A pre-embedded pipe earth-rock dam cutoff wall structure and a defect detection and repair method

Abstract

The application discloses a kind of pre-embedded pipe earth-rock dam cutoff wall structure and defect detection and repair method, "U-shaped" flower pipe is pre-embedded in cutoff wall and is evenly arranged along cutoff wall axis, and flower pipe is filled with colored dye agent;Through dam body seepage pressure monitoring, colored dye agent migrates with seepage and dam downstream water weir seepage flow changes, the position and nature of earth-rock dam seepage can be preliminarily evaluated;Using the "U-shaped" pre-embedded flower pipe in concrete cutoff wall, the defect of cutoff wall can be detected by pre-embedded flower pipe seepage flow detection, pre-embedded flower pipe seepage digital imaging and pre-embedded flower pipe water pressure test;After accurately detecting the defect of cutoff wall, the grouting repair method in cutoff wall pre-embedded pipe uses pre-embedded "U-shaped" flower pipe to carry out local chemical grouting, low disturbance and high efficiency, realize the accurate repair of seepage cutoff wall.

Description

Technical Field

[0001] This invention relates to a pre-embedded pipe earth-rock dam seepage prevention wall structure and its defect detection and repair method, belonging to the field of hydropower and water conservancy engineering technology. Background Technology

[0002] Cut-off walls alter the seepage state of groundwater and intercept seepage, ensuring the seepage stability of earth-rock dams and foundations. They are widely used in seepage prevention projects for newly constructed water conservancy projects and the reinforcement of dilapidated reservoirs. However, with increasing service time, concrete cut-off walls age and crack, creating localized seepage channels within the dam body, which affects the stability of the dam.

[0003] The most direct methods for evaluating the quality of underground cutoff walls are core drilling, water pressure drilling, and elastic wave CT scans performed by drilling holes in the wall. These methods require drilling into the wall, which inevitably causes localized damage to the concrete cutoff wall. Concrete cutoff walls are structurally thin, and drilling and grouting them requires extremely precise drilling angles and is very difficult; a slight mistake could penetrate the wall. On the other hand, non-destructive testing methods for cutoff walls (such as ground-penetrating radar and high-density elastic wave CT) can qualitatively interpret internal defects, but the resulting images are relatively limited and difficult to meet quantitative measurement requirements.

[0004] The difficulty in detecting seepage in cutoff walls lies in the fact that they are concealed works embedded within earth-rock dams. Once seepage occurs, it is necessary to analyze the cause, nature, and location of the leakage. Currently, there is no single, effective, and reliable detection method or technology. For cutoff walls with uncertain seepage nature and location, it is difficult to carry out grouting repairs in engineering practice, and the repair plan often tends to be to build a new cutoff wall, which is more expensive. On the other hand, seepage in earth-rock dams is difficult to detect in the early stages. Once obvious seepage deformation occurs, the dam body has often already suffered serious seepage damage, resulting in huge economic losses. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-embedded pipe seepage barrier structure and a method for defect detection and repair, which can realize the performance monitoring of the seepage barrier of the earth-rock dam. The seepage barrier defect detection and repair method proposed in this invention can accurately detect the seepage parts of the seepage barrier non-destructively, and the seepage barrier can be repaired by grouting inside the pre-embedded pipe.

[0006] Therefore, according to the first aspect of the present invention, the present invention is implemented by the following technical solution:

[0007] A pre-embedded pipe seepage prevention wall structure for earth-rock dams is characterized by comprising multiple "U-shaped" perforated pipes located within the seepage prevention wall of the earth-rock dam. The "U-shaped" perforated pipes are pre-embedded in the middle of each concrete seepage prevention wall pouring section of the seepage prevention wall, and are evenly arranged along the axis of the earth-rock dam. An indicator is filled inside the "U-shaped" perforated pipes.

[0008] The indicator is water-soluble. Further, the indicator is a colored dye; when a through-crack develops in the cutoff wall, the colored dye dissolves in water and migrates with the seepage within the dam body to the downstream slope drainage area, becoming visible and serving as a qualitative evaluation index for cutoff wall leakage. Preferably, different colored dyes can be filled into different "U-shaped" perforated pipes to distinguish leakage in different dam sections. Furthermore, the location and nature of seepage in the earth-rock dam can be preliminarily evaluated by combining the seepage pressure monitoring pipes arranged within the dam body and the seepage flow rate of the downstream weir.

[0009] Furthermore, the "U-shaped" perforated pipe is preferably a perforated perforated pipe, a slotted perforated pipe, or a slotted corrugated pipe. Both ends of the perforated pipe extend to the top of the earth-rock dam. The pipe diameter is 75mm–110mm, the perforation diameter is less than 10mm, and the slot width is less than 5mm. Increasing the perforation rate can reduce the rigidity of the perforated pipe and improve its permeability. Generally, the perforation rate ranges from 30% to 50%, but specific implementation needs to be determined based on shear and compression tests of the anti-seepage wall concrete and the perforated pipe.

[0010] According to a second aspect of the present invention, the present invention is implemented using the following technical solutions:

[0011] Based on any of the above-mentioned defect detection methods for pre-embedded pipe earth-rock dam anti-seepage wall structures, the characteristic is that: using "U-shaped" pre-embedded perforated pipes in the concrete anti-seepage wall, the defects of the anti-seepage wall can be detected accurately and non-destructively. The specific methods include pre-embedded perforated pipe seepage flow detection, pre-embedded perforated pipe seepage digital imaging, and pre-embedded perforated pipe water pressure test.

[0012] The steps for detecting the seepage flow of the pre-embedded perforated pipe include:

[0013] The seepage flow detection of the pre-embedded perforated pipe involves obtaining the seepage flow rate Q per unit time within the pre-embedded "U-shaped" perforated pipe, and calculating the working performance index T of the anti-seepage wall in the measured pouring section. The calculation formula is as follows:

[0014]

[0015] In the formula:

[0016] k is the permeability coefficient of the concrete cutoff wall material.

[0017] H is the height of the anti-seepage wall.

[0018] L is the length of the measured anti-seepage wall casting block along its axial direction.

[0019] W represents the thickness of the impermeable wall.

[0020] h1 and h2 are the upstream and downstream water levels of the earth-rock dam, respectively.

[0021] ρ is the density of water, and g is the acceleration due to gravity.

[0022] P is the additional negative pressure applied inside the pipe; if no negative pressure is applied, then P = 0.

[0023] When 0 < T ≤ 1, the cutoff wall has good working performance; when 1 < T ≤ 2, the cutoff wall has average working performance; when 2 < T ≤ 4, the cutoff wall has poor working performance; when T > 4, the cutoff wall has relatively poor working performance.

[0024] The method for detecting water seepage in the pre-embedded perforated pipe using digital imaging is to insert a digital imaging probe into one end of the pre-embedded "U-shaped" perforated pipe and insert a water pumping pipe into the other end to pump water from the pipe and provide a negative pressure of 0.1 to 0.5 MPa. The water seepage point inside the perforated pipe is located by moving the digital imaging probe.

[0025] The pre-embedded perforated pipe water pressure test involves placing hydraulic plugs at both ends of the pre-embedded "U-shaped" perforated pipe to form a closed water pressure test section inside the pipe. A water pressure stabilization test is then conducted on the test section through a water injection pipe. The hydraulic plugs are moved, and the above steps are repeated to detect the location and amount of seepage in the anti-seepage wall. High-density rubber balls are preferably used as hydraulic plugs, and pressure is provided by a ground hydraulic pump supplying water (or engine oil).

[0026] The performance indicators T mentioned above correspond to the performance evaluation of the cutoff wall, as shown in Table 1. For cutoff walls with "good" or "average" performance, further testing and long-term leakage monitoring can be carried out as needed. For cutoff walls with "poor" or "fair" performance, it is generally necessary to determine the location and nature of the defects and carry out further repair work.

[0027] Table 1 Evaluation of the working performance of the anti-seepage wall

[0028]

[0029] According to a third aspect of the present invention, the present invention is implemented using the following technical solutions:

[0030] The method for repairing defects in the pre-embedded pipe earth-rock dam cutoff wall structure, as described above, is characterized by: using pre-embedded "U-shaped" perforated pipes within the cutoff wall to grout the defective area. One end of the pre-embedded "U-shaped" perforated pipe serves as the repair end, with a hydraulic stopper and grouting pipe inserted to the upper part of the grouting repair section. The other end of the perforated pipe serves as the auxiliary operation end, with a hydraulic stopper and return grout pipe inserted to the lower part of the grouting repair section. The grouting fluid is preferably a modified epoxy grouting fluid or a water-soluble polyurethane grouting fluid, among other chemical grouting materials. The grouting fluid is injected into the cutoff wall defect through openings in the perforated pipe.

[0031] Furthermore: After grouting is completed, excess grout is discharged through the return grout pipe, and the grouting repaired seepage barrier is tested for leakage again. If it passes the test, the hole is cleaned and an indicator is filled in for subsequent seepage barrier monitoring.

[0032] This invention discloses a pre-embedded pipe seepage barrier structure and a method for detecting and repairing seepage barrier defects. This technology is an original innovation in the field of seepage barrier detection and repair. It avoids drilling operations during seepage detection and repair, reducing investment in detection and repair projects and minimizing secondary damage to the seepage barrier. The proposed detection techniques, including in-pipe seepage flow detection, digital seepage imaging, and in-pipe pressure water testing, can accurately detect defects in the seepage barrier. The pre-embedded pipe grouting repair method utilizes pre-embedded "U-shaped" perforated pipes for localized chemical grouting, achieving low disturbance and high efficiency, and enabling precise repair of seepage in the seepage barrier. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the pre-embedded pipe earth-rock dam seepage prevention wall structure proposed in this invention;

[0034] Figure 2 This is a schematic diagram of the axial section of the pre-embedded pipe seepage prevention wall;

[0035] Figure 3 This is a top view of the pre-embedded pipe seepage prevention wall structure;

[0036] Figure 4 This is a schematic diagram showing the layout of the pre-embedded perforated pipes and grouting pipes in the anti-seepage wall;

[0037] Figure 5 This is a schematic diagram of the digital imaging method for detecting defects in the anti-seepage wall proposed in this invention;

[0038] Figure 6 This is a schematic diagram of the pipe pressure water method for detecting defects in the anti-seepage wall proposed in this invention;

[0039] Figure 7 This is a schematic diagram of the local grouting method for repairing defects in the anti-seepage wall proposed in this invention;

[0040] Figure 8 These are schematic diagrams of round hole perforated tubes, slotted perforated tubes, and slotted corrugated perforated tubes.

[0041] In the diagram: 1-Earth-rock dam, 2-Isolation wall, 3-Groove pipe, 4-Base cover boundary line, 5-Slope drainage surface, 6-Drainage ditch, 10-Seepage pressure monitoring pipe, 11-Pressure gauge, 12-Curtain grouting pipe, 13-Grouting pipe fixing frame, 201-Isolation wall crack, 301-Round hole perforated pipe, 302-Slotted perforated pipe, 303-Slotted corrugated pipe;

[0042] 701-Digital imaging probe, 702-Cable, 703-Sealing cap, 704-Computer, 705-Evacuation (water) pipe, 706-Evacuation (water) pump;

[0043] 801-Hydraulic Plug, 802-Liquid Pipe, 803-Hydraulic Pump, 804-Water Injection Pipe, 805-Compression Pump, 806-Water Tank;

[0044] 901-Upper hydraulic stopper, 902-Lower hydraulic stopper, 903-Grouting pipe, 904-Return grout pipe, 905-Grouting pressure pump, 906-Return grout pressure pump, 907-Grouting fluid. Detailed Implementation

[0045] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0046] like Figure 1 As shown, the pre-embedded pipe seepage barrier wall structure of the earth-rock dam provided by the present invention includes a perforated pipe 3, a foundation boundary line 4, a slope-adhering drainage surface 5, and a drainage ditch 6. Simultaneously, seepage pressure monitoring pipes 10 can also be buried within the earth-rock dam upstream and downstream of the seepage barrier wall. The perforated pipe 3 is a U-shaped connecting pipe located inside the concrete seepage barrier wall 2 of the earth-rock dam 1, and is filled with a dye. The axial cross-section of the seepage barrier wall is shown below. Figure 2 As shown, the cutoff wall 2 is driven into the bedrock. Each cast-in-place block of the cutoff wall 2 contains perforated pipes 3, which are evenly distributed along the axis of the cutoff wall. A top-view schematic diagram of the structure is shown below. Figure 3 The perforated pipe 3 is arranged on the central axis of the anti-seepage wall 2. The slope drainage surface 5 is located at the lower part of the downstream face of the earth-rock dam body, which can allow seepage water to flow down the slope into the drainage ditch 6 below it, and at the same time provide a background surface for dye development, making it easy to observe which section of the cast block the seepage water belongs to. The drainage ditch 6 is located at the bottom end of the slope drainage surface 5, connecting all the slope drainage surfaces 5 at the bottom end. Figure 4 The paper demonstrates a method for burying a "U-shaped" flower pipe 3 and a curtain grouting pipe 12. After the "U-shaped" flower pipe is fixed to the curtain grouting pipe 12 by the grouting pipe fixing frame 13, it is placed into the reserved groove of the anti-seepage wall trench. The curtain grouting pipe 12 and the "U-shaped" flower pipe 3 are positioned in the middle of the reserved groove by the fixing frame 13.

[0047] Leakage monitoring of the earth-rock dam cutoff wall is based on a comprehensive assessment using three indicators: changes in downstream flow rate of the measuring weir, changes in head of the seepage pressure monitoring pipe, and the presence of pigment tracers in the pre-embedded perforated pipe. This assessment preliminarily determines whether leakage has occurred in the cutoff wall and identifies its approximate location. When a through-crack forms within the earth-rock dam cutoff wall, creating a leakage channel, the head data reflected by the seepage pressure monitoring pipes 10 upstream and downstream of the cutoff wall changes, and the flow rate of the downstream measuring weir increases. If the crack extends to the pre-embedded perforated pipe 3, the colored dye filling the perforated pipe dissolves in water and permeates to the downstream slope drainage surface 5 and drainage ditch 6, indicating that leakage has occurred in the cutoff wall.

[0048] When leakage indicators suggest the presence of leakage channels in the cutoff wall, further testing of the pre-embedded perforated pipes within the potential leakage area is required. Testing methods include detecting the seepage flow rate inside the pipes, digital imaging detection of water seepage inside the pipes, and pressure testing inside the pipes. Specific implementation methods are as follows:

[0049] ① Clean the hole of the pre-embedded flower pipe 3, rinse the colored dye with water, and if necessary, use a drill bit to clear the blockage inside the pipe.

[0050] ② Detection of seepage flow in pre-embedded perforated pipes. The seepage flow in perforated pipe 3 is measured using a water pump over 30-60 minutes and converted to a unit seepage flow rate Q. Based on Darcy's law, the working performance index T of the tested pouring section of the anti-seepage wall is derived. The calculation formula is as follows:

[0051]

[0052] In the formula: k is the permeability coefficient of the concrete cutoff wall material, H is the height of the cutoff wall, L is the axial length of the cutoff wall block being tested, W is the thickness of the cutoff wall, h1 and h2 are the upstream and downstream water levels of the earth-rock dam, ρ is the water density, g is the gravitational acceleration, and P is the additional negative pressure applied inside the pipe. During on-site testing, both ends of the perforated pipe 3 can be sealed, and air (water) can be pumped into the pipe to apply a certain negative pressure value P to obtain the seepage volume of the cutoff wall under different permeability pressure gradients. If no negative pressure is applied, then P = 0. The performance index T corresponding to the cutoff wall performance evaluation can be found in Table 1. For cutoff walls with "good" or "average" performance, further testing and long-term leakage monitoring can be carried out as needed. For cutoff walls with "poor" or "fair" performance, it is generally necessary to determine the location and nature of the defects and further carry out cutoff wall repair work.

[0053] ③ For example Figure 5 As shown, digital imaging is used to detect water seepage inside the pipe. A pre-embedded "U-shaped" pipe has one end as the inspection end and the other end as the auxiliary end. A digital imaging probe 701 is placed inside the pipe at the inspection end, and the probe 701 is connected to a computer 704 on the ground via a cable 702. An air (water) extraction pipe 705 is placed inside the pipe at the auxiliary end, connected to a water pump 706 on the ground. A pressure gauge 11 is installed at the extraction end. During detection, both ends of the pipe are first sealed with sealing caps 703 to form a closed space. The air (water) extraction pump 706 is then turned on to apply a stable negative pressure (pressure value 0.1–0.5 MPa) inside the pipe. The digital imaging probe is then slowly lifted from the bottom of the pipe to locate the seepage point on the inner wall of the pipe.

[0054] ④ The anti-seepage wall is tested using a water pressure test, such as... Figure 6As shown, one end of the pre-embedded "U-shaped" pipe serves as the pressure end, and the other end as the auxiliary end. Hydraulic plugs 801 are inserted into the two openings of the perforated pipe 3 to form a sealed pressure section. The hydraulic plug at the pressure end is equipped with a water injection pipe 804, which connects to the ground compressor pump 805 and supplies water through a water tank 806. The hydraulic plugs 801 can be made of high-density rubber balls and are connected to the ground hydraulic pump 803 via a hydraulic pipe 802, providing pressure via water or oil. Before pressure testing, the hydraulic plugs 801 are moved to the pressure test section and filled with oil or water, ensuring the rubber ball surface is tightly against the inner wall of the perforated pipe 3. The hydraulic pump 803 is then adjusted to maintain a constant pressure on the hydraulic plugs. Water is then injected into the sealed section between the plugs to conduct the pressure test.

[0055] The seepage detection method for the anti-seepage wall described in this implementation case includes seepage flow detection in the perforated pipe, digital imaging, and water pressure test. On this basis, it can also be combined with other non-destructive testing methods such as cross-hole ultrasonic testing and high-density seismic influence method to detect the location, nature and cause of seepage in the anti-seepage wall in multiple times and from multiple directions.

[0056] After determining the location of defects in the anti-seepage wall, leakage repair is necessary. This invention, combined with the proposed pre-embedded perforated pipe structure, proposes a leakage repair method involving grouting within the pre-embedded "U-shaped" perforated pipe. A schematic diagram of anti-seepage wall crack repair is shown below. Figure 7 As shown, given the location of crack 201 in the anti-seepage wall, an upper hydraulic plug 901 is inserted from one end of a pre-embedded "U-shaped" perforated pipe 3 to the upper end of the crack, and a lower hydraulic plug 902 is inserted from the other end of the perforated pipe 3 to the lower end of the crack. The upper and lower hydraulic plugs form a sealed grouting space within the perforated pipe 3, covering the seepage crack in the anti-seepage wall. The grouting pipe 903 injects chemical grout into the sealed grouting space through the upper hydraulic plug. The return grouting pipe 904 discharges the grout to the ground through the lower hydraulic plug 902. The pressure of the grouting pipe 903 and the return grouting pipe are controlled by the grouting pressure pump 905 and the return grouting pressure pump 906, respectively. Grouting materials include epoxy, methyl methacrylate, acrylic acid, acrylate, acidic and alkaline water glass, water-soluble, non-water-soluble and elastic polyurethane, urea-formaldehyde resin, chromium lignin, etc. The grouting liquid penetrates deep into the anti-seepage wall crack through openings (or grooves) in the perforated pipe. After grouting is completed, excess grout is discharged through the return grout pipe. The grouting-repaired anti-seepage wall is then tested for leakage again. After the test is passed, the pipe is cleaned and colored dye is filled into the pipe. The subsequent dam seepage is continuously monitored.

[0057] The hydraulic plugs connected to the water injection pipe 804, grout injection pipe 903 and return grout pipe 904 mentioned above can be hydraulic plugs with connecting pipes. The water injection pipe 804, grout injection pipe 903 and return grout pipe 904 are connected to the connecting pipe joints of the hydraulic plugs. Water is injected into the detection area, or grout is injected into the repair area, and grout is returned from the repair area through the connecting pipes.

[0058] like Figure 8As shown, the present invention preferably uses a perforated perforated pipe 301, a slotted perforated pipe 302, and a slotted corrugated pipe 303. The diameter of the perforated pipe is 75mm to 110mm, the diameter of the perforation is less than 10mm, and the width of the slot is less than 5mm. Increasing the perforation ratio can reduce the rigidity of the perforated pipe and improve the permeability. Generally, the perforation ratio ranges from 30% to 50%, and the specific implementation needs to be calibrated based on the shear and compression tests of the anti-seepage wall concrete and the perforated pipe.

[0059] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for detecting defects in a pre-embedded pipe diaphragm wall structure of an earth-rockfill dam, characterized in that: The pre-embedded pipe earth-rock dam seepage wall structure includes multiple "U-shaped" perforated pipes located within the earth-rock dam seepage wall. The "U-shaped" perforated pipes are pre-embedded in the middle of each concrete seepage wall pouring section of the seepage wall and are evenly arranged along the axis of the earth-rock dam. An indicator is filled inside the "U-shaped" perforated pipes. The defect detection method utilizes the "U-shaped" pre-embedded perforated pipes within the concrete anti-seepage wall to achieve non-destructive and accurate detection of defects in the anti-seepage wall. Specific methods include pre-embedded perforated pipe seepage flow detection, pre-embedded perforated pipe seepage digital imaging, and pre-embedded perforated pipe water pressure test. The steps for detecting the seepage flow of the pre-embedded perforated pipe include: The seepage flow detection of the pre-embedded perforated pipe involves obtaining the seepage flow rate Q per unit time within the pre-embedded "U-shaped" perforated pipe, and calculating the working performance index T of the anti-seepage wall in the measured pouring section. The calculation formula is as follows: In the formula: k is the permeability coefficient of the concrete cutoff wall material. H is the height of the anti-seepage wall. L represents the length of the measured anti-seepage wall casting block along its axial direction. W represents the thickness of the impermeable wall. h1 and h2 are the upstream and downstream water levels of the earth-rock dam, respectively. ρ is the density of water, and g is the acceleration due to gravity. P is the additional negative pressure applied inside the pipe; if no negative pressure is applied, then P = 0. When 0 < T ≤ 1, the cutoff wall has good working performance; when 1 < T ≤ 2, the cutoff wall has average working performance; when 2 < T ≤ 4, the cutoff wall has poor working performance; when T > 4, the cutoff wall has relatively poor working performance. The method for detecting water seepage in the pre-embedded perforated pipe using digital imaging is to insert a digital imaging probe into one end of the pre-embedded "U-shaped" perforated pipe and insert a water pumping pipe into the other end to pump water from the pipe and provide a negative pressure of 0.1 to 0.5 MPa. The water seepage point inside the perforated pipe is located by moving the digital imaging probe. The pre-embedded perforated pipe water pressure test involves placing hydraulic plugs at both ends of the pre-embedded "U-shaped" perforated pipe to form a closed water pressure test section inside the perforated pipe. A water pressure stabilization test is then conducted on the test section through a water injection pipe. The hydraulic plugs are moved and the above steps are repeated to detect the location and amount of water seepage in the anti-seepage wall.

2. The defect detection method of claim 1, wherein: The indicator is a colored dye. When a through crack occurs in the cutoff wall, the colored dye dissolves in water and migrates with the seepage flow in the dam body to the downstream slope drainage area, which can be used as a qualitative evaluation index for cutoff wall leakage.

3. The defect detection method according to claim 1, characterized in that: The indicator is soluble in water.

4. The defect detection method according to claim 1, characterized in that: The "U-shaped" perforated pipe is a perforated perforated pipe, a slotted perforated pipe, or a slotted corrugated pipe. Both ends of the perforated pipe extend to the top of the earth-rock dam. The diameter of the perforated pipe is 75mm to 110mm, the diameter of the perforation is less than 10mm, and the width of the slot is less than 5mm.

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