Reservoir deep foundation reservoir bottom composite membrane anti-seepage structure and construction technology

Abstract

The invention discloses a reservoir deep foundation reservoir bottom composite membrane anti-seepage structure and a construction technology, and belongs to the technical field of reservoir construction. A reservoir deep foundation reservoir bottom composite membrane anti-seepage structure comprises an intercepting and sewering ditch, a drainage system used for drainage is arranged in the intercepting and sewering ditch, the reservoir deep foundation reservoir bottom composite membrane anti-seepage structure further comprises a blind ditch drainage system, the blind ditch drainage system is communicated with the intercepting and sewering ditch, a geomembrane is laid on the end face of the top of the blind ditch drainage system, and a geotechnical blind pipe is arranged in the blind ditch drainage system; the blind ditch drainage system communicated with the cut-off ditch is formed in the reservoir bottom, the geotechnical blind pipe is laid in the blind ditch drainage system, water or gas permeating underground can be discharged into the cut-off ditch through the geotechnical blind pipe, the drainage efficiency and the safety of the geomembrane are improved, the risk that the geomembrane is floated and broken due to gas expansion is avoided, and the safety of the geomembrane is improved. Therefore, the anti-seepage effect of the reservoir can be obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir construction, and in particular to a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir and a construction process. Background Art

[0002] my country has built more than 1,000 plain reservoirs. For example, in the Huanghuaihai Plain, due to the frequent interruption of the flow of the lower reaches of the Yellow River and the Haihe River Basin, cities such as Jinan, Binzhou, Dongying, Dezhou, and Cangzhou have built a number of plain reservoirs to divert and store water for year-round use. As a result, a large number of reservoir bottom anti-seepage projects are being constructed. Especially when anti-seepage construction is carried out in areas with high groundwater levels, the soil aquifer is cut off, and groundwater will continue to infiltrate the reservoir bottom and slopes, causing sand flow, slope instability, pipe bursts, collapse, etc., which seriously endangers the construction of anti-seepage projects. Therefore, during the existing foundation pit construction, deep foundation pits are generally drained and dewatered.

[0003] During the existing foundation pit construction, deep foundation pits are generally drained and dewatered. Traditional deep foundation pit drainage and dewatering are carried out by using tube wells or light well points. Tube wells or light well points require the soil to have strong water permeability. However, when draining and dewatering deep foundation pits in soft soil such as convection plastic silt, due to the weak water permeability of soft soil, the traditional tube wells or light well points cannot pump out water, and the drainage and dewatering effect is poor. The difficulty in draining the surface shallow water and underground pressurized water for a long time has a great negative impact on the construction of the reservoir bottom and earthwork excavation. The most important thing is that it seriously affects the stability of the dam and causes uneven settlement of the local dam. In addition, in order to prevent reservoir water leakage in reservoir construction, a reservoir plate membrane anti-seepage solution is often used. However, during the implementation of the traditional method, problems such as geomembrane inflation and rupture often occur, resulting in aggravated reservoir water leakage. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of poor well drainage effect in the prior art and the problem that the composite membrane will swell and float or even burst after laying, and to propose a composite membrane anti-seepage structure and construction process for the deep foundation bottom of a reservoir.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A composite membrane anti-seepage structure for the deep foundation and bottom of a reservoir comprises an intercepting ditch, a drainage system for drainage is arranged in the intercepting ditch, and a blind ditch drainage system is also included. The blind ditch drainage system is connected with the intercepting ditch, a geomembrane is laid on the top end surface of the blind ditch drainage system, and a geotechnical blind pipe is arranged in the blind ditch drainage system.

[0006] In order to facilitate the discharge of groundwater, preferably, the blind ditch drainage system includes a main drainage ditch and a branch drainage ditch, the branch drainage ditch and the main drainage ditch are both connected to the intercepting ditch, and the geotechnical blind pipe is arranged in the main drainage ditch and the branch drainage ditch.

[0007] In order to facilitate the gathering of groundwater in the intercepting ditch, further, the depth of the intercepting ditch is greater than the depth of the main drainage ditch, and the depth of the main drainage ditch is greater than the depth of the branch drainage ditch.

[0008] In order to increase the effective interception area of ​​groundwater, further, the branch drainage ditches are distributed in a chessboard pattern, and the main drainage ditch is in a "cross" shape.

[0009] Furthermore, the main drainage ditch is in a "M"-shaped structure, and the branch drainage ditches are in a "O"-shaped structure and are arranged in multiple groups.

[0010] Furthermore, the outer wall of the geotextile blind tube is wrapped with a first geotextile, the inner wall of the main drainage ditch is laid with a second geotextile, the geotextile blind tube is buried in the main drainage ditch and the branch drainage ditch respectively through coarse sand, at least two groups of the geotextile blind tube are arranged in the main drainage ditch, and are distributed up and down along the depth direction of the main drainage ditch, the top end surfaces of the main drainage ditch and the branch drainage ditch are laid with at least two layers of third geotextile, and the geomembrane is located between two adjacent layers of the third geotextile.

[0011] A construction process for a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir, further comprising the following steps: Step 1: Measure and stake out according to the reservoir bottom area, groundwater level and surrounding water sources, and then design and excavate the structure of the blind ditch drainage system; Step 2: Lay the permeable pipe in the excavated blind ditch and backfill the laid blind ditch; Step 3: Level and backfill the blind ditch to a certain thickness and lay an impermeable layer on top.

[0012] In the step 1, the reservoir bottom is excavated by the "pouring soil" method, and every two composite membranes form a working surface for orderly excavation.

[0013] In the step 2, the diameter of the permeable pipe used for laying is in the range of 80mm-120mm, and coarse sand is used for backfilling, the particle size of which is in the range of 12mm-20mm and the mud content is less than 3%.

[0014] In step three, the anti-seepage layer adopts "two cloths and one membrane", the lower geotextile is laid in a wavy loose manner, the redundancy is about 1.5%, the width of the seam between the cloths is not less than 10 cm, the suture width is not less than 10 cm, the stitching distance is about 6 mm, and the overlap width of the two adjacent composite membranes is ensured to be not less than 10 cm during laying.

[0015] Compared with the prior art, the present invention provides a composite membrane anti-seepage structure and construction process for a deep foundation and bottom of a reservoir, which has the following beneficial effects: 1. The deep foundation and bottom composite membrane anti-seepage structure of the reservoir has a blind ditch drainage system connected to the interception ditch at the bottom of the reservoir. Geotextile blind pipes are laid in the blind ditch drainage system, which can discharge underground water or gas into the interception ditch through the geotextile blind pipes, thereby improving drainage efficiency and the safety of the geomembrane, avoiding the risk of floating and bursting of the geomembrane due to gas expansion, and thus significantly improving the anti-seepage effect of the reservoir; 2. The deep foundation and bottom composite membrane anti-seepage structure of the reservoir, by designing the blind ditch drainage system into the main drainage ditch and branch drainage ditch, can reduce construction redundancy while ensuring the drainage effect, which helps to improve construction efficiency, save costs and reduce environmental pollution; 3. The composite membrane anti-seepage structure of the deep foundation of the reservoir can filter groundwater and reduce the entry of sediment into the geotextile blind pipes by setting coarse sand, the second geotextile and the geotextile blind pipes with the first geotextile wrapped around the outer wall in the main drainage ditch and the branch drainage ditch. On the other hand, it is convenient to collect groundwater and then drain it into the intercepting ditch, thereby improving the drainage efficiency.

[0016] The parts not involved in the device are the same as the prior art or can be implemented by the prior art. The present invention opens a blind ditch drainage system connected to the intercepting ditch at the bottom of the reservoir, and lays geotextile blind pipes in the blind ditch drainage system. The water or gas that seeps from the ground can be discharged into the intercepting ditch through the geotextile blind pipes, thereby improving the drainage efficiency and the safety of the geomembrane, avoiding the risk of the geomembrane floating or bursting due to gas expansion, and thus significantly improving the anti-seepage effect of the reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of a blind ditch drainage system of a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir proposed by the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the structure of a blind ditch drainage system of a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir proposed by the present invention. Figure 2 ; Figure 3 This is a schematic diagram of the structure of a blind ditch drainage system of a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir proposed by the present invention. Figure 3 ; Figure 4 This is a structural schematic diagram of a main drainage ditch of a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir proposed by the present invention.

[0018] In the figure: 1. intercepting ditch; 2. main drainage ditch; 3. branch drainage ditch; 4. geotextile blind pipe; 5. first geotextile; 501. second geotextile; 502. third geotextile; 6. geomembrane. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0021] Embodiment 1: Refer to Figure 1-Figure 4 , a composite membrane anti-seepage structure for the deep foundation of a reservoir bottom, including a cut-off ditch 1. The cut-off ditch 1 is in a "mouth" shape structure, excavated at the bottom of the reservoir and at least ten meters away from the bottom of the dam. The depth of the cut-off ditch 1 is three meters and the width is ten meters. A drainage system for draining water is arranged in the cut-off ditch 1. The drainage system includes multiple water pumps. There are two to ten groups of water pumps, preferably four groups, evenly distributed in the cut-off ditch 1, and are used to pump and discharge the accumulated water in the cut-off ditch 1 to the outside of the reservoir. It also includes a blind ditch drainage system, which is connected to the cut-off ditch 1. Moreover, a geomembrane 6 is laid on the top end face of the blind ditch drainage system, and a geocomposite drain 4 is arranged in the blind ditch drainage system. By opening a blind ditch drainage system connected to the cut-off ditch 1 at the bottom of the reservoir and laying a geocomposite drain 4 in the blind ditch drainage system, the water or gas infiltrated from the ground can be discharged into the cut-off ditch 1 through the geocomposite drain 4, improving the drainage efficiency and the safety of the geomembrane 6, and avoiding the risk of the geomembrane 6 being lifted or burst due to gas expansion, thereby significantly improving the anti-seepage effect of the reservoir. Moreover, compared with the traditional pipe well or light well point method, the blind ditch drainage system is more convenient and faster to construct, reducing the input of manpower and material resources. At the same time, the blind ditch drainage system has a self-draining function, reducing the workload and cost of later maintenance. In addition, due to the significant anti-seepage effect, the repair cost caused by leakage is reduced, further reducing the total project cost. In addition, the blind ditch drainage system is made of environmentally friendly materials, such as geotextile, geomembrane 6, etc., all of which have good biodegradability and ecological compatibility. While lowering the groundwater level, this system also helps to improve the hydrogeological conditions of the surrounding soil, promoting vegetation growth and ecological restoration. This is of great significance for protecting the environment around the reservoir and maintaining ecological balance.

[0022] Refer to Figure 1-Figure 3Here, the blind ditch drainage system includes a main drainage ditch 2 and a branch drainage ditch 3. The branch drainage ditch 3 and the main drainage ditch 2 are connected to the interception ditch 1, and the geotextile blind pipe 4 is respectively arranged in the main drainage ditch 2 and the branch drainage ditch 3. When in use, by designing the blind ditch drainage system as the main drainage ditch 2 and the branch drainage ditch 3, while ensuring the drainage effect, the construction redundancy is reduced, which helps to improve the construction efficiency, save costs and reduce environmental pollution.

[0023] Reference Figure 1-Figure 3 Here, the depth of the intercepting ditch 1 is greater than the depth of the main drainage ditch 2, and the depth of the main drainage ditch 2 is greater than the depth of the branch drainage ditch 3. The width of the blind ditch drainage system ranges from 300mm to 1000mm, and the depth ranges from 500mm to 2000mm. Here, we prefer the main drainage ditch 2 to have a depth of 700mm and a width of 400mm, and the branch drainage ditch 3 to have a depth of 500mm and a width of 300mm.

[0024] Reference Figure 1 and Figure 2 Here, the branch drainage ditches 3 are distributed in a chessboard pattern, and the main drainage ditch 2 is in a "cross" shape, forming a "field" shape structure with the interception ditch 1. By designing the branch drainage ditches 3 to be distributed in a chessboard pattern, the effective interception area of ​​groundwater can be increased, and the protective effect of the geomembrane 6 can be increased.

[0025] Reference Figure 4During the excavation of the main drainage ditch 2 and the branch drainage ditch 3, the geotextile blind pipe 4 is laid in the main drainage ditch 2 and the branch drainage ditch 3 while excavating, and during the laying of the geotextile blind pipe 4, the main drainage ditch 2 and the branch drainage ditch 3 are backfilled in time, and then a geomembrane 6 is laid on the end surface after backfilling to achieve the anti-seepage effect of the reservoir bottom. The specific structure is: the outer wall of the geotextile blind pipe 4 is wrapped with a first geotextile 5, which can reduce the entry of silt into the geotextile blind pipe 4, and then the inner walls of the main drainage ditch 2 and the branch drainage ditch 3 are laid with a second geotextile 501, including the ditch bottom and the inner walls on both sides, which can improve the seepage effect while reducing the entry of silt into the main drainage ditch 2 and the branch drainage ditch 3, and then, the geotextile blind pipe 4 is buried in the main drainage ditch 2 and the branch drainage ditch 3 respectively through coarse sand, that is, in the second geotextile After the geotextile 501 is laid, a layer of coarse sand is first laid in the main drainage ditch 2 and the branch drainage ditch 3, and then the geotextile blind pipe 4 is laid in the main drainage ditch 2 and the branch drainage ditch 3, and then the main drainage ditch 2 and the branch drainage ditch 3 are backfilled with coarse sand. At least two groups of geotextile blind pipes 4 are arranged in the main drainage ditch 2, preferably two groups, and are distributed up and down along the depth direction of the main drainage ditch 2. Coarse sand is laid between two adjacent groups, and one group is arranged in the branch drainage ditch 3. When in use, by arranging coarse sand, the second geotextile 501 and the geotextile blind pipe 4 with the first geotextile 5 wrapped around the outer wall in the main drainage ditch 2 and the branch drainage ditch 3, on the one hand, groundwater can be filtered to reduce the entry of sediment into the geotextile blind pipe 4, and on the other hand, it is convenient to collect groundwater and then drain it into the intercepting ditch 1, thereby improving drainage efficiency.

[0026] Reference Figure 4 At least two layers of the third geotextile 502 are laid on the top end surfaces of the main drainage ditch 2 and the branch drainage ditch 3, and then the geomembrane 6 is arranged between two adjacent layers of the third geotextile 502. Here we preferably arrange two layers of the third geotextile 502. When in use, by arranging the geomembrane 6 between two layers of the third geotextile 502, the protective effect of the geomembrane 6 can be improved, the damage of the geomembrane 6 caused by the bottom protrusions can be reduced, and the impact of the top objects on the geomembrane 6 can be reduced, thereby improving the anti-seepage effect of the geomembrane 6.

[0027] Reference Figure 4 The coarse sand particle size range is 12mm-20mm, preferably 15mm, and the mud content is less than 3%, which can improve the water seepage effect and reduce the amount of sediment itself, thereby reducing the risk of clogging the geotextile blind pipe 4.

[0028] Reference Figure 4The diameter of the geotextile blind tube 4 ranges from 80mm to 120mm, and here, we prefer 100mm, and the cross section of the geotextile blind tube 4 is honeycomb briquette-shaped. Designing the cross section of the geotextile blind tube 4 to be honeycomb briquette-shaped can increase the strength of the geotextile blind tube 4 on the one hand, and increase the drainage effect on the other hand. While ensuring the drainage effect, reducing the diameter of the geotextile blind tube 4 can reduce the risk of collapse.

[0029] Embodiment 2: Reference Figure 3 , which is basically the same as the first embodiment. On the basis of the first embodiment, we expand the structure of the blind ditch drainage system. Here, we design the main drainage ditch 2 to be in a "M" shape, and the branch drainage ditch 3 is arranged in a "mouth" shape in multiple groups. When in use, by designing the main drainage ditch 2 to be in a "M" shape and the branch drainage ditch 3 to be in a "mouth" shape, although the excavation area of ​​the main drainage ditch 2 is increased, the excavation area of ​​the branch drainage ditch 3 is reduced accordingly, and the geotextile blind pipe 4 is laid more conveniently, thereby improving the construction efficiency.

[0030] Embodiment three: A construction process for a composite membrane anti-seepage structure for a deep foundation bottom of a reservoir, further comprising the following steps: Step 1: Design and excavation of blind ditch drainage system; Blind ditch layout: According to the reservoir geological survey report and groundwater level, the layout and size of the blind ditch are determined. The blind ditch adopts a criss-cross chessboard structure, and a rectangular soil unit with equal side length is enclosed between every two horizontal blind ditches and every two longitudinal blind ditches. The spacing between blind ditches is determined according to calculations to ensure the drainage effect and the safety of geomembrane 6; Excavation of blind ditch: Use excavators and other equipment to excavate blind ditch, and ensure that the excavation width, depth and bottom flatness meet the design requirements. During the excavation process, pay attention to protecting the surrounding geological structure to avoid damage to the reservoir foundation; Step 2: Lay pipes and backfill blind ditch drainage system; Lay a geotextile blind pipe 4 in the excavated blind ditch, and then backfill with coarse sand; Step 3: Laying the anti-seepage layer; After the blind ditch is backfilled, an anti-seepage layer is laid on the top end face of the blind ditch. The anti-seepage layer is preferably "two cloths and one membrane", that is, a layer of geomembrane 6 is sandwiched between two layers of geotextiles, which can not only improve the anti-seepage effect, but also improve the safety of the geomembrane 6.

[0031] In step one, the reservoir bottom is excavated using the "pour soil" method, with two composite membranes forming a working surface and excavated in an orderly manner. The base elevation is checked according to the control piles and leveling points, and no over-excavation or under-excavation is allowed. This provides strong guarantees for the subsequent reservoir bottom anti-seepage construction in terms of "quality" and "quantity".

[0032] In step 2, the diameter of the permeable pipe used for laying is in the range of 80mm-120mm, and coarse sand is preferably used for backfilling, with a particle size range of 12mm-20mm and a mud content of less than 3%. The requirements for the base surface after backfilling are "three degrees": (1) Flatness: ±5cm / 2m, flat and straight; (2) Compactness: Geotechnical materials can only be laid on the soil after it has been compacted with a light flat roller; (3) Cleanliness: There must be no sharp-edged debris such as reed roots, rubble, rocks, gravel, concrete particles, and sharp corners of shells on the base surface.

[0033] In step three, the anti-seepage layer adopts "two cloths and one membrane". The lower geotextile is laid in a wavy loose manner with a redundancy of about 1.5%. The width of the seam between the cloths is not less than 10cm, and the suture width is not less than 10cm. The stitch length is controlled at about 6mm during suturing, and the connection surface is moderately tight and naturally smooth. The composite membrane is laid in an environment with a temperature above 5°C, a wind force below level 4, and no rain or snow. It is laid manually. When laying, ensure that the overlap width of the two adjacent composite membranes is not less than 10cm. The membrane at the joint should be flat, with moderate tightness so as not to form a "fish mouth", and the overlap width is not less than 10cm. After welding is completed, it is subjected to quality inspection. The laying method of the upper geotextile is the same as that of the lower geotextile.

[0034] The specific steps are: 1. Blind ditch drainage system: 1. Blind ditch excavation: Before digging the blind ditch, accurately lay out the design section (30cm×30cm) and sprinkle the gray line. The blind ditch is set up in strips of 50m×50m. A measurement control pile is set up at each check valve, the check valve number is marked, and a colorful flag is erected at the check valve to indicate it. Regularly check the missing and damaged measurement points and make corrections in time.

[0035] Use a small excavator to dig the blind ditch. After excavation, it is manually trimmed according to the designed size. The soil after the groove is discarded at the edge of the ditch.

[0036] 2. Burying of soft permeable pipe (geotextile blind pipe 4) and installation of check valve: After the blind ditch excavation is completed and accepted, the soft permeable pipe installation construction is carried out. First, the 300g / m2 geotextile is laid flat and pressed along the foot of the blind ditch to make the geotextile close to the periphery of the blind ditch. Then, 10cm thick medium-coarse sand is manually backfilled, and then the soft permeable pipe is laid. The second layer of sand is filled while the soft permeable pipe is laid to ensure that the center of the pipe body is consistent with the center of the blind ditch. Finally, the upper layer of sand is manually leveled and compacted.

[0037] Before installing the check valve, first compact the medium sand around the lower permeable pipe, then lay the lower geotextile of the PE membrane, install the gas collecting base of the check valve on the top surface of the geotextile under the anti-seepage membrane, align the center of the gas collecting base with the center of the upward permeable pipe, and then lay the PE membrane. Cut the PE membrane with a wallpaper knife at the bolt position of the gas collecting base and the outlet position of the gas collecting assembly to fit the PE membrane, then heat the geomembrane 6 with a hot air gun and press it by hand to match the size of the base, then cover the gas collecting cover and tighten it with bolts, and the gas collecting base and the gas collecting cover clamp the anti-seepage membrane to achieve the connection between the gas collecting assembly and the anti-seepage membrane. In order to ensure a tight connection, add a rubber pad on the upper and lower PE membranes respectively.

[0038] Use a stainless steel bellows to connect the outlet of the gas collection assembly and the inlet of the exhaust valve assembly. The bellows are vertically pre-buried inside the soil-covering weight layer on the top of the anti-seepage membrane, and a certain length of the upper bellows is reserved to prevent siltation at the bottom of the reservoir. There are four hanging point bolts on the top of the exhaust valve assembly, which are used to fix the exhaust valve assembly on the top surface inside the protective cover. The protective cover uses reinforced concrete prefabricated parts with a height of 70cm. An exhaust port is set on one side of the prefabricated part, and the height is 50cm above the bottom of the reservoir. The reserved size of the exhaust port meets the requirements of personnel for installing corrugated soft permeable pipes.

[0039] 3. Quality control: The soft permeable pipe should be installed in the center of the blind ditch. The coarse sand backfill of the blind ditch should be full and dense. Use a four-way connection at the intersection of the blind ditch. Use a five-way connection at the check valve position. The connection between the soft permeable pipe and the four-way or five-way connection should be wrapped and overlapped with geotextile.

[0040] During the installation and construction of the check valve, the technical staff of the project department will follow up and guide the installation throughout the process. When covering the soil after the installation is completed, it is strictly forbidden to use machinery to approach the filling soil within a radius of 1m around the check valve. The soil should be filled manually in layers to the designed elevation, and the concrete base and bellows should not be disturbed to ensure that the check valve is not damaged.

[0041] 2. Laying and sewing of the lower geotextile (third geotextile 502): 1. Construction method: Before laying the lower layer of geotextile, check whether the incoming geotextile is qualified. Workers should check whether there are clay lumps larger than 2 cm and other sharp objects and other debris on the laying base surface, and remove them in time. After the geotextile is unfolded, check the appearance quality of the geotextile. No thread adjustment, defect impurities are allowed. Record and repair any mechanical damage and other defects. Replace any serious ones.

[0042] The geotextile is laid manually. In order to facilitate splicing and prevent stress concentration, the geotextile is laid in a wavy loose manner with a redundancy of about 1.5%. The geotextile in the center is laid in a zigzag shape and flattened in time after being spread out. The geotextile is required to fit the foundation surface smoothly without protrusions and wrinkles. Construction workers wear flat cloth shoes or soft rubber shoes. It is strictly forbidden to wear spiked shoes and hard-soled shoes to avoid stepping on the geotextile. Non-related personnel are prohibited from staying on the cloth or performing other non-related operations. If the geotextile is found to be damaged during construction, it should be repaired in time. During laying, the width of the seam between cloths should not be less than 10cm.

[0043] When laying, the geotextile should be placed close to the laying base and flattened to avoid overhead, so as to prevent the geotextile and the membrane on it from being torn after covering with soil. During the laying process, it is forbidden to place construction machinery and equipment directly on the geotextile, and it is forbidden to perform any operations unrelated to the laying of geotechnical materials on the geotextile. To prevent damage by strong winds, all geotextiles should be pressed down with sandbags or soft heavy objects during the laying period.

[0044] The geotextile is sewn with a portable sewing machine, and the sewing width is not less than 10cm. During construction, one person holds the cloth and the other sews at a moderate speed. All sewing must be done continuously, and point sewing is not allowed. The stitch length is controlled at about 6mm during sewing, and the connection surface is moderately tight and naturally smooth.

[0045] 2. Quality control: The project department's quality inspection personnel should follow up and inspect as the construction progresses, and proceed to the next process only after the inspection is qualified.

[0046] All geotextile seams must be inspected by hand-tear method and signed and confirmed by the joint acceptance team.

[0047] The suture lines of the overlapping parts of the geotextile should be straight and the stitches should be even. Make sure that no soil is trapped in the geotextile when suturing.

[0048] If there are skipped stitches at the suture joint, make sure the skipped stitches at the overlapping areas are re-sewn.

[0049] 3. Laying and welding of geomembrane 6: The geomembrane 6 can be laid only after the lower geotextile has been laid and sewn and passed the joint acceptance.

[0050] 1. Laying of geomembrane 6: (1) Laying method: The laying should be carried out in weather with a temperature above 5℃, wind force below level 4, and no rain or snow. After laying, check the appearance quality of the geomembrane 6. No sand holes, impurities or spots are allowed on the geomembrane 6. Record and repair mechanical damage and other defects. Replace the serious ones. The laying direction is horizontal rolling along the north-south direction of the reservoir area.

[0051] Use manual rolling to ensure that the overlap width of two adjacent geomembranes is not less than 10cm. The membrane at the joint should be flat, with moderate tightness, so as not to form a "fish mouth".

[0052] In order to facilitate welding and prevent stress concentration, the geomembrane 6 is laid in a wavy loose manner with a redundancy of about 1.5%. The geomembrane 6 located in the center is laid in a zigzag shape and flattened in time after being spread out. The geomembrane 6 is required to be pressed flat and close to the lower geotextile to avoid overhead and without convex wrinkles. When the laying area is irregular in shape, its relevant dimensions are measured and then cut according to the actual situation.

[0053] To prevent damage from strong winds, sandbags or soft heavy objects should be used to press the edges and joints of the geomembrane 6 during laying until the protective layer is completed. The geomembrane 6 laid on the same day should be fully welded on the same day.

[0054] (2) Laying quality control: On-site construction workers should wear flat cloth shoes or soft rubber shoes, and are strictly prohibited from wearing spiked shoes to avoid damaging the geomembrane 6. During the laying process, avoid unloading concrete blocks directly on the geomembrane 6, do not use pointed steel bars as prying tools, avoid hitting stones on the geomembrane 6, and avoid any construction operations that may cause damage to the geomembrane 6.

[0055] After laying, the laying quality should be inspected, mainly by visual inspection, and the uneven, irregular, and potentially welding-affecting parts should be adjusted. Walking on the membrane and carrying tools should be minimized. Any objects that may cause harm to the membrane should not be left on the membrane or carried on the membrane to avoid accidental damage to the membrane.

[0056] During the laying process, check the appearance of the geomembrane 6 at any time for defects such as damage, wrinkles, pitting, holes and creases. If any defects are found, mark them, replace the material or make repairs.

[0057] 2. Welding of geomembrane 6: Geomembrane 6 welding is carried out by Leicester LST800 geomembrane 6 welding machine, using double-track hot melt welding method. The welds are two-pass and the two ends are closed so that the sealing of the enclosed space formed by the weld can be tested; the tensile strength of the joint is not lower than the strength of the parent material; for areas that the double-track hot melt welding machine cannot reach or in other special circumstances, hot air gun hot melt extrusion welding can be used.

[0058] (1) Welding preparation: Before welding, the weld joint surface should be cleaned to remove oil, dust and other debris. The welding area must not have scratches, stains, moisture, dust and other impurities that affect the welding quality to ensure that the membrane surface is clean.

[0059] Before formal welding, it is usually necessary to test weld a test sample of not less than 300×1000mm on site, with an overlap width of not less than 10cm. Test welding is carried out according to the initially determined equipment welding parameters, and then a tear test is performed. If the parent material is torn but the weld is not torn, it is qualified. If the test is qualified, the set welding parameters can be used for formal welding; otherwise, the machine is re-adjusted for test welding until the test is qualified. Generally, the creeping speed is controlled to be 2.5~4.0m / min, and the test welding temperature is between 350~400℃.

[0060] (2) Geomembrane 6 welding: The welding process of geomembrane 6 is to adjust the pressure, set the temperature and creeping speed, then load the membrane into the machine and start the motor.

[0061] Welding of geomembrane 6 is carried out according to the creeping speed and welding temperature determined by the test welding. Dead folds are not allowed to be pressed out during welding. The welds must be neat and beautiful, and there must be no slip welding or jumping. Ensure that the longitudinal and transverse weld joints should be in a "T" shape, and the staggered spacing is greater than 500mm. "X" shaped joints are not allowed. A 10mm cavity is left between the welds to check the weld quality.

[0062] The welding power supply of geomembrane 6 should be powered by a DC generator with good voltage stabilization performance. If the grid is used for power supply, a voltage stabilizer must be used. When welding on a slope, the high membrane should be overlapped on the low membrane surface. Welding should not be carried out during rainfall or in strong winds and sand.

[0063] (3) Weld inspection: After the welding of geomembrane 6 is completed, the weld quality must be fully inspected.

[0064] Visual inspection method: Observe whether the weld has defects such as leakage, burns, wrinkles, unevenness, etc.

[0065] Inflation detection method: seal both ends of the 10mm cavity weld to be tested, insert an air needle, inflate to 0.15-0.2MPa, observe for 1-5 minutes, and check the pressure gauge. If the air pressure does not drop, it indicates that the weld is qualified. If a pressure drop occurs and the leaking part cannot be identified by the naked eye, use a manual welding gun to separate and weld it into 4-5 equal parts every 50m, and test the pressure one by one.

[0066] For "T" type nodes or single weld repair points, vacuum testing is carried out grid by grid in 50cm×50cm squares. The vacuum pressure is not less than 0.005MPa, maintained for 30s, and soap solution or detergent is applied. If there is no foaming, it is qualified.

[0067] (4) Repair: When welding, the damaged geomembrane 6 must be cut off in time and welded firmly by hot melt extrusion. After the damaged part of the geomembrane 6 is repaired, another layer of qualified geomembrane 6 with each side length greater than 1m of the damaged part is laid on it, and relevant records are kept.

[0068] Weld repair personnel must be trained in advance, familiar with the principles, operations, and precautions of welding guns, formulate repair plans and repair processes, use the same geomembrane 6 as on-site for trial welding, and only allow on-site repair work when the success rate of repair welding under various conditions reaches more than 95%. All repaired parts must be re-inspected.

[0069] 3. Geomembrane 6 welding quality control: (1) Weld appearance inspection and repair welding: After each weld is completed, the weld needs to be visually inspected: lap width, weld width and cavity width between two welds. The weld should be smooth, straight and smooth, with a clear weld outline and transparent glass state, without burns, bubbles, or false welds. If any problems are found, mark them with a marker and immediately perform repair welding with a hot melt air gun.

[0070] (2) Welding quality inspection: Before the inflation test of geomembrane 6, the starting and ending ends of the welding area of ​​geomembrane 6 should be baked with a hot melt air gun until softened and then pasted tightly to make the cavity of geomembrane 6 in the welding area a closed inflation area for inflation test.

[0071] After the temperature of the weld plugging start and end ends is completely cooled, slowly insert the needle into the cavity between the double welds. The needle should be kept parallel to the geomembrane 6, and the needle should not be shaken to avoid enlarging the needle hole. During the inflation test, do not press or disturb the needle manually. When the needle leaks, 502 glue or AB glue can be used to plug the needle hole. After the test is completed, the needle hole is sealed with a welding gun.

[0072] When the air pressure in the cavity of geomembrane 6 reaches 0.15Mpa, start recording the time and keep it for 60s. If there is no obvious drop in pressure, it is qualified. If the inflation test fails, check and repair welding in time.

[0073] (3) On-site testing regulations: After the inspection is completed, all the holes punched by the air pressure during the inspection should be immediately plugged by extrusion welding. The parts that fail the quality inspection should be marked and repaired in time. The joints with false welding and leaking welding should be repaired in time, and the repaired welding parts should be vacuum tested. Quality inspection should be carried out as the construction progresses, and the next process can be carried out only after the inspection is qualified.

[0074] (4) Common quality problems such as over-welding and leaking welding: Analyze the reasons for over-welding and leaky welding: the welding temperature of the equipment is set too high or too low, the crawling speed of the equipment is too slow or too slow, the voltage is unstable, there is dirt on the double rails of the hot melt machine, there is dew or dirt on the film, etc.

[0075] Measures: Carry out trial welding before welding every day, adjust the welding temperature and creeping speed of the equipment in time according to the test welding results, check and clean the dirt on the double tracks of the hot melt machine in time, complete the welding of the geomembrane 6 laid on the same day, or wipe it clean manually before welding, and use a DC generator with good voltage stabilization performance to supply the welding power supply.

[0076] (5) Acceptance of geomembrane 6 welding: Before laying the upper geotextile, the units divided by the plan layout are inspected and accepted. The inspection adopts the mode of recording + video recording. The records should mark which unit and the coordinates of the four corners of the unit. Finally, all the units of geomembrane 6 are stored by position and handed over to the supervisor for storage, recording, filing and preservation. After the geomembrane 6 is welded, it is covered and protected to avoid direct sunlight to prevent damage.

[0077] 4. Laying and sewing of the upper geotextile (third geotextile 502): This process has the same requirements as the laying and sewing of the lower layer of geotextile, but after laying is completed, attention should be paid to the protection of the surrounding area. The protection method is to roll up the two layers of geotextile together to the edge of the membrane, cover them with colored strips of cloth, etc., and place a sandbag or soft heavy object on it every 10m to press it down.

[0078] 5. Covering the film with soil: 1. Construction method: When the upper geotextile is spliced, laid and accepted, backfill the soil in time. Only when the thickness of the backfill soil is greater than 70cm can the equipment be allowed to enter the membrane.

[0079] The design drawing requires 1.13m thick original soil to be backfilled on the membrane. The excavation and filling of the reservoir bottom soil is constructed by the "soil dumping" method, that is, the excavated soil of the first construction unit is dumped to a nearby temporary storage by a short-arm excavator, and then geotechnical materials are laid. After the paving is completed, the soil of the next construction unit is dumped to this construction section for backfilling and compaction, and the cycle is repeated in sequence.

[0080] When using the excavator "pouring soil" method for construction, the width of each operation section is controlled to be 2 membrane widths (i.e. 16 meters), and the excavator pours the soil on the next working surface onto the connected membrane. In order to ensure that the geomembrane 6 is not polluted by the covering soil, 2 membranes are used for construction, and the lower geotextile is 3 6-meter wide. When the covering soil is poured, the lower geotextile is rolled up and covered on the top of the geomembrane 6 for protection. The covering soil is kept more than 2 meters away from the welding seam of the geomembrane 6.

[0081] 2. Quality control: After the geotechnical materials are laid, they can be backfilled only after passing the inspection. When the backfilled soil layer is thicker than 0.7m, mechanical equipment can be allowed to perform construction operations on the membrane.

[0082] The speed of film laying and covering with soil should be carried out simultaneously to avoid laying the film too quickly, which will leave the film exposed for a long time and accelerate aging. When backfilling the earth protection layer, the soil should be spread from the middle or one side first to drive out the gas under the film.

[0083] When construction machinery crosses the membrane and enters the membrane to work, pay attention to the protection of the membrane edge.

[0084] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A composite membrane anti-seepage structure for a deep reservoir bottom, comprising an intercepting ditch (1), wherein a drainage system for drainage is arranged in the intercepting ditch (1), characterized in that: It also includes a blind ditch drainage system which is connected to the seepage cut-off ditch (1). A geomembrane (6) is laid on the top end face of the blind ditch drainage system, and a geocomposite drain (4) is arranged in the blind ditch drainage system.

2. A reservoir deep foundation composite membrane anti-seepage structure according to claim 1, characterized in that: The blind ditch drainage system includes a main drainage ditch (2) and branch drainage ditches (3). Both the branch drainage ditches (3) and the main drainage ditch (2) are connected to the seepage cut-off ditch (1), and the geocomposite drain (4) is arranged in the main drainage ditch (2) and the branch drainage ditches (3).

3. A composite membrane anti-seepage structure for deep foundation and bottom of a reservoir according to claim 2, characterized in that: The depth of the seepage cut-off ditch (1) is greater than the depth of the main drainage ditch (2), and the depth of the main drainage ditch (2) is greater than the depth of the branch drainage ditches (3).

4. A composite membrane anti-seepage structure for deep foundation and bottom of a reservoir according to claim 2, characterized in that: The branch drainage ditches (3) are distributed in a checkerboard pattern, and the main drainage ditch (2) is in a "cross" shape structure.

5. A reservoir deep foundation composite membrane anti-seepage structure according to claim 2, characterized in that: The main drainage ditch (2) is in a "rice" shape structure, and multiple groups of the branch drainage ditches (3) are arranged in a "square" shape.

6. A reservoir deep foundation composite membrane anti-seepage structure according to claim 2, characterized in that: The outer wall of the geocomposite drain (4) is wrapped with a first geotextile (5), the inner wall of the main drainage ditch (2) is laid with a second geotextile (501). The geocomposite drain (4) is respectively buried in the main drainage ditch (2) and the branch drainage ditches (3) with coarse sand. At least two groups of the geocomposite drain (4) are arranged in the main drainage ditch (2) and are distributed vertically along the depth direction of the main drainage ditch (2). At least two layers of a third geotextile (502) are laid on the top end faces of the main drainage ditch (2) and the branch drainage ditches (3), and the geomembrane (6) is located between two adjacent layers of the third geotextile (502).

7. A construction process comprising the composite membrane anti-seepage structure for the deep foundation and bottom of a reservoir according to any one of claims 1 to 6, characterized in that: It also includes the following steps: Step 1: Conduct measurement and layout according to the bottom area of the reservoir, the groundwater level, and the surrounding water source conditions, and then design and excavate the structure of the blind ditch drainage system. Step 2: Lay a permeable pipe in the excavated blind ditch and backfill the completed blind ditch. Step 3: Level the backfilled thickness of the blind ditch and lay an anti-seepage layer on the top.

8. The construction process of a composite membrane anti-seepage structure for a deep foundation and bottom of a reservoir according to claim 7, characterized in that: In Step 1, the bottom of the reservoir is excavated by the "soil dumping" method, and excavation is carried out with every two composite membranes as a working face.

9. The construction process of a composite membrane anti-seepage structure for a deep foundation and bottom of a reservoir according to claim 7, characterized in that: In Step 2, the diameter range of the permeable pipe used for laying is 80 mm - 120 mm, and the backfill uses coarse sand with a particle size range of 12 mm - 20 mm and a mud content of less than 3%.

10. The construction process of a composite membrane anti-seepage structure for a deep foundation and bottom of a reservoir according to claim 7, characterized in that: In Step 3, the anti-seepage layer adopts a "two-layer geotextile and one geomembrane" structure. The lower geotextile is laid in a wavy relaxation manner with a surplus of about 1.5%. The width of the joint between the geotextiles is not less than 10 cm, the sewing width is not less than 10 cm, the stitch spacing is about 6 mm during sewing, and the lap width of two adjacent composite membranes during laying is not less than 10 cm.

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