized in that... The system includes: The well monitoring unit determines the well locations based on the equivalent radius of the foundation pit, the thickness of the aquifer, the permeability coefficient, and the design drawdown. It arranges in-pit dewatering wells inside the foundation pit and out-of-pit depressurization wells outside the foundation pit to form a dewatering well group. Submersible water level sensors are arranged in the dewatering well group and the observation wells to collect real-time water levels. The control unit, connected to the combined well placement unit, reads the real-time water level via a PLC and compares the real-time water level with the target water level and the upper limit deviation. When the real-time water level is greater than the sum of the target water level and the upper limit deviation, the PLC issues a start command to pump water from the corresponding well. When the real-time water level is not greater than the sum of the target water level and the upper limit deviation, and continues to stabilize for a set time, the PLC issues a stop command and generates an alarm interlock command when an alarm water level, pump failure, or communication interruption is triggered. The pump unit execution unit is connected to the control decision unit. The remote terminal receives the start command, the stop command and the alarm interlock command. It dynamically adjusts the inverter output frequency according to the real-time water level change rate and prioritizes starting the submersible pump with the shortest cumulative running time.

2. The automated dewatering and water level control system for deep foundation pits with combined internal and external well placement as described in claim 1, characterized in that, The in-pit dewatering well is used to drain groundwater within the excavation area, and the external depressurization well is used to intercept lateral runoff and reduce water pressure outside the pit.

3. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, The well monitoring unit collects the equivalent radius of the foundation pit, the thickness of the aquifer, the permeability coefficient, and the design drawdown to obtain the foundation parameters for well placement; Read the basic parameters of the well layout and distinguish the effective range of the drainage wells inside the pit and the pressure reduction wells outside the pit. Calculate the total water inflow of the pit and the water output of a single well, and determine the theoretical number of wells to form a group of dewatering wells. Submersible water level sensors are installed in the drainage well inside the pit, the pressure reduction well outside the pit, and the observation well. The water level sampled by the submersible water level sensors is converted to a unified elevation benchmark and the real-time water level is output. Among them, the installation depth of the submersible water level sensor should be lower than the target water level of the corresponding well and higher than the sand settling section at the bottom of the well.

4. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 3, characterized in that, The total inflow of the foundation pit and the output of a single well are calculated using the standard incomplete well formula. The theoretical number of wells is calculated according to the formula n=1.1Q / q, where Q represents the total inflow of the foundation pit, q represents the output of a single well, and n represents the theoretical number of wells. The theoretical well count is rounded up.

5. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, The control unit receives the real-time water level collected by the submersible water level sensor via PLC, and reads the corresponding target water level, upper limit deviation and stabilization setting time according to the well number of each well in the precipitation well group. When the real-time water level is greater than the sum of the target water level and the upper limit deviation, i.e., Hc > H + ΔH, where Hc represents the real-time water level, H represents the target water level, and ΔH represents the upper limit deviation, the PLC sends a start command to the corresponding well. When the real-time water level is not greater than the sum of the deviations between the target water level and the upper limit, i.e., Hc≤H+ΔH, and continues to reach the set stable time, the PLC sends a shutdown command to the corresponding well.

6. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 5, characterized in that, When the PLC issues a shutdown command to the corresponding well, it needs to continuously read the real-time water level corresponding to the same well number, and compare the real-time water level with the sum of the target water level and the upper limit deviation after each reading; If any reading satisfies the condition Hc > H + ΔH again, the PLC clears the accumulated stabilization time and restarts the timer; if consecutive readings all satisfy Hc ≤ H + ΔH, and the accumulated time reaches the set stabilization time, the PLC issues the stop command.

7. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, The control unit also reads the alarm water level, the water pump operation feedback signal and the communication status signal, compares the real-time water level with the alarm water level, and verifies the water pump operation feedback signal with the start command or stop command issued by the PLC. When the real-time water level reaches the alarm water level, the pump operation feedback signal is inconsistent with the start or stop command issued by the PLC, or the communication status signal is interrupted, the PLC issues the alarm interlock command.

8. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, The control unit stores the target water level, upper limit deviation, alarm water level, and stabilization setting time according to the well numbers of the drainage wells inside the pit, the pressure reduction wells outside the pit, and the observation wells. When receiving the real-time water level, the control unit reads the corresponding target water level, upper limit deviation, alarm water level, and stabilization setting time according to the well number. The PLC only performs a joint judgment on the real-time water level corresponding to the same well number, the corresponding target water level, the upper limit deviation, the alarm water level, and the stable set time.

9. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, The pump unit execution unit consists of a remote terminal, a frequency converter, and a submersible pump. The remote terminal receives start commands, stop commands, and alarm interlock commands from the PLC and sends the corresponding commands to the corresponding frequency converter according to the well number of each well in the dewatering well group. When the frequency converter receives a start command, it drives the corresponding submersible pump to run; when it receives a stop command, it stops the corresponding submersible pump from running; and when it receives an alarm interlock command, it stops executing the start-stop regulation of the corresponding submersible pump. The remote terminal continuously reads the real-time water level corresponding to the same well number, and calculates the water level change rate based on the difference between the real-time water levels read before and after and the reading time interval. When the water level change rate is less than the preset descent rate value, the remote terminal increases the output frequency of the strain gauge frequency converter; when the water level change rate is greater than the preset descent rate value and the real-time water level is close to the target water level, the remote terminal decreases the output frequency of the strain gauge frequency converter; the frequency converter drives the corresponding submersible pump to operate according to the adjusted output frequency.

10. The automated dewatering and water level control system for combined internal and external well placement in deep foundation pits according to claim 1, characterized in that, Before executing the start command, the pump unit reads the cumulative running time and operating status of each submersible pump under the same well type, and selects the submersible pump with the shortest cumulative running time from the submersible pumps that are in the startable state as the submersible pump to be started. When the frequency converter corresponding to the submersible pump to be started is in an operational state, the remote terminal will send a start command to the corresponding frequency converter. When the frequency converter corresponding to the submersible pump to be started is in a fault state, the remote terminal excludes the submersible pump to be started and reselects the submersible pump with the shortest cumulative running time from the remaining submersible pumps that are in the startable state.

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