Combined sand drain drainage structure suitable for high slope and construction method of combined sand drain drainage structure

Abstract

The invention provides a combined sand drain drainage structure suitable for a high slope. The combined well drainage structure comprises a row of vertical sand well structures arranged in the side slope along the slope surface line of the side slope and siphon drainage structures arranged at the bottom ends of the row of vertical sand well structures. The vertical sand well structure comprises a vertical well hole, a water permeable pipe and a gravel inverted filter layer, and the water permeable pipe is filled with gravel; the siphon drainage structure comprises a siphon water guide pipe, a horizontal drainage well structure and an inclined drainage pipe. Rainwater of the high slope is collected through the sand wells, the rainwater is collected into the horizontal drainage wells under the action of gravity, underground water collected by the horizontal drainage wells is drained from the drainage holes in the lowest end of the supporting structure through the siphon guide pipes, then negative pressure is generated in the horizontal drainage wells, and drainage of the vertical sand wells is further accelerated. The construction difficulty of the deep drainage structure of the high slope is reduced, and it is guaranteed that underground water enriched under the effects of rainfall, underground pipeline water leakage and the like can be drained in time and rapidly.

Description

Technical Field

[0001] The present invention relates to the field of landslide disaster prevention, management and control, and specifically to a combined sand well drainage structure suitable for high slopes and a construction method thereof. The drainage system can achieve deep rapid drainage of high slopes, and is particularly suitable for the management of high earth fill slopes in areas with heavy rainfall. Technical Background

[0002] The concept of "controlling water before controlling slopes" should be strictly implemented in slope engineering. The occurrence of a large number of slope disasters is closely related to rainfall. The long-term enrichment of groundwater will lead to increased sliding force on the slope and reduced shear strength. Therefore, quickly and efficiently draining groundwater from the slope is a key issue in landslide disaster control engineering.

[0003] At present, the commonly used deep drainage measures for high slopes are vertical drainage wells + drainage tunnels. However, vertical drainage wells are easily blocked by silt and are difficult to maintain. At the same time, when encountering heavy rainfall or large groundwater recharge, the drainage capacity of vertical drainage wells is limited, so that the groundwater in the deep part of the high slope cannot be discharged in time, affecting the stability of the slope. The construction of drainage tunnels is difficult and costly, and it causes great damage to the environment, aggravates soil erosion on the slope, and makes the slope stability worse. Some experts have proposed a horizontal sand well drainage method, which has limited drainage capacity and is inconvenient for later maintenance. Some experts have also proposed a negative pressure drainage method started by drilling. However, this method has a large number of horizontal drill holes in the lower part of the slope, is difficult to construct, and causes great disturbance to the slope. Therefore, there is an urgent need for a deep drainage measure for high slopes with fast drainage speed, low construction cost, and simple construction. Summary of the invention

[0004] In view of the shortcomings and defects of the prior art, the present invention provides a combined sand well drainage structure suitable for high slopes and a construction method thereof; the drainage structure is easy to construct, can ensure that groundwater enriched under the effects of rainfall, underground pipe leakage, etc. can be discharged in a timely and rapid manner, and can improve the safety of the high slopes.

[0005] In order to solve the above problems, the present invention provides a combined sand well drainage structure suitable for high slopes, including 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 in the slope along the slope surface line and a siphon drainage structure arranged at the bottom of a row of vertical sand well structures; the vertical sand well structure includes a vertical wellbore drilled vertically from the slope surface or the top of the slope toward the slope body, a permeable pipe vertically placed in the vertical wellbore and a sand and gravel filter layer filled between the permeable pipe and the inner wall of the vertical wellbore, and the permeable pipe is filled with sand and gravel; the siphon drainage structure includes a siphon water guide pipe, a horizontal drainage well structure and an inclined drainage pipe, the horizontal drainage well structure includes a horizontal wellbore drilled horizontally from the slope surface toward the slope body and a clay pipe arranged along the horizontal wellbore, The clay pipe is wrapped with an anti-filter geotextile. The horizontal wellbore and the clay pipe are both inclined downward from the slope surface toward the slope body, and the horizontal wellbore is connected with a row of vertical wellbores. The clay pipe is provided with a hole corresponding to the position of each permeable pipe. The lower end of each permeable pipe is connected with the hole on the clay pipe, and a permeable plate is provided at the connection position; the lower end of the clay pipe away from the slope surface is provided with a sealing pipe end cap, and the high end of the clay pipe close to the slope surface is connected with the oblique drainage pipe through an adapter, and a water-stopping rubber cover is provided at the connection position. The oblique drainage pipe is inclined downward from the high end of the clay pipe close to the slope surface to the lowest drainage hole. The siphon water guide pipe is located in the clay pipe and the oblique drainage pipe. The siphon water guide pipe extends from the lower end of the clay pipe to the high end of the clay pipe, and after passing through the water-stopping rubber cover, it extends along the oblique drainage pipe to the lowest drainage hole and is connected with the lowest drainage hole.

[0006] A better technical solution of the present invention is as follows: the siphon water pipe is provided with an enlarged pipe diameter section in the water inlet area near the lower end of the clay pipe, the drainage end of the siphon water pipe extends from the lowest drainage hole, and the lowest end of the siphon water pipe is higher than the height of the lowest drainage hole; the water pipe has a diameter of 5 to 10 mm, the enlarged pipe diameter section is enlarged to 10 to 20 mm, and the length of the enlarged pipe diameter section is 1 / 5 to 2 / 5 of the total length of the upper water pipe.

[0007] A better technical solution of the present invention is as follows: the slope surface of the slope is provided with a plurality of groups of combined sand well drainage structures, each group of combined sand well drainage structures includes a plurality of vertical sand well structures and a horizontal drainage well structure, the plurality of vertical sand well structures are arranged in a row and connected with the horizontal drainage well structure; the spacing between two adjacent sand well drainage structures in the same group and between two adjacent groups of sand well drainage structures is 1.5 to 3 m.

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

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

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

[0011] S1: Measurement and positioning, determining the position of the combined sand well drainage structure according to the originally designed slope support structure, wherein the combined sand well drainage structure comprises a plurality of vertical sand well structures and a horizontal drainage well structure, wherein the plurality of vertical sand well structures are arranged in a row along the slope surface line of the slope, and the horizontal drainage well structure is arranged at the bottom of a row of vertical sand well structures, and the setting height of the horizontal drainage well structure is higher than the arrangement height of the lowest drainage hole of the slope support structure;

[0012] S2: Before the construction of the slope support structure, a horizontal wellbore is directionally drilled from the slope surface at the lower part of the slope toward the slope body, and the horizontal wellbore is inclined downward from the slope surface toward the slope body, and the inclination angle is 3 to 7 degrees; one end of the clay pipe is sealed by a pipe sealing end cap, and a hole with an internal thread interface is opened at the position of the clay pipe corresponding to each vertical sand well structure, and then the anti-filter geotextile is coated on the outside of the clay pipe, and the anti-filter geotextile is also opened at the position corresponding to the opening of the clay pipe, and then the siphon water guide pipe is placed in the clay pipe, and a water-stopping rubber cover with an opening is provided at the open end of the clay pipe, and the siphon water guide pipe extends from the hole on the water-stopping rubber cover, and finally a adapter is installed at the unsealed end of the clay pipe;

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

[0014] S4. Use a spiral drill to drill a vertical wellbore from the top or slope surface. The vertical wellbore is arranged in a row along the horizontal wellbore. Each vertical wellbore is drilled to the top surface of the horizontal wellbore and connected with the horizontal wellbore. A water-permeable pipe of a matching length is installed in each vertical wellbore. The bottom end of each water-permeable pipe is bonded with a water-permeable plate by epoxy resin, and the lower end of each water-permeable pipe is provided with an external threaded connection port. The water-permeable pipe is lowered into the corresponding vertical wellbore, and the lower end is threadedly connected with the corresponding hole on the clay pipe, and a sand and gravel filter layer is filled between the water-permeable pipe and the wall of the vertical wellbore. After the water-permeable pipe is installed, geotextile bags filled with sand and gravel are placed in layers in the water-permeable pipe, and the cover is covered;

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

[0016] The preferred technical solution of the present invention is as follows: In the step S1, a plurality of combined sand well drainage structures are provided, and the plurality of combined sand well drainage structures are parallelly distributed on the slope, and the number N of all vertical sand well structures on the slope is determined according to the precipitation Q of the slope catchment area. r And the drainage volume q of a single vertical sand well structure is determined by:

[0017]

[0018] Q r =βrA②

[0019] q=kiA 0 ③

[0020] Where: β is the slope infiltration coefficient, usually 0.5 to 0.8;

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

[0022] k is the permeability coefficient of the sand well; A 0 is the cross-sectional area of ​​the sand well;

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

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

[0025]

[0026] The preferred technical solution of the present invention is: in order to prevent the downward speed of the water pipe at the turning point in the transfer joint of the horizontal drainage well structure from being greater than the siphon rising speed, thereby generating a vacuum zone, the diameter of the water pipe is enlarged for the water suction section of the water pipe in the horizontal drainage well structure to increase the siphon rising speed; in order to ensure the continuity of water flow and not generate a vacuum zone at the turning point of the water pipe, the optimal head H of the siphon water pipe is c The following requirements need to be met and Hc is calculated according to the following formula:

[0027]

[0028] Where: H 1 is the water head difference between the two ends of the siphon water pipe, which can be regarded as the height of the downpipe under heavy rain conditions; 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 To increase the diameter of the upper water pipe of the siphon water pipe; l dup l is the length of the original diameter section of the upper water pipe of the siphon water pipe; down is the length of the siphon aqueduct downpipe; dt is the head loss along the original diameter section of the siphon water pipe; dt is the local head loss of the original diameter section of the siphon water pipe; Dup ζ is the head loss along the section where the diameter of the water pipe on the siphon aqueduct increases; Dup It is the local head loss of the original diameter section of the siphon water pipe; It is the maximum head of the siphon water pipe under the action of atmospheric pressure;

[0029] According to the calculated optimal head H of the siphon water pipe c， Calculate the inclination angle a of the siphon aqueduct according to trigonometric functions;

[0030]

[0031] The preferred technical solution of the present invention is as follows: the water-permeable pipe in the step S3 is a plastic pipe, and the pipe wall is covered with water-permeable holes with a diameter of 15 to 25 mm at intervals of 15 to 30 cm. After the geotextile bag in the pipe body reaches the end of its service life, it is directly extracted and replaced to ensure the vertical sand well structure to collect groundwater and drain water; the siphon water pipe in the horizontal drainage well uses siphon action to drain water, and the head H of the siphon water pipe 0When the height is greater than or equal to 4m, a pump is installed at the outlet of the siphon water pipe to pump out the accumulated water in the horizontal drainage well.

[0032] The geotextile bag needs to collect groundwater around the vertical sand well and collect the groundwater into the horizontal drainage well structure through gravity. For the filling sand, the particle size is generally required to be between 0.25 and 5 mm, of which the proportion of 0.5 to 2 mm particles should exceed 50%, the content of fine sand (such as particle size <0.1 mm) should be <5%, the mud content (particle size <0.075 mm) should be <3%, and the permeability coefficient should be between 1×10 -2 ~1×10 -1 cm / s, the non-uniformity coefficient is controlled at C u =d 60 / d 10 ≤5. The clay pipe is made of sintered clay material. When the groundwater is saturated, the small gaps between the clay are filled with water, and then it can be water-permeable but air-tight. In the case of groundwater enrichment, the surrounding groundwater can flow in while effectively reducing the gas in the horizontal drainage well. At the same time, the anti-filter geotextile is wrapped around the outside of the clay pipe, effectively preventing silt from flowing into the clay pipe and preventing the clay pipe from being blocked.

[0033] In order to ensure the normal operation of the siphon effect, it is necessary to ensure that the horizontal drainage well structure does not generate a large number of bubbles, and the head is required to be within 4m. In order to ensure that there is no vacuum zone between the upper and lower water pipes in the PA water pipe, it is necessary to increase the rising speed of the water flow in the upper water pipe, so the diameter of the bottom of the upper water pipe of the PA water pipe is enlarged, and the length of the enlarged diameter section is about 1 / 5 of the total length. When the flow rate of the PA water pipe is greater than the water collection speed of the vertical sand well, negative pressure will be generated in the horizontal drainage well, further accelerating the water collection speed of the vertical sand well until the water level drops to the specified water level.

[0034] Beneficial effects of the present invention:

[0035] (1) The present invention includes a vertical sand well and a horizontal drainage well. The vertical sand well is distributed on the slope and can collect groundwater enriched 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 is gathered 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 end of the horizontal drainage well, the oblique drainage pipe extends downward to the drainage hole at the lowest end of the slope support structure. A section of the PA water guide pipe in the horizontal drainage well is inclined upward to form an upper water pipe section, and a section in the oblique drainage pipe is inclined downward to form a lower water pipe section. The two sections of the pipe body can form a siphon structure, and the water is continuously discharged using the principle of siphon. The structure can efficiently discharge groundwater enriched in the high slope, reducing the harm of groundwater to the stability of the slope.

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

[0037] (3) A plastic casing is arranged in the vertical sand well of the present invention, and sand bags are piled in the plastic casing to form a core-pulling vertical sand well. When the sand well is blocked and the ability to collect groundwater is weakened, the casing can be pulled out to replace the geotextile bag and fill with sand, thereby realizing the long-term effectiveness of the vertical sand well;

[0038] (4) The horizontal drainage well of the present invention adopts a sintered clay material sleeve which can be water-permeable but air-tight after being saturated with groundwater, effectively reducing the gas in the sleeve and ensuring the siphon effect of the water pipe. At the same time, it is also easier to generate negative pressure in the sintered clay material sleeve, thereby accelerating the speed of collecting groundwater in the vertical sand well.

[0039] (5) When the water generated by the siphon effect flows into the sewer pipe, the gravity may cause the downward water flow speed to be greater than the upward water flow speed, thereby generating a vacuum zone (when the head speed shared by gravity is greater than the influence of the vacuum negative pressure), the diameter of the water inlet area of ​​the upper water pipe section of the PA water pipe is expanded, and the water flow rising speed is controlled by controlling the critical head of the expanded bottom diameter section of the upper water pipe, ensuring that no vacuum zone is generated between the upper water pipe section and the lower water pipe section of the PA water pipe, effectively improving the siphon drainage capacity and accelerating the drainage speed of the PA water pipe. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0044] Figure 5 It is a schematic diagram of the design calculation of the horizontal drainage well structure of the present invention;

[0045] Figure 6 It is a schematic diagram of the principle that the sintered clay material of the present invention is water-permeable but air-impermeable;

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

[0047] Figure 8The invention is a construction flow chart of a combined sand well system suitable for deep drainage of high slopes.

[0048] In the figure: 1-slope, 2-vertical sand well structure, 201-vertical well hole, 202-vertically placed in 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-sealing pipe end cap, 304-filter geotextile, 4-oblique drainage pipe, 5-slope support structure, 6-adapter, 501-sluice hole, 7-siphon water guide pipe, 701-enlarged pipe diameter section, 8-waterstop rubber cover, DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Figures 1 to 6 The drawings are all of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The technical solutions shown in the following drawings are specific solutions of the embodiments of the present invention and are not intended to limit the scope of the invention claimed for protection. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0051] The embodiment of the present invention provides a combined sand well drainage structure suitable for high slopes, such as Figures 1 to 3As shown, it 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, and the drainage structure includes a row of vertical sand well structures 2 arranged in the slope along the slope surface line 100 of 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 the top of the slope toward the slope body, a permeable pipe 202 vertically placed in the vertical well hole 201 and a drainage hole 201 filled in the vertical well hole 201. A sand and gravel filter layer 204 is provided between the permeable pipe 202 and the inner wall of the vertical wellbore 201. A geotextile bag 203 is provided inside the permeable pipe 202, and the geotextile bag 203 is filled with sand and gravel 205. A cover 206 is provided at the pipe mouth of the permeable pipe 202, and the cover 206 is threadedly connected to the pipe mouth of the permeable pipe 202; the lower end of each permeable pipe 202 is threadedly connected to the clay pipe 302, and the permeable plate 207 at the connection is bonded to the lower end of the permeable pipe 202 by epoxy glue. The siphon drainage structure includes a siphon water pipe 7, a horizontal drainage well structure 3 and an inclined drainage pipe 4. The horizontal drainage well structure 3 includes a horizontal wellbore 301 drilled horizontally from the slope surface of the slope 1 toward the slope body and a clay pipe 302 arranged along the horizontal wellbore 301. The clay pipe 302 is wrapped with an anti-filter geotextile 304. The horizontal wellbore 301 and the clay pipe 302 are both inclined downward from the slope surface toward the slope body, and the horizontal wellbore 301 is connected with a row of vertical wellbores 201. The clay pipe 302 is provided with a hole corresponding to the position of each permeable pipe 202, and the lower end of each permeable pipe 202 is connected to the hole on the clay pipe 302. , and a water-permeable plate 207 is provided at the connection position; a sealing pipe end cap 303 is provided at the lower end of the clay pipe 302 away from the slope, and the high end of the clay pipe 302 close to the slope is connected with the oblique drainage pipe 4 through an adapter 6, and a waterproof rubber cover 8 is provided at the connection position, the oblique drainage pipe 4 is inclined downward from the high end of the clay pipe 302 close to the slope to the drainage hole 501, the siphon water guide pipe 7 is located in the clay pipe 302 and the oblique drainage pipe 4, the siphon water guide pipe 7 extends from the lower end of the clay pipe 302 to the high end of the clay pipe 302, and after passing through the waterproof rubber cover 8, extends along the oblique drainage pipe 4 to the drainage hole 501, and is connected with 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 is provided with an enlarged diameter section 701 near the water inlet area at the lower end of the clay pipe 302, and the drainage end of the siphon water pipe 7 extends from the drain hole 501; the diameter of the water pipe 701 is 5-10mm, and the enlarged diameter section 701 is enlarged to 10-20mm, and the enlarged diameter section is 1 / 5-2 / 5 of the total length of the water pipe. The permeable pipe 202 is made of plastic sleeve, and the pipe wall is covered with permeable holes with a diameter of 15-25mm at intervals of 15-30cm; the permeable board 207 is made of sand-based permeable board or granite permeable board; the siphon water pipe 7 is made of PA material; the adapter 6 is a plastic joint, and its two ends are respectively threaded or bonded with the clay pipe 302 and the oblique drainage pipe 4; the oblique drainage pipe 4 is made of plastic sleeve; the sealing pipe end cap 303 is made of sintered clay material and connected to the end of the clay pipe 302 through epoxy resin. The slope support structure 5 is a retaining wall or a pile row; the vertical wellbore 201 is drilled by a spiral drilling rig; the horizontal wellbore 301 is drilled by a directional drilling rig before the construction of the slope support structure 5, and its inclination angle is 3 to 7 degrees. After the drilling construction is completed, the borehole of the horizontal wellbore 301 is buried in the backfill soil layer.

[0053] In an embodiment of the present invention, the slope surface of the slope 1 is provided with a plurality of groups of combined sand well drainage structures, each group of combined sand well drainage structures includes a plurality of vertical sand well structures 2 and a horizontal drainage well structure 3, the plurality of vertical sand well structures 2 are arranged in a row and connected with the horizontal drainage well structure 3; the spacing between two adjacent groups of combined sand well drainage structures is 1.5 to 3 m.

[0054] The present invention has a wide range of applications and is suitable for various slope precipitation and drainage, and is particularly suitable for deep drainage of high fill soil slopes. It can effectively discharge groundwater enriched in the deep part of the slope, improve the stability of the slope, and has low construction difficulty and low engineering cost.

[0055] In this embodiment, the present invention takes the deep drainage of high slope with 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 according to the local rainfall intensity, and determine the positions of vertical sand wells and horizontal drainage wells according to the position of the lowest drainage hole of the original designed 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, multiple vertical sand well structures 2 are arranged in a row along the slope surface line 100 of the slope, and the horizontal drainage well structure 3 is arranged at the bottom of a row of vertical sand well structures 2, and the setting height of the horizontal drainage well structure 3 is higher than the arrangement 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 determined according to the precipitation Q of the slope catchment area r And the drainage volume q of a single vertical sand well structure is determined by:

[0057]

[0058] Q r =βrA②

[0059] q=kiA 0 ③

[0060] Where: β is the slope infiltration coefficient, usually 0.5 to 0.8;

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

[0062] k is the permeability coefficient of the sand well; A 0 is the cross-sectional area of ​​the sand well;

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

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

[0065]

[0066] Based on the above analysis, the sand well is segmented, and the cross-sectional diagram of the single-hole unit of the segmented sand well is as follows: Figure 4 As shown in the figure, considering the drainage of a single sand well as a fixed deep well flow problem, the following analytical solution can be obtained:

[0067]

[0068] Where: is the equivalent radius of a single sand well r e The function of reducing the depth of deep well flow is determined internally; is the dimensionless radial distance; is dimensionless time; J 0 (x) is the zero-order first-kind Bessel function; Y 0 (x) is the zero-order second-kind Bessel function; the basic parameters of the sand well are shown in Figure 4 .

[0069] S2: Before the construction of the slope support structure 5, a horizontal wellbore 301 is directionally drilled from the slope surface at the lower part of the slope toward the slope body, and the horizontal wellbore 301 is inclined downward from the slope surface toward the slope body, and its inclination angle is 3 to 7 degrees; one end of the clay pipe 302 is sealed by a sealing pipe end cap 303, and a hole with an internal thread interface is opened at the position of the clay pipe 302 corresponding to each vertical sand well structure 2, and then the anti-filter geotextile 305 is coated on the outside of the clay pipe 302, and the anti-filter geotextile 305 corresponds to the hole of the clay pipe 302. A hole is also drilled at the position, and then the siphon water guide pipe 7 is placed in the clay pipe 302. A water-stopping rubber cover 8 with a hole is provided at the open end of the clay pipe 302. The siphon water guide pipe 7 extends out from the hole on the water-stopping rubber cover 8. Finally, the adapter 6 is installed at the unsealed end of the clay pipe 302. The height difference between the head and tail sections of the horizontal drainage well does not exceed 4m. The relative position of the sintered clay material sleeve after the hole is set and the anti-filter geotextile is set. The bonding of the sintered clay plate at the bottom and the water-stopping rubber cover at the top is completed. The plastic adapter is installed, and the position of the siphon water guide pipe 7 is set.

[0070] In order to prevent the downward speed of the water pipe at the turning point in the horizontal drainage well structure transfer joint 6 from being greater than the siphon rising speed, thus generating a vacuum zone, the diameter of the water pipe 7 in the horizontal drainage well structure 3 is enlarged to increase the siphon rising speed; in order to ensure the continuity of water flow, a vacuum zone cannot be generated at the turning point of the water pipe. For the entire water pipe, without generating a vacuum zone, when the water section of the siphon water pipe 7 meets the inclination angle of 3 to 7 degrees, it is assumed that the optimal head of the siphon water pipe is H c ; Based on the continuity equation of incompressible fluid and Bernoulli 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 hydraulic head equation is obtained:

[0074] v Dup πD 2 =v dup πd 2

[0075]

[0076] H 1 It is the water head difference at both ends of the siphon water pipe, which can be regarded as the height of the sewer pipe in heavy rain conditions;

[0077] H c The best head for siphon water pipe;

[0078] In order to ensure the continuity of water flow and avoid the formation of vacuum zone at the bend of the water pipe, the v down With v up equal, so the critical head of the variable diameter section is the optimal head of the siphon water pipe H c (That is, under the premise of keeping the total length of the water supply pipe unchanged, the corresponding siphon flow rate increase value for each additional length of the variable pipe diameter section is the largest) meets 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 To increase the diameter of the upper water pipe of the siphon water pipe; l dup l is the length of the original diameter section of the upper water pipe of the siphon water pipe; down is the length of the siphon aqueduct downpipe; dt is the head loss along the original diameter section of the siphon water pipe; dt is the local head loss of the original diameter section of the siphon water pipe; Dup ζ is the head loss along the section where the diameter of the water pipe on the siphon aqueduct increases; Dup It is the local head loss of the original diameter section of the siphon water pipe; It is the maximum head of the siphon water pipe under the action of atmospheric pressure;

[0081] According to the calculated optimal head H of the siphon water pipe c， Calculate the most ideal inclination angle a of the siphon water conduit 7 according to trigonometric functions;

[0082]

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

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

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

[0086] S6: When the geobags of the vertical sand well reach the end of their service life, they should be replaced in time to ensure the vertical sand well’s ability to collect groundwater and drain water.

[0087] The present invention aims at the situation where the groundwater level on the slope is high and there is a lot of rainfall in the local area. The groundwater is collected through vertical sand wells. The vertical sand wells are distributed in a 2m×2m grid on the slope surface. The groundwater is converged into a horizontal drainage well through gravity. The sintered clay material sleeve of the horizontal drainage well can also absorb the surrounding groundwater. The groundwater in the horizontal drainage well is discharged through the drainage hole of the retaining wall through the siphon effect of the PA water pipe. When the PA water pipe drains water and causes the sintered clay material sleeve to generate negative pressure, the negative pressure will further accelerate the speed at which the vertical sand wells collect the surrounding groundwater and the sintered clay material sleeve absorbs the surrounding groundwater, so the groundwater enriched in the deep part of the slope can be quickly discharged, the groundwater level of the slope is effectively lowered, and the overall stability of the slope is improved.

[0088] Due to the siphon effect, this method can reduce the groundwater level to the horizontal well position at a speed about 2 to 3 times that of conventional drainage measures, and the construction period is shortened by half, and the project cost is reduced by about 30%.

[0089] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the structural relationship and principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached 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 well drainage structure comprises a row of vertical sand well structures (2) arranged in the slope along the slope surface line (100) of 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) comprises a vertical well hole (201) drilled vertically from the slope surface or the top of the slope toward the slope body, a water permeable pipe (202) vertically arranged in the vertical well hole (201) and a sand and gravel filter layer (204) filled between the water permeable pipe (202) and the inner wall of the vertical well hole (201); the water permeable pipe (202) is provided in the vertical well hole (201) and the sand and gravel filter layer (204) is provided between the water permeable pipe (202) and the inner wall of the vertical well hole (201). The pipe (202) is filled with sand and gravel (205); the siphon drainage structure comprises a siphon water guide pipe (7), a horizontal drainage well structure (3) and an inclined drainage pipe (4); the horizontal drainage well structure (3) comprises a horizontal wellbore (301) drilled horizontally from the slope surface of the slope (1) toward the slope body and a clay pipe (302) arranged along the horizontal wellbore (301); the clay pipe (302) is wrapped with an anti-filter geotextile (304); the horizontal wellbore (301) and the clay pipe (302) are both drilled horizontally from the slope surface toward the slope body. The wellbore (301) is downwardly inclined, and the horizontal wellbore (301) is connected to a row of vertical wellbores (201). The clay pipe (302) is provided with a hole corresponding to the position of each water-permeable pipe (202). The lower end of each water-permeable pipe (202) is connected to the hole on the clay pipe (302), and a water-permeable plate (207) is provided at the connection position. The lower end of the clay pipe (302) away from the slope surface is provided with a sealing end cap (303), and the upper end of the clay pipe (302) close to the slope surface is connected to the inclined drainage pipe (4) through a conversion joint (6), and the connection is completed. A water-stopping rubber cover (8) is provided at the connection part; the oblique drainage pipe (4) slopes downward from the high end of the clay pipe (302) close to the slope surface to the lowest drainage hole (501); the siphon water guide pipe (7) is located in the clay pipe (302) and the oblique drainage pipe (4); the siphon water guide pipe (7) extends from the lower end of the clay pipe (302) to the high end of the clay pipe (302), passes through the water-stopping rubber cover (8), and then extends along the oblique drainage pipe (4) to the lowest drainage hole (501), and is connected to 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 conduit (7) is provided with an enlarged pipe diameter section (701) in the water inlet region near the lower end of the clay pipe (302); the drainage end of the siphon water conduit (7) extends from the lowest drainage hole (501), and the lowest end of the siphon water conduit (7) is higher than the height of the lowest drainage hole (501); the pipe diameter of the water conduit (701) is 5 to 10 mm, the enlarged pipe diameter section (701) is enlarged to 10 to 20 mm, and the length of the enlarged pipe diameter section is 1 / 5 to 2 / 5 of the total length of the water conduit.

3. A combined sand well drainage structure suitable for high slopes according to claim 1 or 2, characterized in that: The slope surface of the slope (1) is provided with a plurality of groups of combined sand well drainage structures, each group of combined sand well drainage structures comprises a plurality of vertical sand well structures (2) and a horizontal drainage well structure (3), the plurality of 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 sand well drainage structures in the same group and between two adjacent groups of sand well drainage structures is 1.5 to 3 m.

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

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

6. A construction method for the combined sand well drainage structure suitable for high slopes as claimed in claims 1 to 5, characterized in that: The specific construction steps are as follows: S1: measuring and positioning, determining the position of the combined sand well drainage structure according to the originally designed slope support structure (5), wherein the combined sand well drainage structure comprises a plurality of vertical sand well structures (2) and a horizontal drainage well structure (3), wherein the plurality of vertical sand well structures (2) are arranged in a row along the slope surface line (100) of the slope, and 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), a horizontal wellbore (301) is directionally drilled from the slope surface at the bottom of the slope toward the slope body, wherein the horizontal wellbore (301) is inclined downward from the slope surface toward the slope body, and the inclination angle is 3 to 7 degrees; one end of the clay pipe (302) is sealed by a sealing pipe end cap (303), and a hole with an internal thread interface is opened in the clay pipe (302) at a position corresponding to each vertical sand well structure (2), and then A filter geotextile (305) is coated on the outside of the clay pipe (302), and a hole is also opened in the filter geotextile (305) at a position corresponding to the hole of the clay pipe (302), and then a siphon water guide pipe (7) is placed in the clay pipe (302), and a water-stopping rubber cover (8) with a hole is provided at the open end of the clay pipe (302), and the siphon water guide pipe (7) extends out from the hole on the water-stopping rubber cover (8), and finally an adapter (6) is installed at the unsealed end of the clay pipe (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 wellbore (301), and connect the drilled hole with the horizontal wellbore (301). Install an inclined drainage pipe (4) in the drilled hole. Connect the upper end of the inclined drainage pipe (4) to the adapter (6). Pull out the siphon water guide pipe (7), extend it along the inclined drainage pipe (4) and from the position of the lower drainage hole (501); S4. A spiral drill is used to form a vertical wellbore (201) from the top or the surface of the slope. The vertical wellbore (201) is arranged in a row along the horizontal wellbore (301). Each vertical wellbore (201) is drilled to the top surface of the horizontal wellbore (301) and is connected to the horizontal wellbore (301). A water-permeable pipe (202) of a length matching that of the water-permeable pipe (202) is installed in each vertical wellbore (201). The bottom end of each water-permeable pipe (202) is bonded with a water-permeable plate (207) by epoxy resin, and each water-permeable pipe (202) is provided with a water-permeable plate (207). The lower end of the water pipe (202) is provided with an external threaded connection port, the water permeable pipe (202) is lowered into the corresponding vertical wellbore (201), the lower end is threadedly connected to the corresponding hole on the clay pipe (302), and a sand and gravel filter layer (204) is filled between the water permeable pipe (202) and the hole wall of the vertical wellbore (201). After the water permeable pipe (202) is installed, geotextile bags (203) filled with sand and gravel are placed in layers in the water permeable pipe (202), and the cover (206) is covered; S5: After the construction of the vertical sand well structure (2) and the horizontal drainage well structure (3) is completed, the soil layer is backfilled to completely bury the horizontal drainage well structure (3) and the inclined drainage pipe (4), and the slope support structure (5) is constructed. When constructing the lowest drainage hole (501) of the slope support structure (5), the corresponding siphon water guide pipe (7) is pulled out from the lowest drainage hole (501).

7. The construction method of a combined sand well drainage structure suitable for high slopes according to claim 6, characterized in that: In step S1, a plurality of combined sand well drainage structures are provided, and the plurality of combined sand well drainage structures are parallelly distributed on the slope (1). The number N of all vertical sand well structures on the slope (1) is determined according to the precipitation Q of the slope catchment area. r And the drainage volume q of a single vertical sand well structure is determined by: Q r =βrA② q=kiA0③ Where: β is the slope infiltration coefficient, usually 0.5 to 0.8; r is rainfall intensity (mm / d); A is 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, which is calculated based on the water level difference in the soil around the sand well and the length of the water flow path.

8. The construction method of a combined sand well drainage structure suitable for high slopes according to claim 7, characterized in that: N vertical sand well structures are arranged in a square and divided into squares. The single-hole units obtained after division are converted from polygons into circles according to the principle of equal area. The equivalent radius r after conversion is e The relationship between the spacing l and the vertical sand well structure is as follows:

9. A construction method for a combined sand well drainage structure suitable for high slopes according to claim 7 or 8, characterized in that: In order to prevent the downward speed of the water pipe at the turning point of the transfer joint (6) in the horizontal drainage well structure from being greater than the siphon rising speed, thereby generating a vacuum zone, the diameter of the water pipe (7) in the water suction section of the horizontal drainage well structure (3) is enlarged to increase the siphon rising speed; in order to ensure the continuity of water flow and not generate a vacuum zone at the turning point of the water pipe, the optimal head H of the siphon water pipe (7) is c The following requirements need to be met and Hc is calculated according to the following formula: Where: H1 is the water head difference between the two ends of the siphon water pipe, which can be regarded as the height of the downpipe under heavy rain conditions; 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 To increase the diameter of the upper water pipe of the siphon water pipe; l dup l is the length of the original diameter section of the upper water pipe of the siphon water pipe; down is the length of the siphon aqueduct; λdt is the head loss along the original diameter section of the siphon aqueduct; ζ dt is the local head loss of the original diameter section of the siphon water pipe; Dup ζ is the head loss along the section where the diameter of the water pipe on the siphon aqueduct increases; Dup It is the local head loss of the original diameter section of the siphon water pipe; It is the maximum head of the siphon water pipe under the action of atmospheric pressure; According to the calculated optimal head H of the siphon water pipe c， Calculating the inclination angle a of the siphon water conduit (7) according to trigonometric functions; 10. A construction method for a combined sand well drainage structure suitable for high slopes according to claim 7, 8 or 9, characterized in that: The permeable pipe (202) in step S3 is a plastic pipe, and small permeable holes with a diameter of 15 to 25 mm are distributed on the pipe wall at intervals of 15 to 30 cm. After the geotextile bag (203) in the pipe body reaches the end of its service life, it is directly extracted and replaced to ensure the vertical sand well structure (1) to collect groundwater and drain water; the siphon water pipe (7) in the horizontal drainage well uses siphon action to drain water, and when the head H0 of the siphon water pipe (7) is greater than or equal to 4m, a pump is set at the outlet of the siphon water pipe (7) to suck the accumulated water in the horizontal drainage well.

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