Deep foundation pit drainage system and using method

Abstract

The invention relates to the technical field of foundation pit drainage, and provides a deep foundation pit drainage system and a use method.The method comprises the steps that a1, an annular dewatering well is arranged on the periphery of a deep foundation pit, and underground water is collected and lowered through the annular dewatering well; a2, a drainage network in the foundation pit is established to eliminate surface rainfall and seepage water; a3, based on a preset water level control strategy, a drainage pumping device is started to drain the collected underground water away from the foundation pit; a4, hydrological changes inside and outside the deep foundation pit are monitored, and operation parameters of the dewatering well and the drainage system are adjusted in time so that the safe water level state in the deep foundation pit can be maintained; through the scheme of the embodiment of the invention, the problem of how to effectively prevent underground water from seeping into the foundation pit in a high-water-level area by the deep foundation pit drainage system can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit drainage, and in particular to a deep foundation pit drainage system and a use method thereof. Background Art

[0002] A deep foundation pit drainage system and a method of use thereof relate to groundwater management technology in the field of engineering construction. The system can effectively guide the water generated inside the deep foundation pit through a series of arranged water collecting pipes and pumping equipment to ensure the safety of operations and the stability of the soil during the construction process. In the design, multiple schemes are usually considered, such as well point dewatering, interception walls or waterproof barriers combined with pumping and drainage technology, to achieve a good hydrological environment regulation effect for different geological and hydrogeological conditions.

[0003] When facing deep foundation pit projects in high-water areas, a core issue that needs to be solved urgently is to ensure that groundwater can be effectively prevented from seeping into the foundation pit. If not handled properly, it will cause a series of safety hazards such as increased load on the supporting structure and reduced stratum stability, and may even directly threaten the safety of the construction site. To overcome this problem, it is usually necessary to select appropriate stratum sealing methods based on field survey data, combined with precise calculations and monitoring mechanisms, to improve the waterproofing ability and stability of deep foundation pit projects, and achieve the goal of safe and controllable entire construction process. Summary of the invention

[0004] In view of this, the embodiments of the present disclosure provide a deep foundation pit drainage system and a method of use, which at least partially solve the problems existing in the prior art.

[0005] A deep foundation pit drainage system and a method of use, comprising:

[0006] Step a1, arranging annular precipitation wells around the deep foundation pit, collecting groundwater through the annular precipitation wells and lowering the groundwater level;

[0007] Step a2, establishing a drainage network inside the foundation pit to remove surface precipitation and seepage;

[0008] Step a3, starting the drainage pumping equipment to drain the collected groundwater out of the foundation pit based on the preset water level control strategy;

[0009] Step a4, monitoring the hydrological changes inside and outside the deep foundation pit and timely adjusting the operating parameters of the precipitation well and drainage system to maintain a safe water level in the deep foundation pit;

[0010] Preferably, the step a1 specifically includes:

[0011] A1 Select appropriate spacing to arrange drainage well points according to the deep foundation pit design parameters;

[0012] A2 After the drilling hole reaches the predetermined depth, install the water filter pipe section with good permeability;

[0013] A3 Wrap the filter material filling layer outside the water filter pipe section to increase the drainage capacity;

[0014] A4 Arrange each precipitation well in a circular manner and ensure a continuous drainage system;

[0015] A5 Install connecting pipe to ensure the connection between the precipitation well and the main pumping system.

[0016] Preferably, the step a2 specifically includes:

[0017] A1 Design the layout of drainage ditches in the foundation pit to ensure that water can flow smoothly to the collection point;

[0018] A2 Lay waterproof isolation materials in appropriate areas at the bottom of the foundation pit to prevent underwater penetration;

[0019] A3 Establish seepage water interception structure to prevent water intrusion from surrounding soil layers;

[0020] A4 Arrange a sump and install a submersible pump in it to remove the collected water;

[0021] A5 adopts anti-siltation design to ensure that the drainage ditches in the foundation pit are unobstructed.

[0022] Preferably, the step a3 specifically includes:

[0023] A1 sets the initial control water level value and alarm value as operation guidance parameters;

[0024] A2 starts the pre-installed drainage pumps to drain the groundwater;

[0025] A3 arranged for technicians to adjust the pump group to achieve fine control of the water level;

[0026] A4 operates the automatic water level measuring device to continuously record the real-time groundwater conditions;

[0027] A5 uses an intelligent control system to monitor the drainage rate and make timely adjustments.

[0028] Preferably, the step a4 specifically includes:

[0029] A1 deploys environmental monitoring stations to monitor the changing trends of the internal and external environment of the deep foundation pit;

[0030] A2 is equipped with a remote water level sensor to continuously obtain the current underground level value;

[0031] A3 Analyze the impact of deep foundation pit excavation progress on the groundwater system;

[0032] A4 adjusts the intensity of precipitation well operations based on actual water level changes to replenish water sources in a timely manner;

[0033] A5 Implement preventive maintenance plans to reduce the chance of failure and ensure drainage efficiency.

[0034] Preferably, the step a3 of starting the drainage pumping equipment to drain the collected groundwater from the foundation pit based on the preset water level control strategy includes:

[0035] Start drainage according to the real-time water level H in the deep foundation pit monitored;

[0036] Set the safe minimum water level H_min and safe maximum water level H_max as reference benchmarks;

[0037] When the real-time water level H is less than H_min, the drainage pump stops working and enters standby mode;

[0038] When the real-time water level H reaches or exceeds H_max and is lower than the warning water level H_w, the drainage pump is automatically started to drain water until the water level drops below H_max.

[0039] Preferably, the preset water level control strategy is further defined to include the following operations:

[0040] Adjust the control valve opening size C according to the changes in the average rainfall R and evaporation E in the foundation pit;

[0041] Determine the current water level H_c and calculate the remaining safe water volume W based on H_c;

[0042] If H_c is greater than the preset minimum safe water level plus the preset safety threshold ΔH, W is calculated according to the formula: \(W=V_b\times(1R / E)\), where V_b is the capacity of the deep foundation pit;

[0043] Decide whether to increase or decrease the displacement based on W.

[0044] Preferably, the operation of adjusting the opening size of the control valve further comprises:

[0045] Monitor the rainfall intensity I and determine whether it is greater than the threshold \(I_t=H_{\text{max}}\times C / T\), where T is the cycle duration in hours;

[0046] If the rainfall intensity I is greater than the threshold, the valve opening size ΔC1 is reduced;

[0047] If the current time falls within the drainage cycle, the opening size is increased to the initial preset standard C;

[0048] Otherwise, the current opening size of the valve port is fine-tuned to ΔC2 according to the hydrological conditions.

[0049] Preferably, the control of the actual drainage process based on the adjusted opening size of the control valve further includes the following specific operations:

[0050] Measure the real-time rainfall accumulation amount \(A_r\) in the deep foundation pit, and set the maximum allowable accumulation threshold \(A_{r,\max}\) and the minimum allowable accumulation threshold \(A_{r,\min}\);

[0051] Judge whether \(A_r\geq A_{r,\min}\) holds;

[0052] When the measured real-time rainfall accumulation amount \(A_r < A_{r,\min}C\times I / V\times H_b + R_d\), stop the drainage operation; here \(R_d\) represents the drainage rate of the drainage pump;

[0053] In other cases, maintain drainage to ensure that the accumulated water volume \(A_r\) is within a predetermined range, avoiding too high or too low water levels.

[0054] Preferably, when adjusting the water level control strategy according to the current hydrological conditions, the further specific steps include:

[0055] When the continuous rainfall hours \(N\geq\) the preset rainy season critical hours \(N_s\) and \(A_r\geq A_{r,\max}+C\times I / (1H_d)R_d\), where \(H_d\) is the actual water level floating rate, then increase the lower water level threshold to reduce the water volume;

[0056] After the rainfall stops, adjust the upper and lower limits of the actual water level according to the drainage efficiency \(\eta\) and the preset drainage recovery time \(\tau\) to restore the normal level;

[0057] In the non-rainy season stage, if \(N\) is less than the minimum non-rainy season hours \(N_{\min}\) and \(N < N_{\min}(V_h / (R_{\text{average}}\eta))\), then restore the water level control to the normal state;

[0058] Where \(R_{\text{average}}\) represents the average rainfall over a long period of time, and \(V_h\) is the depth of the foundation pit.

[0059] The disclosed embodiment provides a deep foundation pit drainage system and a method for use, comprising: step a1, arranging annular precipitation wells around the deep foundation pit, collecting groundwater through the annular precipitation wells and lowering the groundwater level; step a2, establishing a drainage network inside the foundation pit to remove surface precipitation and seepage; step a3, starting the drainage pumping equipment based on a preset water level control strategy to discharge the collected groundwater out of the foundation pit; step a4, monitoring the hydrological changes inside and outside the deep foundation pit and timely adjusting the operating parameters of the precipitation wells and the drainage system to maintain a safe water level in the deep foundation pit; through the solution of the disclosed embodiment, it is possible to solve the problem of how to effectively prevent groundwater from infiltrating into the foundation pit in the deep foundation pit drainage system in high water level areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a flow chart of a deep foundation pit drainage system and its use method;

[0061] Figure 2 Yes, step a1 is a specific flow chart;

[0062] Figure 3 It is a specific flow chart of step a2;

[0063] Figure 4 Yes, step a3 is a specific flow chart;

[0064] Figure 5 Yes, step a4 is a specific flow chart;

[0065] Figure 6 The flowchart of step a3 is to start the drainage pumping equipment to discharge the collected groundwater from the foundation pit based on the preset water level control strategy;

[0066] Figure 7 It is a flowchart further defining the operation based on the preset water level control strategy including the following:

[0067] Figure 8 is a further flow chart of the operation of adjusting the opening size of the control valve;

[0068] Fig. 9 The actual drainage process is controlled based on the adjusted control valve opening size and also includes the following specific operations: a flow chart;

[0069] Fig.10 It is a flowchart of the specific steps to be further performed when adjusting the water level control strategy according to the current hydrological conditions. DETAILED DESCRIPTION

[0070] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0071] The deep foundation pit drainage system and its use method is a technical solution designed to ensure that the accumulated water can be effectively removed during or after the excavation of the deep foundation pit. The design of this system is particularly important in areas with high groundwater levels. The purpose is to provide a stable working environment by reducing the impact of the groundwater surface, ensure the smooth progress of construction and protect the safety of the foundation pit. The first step is to dig a number of circular precipitation wells around the pit body at a predetermined interval before the excavation of the deep foundation pit. These wells not only need to be able to collect the surrounding groundwater, but also need to have a strong drainage function so that the groundwater can be removed in time to reduce the groundwater head pressure, thereby effectively reducing the groundwater level in the surrounding and base soil layers of the foundation pit, so that the entire foundation pit is in a low groundwater state. As an example, we can consider the engineering situation of a subway construction project in a typical coastal city such as Shanghai. The groundwater level in this area is relatively high due to its proximity to the sea. Under such conditions, some circular precipitation wells with appropriate spacing will be arranged before the foundation pit excavation work is carried out. Drainage pipelines are pre-installed in the precipitation wells to ensure that when the water pump starts to drain, the collected groundwater can be quickly discharged from the deep foundation pit area. For example, when excavating a certain section of a subway line, it is necessary to arrange a deep well with a diameter of about 1m and a depth of more than 3 times the excavation pit as a drainage and downdraft pipe at a distance of about 25 meters around the foundation pit. The design requires that all downdraft wells should be set to a sufficient depth to effectively intercept the incoming groundwater and have a strong suction capacity at the same time. Then, the second step is to build internal drainage pipes inside the deep pit. These pipes are responsible for handling surface water caused by rainfall or water that seeps from the surface so that it no longer accumulates. These pipes are usually set at an appropriate slope to facilitate the smooth flow of accumulated water. For example, in the above-mentioned subway tunnel excavation site, we can also see a pipe that runs through the bottom of the deep pit and has a certain slope for rainwater drainage. The purpose of this design is not only to help guide surface water out of the deep pit, but also to ensure that even if there is a small amount of leakage, it will not accumulate into a dangerous state. Then the third step starts to start the installed submersible water pump to pump the water in the well to the outside of the deep pit and eventually introduce it into the public water system such as the nearby river canal. This process can be triggered by the sensor that monitors the water level in the circular dewatering well to automatically start the control of the pumping equipment to ensure that the water level can always be effectively maintained. At this stage, the construction party can install a water level sensor at the wellhead of each circular well, and set it to automatically start working when the water level reaches 1.6 meters below the bottom of the deep pit to maintain the groundwater level. This step helps to ensure that the normal construction of the foundation pit excavation is not disturbed by high water levels, thereby improving work efficiency and reducing potential safety hazards. The next fourth step is to arrange to monitor the natural hydraulic conditions and drainage effects around the foundation pit during the drainage pumping process, and monitor and analyze the well water discharge and well water extraction to adjust the equipment in time to avoid risks such as well wall collapse caused by excessive water pressure.In the above-mentioned subway line project case in Shanghai, a monitoring team may be set up to monitor the actual effect of the entire drainage project to avoid unexpected problems caused by sudden factors. Combining the above four steps, it can be seen that this drainage design method brings great convenience to foundation pit construction and can cope with various uncertain conditions to ensure the safety of the project. In this way, the surface runoff or surface seepage generated during the excavation of the foundation pit of the subway construction project located in the high-risk area of ​​groundwater level can be successfully removed and disposed of properly. This not only prevents surface water or rainwater from gathering in the foundation pit during the construction process to form silt and affect the progress, but also solves the key difficulty of how to effectively drain water to maintain construction safety.

[0072] Next, the details of step a1 are described as follows:

[0073] To make the description more intuitive, we can take the operation process in a specific project as an example. Suppose there is a construction pit with a depth of 15 meters in an urban area with a high groundwater level.

[0074] First, execute step A1: The engineering team needs to select the appropriate spacing of drainage wells according to the design parameters of the deep foundation pit, such as excavation depth, groundwater burial depth, and construction period. Usually, a vertical well is drilled every 20 to 30 meters. In this project, 25 meters is selected as the spacing.

[0075] Then execute step A1.2, use professional equipment (drilling rig) to drill according to the determined layout and coordinates. After reaching the expected well depth around the foundation pit, lower a steel pipe with mesh pores as the main structural part of the well body. This structure is usually called a water filter pipe to ensure that a certain amount of water can flow in during the pumping process while preventing soil from entering the drainage system with the water flow.

[0076] Next is step A1.3: Fill the filter material with strong water permeability and air permeability around the filter pipe to prevent siltation and enhance the filtration function. For example, crushed stone or other fine sand, small gravel and other materials suitable for local water quality characteristics are used to form a filter ring layer with a certain thickness. Usually, the filling height of the filter layer exceeds a certain range above the water surface to ensure that the silt is effectively blocked from flowing into the well with the water to cause siltation, and can further improve the permeability during pumping.

[0077] Subsequently, step A1.4 is implemented: each water extraction pipe is laid in sequence in a closed form in the well group, and they are interlaced and linked to each other to form a coherent water extraction circulation system; at the same time, interfaces are reserved at the bottom of the well and the ground outlet to facilitate the later installation of pipelines.

[0078] Finally, proceed to step A1.5: Use pipes to connect each pumping device, guide the extracted liquid in the single well to the central collection pool or directly send it to the surface treatment device, and monitor the operation of the pumping station by setting up pressure sensors so that the operation plan can be adjusted in time when the water volume is too large to avoid problems such as subsidence caused by over-pumping.

[0079] The above five links constitute the specific content of the entire step a1. In actual operation, corresponding adjustments and improvements will be made in combination with the specific construction environment and site conditions. This is a set of standard processes for dewatering deep foundation pits to ensure safety and engineering quality during construction.

[0080] Next, the description of “the step a2 specifically” refers to a series of operations for effective management of internal moisture during the process of constructing a deep foundation pit drainage system.

[0081] A1. Designing the layout of drainage ditches in the foundation pit involves planning the drainage ditches inside the foundation pit so that the ditches can efficiently direct the accumulated water to a specific collection location to ensure that the water flow is not blocked, thereby achieving a good drainage balance. For example, when constructing a deep foundation pit located next to a hillside, engineers need to set the appropriate slope and drainage ditch direction by carefully observing the terrain conditions and considering the dynamic and directional factors of the water flow. In this way, when precipitation or groundwater enters the foundation pit, it can flow along the planned channel to the preset water pool.

[0082] A2.2. To prevent water from seeping in, waterproof isolation materials are laid in appropriate areas at the bottom of the foundation pit. This means that water is prevented from seeping into the soil from the bottom by laying impermeable materials such as polymer composite membranes or waterproof boards in areas prone to seepage. For example, laying a special material covering layer at the bottom of a deep foundation pit can prevent water from rising from the soil below to the working surface through porous materials.

[0083] A2.3. The purpose of establishing a seepage water interception structure is to prevent the infiltration of groundwater from adjacent areas by using waterproof walls or other types of physical barriers, such as driving underground continuous walls or using grouting curtain technology to establish a leak-proof barrier, thereby providing a protective measure to avoid water damage to the surrounding environment caused by deep excavation. For example, the strategy of using concrete retaining structures to surround the foundation pit boundary to prevent nearby water sources from invading the construction site is a practical manifestation of this measure.

[0084] A2.4. Arrange a water collection pit and set up a submersible pump in it to remove the collected water. This means digging a water storage depression and coordinating with an automatic start-stop control submersible pump to remove the excess water collected there by the above methods. A typical practice is to set up a low pit at a selected location on the construction site to temporarily store drainage from all directions, and then install a pumping device to discharge the accumulated excess liquid at any time.

[0085] A2.5. Using anti-clogging design to ensure that the drainage ditches in the foundation pit are unobstructed emphasizes that reasonable design must be adopted to prevent the ditches from losing their effectiveness due to sediments and other debris. In actual project implementation, for example, ditches with slopes and meanders can be designed to reduce the possibility of soil and impurities settling, or cleaning facilities can be arranged at intervals to clear the channels for slag maintenance, etc. to maintain good drainage conditions and stability.

[0086] Next, the sub-steps in "step a3" are described:

[0087] A1 sets the initial control water level value and alarm value. These parameters will provide a reference standard for the actual operation process to ensure the safe and efficient operation of the system. For example, before starting the deep foundation pit drainage system, the construction personnel set an initial control water level after on-site inspection and evaluation - 2 meters from the bottom of the foundation pit, and set the trigger point for the alarm when the water level is too high to 1.5 meters high.

[0088] A3.2 Next, the staff started the five pre-installed automatic drainage pumps according to the predetermined plan. In a construction site practice, in order to ensure the safe progress of the deep foundation pit excavation project, these devices were started one by one to start pumping out the accumulated water to avoid excessive water accumulation on the ground affecting normal work.

[0089] After A3.3, the operation and status of the drainage pump group in operation need to be adjusted to maintain the best working condition, accurately maintain the groundwater pressure within a reasonable range, and prevent engineering hazards caused by water level fluctuations. For example, the technical person in charge may reduce the number of pumps to reduce the suction speed when the water level drops rapidly.

[0090] A3.4 During the same period of time, the automated detection unit continuously records the on-site water pressure change data. For example, when using an ultrasonic monitoring probe to measure the underground liquid level, the latest information is reported to the control system every two minutes.

[0091] A3.5 As part of the overall intelligent management system, the computer can determine whether appropriate changes need to be made based on the data fed back immediately to ensure the normal and stable operation of the entire system. For example, if the water level drops too quickly beyond expectations, the operating frequency of some pump groups can be increased accordingly. In this example, once it is found that the water pressure is too much lower than the predetermined target value, the control software will issue an instruction to increase the number of flow pumps so that the total discharge capacity can be re-matched to the required value.

[0092] Next, the description of "the specifics of step a4" includes multiple detailed operation steps. Each sub-step will be explained below, and examples will be used to help understanding:

[0093] A1 Deployment of environmental monitoring stations to monitor the changing trends of the internal and external environment of deep foundation pits refers to the installation of environmental monitoring equipment at appropriate locations around the foundation pit, such as sensors for measuring air and groundwater quality, in order to continuously track the changes in the surrounding natural environment during the construction process and possible risks. For example, before construction, a series of surveillance cameras and soil hydrological sensors were installed around the foundation pit, which can collect relevant data 24 hours a day and transmit it to the monitoring center in real time. When any abnormal changes in soil or water quality are found, feedback can be given immediately, facilitating timely processing.

[0094] A4.2 Equipped with a remote water level sensor to continuously obtain the current underground level value means installing a water level meter with remote transmission function and long-term operation at a key position in the drainage system (such as a precipitation well) to automatically and continuously monitor and record the actual change status of groundwater. Assuming that a construction site is equipped with a wireless transmission type float liquid level controller, once the increase or decrease of groundwater exceeds the preset limit, an early warning signal will be sent to the main control room.

[0095] A4.3 Analysis of the impact of deep foundation pit excavation progress on the groundwater system refers to the conclusion formed after statistical analysis and comparative calculation of the groundwater content in the area where the excavation activities have been carried out. For example, software tools are used to assist in modeling simulation analysis (such as groundwater mechanics prediction based on finite element or boundary element method), combined with data obtained from field monitoring, to evaluate whether the construction behavior under different working conditions meets the safety standards, and decide on the next reasonable operation accordingly.

[0096] A4.4 Adjusting the intensity of the dewatering well operation based on actual water level changes and replenishing water sources in a timely manner means dynamically changing the pumping power and number of well pumps and other conditions based on the data reported by the water level gauge, and taking remedial measures when necessary to avoid excessive drainage and other problems. If the groundwater level at a certain construction site is found to be continuously and rapidly decreasing beyond the alarm line, the outflow rate can be increased by increasing the number of pumps or changing the frequency setting; if abnormal seepage occurs, external clean water can be appropriately injected to replenish the consumed part to keep the overall level within a stable range.

[0097] A4.5 Implement preventive maintenance plans to reduce the probability of failures and ensure drainage efficiency. The purpose is to regularly arrange equipment inspection and maintenance work and fill in daily record forms to prevent sudden damage to important devices and cause serious accidents such as a significant decline in overall efficiency. For example, in this project, a professional team was specially set up to thoroughly clean and inspect the bottom filter material, valves, and motor connection lines every three months, thereby greatly improving its continuous operation reliability index and reducing unnecessary maintenance time and labor costs.

[0098] Next, it is described that "the step a3 starts the drainage pumping equipment based on the preset water level control strategy to drain the collected groundwater away from the foundation pit."

[0099] In this description, step a3 involves an automated deep foundation pit groundwater drainage control process based on a preset water level control strategy, which mainly includes monitoring the real-time water level and controlling the operation of the drainage pump. This process ensures that the water level inside the foundation pit is stable within a predetermined range.

[0100] The specific implementation contents are as follows:

[0101] First, the actual water level inside the foundation pit (i.e. H) is monitored based on the real-time data. This step is completed by sensors arranged around the foundation pit. Next, two important reference water level values ​​are set as key indicators for the operation of the control system. This includes a lower safety water level threshold called the minimum safety water level (H_min) and a higher safety water level threshold, the maximum safety water level (H_max), which are used to guide the behavior of the automatic pumping equipment.

[0102] During normal operation, when the real-time water level H is lower than the predetermined minimum safe water level H_min, it means that the water has been drained to a certain extent and there is no need to start the drainage pump again. Therefore, the drainage pump will automatically stop working and enter standby mode to wait for the drainage stage to begin again.

[0103] When the water level rise is detected, and the real-time water level H reaches or exceeds the preset maximum safety water level H_max but does not reach the higher-level warning water level H_w (assuming that the water level does not rise so extreme that it will not cause additional alarm processing procedures), the control system will automatically start the pump for continuous pumping and drainage operations to ensure that the groundwater level falls back to the set safety range. When the monitored real-time water level drops and drops below the set maximum safety water level H_max again, the control system will stop the pump.

[0104] To explain more clearly, here is an example: suppose a high-rise building under construction needs to build a large circular foundation pit with a depth of 20 meters and a diameter of 80 meters. The construction site has designed and arranged a series of deep foundation pit waterproofing and rainwater management systems as required. The safe maximum water level H_max and safe minimum water level H_min in the system are +1 meter and +0.5 meter respectively (the above values ​​are calculated relative to the natural floor elevation). When the construction site staff detects that the current actual water level H suddenly rises and reaches 1.5 meters, according to the predefined water level management rules, the following condition is set in the system: H≥H_max (1.5m≥+1m is true and lower than the warning value, such as 2 meters). In this state, the drainage pump will be started and automatically run until the water level drops to the safe maximum value (that is, H<+1 meter); when the water level continues to drop until it is less than +0.5 meters, the system will enter standby and wait for the next drainage demand. This repeated operation can effectively protect the building infrastructure from the influence of groundwater during the construction phase.

[0105] This process effectively manages groundwater resources at the construction site, creating more stable environmental conditions for subsequent construction operations without compromising building safety.

[0106] Next, the description “further defines the preset water level control strategy to include the following operations:

[0107] Adjust the control valve opening size C according to the changes in the average rainfall R and evaporation E in the foundation pit;

[0108] Determine the current water level H_c and calculate the remaining safe water volume W based on H_c;

[0109] If H_c is greater than the preset minimum safe water level plus the preset safety threshold ΔH, W is calculated according to the formula: \(W=V_b\times(1-R / E)\), where V_b is the capacity of the deep foundation pit;

[0110] Decide whether to increase or decrease the displacement based on W."

[0111] According to the data changes of the average rainfall R and evaporation E in the deep foundation pit, the opening size C of the control valve is dynamically adjusted to change the drainage volume and achieve the purpose of automatic water level control. Then, the system will detect and record the current actual water level H_c. Based on H_c and the set safe water level plus a certain water level deviation ΔH, a comparative analysis is performed. If H_c exceeds this value, the remaining safe water storage capacity W in the foundation pit is determined according to the calculation formula: \(W=V_b\times(1-R / E)\), where \(V_b\) represents the total amount of the deep foundation pit. Finally, after obtaining the calculated W value, the system will adjust the drainage volume accordingly to decide whether to increase or decrease the drainage flow.

[0112] To make it easier to understand this process, assume that we have a deep foundation pit, the safe minimum water level of the foundation pit is preset to 1 meter, the preset safety threshold is set to 0.5 meters, and the current water level \(H_c\) is measured to be 2 meters. Assume that within a day, the average rainfall in the foundation pit is R = 0.5mm / h, and the hourly evaporation rate is E = 1mm / h in the absence of rainfall. Knowing that the capacity of \(V_b\) is 5000 cubic meters, substitute it into the formula to get W. Assuming that the calculation results show that the current remaining safe water volume W is small, that is, the (\(R / E\)) value is greater than 0.66, then the system will reduce the opening of the control valve to reduce the discharge volume. If W is greater than a certain critical value, it may be necessary to increase the opening of the valve to increase the discharge volume to ensure safety.

[0113] Next, the description of "wherein the operation of adjusting the opening size of the control valve further" involves multiple specific decision logics to adapt to changing environments and needs. First, the sensor of the monitoring system continuously measures the rainfall intensity I and compares it with the threshold value \(I_t=H_{\text{max}}\times C / T\). This formula calculates that the threshold value is related to the maximum expected water height \(H_{\text{max}}\), the cycle period T (hours), and the preset valve opening amount C. In this way, the basic premise for the need for opening adjustment is determined.

[0114] For example, if the maximum expected water height \(H_{\text{max}}=50\)mm, the preset opening volume is C=2mm / hour and the drainage cycle T is 6 hours, then the threshold \(I_t\) can be obtained by the following formula: \(I_t=50\times2\, / \,6\approx 16.67\)mm / hour. This means that when the measured rainfall intensity exceeds about 16.67mm / hour, the control system determines that the rainfall is too strong and automatically takes measures to reduce the possibility of water flowing into the foundation pit.

[0115] Then, when it is confirmed that the rainfall intensity is higher than the given threshold, the control system automatically reduces the valve opening size. For example, in the above case, assuming that the rainfall has indeed increased significantly and has exceeded the set threshold \(I>16.67\) mm / hour, the control system will reduce the original valve opening by a certain value, recorded as ΔC1; for example, from the original preset size to C' (C-ΔC1) by 0.5mm to slow down the water inflow rate. This action helps to keep the water level in the foundation pit within the expected safety range and prevent the risk of excessive water accumulation.

[0116] In addition, according to the requirements of the time period, when within the specified drainage time, the opening degree of the valve should be adjusted back to the pre-specified state, that is, the valve opening is restored to the initial set width C; otherwise, during the non-drainage period, it needs to be adjusted according to the actual situation so that the opening degree is adjusted to another smaller value ΔC2. If the current time exactly falls within the specified drainage period, the system automatically resets the opening degree of the valve back to C, and if the time does not belong to this stage, corresponding fine-tuning should be made according to actual needs (for example, under the example conditions, the opening degree of the valve can be changed to a value slightly smaller than the original, such as: C - 0.2), so as to ensure the safety and stable handling of water flow problems while not overly restricting drainage.

[0117] Next, describe that "controlling the actual drainage process based on the adjusted control valve opening size further includes the following specific operations:

[0118] * Measure the real-time rainfall accumulation amount Ar in the deep foundation pit, and set the maximum allowable cumulative threshold Ar,max and the minimum allowable accumulation threshold Ar,min; this means that the system first needs to install a water level sensor to detect the actual water level in the foundation pit. At the same time, in order to maintain the safe and stable operation of the foundation pit, appropriate deepest water volume and shallowest water volume standards also need to be preset. Assume that the minimum allowable rainfall accumulation depth in the foundation pit is 0.3 meters as the minimum cumulative threshold, and the maximum cumulative depth is 2.0 meters as the highest allowable threshold;

[0119] * Determine whether Ar is greater than or equal to the minimum accumulation threshold Ar,min; this is to avoid the situation where the automatic drainage system is still started when the rainwater accumulation is insufficient, resulting in the pump running empty and affecting the normal operation of the equipment. Continuing with the previous data example, if the real-time monitored water accumulation depth is 0.28 meters < the minimum allowable water level depth, then the system does not need to start the drainage treatment at this time;

[0120] * Stop the drainage operation when the real-time measured rainfall accumulation amount \(A_r < A_r,\min + C\times I / V\times H_b + R_d\); where C, I, V, and \(H_b\) are the cross-sectional area coefficient of the foundation pit, the current instantaneous rainfall rate value, the average volume of the bottom surface of the foundation pit, and the real-time drainage efficiency respectively. Here, the formula is used to ensure that when the precipitation rate is small and most of the accumulated water has been drained, the pump is not over-operated to reduce resource consumption. Further analyze with the previous example situation. Suppose the current rainfall speed I = 2 mm / h at this time, and the real-time抽空 rate of the pump \(Rd = 20m^3 / h\). The result calculated based on the defined formula is: 2 * 2mm / 3600s * (6 * 30 * 2) / 10 = 0.267m. If the result obtained from the actual measurement of the water meter is lower than the above number, then the system should automatically stop pumping.

[0121] * In other cases, drainage is maintained to ensure that the amount of accumulated water A_r is within the predetermined range to avoid excessively high or low water levels; if the accumulated rainfall exceeds the minimum requirement but is not close to the maximum limit, that is, \(A_{min}<=A_r<=A_{max}\), it is necessary to ensure that the water pump is turned on to keep the water level at a reasonable height.

[0122] Next, describe the "further specific steps to be taken when adjusting the water level control strategy based on current hydrological conditions."

[0123] 1. First, it is necessary to determine whether the continuous rainfall duration (N) is greater than or equal to the preset rainy season critical hours (N_s) and whether the formula \(A_r>=A_r,\max+C\times I / (1H_d)R_d\) satisfies the establishment conditions, where \(A_r\) represents the remaining water storage capacity of the foundation pit, \(A_r,\max\) represents the maximum instantaneous precipitation that the foundation pit can accept in the non-flood season, C is the coefficient of the change in the foundation pit water depth and the water storage increment, \(I\) represents the actual rainfall intensity per unit time, \(H_d\) represents the actual change value of the actual water level relative to the design water level of the foundation pit, and \(R_d\) is the rate of change of the foundation pit water level. For example, if there is continuous rainfall every day during a certain period of the rainy season, the number of rainfall days has exceeded the preset rainy season critical value N_s, and according to the current rainfall intensity and water level drop rate, the remaining water storage capacity of the foundation pit exceeds the warning setting threshold, that is, the water storage in the foundation pit is about to overflow. Under such conditions, the control system needs to raise the lower water level threshold to increase water pumping, thereby reducing the internal water volume and ensuring system stability.

[0124] 2. If the precipitation has stopped and the conditions are met, the system needs to recalculate and set new upper and lower limits of the actual water level. This stage is achieved based on the actual drainage efficiency η of the foundation pit and the preset emptying cycle τ. The purpose is to gradually reduce the water pumping intensity in the foundation pit by appropriately reducing the frequency or number of pumps opened so as to restore it to the usual level. For example, when the weather turns clear and the accumulated water begins to gradually drain, we can infer how many hours it will take for the water body to return to the standard line based on the current emptying time and efficiency of the foundation pit, and slowly reduce the upper and lower limits of the water level.

[0125] 3. When it is not in the rainy season, it is necessary to further determine the number of consecutive non-precipitation days N. If N is lower than the preset minimum non-rainy season critical hours N_min, that is, when the precipitation situation reaches a certain standard, based on the foundation pit water level changes and drainage data over a period of time, if the drainage capacity corresponding to the current rainless period is less than or equal to the rainfall dilution time, then the various water level control settings in the control system can be restored to the initial state value and the normal operating mode can be restored. According to the example, after a long period without rain, it is found that the current water body allows drainage time is not enough to dilute the impact of the recent average rainfall on the foundation pit water capacity. At this time, the control system should be adjusted to restore to normal settings to avoid unnecessary energy waste.

[0126] The "deep foundation pit drainage system and use method" of the present invention includes a series of steps, aiming to solve the problem that deep foundation pits are prone to groundwater infiltration in high water level areas, thereby ensuring construction safety and smooth progress of the project. First, "step a1" mentions that groundwater can be effectively collected by arranging annular precipitation wells along the periphery of the deep foundation pit. The annular design of this precipitation well can cover as large an area as possible, ensuring that as much groundwater as possible can be intercepted in time, and in this way reduces the height of the groundwater surface in the pit, effectively preventing the impact of groundwater rise on the stability of the foundation pit. Subsequently, "step a2" introduces how to construct a drainage network inside the deep foundation pit to further ensure the drainage effect. This design not only deals with the accumulation of water caused by precipitation, but also takes into account the water that penetrates inward through the rock and soil structure, ensuring that the working environment in the deep foundation pit always maintains a suitable working state. Next, "step a3" points out the need to start the drainage pumping equipment in a timely manner according to the preset water level control strategy. This strategy ensures that groundwater can be discharged in time while maintaining safety, effectively controls the hydrological dynamics, and avoids the risks and inconveniences caused by fluctuations in the foundation pit water level. Finally, "step a4" focuses on the dynamic operation monitoring mechanism of the entire system. With the help of automated monitoring technology, the hydrological environment inside and outside the foundation pit is continuously tracked and analyzed, and the system parameters are adjusted when necessary, so that the device can always be in the most optimized operating state and ensure the safety, stability and engineering quality of the foundation pit. Overall, this drainage plan adopts multi-level comprehensive measures to ensure that groundwater is reasonably controlled and effectively removed. Through the form of circular layout and internal and external coordination, it can prevent groundwater intrusion while effectively managing the collected or accumulated groundwater, ultimately achieving the goal of safe construction. This technology plays a key role in improving water resource management in deep foundation pit construction.

[0127] The methods, programs, systems, devices, etc. of the embodiments of the present invention may be executed or implemented in a single or multiple networked computers, or may be practiced in a distributed computing environment. In the embodiments of this specification, in these distributed computing environments, tasks may be performed by remote processing devices connected via a communication network.

[0128] Those skilled in the art should understand that the embodiments of the present specification may be provided as methods, systems or computer program products. Therefore, those skilled in the art may imagine that the functional modules / units or controllers and related method steps described in the above embodiments may be implemented in software, hardware or a combination of software / hardware.

[0129] Unless explicitly stated, the actions or steps of the methods, programs, and embodiments of the present invention do not have to be performed in a specific order and can still achieve the desired results. In some implementations, multitasking and parallel processing are also possible or may be advantageous.

[0130] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A deep foundation pit drainage system and a method of use, characterized in that: include: Step a1, arranging annular precipitation wells around the deep foundation pit, collecting groundwater through the annular precipitation wells and lowering the groundwater level; Step a2, establishing a drainage network inside the foundation pit to remove surface precipitation and seepage; Step a3, starting the drainage pumping equipment to drain the collected groundwater out of the foundation pit based on the preset water level control strategy; Step a4, monitor the hydrological changes inside and outside the deep foundation pit and adjust the operating parameters of the precipitation well and drainage system in time to maintain a safe water level in the deep foundation pit.

2. A deep foundation pit drainage system and use method according to claim 1, characterized in that: The step a1 specifically includes: A1 Select appropriate spacing to arrange drainage well points according to the deep foundation pit design parameters; A1.2 After the drilling reaches the predetermined depth, install the water filter pipe section with good permeability; A1.3 Wrap the outside of the filter pipe section with a filter material filling layer to increase drainage capacity; A1.4 Arrange each precipitation well in a circular pattern and ensure a continuous drainage system; A1.5 Install connecting pipes to ensure connectivity between the precipitation well and the main pumping system.

3. A deep foundation pit drainage system and use method according to claim 1, characterized in that: The step a2 specifically includes: A1 Design the layout of drainage ditches in the foundation pit to ensure that water can flow smoothly to the collection point; A2.2 Lay waterproof isolation materials in appropriate areas at the bottom of the foundation pit to prevent underwater penetration; A2.3 Establish seepage water interception structures to prevent water intrusion from surrounding soil layers; A2.4 Arrange a sump and install a submersible pump in it to remove the collected water; A2.5 adopts anti-siltation design to ensure that the drainage ditches in the foundation pit are unobstructed.

4. A deep foundation pit drainage system and use method according to claim 1, characterized in that: The step a3 specifically includes: A1 sets the initial control water level value and alarm value as operation guidance parameters; A3.2 Start the pre-installed drainage pumps to drain the groundwater; A3.3 Arrange technicians to adjust the pump group to achieve fine control of water level; A3.4 Operate the automatic water level measuring device to continuously record the real-time groundwater conditions; A3.5 Use intelligent control systems to monitor drainage rates and make appropriate adjustments.

5. A deep foundation pit drainage system and use method according to claim 1, characterized in that: The step a4 specifically includes: A1 deploys environmental monitoring stations to monitor the changing trends of the internal and external environment of the deep foundation pit; A4.2 is equipped with a remote water level sensor to continuously obtain the current underground level value; A4.3 Analyze the impact of deep foundation pit excavation progress on the groundwater system; A4.4 Adjust the intensity of precipitation well operations based on actual water level changes to replenish water sources in a timely manner; A4.5 Implement preventive maintenance plans to reduce the chance of failure and ensure drainage efficiency.

6. A deep foundation pit drainage system and use method according to claim 1, characterized in that: The step a3 of starting the drainage pumping equipment to discharge the collected groundwater from the foundation pit based on the preset water level control strategy includes: Start drainage according to the real-time water level H in the deep foundation pit monitored; Set the safe minimum water level H_min and safe maximum water level H_max as reference benchmarks; When the real-time water level H is less than H_min, the drainage pump stops working and enters standby mode; When the real-time water level H reaches or exceeds H_max and is lower than the warning water level H_w, the drainage pump is automatically started to drain water until the water level drops below H_max.

7. A deep foundation pit drainage system and use method according to claim 1, characterized in that: Further defining the preset water level control strategy includes the following operations: Adjust the control valve opening size C according to the changes in the average rainfall R and evaporation E in the foundation pit; Determine the current water level H_c and calculate the remaining safe water volume W based on H_c; If \(H_c\) is greater than the preset minimum safety water level plus the preset safety threshold \(\Delta H\), \(W\) is calculated according to the formula: \(W = V_b\times(1R / E)\), where \(V_b\) is the deep foundation pit capacity; Determine whether to increase or decrease the drainage volume according to \(W\).

8. A deep foundation pit drainage system and use method according to claim 7, characterized in that: Among them, the operation of adjusting the opening size of the control valve further includes: Monitor the rainfall intensity \(I\) and judge whether it is greater than the threshold value \(I_t = H_{\text{max}}\times C / T\), where \(T\) is the cycle duration in hours; If the rainfall intensity \(I\) is greater than this threshold value, reduce the valve opening size \(\Delta C1\); If the current time falls within the drainage cycle, increase the opening size to the initial preset standard \(C\); Otherwise, fine-tune the current opening size of the valve to \(\Delta C2\) according to the hydrological situation.

9. A deep foundation pit drainage system and use method according to claim 8, characterized in that: Controlling the actual drainage process based on the adjusted control valve opening size further includes the following specific operations: Measure the real-time rainfall accumulation amount \(A_r\) in the deep foundation pit, and set the maximum allowable accumulation threshold \(A_{r,\max}\) and the minimum allowable accumulation threshold \(A_{r,\min}\); Judge whether \(A_r\geq A_{r,\min}\) holds; When the real-time measured rainfall accumulation amount \(A_r < A_{r,\min}C\times I / V\times H_b + R_d\), stop the drainage operation; here \(R_d\) represents the drainage rate of the drainage pump; In other cases, maintain drainage to ensure that the accumulated water volume \(A_r\) is within a predetermined range to avoid too high or too low water levels.

10. A deep foundation pit drainage system and use method according to claim 5, characterized in that: When adjusting the water level control strategy according to the current hydrological conditions, the specific steps further executed include: When the continuous rainfall hours \(N\) is greater than or equal to the preset rainy season critical hours \(N_s\) and \(A_r\geq A_{r,\max}+C\times I / (1H_d)R_d\), where \(H_d\) is the actual water level floating rate, then increase the lower water level threshold to reduce the water volume; After the rainfall stops, adjust the upper and lower limits of the actual water level according to the drainage efficiency \(\eta\) and the preset drainage recovery time \(\tau\) to restore the normal level; In the non-rainy season stage, if \(N\) is less than the minimum non-rainy season hours \(N_{\min}\) and \(N < N_{\min}(V_h / (R_{\text{average}}\eta))\), then restore the water level control to the normal state; Among them, \(R_{\text{average}}\) represents the average rainfall over a long period of time, and \(V_h\) is the foundation pit depth.

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