Deep foundation pit dewatering and drainage construction method based on water level control and control system

Abstract

The invention provides a deep foundation pit dewatering and drainage construction method based on water level control and a control system.The deep foundation pit is provided with an upper berm, a lower berm and an excavation base face, dewatering tube wells are arranged on the excavation face and the upper berm, and first water pumps of the dewatering tube wells are used for water pumping and drainage; an inverted filter layer is arranged on the slope surface of a lower berm and an excavation base plane, dewatering and drainage are conducted in cooperation with a slope toe drainage ditch and a water collecting well, water level sensors in a river and the water collecting well are used for collecting the water level in real time, optimization decision making is conducted in combination with the water level, then a first water pump is driven to conduct power adjustment, and the dewatering and drainage construction efficiency is improved through a corresponding control decision making method.

Description

Technical Field

[0001] The present invention relates to the field of foundation treatment, and particularly relates to a construction method and control system for dewatering of deep foundation pits based on water level control. Background Technique

[0002] The excavation of foundation pits is an important link in construction engineering and one of the key projects and parts. During the excavation of foundation pits, it is necessary to ensure the stability of the foundation pit slope and, through reasonable dewatering means, lower the groundwater level of the foundation pit to ensure that problems such as quicksand and piping do not occur during the excavation and construction of the foundation pit. For the excavation of foundation pits near the outer river water level, since the water level of the outer river may change, it may lead to different changes in the groundwater level. If a fixed single-mode dewatering is adopted, it may not be possible to effectively ensure the control of the groundwater level during the construction of the foundation pit.

[0003] For the control of deep foundation pit groundwater, methods such as theoretical calculation and simulation calculation can be used at present. However, these calculation results rely on the original measurement data, and there are certain errors between these geological data, calculation parameters, etc. and the actual situation, resulting in the inability to guide actual construction only relying on the theoretical calculation results. Therefore, it is necessary to conduct intelligent monitoring and optimization adjustment during actual construction to improve the comprehensive efficiency of dewatering. Summary of the Invention

[0004] In view of the problems of the prior art, the present invention provides a construction method and control system for dewatering of deep foundation pits based on water level control, which improves the dewatering efficiency of deep foundation pit excavation construction through intelligent decision-making and reduces energy consumption waste.

[0005] The present invention provides a construction method for dewatering of deep foundation pits based on water level control. The deep foundation pit is adjacent to a river and dewatering is carried out during the excavation process. The characteristics are as follows: The deep foundation pit is excavated in layers, with an upper berm, a lower berm, and an excavation base surface set. Among them, the layer from the lower berm to the ground is a loam layer, and the layer below the lower berm is a fine sand layer. Dewatering wells are set on both the excavation surface and the upper berm. A first water pump is set in the dewatering well, and the power of the first water pump supports adjustment. An anti-filter layer is set on the slope between the lower berm and the excavation base surface, and a toe drain is set at the bottom of the anti-filter layer. The toe drain is connected to a sump, and a second water pump is set in the sump. Water level sensors are respectively set in the river and the sump to obtain the river water level Hs1 and the sump water level Hs2 respectively. The construction method includes the following steps: S1: With the goal of controlling the water level at the sump water level Hs2min, through simulation calculation, the power P of the first water pump under different river water levels Hs1 is obtained, and an Hs1-P relationship table is obtained, where the power range of the first water pump covers the power values in the Hs1-P relationship table; S2: After the excavation of the deep foundation pit is completed, the river water level Hs1s is monitored in real time, and the Hs1-P relationship table is searched to obtain the power Ps of the first pump, and the first pump is controlled to operate according to the power Ps; the water level Hs2 of the sump is monitored in real time; S21: When the water level of the sump is higher than Hs2min, gradually increase the power Ps of the first pump until the water level of the sump is controlled at Hs2min minus the set water level; S22: When the water level of the sump is lower than Hs2min minus the set water level, gradually reduce the power Ps of the first pump until the water level of the sump is controlled at Hs2min minus the set water level; S23: When the water level of the sump is stable at Hs2min minus the set water level, record the river water level Hs10 and the power Ps0 of the first pump at this time; S24: Replace the values in the Hs1-P relationship table with Hs10 and Ps0 to obtain a new Hs1-P relationship table; S3: When the real-time monitored river water level Hs1s changes, call the Hs1-P relationship table updated in step S2 and execute step S2.

[0006] Preferably, the water level sensors in the river and the sump are both submersible water level gauges.

[0007] Preferably, the power adjustment of the first pump is stepwise, and the power adjustment amplitude each time is 5% - 10% of the rated power.

[0008] Preferably, a water retaining embankment is arranged on the excavation surface, and the cross-section of the water retaining embankment is trapezoidal. The water retaining embankment is used to prevent external rainwater from flowing into the foundation pit during heavy rainfall.

[0009] A control system applying the above-mentioned deep foundation pit dewatering construction method based on water level control, characterized in that: the control system includes a control module, the control module is connected to the water level sensors in the river and the sump for obtaining the real-time water levels of the river and the sump, a data storage module is arranged inside the control module for storing the Hs1-P relationship table, the control module is connected to the first pump for sending a power adjustment signal to the first pump according to the above method, and the power adjustment signal includes a power value given or a power increase or power decrease signal.

[0010] Preferably, the control module is a single-chip microcomputer, and a data update module is further arranged inside the control module. The data update module is used to obtain the river water level, the water level of the sump and the power of the first pump, and can update the data of the Hs1-P relationship table stored in the data storage module according to the river water level, the water level of the sump and the power of the first pump.

[0011] The working principle of the present invention is as follows: For foundation pit excavation, it is necessary to reasonably control the groundwater level. By cooperating with a pump to drain water through a dewatering pipe well, a circular closed funnel-shaped water level control curve can be formed. The dewatering pipe wells need to be arranged in a circular closed manner. Based on obtaining the water-containing characteristics and seepage characteristics of the geological layer, the variation law of the seepage field can be obtained through simulation calculation. Based on determining the number and position of the dewatering pipe wells, the corresponding groundwater level control conditions under different pumping and drainage powers can be simulated through simulation (such as software like ANSYS or flas3D). On the basis of meeting the groundwater level control, the corresponding pump power can be obtained. For different river water levels, a set of pump powers can be obtained through simulation, thereby generating a theoretically relationship table between the river water level and the first pump power. This table is obtained through theoretical simulation calculation and may deviate from the actual situation. The main reason is that the water-containing characteristics and seepage characteristics of the geological layer may be different from the actual situation.

[0012] During the dewatering operation, if the water level in the sump (which reflects the groundwater level control situation) is too high, it indicates that the power of the first pump is too small. At this time, the pump power should be increased to control the groundwater level. If the water level is too low, it indicates that the pump power is too large, and the pump power should be reduced. If the water level in the sump is stable at a reasonable level, it indicates that the pump power is appropriate and meets the groundwater level control. At this time, record the river water level and the power of the first pump, and update the relationship table obtained through theoretical calculation. Through data update feedback, a new relationship table can be generated, which can reflect the actual situation on site to improve the efficiency of dewatering construction.

[0013] This method obtains the relationship table between the river water level and the first pump through theoretical simulation calculation, which can effectively guide the pump dewatering operation and avoid blindness in operation. Through effective adjustment feedback using measured data, reasonable and effective control of the groundwater level can be achieved. Using the regulation results, the relationship table between the river water level and the first pump is updated in real time, thereby guiding the regulation of the first pump next time.

[0014] The advantages of the present invention are as follows: (1) The first water pump with adjustable power is adopted, which can adjust the power according to different outer river water levels, avoid waste of energy consumption, and improve the dewatering efficiency. The first water pump is remotely and intelligently controlled to reduce manual input; (2) The water level sensors are used to collect the river water level and the water level in the sump in real time, so as to master the current groundwater situation in real time and adjust the dewatering working conditions; (3) The filter layer is set in the fine sand layer to ensure the precipitation of water without generating quicksand piping, protect the stability of the slope, and reduce the occurrence of slope instability; (4) Use simulation analysis and calculation to achieve intelligent control of the pump unit. By using the feedback of measured data and updating the simulation calculation data, it can better conform to the actual working conditions on site, thereby ensuring the construction efficiency and management performance of dewatering. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is the construction profile of the present invention; Figure 2 It is the flow chart of the construction method; Figure 3 It is the schematic connection diagram of the control system.

[0015] DETAILED IMPLEMENTATION MANNER: The following is a specific explanation of the content defined by the present invention.

[0016] The present invention provides a dewatering construction method for deep foundation pits based on water level control. The deep foundation pit is adjacent to a river, and dewatering is carried out during the excavation process. It is characterized in that: the deep foundation pit is excavated in layers, with an upper berm 1, a lower berm 2, and an excavation base surface 3 set. Among them, the soil layer from the lower berm 2 to the ground is the loam layer, and the fine sand layer is below the lower berm 2. Dewatering wells 5 are set on both the excavation surface 4 and the upper berm 1. A first water pump is set in the dewatering well 5, and the power of the first water pump supports adjustment. An anti-filter layer 6 is set on the slope between the lower berm 2 and the excavation base surface 3. A toe drain is set at the bottom of the anti-filter layer 6, and the toe drain is connected to a sump 8. A second water pump is set in the sump 8. Water level sensors 9 are respectively set in the river and the sump 8 to respectively obtain the river water level Hs1 and the sump 8 water level Hs2. The construction method includes the following steps: S1: With the goal of controlling the water level at the sump 8 water level Hs2min, through simulation calculation, the power P of the first water pump under different river water levels Hs1 is obtained, and an Hs1-P relationship table is obtained, where the power range of the first water pump covers the power values in the Hs1-P relationship table; S2: After the deep foundation pit is excavated, the river water level Hs1s is monitored in real time, and the Hs1-P relationship table is searched to obtain the power Ps of the first pump unit 7, and control the first pump unit 7 to operate according to the power Ps; the sump 8 water level Hs2 is monitored in real time; S21: When the sump 8 water level is higher than Hs2min, gradually increase the power Ps of the first pump unit 7 until the sump 8 water level is controlled at Hs2min minus the set water level; S22: When the sump 8 water level is lower than Hs2min minus the set water level, gradually reduce the power Ps of the first pump unit 7 until the sump 8 water level is controlled at Hs2min minus the set water level; S23: When the sump 8 water level is stable at Hs2min minus the set water level, record the river water level Hs10 and the power Ps0 of the first pump unit 7 at this time; S24: Replace the values in the Hs1-P relationship table with Hs10 and Ps0 to obtain a new Hs1-P relationship table; S3: When the real-time monitored river water level Hs1s changes, call the Hs1-P relationship table updated through step S2 and execute step S2.

[0017] A second pump is also set in the sump. In case of an emergency, if the water level in the sump is too high, the second pump is started for pumping to prevent the water level from being too high and affecting the construction of the excavation base surface.

[0018] The Hs1-P relationship table should cover the maximum water level and the minimum water level that the river may have. For the values falling within the Hs1-P relationship table, the corresponding P value can be obtained according to the difference (preferably linear interpolation). For example, for the water level Hs1r, the two adjacent water level values are Hs1rm and Hs1rn (Hs1rn > Hs1r > Hs1rm), and the corresponding P values are Psm and Psr respectively. Then, according to the linear interpolation, the power value corresponding to the water level Hs1r can be calculated as follows: P = Psm + (Psr - Psm) / (Hs1rn - Hs1rm) × (Hs1r - Hs1rm) The set water level can be selected as 5 cm. In S21 and S22, the basis for controlling the water level of the sump 8 at Hs2min minus the set water level is that the water level of the sump 8 is within the range between Hs2min and Hs2min minus the set water level within the set time. The set time can be selected as 5 min.

[0019] In S23, when it is stable at Hs2min minus the set water level, the judgment basis is that the water level of the sump 8 is within the range between Hs2min and Hs2min minus the set water level within the set time. The set time can be selected as 5 min.

[0020] Preferably, the adjustment of the power of the first pump 7 can be related to the increasing speed of the water level of the sump 8. If the increasing speed is large, the increasing rate of the first pump 7 is fast; if the increasing speed is small, the increasing rate of the first pump 7 is small, and vice versa. Considering that the river water level generally does not change suddenly, only by controlling the water level of the sump 8 can it be achieved. If the water level is higher than Hs2min, it means that the power is small at this time and the groundwater level cannot be effectively reduced. If the water level is lower than Hs2min minus the set water level, it means that the power of the first pump 7 is too large and there is a situation of energy consumption waste.

[0021] Using the adjusted data to replace the original relationship table can more realistically conform to the situation. For the update of the data relationship table, if there is a corresponding water level Hs1, then replace and update it; if not, select interpolation into the relationship table.

[0022] The excavation depth of the deep foundation pit is not less than 10m. The deep foundation pit is excavated in layers. Due to the design of the filter layer 6, when the groundwater level is high, water in the fine sand layer will be precipitated through the filter layer 6 without bringing out the sand, effectively avoiding the occurrence of quicksand pipe phenomenon.

[0023] Preferably, the water level sensors 9 in the river and the water collection well 8 are immersion type water level gauges, the measuring range of which meets the water level measurement requirements, and the output signal thereof is a 485 signal.

[0024] Preferably, the power regulation of the first pump machine 7 is step-by-step, and the power adjustment range of each time is 5% to 10% of the rated power. The power regulation of the first pump machine 7 can be adjusted by a frequency converter. The first pump machine 7 should also support power setting, that is, after setting a certain power, the first pump machine 7 can operate according to the set power.

[0025] Preferably, a water retaining earth embankment 10 is provided on the excavation surface 4. The cross section of the water retaining earth embankment 10 is trapezoidal. The water retaining earth embankment 10 is used to prevent external rainwater from flowing into the foundation pit during heavy rainfall periods.

[0026] A control system that applies the above-mentioned deep foundation pit dewatering construction method based on water level control, characterized in that: the control system includes a control module 11, the control module 11 is connected to the water level sensor 9 in the river and the water collection well 8, and is used to obtain the real-time water level of the river and the water collection well 8. The control module 11 is internally provided with a data storage module for storing the Hs1-P relationship table. The control module 11 is connected to the first pump 7 and is used to send a power regulation signal to the first pump 7 according to the above-mentioned method, and the power regulation signal includes a power value given or a power increase or power decrease signal.

[0027] The control module 11 should have calculation, analysis and storage functions. Preferably, the control module 11 is a single-chip microcomputer. The control module 11 is also provided with a data update module. The data update module is used to obtain the river water level, the water level of the collection well 8 and the power of the first pump 7, and can update the Hs1-P relationship table stored in the data storage module according to the river water level, the water level of the collection well 8 and the power of the first pump 7. The data update includes data replacement or data insertion.

[0028] Taking the drainage operation of a deep foundation pit as an example, before the operation, the seepage field of the deep foundation pit was simulated through simulation. According to the maximum number of designed two-layer drainage wells, the power value of the first pump corresponding to different river water levels was obtained. This power value can ensure that the groundwater level meets the construction requirements.

[0029] For example, in the obtained relationship table, the power value corresponding to a river water level of 50.1 m is 670 kW, and the power value corresponding to a river water level of 50.2 m is 710 kW. After excavation, when the real-time monitored river water level is 50.15 m, the power value of the first pump is calculated to be 690 kW.

[0030] The first pump operates at this power value and it is found that the water level in the sump is on the high side (it should be controlled below 0.5 m according to the design). By increasing the pump power (increasing by 5 kW each time), the water level in the sump then drops and stabilizes at 0.48 m. At this time, the power of the first pump is 695 kW. Record 50.15 m - 695 kW and interpolate it in the original relationship table (add this row record to the original relationship table).

[0031] The above embodiments are only the preferred embodiments of the present invention. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. The protection scope of the present invention also includes equivalent technical means that can be conceived by those skilled in the art according to the concept of the present invention.

Claims

1. A construction method for dewatering in deep foundation pits based on water level control. The deep foundation pit is adjacent to a river, and dewatering is carried out during the excavation process. It is characterized in that: The deep foundation pit is excavated in layers, with an upper berm, a lower berm and an excavation base surface. The soil layer from the lower berm to the ground is a loam layer, and the layer below the lower berm is a fine sand layer. Dewatering wells are arranged on both the excavation surface and the upper berm. A first water pump is arranged in the dewatering well, and the power of the first water pump supports adjustment. An anti-filter layer is arranged on the slope between the lower berm and the excavation base surface, and a toe drain is arranged at the bottom of the anti-filter layer. The toe drain is connected to a sump, and a second water pump is arranged in the sump. Water level sensors are respectively arranged in the river and the sump to obtain the river water level Hs1 and the sump water level Hs2. The construction method includes the following steps: S1: Aiming at controlling the water level at the sump water level Hs2min, through simulation calculation, the power P of the first water pump under different river water levels Hs1 is obtained, and an Hs1-P relationship table is obtained, where the power range of the first water pump covers the power values in the Hs1-P relationship table; S2: After the deep foundation pit is excavated, the river water level Hs1s is monitored in real time, and the Hs1-P relationship table is searched to obtain the power Ps of the first pump, and the first pump is controlled to operate according to the power Ps; the sump water level Hs2 is monitored in real time; S21: When the sump water level is higher than Hs2min, gradually increase the power Ps of the first pump until the sump water level is controlled at Hs2min minus the set water level; S22: When the sump water level is lower than Hs2min minus the set water level, gradually reduce the power Ps of the first pump until the sump water level is controlled at Hs2min minus the set water level; S23: When the sump water level is stable at Hs2min minus the set water level, record the river water level Hs10 and the power Ps0 of the first pump at this time; S24: Replace the values in the Hs1-P relationship table with Hs10 and Ps0 to obtain a new Hs1-P relationship table; S3: When the real-time monitored river water level Hs1s changes, call the Hs1-P relationship table updated in step S2 and execute step S2.

2. The construction method for dewatering of deep foundation pits based on water level control according to claim 1, wherein: The water level sensors in the river and the sump are both submersible water level gauges.

3. The construction method for dewatering of deep foundation pit based on water level control according to claim 1, characterized in that: The power adjustment of the first pump is stepless, and the amplitude of each power adjustment is 5% - 10% of the rated power.

4. The construction method for dewatering of deep foundation pits based on water level control according to claim 1, characterized in that: A water retaining embankment is arranged on the excavation surface, and the cross-section of the water retaining embankment is trapezoidal. The water retaining embankment is used to prevent external rainwater from flowing into the foundation pit during heavy rainfall.

5. A control system for applying the construction method of dewatering in deep foundation pits based on water level control according to any one of claims 1-4, characterized in that: The control system includes a control module. The control module is connected to the water level sensors in the river and the sump for obtaining the real-time water levels of the river and the sump. A data storage module is arranged inside the control module for storing the Hs1-P relationship table. The control module is connected to the first pump for sending a power adjustment signal to the first pump according to the method of any one of claims 1-4. The power adjustment signal includes a power value given signal or a power increase or power decrease signal.

6. A control system as claimed in claim 5, characterized in that: The control module is a single-chip microcomputer, and a data update module is further arranged in the control module. The data update module is used to obtain the river water level, the sump water level, and the power of the first pump, and can update the data in the Hs1-P relationship table stored in the data storage module according to the river water level, the sump water level, and the power of the first pump.

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