Construction method for dam anti-seepage curtain grouting

Abstract

The invention discloses a construction method for dam anti-seepage curtain grouting, and relates to the technical field of water conservancy and hydropower engineering.According to the construction method for curtain grouting, construction is conducted according to the principle of sequential densification, a segmented construction method is planned to be adopted, in the same unit, after first-order holes are constructed to be 15 m below bedrock, later-order holes can be constructed, and the next-order holes can be constructed after the first-order holes are constructed to be 15 m below bedrock; the method specifically comprises the steps of pilot hole segmented drilling and coring, water pressing, grouting and hole sealing, first-stage sequential hole segmented drilling, water pressing, grouting and imbedding, second-stage sequential hole segmented drilling, water pressing, grouting and imbedding, third-stage sequential hole segmented drilling, water pressing, grouting and imbedding, quality inspection hole drilling and coring, segmented water pressing and full-hole grouting and hole sealing. The dam anti-seepage curtain grouting construction method has the remarkable beneficial effects in the aspects of guaranteeing the anti-seepage performance of the dam, improving the construction efficiency, ensuring the engineering quality and long-term stable operation and the like, provides a solid guarantee for safe and reliable operation of a water conservancy project, and has important economic, social and environmental benefits.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy and hydropower engineering, and in particular to a construction method for dam anti-seepage curtain grouting. Background Art

[0002] Dam anti-seepage curtain grouting is an important anti-seepage treatment technology in water conservancy projects. There are many common existing technologies. In terms of grouting materials, traditional cement slurry is still the main choice, but with the development of technology, some new chemical grouting materials have also emerged, such as epoxy resin, polyurethane, etc. Cement slurry has a low cost, but its performance may be limited under certain complex geological conditions; chemical grouting materials have good permeability and adhesion, but the cost is relatively high. In terms of drilling technology, common methods include rotary drilling, impact drilling and follow-up drilling. Rotary drilling is suitable for most geological conditions and can ensure the verticality and accuracy of the borehole; impact drilling has a high drilling efficiency in hard rocks; follow-up drilling can effectively prevent borehole collapse. In terms of grouting methods, top-down segmented grouting and bottom-up segmented grouting are two commonly used methods. Top-down segmented grouting can better control the grouting quality, but the construction process is relatively complicated; bottom-up segmented grouting has a high construction efficiency, but the control requirements for grouting pressure are more stringent. In terms of grouting pressure control, existing technologies are usually determined based on factors such as geological conditions, dam structure and design requirements. It is generally achieved by manually or automatically adjusting the pressure of the grouting pump, and combining monitoring equipment to monitor pressure changes in real time.

[0003] In addition, during the construction process, some auxiliary technologies will be used, such as geological survey technology to accurately understand the formation conditions, computer simulation technology to predict the grouting effect, etc. However, the existing technology still has some challenges in dealing with complex geological conditions, deep curtain grouting, and ensuring long-term anti-seepage effects. For example, in karst areas or formations with large cracks, the loss of grouting materials and the difficulty in effective filling still need to be solved; after long-term operation, the anti-seepage performance of the curtain may gradually decrease due to changes in geological conditions and aging of materials.

[0004] Therefore, it is urgent to develop a construction method for dam anti-seepage curtain grouting, which can have significant beneficial effects in ensuring the anti-seepage performance of the dam, improving construction efficiency, ensuring project quality and long-term stable operation, and provide a solid guarantee for the safe and reliable operation of water conservancy projects, which is of great significance to improving the construction level of water conservancy and hydropower projects. Summary of the invention

[0005] In view of the above shortcomings, the present invention provides a construction method for dam anti-seepage curtain grouting, which can have significant beneficial effects in ensuring the anti-seepage performance of the dam, improving construction efficiency, ensuring project quality and long-term stable operation, and provides a solid guarantee for the safe and reliable operation of water conservancy projects. The specific technical scheme is as follows:

[0006] A construction method for curtain grouting of dam anti-seepage, wherein the construction method of the curtain grouting is carried out according to the principle of sequential intensification, and a segmented construction method is proposed. After the first sequence hole in the same unit is constructed to 15m below the bedrock, the next sequence hole can be constructed. The specific procedures include:

[0007] The pilot hole is drilled and cored in stages, water pressed, grouting and hole sealed → the first stage is the sequence holes are drilled and cored in stages, water pressed, grouting and hole sealed → the second stage is the sequence holes are drilled and cored in stages, water pressed, grouting and hole sealed → the third stage is the sequence holes are drilled and cored, water pressed in stages, grouting and hole sealed → the quality inspection hole is drilled and cored, water pressed in stages, and the whole hole is grouted and cast.

[0008] Furthermore, the anti-seepage curtain grouting of the dam is carried out in three stages: the first stage is to carry out curtain grouting of the riverbed foundation below the flood elevation of the dam, and the construction is carried out after the dam is poured to the flood elevation; the second stage is to carry out curtain grouting of the slopes on both sides; the third stage is to carry out curtain grouting of the dam section foundation on both sides of the flood elevation, and the grouting is carried out after the dam body is poured to the dam top elevation. The curtain grouting adopts 100-type rotary drilling rig drilling grouting, the slurry is mixed by the slurry making station on the left bank downstream of the dam, and the grouting pipe or bucket car cooperates with the grouting pump. The grouting construction is strictly carried out in accordance with the "Technical Specifications for Cement Grouting Construction of Hydraulic Structures" (SL62-2014) and other relevant regulations and specifications.

[0009] Furthermore, before the curtain grouting construction begins, it is necessary to conduct curtain grouting tests on slurries with different water-cement ratios, different admixtures and different additives, verify the hole spacing, row spacing, grouting pressure and water-cement ratio, and seek curtain grouting construction parameters and processes suitable for the geological conditions of the grouting area through data analysis.

[0010] Furthermore, the drilling steps are carried out in accordance with the design and construction drawings to determine the opening diameter and the final hole diameter, and measure the hole inclination of the pilot hole, curtain grouting hole, and quality inspection hole; the drilling position deviation of the hole is not greater than 10 cm, and the drilling rig is fixed and stable during drilling, and the drilling rig vertical axis angle is measured with an inclinometer to make it consistent with the designed hole direction; after the drilling of the hole is started, the hole mouth is properly protected with a hole mouth cover to prevent tools and other objects from falling into the hole.

[0011] The bottom hole deviation value is strictly controlled within the allowable deviation specified in the design, see Table 1 below.

[0012] Table 1 Maximum allowable deviation of the bottom of curtain grouting drilling hole

[0013]

[0014] Furthermore, the water pressure step specifically includes flushing the borehole, flushing the fissures and conducting a water pressure test after the drilling of various boreholes is completed, including: flushing the borehole until the return water is clear, and the thickness of the sediment of residual rock powder in the hole at the bottom of the hole after the hole flushing is completed shall not be greater than 20 cm; flushing the fissures, the flushing pressure is 80% of the grouting pressure and not greater than 1.0 MPa, and the flushing time is required to be not less than 30 minutes for a single hole and not less than 2 hours for a series of holes; the pilot holes and quality inspection holes are subjected to top-down segmented drilling, single-point method or five-point method water pressure test, and the general curtain grouting holes are subjected to a simple water pressure test.

[0015] Furthermore, the grouting step adopts silicate cement or pure cement slurry with a strength grade of not less than 32.5, adopts a high-speed mixer to make slurry, a slurry storage bucket to store slurry, a mixing bucket to prepare slurry, and a high-pressure grouting pump to grout. The grouting automatic recorder monitors and records the whole process. It is determined whether to wait for setting according to different situations. The construction parameters such as the grouting water-cement ratio and the conversion principle, the grouting section and the grouting pressure of each section, the control standard of the grouting pressure, and the grouting end standard are followed. The hole-closing inner hole circulation from top to bottom segmented grouting method is adopted. The grouting pipe is not more than 50cm away from the bottom of the hole; the grouting slurry changes step by step from thin to thick. The water-cement ratio (weight ratio) of the curtain grouting cement slurry adopts seven ratios of 5:1, 3:1, 2:1, 1:1, 0.8:1, 0.6:1, and 0.5:1; the water-cement ratio for opening irrigation is 5:1; the cement-clay slurry: cement: clay: water = 1:1:12, 1:1:10, 1:1:8, 1:1:6, 1:1:4, 1:1:3 and other six ratios, and the concentration for opening irrigation is 1:1:12.

[0016] Furthermore, the casting and sealing method is as follows: after the grouting is completed, a 0.5:1 concentrated slurry is injected into the hole to replace the thin slurry in the hole; the orifice pipe is buried, and in the section with intact rock, the depth of the orifice pipe buried in the bedrock is not less than the section length of the grouting section. If the bedrock is broken, the burial depth can be lengthened according to the site conditions after the grouting of the corresponding section is completed; after the orifice pipe is buried, the hole can be swept after solidification for 3-5 days, and the subsequent section drilling and grouting can be carried out only after the orifice pipe is checked to be qualified.

[0017] Furthermore, the grouting termination criteria are: under the design pressure, when the injection rate is no more than 0.4 L / min, continue grouting for 60 min; or when the injection rate is no more than 1 L / min, continue grouting for no less than 90 min; and during the entire grouting process, the grouting time under the design pressure must be no less than 120 min before it can be terminated.

[0018] Furthermore, after the full grouting of each curtain grouting hole is completed, acceptance should be carried out in a timely manner together with the supervisor, and the grouting holes that pass the acceptance should be sealed using the "replacement and pressure grouting sealing method".

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The dam anti-seepage curtain grouting construction method of the present invention has significant beneficial effects in ensuring the anti-seepage performance of the dam, improving construction efficiency, ensuring project quality and long-term stable operation, etc., provides a solid guarantee for the safe and reliable operation of water conservancy projects, and has important economic, social and environmental benefits.

[0021] 2. In terms of anti-seepage arrangement, the present invention scientifically and reasonably plans the boundaries of the curtain line, which can specifically solve the leakage problem after the reservoir is filled with water, ensure the long-term stable operation of the dam, reduce the waste of water resources, and improve the water storage capacity and water resource utilization efficiency of the reservoir; strict anti-seepage standards and carefully designed hole spacing, row spacing and hole sequence effectively improve the anti-seepage performance of the curtain; through multi-sequence construction, the grouting holes are gradually encrypted, the uniformity and reliability of the grouting effect are enhanced, the anti-seepage quality of the dam foundation is ensured, and the risk of safety hazards caused by leakage of the dam is reduced.

[0022] 3. The drilling control and orifice tube casting process of the present invention ensures the accuracy and stability of the drilling, and improves the effect and reliability of grouting. At the same time, the drilling flushing, crack flushing and water pressure test effectively remove impurities in the hole and cracks, enhance the bonding force between the slurry and the bedrock, and improve the integrity and anti-seepage performance of the curtain. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is a construction procedure diagram of dam curtain grouting of the present invention;

[0025] Figure 2 It is the curtain grouting drilling construction drawing of the present invention;

[0026] Figure 3 This is a process flow chart of the grouting construction of the covering layer of the present invention;

[0027] Figure 4 This is a process flow chart of bedrock grouting construction of the present invention;

[0028] Figure 5 It is a process diagram of the anti-seepage grouting step in the present invention. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention, etc. can be purchased from the market or can be prepared by existing methods.

[0030] The present invention mainly solves the grouting construction problem of building a large reservoir and provides a construction method for dam anti-seepage curtain grouting. The construction method of the present invention is further described below in conjunction with an embodiment.

[0031] The total storage capacity of the reservoir of this project is 1.15 million m 3 The total storage capacity of the reservoir is greater than 1 million m 3 Less than 10 million m 3 According to the "Classification and Flood Standards for Water Conservancy and Hydropower Engineering" (SL252-2017) and "Flood Control Standards" (GB50201-2014), the reservoir is small (1) type, the engineering grade is IV, and the maximum dam height is 18.0m. After the reservoir of this project is filled with water, there is a problem of leakage around the dam foundation shoulder to the downstream along the strong weathering zone and strong karst layer on the left and right banks of the dam site. The applicant has tried the construction method of the dam anti-seepage curtain grouting of the present invention.

[0032] Dam site curtain line boundary left bank closed T1f 6-1 、T1f 6-2 Karst layer connected to T1f 7 Relative aquiclude, the right bank closes the T1f4 strong karst layer and connects to T1f 3 Relative to the aquiclude, the bottom boundary closes the medium to strong permeable rock mass and the groundwater level is connected to the weak permeable rock mass; the bottom boundary of the riverbed curtain is controlled by 0.6 times the dam height and the rock mass permeability q≤5Lu. At the same time, combined with the project scale and the hydrological and engineering geological conditions of the dam site, considering that T1f 4 、T1f 6-2 The karst is strongly developed, the groundwater level is low and gentle, the curtain is designed in double rows, the hole spacing is 3m, the row spacing is 1.5m, the hole sequence is constructed in 3 sequences, the secondary curtain focuses on closing the strong karst zone, the grouting on both sides is likely to encounter karst caves and pipelines, which can be combined with plugging treatment, the riverbed curtain hole is about 29m below the foundation surface, and considering that if the left bank is grouting on the surface, the invalid footage will be large, in order to ensure the grouting quality and reduce the invalid footage, the left bank slope is grouting the curtain hole in the tunnel, the diversion tunnel and the water intake and discharge tunnel are city gate tunnel type, with a width of 3.0m and a height of 3.5m (width × height), the tunnel is about 186m long, and the overall engineering geological conditions of the tunnel are good, only the local karst zone and T1f 7The engineering geological conditions in the soft rock area are poor, and lining support treatment is required. The shale belt must be closed in time. Grouting is carried out on the surface of the right bank with a starting elevation of 987.00m. The riverbed section is grouted in the grouting corridor. The edge and bottom boundaries of the curtain grouting can be reasonably adjusted based on the pilot hole test data.

[0033] The anti-seepage curtain grouting of the dam in this embodiment is carried out in three stages: in the first stage, curtain grouting is carried out on the riverbed foundation below the flood elevation of the dam, and the construction is carried out after the dam is poured to the flood elevation; in the second stage, curtain grouting is carried out on the slopes on both sides; in the third stage, curtain grouting is carried out on the foundation of the dam section on both sides of the flood elevation, and grouting is carried out after the dam body is poured to the dam top elevation.

[0034] The curtain grouting of this embodiment is constructed according to the principle of sequential intensification. It is planned to adopt the method of segmented construction. After the first sequence hole in the same unit is constructed to 15m below the bedrock, the next sequence hole can be constructed. The specific construction procedure of curtain grouting in this project section is: segmented drilling and coring, water pressure, grouting, and casting of the pilot hole → segmented drilling, water pressure, grouting, and casting of the I sequence hole → segmented drilling, water pressure, grouting, and casting of the II sequence hole → segmented drilling, water pressure, grouting, and casting of the III sequence hole → drilling and coring of the quality inspection hole, segmented water pressure, and grouting and sealing of the entire hole.

[0035] In this embodiment, a total of 271 boreholes are designed, the total length of the anti-seepage line is 492m, and the total anti-seepage area is about 26,000m 2 The total drilling footage is 16,326m, of which the main curtain has a total footage of 10,729m and the secondary curtain has a total footage of 5,597m.

[0036] Combination Figure 1 The specific steps of the embodiment of the anti-seepage curtain grouting construction method of this project are as follows:

[0037] 1. Curtain grouting test

[0038] The purpose of the curtain grouting test is mainly to verify the design construction parameters (such as hole spacing, row spacing, grouting pressure, water-cement ratio, etc.), and to seek curtain grouting construction parameters and processes suitable for the geological conditions of the grouting area through data analysis, so as to adjust or optimize the construction parameters according to the actual grouting effect and guide the next step of curtain grouting construction.

[0039] (1) Carry out particle analysis, chemical composition and properties, mineral analysis, and determination of capacity, liquid limit, and plastic limit of the clay in the selected material field to determine the material field; carry out tests on the slurry for different water-cement ratios, such as adhesion, plastic viscosity, impermeability, shrinkage, and water seepage, to determine the slurry formula for curtain grouting;

[0040] (2) Carry out the concrete cushion anti-lifting capacity test according to the design technical requirements and propose the maximum grouting pressure suitable for the geological conditions of this project;

[0041] (3) The top-down segmented grouting process for hole closure was tested to determine the curtain grouting parameters.

[0042] 2. Drilling

[0043] Pilot holes, observation holes, curtain grouting holes, quality inspection holes, etc. are all drilled using XY-2PC or XY-2 geological drilling rigs equipped with diamond drill bits for rotary drilling.

[0044] Arrange holes according to the design and construction drawings, determine the opening diameter and final hole diameter, the opening diameter of the pilot hole is Φ91mm, and the final hole diameter is Φ76mm; the opening diameter of the general curtain grouting hole is Φ76mm, and the final hole diameter is Φ59mm; the final hole diameter of the curtain grouting quality inspection hole is not less than Φ76mm; measure the hole inclination of the pilot hole, curtain grouting hole, and quality inspection hole, then drill and coring, uniformly number them according to the coring order, fill in the box with cards, draw a borehole column chart and describe the core; the drilling position deviation of the grouting hole is not more than 10cm, the drilling rig is fixed and stable during drilling, and the drilling rig vertical axis angle is measured with an inclinometer to make it consistent with the designed hole direction; after drilling, the hole mouth is properly protected with a hole mouth cover to prevent tools and other items from falling into the hole.

[0045] The bottom hole deviation value is strictly controlled within the allowable deviation specified in the design, see Table 1 below.

[0046] Table 1 Maximum allowable deviation of the bottom of curtain grouting drilling hole

[0047]

[0048] 3. Water pressure

[0049] After drilling all types of boreholes, the water volume must be increased to flush the boreholes to flush the rock dust out of the hole until the return water is clear. After the hole is flushed, the thickness of the sediment of the residual rock dust in the hole at the bottom of the hole shall not be greater than 20cm.

[0050] All curtain grouting holes should be flushed with pressurized water. The flushing pressure is 80% of the grouting pressure and not more than 1.0MPa. The flushing time is required to be no less than 30 minutes for a single hole and no less than 2 hours for a series of holes. For the hole sections where the return water does not meet the clarification requirements, flushing should be continued. The thickness of the remaining sediment in the hole shall not exceed 20cm. When the flushing effect is not good, high-pressure water pulsation flushing or wind and water rotation flushing can be used. When there is a hole being grouted nearby or the neighboring grouting hole has been completed for less than 24 hours, the fissure flushing shall not be carried out. After the fissure flushing of the grouting hole (section), the hole (section) should be grouting continuously immediately. If the interruption time interval exceeds 24 hours due to some reason, the fissure flushing should be carried out again before grouting.

[0051] Pilot holes and quality inspection holes are drilled from top to bottom in sections, and single-point or five-point water pressure tests are used. General curtain grouting holes are subjected to simple water pressure tests, which can be combined with crack flushing. Five-point and single-point water pressure tests are carried out in accordance with Appendix A of DL / T5148-2001.

[0052] 4. Grouting

[0053] The bedrock grouting in the same section must first complete the consolidation grouting and pass the inspection before curtain grouting can be carried out. For the grouting area equipped with lifting observation equipment, the grouting operation can only be carried out after the lifting observation instrument is installed and the pre-grouting test work is completed. Lifting monitoring should be carried out during the crack flushing, water pressure test and grouting construction process. The observation results should be reported to the supervisor. When the lifting deformation value exceeds the design value, the construction should be stopped immediately, and the supervisor should be reported to jointly study the treatment measures.

[0054] The curtain grouting is made of silicate cement with a strength grade of not less than 32.5. The fineness of the cement is that the residue passing through the 80μm square hole sieve is not more than 5%. Other performance requirements meet the relevant requirements of GB175-2007 standard. The water used for grouting meets the requirements for water for concrete mixing, and the temperature of the water for mixing grouting is not higher than 40℃. A 100-type rotary drilling rig is used for drilling and grouting. The slurry is mixed by the slurry making station on the left bank downstream of the dam. The grouting pipe or bucket car cooperates with the grouting pump to operate, strictly following the "Technical Specifications for Cement Grouting Construction of Hydraulic Structures" (SL62-2014) and other relevant regulations and specifications. A high-speed mixer is used to make slurry, a slurry storage barrel is used to store slurry, a mixing barrel is used to mix slurry, a high-pressure grouting pump is used for grouting, and an automatic grouting recorder is used to monitor and record the entire process.

[0055] The curtain grouting overlay section adopts the hole closed circulation drilling and grouting method, see Figure 3 ; The bedrock section adopts the top-down segmented grouting method with closed hole and internal circulation. Figure 4 The length of the rock foundation grouting section shall not exceed 5m. If there are caves, faults, weak interlayers, etc., the section length should not exceed 3m; the grouting section length of the connection section between the grouting cushion concrete and the foundation is 2m into the rock, and the maximum section length of the final hole section shall not exceed 10m. Determine whether to wait for setting according to different situations, follow the grouting water-cement ratio and transformation principles, grouting sections and grouting pressure of each section, grouting pressure control standards, grouting end standards and other construction parameters, adopt the hole-closing internal circulation from top to bottom grouting method, and the grouting pipe is no more than 50cm away from the bottom of the hole. The grouting slurry changes step by step from thin to thick. The water-cement ratio (weight ratio) of curtain grouting cement slurry adopts seven ratios of 5:1, 3:1, 2:1, 1:1, 0.8:1, 0.6:1, and 0.5:1; the water-cement ratio for initial pouring is 5:1; the cement-clay slurry: cement: clay: water = 1:1:12, 1:1:10, 1:1:8, 1:1:6, 1:1:4, and 1:1:3, and the concentration for initial pouring is 1:1:12.

[0056] The criteria for the end of grouting are: under the design pressure, when the injection rate is no more than 0.4L / min, continue grouting for 60min; or when it is no more than 1L / min, continue grouting for no less than 90min; and during the entire grouting process, the grouting time under the design pressure must be no less than 120min before it can be ended.

[0057] 6. Casting of orifice tube

[0058] After the grouting is completed, 0.5:1 concentrated slurry is injected into the hole to replace the thin slurry in the hole; the orifice pipe is buried. In the section with intact rock, the depth of the orifice pipe buried in the bedrock should not be less than the length of the grouting section. If the bedrock is broken, the burial depth can be lengthened according to the site conditions after the grouting of the corresponding section is completed; after the orifice pipe is buried, the hole can be swept after 3-5 days of solidification, and the subsequent section drilling and grouting can be carried out only after the orifice pipe is checked to be qualified.

[0059] 7. Full hole grouting and sealing

[0060] After the full grouting of each curtain grouting hole is completed, acceptance should be carried out in a timely manner together with the supervisor, and the grouting holes that pass the acceptance should be sealed using the "replacement and pressure grouting sealing method".

[0061] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A construction method for dam anti-seepage curtain grouting, characterized in that: The curtain grouting construction method is carried out according to the principle of sequential intensification. It is planned to adopt the method of segmented construction. After the first sequence hole in the same unit is constructed to 15m below the bedrock, the next sequence hole can be constructed. The specific procedures include: The pilot hole is drilled and cored in stages, water pressed, grouting and hole sealed → The first stage is the sequence holes are drilled and cored in stages, water pressed, grouting and casting → The second stage is the sequence holes are drilled and cored in stages, water pressed, grouting and casting → The third stage is the sequence holes are drilled and cored, water pressed in stages, grouting and hole sealed → The quality inspection hole is drilled and cored, water pressed in stages, and the whole hole is grouted and hole sealed.

2. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The anti-seepage curtain grouting of the dam is carried out in three stages: in the first stage, curtain grouting is carried out on the riverbed foundation below the flood elevation of the dam, and the construction is carried out after the dam is poured to the flood elevation; in the second stage, curtain grouting is carried out on the slopes on both sides; in the third stage, curtain grouting is carried out on the foundation of the dam section on both sides of the flood elevation, and the grouting is carried out after the dam body is poured to the dam top elevation.

3. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: A 100-type rotary drilling rig is used for drilling and grouting. The slurry is mixed by a slurry-making station on the left bank downstream of the dam. Grouting pipes or bucket trucks are used in conjunction with grouting pumps, strictly following the "Technical Specifications for Cement Grouting Construction of Hydraulic Structures" and other relevant regulations and specifications.

4. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: Before the construction of the curtain grouting begins, curtain grouting tests are carried out on slurries with different water-cement ratios, different admixtures and different additives, and the hole spacing, row spacing, grouting pressure and water-cement ratio are verified. Through data analysis, curtain grouting construction parameters and processes suitable for the geological conditions of the grouting area are sought.

5. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The drilling steps are specifically carried out according to the design and construction drawings to arrange the holes, determine the opening diameter and the final hole diameter, and measure the hole inclination of the pilot hole, curtain grouting hole, and quality inspection hole; the drilling position deviation of the hole is not greater than 10 cm, and the drilling rig is fixed and stable during drilling, and the drilling rig vertical axis angle is measured with an inclinometer to ensure that it conforms to the designed hole direction; after the drilling is started, the hole mouth is properly protected with a hole mouth cover to prevent tools and other items from falling into the hole.

6. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The water pressure step specifically includes flushing the borehole, flushing the fissures and conducting a water pressure test after the drilling of various boreholes is completed, including: flushing the borehole until the return water is clear, and the thickness of the sediment of the residual rock powder in the hole at the bottom of the hole after the hole flushing is completed shall not be greater than 20 cm; flushing the fissures, the flushing pressure is 80% of the grouting pressure and is not greater than 1.0 MPa, and the flushing time is required to be not less than 30 minutes for a single hole and not less than 2 hours for a series of holes; the pilot hole and quality inspection hole adopt a top-down segmented drilling, a single-point method or a five-point method water pressure test, and a simple water pressure test is generally adopted for curtain grouting holes.

7. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The grouting step adopts silicate cement or pure cement slurry with a strength grade of not less than 32.5, adopts a high-speed mixer to make slurry, a slurry storage barrel to store slurry, a mixing barrel to prepare slurry, and a high-pressure grouting pump to grout. The grouting automatic recorder monitors and records the whole process. According to different situations, it is determined whether to wait for setting. The construction parameters such as the grouting water-cement ratio and the conversion principle, the grouting section and the grouting pressure of each section, the control standard of the grouting pressure, and the grouting end standard are followed. The orifice is closed and the internal circulation is carried out from top to bottom. The grouting pipe shall not be greater than 50 cm from the bottom of the hole, and the grouting slurry is gradually changed from thin to thick.

8. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The method of the casting step is as follows: after the grouting is completed, a 0.5:1 concentrated slurry is injected into the hole to replace the thin slurry in the hole; the orifice pipe is buried, and in the section with intact rock, the depth of the orifice pipe buried in the bedrock is not less than the section length of the grouting section. If the bedrock is broken, the burial depth can be lengthened according to the site conditions after the grouting of the corresponding section is completed; after the orifice pipe is buried, the hole can be swept after solidification for 3-5 days, and the subsequent section drilling and grouting can be carried out only after the orifice pipe is checked to be qualified.

9. The construction method of dam anti-seepage curtain grouting according to claim 7, characterized in that: The standard for the end of grouting is: under the design pressure, when the injection rate is not more than 0.4L / min, continue grouting for 60min; or when the injection rate is not more than 1L / min, continue grouting for no less than 90min; and during the whole grouting process, the grouting time under the design pressure shall be no less than 120min before it can be ended.

10. The construction method of dam anti-seepage curtain grouting according to claim 1, characterized in that: The full-hole grouting and sealing method is used to seal the grouting holes that have passed the full-hole grouting.

Images