Face mask earth dam bank slope under-membrane interception drainage system and construction method thereof

Abstract

The invention provides a face mask earth dam bank slope under-membrane interception drainage system and a construction method thereof, the face mask earth dam bank slope under-membrane interception drainage system comprises a geomembrane and further comprises a drainage mat laid under the geomembrane, and a plurality of transverse ditches and longitudinal ditches are arranged under the drainage mat. The transverse ditches comprise a water seepage collecting ditch arranged along the slope toe of the bank slope and a plurality of first intercepting ditches arranged at different bank slope heights, the longitudinal ditches comprise a plurality of second intercepting ditches arranged along the slope direction of the bank slope, and the plurality of second intercepting ditches are communicated between every two transverse ditches which are adjacent up and down; by arranging the drainage mat, the first intercepting ditch, the second intercepting ditch and the water seepage collecting ditch below the geomembrane, the reliability and safety of drainage under the geomembrane are improved, and meanwhile the risk that the geomembrane is reversely jacked and damaged is reduced; by arranging the first drainage solid pipe and the second drainage solid pipe, membrane penetrating water seepage and underground water collection in the drainage mat are mutually independent, and leakage monitoring is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water and electricity engineering, and particularly relates to a membrane under-slope drainage system for a membrane dam bank slope and a construction method thereof. BACKGROUND

[0002] Defect holes that occur occasionally in the operation process of a whole-reservoir basin geomembrane seepage prevention reservoir cannot be completely avoided. If a geomembrane has a large leakage defect and has no reasonable drainage channel, or the underground water level line of the bank slope is high, the underground water will overflow on the membrane under-slope surface. The seepage water will gradually accumulate and generate a certain pressure under the geomembrane. When the reservoir water level drops, the water pressure under the membrane is greater than the pressure outside the membrane, a reverse jacking effect is generated, and when the water pressure under the membrane is large enough, the geomembrane will bulge and gradually form a defect hole, causing the seepage through the membrane and threatening the safe use of the geomembrane. Such accidents are particularly obvious in a pumped storage power station reservoir. The water level of the pumped storage power station is in a variable amplitude process of lifting and dropping for a long time, the pressure on the membrane changes greatly, and the bulging position is repeatedly stressed to easily form fatigue damage. SUMMARY

[0003] The purpose of the present application is to overcome the deficiencies of the prior art, and provide a membrane under-slope drainage system for a membrane dam bank slope, which can solve the problem that the pressure on the geomembrane changes greatly and the bulging position is repeatedly stressed to easily form fatigue damage.

[0004] To this end, the present application adopts the following technical solutions: A membrane under-slope drainage system for a membrane dam bank slope, comprising a geomembrane, further comprising a drainage mat laid under the geomembrane, a plurality of transverse water ditches and longitudinal water ditches are arranged under the drainage mat, the bottom of the transverse water ditch is connected with an underground water level line, the transverse water ditch comprises a seepage water collecting ditch arranged along the toe of the bank slope and a plurality of first water cutting ditches arranged at different bank slope heights, respectively, the longitudinal water ditch comprises a plurality of second water cutting ditches arranged along the direction of the bank slope gradient, a plurality of second water cutting ditches are respectively connected between two adjacent transverse water ditches in the up-down direction, and a reservoir bottom water guide groove is connected to the side of the seepage water collecting ditch away from the bank slope.

[0005] On the basis of the above technical solutions, the present application can further adopt the following further technical solutions, or use these further technical solutions in combination: One end of the second water cutting ditch is connected to the bottom of the first water cutting ditch arranged above.

[0006] Geotextiles are laid on the inner walls of the reservoir bottom water diversion channel, the transverse water ditch, and the longitudinal water ditch. The first intercepting ditch and the second intercepting ditch are filled with a first graded crushed stone and a first clay waterproof layer. The first clay waterproof layer is located between the drainage mat and the first graded crushed stone. The seepage collection ditch is filled with a second graded crushed stone, which is in contact with the lower surface of the drainage mat. A second clay waterproof layer is provided on the side of the seepage collection ditch away from the bank slope, which is in contact with the lower surface of the geomembrane. The reservoir bottom water diversion channel is filled with a third clay waterproof layer, which is in contact with the lower surface of the geomembrane.

[0007] A first drainage pipe is installed at the bottom of several second intercepting ditches near the toe of the bank slope. The outlet end of the first drainage pipe is connected to a first drainage pipe. One end of the first drainage pipe extends to the bottom of the seepage collection ditch. A second drainage pipe is installed at the bottom of the seepage collection ditch along its length. The first drainage pipe is connected to the second drainage pipe.

[0008] The bottom of the seepage collection ditch is equipped with a second drainage pipe that runs along its length to collect seepage water through the membrane.

[0009] The lower part of the reservoir bottom water diversion channel is provided with a geomembrane seepage collection and drainage solid pipe and a groundwater seepage collection and drainage solid pipe arranged along its length direction. The water outlet end of the second drainage pipe is connected to the geomembrane seepage collection and drainage solid pipe, and the water outlet end of the second drainage solid pipe is connected to the groundwater seepage collection and drainage solid pipe.

[0010] The drainage slopes of the first drainage perforated pipe, the second drainage perforated pipe, the first drainage solid pipe, the second drainage solid pipe, the geomembrane seepage collection and drainage solid pipe, and the groundwater seepage collection and drainage solid pipe are all greater than 1%.

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a construction method for a geomembrane slope drainage system, which can solve the problems of large pressure changes on the geomembrane and fatigue failure caused by repeated stress on the bulging position.

[0012] Therefore, the present invention adopts the following technical solution: A construction method for a drainage system under the membrane of a faceplate earth dam slope includes the following steps: 1. Assess the groundwater level and determine the location, quantity, and dimensions of the first and second intercepting ditches; 2. Locate and mark the positions of the first and second intercepting ditches. As the earthen dam slope is excavated, the first and second intercepting ditches on the slope are excavated simultaneously and gradually. 3. After the excavation of the first and second intercepting ditches is completed, geotextile is laid on the inner walls of the first and second intercepting ditches respectively. The first drainage pipe and the first drainage pipe connected to the first drainage pipe are pre-embedded at the bottom of several second intercepting ditches near the toe of the bank slope. One end of the first drainage pipe extends to the outside of the second intercepting ditch. Then, the first grade crushed stone is filled into the first and second intercepting ditches to ensure the stability of the ditch walls. Then, the first clay waterproof layer is filled on the first grade crushed stone in the first and second intercepting ditches and compacted. 4. Locate and mark the location of the seepage collection ditch. First, excavate and replace the second clay waterproof layer on the side of the seepage collection ditch away from the bank slope. After the second clay waterproof layer is backfilled and compacted, gradually excavate the seepage collection ditch at the toe of the bank slope. 5. After the excavation of the seepage collection ditch is completed, geotextile is laid on the inner wall of the seepage collection ditch, and a second drainage perforated pipe and a second drainage solid pipe are pre-embedded at the bottom of the seepage collection ditch along its length. The outlet end of the first drainage solid pipe is connected to the second drainage solid pipe, and the outlet end of the second drainage perforated pipe and the second drainage solid pipe extends to the outside of the seepage collection ditch. Then, the second grade crushed stone is filled into the seepage collection ditch. 6. Excavate a water diversion channel at the bottom of the reservoir on the side of the seepage collection ditch away from the bank slope. After the water diversion channel at the bottom of the reservoir is excavated, lay geotextile on the inner wall of the water diversion channel at the bottom of the reservoir. In advance, pre-embed geomembrane seepage collection and drainage pipe and groundwater seepage collection and drainage pipe at the bottom of the water diversion channel at the bottom of the reservoir. Extend the second drainage pipe and the second drainage pipe into the water diversion channel at the bottom of the reservoir. Connect the outlet end of the second drainage pipe to the geomembrane seepage collection and drainage pipe and the outlet end of the second drainage pipe to the groundwater seepage collection and drainage pipe. Lead the outlet ends of the geomembrane seepage collection and drainage pipe and the groundwater seepage collection and drainage pipe to the outside of the reservoir and then connect to the measuring weir. After the laying is completed, backfill the water diversion channel at the bottom of the reservoir with a third clay waterproof layer. 7. After completing the above work, lay drainage mats to cover the first intercepting ditch, the second intercepting ditch, and the seepage collection ditch. After the drainage mats are laid, gradually lay geomembrane on top of them.

[0013] The width of the first intercepting ditch, the second intercepting ditch, and the seepage collection ditch is greater than or equal to 0.8m. The depth of the first intercepting ditch and the second intercepting ditch is determined according to the groundwater level. The depth of the seepage collection ditch is greater than 1m. The thickness of the first clay waterproof layer above the first grade crushed stone is at least 0.5m.

[0014] The drainage slopes of the first drainage perforated pipe, the second drainage perforated pipe, the first drainage solid pipe, the second drainage solid pipe, the geomembrane seepage collection and drainage solid pipe, and the groundwater seepage collection and drainage solid pipe are all greater than 1%.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: The use of a slope membrane under-membrane drainage system improves the reliability and safety of drainage under the membrane by setting drainage mats, a first intercepting ditch, a second intercepting ditch, and a seepage collection ditch below the geomembrane, while reducing the risk of geomembrane overturning and damage. By setting up a first and second drainage pipe, the seepage through the membrane and the collection of groundwater in the drainage mat are independent of each other, which is beneficial for leakage monitoring, early warning and analysis of geomembrane damage, and facilitates geomembrane inspection and maintenance. Attached Figure Description

[0016] Figure 1 This is a typical planar schematic diagram of the present invention.

[0017] Figure 2 This is a typical cross-sectional schematic diagram of the bank slope sections of the first and second intercepting ditches of the present invention.

[0018] Figure 3 This is a typical cross-sectional schematic diagram of the width direction of the first intercepting ditch of the present invention.

[0019] Figure 4 This is a typical cross-sectional schematic diagram of the width direction of the second intercepting ditch of the present invention.

[0020] Figure 5 This is a typical cross-sectional schematic diagram of the present invention.

[0021] Figure 6 This is a typical cross-sectional schematic diagram of the water intake channel at the bottom of the reservoir in this invention, along its width. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0024] The present invention provides a geomembrane slope interception and drainage system for a geomembrane dam, including a geomembrane 11 and a drainage mat 3 laid under the geomembrane 11. Several transverse and longitudinal ditches are provided under the drainage mat 3. The bottom of the transverse ditches is connected to the groundwater level 10. The transverse ditches include seepage collection ditches 5 set along the toe of the slope and several first interception ditches 1 set at different slope heights. The longitudinal ditches include several second interception ditches 2 set along the slope gradient. Several second interception ditches 2 are connected between two adjacent transverse ditches. The side of the seepage collection ditches 5 away from the slope is connected to the bottom water intake channel 12.

[0025] The transverse drainage ditch is mainly used to collect groundwater, lower the groundwater level by 10, and prevent groundwater from overflowing on the slope.

[0026] The longitudinal ditches intersect and connect with the transverse ditches, and collect the water accumulated in the transverse ditches to the foot of the slope.

[0027] The drainage mat 3 is mainly used to collect seepage water from the defects of the geomembrane 11 and to channel the seepage water through the membrane to the toe of the slope.

[0028] One end of the second intercepting ditch 2 is connected to the bottom of the adjacent first intercepting ditch 1 above it.

[0029] Geotextile 8 is laid on the inner walls of the reservoir bottom water diversion channel 12, the transverse water ditch and the longitudinal water ditch respectively. The first intercepting ditch 1 and the second intercepting ditch 2 are filled with first grade crushed stone 91 and first clay waterproof layer 41. The first clay waterproof layer 41 is located between the drainage mat 3 and the first grade crushed stone 91. The seepage collection ditch 5 is filled with second grade crushed stone 92. The second grade crushed stone 92 is in contact with the lower surface of the drainage mat 3. The seepage collection ditch 5 is provided with a second clay waterproof layer 42 on the side away from the bank slope. The second clay waterproof layer 42 is in contact with the lower surface of the geomembrane 11. The reservoir bottom water diversion channel 12 is filled with a third clay waterproof layer 43. The third clay waterproof layer 43 is in contact with the lower surface of the geomembrane 11.

[0030] The first clay waterproof layer 41 is mainly used to separate seepage water through the membrane from groundwater, while the second clay waterproof layer 42 separates seepage water from the bottom of the reservoir and seepage water from the banks of the reservoir.

[0031] Several second intercepting ditches 2 near the toe of the bank slope are provided with first drainage flower pipes 61 at the bottom. The outlet end of the first drainage flower pipe 61 is connected to a first drainage solid pipe 71. One end of the first drainage solid pipe 71 extends to the bottom of the seepage collection ditch 5. The bottom of the seepage collection ditch 5 is provided with a second drainage solid pipe 72 arranged along its length. The first drainage solid pipe 71 and the second drainage solid pipe 72 are connected.

[0032] The bottom of the seepage collection ditch 5 is provided with a second drainage pipe 62 that runs along its length to collect seepage water through the membrane.

[0033] The lower part of the reservoir bottom water diversion channel 12 is provided with a geomembrane seepage collection and drainage solid pipe 73 and a groundwater seepage collection and drainage solid pipe 74 arranged along its length. The outlet end of the second drainage pipe 62 is connected to the geomembrane seepage collection and drainage solid pipe 73, and the outlet end of the second drainage pipe 72 is connected to the groundwater seepage collection and drainage solid pipe 74.

[0034] Groundwater collected in the transverse ditch flows into the first drainage pipe 61 and then into the first drainage pipe 71 and the second drainage pipe 72, eventually converging and flowing into the groundwater seepage collection and drainage pipe 74. Seepage water collected in the drainage mat 3 flows into the geomembrane seepage collection and drainage pipe 73 after being collected by the second drainage pipe 62. The geomembrane seepage collection and drainage pipe 73 and the groundwater seepage collection and drainage pipe 74 are then connected to a measuring weir.

[0035] The drainage slopes of the first drainage perforated pipe 61, the second drainage perforated pipe 62, the first drainage solid pipe 71, the second drainage solid pipe 72, the geomembrane seepage collection and drainage solid pipe 73, and the groundwater seepage collection and drainage solid pipe 74 are all greater than 1%.

[0036] The extent of damage to the geomembrane 11 and the rise of surface water can be determined by the amount of water collected in the geomembrane seepage collection and drainage pipe 73 and the groundwater seepage collection and drainage pipe 74, respectively.

[0037] The present invention provides a construction method for a drainage system under a membrane on the slope of a dam, comprising the following steps: 1. Assess the groundwater level and determine the location, quantity, and dimensions of the first intercepting ditch 1 and the second intercepting ditch 2; 2. Locate and mark the positions of the first intercepting ditch 1 and the second intercepting ditch 2. As the earthen dam slope is excavated, the first intercepting ditch 1 and the second intercepting ditch 2 on the slope are excavated simultaneously and gradually. 3. After the excavation of the first intercepting ditch 1 and the second intercepting ditch 2 is completed, geotextile 8 is laid on the inner wall of the first intercepting ditch 1 and the second intercepting ditch 2 respectively. The first drainage flower pipe 61 and the first drainage solid pipe 71 connected to the first drainage flower pipe 61 are pre-embedded at the bottom of several second intercepting ditch 2 near the slope foot. One end of the first drainage solid pipe 71 extends to the outside of the second intercepting ditch 2. Then, the first grade crushed stone 91 is filled into the first intercepting ditch 1 and the second intercepting ditch 2 to ensure the stability of the ditch wall. Then, the first clay water-proof layer 41 is filled on the first grade crushed stone 91 in the first intercepting ditch 1 and the second intercepting ditch 2 and compacted. 4. Locate and lay out the position of the seepage collection ditch 5. First, excavate and replace the second clay waterproof layer 42 on the side of the seepage collection ditch 5 away from the bank slope. After the second clay waterproof layer 42 is backfilled and compacted, the seepage collection ditch 5 at the toe of the bank slope is gradually excavated. 5. After the excavation of the seepage collection ditch 5 is completed, geotextile 8 is laid on the inner wall of the seepage collection ditch 5, and the second drainage perforated pipe 62 and the second drainage solid pipe 72 are pre-embedded at the bottom of the seepage collection ditch 5 along its length. The outlet end of the first drainage solid pipe 71 is connected to the second drainage solid pipe 72. The outlet ends of the second drainage perforated pipe 62 and the second drainage solid pipe 72 are extended to the outside of the seepage collection ditch 5. Then, the second grade crushed stone 92 is filled into the seepage collection ditch 5. 6. On the side of the seepage collection ditch 5 away from the bank slope, excavate the bottom water diversion channel 12. After the bottom water diversion channel 12 is excavated, lay geotextile 8 on the inner wall of the bottom water diversion channel 12. In advance, pre-embed geomembrane seepage collection and drainage pipe 73 and groundwater seepage collection and drainage pipe 74 in the lower part of the bottom water diversion channel 12. Extend the second drainage pipe 62 and the second drainage pipe 72 into the bottom water diversion channel 12. Connect the outlet end of the second drainage pipe 62 to the geomembrane seepage collection and drainage pipe 73 and the outlet end of the second drainage pipe 72 to the groundwater seepage collection and drainage pipe 74. Lead the outlet ends of the geomembrane seepage collection and drainage pipe 73 and the groundwater seepage collection and drainage pipe 74 to the outside of the reservoir and then connect to the measuring weir. After the laying is completed, backfill the bottom water diversion channel 12 with the third clay waterproof layer 43. 7. After completing the above work, lay drainage mat 3. Drainage mat 3 covers the first intercepting ditch 1, the second intercepting ditch 2 and the seepage collection ditch 5. After the drainage mat 2 is laid, geomembrane 11 is gradually laid on it.

[0038] The widths of the first intercepting ditch 1, the second intercepting ditch 2, and the seepage collection ditch 5 are all greater than or equal to 0.8m. The depths of the first intercepting ditch 1 and the second intercepting ditch 2 are determined according to the groundwater level 10. The depth of the seepage collection ditch 5 is greater than 1m. The thickness of the first clay waterproof layer 41 located above the first grade crushed stone 91 is at least 0.5m.

[0039] The drainage slopes of the first drainage perforated pipe 61, the second drainage perforated pipe 62, the first drainage solid pipe 71, the second drainage solid pipe 72, the geomembrane seepage collection and drainage solid pipe 73, and the groundwater seepage collection and drainage solid pipe 74 are all greater than 1%.

[0040] Based on the description and accompanying drawings of this invention, those skilled in the art can easily manufacture or use the membrane-supported drainage system and its construction method for a dam slope, and can achieve the positive effects described in this invention.

[0041] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "linked," and "sleeve" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral construction; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In the description of this invention, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the mechanism 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. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0043] Furthermore, in practicing the claims of this invention, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the present invention are covered by the scope of the claims of the present invention, and will not be listed here.

Claims

1. A geomembrane (11) under-slope drainage system for earth dam slopes, comprising a geomembrane (11), characterized in that, Further comprising a drainage mat (3) laid under the geomembrane (11), wherein a plurality of transverse water ditches and longitudinal water ditches are arranged under the drainage mat (3), the bottom of the transverse water ditches is connected with the underground water level line (10), the transverse water ditches comprise a water seepage collecting ditch (5) arranged at the toe of the bank slope and a plurality of first intercepting ditches (1) arranged at different bank slope heights respectively, the longitudinal water ditches comprise a plurality of second intercepting ditches (2) arranged along the direction of the bank slope gradient, a plurality of second intercepting ditches (2) are respectively connected between two adjacent transverse water ditches in the up-down direction, and the side of the water seepage collecting ditch (5) far from the bank slope is connected with a reservoir bottom water guiding groove (12).

2. A membrane underdrain system for a face dam embankment according to claim 1, wherein, One end of the second intercepting ditch (2) is connected with the bottom of the first intercepting ditch (1) arranged above.

3. A membrane underdrain system for a face dam embankment according to claim 1, wherein, The inner walls of the reservoir bottom water guiding groove (12), the transverse water ditches and the longitudinal water ditches are respectively laid with geotextiles (8), the first intercepting ditches (1) and the second intercepting ditches (2) are both filled with first graded gravel (91) and a first clay water-proof layer (41), the first clay water-proof layer (41) is arranged between the drainage mat (3) and the first graded gravel (91), the water seepage collecting ditch (5) is filled with second graded gravel (92), the second graded gravel (92) is connected with the lower surface of the drainage mat (3), the side of the water seepage collecting ditch (5) far from the bank slope is provided with a second clay water-proof layer (42), the second clay water-proof layer (42) is connected with the lower surface of the geomembrane (11), and the reservoir bottom water guiding groove (12) is filled with a third clay water-proof layer (43), the third clay water-proof layer (43) is connected with the lower surface of the geomembrane (11).

4. A membrane underdrain system for a face dam embankment according to claim 1, wherein, The bottom of the second intercepting ditch (2) close to the toe of the bank slope is provided with a first drainage flower pipe (61), the water outlet end of the first drainage flower pipe (61) is connected with a first drainage solid pipe (71), one end of the first drainage solid pipe (71) extends to the bottom of the water seepage collecting ditch (5), the bottom of the water seepage collecting ditch (5) is provided with a second drainage solid pipe (72) arranged along the length direction of the water seepage collecting ditch (5), and the first drainage solid pipe (71) is connected with the second drainage solid pipe (72).

5. A membrane underdrain system for a face dam embankment according to claim 4, wherein, The bottom of the water seepage collecting ditch (5) is provided with a second drainage flower pipe (62) arranged along the length direction of the water seepage collecting ditch (5) for collecting membrane seepage water.

6. A membrane underdrain system for a face dam embankment according to claim 5, wherein, The lower part of the reservoir bottom water guiding groove (12) is provided with a geomembrane seepage water collecting drainage solid pipe (73) and a groundwater seepage water collecting drainage solid pipe (74) arranged along the length direction of the reservoir bottom water guiding groove (12), the water outlet end of the second drainage flower pipe (62) is connected with the geomembrane seepage water collecting drainage solid pipe (73), and the water outlet end of the second drainage solid pipe (72) is connected with the groundwater seepage water collecting drainage solid pipe (74).

7. A membrane underdrain system for a face dam embankment according to claim 5, wherein, The drainage slopes of the first drainage flower pipe (61), the second drainage flower pipe (62), the first drainage solid pipe (71), the second drainage solid pipe (72), the geomembrane seepage water collecting drainage solid pipe (73) and the groundwater seepage water collecting drainage solid pipe (74) are all greater than 1%.

8. A construction method of a face dam slope membrane underdrain system characterized by, The method comprises the following steps: I. Assess the groundwater level, determine the first trench (1), the second trench (2) layout position, quantity and size; II. The position of the first trench (1), the second trench (2) is positioned and staked out, with the excavation of the dam slope, the first trench (1), the second trench (2) on the slope is gradually excavated; III. After the first trench (1), the second trench (2) is excavated, the first trench (1), the second trench (2) is laid on the inner wall of the geotextile (8), and the first drainage flower pipe (61) and the first drainage pipe (71) are pre-buried at the bottom of the second trench (2) near the toe of the slope, one end of the first drainage pipe (71) extends to the outside of the second trench (2), then the first graded gravel (91) is filled in the first trench (1), the second trench (2), so as to ensure the stability of the trench wall, and then the first clay waterproof layer (41) is filled on the first graded gravel (91) in the first trench (1), the second trench (2) and is compacted; IV. The position of the water collecting trench (5) is positioned and staked out, the second clay waterproof layer (42) is excavated and replaced on the side of the water collecting trench (5) away from the slope, after the second clay waterproof layer (42) is backfilled and compacted, the water collecting trench (5) at the toe of the slope is gradually excavated; V. After the water collecting trench (5) is excavated, the geotextile (8) is laid on the inner wall of the water collecting trench (5), and the second drainage flower pipe (62) and the second drainage pipe (72) are pre-buried at the bottom of the water collecting trench (5) in the length direction, the water outlet end of the first drainage pipe (71) is communicated with the second drainage pipe (72), the water outlet end of the second drainage flower pipe (62) and the second drainage pipe (72) extends to the outside of the water collecting trench (5), then the second graded gravel (92) is filled in the water collecting trench (5); VI. The bottom of the reservoir is excavated on the side of the water collecting trench (5) away from the slope, the geotextile (8) is laid on the inner wall of the bottom of the reservoir, and the geotextile membrane water collecting drainage pipe (73) and the underground water collecting drainage pipe (74) are pre-buried at the lower part of the bottom of the reservoir, the second drainage flower pipe (62) and the second drainage pipe (72) extend into the bottom of the reservoir, the water outlet end of the second drainage flower pipe (62) is communicated with the geotextile membrane water collecting drainage pipe (73), the water outlet end of the second drainage pipe (72) is communicated with the underground water collecting drainage pipe (74), the water outlet end of the geotextile membrane water collecting drainage pipe (73) and the underground water collecting drainage pipe (74) is led to the outside of the reservoir, then a water weir is connected, after the laying is completed, the third clay waterproof layer (43) is backfilled in the bottom of the reservoir; Seven, after the above work, laying drainage mat (3), drainage mat (3) covers the first water trench (1), the second water trench (2) and the water seepage collection trench (5), after the completion of the drainage mat (2), gradually laying geomembrane (11) on it.

9. A face dam slope membrane underdrain system and method of construction thereof according to claim 8, wherein, The width of the first water trench (1), the second water trench (2) and the water seepage collection trench (5) is greater than or equal to 0.8m, the depth of the first water trench (1) and the second water trench (2) is determined according to the underground water level line (10), the depth of the water seepage collection trench (5) is greater than 1m, the thickness of the first clay water barrier layer (41) above the first graded gravel (91) is at least 0.5m.

10. The face dam slope membrane underdrain system and method of constructing the same of claim 8, wherein, The drainage slope of the first drainage flower pipe (61), the second drainage flower pipe (62), the first drainage solid pipe (71), the second drainage solid pipe (72), the geomembrane water seepage collection drainage solid pipe (73) and the underground water seepage collection drainage solid pipe (74) is greater than 1%.

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