A rapid sealing device for sudden water inrush at the bottom of a foundation pit and its construction method

Abstract

This invention discloses a rapid sealing device and construction method for sudden water inrush at the bottom of a foundation pit, belonging to the field of building and geotechnical engineering technology. The structure includes a movable base, a pressure-reducing and flow-controlling cylinder, a reverse filtration and flow-controlling unit, a grouting reinforcement device, and an auxiliary sensing system. The movable base is equipped with a water inrush sensing contact, which can automatically position and seal the area. The pressure-reducing and flow-controlling cylinder has a built-in pressure relief valve and water tank, which automatically opens drainage based on the water pressure threshold to achieve dynamic pressure control. The reverse filtration and flow-controlling unit includes a nested reverse filter layer and an adjustable ballast plate, actively balancing the water pressure difference between the upper and lower parts of the reverse filter layer. The grouting reinforcement device has circumferentially arranged grouting reinforcement pipes that penetrate the soil layer and inject dual-liquid grout to form a radial curtain and a bottom plate reinforcement structure. The construction method includes steps such as inrush location, initial flow control and pressure reduction, reverse filtration and flow control, grouting reinforcement, and permanent sealing. This invention achieves rapid and accurate location of sudden water inrush, dynamic pressure control, integrated reverse filtration reinforcement, and intelligent construction, significantly shortening the sealing time and improving sealing reliability and adaptability.

Description

Technical Field

[0001] This invention relates to the field of building and geotechnical engineering, and in particular to a rapid sealing device for sudden water inrush at the bottom of a foundation pit and its construction method. Background Technology

[0002] With the continuous advancement of urbanization in my country, the development of urban underground space is becoming increasingly in-depth, and the number and scale of deep foundation pit projects are constantly growing. During the construction of deep foundation pit projects, due to the complexity and uncertainty of hydrogeological conditions, the problem of sudden water inrush at the bottom of the pit is becoming increasingly prominent. In existing technologies, the treatment of sudden water inrush in foundation pits typically adopts either a "drainage first, then sealing" or "dewatering and cofferdam" approach. Common methods involve setting up well points around the water inrush point for dewatering to reduce water head pressure, followed by grouting or concrete pouring for sealing in a waterless environment. Alternatively, a temporary cofferdam can be constructed to isolate the water inrush area, followed by pumping and sealing operations inside the cofferdam. These methods have slow response times; traditional methods require setting up well points for dewatering or constructing temporary cofferdams, which is time-consuming and makes it difficult to achieve rapid control in the early stages of water inrush, easily leading to soil erosion, structural deformation, or even collapse of the foundation pit. Conventional grouting and sealing methods struggle to accurately locate the water inrush channel; the grout is easily dispersed by seepage, and voids easily form between the sealing layer and the original strata, resulting in a high risk of later leakage and high costs associated with repeated treatments. Large-scale precipitation or cofferdam construction can alter the groundwater level around the foundation pit, causing differential settlement of adjacent buildings and structures, resulting in secondary disasters. Existing structures cannot monitor changes in inrush pressure in real time and automatically adjust flow control measures, making it difficult to cope with sudden surges in water head or fluctuations in inrush volume. Therefore, existing technologies suffer from technical bottlenecks such as low efficiency, poor reliability, and weak adaptability, failing to meet the demands of modern deep foundation pit engineering for rapid, precise, and intelligent handling of inrush disasters. Summary of the Invention

[0003] The purpose of this invention is to provide a rapid sealing device and construction method for sudden water inrush at the bottom of a foundation pit, so as to solve the technical problems of slow response speed, poor sealing effect, large secondary disturbance and lack of dynamic control capability in the prior art.

[0004] To achieve the above objectives, the present invention provides a rapid sealing device for sudden water inrush at the bottom of a foundation pit, comprising a movable base, a pressure-reducing and flow-controlling cylinder, a pressure-carrying platform, a reverse filter flow-controlling unit, and a grouting reinforcement device, characterized in that: the lower part of the movable base is provided with a water inrush sensing contact, used to sense the water inrush position and align it with the water inrush point. The pressure-reducing and flow-controlling cylinder includes a built-in flow-controlling cylinder and a pressure-controlling cover plate. The pressure-reducing and flow-controlling cylinder is disposed above the movable base. The pressure-controlling cover plate is provided with a water pressure sensor, a drain pipe and an adjustable pressure relief valve. The upper part of the drain pipe is connected to the adjustable pressure relief valve and the lower part is connected to the bottom water inrush point. When the water pressure in the built-in flow-controlling cylinder exceeds a preset threshold, the valve opens to drain water and reduce pressure. A water pipe is connected to the outside of the valve. The pressure platform is mounted on a movable base, and a water tank is mounted on the upper part of the pressure platform. The water pipe is connected to the water tank mounted on the pressure platform. The reverse filter flow control unit is disposed in the built-in flow control cylinder and is used to actively balance the water pressure difference between the upper and lower sides of the reverse filter layer. The grouting reinforcement device includes several grouting reinforcement pipes evenly distributed around the side of the built-in flow control cylinder. When excessive water pressure is detected or the reverse filter flow control unit is in an abnormal state, the grouting reinforcement pipes are driven by external force to press into the soil layer and inject reinforcement grout to form a circumferential reinforcement ring.

[0005] The movable base is equipped with electric casters and is disc-shaped or square. Its bottom is equipped with a rubber water-stop sealing ring or an inflatable sealing bladder. Four electric spiral anchors are evenly arranged on the outer periphery of the movable base. When the movable base moves to the water inflow position, the electric spiral anchors are anchored into the soil layer respectively, and at the same time, the rubber water-stop sealing ring or inflatable sealing bladder is pressed to form a seal between the movable base and the bottom of the pit.

[0006] The bottom of the built-in flow control cylinder is connected to the water inflow channel of the movable base. A drain hole is provided on the cylinder. An adjustable pressure relief valve is installed on the outside of the drain hole. The outlet of the pressure relief valve is connected to the water tank through a flexible high-pressure hose.

[0007] The reverse filtration flow control unit is configured from bottom to top as follows: a stainless steel filter screen, a gravel layer, a bentonite particle layer, a fine sand layer, and a non-woven geotextile.

[0008] The adjustable pressure relief valve is installed at the center perforation of the pressure control cover plate. It adopts a conical spring valve core structure, and an adjusting nut for preset pressure relief opening pressure is provided between the valve core and the pressure control cover plate.

[0009] The grouting reinforcement pipe is a steel pipe with a closed front end and lateral grouting holes. The pipe body has a double channel arranged along the axial direction. The grouting reinforcement pipe is driven by a hydraulic cylinder or an electric push rod and can penetrate radially into the soil from 0.5m to 1.5m.

[0010] It also includes an auxiliary sensing and control system, which includes a distributed water pressure sensor, a flow meter, an earth pressure gauge, a camera, and a PLC controller. All sensor signals are fed into the PLC controller, which is connected to the operating terminal via a wireless communication module.

[0011] In addition, a method for constructing a rapid sealing device for water inrush at the bottom of a foundation pit is provided, including the following steps: Step S1: Sudden surge positioning and structural placement. Control the movable base to move above the water surge point, trigger the placement signal through the water surge sensing contact, lock the base position and complete the initial fixation; Step S2: Initial flow control and pressure reduction. Anchor four electric spiral anchors into the bottom layer so that the movable base is in close contact with the ground. At the same time, press the rubber water-stop sealing ring or the inflatable sealing bladder to seal the bottom. The drain pipe is connected to the water tank. Step S3: Reverse filtration and flow control operation, real-time monitoring of water pressure, automatic opening or closing of the adjustable pressure relief valve to maintain pressure balance; when the water pressure in the built-in flow control cylinder exceeds the preset threshold, the valve is opened to the maximum to allow the gushing water to be quickly introduced into the water tank, reducing the gushing water pressure; Step S4: Grouting reinforcement and permanent sealing. Start the grouting reinforcement device, insert the grouting reinforcement pipe into the soil layer and inject dual-liquid grout to form a circumferential reinforcement ring, which reinforces the soil layer around the water inflow and partially cuts off the water inflow path.

[0012] In step S4, a quick-setting dual-liquid slurry with an initial setting time of 10-30 seconds is first injected to form a temporary sealing ring, and then a slow-setting dual-liquid slurry with an initial setting time of 5-8 minutes is injected to form a permanent reinforcement ring. In step S3, a periodic backwashing mode is also introduced, using clean water in the water tank to backwash the nested filter layer to maintain its backwashing efficiency. In step S2 or step S3, when the inflow rate exceeds a preset value, a set of parallel pressure-reducing and flow-controlling cylinders are added to achieve multi-stage pressure reduction and directly introduce the inflowing water into the external sump pit.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) Fast response and precise positioning. The movable base is linked with the water inrush sensor contact. It only takes a few minutes from the occurrence of water inrush to the placement of the flow control device, which is much faster than the traditional process and minimizes the risk of soil erosion and foundation pit deformation. (2) Dynamic balance and active pressure control. The pressure-reducing flow control cylinder, together with the adjustable pressure relief valve and the reverse filter flow control unit, can adjust the drainage volume in real time according to the water inrush pressure, avoid the sudden drop in water head causing soil instability, and achieve safe progressive treatment. (3) Integrated reverse filtration and reinforcement, thorough sealing. The reverse filter layer intercepts fine particles and forms a natural filter cake. The grouting reinforcement pipe is radially inserted to form a permanent curtain. The bottom plate reinforcement structure eliminates the interface leakage channel. The triple defense line ensures that there are no gaps or leakage points between the sealing layer and the original stratum, and has a long service life. (4) It is highly adaptable and has a wide range of applications. With adjustable ballast plates, modular filter layers and various types of grouting materials, it can cope with different strata and water inflow characteristics, and supports multi-machine parallel operation and remote control. (5) It is environmentally friendly and has little secondary disturbance. It only seals the water inflow point locally, without the need for large-area dewatering or the construction of cofferdams. It has a small disturbance range to the surrounding soil and effectively protects the safety of nearby buildings and underground pipelines. (6) It has a high degree of intelligence. It integrates sensor networks and automatic control strategies to realize full automation and remote monitoring of the sealing process. Attached Figure Description

[0014] Figure 1 This is an overall schematic diagram of the rapid sealing device provided in Embodiment 1 of the present invention.

[0015] Figure 2 This is a construction schematic diagram of the rapid sealing device provided in Embodiment 1 of the present invention.

[0016] Figure 3 This is a schematic diagram of the reverse filter flow control unit provided in Embodiment 2 of the present invention.

[0017] In the diagram: 1—Movable base; 2—Pressure-reducing and flow-controlling cylinder; 3—Reverse filtration and flow-controlling unit; 4—Grouting reinforcement device; 5—Water inrush sensor contact; 6—Pressure-carrying platform; 7—Water tank; 8—Rubber water-stop sealing ring; 9—Control system; 10—Electric caster wheel; 11—Built-in flow-controlling cylinder; 12—Pressure control cover plate; 13—Adjustable pressure relief valve; 14—Grouting reinforcement pipe; 15—Drainage pipe; 16—Electric spiral anchor; 110—Stainless steel filter screen; 111—Crushed stone layer; 112—Bentonite particle layer; 113—Fine sand layer; 114—Non-woven geotextile. Detailed Implementation To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] This embodiment provides a rapid sealing device for sudden water inrush at the bottom of a foundation pit, used to handle sudden water inrush situations occurring in conventional sandy foundation pits. For example... Figure 1 and Figure 2 As shown, the structure includes a movable base 1, a pressure-reducing and flow-controlling cylinder 2, a reverse filter and flow-controlling unit 3, a grouting reinforcement device 4, and an auxiliary sensing system.

[0019] The movable base 1 is disc-shaped, with a rubber water-stop sealing ring 8 at its bottom. A water inrush sensing contact 5, specifically a pressure sensor, is installed in the center of the base. Electric casters 10 are arranged around the base, and four electric spiral anchors 16 are evenly distributed around the outer perimeter of the movable base 1. When the movable base 1 moves to the water inrush position, the electric spiral anchors 16 anchor into the soil layer, simultaneously compressing the rubber water-stop sealing ring 8 or an inflatable sealing bladder to seal the movable base 1 and the bottom of the pit. During construction, the movable base 1 is remotely controlled to move directly above the water inrush point. When the water inrush sensing contact 5 accurately contacts the water inrush point, the system automatically sends a positioning signal, locks the base position, and triggers the expansion of the rubber water-stop sealing ring 8 (or an inflatable sealing bladder), effectively isolating the base from the bottom of the pit.

[0020] The pressure-reducing and flow-controlling cylinder 2 includes a built-in flow-controlling cylinder 11 and a pressure-controlling cover plate 12. The pressure-reducing and flow-controlling cylinder 2 is positioned above the movable base 1. The pressure-controlling cover plate 12 is equipped with a water pressure sensor, a drain pipe 15, and an adjustable pressure relief valve 13. The upper part of the drain pipe 15 is connected to the adjustable pressure relief valve 13, and the lower part is connected to the bottom water inflow point. When the water pressure inside the built-in flow-controlling cylinder 11 exceeds a preset threshold, the valve opens to drain water and reduce pressure. A water pipe is connected to the outside of the valve. A drain hole is opened at the top of the cylinder, and an adjustable pressure relief valve 13 (or solenoid valve) is installed outside the drain hole. The outlet of the pressure relief valve is connected to a water tank 7 placed on the pressure-carrying platform 6 via a flexible high-pressure hose. The pressure-controlling cover plate 12 seals the top of the cylinder, and a vibrating wire water pressure sensor and a flow meter are installed on the cover plate for real-time monitoring of the water pressure and inflow rate inside the cylinder. When the water pressure sensor detects that the pressure inside the cylinder exceeds the preset threshold (e.g., 0.4MPa), the controller automatically opens the pressure relief valve to divert the high-pressure water to the water tank 7, thereby achieving active pressure reduction and flow control. When the water pressure drops to a safe value, the pressure relief valve automatically closes.

[0021] The reverse filtration flow control unit 3 is built into the built-in flow control cylinder 11. The reverse filtration flow control unit 3 is arranged from bottom to top as follows: a stainless steel filter screen 110, a crushed stone layer 111, a bentonite particle layer 112, a fine sand layer 113, and a non-woven geotextile 114. An adjustable pressure relief valve 13 is installed at the center perforation of the pressure control cover plate 12. It adopts a conical spring valve core structure. When the pressure difference between the upper and lower water of the reverse filtration flow control unit 3 exceeds the design value, the valve automatically opens to drain water, actively balances the pressure, and prevents the reverse filtration layer from being damaged by seepage.

[0022] The grouting reinforcement device 4 includes four circumferentially distributed pressure lifting devices on the sides of the built-in flow control cylinder 11, a grouting reinforcement pipe 14, and a grouting pump. The grouting reinforcement pipe 14 is an O-shaped steel pipe with a closed front end and a lateral grouting hole. Spiral blades are welded to the outside of the pipe. The pressure lifting device is a hydraulic cylinder that can radially insert the grouting reinforcement pipe into the soil. The insertion depth is controlled by a water pressure sensor and soil resistance. After the grouting reinforcement pipe is inserted, the grouting reinforcement operation is performed.

[0023] The auxiliary sensing system includes distributed water pressure sensors, flow meters, earth pressure gauges, CCD cameras, and a PLC controller. All sensor signals are fed into the controller, which connects to a ground-based operating terminal via a wireless communication module, enabling full-process automation and remote monitoring.

[0024] Based on the above structure, the construction method of this embodiment includes the following steps: Step S1: Sudden Water Inrush Positioning and Structure Placement. When a sudden water inrush occurs at the bottom of the foundation pit, immediately activate the ground remote control device to move the movable base 1 above the water inrush point. The water inrush sensing contact 5 in the center of the base contacts the water inrush. When the continuous water flow impact force reaches the set value and lasts for more than 3 seconds, the placement signal is automatically triggered, locking the base and expanding the rubber water-stop sealing ring 8 to complete the initial fixation.

[0025] Step S2: Initial flow control and pressure reduction. Anchor four electric spiral anchors 16 into the bottom layer so that the movable base 1 is in close contact with the ground. At the same time, press the rubber water-stop sealing ring 8 or the inflatable sealing bladder to seal the bottom. The drain pipe 15 is connected to the water tank 7.

[0026] Step S3: Reverse filtration and flow control operation, real-time monitoring of water pressure, automatic opening or closing of the adjustable pressure relief valve 13 to maintain pressure balance; when the water pressure in the built-in flow control cylinder 11 exceeds the preset threshold, the valve is opened to the maximum to allow the gushing water to be quickly introduced into the water tank 7, reducing the gushing water pressure.

[0027] Step S4: Grouting Reinforcement and Permanent Sealing. Once the water pressure stabilizes, activate the grouting reinforcement device 4. Simultaneously insert four grouting reinforcement pipes 14 into the soil layer surrounding the water inflow point using hydraulic cylinders, to a depth of 1.0 meter. Inject cement-water glass dual-liquid grout (water-cement ratio 0.8, initial setting time 20 seconds) to form a radial waterproof curtain ring. After the radial curtain has initially set, continue injecting slow-setting grout at a lower pressure, allowing the grout to spread along the bottom edge of the base to form a continuous closed structure. Simultaneously, anchor the base to the reinforcement ring using pre-embedded U-shaped anchor bolts.

[0028] Example 2 The main difference between this embodiment and Embodiment 1 is that the structure and method have been adapted for scenarios with extremely high water flow rates (such as exceeding 100 cubic meters per hour). In this embodiment, after completing the initial flow control and pressure reduction in step S2, the controller determines that the drainage capacity of a single set of pressure-reducing flow control cylinders 2 is insufficient based on the flow data fed back by the auxiliary sensing system. At this time, the construction method adds an extra step after step S2: connecting the second set of parallel pressure-reducing flow control cylinders 2 to the original system through quick connectors to achieve "multi-stage pressure reduction". The water tank drain pipe of this second set of truncated cones is directly led to the sump outside the foundation pit, thereby avoiding flow control interruption due to insufficient water tank capacity. At the same time, the adjustable pressure relief valve 13 in the built-in flow control cylinder 11 is replaced with a combined overflow valve and an electric regulating valve. With the help of the PID control algorithm, it can more accurately follow and stabilize the water pressure inside the cylinder, and maintain the dynamic balance of the system even under large flow impacts.

[0029] Example 3 This embodiment is applicable to situations where the water inflow point is located in a highly permeable pebble layer and where pressurized water exists. Adjustments were made to the grouting materials and process to suit the characteristics of this type of stratum. In step S4, grouting reinforcement, the grouting material was replaced from the standard cement-water glass two-component grout with a polyurethane-cement composite grout. This composite grout has better fluidity and filling properties, effectively penetrating the larger voids between the pebbles. The construction process was correspondingly adjusted to a "low-pressure slow-permeability" mode, with the grouting pressure controlled at 0.15 MPa and the single grouting time extended to 45 minutes, ensuring that the grout can fully and evenly fill the voids in the pebble layer, forming a dense and high-strength water-stop curtain.

[0030] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A rapid sealing device for sudden water inrush at the bottom of a foundation pit, comprising a movable base, a pressure-reducing and flow-controlling cylinder, a pressure-carrying platform, a reverse filter and flow-controlling unit, and a grouting reinforcement device, characterized in that: The lower part of the movable base is provided with a water inrush sensor contact, which is used to sense the location of the water inrush and align it with the water inrush point. The pressure-reducing and flow-controlling cylinder includes a built-in flow-controlling cylinder and a pressure-controlling cover plate. The pressure-reducing and flow-controlling cylinder is disposed above the movable base. The pressure-controlling cover plate is provided with a water pressure sensor, a drain pipe and an adjustable pressure relief valve. The upper part of the drain pipe is connected to the adjustable pressure relief valve and the lower part is connected to the bottom water inrush point. When the water pressure in the built-in flow-controlling cylinder exceeds a preset threshold, the valve opens to drain water and reduce pressure. A water pipe is connected to the outside of the valve. The pressure platform is mounted on a movable base, and a water tank is mounted on the upper part of the pressure platform. The water pipe is connected to the water tank mounted on the pressure platform. The reverse filter flow control unit is disposed in the built-in flow control cylinder and is used to actively balance the water pressure difference between the upper and lower sides of the reverse filter layer. The grouting reinforcement device includes several grouting reinforcement pipes evenly distributed around the side of the built-in flow control cylinder. When excessive water pressure is detected or the reverse filter flow control unit is in an abnormal state, the grouting reinforcement pipes are driven by external force to press into the soil layer and inject reinforcement grout to form a circumferential reinforcement ring.

2. The rapid sealing device for sudden water inrush at the bottom of the foundation pit as described in claim 1, characterized in that, The movable base is equipped with electric casters and is disc-shaped or square. Its bottom is equipped with a rubber water-stop sealing ring or an inflatable sealing bladder. Four electric spiral anchors are evenly arranged on the outer periphery of the movable base. When the movable base moves to the water inflow position, the electric spiral anchors are anchored into the soil layer respectively, and at the same time, the rubber water-stop sealing ring or inflatable sealing bladder is pressed to form a seal between the movable base and the bottom of the foundation pit.

3. The rapid sealing device for sudden water inrush at the bottom of the foundation pit as described in claim 1, characterized in that, The bottom of the built-in flow control cylinder is connected to the water inflow channel of the movable base. A drain hole is provided on the cylinder. An adjustable pressure relief valve is installed on the outside of the drain hole. The outlet of the pressure relief valve is connected to the water tank through a flexible high-pressure hose.

4. The rapid sealing device for sudden water inrush at the bottom of the foundation pit as described in claim 1, characterized in that, The reverse filtration flow control unit is configured from bottom to top as follows: a stainless steel filter screen, a gravel layer, a bentonite particle layer, a fine sand layer, and a non-woven geotextile.

5. The rapid sealing device for sudden water inrush at the bottom of the foundation pit as described in claim 1, characterized in that, The adjustable pressure relief valve is installed at the center perforation of the pressure control cover plate. It adopts a conical spring valve core structure, and an adjusting nut for preset pressure relief opening pressure is provided between the valve core and the pressure control cover plate.

6. The rapid sealing device for sudden water inrush at the bottom of the foundation pit as described in claim 1, characterized in that, The grouting reinforcement pipe is a steel pipe with a closed front end and lateral grouting holes. The pipe body has a double channel arranged along the axial direction. The grouting reinforcement pipe is driven by a hydraulic cylinder or an electric push rod and can penetrate radially into the soil from 0.5m to 1.5m.

7. The rapid sealing device for sudden water inrush at the bottom of a foundation pit as described in any one of claims 1 to 6, characterized in that, It also includes an auxiliary sensing and control system, which includes a distributed water pressure sensor, a flow meter, an earth pressure gauge, a camera, and a PLC controller. All sensor signals are fed into the PLC controller, which is connected to the ground operation terminal via a wireless communication module.

8. A method for construction using a rapid sealing device for water inrush at the bottom of a foundation pit as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step S1: Sudden surge positioning and structural placement. Control the movable base to move above the water surge point, trigger the placement signal through the water surge sensing contact, lock the base position and complete the initial fixation; Step S2: Initial flow control and pressure reduction. Anchor four electric spiral anchors into the bottom layer so that the movable base is in close contact with the ground. At the same time, press the rubber water-stop sealing ring or the inflatable sealing bladder to seal the bottom. The drain pipe is connected to the water tank. Step S3: Reverse filtration and flow control operation, real-time monitoring of water pressure, automatic opening or closing of the adjustable pressure relief valve to maintain pressure balance; when the water pressure in the built-in flow control cylinder exceeds the preset threshold, the valve is opened to the maximum to allow the gushing water to be quickly introduced into the water tank, reducing the gushing water pressure; Step S4: Grouting reinforcement and permanent sealing. Start the grouting reinforcement device, insert the grouting reinforcement pipe into the soil layer and inject dual-liquid grout to form a circumferential reinforcement ring, which reinforces the soil layer around the water inflow and partially cuts off the water inflow path.

9. The construction method as described in claim 8, characterized in that, In step S4, a quick-setting dual-liquid slurry with an initial setting time of 10-30 seconds is first injected to form a temporary sealing ring, and then a slow-setting dual-liquid slurry with an initial setting time of 5-8 minutes is injected to form a permanent reinforcement ring. In step S3, a periodic backwashing mode is also introduced, using clean water in the water tank to backwash the nested filter layer to maintain its backwashing efficiency. In step S2 or step S3, when the inflow rate exceeds a preset value, a set of parallel pressure-reducing and flow-controlling cylinders are added to achieve multi-stage pressure reduction and directly introduce the inflowing water into the external sump pit.

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