A replaceable filter cartridge and a filter cartridge replacement method thereof

Abstract

The application discloses a replaceable filter core of a drainage pipe and a filter core replacement method thereof, relates to the technical field of slope underground water drainage pipes, and discloses the replaceable filter core of a drainage pipe and a filter core replacement method thereof.

Description

Technical Field

[0001] This invention relates to the field of underground drainage technology for slopes, and in particular to a drainage pipe with replaceable filter elements and a method for replacing the filter elements. Background Technology

[0002] Slopes are characterized by their non-slip nature when dry, and numerous drainage measures are employed in slope stabilization. Groundwater drainage pipes are among the most economical methods, effectively lowering the groundwater level. This helps control the softening of the soil and rock, and reduces the impact of sliding mass and adverse water pressure. However, drainage pipes buried in the slope are in direct contact with soil particles and are subject to multiple physical, chemical, and biological effects. After a period of operation, they frequently become clogged, gradually reducing their drainage capacity and altering the seepage field within the slope, significantly impacting slope stability, especially on slopes with high groundwater levels. Furthermore, drainage pipes are generally long and slender, with small diameters and large lengths, making cleaning difficult. Therefore, how to quickly replace easily clogged drainage pipes after a scientific assessment of their clogging status is a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0003] To address the problem of easy clogging and difficulty in cleaning existing drainage pipes, this invention provides a drainage pipe with a replaceable filter element and a method for replacing the filter element.

[0004] This invention provides the following technical solution: a drain pipe with a replaceable filter element, comprising:

[0005] A porous pipe, wherein the pipe wall is provided with multiple seepage holes, and one end of the porous pipe is a closed end and the other end is an open end;

[0006] A filter element, which is inserted into the porous tube, includes a filter screen tube, a reverse filtration layer covering the surface of the filter screen tube, and a water injection pipe disposed inside the filter screen tube.

[0007] Preferably, the two ends of the reverse filter layer protrude from the two ends of the filter tube and extend to the inner wall of the filter tube, and a pressure head pipe is provided between the two ends of the water injection pipe and the reverse filter layer.

[0008] Preferably, the filter tube is provided with a deep fixing member and an end fixing member at both ends; the end fixing member corresponds to the open end and is provided with a water outlet, the end of the water injection pipe corresponding to the open end is provided with a connector, and the connector is provided with a snap-fit ​​part; the deep fixing member is provided with a limiting groove, and the water injection pipe is provided with a sleeve that is snapped into the limiting groove.

[0009] Preferably, the inner wall of the porous tube is provided with a plurality of blind grooves extending along the axial direction of the porous tube, and a sliding plate is slidably connected in the blind groove. Both the side wall of the blind groove and the side wall of the sliding plate are provided with a plurality of side grooves. The side grooves of the blind groove and the side grooves of the sliding plate are spliced ​​together to form the seepage hole. A plurality of connecting pipes are provided between the plurality of sliding plates, and the connecting pipes are connected to the filter element.

[0010] Preferably, the open end is detachably connected to a pipe cap, the pipe cap is provided with an inner flange extending into the inside of the porous pipe, and a retaining ring is provided between the end fixing member and the inner flange.

[0011] A method for replacing a drain pipe filter element, applied to a drain pipe with a replaceable filter element, includes the following steps:

[0012] Step 1: Divide the drain pipe into multiple sections according to its length, and define the degree of blockage of each section as either blocked or unobstructed. Arrange the different degrees of blockage of the multiple drain pipe sections to form multiple working conditions.

[0013] Step 2: Based on the engineering geological characteristics of the slope, the local rainfall, and the properties of the drainage pipes, perform finite element analysis on the changes in the slope stability coefficient under the multiple working conditions to obtain the slope stability coefficient variation curve over time under each working condition.

[0014] Step 3: Determine a slope stability coefficient value as the replacement standard. If the slope stability coefficient of a certain working condition is lower than this replacement standard, replace the drainage pipe under this working condition, and complete the detection and replacement of the drainage pipe's blockage status before the time point when the slope stability coefficient is lower than this replacement standard. If there are multiple time points, the detection and replacement of the drainage pipe's blockage status should be completed before the earliest time point. During replacement, inject water into the porous pipe through the water injection pipe to flush out some of the blockage, reduce the pulling resistance, and use the pulling force on the filter element to pull out the filter element.

[0015] Preferably, in step 2, the engineering geological characteristics include soil type, soil weight, cohesion, internal friction angle, elastic modulus, Poisson's ratio, and permeability coefficient; the local rainfall is the monthly rainfall from January to December at the slope location; and the drainage pipe properties include the drainage pipe permeability coefficient, length, pipe diameter, and installation inclination angle.

[0016] Preferably, in step 2, if the soil type includes expansive soil, then the permeability coefficient of the expansive soil includes the vertical equivalent permeability coefficient and the horizontal equivalent permeability coefficient.

[0017] Preferably, the vertical equivalent permeability coefficient k v for:

[0018]

[0019] In the formula, k is the equivalent permeability coefficient; η s η r These represent the fracture ratios corresponding to the saturated and residual states of the soil, respectively; ψ represents the matrix suction; ψ s ψ r These represent the matrix suction corresponding to the saturated and residual states of the soil, respectively; δ is the fracture width; δ max δ is the maximum crack width; maxs δ maxr ρ represents the maximum crack width corresponding to the saturated and residual states of the soil, respectively; g is the density of water; K is the acceleration due to gravity; μ is the viscosity of water. Θ is the permeability coefficient corresponding to the saturated state of the soil matrix; Θ is the normalized water content; p and t are fitting parameters characterizing the relationship between soil water content and matrix suction; y is the integral variable.

[0020] Preferably, step 2 consists of the following steps:

[0021] Determine the engineering geological characteristics of the slope, the local rainfall, and the nature of the drainage pipes;

[0022] A slope model was established, and the pore water pressure distribution of the slope body throughout the year under each working condition was analyzed using finite element software.

[0023] The slope stability coefficient variation curve over time under each working condition was calculated based on the pore water pressure distribution.

[0024] The beneficial effects of this invention are: 1. By using a combination of porous tubes and filter elements, the filter element can be pulled out for cleaning or replacement after clogging, which solves the problem of difficult drainage pipe clogging in the prior art; a water injection pipe is set inside the filter element, and water is injected into the depth of the porous tube through the water injection pipe to balance the pressure difference between the depth of the porous tube and the external environment when the filter element is pulled out, and to increase the water pressure to push the filter element out of the porous tube and flush out some of the clogging material; after the sliding plate is replaced with the filter element, some of the clogging material is carried out with the sliding plate, and the displacement between the two side grooves that splice the seepage hole destroys the stability of the clogging material in the seepage hole, leaving it in the blind groove. The blockages in the sidewall grooves are more easily flushed out; the above measures solve the problem of how to conveniently and quickly replace the drainage pipes and more effectively clean the blockages; 2. The filter replacement method divides the drainage pipe into multiple sections according to length, analyzes the slope stability coefficient change curve over time under different blockage conditions, and improves the calculation formula for the equivalent permeability coefficient of the soil, which is more in line with the soil characteristics and the analysis results are more realistic and reliable. Thus, it solves the problem of when the drainage pipe needs to be replaced under what blockage conditions and within what time period to complete the replacement without affecting the slope stability. Attached Figure Description

[0025] Figure 1 This is an axial cross-sectional view of one embodiment of a drainage pipe.

[0026] Figure 2 This is a radial cross-sectional view of one embodiment of a drain pipe.

[0027] Figure 3 This is a schematic diagram of one embodiment of a porous tube.

[0028] Figure 4 This is a schematic diagram of one embodiment of a water injection pipe.

[0029] Figure 5 This is a cross-sectional view of the slope model.

[0030] Figure 6 This is a graph showing the change in elastic modulus.

[0031] Figure 7 This is a graph showing the change in permeability coefficient.

[0032] Figure 8 This is a graph showing rainfall statistics.

[0033] Figure 9 This is a diagram showing the pore water pressure distribution on the slope under working condition S1 on day 240.

[0034] Figure 10 This is a graph showing the change in pore water pressure at the endpoint.

[0035] Figure 11 This is a graph showing the variation of the slope stability coefficient.

[0036] Reference numerals: 10-Porous pipe, 11-Seepage hole, 12-Closed end, 13-Open end, 14-Blind groove, 15-Sliding plate, 16-Connecting pipe, 17-Side groove, 21-Filter screen pipe, 211-Deep fixing component, 212-End fixing component, 213-Outlet, 22-Reverse filter layer, 23-Water injection pipe, 231-Connector, 232-Snap-fit ​​part, 233-Pipe sleeve, 24-Pressure head pipe, 30-Pipe cap, 31-Retaining ring. Detailed Implementation

[0037] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings and reference numerals, so that those skilled in the art can implement them after reading this specification. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0038] Example 1

[0039] This embodiment provides, for example Figure 1-4 The drain pipe shown includes a replaceable filter element, a porous pipe 10, a filter element, and a pipe cap 30.

[0040] The porous pipe 10 is inserted into a borehole on the slope, possessing sufficient structural strength to prevent soil damage to the drainage pipe and protecting its internal structure. The porous pipe 10 has multiple seepage holes 11 on its wall, with one end being a closed end 12 and the other an open end 13. The closed end 12 can have a conical structure for easy insertion into the borehole. In existing technology, the porous pipe 10 is installed at an upward angle. If the drainage pipe is not blocked, groundwater is introduced into the porous pipe 10 through the seepage holes 11 and then flows by gravity to the open end to exit the slope, thus lowering the groundwater level on the slope. With increasing usage time, the soil within the slope gradually fills the borehole, burying and compacting the drainage pipe. Silt gradually enters the drainage pipe from the seepage holes 11, causing blockage. A replaceable filter element is inserted into the porous tube 10. The filter element occupies the internal space of the porous tube 10 in advance to prevent the blockage from being occupied and difficult to clean. During the drainage process, the blockage gradually clogs the filter element. The filter element can be pulled out for cleaning or replacement, which can solve the problem of difficult drainage pipe blockage. However, how to determine when the filter element needs to be replaced and how to replace it conveniently and quickly have become new problems.

[0041] In this embodiment, the filter element includes a filter screen tube 21, a reverse filter layer 22 covering the surface of the filter screen tube 21, and a water injection pipe 23 disposed inside the filter screen tube 21. The filter screen tube 21 is the main structure of the filter element and can be made of porous materials such as porous resin. Compared with slopes, the filter screen tube 21 has higher drainage efficiency. The reverse filter layer 22 can be made of geotextile and covers the outer surface of the filter screen tube 21 to perform reverse filtration and delay the time when the filter element is blocked by silt. Specifically, the two ends of the reverse filter layer 22 protrude from the two ends of the filter screen tube 21 and extend to the inner wall of the filter screen tube 21. A pressure head pipe 24 is provided between the two ends of the water injection pipe 23 and the reverse filter layer 22. After the reverse filter layer 22 covers the outer surface of the filter screen tube 21, its two ends are inserted into the interior of the filter screen tube 21 and pass through the water injection pipe 23. The pressure head pipe 24 then presses the reverse filter layer 22, the filter screen tube 21, and the water injection pipe 23 together.

[0042] The water injection pipe 23 connects the internal space between the filter element and the closed end 12. Water is injected into the closed end 12 through the water injection pipe 23 to balance the pressure difference between this internal space and the external environment when the filter element is pulled out, and to increase the water pressure to push the filter element out of the porous tube. At the same time, it flushes out some of the blockages between the filter element and the porous tube 10 and in the seepage holes 11. Further, the filter screen tube 21 is provided with a deep fixing member 211 and an end fixing member 212 at both ends to fix the reverse filter layer 22 from both ends. The end fixing member 212 corresponds to the open end 13 and is provided with a water outlet 213. The end of the water injection pipe 23 corresponding to the open end 13 is provided with a connector 231 for connecting a water source. The connector 231 is also provided with a snap-fit ​​part 232. In this embodiment, the snap-fit ​​part 232 is a stepped structure provided on the outer wall of the connector 231. The snap-fit ​​part 232 is clamped by a clamp, which can also provide the pulling force to pull out the filter element. The deep fixing member 211 is provided with a limiting groove 214. The water injection pipe 23 is threadedly connected to a sleeve 233, which is engaged in the limiting groove 214 to prevent the water injection pipe 23 from coming out of the filter screen pipe 21. Pulling the water injection pipe 23 outward can also pull out the entire filter element. The open end 13 can also be detachably connected to a pipe cap 30. The pipe cap 30 is provided with an inner flange extending into the porous pipe 10. A retaining ring 31 is provided between the end fixing member 212 and the inner flange. After the filter element is inserted into the porous pipe 10, the inner flange of the pipe cap 30 prevents the filter element from coming out of the porous pipe 10, and the retaining ring 31 fills the length difference between the filter element and the porous pipe 10.

[0043] Furthermore, the inner wall of the porous pipe 10 is provided with multiple blind grooves 14 extending along the axial direction of the porous pipe 10. A sliding plate 15 is slidably connected within each blind groove 14. Both the side walls of the blind grooves 14 and the side walls of the sliding plate 15 are provided with multiple side grooves 17. The side grooves of the blind grooves 14 and the side grooves of the sliding plate 15 are joined together to form the seepage hole 11. All side grooves 17 are through grooves. During use, the seepage hole 11 is filled with silt. When the sliding plate 15 slides relative to the blind grooves 14, displacement occurs between the two side grooves 17 that form the seepage hole 11, thereby disrupting the stability of the silt inside the seepage hole 11. In the prior art, as the usage time increases, the soil of the slope gradually fills the boreholes, burying and compacting the drainage pipes. When water is injected into the porous pipe 10, very high pressure is required to flush away the silt inside the seepage hole 11, and generally only the shallow silt inside the seepage hole 11 can be cleaned. Therefore, by disrupting the stability of the blockage, injecting water deep into the porous pipe 10 during filter replacement makes it easier to flush away the blockage in the side grooves of the blind channel. Simultaneously, multiple connecting rings 16 are provided between the multiple sliding plates 15. The sliding plates 15 are arranged circumferentially along the porous pipe, and the connecting rings 16 are located on the inner surface of the sliding plates 15. The multiple sliding plates 15 are connected to the filter element through the multiple connecting rings 16 and are replaced along with the filter element. Some of the blockage is discharged from the porous pipe 10 along with the sliding plates 15.

[0044] Example 2

[0045] A method for replacing the filter element in a drainage pipe is provided, applied to a drainage pipe with a replaceable filter element as described in Example 1. One application scenario of this example uses a branch canal slope in an irrigation district as a model, with the slope profile shown below. Figure 5 As shown.

[0046] The replacement method includes the following steps:

[0047] Step 1: Divide the drainage pipe into three sections of equal length: end, middle, and deep section. The end section faces the slope surface. Define the blockage level of each drainage pipe section as having only two states: blocked or unobstructed. The different blockage levels of multiple drainage pipe sections are arranged to form S1-8 working conditions, as follows:

[0048] S1, the deep, middle and end sections are all unobstructed;

[0049] S2: Deep and middle sections are unobstructed, but the ends are blocked.

[0050] S3: Deeply unobstructed, centrally blocked, and unobstructed at the ends;

[0051] S4, deep section unobstructed, middle and end sections blocked;

[0052] S5, deep blockage, clear in the middle and ends;

[0053] S6, deep blockage, unobstructed middle section, and end blockage;

[0054] S7, deep and middle sections are blocked, but the ends are clear;

[0055] S8 is clogged in the deep, middle and end parts.

[0056] Various working conditions such as Figure 5 As shown in the upper right corner, the white box indicates a smooth flow, and the black box indicates a blocked flow.

[0057] Step 2: Based on the engineering geological characteristics of the slope, the local rainfall, and the properties of the drainage pipes, establish a model and perform finite element analysis on the changes in the slope stability coefficient under the multiple working conditions to obtain a graph showing the change of the slope stability coefficient over time under each working condition.

[0058] First, determine the engineering geological characteristics of the slope, the local rainfall, and the properties of the drainage pipes. The engineering geological characteristics are shown in Table 1, including soil type, soil weight, cohesion, internal friction angle, elastic modulus, Poisson's ratio, and permeability coefficient.

[0059]

[0060] In this model, the soil and rock types include expansive soil and strongly weathered sandstone. The upper layer of the slope is a 9m thick expansive soil layer, and the lower layer is a 10m thick strongly weathered sandstone. It should be noted that the elastic modulus and permeability coefficient of the expansive soil layer are not specified in Table 1, and these values ​​are not constant.

[0061] The elastic modulus of expansive soil layers is calculated using a semi-empirical formula from existing technology, as follows:

[0062]

[0063] Where E unsat E is the elastic modulus in the unsaturated state. sat Let be the elastic modulus under saturation, and α and β be empirical values, taken as α = 0.1 and β = 2. a u w These are the pore gas pressure and pore water pressure, respectively, P a Let S be the atmospheric pressure and S be the degree of saturation. The calculation results are as follows: Figure 6 As shown, Figure 6 The horizontal axis represents matrix suction, and the vertical axis represents the elastic modulus under unsaturated conditions.

[0064] The permeability coefficient of expansive soil layers includes the vertical equivalent permeability coefficient and the horizontal equivalent permeability coefficient. Influenced by the atmosphere, the shallow surface layer of expansive soil contains complex fractures, predominantly vertical, which provide a preferential path for water infiltration and can significantly alter the original seepage field. Therefore, under the influence of fractures, the vertical equivalent permeability coefficient k... v The calculation formula is as follows, as it is affected by the fracture ratio, the permeability coefficient of the fracture, and the permeability coefficient of the matrix:

[0065]

[0066] In the formula, k is the equivalent permeability coefficient; η s η r These represent the fracture ratios corresponding to the saturated and residual states of the soil, respectively; ψ represents the matrix suction; ψ s ψ r These represent the matrix suction corresponding to the saturated and residual states of the soil, respectively; δ is the fracture width; δ max δ is the maximum crack width; maxs δ maxr ρ represents the maximum crack width corresponding to the saturated and residual states of the soil, respectively; g is the density of water; K is the acceleration due to gravity; μ is the viscosity of water. Θ is the permeability coefficient corresponding to the saturated state of the soil matrix; Θ is the normalized water content; p and t are fitting parameters characterizing the relationship between soil water content and matrix suction; y is the integral variable.

[0067] The curve of permeability coefficient versus matrix suction obtained from the above formula is shown below. Figure 7 As shown, Figure 7 The horizontal axis represents matrix suction, and the vertical axis represents the permeability coefficient, k. c Let k be the permeability coefficient of the fracture. m Let be the permeability coefficient of the matrix. Assume a conductivity of 1, and the horizontal equivalent permeability coefficient is the same as the vertical equivalent permeability coefficient.

[0068] The rainfall at the location mentioned refers to the monthly rainfall from January to December of a given year at the slope location, such as... Figure 8 As shown, Figure 8 The horizontal axis represents the month, and the vertical axis represents the rainfall. The drainage pipe is 12m long and 0.1m in diameter, installed at an angle of 7° at the bottom of the expansive soil layer, with a permeability coefficient of 2×10⁻⁶. -4 m / s.

[0069] Then, excluding the influence of evaporation, a slope model was established based on the above parameters, and the pore water pressure distribution of the slope throughout the year under each working condition was analyzed using the finite element software SIGMA / W. Taking working condition S1 as an example, the pore water pressure distribution diagram of the slope on day 240 is shown below. Figure 9As shown. Next, select the end point deep within the drain pipe, away from the end, and analyze the pore water pressure variation curve at that end point over time under each operating condition, as shown. Figure 10 As shown.

[0070] Depend on Figure 10 It can be seen that the change in pore water pressure at the endpoint goes through three stages:

[0071] Phase 1 (January to May). Affected by rainfall intensity, pore water pressure fluctuates continuously, but its value is always negative. The soil is not saturated, and the drainage pipes are not functioning. Since the initial conditions are the same, the pore water pressure is the same under different siltation conditions during this phase.

[0072] The second phase (June-July). As rainfall continues, the groundwater level rises to the drainage pipes, which then begin to function. However, due to varying siltation conditions, the pore water pressure differs significantly. In condition S1, the pore water pressure remains zero, consistent with the boundary conditions. In other conditions, the pore water pressure is positive, indicating existing water accumulation and the drainage pipes are functioning, but their capacity seems somewhat insufficient. For conditions S2 and S5, the maximum pore water pressure occurs at 210 days, closely related to rainfall. In conditions S3, S4, and S6-S8, the pore water pressure exhibits a lag effect, with its maximum value occurring at 220 days, indicating that the drainage pipes are less effective under these conditions.

[0073] The third stage (August to December) sees a significant decrease in rainfall intensity and a gradual drop in water level to the height of the drainage pipes. The drainage pipes lose their function again, but due to the varying drainage effects of different blockage conditions in the previous stage, there are differences in pore water pressure during this stage.

[0074] Finally, excluding the influence of cracks on soil strength, the slope stability coefficient under each working condition was calculated as a function of time based on the pore water pressure distribution. Figure 11 As shown; the calculation method for the slope stability coefficient is based on existing technology. Figure 11 Different background colors are used to more intuitively represent the stability of the slope, from top to bottom: stable, basically stable, slightly unstable, and unstable.

[0075] Step 3: The standard slope stability coefficient is 1.05. When the slope stability coefficient is less than 1.05, the slope will enter a sub-stable or even unstable state. If the slope stability coefficient of a certain working condition is lower than this replacement standard, the drainage pipe under this working condition should be replaced. The detection and replacement of the drainage pipe's blockage status should be completed before the time point when the slope stability coefficient falls below this replacement standard. If there are multiple time points, the detection and replacement of the drainage pipe's blockage status should be completed before the earliest time point. In this embodiment, under the five working conditions S2, S3, S4, S6, and S7, the slope stability coefficient has a period of falling below 1.05. Due to the lag effect of pore water pressure, the time points generally occur after July when the rainfall is the largest. The earliest time point when it falls below the replacement standard is the 200th day. The detection and replacement of the drainage pipe's blockage status should be completed before the 200th day. During testing, check whether the end and middle of the drain pipe are blocked; when replacing, inject water into the porous pipe through the water injection pipe and pull the filter element to flush out some of the blockage, reduce the pulling resistance, and use the pulling force on the filter element to pull it out.

[0076] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A drain pipe with a replaceable filter element, characterized in that, include: A porous pipe (10) has multiple seepage holes (11) on its wall. One end of the porous pipe (10) is a closed end (12) and the other end is an open end (13). The filter element is inserted into the porous tube (10). The filter element includes a filter screen tube (21), a reverse filtration layer (22) covering the surface of the filter screen tube (21), and a water injection pipe (23) disposed inside the filter screen tube (21). The water injection pipe (23) is used to connect the internal space between the closed end (12) and the filter element, and water is injected into the closed end (12) through the water injection pipe (23). The filter screen tube (21) is provided with a deep fixing member (211) and an end cap at both ends. The end fixing member (212) corresponds to the open end (13) and is provided with a water outlet (213). The end of the water injection pipe (23) corresponding to the open end (13) is provided with a connector (231). The connector (231) is provided with a snap-fit ​​part (232). The deep fixing member (211) is provided with a limiting groove (214). The water injection pipe (23) is provided with a pipe sleeve (233) that is locked in the limiting groove (214).

2. The drain pipe with a replaceable filter element according to claim 1, characterized in that, The two ends of the reverse filter layer (22) protrude from the two ends of the filter tube (21) and extend to the inner wall of the filter tube (21). A pressure head tube (24) is provided between the two ends of the water injection pipe (23) and the reverse filter layer (22).

3. A drain pipe with a replaceable filter element according to claim 1, characterized in that, The inner wall of the porous tube (10) is provided with a plurality of blind grooves (14) extending along the axial direction of the porous tube (10). A sliding plate (15) is slidably connected in the blind groove (14). Both the side wall of the blind groove (14) and the side wall of the sliding plate (15) are provided with a plurality of side grooves (17). The side grooves of the blind groove (14) and the side grooves of the sliding plate (15) are spliced ​​together to form the seepage hole (11). A plurality of connecting pipes (16) are provided between the plurality of sliding plates (15). The connecting pipes (16) are connected to the filter element.

4. A drain pipe with a replaceable filter element according to claim 1, characterized in that, The open end (13) is detachably connected to a tube cap (30), the tube cap (30) is provided with an inner flange extending into the inside of the porous tube (10), and a retaining ring (31) is provided between the end fixing member (212) and the inner flange.

5. A method for replacing a drain pipe filter element, characterized in that, A drain pipe for use with a replaceable filter element as described in any one of claims 1 to 4 comprises the following steps: Step 1: Divide the drain pipe into multiple sections according to its length, and define the degree of blockage of each section as either blocked or unobstructed. Arrange the different degrees of blockage of the multiple drain pipe sections to form multiple working conditions. Step 2: Based on the engineering geological characteristics of the slope, the local rainfall, and the properties of the drainage pipes, perform finite element analysis on the changes in the slope stability coefficient under the multiple working conditions to obtain the slope stability coefficient variation curve over time under each working condition. Step 3: Determine a slope stability coefficient value as the replacement standard. If the slope stability coefficient of a certain working condition is lower than this replacement standard, replace the drainage pipe under this working condition, and complete the detection and replacement of the drainage pipe's blockage status before the time point when the slope stability coefficient is lower than this replacement standard. If there are multiple time points, the detection and replacement of the drainage pipe's blockage status should be completed before the earliest time point. During replacement, inject water into the porous pipe through the water injection pipe to flush out some of the blockage, reduce the pulling resistance, and use the pulling force on the filter element to pull out the filter element.

6. A method for replacing a drain pipe filter element according to claim 5, characterized in that, In step 2, the engineering geological characteristics include soil type, soil weight, cohesion, internal friction angle, elastic modulus, Poisson's ratio, and permeability coefficient; the local rainfall is the monthly rainfall from January to December at the slope location; the drainage pipe properties include the drainage pipe permeability coefficient, length, pipe diameter, and installation inclination angle.

7. A method for replacing a drain pipe filter element according to claim 6, characterized in that, In step 2, if the soil type includes expansive soil, the permeability coefficient of the expansive soil includes the vertical equivalent permeability coefficient and the horizontal equivalent permeability coefficient.

8. A method for replacing a drain pipe filter element according to claim 7, characterized in that, The vertical equivalent permeability coefficient for: ； In the formula, k is the equivalent permeability coefficient; , These represent the fracture ratios corresponding to the saturated and residual states of the soil, respectively. For matrix suction; , These represent the matrix suction corresponding to the saturated and residual states of the soil, respectively. The width of the crack; Maximum crack width; , These represent the maximum crack widths corresponding to the saturated and residual states of the soil, respectively. The density of water; It is the acceleration due to gravity; This is a correction factor; The viscosity of water; This represents the permeability coefficient corresponding to the saturated state of the soil matrix. Normalized moisture content; , y is the fitting parameter characterizing the relationship between soil moisture content and matrix suction; y is the integral variable.

9. A method for replacing a drain pipe filter element according to claim 5, characterized in that, The specific steps of step 2 are as follows: Determine the engineering geological characteristics of the slope, the local rainfall, and the nature of the drainage pipes; A slope model was established, and the pore water pressure distribution of the slope body throughout the year under each working condition was analyzed using finite element software. The slope stability coefficient variation curve over time under each working condition was calculated based on the pore water pressure distribution.

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