Precipitation system and precipitation operation method for deep foundation pit close to building

Abstract

According to the dewatering system for the deep foundation pit close to the building and the dewatering operation method, a floor type waterproof curtain is arranged outside the side, adjacent to the building, of an underground diaphragm wall on the periphery of the deep foundation pit, a dewatering influence area outside the foundation pit is isolated from the building, and the influence on the building in the dewatering process of the deep foundation pit is reduced; a plurality of pressurized recharge wells are arranged between the underground diaphragm wall and the waterproof curtain, and a plurality of normal-pressure recharge wells are arranged between the waterproof curtain and the building; in the construction process of the deep foundation pit, rainfall in the foundation pit is recharged to a confined water layer between an underground diaphragm wall and a waterproof curtain through a pressurizing recharge well and is recharged to a phreatic water layer and the confined water layer of the area where the building is located through a normal-pressure recharge well, and the pore water pressure in the phreatic water layer and the water head pressure in the confined water layer of the area where the building is located are maintained; the influence of deep foundation pit dewatering on building settlement is improved; as the floor type waterproof curtain and the underground diaphragm wall are separated and are short, the floor type waterproof curtain and the underground diaphragm wall can be constructed at the same time, and the construction period and the engineering cost of the deep foundation pit dewatering engineering are greatly shortened.

Description

Technical Field

[0001] The invention relates to the technical field of deep foundation pit construction, and in particular to a dewatering system and a dewatering operation method for a deep foundation pit adjacent to a building. Background Art

[0002] With the increasing construction of domestic subways, high-rise buildings and underground parking lots, the excavation depth of deep foundation pits has developed from several meters to 20-30 meters. Deep foundation pit construction will inevitably encounter precipitation problems, and deep foundation pit precipitation will inevitably produce horizontal displacement and settlement of the ground, which will pose a threat to the safety of adjacent buildings. Therefore, the "Safety Code for Construction of Building Engineering" clearly stipulates the safe distance between deep foundation pits and adjacent buildings during construction; but under certain special construction conditions, the safety distance between deep foundation pits and adjacent buildings is less than the conditions stipulated in the "Safety Code for Construction of Building Engineering". How to strictly control the horizontal displacement and settlement of the ground during deep foundation pit construction to ensure the safety of adjacent buildings has become a technical problem.

[0003] At present, many domestic universities and design and construction units have conducted extensive research on the problem of ground horizontal displacement and settlement caused by dewatering during deep foundation pit construction, and have also given many deep foundation pit dewatering engineering structures and methods for controlling ground horizontal displacement and settlement during construction. However, the existing engineering structures and control methods all focus on the isolation of groundwater space inside and outside the deep foundation pit and the control of ground horizontal displacement and settlement outside the foundation pit, while there are fewer studies on how to control the range of ground horizontal displacement and settlement outside the foundation pit. Therefore, there is no good method for controlling the settlement of buildings adjacent to deep foundation pits.

[0004] The application number is 202310618508.7 The Chinese invention patent discloses an integrated construction control method for groundwater isolation-sealing-pumping-injection of ultra-deep foundation pits. Aiming at the problem of large depth reduction of high-pressure water in deep foundation pits, the patent adopts ultra-deep large-diameter ultra-high-pressure jet grouting technology to realize the horizontal bottom sealing of deep layers of high-pressure water in deep foundation pits and the structure of bottom-type waterproof curtain dewatering engineering. The comprehensive measures of depressurization in the pit on demand and recharging outside the pit are combined to achieve the technical effect of depressurization of related multi-layered pressure water layers above the deep bottom waterproof layer below the pit bottom to transform into the nature of phreatic water dewatering. Since the technical solution of the patent basically isolates the connection between the groundwater inside and outside the deep foundation pit, the disturbance to the groundwater outside the foundation pit is small during the dewatering process in the foundation pit, and the settlement control effect on the adjacent buildings of the deep foundation pit is relatively good. However, the technical solution of the patent has the problems that the bottom-type waterproof curtain, horizontal bottom sealing and ground-connected wall cannot be constructed at the same time, and the engineering volume is large, resulting in a long construction period and high cost for the deep foundation pit dewatering engineering. Therefore, further improvement is needed to apply it to the dewatering of deep foundation pits adjacent to buildings. Summary of the invention

[0005] In order to overcome the shortcomings of the background technology, the present invention discloses a deep foundation pit dewatering system and a dewatering operation method adjacent to buildings. By setting a water-stop curtain between the deep foundation pit and the adjacent buildings, the dewatering influence area outside the foundation pit is isolated from the buildings, thereby achieving control of the horizontal displacement and settlement range of the ground outside the foundation pit, thereby ensuring the safety of the adjacent buildings during the deep foundation pit construction process, and at the same time achieving the purpose of reducing the long construction period and high cost of the deep foundation pit dewatering project.

[0006] In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical scheme: a deep foundation pit dewatering system adjacent to a building, wherein there are a phreatic layer and a confined water layer underground at the bottom layer of the deep foundation pit, and the depth of the deep foundation pit extends into the confined water layer; a ground-connected wall is arranged around the deep foundation pit, and a water-stop curtain is arranged on the outside of the side adjacent to the ground-connected wall and the building, and the water-stop curtain is a floor-standing water-stop curtain composed of a number of high-pressure rotary jet piles; a number of dewatering wells are arranged on the inner side of the ground-connected wall, a number of pressurized recharge wells are arranged between the ground-connected wall and the water-stop curtain, and a number of normal-pressure recharge wells are arranged between the water-stop curtain and the building; a pressure sensor is arranged in the pressurized recharge well, and a liquid level detection sensor is arranged in the normal-pressure recharge well, and the pressure sensor and the liquid level detection sensor are communicatively connected to the deep foundation pit dewatering monitoring terminal ; The ground-connected wall as a deep foundation pit retaining structure has a high engineering cost. When the depth of the pressurized water layer is deep, the ground-connected wall usually cannot completely cut off the connection between the pressurized water layers inside and outside the deep foundation pit. Therefore, when dewatering the deep foundation pit, it has a greater impact on the adjacent buildings of the deep foundation pit, and the conventional dewatering system cannot ensure the safety of the adjacent buildings during the dewatering process of the deep foundation pit; after setting a ground-type water-stop curtain between the ground-connected wall and the building, the dewatering influence area outside the foundation pit is isolated from the building, so that the horizontal displacement and settlement range of the ground outside the foundation pit are mainly controlled between the water-stop curtain and the deep foundation pit, thereby reducing the impact on the building during the dewatering process of the deep foundation pit; the pressurized recharge well between the ground-connected wall and the water-stop curtain adopts pressurized recharge to prevent horizontal displacement and settlement between the ground-connected wall and the water-stop curtain during the dewatering process of the deep foundation pit. Although pressurized reinjection has the advantage of high efficiency, it will cause reinjection water replenishment cones in the confined water layer of the reinjection area, and increase the pore water pressure in the diving layer, causing local uplift of the ground in the reinjection area. After setting up the floor-standing water curtain, the local uplift of the ground in the reinjection area is completely controlled in the area between the ground-connected wall and the water-stop curtain, thereby avoiding the impact of pressurized reinjection on adjacent buildings. In addition, after setting up the floor-standing water-stop curtain, although the building is isolated from the precipitation-affected area, the water-stop curtain itself has a certain permeability coefficient. At the same time, there is a bypass phenomenon at both ends of the water-stop curtain during precipitation. Therefore, the confined water layer in the area where the building is located still has a certain head drop and the pore water pressure of the diving layer drops. When the water-stop curtain and the building are connected, the water-stop curtain and the building are connected. After setting up a normal pressure recharge well, the above problem can be solved by replenishing water at a normal pressure constant water level; in addition, the floor-standing water-stop curtain, as an underground engineering structure, itself has a high overall structural strength. Even if horizontal displacement and settlement occur in the pressurized recharge area between the ground-connected wall and the water-stop curtain, the floor-standing water-stop curtain itself can improve the horizontal displacement and settlement of the area where the building is located; in the deep foundation pit dewatering system adjacent to the building, the floor-standing water-stop curtain is only set between the ground-connected wall and the building, so the project volume is small, and the floor-standing water-stop curtain (high-pressure rotary jet pile) itself has a low project cost, so the total project cost is low; in addition, the floor-standing water-stop curtain and the ground-connected wall are separate structures, and the two can be constructed simultaneously and in parallel, so the total project period is also shortened.

[0007] Furthermore, the pressurized recharge wells are arranged in groups, and each group of pressurized recharge wells is provided with two pressurized recharge wells, one of which is used as a backup well for pumping and lifting operations to prevent the formation of a precipitation funnel cone in the pressurized water layer when the pressurized recharge well is pumping and lifting water, causing local subsidence.

[0008] Furthermore, a recharge pipe is provided in the pressurized recharge well and the normal pressure recharge well, and filter materials are laid at the bottom of the pipe and the bottom of the borehole. Clay balls, filter materials, plastic spacers, and clay balls are filled in sequence from bottom to top between the pipe wall and the borehole. A pressurized grouting seal is adopted near the pipe mouth to prevent overflow of the pipe mouth during pressurized recharge and inability to maintain the recharge pressure; wherein the plastic spacers and clay balls prevent the sealing grouting from penetrating into the filter materials under the action of pressure during the pressurized grouting seal; the plastic spacers arranged between the filter materials and the clay balls are made of foamed polyethylene, which is cut and made, and its outer diameter is larger than the borehole wall diameter and its inner diameter is smaller than the outer diameter of the recharge pipe. There are a large number of closed air bubbles in the foamed polyethylene, which has good elasticity, and its elasticity is used to form a seal between the pipe wall and the borehole wall; during the pressurized recharge process, when the pressurized recharge well is blocked, the recharge efficiency is reduced, and it is necessary to improve the recharge efficiency. Injection pressure. When the reinjection pressure is adjusted, due to the incompressibility of water, the reinjection pressure adjustment will cause an instantaneous fluctuation and increase in the pressure of the water in the reinjection well. The instantaneous fluctuation and increase in pressure will cause a large change in the groundwater seepage velocity around the reinjection well, causing the solid soil particles that were originally stable to move with the groundwater seepage and be intercepted and retained in the new position, thereby accelerating the clogging speed of the pressurized reinjection well and causing the frequency of water pumping back from the pressurized reinjection well to increase. After adding the plastic spacer, due to the good elasticity of the plastic spacer, it has the function of absorbing and eliminating the instantaneous pressure fluctuation increase, thereby improving the problem of accelerated clogging speed of the pressurized reinjection well caused by the reinjection pressure adjustment. In addition, the plastic spacer has the property of being impermeable, which can improve the problem of clogging of the pressurized reinjection well caused by the solid soil particles in the clay ball that seeps into the reinjection water after being softened by water.

[0009] Furthermore, a sealing end cap is fixedly provided at the top of the recharge pipe, and two pipe interfaces are provided on the sealing end cap, one of which is connected to a recharge water pump through a pipeline, and the other is connected to a negative pressure water pump through a pipeline. When the pressure recharge well works normally, the recharge pressure is controlled by controlling the recharge rate of the recharge water pump; when pumping and lifting, the negative pressure water pump works at a frequency of 2-3Hz for 5-10 minutes, and intermittent negative pressure pumping and lifting is generated in the pressurized recharge well, so that solid particles that are blocked within a range of about 6 cm around the pressurized recharge well flow back into the recharge pipe with the pumping water, and are finally discharged from the pressurized recharge well through the negative pressure water pump; negative pressure pumping and lifting can improve the pumping and lifting efficiency of the pressurized recharge well, shorten the pumping and lifting operation time, and thus minimize the disturbance of the pressurized water in the recharge area caused by pumping and lifting.

[0010] Furthermore, a valve is provided on the sealing end cover; the valve is in a closed state when the pressurized recharge well is operating, and the valve is in a normally open state when the normal pressure recharge well is operating; the valve is opened in the later stage of negative pressure pumping and the negative pressure pump continues to work at a set rate for a certain period of time to completely complete the replacement of water in the pressurized recharge well and reduce the content of solid particles in the recharge water.

[0011] Furthermore, a number of monitoring wells are provided between the ground-connected wall and the water-stop curtain and in the deep foundation pit. Water level measuring instruments are provided in the monitoring wells. The water level measuring instruments are communicatively connected to the deep foundation pit dewatering monitoring terminal.

[0012] Furthermore, a pore water pressure sensor is buried in the submerged layer between the water-stop curtain and the building, and the pore water pressure sensor is communicatively connected to the deep foundation pit dewatering monitoring terminal.

[0013] Furthermore, a tilt sensor is provided on the building, and the tilt sensor is communicatively connected to a deep foundation pit dewatering monitoring terminal.

[0014] A dewatering operation method for a deep foundation pit dewatering system adjacent to a building, 1. During the deep foundation pit dewatering process, the extracted groundwater is used as recharge water after sedimentation and filtration, so as to improve the quality of the recharge water and prolong the blockage time of the pressurized recharge well; 2. Recharge and pumping are carried out simultaneously, and the total recharge rate and the total pumping rate are within the set range of 1.2 times; 3. The pressurized recharge well adopts pressurized recharge, and the recharge rate is controlled by feedback of the measurement result of the water level measuring instrument in the adjacent monitoring well; the maximum pressure of the pressurized recharge is not more than 0.2MPa; 4. The normal pressure recharge well adopts constant water level recharge, and the water level height in the normal pressure recharge well is controlled by feedback of the measurement result of the pore water pressure sensor installed nearby.

[0015] Furthermore, when the pressurized recharge well pressure is greater than the set value of 0.2MPa, negative pressure intermittent pumping and recharging operations must be carried out.

[0016] Due to the adoption of the technical scheme as described above, the present invention has the following beneficial effects: the present invention discloses a deep foundation pit dewatering system and dewatering operation method adjacent to a building, wherein a floor-standing water-stopping curtain is arranged outside the ground-connected wall around the deep foundation pit and the adjacent side of the building, and the dewatering influence area outside the foundation pit is isolated from the building by the floor-standing water-stopping curtain, so as to realize the control of the horizontal displacement and settlement range of the ground outside the foundation pit, and reduce the impact on the building during the dewatering process of the deep foundation pit; a plurality of pressurized reinjection wells are arranged between the ground-connected wall and the water-stopping curtain, and a plurality of normal-pressure reinjection wells are arranged between the water-stopping curtain and the building; during the dewatering process of the deep foundation pit, the water in the foundation pit is dewatered by pressurized water. The pressure recharge well recharges to the confined water layer between the ground-anchored wall and the water-stop curtain, forming a recharge rising cone curtain in the confined water layer. The recharge rising cone curtain further reduces the impact of deep foundation pit dewatering on the confined water layer under the building; at the same time, the dewatering in the foundation pit is also recharged to the phreatic layer and confined water layer in the area where the building is located through the normal pressure recharge well, maintaining the pore water pressure in the phreatic layer and the head pressure in the confined water layer, further improving the impact of deep foundation pit dewatering on the settlement of the building; since the floor-standing water-stop curtain is separated from the ground-anchored wall and is short in length, the two can be constructed at the same time, greatly shortening the construction period and project cost of the deep foundation pit dewatering project. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the plan layout of the deep foundation pit dewatering system near the building; Figure 2 This is a cross-sectional structural diagram of the deep foundation pit dewatering system of the adjacent building; Figure 3 This is a schematic diagram of the cross-sectional structure of a pressurized recharge well; Figure 4 This is a schematic diagram of the cross-sectional structure of a normal pressure recharge well.

[0018] In the figure: 1. Ground-anchored wall; 2. Water-stop curtain; 3. Deep foundation pit; 4. Foundation pit bottom plate; 5. Upper stratum; 6. Phreatic layer; 7. Water-proof layer; 8. Confined water layer; 9. Dewatering well; 10. Pressurized recharge well; 10.1. Clay ball; 10.2. Filter material; 10.3. Plastic spacer; 10.4. Clay ball; 10.5. Sealing grouting; 11. Monitoring well; 12. Normal pressure recharge well; 13. Pore water pressure sensor; 14. Building. DETAILED DESCRIPTION

[0019] The present invention can be explained in detail by the following examples, and the purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0020] See the instruction manual Figure 1-4: A dewatering system for a deep foundation pit adjacent to a building, wherein a phreatic layer 6 and a confined water layer 8 are present in the underground of the bottom layer of the deep foundation pit 3, the deep foundation pit 3 penetrates into the confined water layer 8, and the bottom elevation is -20 meters; a ground-connected wall 1 is arranged around the deep foundation pit, and a building 14 is arranged on one side of the ground-connected wall 1, and the distance is 20 meters (less than 30 meters required by the safety code for construction engineering), and a floor-type water-stopping curtain 2 is arranged 12 meters outside the adjacent side of the ground-connected wall 1 and the building 14, and the floor-type water-stopping curtain 2 is composed of a number of overlapping high-pressure rotary jet piles, the diameter of the high-pressure rotary jet piles is 1200, and the overlapping of adjacent high-pressure rotary jet piles is 400mm; in this embodiment, the water-stopping curtain 2 is provided with inclined surfaces at both ends. The extension section (shortening the length of the construction site) is used to reduce the impact of the circumferential flow at both ends of the water-stop curtain 2 on the building 14 during precipitation. A total of 30 precipitation wells 9 are arranged along the inner side of the ground-connected wall 1 along the periphery (including 12 wells arranged on the side of the ground-connected wall 1 adjacent to the building 14), with an aperture of 700 mm and a pipe diameter of 325 mm. The precipitation well 9 is 5 m away from the ground-connected wall 1, and the distance between adjacent precipitation wells 9 is 10 m. The depth is between 0.5 and 0.7 times the thickness of the confined water layer 8. Eight groups of pressurized recharge wells 10 are arranged between the ground-connected wall 1 and the water-stop curtain 2, each group including two pressurized recharge wells 10 with a distance of 5 m. The eight groups of pressurized recharge wells 10 are staggered with the precipitation wells 9 on the inner side of the ground-connected wall 1. The distance from the water-stop curtain is 5 meters, and the depth is equal to that of the precipitation well 9; the diameter of the pressurized recharge well 10 is 700mm, the inner diameter of the recharge pipe is 325mm, and filter material 10.2 is laid at the bottom of the pipe and the bottom of the borehole. Clay balls 10.1, filter material 10.2, plastic spacers 10.3, and clay balls 10.4 are filled in sequence from bottom to top between the pipe wall and the borehole. The sealing grouting 10.5 is used for pressurized grouting sealing near the pipe mouth. The filling depth of the filter material 10.2 in the pressurized recharge well 10 covers the thickness of the pressure water layer 8; the plastic spacer 10.3 is made of foamed polyethylene, which is made by hand cutting. Its outer diameter is larger than the diameter of the borehole wall, and its inner diameter is smaller than the outer diameter of the recharge pipe. Its elasticity is used to force The sealing is formed between the pipe wall and the borehole wall; a sealing end cap is fixedly arranged at the top of the recharging pipe, and two pipe interfaces are arranged on the sealing end cap, one of which is connected to a recharging water pump through a pipeline, and the other is connected to a negative pressure pump through a pipeline, and a valve is also arranged on the sealing end cap; 6 normal pressure recharging wells 12 are arranged between the water-stop curtain 2 and the building 14, and the normal pressure recharging wells 12 are arranged along the direction of the water-stop curtain 2, and are 4 meters away from the water-stop curtain 2, and the 4 normal pressure recharging wells 12 in the middle are 30 meters apart, and the two at the two ends are 20 meters apart; the structure of the normal pressure recharging well 12 is basically the same as the pressurized recharging well 10, except that the filter material 10 in the normal pressure recharging well 12.2 filling depth covers the thickness of the confined water layer 8 and the phreatic layer 6; a pressure sensor is provided in the pressurized recharge well 10, and a liquid level detection sensor is provided in the normal pressure recharge well 12. The pressure sensor and the liquid level detection sensor are connected to the deep foundation pit dewatering monitoring terminal; 7 monitoring wells 11 are also provided between the ground-connected wall 1 and the water-stop curtain 2 and in the deep foundation pit 3. The monitoring well 11 outside the foundation pit is provided between two adjacent pressurized recharge wells 10, and is 2 meters away from the ground-connected wall 1. A water level measuring instrument is provided in the monitoring well 11, and the water level measuring instrument is connected to the deep foundation pit dewatering monitoring terminal through communication; 3 pore water pressure sensors 13 are also buried in the phreatic layer 6 between the water-stop curtain 2 and the building 14. The pore water pressure sensor 13 is provided near the normal pressure recharge well 12, with a distance of 5 meters and the same depth. The pore water pressure sensor 13 is connected to the deep foundation pit dewatering monitoring terminal through communication;. The building 14 is also provided with a tilt sensor, which is communicatively connected to a deep foundation pit dewatering monitoring terminal for dynamically monitoring the tilt state of the building 14 .

[0021] Dewatering operation method of deep foundation pit dewatering system near buildings: 1. Before the start of deep foundation pit dewatering, a 6-hour stable detection period is set; after 6 hours, the deep foundation pit dewatering monitoring terminal first detects and records the initial water level heights of all monitoring wells 11 and normal pressure recharge wells 12, and the initial pressure values ​​of all pore water pressure sensors 13; 2. During the deep foundation pit dewatering operation, the extracted groundwater can be used as recharge water only after sedimentation and filtration. Therefore, tap water needs to be used as recharge water in the initial stage of recharge; 3. After the dewatering of the deep foundation pit begins, recharging and pumping are carried out simultaneously. Only one of each group of pressurized recharging wells 10 is used for recharging, and the other is used as a backup. The recharging rate of the pressurized recharging well 10 located in the middle is the same as the pumping rate of the dewatering well 9 adjacent to it, and the recharging rate of the pressurized recharging wells 10 located at both ends is higher than the recharging rate of the pressurized recharging well 10 in the middle. The normal pressure recharging well 12 stabilizes its water level by recharging to be 0.5 meters higher than the initial water level. At this time, the water level of the normal pressure recharging well 12 is controlled by the feedback of the measured value of the water level measuring instrument, and the ratio of the total recharging rate to the total pumping rate is set within 1.2 times. The recharging pressure of the pressurized recharging well 10 is determined by the speed of the recharging water pump, and no specific control is performed. Only the pressure value of the pressurized recharging well 10 is monitored by the pressure sensor. 4. When the deep foundation pit dewatering operation continues for a period of time, the water level heights of the monitoring well 11, the normal pressure recharge well 12, and the pressure value of the pore water pressure sensor 13 change and are in a stable state. The recharge rate of the pressurized recharge well 10 is controlled by the feedback of the measurement results of the water level measuring instrument in the adjacent monitoring well 11, and the water level height in the normal pressure recharge well 12 is controlled by the feedback of the measurement results of the adjacent pore water pressure sensor 13; in the feedback control of the recharge rate of the pressurized recharge well 10, the average value of the water level heights of all monitoring wells 11 after stabilization is used as the benchmark. The difference between the measured result of the water level measuring instrument in the adjacent monitoring well 11 and the reference value is used as a feedback signal to feedback control the recharge rate of the corresponding pressurized recharge well 10, so that the measured result of the water level measuring instrument in the adjacent monitoring well 11 is stabilized at the reference value; in the feedback control of the water level height of the normal pressure recharge well 12, the difference between the measured result of the adjacent pore water pressure sensor 13 and the initial pressure value is used as a feedback signal to feedback control the water level height in the normal pressure recharge well 12, so that the measured result of the adjacent pore water pressure sensor 13 is stabilized at the initial pressure value; 5. During the deep foundation pit dewatering operation, the pressure sensor in the pressurized recharge well 10 continuously detects the recharge pressure at a set frequency. When the maximum pressure of the pressurized recharge reaches 0.2MPa, another pressurized recharge well 10 in the same group is started for pressurized recharge, and the recharge operation of the original pressurized recharge well 10 is stopped at the same time, and negative pressure pumping and lifting operation is carried out; when performing negative pressure pumping and lifting operation, the rate of the negative pressure pump is the same as the pumping rate of the adjacent dewatering well 9, with a cycle of 10 seconds of negative pressure pumping and 10 seconds of stopping pumping, and it lasts for 5 minutes; then open the valve on the sealing end cover, continue pumping for 5 minutes, and then close the valve on the sealing end cover to complete the negative pressure pumping and lifting operation and enter the standby state; 6. During the deep foundation pit dewatering operation, if the water level in the normal pressure recharge well 12 has reached the top of the pipe and still cannot maintain the initial pressure value of the adjacent pore water pressure sensor 13, the normal pressure recharge well 12 performs negative pressure pumping and lifting operation, and its operation method is basically the same as the negative pressure pumping and lifting operation of the pressurized recharge well 10; the difference between the negative pressure pumping and lifting operation of the normal pressure recharge well 12 and the negative pressure pumping and lifting operation of the pressurized recharge well 10 is that after the negative pressure pumping and lifting operation of the normal pressure recharge well 12 is completed, the valve on the sealing end cover is in a normally open state.

[0022] It should be understood that the present solution is not limited to the above-mentioned specific implementation methods, and the devices and structures not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present solution without departing from the scope of the technical solution of the present solution, or modify it into an equivalent embodiment with equivalent changes, which does not affect the essential content of the present solution. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present solution without departing from the content of the technical solution of the present solution still falls within the scope of protection of the technical solution of the present solution.

[0023] Parts of the present invention not described in detail are prior art.

Claims

1. A dewatering system for a deep foundation pit adjacent to a building, wherein a phreatic layer (6) and a confined water layer (8) exist underground at the bottom of the deep foundation pit (3), and the deep foundation pit (3) extends deep into the confined water layer (8); the system is characterized by: A ground-connected wall (1) is arranged around the deep foundation pit, and a water-stopping curtain (2) is arranged outside the ground-connected wall (1) adjacent to the building (14); a plurality of dewatering wells (9) are arranged inside the ground-connected wall (1), a plurality of pressurized reinjection wells (10) are arranged between the ground-connected wall (1) and the water-stopping curtain (2), and a plurality of normal-pressure reinjection wells (12) are arranged between the water-stopping curtain (2) and the building (14); a pressure sensor is arranged in the pressurized reinjection well (10), and a liquid level detection sensor is arranged in the normal-pressure reinjection well (12); the pressure sensor and the liquid level detection sensor are communicatively connected to a deep foundation pit dewatering monitoring terminal.

2. The deep foundation pit dewatering system adjacent to a building according to claim 1 is characterized by: The pressurized reinjection wells (10) are arranged in groups, and each group of pressurized reinjection wells (10) is provided with two pressurized reinjection wells (10), one of which is used as a standby well during water pumping and recharging operations.

3. The deep foundation pit dewatering system adjacent to a building according to claim 1 is characterized by: A recharging pipe is provided in the pressure recharging well (10) and the normal pressure recharging well (12). A filter material (10.2) is laid at the bottom of the recharging pipe and the bottom of the borehole. Clay balls (10.1), filter material (10.2), plastic spacers (10.3), and clay balls (10.4) are filled in sequence from bottom to top between the pipe wall and the borehole. Sealing grouting (10.5) is used for pressure grouting sealing near the pipe mouth.

4. The deep foundation pit dewatering system adjacent to a building according to claim 3 is characterized by: A sealing end cap is fixedly arranged at the top of the recharging pipe, and two pipe interfaces are arranged on the sealing end cap, one of which is connected to a recharging water pump through a pipeline, and the other is connected to a negative pressure water pump through a pipeline.

5. The dewatering system for deep foundation pits adjacent to buildings according to claim 4 is characterized by: The sealing end cover is also provided with a valve; the valve is in a closed state when the pressurized recharging well (10) is in operation, and the valve is in a normally open state when the normal pressure recharging well (12) is in operation.

6. The dewatering system for deep foundation pits adjacent to buildings according to claim 1 is characterized by: A plurality of monitoring wells (11) are also provided between the ground-connected wall (1) and the water-stop curtain (2) and in the deep foundation pit (3). A water level measuring instrument is provided in the monitoring well (11), and the water level measuring instrument is communicatively connected to the deep foundation pit dewatering monitoring terminal.

7. The dewatering system for deep foundation pits adjacent to buildings according to claim 1 is characterized by: A pore water pressure sensor (13) is also buried between the water-stop curtain (2) and the building (14), and the pore water pressure sensor (13) is communicatively connected to a deep foundation pit dewatering monitoring terminal.

8. The deep foundation pit dewatering system adjacent to a building according to claim 1 is characterized by: The building (14) is also provided with a tilt sensor, which is communicatively connected to a deep foundation pit dewatering monitoring terminal.

9. A dewatering operation method based on the dewatering system for deep foundation pits adjacent to buildings as claimed in any one of claims 1 to 7, characterized in that:

1. During the deep foundation pit dewatering process, the extracted groundwater is used as recharge water after sedimentation and filtration; 2. Recharge and pumping are carried out simultaneously, and the total recharge rate and total pumping rate are within 1.2 times of the set value; 3. The pressurized recharge well (10) adopts pressurized recharge, and the recharge rate is controlled by feedback from the measurement results of the adjacent water level measuring instrument; the maximum pressure of the pressurized recharge is not greater than 0.2MPa; 4. The normal pressure recharge well (12) adopts constant water level recharge, and the water level in the normal pressure recharge well (12) is controlled by feedback from the measurement results of the adjacent pore water pressure sensor (13).

10. The dewatering operation method of the deep foundation pit dewatering system adjacent to a building according to claim 6, characterized in that: When the pressurized pressure of the pressurized recharging well (10) is greater than the set value, negative pressure intermittent pumping and recharging operations must be performed.

Images