Combined sand well drainage structure and its construction method applicable to high slopes

Abstract

This invention provides a combined sand well drainage structure suitable for high slopes. The combined well drainage structure includes a row of vertical sand wells arranged along the slope line within the slope and a siphon drainage structure at the bottom of the vertical sand wells. Each vertical sand well includes a vertical well hole, a permeable pipe, and a sand and gravel filter layer; the permeable pipe is filled with sand and gravel. The siphon drainage structure includes a siphon guide pipe, a horizontal drainage well structure, and an inclined drainage pipe. This invention utilizes the sand wells to collect rainwater from high slopes. Under gravity, the rainwater flows into the horizontal drainage wells. The groundwater collected in the horizontal drainage wells is discharged through the siphon guide pipe from the lowest drainage hole of the support structure, thus creating negative pressure within the horizontal drainage wells and further accelerating the drainage from the vertical sand wells. This invention reduces the construction difficulty of deep drainage structures on high slopes and ensures that groundwater accumulated due to rainfall and underground pipe leakage can be discharged promptly and quickly.

Description

Technical Field

[0001] This invention relates to the field of landslide prevention and control, specifically a combined sand well drainage structure and its construction method suitable for high slopes. This drainage system can achieve rapid drainage from deep parts of high slopes, and is especially suitable for the treatment of high embankment slopes in areas with large rainfall. Technical Background

[0002] In slope engineering, the principle of "controlling water before controlling slope" should be strictly implemented. Many slope disasters are closely related to rainfall, and the long-term accumulation of groundwater will lead to increased slope sliding force and reduced shear strength. Therefore, the rapid and efficient drainage of groundwater from slopes is a key issue in landslide disaster control engineering.

[0003] Currently, the commonly used deep drainage measures for high slopes are vertical drainage wells combined with drainage tunnels. However, vertical drainage wells are prone to siltation and are difficult to maintain. Furthermore, in cases of heavy rainfall or large groundwater recharge, the drainage capacity of vertical drainage wells is limited, preventing the timely removal of deep groundwater from high slopes and affecting slope stability. Drainage tunnels are difficult and costly to construct, causing significant environmental damage and exacerbating soil erosion, further deteriorating slope stability. Some experts have proposed horizontal sand well drainage methods, but these have limited drainage capacity and are inconvenient to maintain. Others have proposed a negative pressure drainage method using boreholes; however, this method requires numerous horizontal boreholes in the lower part of the slope, making construction difficult and causing significant slope disturbance. Therefore, there is an urgent need for a deep drainage measure for high slopes that is fast, low-cost, and easy to construct. Summary of the Invention

[0004] This invention addresses the shortcomings and defects of existing technologies by providing a combined sand well drainage structure and its construction method suitable for high slopes. This drainage structure is easy to construct and can ensure that groundwater accumulated under the influence of rainfall, underground pipe leakage, etc., can be discharged in a timely and rapid manner, thereby improving the safety of high slopes.

[0005] To address the aforementioned problems, this invention provides a combined sand well drainage structure suitable for high slopes, comprising a slope and a slope support structure. A drainage hole is provided at the bottom of the slope support structure. The combined well drainage structure includes a row of vertical sand well structures arranged along the slope surface line within the slope and a siphon drainage structure at the bottom of the row of vertical sand well structures. The vertical sand well structure includes vertical well holes drilled vertically from the slope surface or top towards the slope body, permeable pipes placed vertically within the vertical well holes, and a sand and gravel filter layer filled between the permeable pipes and the inner wall of the vertical well holes. The permeable pipes are filled with sand and gravel. The siphon drainage structure includes a siphon guide pipe, a horizontal drainage well structure, and an inclined drainage pipe. The horizontal drainage well structure includes horizontal well holes drilled horizontally from the slope surface towards the slope body and clay pipes arranged along the horizontal well holes. The earthen pipe is wrapped with a reverse filter geotextile. Both the horizontal well and the earthen pipe slope downwards from the slope surface towards the slope body. The horizontal well is connected to a row of vertical wells. The earthen pipe has holes corresponding to the positions of each permeable pipe. The lower end of each permeable pipe is connected to the holes on the earthen pipe, and a permeable plate is provided at the connection point. The lower end of the earthen pipe away from the slope surface is provided with a pipe end cap. The upper end of the earthen pipe near the slope surface is connected to the inclined drainage pipe through an adapter, and a water-stop rubber cap is provided at the connection point. The inclined drainage pipe slopes downwards from the upper end of the earthen pipe near the slope surface to the lowest drainage hole. The siphon water guide pipe is located inside the earthen pipe and the inclined drainage pipe. The siphon water guide pipe extends from the lower end of the earthen pipe to the upper end of the earthen pipe, passes through the water-stop rubber cap, and extends along the inclined drainage pipe to the lowest drainage hole, where it is connected.

[0006] The preferred technical solution of the present invention is as follows: the siphon water guide pipe has an enlarged diameter section in the inlet area near the lower end of the clay pipe, the drain end of the siphon water guide pipe extends from the lowest drain hole, and the lowest end of the siphon water guide pipe is higher than the height of the lowest drain hole; the diameter of the water guide pipe is 5-10mm, the enlarged diameter section is enlarged to 10-20mm, and the enlarged diameter section is 1 / 5 to 2 / 5 of the total length of the water supply pipe.

[0007] The preferred technical solution of the present invention is as follows: the slope surface is provided with multiple sets of combined sand well drainage structures. Each set of combined sand well drainage structures includes multiple vertical sand well structures and one horizontal drainage well structure. The multiple vertical sand well structures are arranged in a row and are connected to the horizontal drainage well structure. The spacing between two adjacent sand well drainage structures in the same set and between two adjacent sets of sand well drainage structures is 1.5 to 3m.

[0008] The preferred technical solution of this invention is as follows: the permeable pipe adopts a plastic sleeve, and the pipe wall is covered with permeable holes of 15-25mm in diameter at intervals of 15-30cm. A geotextile bag is installed inside the permeable pipe, and the sand and gravel are filled inside the geotextile bag. A cap is provided at the opening of the permeable pipe, and the cap is threaded to the opening of the permeable pipe. The lower end of each permeable pipe is threaded to a clay pipe, and the permeable plate at the connection is bonded to the lower end of the permeable pipe with epoxy adhesive. The permeable plate is a sand-based permeable plate or a granite permeable plate. The siphon water guide pipe is a water guide pipe made of PA material. The adapter is a plastic connector, and its two ends are threaded to or bonded to the clay pipe and the inclined drainage pipe, respectively. The inclined drainage pipe adopts a plastic sleeve. The sealing end cap is made of sintered clay material and is connected to the end of the clay pipe with epoxy resin.

[0009] The preferred technical solution of the present invention is as follows: the slope protection structure is a retaining wall or a pile wall; the vertical well is drilled by a spiral drilling rig; the horizontal well is drilled by a directional drilling rig before the construction of the slope protection structure, with an inclination angle of 3 to 7°, and after the drilling is completed, the borehole of the horizontal well is buried in the backfill soil layer.

[0010] This invention also provides a construction method for a combined sand well drainage structure suitable for high slopes, the specific construction steps of which are as follows:

[0011] S1: Measurement and positioning. Based on the original design of the slope support structure, determine the location of the combined sand well drainage structure. The combined sand well drainage structure includes multiple vertical sand well structures and one horizontal drainage well structure. The multiple vertical sand well structures are arranged in a row along the slope line of the slope. The horizontal drainage well structure is arranged at the bottom of the row of vertical sand well structures, and the setting height of the horizontal drainage well structure is higher than the setting height of the lowest drainage hole of the slope support structure.

[0012] S2: Before the construction of the slope support structure, horizontal well holes are drilled directionally from the slope surface at the bottom of the slope towards the slope body. The horizontal well holes are inclined downwards from the slope surface towards the slope body at an angle of 3 to 7°. One end of the clay pipe is sealed with a pipe end cap, and holes with internal thread interfaces are opened at the positions of each vertical sand well structure on the clay pipe. Then, the clay pipe is wrapped with a reverse filter geotextile, and holes are also opened at the positions of the reverse filter geotextile corresponding to the openings in the clay pipe. Then, the siphon water guide pipe is placed inside the clay pipe. A perforated water-stop rubber cap is provided at the open end of the clay pipe, and the siphon water guide pipe extends out from the hole in the water-stop rubber cap. Finally, an adapter is installed at the unsealed end of the clay pipe.

[0013] S3. Drill a hole from the design position of the lowest drainage hole of the slope support structure to the highest end of the horizontal well hole, and connect the drilling hole with the horizontal well hole. Install an inclined drainage pipe in the drilling hole. Connect the upper end of the inclined drainage pipe to the adapter. Pull out the siphon water guide pipe and extend it along the inclined drainage pipe from the position of the lower drainage hole.

[0014] S4. Use a spiral drilling rig to drill vertical wells from the top or surface of the slope. The vertical wells are arranged in a row along the horizontal wells. Each vertical well is drilled to the top of the horizontal well and connected to it. A permeable pipe of the same length is installed in each vertical well. The bottom end of each permeable pipe is bonded with a permeable plate by epoxy resin. Each permeable pipe has an external threaded connection port at the bottom end. The permeable pipe is lowered into the corresponding vertical well and the bottom end is threaded to the corresponding hole on the earthenware pipe. A sand and gravel filter layer is filled between the permeable pipe and the wall of the vertical well. After the permeable pipe is installed, geotextile bags filled with sand and gravel are placed in layers inside the permeable pipe and covered with a cap.

[0015] S5: After the construction of the vertical sand well structure and the horizontal drainage well structure is completed, the backfill soil layer will completely bury the horizontal drainage well structure and the inclined drainage pipe, and the slope support structure will be constructed. When constructing the lowest drainage hole of the slope support structure, the corresponding siphon water pipe will be pulled out from the lowest drainage hole.

[0016] The preferred technical solution of this invention is as follows: In step S1, multiple sets of combined sand well drainage structures are provided, and these multiple sets of combined sand well drainage structures are distributed in parallel on the slope. The number N of all vertical sand well structures on the slope is based on the slope's catchment area and the amount of precipitation Q. r The drainage capacity q of a single vertical sand well structure is determined as follows:

[0017]

[0018] Q r =βrA②

[0019] q=kiA0③

[0020] In the formula: β is the slope infiltration coefficient, which is usually taken as 0.5 to 0.8;

[0021] r represents rainfall intensity (mm / d); A represents the slope catchment area.

[0022] k is the permeability coefficient of the sand well; A0 is the cross-sectional area of ​​the sand well;

[0023] i is the hydraulic gradient, calculated based on the water level difference in the soil surrounding the well and the length of the water flow path.

[0024] A preferred technical solution of this invention: N vertical sand well structures are arranged in a square, divided into squares. The resulting single-hole units are then converted from polygons to circles according to the principle of equal area. The equivalent radius r after conversion is... e The relationship between the spacing l of the vertical sand well structure and the vertical sand well structure is as follows:

[0025]

[0026] The preferred technical solution of this invention is as follows: To prevent the descent speed of the guide pipe at the bend in the horizontal drainage well structure from exceeding the siphon rise speed and creating a vacuum zone, the diameter of the guide pipe in the suction section of the guide pipe in the horizontal drainage well structure is increased to enhance the siphon rise speed; to ensure continuous water flow and prevent the creation of a vacuum zone at the bend in the guide pipe, the optimal head H of the siphon guide pipe is... c The following requirements must be met to calculate Hc using the following formula:

[0027]

[0028] In the formula: H1 is the head difference between the two ends of the siphon pipe, which can be regarded as the height of the sewer pipe under heavy rain conditions; D is the diameter of the siphon pipe after the diameter reduction section is enlarged; d is the original diameter of the siphon pipe; l Dup Increase the length of the diameter section of the siphon water supply pipe; dup The length of the original diameter section of the siphon water supply pipe; down λ is the length of the siphon drain pipe; dt This refers to the head loss along the original diameter section of the siphon water pipe; ζ dt This refers to the local head loss in the original diameter section of the siphon water pipe; λ Dup For the head loss along the section where the diameter of the siphon water supply pipe increases; ζ Dup This refers to the local head loss in the original diameter section of the siphon water pipe; This represents the maximum head of the siphon water pipe under atmospheric pressure.

[0029] Based on the calculated optimal head H of the siphon water pipe c， The inclination angle α of the siphon water pipe is calculated using trigonometric functions;

[0030]

[0031] The preferred technical solution of the present invention is as follows: the permeable pipe in step S3 is a plastic pipe, with permeable holes of 15-25mm in diameter arranged at intervals of 15-30cm on the pipe wall. After the geotextile bag inside the pipe reaches the end of its service life, it is directly extracted and replaced to ensure the vertical sand well structure's ability to collect groundwater and drain water; the siphon water guide pipe in the horizontal drainage well uses siphon action to drain water. When the head H0 of the siphon water guide pipe is greater than or equal to 4m, a pump is installed at the outlet of the siphon water guide pipe to pump out the water accumulated in the horizontal drainage well.

[0032] The geotextile bags are required to collect groundwater around the vertical sand wells and then, through gravity, channel the groundwater into the horizontal drainage well structure. For the sand filling, the particle size should generally be between 0.25 and 5 mm, with particles between 0.5 and 2 mm accounting for more than 50%. The content of fine sand (e.g., particle size <0.1 mm) should be <5%, and the mud content (particle size <0.075 mm) should be <3%. The permeability coefficient should be 1×10⁻⁶. -2 ~1×10 -1 cm / s, the non-uniformity coefficient is controlled within C u =d 60 / d 10 ≤5. The terracotta pipe is made of sintered terracotta material. When saturated with groundwater, the small gaps between the terracotta particles are filled with water, achieving water permeability but air impermeability. In cases of abundant groundwater, while allowing surrounding groundwater to flow in, it effectively reduces gas in the horizontal drainage well. Simultaneously, the geotextile filter wrapped around the outside of the terracotta pipe effectively prevents silt from flowing into it, thus preventing blockage.

[0033] To ensure the proper functioning of the siphon, the horizontal drainage well structure must not generate a large number of air bubbles, and the head must be within 4 meters. To prevent a vacuum zone from forming between the inlet and outlet pipes within the PA water guide pipe, the upward velocity of the water flow in the inlet pipe needs to be increased. Therefore, the diameter of the bottom end of the PA water guide pipe is enlarged, with the enlarged section being approximately 1 / 5 of the total length. When the flow velocity in the PA water guide pipe exceeds the water collection velocity in the vertical sand well, negative pressure will be generated in the horizontal drainage well, further accelerating the water collection velocity in the vertical sand well until the water level drops to the designated level.

[0034] The beneficial effects of this invention are:

[0035] (1) This invention includes vertical sand wells and horizontal drainage wells. The vertical sand wells are distributed on the slope and can collect the groundwater accumulated in the slope. The collected groundwater enters the sleeve of the horizontal drainage well. Since the end of the horizontal drainage well away from the slope is lower, the water entering the sleeve of the horizontal drainage well gathers at the lower end and enters the PA water guide pipe in the sleeve of the horizontal drainage well through the lower end. When the PA water guide pipe reaches the highest point of the horizontal drainage well, it extends downwards to the drainage hole at the lowest point of the slope support structure. One section of the PA water guide pipe in the horizontal drainage well is inclined upwards to form an upper water pipe section, and the other section in the inclined drainage pipe is inclined downwards to form a lower water pipe section. The two pipe sections can form a siphon structure, which continuously discharges water using the siphon principle. This structure can efficiently discharge the groundwater accumulated on the high slope and reduce the harm of groundwater to the slope stability.

[0036] (2) The vertical sand well of the present invention is constructed by a spiral drilling rig, and the horizontal drainage well is constructed by a directional drilling rig. The construction is convenient, the project cost is low, the construction difficulty is small, and the disturbance to the slope is small.

[0037] (3) The present invention provides a plastic sleeve in the vertical sand well and fills the plastic sleeve with sandbags to form a core extraction vertical sand well. When the sand well is blocked and the ability to collect groundwater is weakened, the sleeve can be extracted to replace the geotextile bag and fill with sand, thereby achieving long-term effectiveness of the vertical sand well.

[0038] (4) The horizontal drainage well of the present invention uses a sintered clay material sleeve, which can achieve water permeability but not air permeability after being soaked in groundwater to saturate it. This effectively reduces the gas in the sleeve, ensures the siphon effect of the water pipe, and makes it easier to generate negative pressure in the sintered clay material sleeve, thereby accelerating the collection of groundwater in the vertical sand well.

[0039] (5) Due to the siphon effect, the water flow into the drain pipe may cause the downward water flow velocity to be greater than the upward water flow velocity due to gravity, thus creating a vacuum zone (when the water head velocity shared by gravity is greater than the vacuum negative pressure). This expands the diameter of the water inlet area of ​​the PA water pipe section. By controlling the critical head of the expanded bottom diameter section of the water pipe, the upward water flow velocity is controlled, ensuring that no vacuum zone is generated between the water inlet and drain sections of the PA water pipe. This effectively improves the siphon drainage capacity and accelerates the drainage speed of the PA water pipe. Attached Figure Description

[0040] Figure 1 This is a cross-sectional view of the combined sand well system for deep drainage of high slopes according to the present invention;

[0041] Figure 2 This is a cross-sectional view of the vertical sand well structure of the present invention;

[0042] Figure 3This is a cross-sectional view of the horizontal drainage well structure of the present invention;

[0043] Figure 4 This is a schematic diagram of the vertical sand well structure design calculation of the present invention;

[0044] Figure 5 This is a schematic diagram of the structural design and calculation of the horizontal drainage well of the present invention;

[0045] Figure 6 This is a schematic diagram illustrating the principle of the sintered clay material of the present invention as permeable to water but impermeable to air;

[0046] Figure 7 This is a schematic diagram of the vertical sand well single-hole unit of the present invention converting a polygon into a circle according to the principle of equal area;

[0047] Figure 8 This is a construction flowchart of the combined sand well system for deep drainage of high slopes according to the present invention.

[0048] In the diagram: 1—Slope; 2—Vertical sand well structure; 201—Vertical well hole; 202—Vertical placement within the vertical well hole; 203—Geotextile bag; 204—Sand and gravel filter layer; 205—Sand and gravel; 206—Cover; 207—Permeable board; 3—Horizontal drainage well structure; 301—Horizontal well hole; 302—Clay pipe; 303—Pipe end cap; 304—Geotextile filter; 4—Inclined drainage pipe; 5—Slope support structure; 6—Connector; 501—Drainage hole; 7—Siphon water pipe; 701—Enlarged diameter section; 8—Water-stop rubber cover. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figures 1 to 6 All accompanying drawings are simplified versions of embodiments and are intended only to clearly and concisely illustrate the embodiments of the present invention. The technical solutions shown in the drawings below are specific solutions of embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0051] This invention provides a combined sand well drainage structure suitable for high slopes, such as... Figures 1 to 3 As shown, the structure includes a slope 1 and a slope support structure 5. A drainage hole 501 is provided at the bottom of the slope support structure 5. The drainage structure includes a row of vertical sand well structures 2 arranged along the slope line 100 of the slope 1 within the slope and a siphon drainage structure arranged at the bottom of the row of vertical sand well structures 2. The vertical sand well structure 2 includes a vertical well hole 201 drilled vertically from the slope surface or top towards the slope body, a permeable pipe 202 vertically placed within the vertical well hole 201, and a filling material... A sand and gravel filter layer 204 is provided between the permeable pipe 202 and the inner wall of the vertical well hole 201. A geotextile bag 203 is installed inside the permeable pipe 202 and filled with sand and gravel 205. A cover 206 is provided at the opening of the permeable pipe 202 and the cover 206 is threaded to the opening of the permeable pipe 202. The lower end of each permeable pipe 202 is threaded to a clay pipe 302, and the permeable plate 207 at the connection is bonded to the lower end of the permeable pipe 202 with epoxy adhesive. The siphon drainage structure includes a siphon water guide pipe 7, a horizontal drainage well structure 3, and an inclined drainage pipe 4. The horizontal drainage well structure 3 includes a horizontal well hole 301 drilled horizontally from the slope surface towards the slope body and a clay pipe 302 arranged along the horizontal well hole 301. The clay pipe 302 is wrapped with a reverse filter geotextile 304. Both the horizontal well hole 301 and the clay pipe 302 are inclined downward from the slope surface towards the slope body, and the horizontal well hole 301 is connected to a row of vertical well holes 201. The clay pipe 302 has holes corresponding to the positions of each permeable pipe 202, and the lower end of each permeable pipe 202 is connected to the holes on the clay pipe 302. A permeable plate 207 is provided at the connection point; a sealing end cap 303 is provided at the lower end of the terracotta pipe 302 away from the slope; the upper end of the terracotta pipe 302 near the slope is connected to the inclined drainage pipe 4 through an adapter 6, and a water-stopping rubber cap 8 is provided at the connection point; the inclined drainage pipe 4 slopes downward from the upper end of the terracotta pipe 302 near the slope to the drainage hole 501; the siphon water guide pipe 7 is located inside the terracotta pipe 302 and the inclined drainage pipe 4; the siphon water guide pipe 7 extends from the lower end of the terracotta pipe 302 to the upper end of the terracotta pipe 302, and after passing through the water-stopping rubber cap 8, it extends along the inclined drainage pipe 4 to the drainage hole 501 and is connected to the drainage hole 501.

[0052] The embodiment provides a combined sand well drainage structure suitable for high slopes, such as Figures 1 to 3As shown, the siphon water pipe 7 has an enlarged diameter section 701 near the inlet area at the lower end of the clay pipe 302. The drain end of the siphon water pipe 7 extends from the drain hole 501. The diameter of the water pipe 701 is 5-10 mm, and the enlarged diameter section 701 is enlarged to 10-20 mm, with the enlarged diameter section being 1 / 5 to 2 / 5 of the total length of the water supply pipe. The permeable pipe 202 uses a plastic sleeve, and the pipe wall is covered with permeable holes of 15-25 mm in diameter at intervals of 15-30 cm. The permeable plate 207 uses a sand-based permeable plate or a granite permeable plate. The siphon water pipe 7 uses a PA material water pipe. The adapter 6 is a plastic connector, and its two ends are threaded or bonded to the clay pipe 302 and the inclined drain pipe 4, respectively. The inclined drain pipe 4 uses a plastic sleeve. The sealing end cap 303 uses sintered clay material and is connected to the port of the clay pipe 302 through epoxy resin. The slope protection structure 5 is a retaining wall or piles; the vertical well 201 is drilled by a spiral drilling rig; the horizontal well 301 is drilled by a directional drilling rig before the construction of the slope protection structure 5, with an inclination angle of 3 to 7°, and after the drilling is completed, the borehole of the horizontal well 301 is buried in the backfill soil layer.

[0053] In this embodiment of the invention, the slope surface of the slope 1 is provided with multiple sets of combined sand well drainage structures. Each set of combined sand well drainage structures includes multiple vertical sand well structures 2 and one horizontal drainage well structure 3. The multiple vertical sand well structures 2 are arranged in a row and are connected to the horizontal drainage well structure 3. The spacing between two adjacent sets of combined sand well drainage structures is 1.5 to 3m.

[0054] This invention has a wide range of applications and is suitable for various slope dewatering and drainage, especially for deep drainage of high fill soil slopes. It can effectively drain groundwater accumulated in the deep part of the slope, improve slope stability, and has low construction difficulty and low project cost.

[0055] In this embodiment, the present invention takes deep drainage of a high slope with a high groundwater level as an example, and the specific construction process is as follows:

[0056] S1: Measurement and positioning. Determine the number of combined sand well drainage structures based on local rainfall intensity. Determine the positions of vertical sand wells and horizontal drainage wells based on the location of the lowest drainage hole of the original slope retaining wall support structure. Each group of combined sand well drainage structures includes multiple vertical sand well structures 2 and one horizontal drainage well structure 3. The multiple vertical sand well structures 2 are arranged in a row along the slope line 100 of the slope. The horizontal drainage well structure 3 is arranged at the bottom of the row of vertical sand well structures 2, and the installation height of the horizontal drainage well structure 3 is higher than the installation height of the lowest drainage hole of the slope support structure 5. The number N of all vertical sand well structures on the slope 1 is based on the slope catchment area and rainfall Q. r The drainage capacity q of a single vertical sand well structure is determined as follows:

[0057]

[0058] Q r =βrA②

[0059] q=kiA0③

[0060] In the formula: β is the slope infiltration coefficient, which is usually taken as 0.5 to 0.8;

[0061] r represents rainfall intensity (mm / d); A represents the slope catchment area.

[0062] k is the permeability coefficient of the sand well; A0 is the cross-sectional area of ​​the sand well;

[0063] i is the hydraulic gradient, calculated based on the water level difference in the soil surrounding the well and the length of the water flow path.

[0064] N vertical sand well structures are arranged in a square, divided into squares. The resulting single-hole units are then converted from polygons into circles according to the principle of equal area, such as... Figure 7 As shown, the converted equivalent radius r e The relationship between the spacing l of the vertical sand well structure and the vertical sand well structure is as follows:

[0065]

[0066] Based on the above analysis, the sand well is divided into sections, and the cross-sectional diagram of a single-hole unit of the divided sand well is shown below. Figure 4 As shown, treating the drainage of a single sand well as a fixed-depth well flow problem, the following analytical solution can be obtained:

[0067]

[0068] In the formula: The equivalent radius r of a single sand well e The predetermined function is to reduce the depth of the deep well flow. The radial distance is dimensionless. The time constant is dimensionless; J0(x) is a zero-order Bessel function of the first kind; Y0(x) is a zero-order Bessel function of the second kind; basic parameters of sand wells are shown in [reference needed]. Figure 4 .

[0069] S2: Before the construction of the slope support structure 5, horizontal well holes 301 are drilled directionally from the lower slope surface towards the slope body. The horizontal well holes 301 are inclined downwards from the slope surface towards the slope body at an angle of 3-7°. One end of the clay pipe 302 is sealed with a pipe end cap 303, and holes with internal threaded interfaces are opened in the clay pipe 302 corresponding to each vertical sand well structure 2. Then, a filter geotextile 304 is wrapped around the clay pipe 302, with the filter geotextile 304 corresponding to the openings in the clay pipe 302. The position is also opened, and then the siphon water guide pipe 7 is placed into the clay pipe 302. A perforated water-stop rubber cap 8 is provided at the open end of the clay pipe 302. The siphon water guide pipe 7 extends out from the hole in the water-stop rubber cap 8. Finally, the adapter 6 is installed at the unsealed end of the clay pipe 302. The height difference between the first and last sections of the horizontal drainage well does not exceed 4m. The relative positions of the sintered clay material sleeve after the opening is set with the reverse filter geotextile. The bonding of the bottom sintered clay plate and the top water-stop rubber cap is completed. The plastic adapter is installed and the position of the siphon water guide pipe 7 is set.

[0070] To prevent a vacuum zone from being created at the bend in the inner guide pipe of the horizontal drainage well structure 6, where the descent speed exceeds the siphon's upward speed, the diameter of the inner guide pipe 7 in the horizontal drainage well structure 3 is increased to enhance the siphon's upward speed. To ensure continuous water flow, a vacuum zone must not be created at the bend in the guide pipe. For the entire guide pipe, without creating a vacuum zone, and assuming the inclination angle of the upper section of the siphon guide pipe 7 is within the range of 3–7°, the optimal head of the siphon guide pipe is assumed to be H. c Based on the continuity equation for incompressible fluids and Bernoulli's equation, the following head equation is obtained:

[0071] v Dup πD 2 =v down πd 2

[0072]

[0073] For the water supply pipe section, the following head equation is obtained:

[0074] v Dup πD 2 =v dup πd 2

[0075]

[0076] H1 is the head difference between the two ends of the siphon water pipe, which can be regarded as the height of the sewer pipe under heavy rain conditions.

[0077] H c To achieve the optimal head for the siphon water pipe;

[0078] To ensure continuous water flow and prevent vacuum zones from forming at bends in the water pipe, the aforementioned v is required. down With v up Since they are equal, the critical head of the variable diameter section is also the optimal head H of the siphon water guide pipe. c (That is, while keeping the total length of the water supply pipe constant, the increase in siphon velocity for each additional variable pipe diameter section is the largest) and must meet the following requirements:

[0079]

[0080] Where: D is the diameter of the siphon water pipe after the diameter reduction section is enlarged; d is the original diameter of the siphon water pipe; l Dup Increase the length of the diameter section of the siphon water supply pipe; dup The length of the original diameter section of the siphon water supply pipe; down λ is the length of the siphon drain pipe; dt This refers to the head loss along the original diameter section of the siphon water pipe; ζ dt This refers to the local head loss in the original diameter section of the siphon water pipe; λ Dup For the head loss along the section where the diameter of the siphon water supply pipe increases; ζ Dup This refers to the local head loss in the original diameter section of the siphon water pipe; This represents the maximum head of the siphon water pipe under atmospheric pressure.

[0081] Based on the calculated optimal head H of the siphon water pipe c， The ideal tilt angle α of the siphon water pipe 7 is calculated using trigonometric functions.

[0082]

[0083] S3. Drill a hole from the designed position of the lowest drainage hole 501 of the slope support structure 5 to the highest end of the horizontal well hole 301, and connect the hole with the horizontal well hole 301. Install the inclined drainage pipe 4 in the hole. Connect the upper end of the inclined drainage pipe 4 to the adapter 6. Pull out the siphon water guide pipe 7 and extend it along the inclined drainage pipe 4 from the position of the lower drainage hole 501.

[0084] S4. A spiral drilling rig is used to drill vertical well holes 201 from the top of the slope or the slope surface. The vertical well holes 201 are arranged in a row along the horizontal well holes 301. Each vertical well hole 201 is drilled to the top surface of the horizontal well hole 301 and is connected to the horizontal well hole 301. A permeable pipe 202 of the same length is installed in each vertical well hole 201. The bottom end of each permeable pipe 202 is bonded with a permeable plate 207 by epoxy resin. The lower end of each permeable pipe 202 is provided with an external threaded connection port. The permeable pipe 202 is lowered into the corresponding vertical well hole 201. The lower end is threadedly connected to the corresponding hole on the earthen pipe 302. A sand and gravel filter layer 204 is filled between the permeable pipe 202 and the wall of the vertical well hole 201. After the permeable pipe 202 is installed, geotextile bags 203 filled with sand and gravel are placed in layers inside the permeable pipe 202 and covered with a cover 206.

[0085] S5: After the vertical sand well structure 2 and the horizontal drainage well structure 3 are completed, the backfill soil layer will completely bury the horizontal drainage well structure 3 and the inclined drainage pipe 4, and the slope support structure 5 will be constructed. When constructing the lowest drainage hole 501 of the slope support structure 5, the corresponding siphon water pipe 7 will be pulled out from the lowest drainage hole 501.

[0086] S6: Replace the geotextile bags in the vertical sand wells in a timely manner after they reach the end of their service life to ensure the vertical sand wells' ability to collect groundwater and drain water.

[0087] This invention addresses situations where the groundwater level is high on slopes and local rainfall is abundant. It utilizes vertical sand wells distributed in a 2m x 2m grid pattern on the slope surface to collect groundwater. Gravity draws the groundwater into horizontal drainage wells, whose sintered clay sleeves also absorb surrounding groundwater. The groundwater in the horizontal drainage wells is then drained through drainage holes in the retaining wall via a PA (polycarbonate) water pipe. When the PA water pipe discharges water, creating negative pressure in the sintered clay sleeves, this negative pressure further accelerates the collection of surrounding groundwater by the vertical sand wells and the absorption of surrounding groundwater by the sintered clay sleeves. This allows for the rapid discharge of groundwater accumulated deep within the slope, effectively lowering the groundwater level and improving the overall stability of the slope.

[0088] Due to the siphon effect, this method lowers the groundwater level to the horizontal well position at a rate approximately 2 to 3 times faster than conventional drainage measures, and the construction period is halved, reducing the project cost by about 30%.

[0089] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the structural relationships and principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A combined sand well drainage structure suitable for high slopes, comprising a slope (1) and a slope support structure (5), wherein a drainage hole (501) is provided at the bottom of the slope support structure (5), characterized in that: The combined sand well drainage structure includes a row of vertical sand well structures (2) arranged along the slope line (100) within the slope (1) and a siphon drainage structure arranged at the bottom of the row of vertical sand well structures (2); the vertical sand well structure (2) includes a vertical well hole (201) drilled vertically from the slope surface or top towards the slope body, a permeable pipe (202) placed vertically within the vertical well hole (201), and a sand and gravel filter layer (204) filled between the permeable pipe (202) and the inner wall of the vertical well hole (201). The water pipe (202) is filled with sand and gravel (205); the siphon drainage structure includes a siphon water guide pipe (7), a horizontal drainage well structure (3) and an inclined drainage pipe (4). The horizontal drainage well structure (3) includes a horizontal well hole (301) drilled horizontally from the slope surface (1) towards the slope body and a clay pipe (302) laid along the horizontal well hole (301). The clay pipe (302) is wrapped with a reverse filter geotextile (304). The horizontal well hole (301) and the clay pipe (302) both run from the slope surface towards the slope body. Inclined downwards, with horizontal well holes (301) connected to a row of vertical well holes (201), the clay pipe (302) has holes corresponding to the positions of each permeable pipe (202), the lower end of each permeable pipe (202) is connected to the holes on the clay pipe (302), and a permeable plate (207) is provided at the connection point; the lower end of the clay pipe (302) away from the slope is provided with a sealing end cap (303), and the upper end of the clay pipe (302) near the slope is connected to the inclined drainage pipe (4) through an adapter (6), and at the connection point... The joint is provided with a water-stop rubber cover (8). The inclined drainage pipe (4) slopes down from the high end of the earthenware pipe (302) near the slope to the lowest drainage hole (501). The siphon water guide pipe (7) is located inside the earthenware pipe (302) and the inclined drainage pipe (4). The siphon water guide pipe (7) extends from the low end of the earthenware pipe (302) to the high end of the earthenware pipe (302), and after passing through the water-stop rubber cover (8), it extends along the inclined drainage pipe (4) to the lowest drainage hole (501) and communicates with the lowest drainage hole (501).

2. The combined sand well drainage structure suitable for high slopes according to claim 1, characterized in that: The siphon water pipe (7) has an enlarged diameter section (701) near the inlet area of ​​the lower end of the clay pipe (302). The drain end of the siphon water pipe (7) extends from the lowest drain hole (501), and the lowest end of the siphon water pipe (7) is higher than the height of the lowest drain hole (501). The diameter of the water pipe (7) is 5-10 mm, and the enlarged diameter section (701) is enlarged to 10-20 mm. The length of the enlarged diameter section accounts for 1 / 5 to 2 / 5 of the total length of the water supply pipe.

3. A combined sand well drainage structure suitable for high slopes according to claim 1 or 2, characterized in that: The slope (1) is provided with multiple sets of combined sand well drainage structures. Each set of combined sand well drainage structures includes multiple vertical sand well structures (2) and one horizontal drainage well structure (3). The multiple vertical sand well structures (2) are arranged in a row and connected to the horizontal drainage well structure (3). The distance between two adjacent sand well drainage structures in the same set and between two adjacent sets of sand well drainage structures is 1.5 to 3m.

4. A combined sand well drainage structure suitable for high slopes according to claim 1 or 2, characterized in that: The permeable pipe (202) is made of plastic sleeve, and the pipe wall is covered with permeable holes of 15-25mm in diameter at intervals of 15-30cm. A geotextile bag (203) is installed inside the permeable pipe (202), and the sand and gravel (205) are filled inside the geotextile bag (203). A cap (206) is provided at the opening of the permeable pipe (202), and the cap (206) is threaded to the opening of the permeable pipe (202). The lower end of each permeable pipe (202) is threaded to a clay pipe (302), and a permeable plate (2) is installed at the connection. 07) The lower end of the permeable pipe (202) is bonded with epoxy adhesive. The permeable plate (207) is a sand-based permeable plate or a granite permeable plate. The siphon water pipe (7) is a PA material water pipe. The adapter (6) is a plastic connector, and its two ends are threaded or bonded to the clay pipe (302) and the inclined drainage pipe (4) respectively. The inclined drainage pipe (4) is a plastic sleeve. The sealing end cap (303) is made of sintered clay material and is connected to the end of the clay pipe (302) with epoxy resin.

5. A combined sand well drainage structure suitable for high slopes according to claim 1 or 2, characterized in that: The slope protection structure (5) is a retaining wall or a pile wall; the vertical well hole (201) is drilled by a spiral drilling machine; the horizontal well hole (301) is drilled by a directional drilling machine before the construction of the slope protection structure (5), and its inclination angle is 3 to 7°. After the drilling is completed, the borehole of the horizontal well hole (301) is buried in the backfill soil layer.

6. A construction method for a combined sand well drainage structure suitable for high slopes as described in any one of claims 1 to 5, characterized in that, The specific construction steps are as follows: S1: Measurement and positioning. Based on the original design of the slope support structure (5), determine the location of the combined sand well drainage structure. The combined sand well drainage structure includes multiple vertical sand well structures (2) and one horizontal drainage well structure (3). Multiple vertical sand well structures (2) are arranged in a row along the slope line (100) of the slope. The horizontal drainage well structure (3) is arranged at the bottom of the row of vertical sand well structures (2), and the setting height of the horizontal drainage well structure (3) is higher than the setting height of the lowest drainage hole of the slope support structure (5). S2: Before the construction of the slope support structure (5), horizontal well holes (301) are drilled directionally from the lower slope surface towards the slope body. The horizontal well holes (301) are inclined downwards from the slope surface towards the slope body at an angle of 3-7°. One end of the clay pipe (302) is sealed with a pipe end cap (303), and holes with internal threaded interfaces are opened in the clay pipe (302) corresponding to each vertical sand well structure (2). A reverse filter geotextile (304) is wrapped around the earthen tube (302), and the reverse filter geotextile (304) is also perforated at the position corresponding to the opening of the earthen tube (302). Then, the siphon water pipe (7) is placed inside the earthen tube (302). A perforated water-stop rubber cap (8) is provided at the open end of the earthen tube (302). The siphon water pipe (7) extends out from the hole in the water-stop rubber cap (8). Finally, an adapter (6) is installed at the unsealed end of the earthen tube (302). S3: Drill a hole from the designed position of the lowest drainage hole (501) of the slope support structure (5) to the highest end of the horizontal well hole (301), and the hole is connected to the horizontal well hole (301). Install an inclined drainage pipe (4) in the hole. Connect the upper end of the inclined drainage pipe (4) to the adapter (6). Pull out the siphon water pipe (7) and extend it along the inclined drainage pipe (4) to the position of the lower drainage hole (501). S4: A spiral drilling rig is used to drill vertical wells (201) from the top or surface of the slope. A row of vertical wells (201) is laid along the horizontal wells (301). Each vertical well (201) is drilled to the top surface of the horizontal well (301) and connected to it. A permeable pipe (202) of matching length is installed in each vertical well (201). A permeable plate (207) is bonded to the bottom of each permeable pipe (202) with epoxy resin. The lower end of the water pipe (202) is provided with an external threaded connection port. The permeable pipe (202) is lowered into the corresponding vertical well hole (201). The lower end is threadedly connected to the corresponding hole on the clay pipe (302). A sand and gravel filter layer (204) is filled between the permeable pipe (202) and the wall of the vertical well hole (201). After the permeable pipe (202) is installed, geotextile bags (203) filled with sand and gravel are placed in layers inside the permeable pipe (202) and covered with a cover (206). S5: After the construction of the vertical sand well structure (2) and the horizontal drainage well structure (3) is completed, the backfill soil layer will completely bury the horizontal drainage well structure (3) and the inclined drainage pipe (4), and the slope support structure (5) will be constructed. When constructing the lowest drainage hole (501) of the slope support structure (5), the corresponding siphon water pipe (7) will be pulled out from the lowest drainage hole (501).

7. A construction method for a combined sand well drainage structure suitable for high slopes according to claim 6, characterized in that: In step S1, multiple sets of combined sand well drainage structures are provided, and these multiple sets of combined sand well drainage structures are distributed in parallel on the slope (1). The number N of all vertical sand well structures on the slope (1) is based on the slope's catchment area and the amount of precipitation Q. r The drainage capacity q of a single vertical sand well structure is determined as follows: Q r =βrA② q=kiA0③ In the formula: β is the slope infiltration coefficient, which is usually taken as 0.5 to 0.8; r represents rainfall intensity (mm / d); A represents the slope catchment area. k is the permeability coefficient of the sand well; A0 is the cross-sectional area of ​​the sand well; i is the hydraulic gradient, calculated based on the water level difference in the soil surrounding the well and the length of the water flow path.

8. A construction method for a combined sand well drainage structure suitable for high slopes according to claim 7, characterized in that: To prevent a vacuum zone from being created by the descent speed exceeding the siphon rise speed at the bend of the inner guide pipe in the horizontal drainage well structure (6), the diameter of the inner guide pipe (7) in the suction section of the horizontal drainage well structure (3) is increased to enhance the siphon rise speed. To ensure continuous water flow and prevent a vacuum zone from being created at the bend of the guide pipe, the optimal head H of the siphon guide pipe (7) is set. c The following requirements must be met to calculate Hc using the following formula: In the formula: H1 is the head difference between the two ends of the siphon pipe, which can be regarded as the height of the sewer pipe under heavy rain conditions; D is the diameter of the siphon pipe after the diameter reduction section is enlarged; d is the original diameter of the siphon pipe; l Dup Increase the length of the diameter section of the siphon water supply pipe; dup The length of the original diameter section of the siphon water supply pipe; down λ is the length of the siphon drain pipe; dt This refers to the head loss along the original diameter section of the siphon water pipe; ζ dt This refers to the local head loss in the original diameter section of the siphon water pipe; λ Dup For the head loss along the section where the diameter of the siphon water supply pipe increases; ζ Dup This refers to the local head loss in the original diameter section of the siphon water pipe; This represents the maximum head of the siphon water pipe under atmospheric pressure. Based on the calculated optimal head H of the siphon water pipe c， The inclination angle α of the siphon water pipe (7) is calculated using trigonometric functions; 9. A construction method for a combined sand well drainage structure suitable for high slopes according to claim 7 or 8, characterized in that: The permeable pipe (202) in step S3 is made of plastic pipe, with permeable holes of 15-25mm in diameter arranged at intervals of 15-30cm on the pipe wall. After the geotextile bag (203) inside the pipe reaches the end of its service life, it is directly extracted and replaced to ensure the vertical sand well structure (2) has the ability to collect groundwater and drain water. The siphon water pipe (7) in the horizontal drainage well uses siphon action to drain water. When the head H0 of the siphon water pipe (7) is greater than or equal to 4m, a pump is installed at the outlet of the siphon water pipe (7) to pump out the water accumulated in the horizontal drainage well.

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