Drainage system and drainage method for foundation pit

Abstract

The invention relates to the technical field of water conservancy projects, in particular to a drainage system and drainage method for a foundation pit, the drainage system comprises a flexible filter screen, a drainage pump and a supporting assembly, the flexible filter screen is cylindrical, the upper end of the flexible filter screen is through, and the lower end of the flexible filter screen is sealed. According to the invention, the flexible filter screen and the supporting assembly are arranged, when the flexible filter screen is buried by sludge, the flexible filter screen is sunken inwards to be approximately elliptical, and along with continuous rotation of the central rotating shaft, all positions in the circumferential direction of the flexible filter screen continuously change between the position corresponding to the long axis of the ellipse and the position corresponding to the short axis of the ellipse; the flexible filter screen continuously pushes the sludge to the direction far away from the center of the flexible filter screen and then independently moves towards the center of the flexible filter screen, so that a gap area can be reserved between the flexible filter screen and the sludge, and water in the water collecting well can enter the input end of the drainage pump through the flexible filter screen; normal operation of the draining pump is guaranteed, and idling of the draining pump is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy projects, and particularly to a drainage system and a drainage method for a foundation pit. Background Art

[0002] Drainage after foundation pit excavation is crucial for the safety and convenience of on-site construction operations, and is an essential part of ensuring project quality. Because the presence of groundwater will weaken the stability of the soil and increase the risk of soil slip or collapse. Especially for those soil types that are originally relatively loose or have a high water content (such as sandy soil, silt, etc.), the increase in the water accumulation will make the situation more dangerous. Therefore, after the foundation pit is excavated, it is necessary to timely drain the groundwater seeping out of the foundation pit to ensure that the foundation pit will not be damaged by groundwater.

[0003] The commonly used foundation pit drainage methods in the prior art are open ditch drainage method and well point dewatering method. Among them, the open ditch drainage method is the most commonly used drainage method. Specifically, it digs drainage ditches around the foundation pit and sets sump wells, so that the water in the foundation pit flows along the drainage ditches and converges into the sump wells, and then uses a water pump to drain the collected groundwater out of the pit. In the above drainage process, the following problems exist: a very thick layer of sludge often accumulates at the bottom of the sump well. After the input end of the water pump is placed at the bottom of the sump well, the input end of the water pump is extremely easy to be buried by the sludge, resulting in the water pump running idly. Summary of the Invention

[0004] Based on this, it is necessary to provide a drainage system and a drainage method for a foundation pit to solve the problem that the input end of the water pump is extremely easy to be buried by sludge in view of the problems existing in the current foundation pit drainage system.

[0005] The above object is achieved by the following technical solutions: A drainage system for a foundation pit includes: A flexible filter screen, the flexible filter screen is cylindrical, its upper end is through, and its lower end is sealed; A drainage pump, the input end of the drainage pump is communicated with the inside of the flexible filter screen; Support component, the support component includes a central rotating shaft, a first telescopic rod, a second telescopic rod, a first support rod and a second support rod. The central rotating shaft can rotate around its axis, the axis of the central rotating shaft coincides with the axis of the flexible filter screen, and the lower end of the central rotating shaft is rotatably connected to the flexible filter screen. There are multiple first telescopic rods and multiple second telescopic rods. The multiple first telescopic rods and the multiple second telescopic rods are circumferentially arranged at equal intervals around the axis of the central rotating shaft and are alternately arranged. The first support rod is rotatably abutted against the inner peripheral wall of the flexible filter screen. There are multiple first support rods, and the multiple first support rods correspond to the multiple first telescopic rods one by one. The middle part of the first support rod is fixedly connected to the end of the first telescopic rod far from the central rotating shaft. The second support rod is rotatably abutted against the inner peripheral wall of the flexible filter screen. There are multiple second support rods, and the multiple second support rods correspond to the multiple second telescopic rods one by one. The middle part of the second support rod is fixedly connected to the end of the second telescopic rod far from the central rotating shaft; In the initial state, the first telescopic rod is at the shortest length and the second telescopic rod is at the longest length; When the second telescopic rod shortens by a preset length, the first telescopic rod can correspondingly extend by the preset length; And the length change amount of the second telescopic rod is negatively correlated with the flow-through area of the flexible filter screen.

[0006] Preferably, the flexible filter screen includes an annular filter screen, a metal bellows and a support plate. There are two metal bellows, and the two metal bellows are arranged at intervals up and down, and the two metal bellows are respectively arranged at both ends of the annular filter screen. There are two support plates, and the two support plates are arranged at intervals up and down. The support plate located above is fixedly connected to the end of the metal bellows located above far from the annular filter screen. The support plate located below is fixedly connected to the end of the metal bellows located below far from the annular filter screen; A communication hole is opened on the upper surface of the support plate located above, and the communication hole is communicated with the input end of the drainage pump.

[0007] Preferably, a spiral impeller is arranged on the outer periphery of the central rotating shaft. The spiral impeller is located inside the input end of the drainage pump, and the spiral impeller is used to guide the fluid in the annular filter screen into the input end of the drainage pump.

[0008] Preferably, the flexible filter screen further includes support columns. There are multiple support columns, and the multiple support columns are arranged circumferentially at equal intervals around the annular filter screen. Both ends of the support columns are fixedly connected to the corresponding support plates.

[0009] Preferably, a driving member is arranged outside the annular filter screen, and the output end of the driving member is fixedly connected to the central rotating shaft.

[0010] Preferably, the annular filter screen is conical, and the cross-sectional area decreases from top to bottom.

[0011] Preferably, wear-resistant sleeves are rotatably sleeved outside the first support rod and the second support rod.

[0012] Preferably, the first telescopic rod includes a first hydraulic sleeve, a first piston rod and a retaining ring. The first hydraulic sleeve is arranged on the central rotating shaft. The first piston rod is slidably connected inside the first hydraulic sleeve. The retaining ring is coaxially arranged outside the first piston rod. In the initial state, the retaining ring abuts against the first hydraulic sleeve.

[0013] Preferably, the second telescopic rod includes a second hydraulic sleeve, a second piston rod and an elastic member. The second hydraulic sleeve is arranged on the central rotating shaft. The inside of the second hydraulic sleeve is communicated with the inside of the first hydraulic sleeve. The second piston rod is slidably connected inside the second hydraulic sleeve. The elastic member is arranged inside the second hydraulic sleeve. One end of the elastic member is fixedly connected to the second hydraulic sleeve, and the other end of the elastic member is fixedly connected to the second piston rod. The elastic member is used to make the second piston rod extend to the maximum length.

[0014] A drainage method for a foundation pit uses the drainage system for the foundation pit described above.

[0015] The beneficial effects of the present invention are as follows: The present invention is provided with a flexible filter screen and a support assembly. After the flexible filter screen is buried by sludge, under the suction action of the drainage pump, the flexible filter screen sinks inward. When the number of the first telescopic rods and the second telescopic rods corresponding to the support assembly is two, the flexible filter screen sinks inward to form an approximately elliptical shape. As the central rotating shaft continues to rotate, the positions of various parts in the circumferential direction of the flexible filter screen constantly change between the positions corresponding to the major axis of the ellipse and the positions corresponding to the minor axis of the ellipse, so that the flexible filter screen continuously first pushes the sludge in the direction away from its center, and then moves alone in the direction of its center, so that a gap area can be left between the flexible filter screen and the sludge, so as to ensure that the water in the sump can enter the input end of the drainage pump through the flexible filter screen, thereby ensuring the normal operation of the drainage pump and avoiding the idling of the drainage pump. Description of the Drawings

[0016] Figure 1 is the overall schematic diagram of a drainage system for a foundation pit of the present invention; Figure 2 is the front view of a drainage system for a foundation pit of the present invention; Figure 3 is Figure 2 the half-sectional axonometric view of A-A in Figure 4 is Figure 2 the sectional view of A-A in Figure 5 is Figure 3 the enlarged schematic diagram of the structure at C in Figure 6 For Figure 2 Cross-sectional view B-B in Figure 7 For Figure 6 Schematic diagram of the enlarged structure at position D in Figure 8 Schematic diagram of the usage state of the annular filter screen in the drainage system of a foundation pit according to the present invention; Figure 9 For Figure 8 Schematic diagram of the enlarged structure at position E in Figure 10 For Figure 8 Schematic diagram of the enlarged structure at position F in

[0017] Wherein: 100, flexible filter screen; 110, annular filter screen; 120, metal bellows; 130, support plate; 140, support column; 200, drainage pump; 300, support assembly; 310, central rotating shaft; 320, first telescopic rod; 321, first hydraulic sleeve; 322, first piston rod; 323, retaining ring; 330, second telescopic rod; 331, second hydraulic sleeve; 332, second piston rod; 333, elastic member; 340, first support rod; 350, second support rod; 400, driving member; 500, spiral impeller. Detailed implementation manners

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any sequential or technical meanings. The "connection" and "coupling" mentioned in the present invention, unless otherwise specified, both include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0020] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0021] As Figures 1 to 10 shown, a drainage system for a foundation pit includes a flexible filter screen 100, a drainage pump 200 and a support assembly 300. The flexible filter screen 100 is cylindrical, with its upper end being through and its lower end being sealed. The input end of the drainage pump 200 (i.e., the water pipe connected to the water inlet of the drainage pump 200) is in communication with the interior of the flexible filter screen 100. The support assembly 300 includes a central rotating shaft 310, a first telescopic rod 320, a second telescopic rod 330, a first support rod 340 and a second support rod 350. The central rotating shaft 310 can rotate about its axis, and the axis of the central rotating shaft 310 coincides with the axis of the flexible filter screen 100. Moreover, the lower end of the central rotating shaft 310 is rotatably connected to the flexible filter screen 100. There are multiple first telescopic rods 320 and multiple second telescopic rods 330. The multiple first telescopic rods 320 and the multiple second telescopic rods 330 are circumferentially arranged at equal intervals around the axis of the central rotating shaft 310 and are arranged alternately. The first support rod 340 is in rotational abutment with the inner peripheral wall of the flexible filter screen 100. There are multiple first support rods 340, and the multiple first support rods 340 correspond to the multiple first telescopic rods 320 one by one. Moreover, the middle part of the first support rod 340 is fixedly connected to the end of the first telescopic rod 320 far from the central rotating shaft 310. The second support rod 350 is in rotational abutment with the inner peripheral wall of the flexible filter screen 100. There are multiple second support rods 350, and the multiple second support rods 350 correspond to the multiple second telescopic rods 330 one by one. Moreover, the middle part of the second support rod 350 is fixedly connected to the end of the second telescopic rod 330 far from the central rotating shaft 310. In the initial state, the first telescopic rod 320 is at the shortest length, and the second telescopic rod 330 is at the longest length. When the second telescopic rod 330 shortens by a preset length, the first telescopic rod 320 can correspondingly elongate by the preset length, and the length change amount of the second telescopic rod 330 is negatively correlated with the flow-through area of the flexible filter screen 100.

[0022] The working principle is described with both the number of the first telescopic rod 320 and the second telescopic rod 330 being two. Specifically, during use, the staff sinks the flexible filter screen 100 to the bottom of the sump, starts the drainage pump 200, and at the same time, makes the central rotating shaft 310 rotate slowly around its own axis. When the flexible filter screen 100 is buried by sludge, under the suction of the drainage pump 200, the flexible filter screen 100 depresses inward by itself. At this time, the inward depression of the flexible filter screen 100 pushes the second telescopic rod 330 to start shortening from its longest length. When the second telescopic rod 330 shortens by a preset length, the first telescopic rod 320 correspondingly elongates by a preset length. At this time, under the supporting action of the first support rod 340 connected to the two first telescopic rods 320 and the second support rod 350 connected to the two second telescopic rods 330, the flexible filter screen 100 is approximately deformed into an ellipse. With the continuous rotation of the central rotating shaft 310, the central rotating shaft 310 drives the first telescopic rod 320 and the second telescopic rod 330 to rotate synchronously and slowly. At this time, the supporting points of the first support rod 340 and the second support rod 350 on the circumference of the flexible filter screen 100 are constantly changing. Therefore, the positions of the major axis and the minor axis of the flexible filter screen 100 supported by the first support rod 340 and the second support rod 350 are constantly changing. When a certain position of the flexible filter screen 100 changes from the position corresponding to the minor axis to the position corresponding to the major axis, the flexible filter screen 100 pushes the sludge in the direction away from its center. Next, when the position of this part of the flexible filter screen 100 changes from the position corresponding to the major axis to the position corresponding to the minor axis, the flexible filter screen 100 moves towards its center. Due to the poor fluidity of the sludge, at this time, the flexible filter screen 100 and the sludge are separated from each other, and a void area appears between the flexible filter screen 100 and the sludge in this area. At this time, the accumulated water in the sump can quickly enter the interior of the drainage pump 200 through the flexible filter screen 100 in this area. With the continuous rotation of the central rotating shaft 310, the positions of all parts on the circumference of the flexible filter screen 100 keep changing between the position corresponding to the major axis and the position corresponding to the minor axis, so that the flexible filter screen 100 continuously pushes the sludge away from its center first and then moves towards its center to ensure that there is a void area between the flexible filter screen 100 and the sludge, so as to ensure that the water in the sump can enter the input end of the drainage pump 200 through the flexible filter screen 100, thereby ensuring the normal operation of the drainage pump 200 and avoiding the idling of the drainage pump 200.

[0023] It can be understood that the more tightly the flexible filter screen 100 is buried by sludge, the smaller the flow-through area on the surface of the flexible filter screen 100. Under the suction of the drainage pump 200, the deformation amount of the flexible filter screen 100 is larger. In this way, the length change amounts of the first telescopic rod 320 and the second telescopic rod 330 are larger. Thus, the difference between the major axis and the minor axis of the ellipse formed after the flexible filter screen 100 is deformed is larger. When each position on the circumferential direction of the flexible filter screen 100 changes between the position corresponding to the major axis and the position corresponding to the minor axis, the flexible filter screen 100 can push the sludge to a position farther away from the center of the flexible filter screen 100. When there is a large amount of sand and soil in the sludge, after the flexible filter screen 100 pushes the sludge to a position away from the center of the flexible filter screen 100, due to the poor fluidity of the sludge, the sludge is more likely to accumulate together and is not easy to move towards the center of the flexible filter screen 100. Therefore, the flow-through area of the flexible filter screen 100 will increase correspondingly. At this time, the difference between the major axis and the minor axis of the ellipse formed after the flexible filter screen 100 is deformed decreases. Therefore, the disturbance of the flexible filter screen 100 to the water flow during the deformation process is reduced, and the area blocked by the sediment in the water flow on the flexible filter screen 100 can be effectively reduced. In summary, the effect of adaptively adjusting the difference between the major axis and the minor axis of the ellipse formed after the flexible filter screen 100 is deformed is achieved. In this way, not only can the normal flow-through of the flexible filter screen 100 be ensured, further avoiding the idling of the drainage pump 200, but also the area blocked by the sediment in the water flow on the flexible filter screen 100 can be effectively reduced.

[0024] It should also be supplemented that during the deformation of the flexible filter screen 100, the water in the sump can backwash the flexible filter screen 100, which helps the flexible filter screen 100 to perform self-cleaning and prevents the flexible filter screen 100 from being severely blocked.

[0025] It should also be supplemented that in addition to configuring the numbers of the first telescopic rod 320 and the second telescopic rod 330 to be both two, the numbers of the first telescopic rod 320 and the second telescopic rod 330 can also be configured to be three. Such a setting can reduce the deformation amplitude of the flexible filter screen 100 and increase the deformation frequency of the flexible filter screen 100 while the central rotating shaft 310 rotates circumferentially. This configuration form is suitable for the situation with a relatively large content of sand and soil. Reducing the deformation amplitude of the flexible filter screen 100 can reduce the disturbance to the water flow, and increasing the deformation frequency of the flexible filter screen 100 can ensure an increase in the backwashing frequency of the flexible filter screen 100 and timely remove the sand and soil blocked in the mesh holes of the flexible filter screen 100.

[0026] In this embodiment, as Figure 2 and Figure 3As shown, the flexible filter screen 100 includes an annular filter net 110, metal bellows 120 and support plates 130. There are two metal bellows 120, which are arranged at intervals up and down, and the two metal bellows 120 are respectively arranged at both ends of the annular filter net 110. There are two support plates 130, which are arranged at intervals up and down. Among them, the upper support plate 130 is fixedly connected to the end of the upper metal bellows 120 far away from the annular filter net 110, and the lower support plate 130 is fixedly connected to the end of the lower metal bellows 120 far away from the annular filter net 110. A communication hole is opened on the upper surface of the upper support plate 130, and the communication hole is communicated with the input end of the drainage pump 200. The purpose of opening the communication hole is to ensure that the water in the flexible filter screen 100 can enter the water pipe at the input end of the drainage pump 200 through the communication hole.

[0027] It can be understood that the metal bellows 120 are arranged at the upper and lower ends of the annular filter net 110 to enable the annular filter net 110 to have sufficient deformation space so that the annular filter net 110 can deform adaptively. The support plates 130 are provided to limit the upper and lower ends of the annular filter net 110 and prevent it from deforming in the axial direction.

[0028] In this embodiment, as Figure 3 shown, a spiral impeller 500 is arranged on the outer periphery of the central rotating shaft 310. The spiral impeller 500 is located inside the input end of the drainage pump 200, and the spiral impeller 500 is used to guide the fluid in the annular filter net 110 into the input end of the drainage pump 200.

[0029] It should be added that the spiral impeller 500 is provided to assist the water in the flexible filter screen 100 to accelerate into the water pipe at the input end of the drainage pump 200.

[0030] In this embodiment, as Figure 3 shown, the flexible filter screen 100 further includes support columns 140. There are multiple support columns 140, which are arranged at equal intervals circumferentially around the annular filter net 110, and both ends of the support columns 140 are fixedly connected to the corresponding support plates 130.

[0031] The support columns 140 are provided to connect the two support plates 130 together to ensure that the flexible filter screen 100 and the central rotating shaft 310 can remain concentric.

[0032] In this embodiment, a driving member 400 is arranged outside the annular filter net 110. The output end of the driving member 400 is fixedly connected to the central rotating shaft 310. The driving member 400 is specifically a driving motor, and the output shaft of the driving motor is coaxially and fixedly connected to the central rotating shaft 310.

[0033] In this embodiment, asFigure 3 As shown, the annular filter screen 110 is conical, and its cross-sectional area decreases from top to bottom.

[0034] The annular filter screen 110 is made conical to push the sludge into a sloped shape by the flexible filter screen 100, so as to increase the stability after sludge accumulation, prevent the accumulated sludge from suddenly collapsing, and avoid the flexible filter screen 100 from being suddenly buried by the collapsed sludge.

[0035] In this embodiment, wear-resistant sleeves are rotatably sleeved outside the first support rod 340 and the second support rod 350.

[0036] Rotatably sleeving wear-resistant sleeves outside the first support rod 340 and the second support rod 350 is to prevent excessive wear of the first support rod 340 and the second support rod 350.

[0037] When the wear amount of the wear-resistant rings rotatably sleeved outside the first support rod 340 and the second support rod 350 is excessive, the staff can remove the wear-resistant rings and replace them with new ones.

[0038] In this embodiment, as Figures 5 to 10 shown, the first telescopic rod 320 includes a first hydraulic cylinder 321, a first piston rod 322 and a retaining ring 323. The first hydraulic cylinder 321 is arranged on the central rotating shaft 310. The first piston rod 322 is slidably connected inside the first hydraulic cylinder 321. The retaining ring 323 is coaxially arranged outside the first piston rod 322. In the initial state, the retaining ring 323 abuts against the first hydraulic cylinder 321. The second telescopic rod 330 includes a second hydraulic cylinder 331, a second piston rod 332 and an elastic member 333. The second hydraulic cylinder 331 is arranged on the central rotating shaft 310. The inside of the second hydraulic cylinder 331 is connected to the inside of the first hydraulic cylinder 321. The second piston rod 332 is slidably connected inside the second hydraulic cylinder 331. The elastic member 333 is a compression spring. The elastic member 333 is arranged inside the second hydraulic cylinder 331, and one end of the elastic member 333 is fixedly connected to the second hydraulic cylinder 331, and the other end of the elastic member 333 is fixedly connected to the second piston rod 332. The elastic member 333 is used to make the second piston rod 332 in the maximum extended length.

[0039] When the flexible filter screen 100 is buried by sludge, under the suction of the drainage pump 200, the flexible filter screen 100 is recessed inward. At this time, the flexible filter screen 100 recessed inward pushes the second piston rod 332 to move into the second hydraulic cylinder 331. At this time, the elastic member 333 is gradually compressed, and the hydraulic oil in the second hydraulic cylinder 331 enters the inside of the first hydraulic cylinder 321, and the hydraulic oil pushes the first piston rod 322 outwards to increase the extended length of the first piston rod 322.

[0040] When the flow-through area of the flexible filter screen 100 increases, the degree of inward depression of the flexible filter screen 100 decreases. At this time, the pressure of the flexible filter screen 100 on the second piston rod 332 decreases. Under the action of the elastic member 333, the second piston rod 332 extends outward. At this time, the hydraulic oil in the first hydraulic sleeve 321 gradually enters the second hydraulic sleeve 331. Then, the first piston rod 322 contracts inward, so that the difference between the major axis and the minor axis of the ellipse formed by the deformation of the flexible filter screen 100 decreases.

[0041] A drainage method for a foundation pit includes the following steps: The first step: sinking the flexible filter screen to the bottom of the sump; The second step: starting the drainage pump and simultaneously starting the driving member.

[0042] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0043] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A drainage system for a foundation pit, characterized in that: include: Flexible filter screen, the flexible filter screen is cylindrical, the upper end of which is through and the lower end is sealed; A drainage pump, wherein an input end of the drainage pump is connected to the interior of the flexible filter screen; The support assembly comprises a central rotating shaft, a first telescopic rod, a second telescopic rod, a first support rod and a second support rod, the central rotating shaft can rotate around its axis, the axis of the central rotating shaft coincides with the axis of the flexible filter screen, and the lower end of the central rotating shaft is rotatably connected to the flexible filter screen, there are multiple first telescopic rods and multiple second telescopic rods, the multiple first telescopic rods and the multiple second telescopic rods are circumferentially equidistantly arranged around the axis of the central rotating shaft and are alternately arranged, the first support rod is rotatably abutted against the inner circumferential wall of the flexible filter screen, there are multiple first support rods, the multiple first support rods correspond one-to-one with the multiple first telescopic rods, and the middle part of the first support rod is fixedly connected to the end of the first telescopic rod away from the central rotating shaft, the second support rod is rotatably abutted against the inner circumferential wall of the flexible filter screen, there are multiple second support rods, the multiple second support rods correspond one-to-one with the multiple second telescopic rods, and the middle part of the second support rod is fixedly connected to the end of the second telescopic rod away from the central rotating shaft; In the initial state, the first telescopic rod is at the shortest length, and the second telescopic rod is at the longest length; When the second telescopic rod is shortened to a preset length, the first telescopic rod can be correspondingly extended to a preset length; Furthermore, the length variation of the second telescopic rod is negatively correlated with the flow area of ​​the flexible filter screen.

2. A drainage system for a foundation pit according to claim 1, characterized in that: The flexible filter screen includes an annular filter screen, a metal bellows and a support plate. There are two metal bellows, which are spaced apart from each other and are respectively arranged at two ends of the annular filter screen. There are two support plates, which are spaced apart from each other, wherein the upper support plate is fixedly connected to one end of the metal bellows located above and away from the annular filter screen, and the lower support plate is fixedly connected to one end of the metal bellows located below and away from the annular filter screen. A communication hole is provided on the upper surface of the support plate located above, and the communication hole is connected with the input end of the drainage pump.

3. A drainage system for a foundation pit according to claim 2, characterized in that: A spiral impeller is arranged on the outer periphery of the central rotating shaft. The spiral impeller is located in the input end of the drainage pump. The spiral impeller is used to guide the fluid in the annular filter screen to enter the input end of the drainage pump.

4. A drainage system for a foundation pit according to claim 2, characterized in that: The flexible filter screen also includes a plurality of support columns, which are arranged at equal intervals around the annular filter screen, and both ends of the support columns are fixedly connected to corresponding support plates.

5. A drainage system for a foundation pit according to claim 2, characterized in that: A driving member is arranged outside the annular filter screen, and an output end of the driving member is fixedly connected to the central rotating shaft.

6. A drainage system for a foundation pit according to claim 2, characterized in that: The annular filter screen is in a conical shape, and the cross-sectional area decreases from top to bottom.

7. A drainage system for a foundation pit according to claim 1, characterized in that: The outer rotating sleeves of the first support rod and the second support rod are provided with wear-resistant sleeves.

8. A drainage system for a foundation pit according to claim 1, characterized in that: The first telescopic rod comprises a first hydraulic sleeve, a first piston rod and a retaining ring, the first hydraulic sleeve is arranged on the central rotating shaft, the first piston rod is slidably connected in the first hydraulic sleeve, and the retaining ring is coaxially arranged outside the first piston rod; In the initial state, the retaining ring abuts against the first hydraulic sleeve.

9. A drainage system for a foundation pit according to claim 8, characterized in that: The second telescopic rod includes a second hydraulic sleeve, a second piston rod and an elastic member. The second hydraulic sleeve is arranged on the central rotating shaft. The interior of the second hydraulic sleeve is connected with the interior of the first hydraulic sleeve. The second piston rod is slidably connected in the second hydraulic sleeve. The elastic member is arranged in the second hydraulic sleeve, and one end of the elastic member is fixedly connected to the second hydraulic sleeve, and the other end of the elastic member is fixedly connected to the second piston rod. The elastic member is used to make the second piston rod at the maximum extension length.

10. A method for draining a foundation pit, characterized in that: A drainage system for a foundation pit according to any one of claims 1 to 9 is used.

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