Construction method for filling rockfill dam by controlling content of fine-particle rockfill materials

Abstract

The invention discloses a construction method for filling a rockfill dam by controlling the content of fine-particle rockfill materials, and belongs to the technical field of design and construction of water conservancy and hydropower engineering buildings. According to the construction method for filling the rock-fill dam by controlling the content of the fine particle rockfill materials, the filling quality of the rock-fill dam can be effectively improved, and the particle sizes of the rockfill materials filled in all parts of the rock-fill dam meet the requirement. The construction method comprises the steps that firstly, a rockfill dam body and a rockfill material yard are partitioned, then rockfill material mining and rockfill material filling are conducted in a one-to-one correspondence mode according to the partitions of the rockfill dam body and the partitions of the rockfill material yard, and quality detection is conducted on all filled rockfill dam layers; in the rockfill material transferring process, fine particles with the content exceeding the standard are at least removed from the rockfill materials in the outer side area of the rockfill dam body and / or the filling area of the upper middle portion of the rockfill dam body; and in the process of filling the dam body layers layer by layer, after paving and rolling of the filling layers are completed, scrape-off treatment is conducted on the broken superstandard fine powder layers on the surfaces, and then filling of rockfill materials of the next layer is conducted.

Description

Technical Field

[0001] The invention relates to a construction method, in particular to a construction method for controlling the filling of fine-grained rockfill materials in a rockfill dam, and belongs to the technical field of design and construction of water conservancy and hydropower engineering buildings. Background Art

[0002] As a type of earth-rockfill dam, rockfill dams are widely used worldwide due to their adaptability to topographical and geological conditions, local material resources, low construction cost, and strong stability. The primary fill material for rockfill dams is rockfill. Rockfill is a granular material composed of rock particles of varying sizes interlocked together. High dam projects often require it to possess engineering properties such as high permeability, good compaction properties, high shear strength, strong bearing capacity, and minimal deformation. The particle size range for dam rockfill is wide, with the largest particle size reaching 1000mm, while smaller particles can be less than 0.075mm, representing a typical wide-graded granular material. The fine particle content significantly affects the mechanical properties of rockfill. Excessive fine particle content can compromise the permeability, strength, and deformation characteristics of the rockfill, leading to issues with the dam's seepage stability, slope stability, and deformation stability. Relevant regulations set limits on the gradation continuity and fine particle content of rockfill, requiring no more than 30% for particles smaller than 5mm and no more than 5% for particles smaller than 0.075mm. High dam projects have even stricter requirements.

[0003] With the acceleration of high dam and reservoir construction in China, a number of ultra-high rockfill dams, such as Shuangjiangkou, Rumei, Gushui, Lawa, and Dashixia, are under construction or planned. Rockfill materials for dam construction are commonly mined by explosive blasting. To control and coordinate dam deformation, the gradation of the blasted material must meet design requirements. Investment, environmental protection, and water conservation considerations require that excavated materials from the material yard and project area be fully utilized to minimize waste. However, due to complex and variable engineering geological conditions and the uncertainty of blasting, the excavated and blasted rock from the material yard often contains a high content of fine particles, and conventional methods are difficult to economically and efficiently remove the excess fines. The more efficient advance method is often used during the paving process, but this method is more prone to particle separation, resulting in the concentration and uneven distribution of fine particles. The layered filling and vibratory compaction method used in the rockfill area can easily lead to particle fragmentation, and in severe cases, a compacted fine layer can form on the surface. For example, a quarry at a certain ultra-high rockfill dam had complex lithology, extensive joints and fissures, and the blasting material contained over 30% fine particles. After compaction, the rockfill formed a surface layer of approximately 10 cm thick with excessive fines, creating a significant challenge for construction. This high fine particle content and uneven distribution became a key constraint on the dam's construction quality, construction schedule, and investment.

[0004] The typical characteristics of rockfill dam rockfill construction are large size, complex processes, and long construction times. These projects involve numerous scenarios and construction stages, including material extraction, paving, compaction, and testing. Furthermore, considering investment and efficiency issues, accurately controlling the fine particle content throughout the entire process and over a large area is extremely difficult and involves numerous uncertainties. In the past, there was no mature set of technologies and control requirements for fine particle control in the rockfill construction of high rockfill dams. Current design and construction specifications only required that the fine particle content meet the corresponding requirements and ensure continuous grading. However, the specific construction measures to achieve this goal still relied heavily on controlling blasting parameters during mining. For some rockfill sites with poor lithology, controlling blasting parameters cannot solve the problem of high fine particle content in the blasted material. There is also no mature method to address the problems of particle breakage and fine particle concentration during the filling process. Existing technologies no longer meet current needs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a construction method for controlling the content of fine-grained rockfill material in rockfill dams, which can effectively improve the filling quality of rockfill dams and ensure that the particle size of rockfill materials in various parts of the rockfill dam meets the requirements.

[0006] The technical solution adopted to solve the above technical problems is: a construction method for controlling the content of fine-grained rockfill material in a rockfill dam, characterized in that: the construction method first divides the rockfill dam body and the rockfill material yard into zones, then carries out rockfill mining and rockfill filling in a one-to-one correspondence according to the rockfill dam body zones and the rockfill material yard zones, and timely tests the fine-grained content and compaction index of each rockfill dam layer according to the filling sequence, finally obtaining a rockfill filling body that meets the requirements of rockfill dam filling. In the process of transporting the rockfill materials, at least the rockfill materials in the outer area of ​​the rockfill dam body and / or the filling area in the upper and middle part of the rockfill dam body are removed with excessive fine particles. In the process of filling the dam body layer by layer, the excessive fine powder layer that is broken on the surface after paving and rolling of each filling layer is scraped off before the next layer of rockfill materials is filled.

[0007] Furthermore, when zoning the rockfill dam body, based on the technical requirements for rockfill dam filling and the characteristics of rockfill materials mined in the material yard, the dam is divided from the outside to the inside along the dam length direction with the center bottom of the dam body as the reference, into rockfill I filling area, rockfill II filling area and rockfill III filling area; when zoning the rockfill material yard, based on geological survey information and the technical requirements for rockfill dam filling, the rockfill material yard is divided into rockfill I mining area, rockfill II mining area and rockfill III mining area corresponding to the dam body partitions; when filling the rockfill dam, the rockfill materials mined in the rockfill I mining area, rockfill II mining area and rockfill III mining area correspond to the rockfill I filling area, rockfill II filling area and rockfill III filling area of ​​the rockfill dam body respectively; during the transportation of rockfill materials, at least the fine particles with excessive content in the rockfill materials mined in the rockfill I mining area are preliminarily removed.

[0008] The preferred method of the above scheme is that the zoning of the rockfill material yard is based on the geological survey information including at least the rock mass conditions of the working face of each rockfill material area, and the rockfill dam filling requirements include at least the design strength and grading requirements of the rockfill material required for each rockfill area of ​​the rockfill dam. The specific zoning process is as follows: Combined with the identification of the source of the material, the area with intact rock mass, high strength, relatively uniform lithology and no significant change in the internal lithology was designated as the rockfill material I mining area; based on the development of joints and fissures, the degree of unloading, the distribution of lithology types, and the strictness of fine particle control, the rockfill material II and rockfill material III mining areas were further designated. The rockfill materials in each rockfill mining area are mined independently by on-site blasting. The amount of explosives used in the blasting mining in each rockfill mining area and the relevant blasting parameters such as the spacing between blast holes are determined after testing based on the design grading requirements of each rockfill material.

[0009] Furthermore, the source identification is carried out according to the following steps and requirements: Areas with high rock strength, moderate particle size, and good gradation in the rockfill are identified as useful materials, while areas with low rock strength, small particle size, high fine powder content, or mud and sand impurities are identified as useless materials. During the appraisal process, the strength of the rockfill blocks is determined based on their lithology and in combination with the results of previous tests. Alternatively, the strength can be determined on-site by hammering with tools and through manual observation combined with engineering experience. This can be supplemented by on-site sampling and laboratory testing. The particle size, gradation, and fine particle content are determined on-site through combined on-site identification and prescribed particle screening tests. The useful materials are further divided into rockfill material I, rockfill material II and rockfill material III according to the fine particle content.

[0010] A preferred embodiment of the above scheme is that, during the transportation of the rockfill material, a filter plate with sieve holes is provided at the bottom of the loading box of the transport equipment to remove the fine particles exceeding the content standard. Then, during the transportation of the transport equipment, the fine particles are screened out and flushed into the double-layer bottom plate structure below the filter plate due to the bumps and water flow from the high-pressure water supply points.

[0011] Furthermore, the removal of fine particles exceeding the standard during the rockfill material transportation process also includes setting the excavator's hopper to a grid hopper, and performing arm shaking to preliminarily screen out a portion of the fine particles exceeding the standard during the process of loading the rockfill material into the loading box through the grid hopper.

[0012] The preferred embodiment of the above scheme is that the diameter of the filter holes provided on the filter plate and the curved bottom plate of the grid hopper is 5 to 10 cm, the distance between the filter plate and the bottom of the loading box is not less than 10 cm, and the excavator shakes its arm no less than 3 times.

[0013] Furthermore, when filling the rockfill materials in each rockfill area, a mixed paving method of the advance method and the retreat method is adopted. After paving is completed, it is leveled by a bulldozer and / or an excavator, and then compacted and filled according to the specified compaction parameters. Finally, a bulldozer is used to remove the broken fine powder layer on the surface and roughen the surface.

[0014] The preferred embodiment of the above scheme is that the rolling parameters include the number of rolling passes, the driving route and speed of the rolling machinery; when determining the rolling route, rolling is carried out along a straight route, and the rolling range between two adjacent rolling lines overlaps by at least 10 cm; when scraping off the surface crushed fine powder layer, the scraping operation is carried out 1-2 times by a bulldozer.

[0015] The beneficial effects of the present invention are as follows: the above-mentioned technical solution provided in this application makes full use of the characteristics of the engineering dam body itself and the significant differences in the requirements of relevant specifications for different parts of the dam body, and then combines the distribution characteristics of the material yard itself to carry out zoning mining, zoning identification, marked transportation, zoning paving and filling, and after filling, the surface layer of fine powder exceeding the standard is properly scraped off, thereby achieving the goal of making full use of materials, zoning utilization, proper treatment and controllable quality without significantly increasing the construction process and investment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the partition structure of a rockfill dam involved in the construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to the present invention; Figure 2 Schematic diagram of the structure of the filter plate involved in the construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to the present invention; Figure 3Schematic diagram of the structure of the grid hopper involved in the construction method for controlling the content of fine-grained rockfill material in rockfill dams according to the present invention; Figure 4 The present invention is a flow chart of a construction method for controlling the content of fine-grained rockfill material in a rockfill dam.

[0017] Marked in the figure are: rockfill I filling area 1, rockfill II filling area 2, rockfill III filling area 3, filter plate 4, screen hopper 5, and filter hole 6. DETAILED DESCRIPTION

[0018] like Figures 1 to 4 The present invention provides a construction method for controlling the fine-grained rockfill content in a rockfill dam, which can effectively improve the filling quality of the rockfill material in various parts of the rockfill dam, ensuring that the particle size of the rockfill material meets the requirements. The construction method first divides the rockfill dam body and the rockfill material yard into zones, then carries out rockfill mining and rockfill filling in a one-to-one correspondence between the rockfill dam body zones and the rockfill material yard zones, and timely tests the fine-grained content and compaction index of each rockfill dam layer according to the filling sequence, ultimately obtaining a rockfill body that meets the rockfill dam filling requirements. In the process of transporting the rockfill material, at least the rockfill material in the outer area of ​​the rockfill dam body and / or the middle and upper filling area of ​​the rockfill dam body is removed of fine particles that exceed the standard. In the process of filling the dam body layer by layer, the fine powder layer that exceeds the standard and is broken on the surface after paving and rolling of each filling layer is scraped off before the next layer of rockfill material is filled. The above-mentioned technical solution provided by this application fully utilizes the characteristics of the engineering dam body itself and the characteristics that the requirements of the relevant specifications for different parts of the dam body are significantly different. In combination with the distribution characteristics of the material yard itself, the zoning mining, zoning identification, marking and transportation, zoning paving and filling are carried out. After filling, the surface layer of fine particles and fine powder that exceed the standard is appropriately scraped off, thereby achieving the goals of making full use of materials, zoning utilization, appropriate treatment, and controllable quality without significantly increasing the construction process and investment costs. In short, the core of the technical solution of this application is to carry out zoning mining and zoning filling, and to remove excessive fine particles during transportation after mining is completed, as well as timely remove excessive fine powder layers during filling, so as to achieve the purpose of improving the quality of the rockfill dam body without significantly increasing the construction process and investment costs.

[0019] In combination with relevant industry regulations and the physical and chemical properties of the rockfill material yard itself, this application divides the rockfill dam body into zones along the dam length with the center bottom of the dam body as the reference, based on the technical requirements for rockfill dam filling and the characteristics of the rockfill materials mined in the yard, from the outside to the inside into rockfill filling area I 1, rockfill filling area II 2 and rockfill filling area III 3; when zoning the rockfill material yard, based on geological survey information and the technical requirements for rockfill dam filling, the rockfill material yard is divided into rockfill mining area I, rockfill mining area II and rockfill mining area III corresponding to the dam body zones; when filling the rockfill dam, the rockfill materials mined in rockfill mining area I, rockfill mining area II and rockfill mining area III are used to fill the rockfill dam body into rockfill filling area 1, rockfill filling area 2 and rockfill filling area III respectively; during the transportation of the rockfill materials, fine particles with excessive particle size from the rockfill materials mined in rockfill mining area I are appropriately removed. Accordingly, when zoning the rockfill material yard in this application, the geological survey information based on which the rockfill material yard is zoned includes at least the rock mass conditions of the working face of each rockfill material area, and the rockfill dam filling technical requirements based on which the rockfill material is zoned include at least the design strength and grading requirements of the rockfill material required for each rockfill material area of ​​the rockfill dam. The specific zoning process is as follows: Combined with the identification of the source of the material, the area with intact rock mass, high strength, relatively uniform lithology and no significant change in the internal lithology was designated as the rockfill material I mining area; based on the development of joints and fissures, the degree of unloading, the distribution of lithology types, and the strictness of fine particle control, the rockfill material II and rockfill material III mining areas were further designated. The rockfill materials in each rockfill mining area are mined independently using on-site blasting. The amount of explosives used in each rockfill mining area and the blasting parameters related to the spacing between blastholes are determined after testing based on the design grading requirements of each rockfill material. The specific operation of material source identification is carried out according to the following steps and requirements: Areas with high rock strength, moderate particle size, and good gradation in the rockfill are identified as useful materials, while areas with low rock strength, small particle size, high fine powder content, or mud and sand impurities are identified as useless materials. During the appraisal process, the strength of the rockfill blocks is determined based on their lithology and in combination with the results of previous tests. Alternatively, the strength can be determined on-site by hammering with tools and through manual observation combined with engineering experience. This can be supplemented by on-site sampling and laboratory testing. The particle size, gradation, and fine particle content are determined through on-site observation combined with prescribed particle screening tests. Useful materials are further divided into rockfill material I, rockfill material II and rockfill material III according to the fine particle content.

[0020] To control the quality of rockfill materials during transportation, and to avoid significantly increasing the number of processes and investment costs, this application removes excessively large particles during the rockfill material transfer process by installing a filter plate 4 with sieve holes at the bottom of the transport equipment's loading box. During transportation, the transport equipment then uses the equipment's turbulence and high-pressure water points to screen out some of the fine particles and flush them into the double-layer bottom plate structure below the filter plate for removal. Removing excessively large particles during the rockfill material transfer process also involves configuring the excavator's hopper as a screen hopper 5. During the process of loading the rockfill material into the loading box through the screen hopper 5, the excavator's arm is shaken to initially remove some of the excessively large particles.

[0021] The diameter of the filter plate 4 and the filter holes 6 set on the curved bottom plate of the grid hopper is 5 to 10 cm, the distance between the filter plate 4 and the bottom of the loading box is not less than 10 cm, and the excavator shakes its arm no less than 3 times.

[0022] Furthermore, as an integral part of dam quality control during the filling process, this application utilizes a mixed approach of advancing and retreating paving for the rockfill in each rockfill area. After paving, the rockfill is leveled using a bulldozer and / or excavator, followed by compaction and filling according to specified compaction parameters. Finally, a bulldozer is used to remove the surface fine powder layer and roughen the surface. Compaction parameters include the number of passes, the compaction machine's route, and the speed. When determining the compaction route, the compaction is performed along a straight path, with at least 10 cm overlap between adjacent compaction lines. When scraping the surface fine powder layer, the bulldozer performs one to two passes.

[0023] In summary, the technical solution provided by this application also has the following advantages: 1. The excavator modified with a grid bucket is used for fine particle screening of rockfill dam materials, realizing efficient and feasible fine particle screening construction for large-scale rockfill materials.

[0024] 2. The conventional single rockfill paving method has been optimized to reduce the concentrated distribution of fine particles and further improve the reliability of rockfill grading.

[0025] 3. The fine powder layer formed by rolling on the surface of the rockfill is systematically scraped away to improve the filling quality of the rockfill.

[0026] 4. The complete set of technologies for fine particle control in large-scale rockfill mining and filling processes was improved and successfully applied. The fine particle content and compaction index were tested to verify the reliability of the proposed method.

[0027] Example 1 The technical problem to be solved by the present invention is to provide a complete construction method which can effectively control the fine particles during loading, transportation and watering when the fine particles of the rockfill material in the quarry are too high, ensure the uniform spreading of the fine particles during the rockfill filling process, and effectively remove the surface broken layer formed during the rockfill rolling process, so as to ensure that the rockfill filling gradation meets the design requirements.

[0028] The technical solution adopted to solve the above technical problems is: according to the functional requirements of the dam body, the dam rockfill materials are divided into rockfill area I, rockfill area II and rockfill area III, and the corresponding fine particle content requirements are strict, moderate and loose, and different technical requirements are proposed respectively.

[0029] A construction method for controlling fine particle content during rockfill loading, transportation, watering, and filling, the construction steps are as follows: S1. This primarily involves zoning and material source identification. Based on the dam rockfill zoning and the rock mass conditions of each area in the material yard, preliminary quarrying areas for rockfill materials I, II, and III are designated. Blasting is then carried out after the designated quarrying zones are established. After the blasting of each blasting unit in the rockfill yard is completed, the owner, design team, supervisor, and construction team are organized to conduct on-site material source identification of the blasted rockfill materials, identifying both useful and non-useful materials. Based on the characteristics of the useful materials, the areas designated for dam rockfill material areas I, II, and III are then divided. The type of rockfill material to be mined in the next blasting unit is then designated based on the rock mass conditions at the tunnel face.

[0030] S2. Carry out quality supervision and control on each process of rockfill material transportation in each zone, mainly including the loading, transportation and watering construction processes of rockfill materials.

[0031] S3. Supervise and control the quality of each process of rockfill filling construction, mainly including the rockfill zoning and marking, rockfill paving, leveling, rolling filling and scraping of fine powder layer after rolling.

[0032] S4. After filling is completed, the permeability and porosity test of the rockfill shall be carried out.

[0033] In step S1: The zoning mining of rockfill materials is mainly based on the rock mass conditions of the tunnel face, combined with the zoning of the dam body rockfill materials and the design strength and grading requirements of the rockfill materials in each zone.

[0034] Zoning mining needs to be combined with material source identification. The zoning is based on the preliminary designation of the rockfill material type to be mined. The area with intact and high-strength face rock mass, relatively uniform lithology, and inferred no significant change in internal lithology is designated as rockfill material I mining area. Based on the development of joints and fissures, the degree of unloading, the distribution of lithology types, etc., combined with the strictness of fine particle control, the rockfill material II and III mining areas are further designated.

[0035] After the mining zones of rockfill materials I, II and III are designated, blasting mining can be carried out. The blasting parameters such as the amount of explosives used in each zone and the spacing between blasting holes should be determined after testing based on the design grading requirements of each rockfill material.

[0036] Material source identification ultimately determines the type of rockfill material. Material source identification: areas in the rockfill material with high rock strength, moderate particle size, and good gradation are identified as useful materials, while areas with low rock strength, small particle size, high fine powder content, or impurities such as mud and sand are identified as useless materials.

[0037] The strength of rockfill blocks can be assessed based on their lithology and in combination with previous test results. Alternatively, the strength can be assessed on-site through observation using tools and engineering experience. If necessary, additional laboratory testing can be performed using samples. Particle size, gradation, and fine particle content are assessed through on-site observation and, if necessary, particle screening tests.

[0038] Useful materials are further divided into rockfill material I, rockfill material II and rockfill material III according to the fine particle content.

[0039] After the source of materials is identified, pennant flags are used to separate useful materials from useless materials, and useless materials are promptly transported to designated storage yards.

[0040] Pennants are also used to demarcate the areas of available materials into rockfill I, rockfill II, and rockfill III. Different colored flags are used to mark these areas, with the words "rockfill I," "rockfill II," and "rockfill III" written on them, respectively. These markings are eye-catching and intuitive, making it easier for all parties involved in the construction to jointly control the quality of the source materials.

[0041] In step S2: The loading and transporting equipment for the rock pile is a "modified excavator" and a "modified dump truck". Each area of ​​rock pile I, rock pile II and rock pile III is equipped with dedicated loading and transporting equipment, and their respective construction is carried out without interfering with each other.

[0042] "Modified excavator" means that the grab bucket of the excavator used to load rock piles is modified into a grille bucket with holes.

[0043] A modified dump truck involves welding an additional layer of steel plate to the original truck bed, creating a double-layer floor structure. The two layers are elevated, with a spacing of 10 cm. Ribs are installed underneath the welded layer, along the direction of the vehicle body, to provide support. Ribs are welded to the truck bed and steel plate on either side, providing support. Ribs are spaced 1 meter apart and have holes in them.

[0044] Holes are arranged at appropriate intervals on the steel plate layer installed at the bottom of the carriage to filter fine particles and separate them from the rockfill.

[0045] A long strip of fine particle storage box is welded at the rear of the carriage along the width of the carriage. The storage box is connected to the middle space of the above-mentioned "double-layer bottom plate structure". When unloading, the filtered fine particles can slide into the storage box.

[0046] A valve is provided at the bottom of the storage box. When the storage box is full, the valve is opened and the material is unloaded at a designated location.

[0047] The front of the "modified dump trucks" are all marked with eye-catching signs such as "Rock Pile I", "Rock Pile II" or "Rock Pile III", indicating the type of rock pile being transported. According to the type of sign, the trucks go to the rock pile area marked with the corresponding colorful flags to load the materials.

[0048] When loading materials in each rockfill area, drivers of "modified excavators" must pay attention to the license plates of the vehicles coming to load the materials. If the type of rockfill materials does not match that of the area, the vehicles must be returned and no material will be loaded.

[0049] Quality inspectors will be set up on site to manage and supervise the orderly construction of each stone pile area in accordance with the above requirements to avoid confusion.

[0050] For rockfill material I, a modified excavator is used to load the corresponding rockfill material into a perforated screen bucket, shake it a specified number of times, and then load it onto the truck. Rockfill materials II and III are loaded directly onto the truck using a modified excavator without shaking, which removes fine particles to a certain extent and improves work efficiency.

[0051] The construction method for fine particle screening of rockfill material I is to first fill the excavator's screen bucket with rockfill material, then continuously shake the excavator's arm to allow fine particles to pass through the screen bucket holes for screening. The remaining rockfill material in the screen bucket is then loaded onto a truck and transported to the dam for filling. The modified screen bucket is filled to approximately 80% of the bucket capacity to prevent the rockfill material from being scattered during the excavator's arm shaking and screening.

[0052] The hole size and spacing of the excavator's modified grille bucket, the excavator's arm shaking amplitude and frequency must be determined based on the actual characteristics of the rock pile and on-site screening and loading tests to ensure that the gradation of the rock pile after screening and loading is within the design range.

[0053] After determining the excavator's arm shaking amplitude and frequency, the subsequent execution will be carried out accordingly. The on-site quality inspector will supervise whether the driver loads the materials as required.

[0054] Monitoring facilities are arranged on site to monitor the screening construction of rockfill materials and to monitor whether the construction procedures of the entire rockfill area are carried out in an orderly manner according to the specific division of labor.

[0055] The cargo compartments of the "modified dump trucks" are all equipped with automatic awnings. After loading is completed, the awnings are opened to cover the piled stones to prevent scattering and dust pollution.

[0056] High-pressure water-adding points are set up during vehicle transportation to fully add water to the rockfill to improve compaction performance, while further flushing fine particles into the "double-layer bottom plate structure" to reduce the fine particle content of the rockfill on the dam.

[0057] In step S3: The rockfill area is demarcated with white lime lines to demarcate the rockfill material I, II, and III. When dump trucks transport rockfill materials to the rockfill area, they drive to the corresponding rockfill partition based on the type of material being transported.

[0058] Quality inspectors must be posted at the rockfill filling surface to supervise the transportation of each vehicle to the corresponding rockfill area. Vehicles that are not marked or that do not transport rockfill materials according to the marked types should not be accepted.

[0059] When unloading the rock pile, a mixture of the advance method and the retreat method is adopted for paving, and the rock pile is leveled with the help of bulldozers, excavators, etc., while the fine particles that are locally concentrated are dispersed.

[0060] During the paving and leveling process of rockfill materials, the paving thickness must be controlled to meet the design requirements.

[0061] After the material is laid and leveled to the designed rolling thickness, it can be rolled and filled according to the designed rolling parameters. The driving route, speed and rolling times of the rolling machinery are monitored and fed back to the monitoring data center in real time as the basis for rolling quality assessment.

[0062] After compaction, a bulldozer is used to scrape off the broken fine powder layer on the surface, which also serves to roughen the filling surface.

[0063] Before scraping fine powder, the bulldozer should plan the route reasonably, try to make the route straight and convenient for construction, and at the same time, the scraping range between two adjacent driving routes should overlap by at least 10 cm to avoid missing construction at the intersection.

[0064] The scraped fine powder is collected and then transported to the designated waste dump. The location where the fine powder is collected is determined according to the fine powder content and the size of the bulldozer's bulldozer shovel. It should be avoided that the bulldozer shovel is filled with fine powder before the bulldozer reaches the collection point.

[0065] The number of times of scraping off fine powder is 1 to 2 times, which will be decided by all parties involved in the construction based on the actual effect of scraping off fine powder.

[0066] In step S4: The quality inspection of rockfill materials after rolling includes fine particle content inspection and compaction index inspection. When the compaction index meets the design requirements but the fine particle content does not meet the requirements, targeted local excavation or secondary scraping construction should be carried out; when the compaction index does not meet the design requirements, targeted re-rolling construction should be carried out, and the surface fine powder layer should be scraped off after rolling; when both meet the requirements, the next layer of filling can be carried out according to the above process.

Claims

1. A construction method for controlling the content of fine-grained rockfill material in rockfill dams, characterized by: The construction method first divides the rockfill dam body and the rockfill material yard into zones, then carries out rockfill mining and rockfill filling in a one-to-one correspondence according to the rockfill dam body zones and the rockfill material yard zones, and timely tests the fine particle content and compaction index of each rockfill dam layer according to the filling sequence, finally obtaining a rockfill body that meets the rockfill dam filling requirements. In the process of transporting the rockfill materials, at least the rockfill materials in the outer area of ​​the rockfill dam body and / or the filling area in the upper and middle part of the rockfill dam body are removed with excessive fine particles. In the process of filling the dam body layer by layer, the excessive fine powder layer that is broken on the surface after paving and rolling of each filling layer is scraped off before the next layer of rockfill materials is filled.

2. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 1, characterized in that: When zoning the rockfill dam body, based on the technical requirements for rockfill dam filling and the characteristics of the rockfill materials mined in the material yard, the dam body is divided into rockfill I filling area (1), rockfill II filling area (2) and rockfill III filling area (3) from the outside to the inside along the dam length direction with the center bottom of the dam body as the reference; when zoning the rockfill material yard, based on the geological survey information and the technical requirements for rockfill dam filling, the rockfill material yard is divided into rockfill I mining area, rockfill II mining area and rockfill III mining area corresponding to the dam body zoning; when filling the rockfill dam, the rockfill materials mined in the rockfill I mining area, rockfill II mining area and rockfill III mining area are used to fill the rockfill I filling area (1), rockfill II filling area (2) and rockfill III filling area (3) of the rockfill dam body respectively; during the rockfill material transportation process, at least the fine particles with excessive content in the rockfill materials mined in the rockfill I mining area are preliminarily removed.

3. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 2, characterized in that: The geological survey information based on which the rockfill material yard is divided shall at least include the rock mass conditions of the working face of each rockfill material area. The rockfill dam filling requirements shall at least include the design strength and grading requirements of the rockfill materials required in each rockfill area of ​​the rockfill dam. The specific division process is as follows: Combined with the identification of the source of the material, the area with intact rock mass, high strength, relatively uniform lithology and no significant change in the internal lithology was designated as the rockfill material I mining area; based on the development of joints and fissures, the degree of unloading, the distribution of lithology types, and the strictness of fine particle control, the rockfill material II and rockfill material III mining areas were further designated. The rockfill materials in each rockfill mining area are mined independently by on-site blasting. The amount of explosives used in the blasting mining in each rockfill mining area and the relevant blasting parameters such as the spacing between blast holes are determined after testing based on the design grading requirements of each rockfill material.

4. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 3, characterized in that: Material source identification is carried out according to the following steps and requirements: Areas with high rock strength, moderate particle size, and good gradation in the rockfill are identified as useful materials, while areas with low rock strength, small particle size, high fine powder content, or mud and sand impurities are identified as useless materials. During the appraisal process, the strength of the rockfill blocks is determined based on their lithology and in combination with the results of previous tests. Alternatively, the strength can be determined on-site by hammering with tools and through manual observation combined with engineering experience. This can be supplemented by on-site sampling and laboratory testing. The particle size, gradation, and fine particle content are determined on-site through combined on-site identification and prescribed particle screening tests. The useful materials are further divided into rockfill material I, rockfill material II and rockfill material III according to the fine particle content.

5. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 2, 3 or 4, characterized in that: During the rockfill material transportation process, the fine particles exceeding the standard are removed by setting a filter plate (4) with sieve holes at the bottom of the loading box of the transport equipment, and then, during the transportation of the transport equipment, through the bumps and the water flow from the set high-pressure water adding point, some of the fine particles are screened out and washed into the double-layer bottom plate structure below the filter plate for removal.

6. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 5, characterized in that: The removal of fine particles exceeding the standard during the rock pile transportation process also includes setting the hopper of the excavator as a grid hopper (5), and performing arm shaking to preliminarily screen out a portion of the fine particles exceeding the standard during the process of loading the rock pile into the loading box through the grid hopper (5).

7. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 6, characterized in that: The diameter of the filter plate (4) and the filter holes (6) provided on the arc-shaped bottom plate of the grid hopper is 5 to 10 cm, the distance between the filter plate (4) and the bottom of the loading box is not less than 10 cm, and the number of times the excavator shakes its arm is not less than 3 times.

8. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 7, characterized in that: When filling the rockfill materials in each rockfill area, a mixed paving method of the advance method and the retreat method is adopted. After paving, it is leveled by a bulldozer and / or excavator, and then compacted and filled according to the specified compaction parameters. Finally, a bulldozer is used to remove the broken fine powder layer on the surface and roughen the surface.

9. The construction method for controlling the content of fine-grained rockfill material in a rockfill dam according to claim 8, characterized in that: The rolling parameters include the number of rolling passes, the driving route of the rolling machinery and the speed; when determining the rolling route, rolling is carried out along the straight route, and the rolling range between two adjacent rolling lines overlaps by at least 10 cm; when scraping off the surface crushed fine powder layer, the scraping operation is carried out 1-2 times by a bulldozer.

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