Non-fine concrete slab seepage water taking test system and method

Abstract

The invention relates to the technical field of non-fine concrete slab seepage water taking, in particular to a non-fine concrete slab seepage water taking testing system and method.The system comprises a water supply system, an experimental testing system and a water flow recycling system, and the water supply system comprises a water supply tank, a centrifugal pump and a sediment stirring and concentration monitoring device and can provide sediment-containing water with the stable concentration; the experimental testing system adopts a vertical tower type seepage box, and a matched non-fine concrete slab is arranged in the vertical tower type seepage box; the water flow recovery system accurately measures the seepage flow through a right-angle triangular weir and a water level probe in the water recession channel. According to the testing method, three non-fine concrete slabs with different volume weights are selected, seepage flow data under different water inlet heads are collected, the silting rule is observed and analyzed for a long time, the silting recovery capacity is compared and tested through three desilting methods, and the effect is quantified according to the seepage recovery rate. According to the device and the method, integrated testing of the seepage characteristics, the silting rule and the recovery capability of the sand-bearing water flow is realized, data are accurate, and technical support is provided for seepage water taking engineering in a silt-carrying area.

Description

Technical Field

[0001] This invention belongs to the field of seepage water sampling technology for sand-free concrete slabs, specifically relating to a seepage water sampling test system and method for sand-free concrete slabs. Background Technology

[0002] In the Loess Plateau region, when surface water is selected as an irrigation source, the high sediment content of rivers inevitably leads to siltation in water supply channels and intakes over time. To address this issue, seepage water intake has emerged, with the use of no-fines concrete slabs for seepage water intake being widely applied in engineering practice. This method effectively filters sediment from the water flow, preventing siltation in channels and intakes. No-fines concrete slabs are mainly composed of coarse aggregate, cement, and water, and possess a combination of permeability, filtration, and strength.

[0003] Existing technologies have been used to study the seepage characteristics of no-fines concrete slabs: Jimenez et al. analyzed the relationship between the permeability of no-fines concrete and time, concluding that the permeability of ordinary concrete is much lower than that of no-fines concrete; Yong-YeLi et al. studied the seepage characteristics of no-fines concrete slabs by laying coarse-grained stones with different characteristics, laying a theoretical foundation for the study of seepage characteristics of macroporous media; Huo Liang et al. experimentally studied the permeability coefficient of no-fines concrete, finding that the permeability coefficient gradually increases with increasing porosity; Zhang Zhaohui et al. studied the influencing factors of permeability of permeable concrete, pointing out that the more cement used, the worse the permeability, and the smaller the permeability coefficient and porosity; Fu-ShengWen et al. studied the porosity characteristics of frost-resistant permeable concrete... Tests were conducted to determine the critical Reynolds number of frost-resistant concrete with different pore structures, and it was found that pore pressure is positively correlated with inlet pressure. Deng Liang analyzed the influence of different aggregate construction sequences on the seepage characteristics of no-fines concrete slabs, and found that when the aggregate particle size decreases with the seepage direction, it has a significant impact on the seepage capacity. Yu Xiaolong et al. compared the seepage velocity characteristics of no-fines concrete slabs with single aggregate and multiple aggregates, and found that when laying aggregates containing fine aggregates, the seepage velocity changes less with the increase of inlet water head, which is more suitable for practical engineering. Wang Xinyong obtained an empirical formula for calculating the seepage flow of no-fines concrete slabs when laying heterogeneous filter media through dimensional analysis fitting, and found that the influence of inlet water head on seepage flow is greater than that of the average particle size of heterogeneous filter media.

[0004] Current research on seepage water intake using no-fines concrete slabs is mostly conducted under clear water conditions. However, in actual seepage water intake projects, sand-laden water flows are common. As the flow time increases, the sediment carried by the sand-laden water flow can clog the permeable pores of the no-fines concrete slab, reducing its flow capacity.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] To address the aforementioned technical problems in the existing technology, this invention provides a seepage sampling test system and method for sand-free concrete slabs, which solves the problems that existing studies are mostly based on clean water environments, detached from actual sand-laden water flow conditions, and lack research on the siltation law of sand-free concrete slabs under sand-laden water flow and their recovery ability after siltation.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, a seepage water sampling test system for sand-free concrete slabs includes: a water supply system, a test system, and a water flow recovery system; The water supply system includes a water supply tank, a centrifugal pump, and a water supply pipeline. The water supply tank is equipped with a sediment mixing device and a sediment concentration monitoring device. The test system includes a seepage box and a sand-free concrete slab. The seepage box is a vertical tower structure. The sand-free concrete slab is placed horizontally in the middle of the seepage box and divides the seepage box into upper and lower parts. The upper part of the seepage box is provided with an inlet and the lower part with an outlet. The inlet is connected to the water supply box through a water supply pipe. The centrifugal pump is connected in series with the water supply pipe. The water recycling system includes a drainage channel and a drain pipe. The drainage channel is connected to the outlet of the seepage box, and the drain pipe is connected to the drainage channel.

[0008] Furthermore, a right-angled triangular weir is arranged in the drainage channel. The seepage flow of the sand-free concrete slab can be calculated by measuring the water head on the weir, and a water level measuring needle for reading the water level is provided on the drainage channel.

[0009] Furthermore, the main body of the seepage box is made of steel plate with a thickness of 5mm, and the dimensions of the seepage box are 0.5m in diameter and 3m in height; the dimensions of the no-fines concrete slab are 0.5m in diameter and 0.2m in height, which are adapted to the inner diameter of the seepage box.

[0010] Furthermore, the no-fines concrete slab is made by mixing ordinary Portland cement with a strength grade of C32.5, uniform gravel aggregate with a particle size of 10~20mm, and tap water.

[0011] Furthermore, the test system also includes filter media and a pressure detection device. The filter media is laid on the upper surface of the sand-free concrete slab, and the pressure detection device is installed on the upper part of the seepage box to detect the inlet water head.

[0012] Furthermore, the water supply system also includes valves installed on the water supply pipes.

[0013] Secondly, a method for testing seepage water in a sand-free concrete slab includes: S1. Selecting test subjects: Select subjects with bulk densities of... Three types of sand-free concrete slabs; S2. Set up the test device: hoist the no-fines concrete slab selected in step S1 to the support part inside the seepage box, ensuring that the no-fines concrete slab is placed horizontally. If the seepage box contains filter material, lay the filter material on the surface of the no-fines concrete slab. S3. Introduce sand-laden water and collect basic data: Turn on the centrifugal pump and transport the sand-laden water, which has been mixed by the mud and sand mixing device in the water supply tank, to the infiltration tank through the water supply pipeline. The sand-laden water flows through the filter media and the sand-free concrete slab and then flows into the drainage ditch from the outlet of the infiltration tank. The water level in the drainage ditch is read by the water level probe to calculate the seepage flow rate, and the inlet water head is read by the pressure detection device. S4. Long-term seepage observation: Keep the sand-containing water continuously flowing into the seepage box for 48 hours. Repeat step S3 at 6 hours, 12 hours, 24 hours, 36 hours and 48 hours after the sand-containing water is introduced to collect the seepage flow rate and influent head at each time point and observe the changes in seepage capacity. S5. Siltation recovery capacity test: Remove the silted no-fines concrete slab after the test in step S4, treat it with different sludge removal methods, reinstall it in the seepage box and introduce clean water, collect the seepage flow data after sludge removal, and compare and analyze the siltation recovery capacity.

[0014] Furthermore, in step S3, the sediment concentration of the sand-containing water is 7.5 kg / m³, and the water is introduced into the seepage box only after the sediment concentration monitoring device in the water supply tank confirms that the concentration meets the standard.

[0015] Furthermore, in step S5, the different dredging methods include: manually removing surface mud and sand followed by rinsing with clean water, manually removing surface mud and sand followed by backwashing, and manually removing surface mud and sand followed by high-pressure water gun rinsing.

[0016] Furthermore, in step S5, the siltation recovery capability is quantitatively evaluated by the seepage recovery rate, which is the percentage of the seepage flow after siltation to the clear water seepage flow before siltation.

[0017] Compared with existing technologies, the present invention provides a seepage water intake testing system and method for sand-free concrete slabs. The system includes a water supply, testing, and water recovery system: the water supply system includes a water tank, a centrifugal pump, a sediment mixing and concentration monitoring device, which can provide stable concentrations of sediment-laden water; the testing system uses a vertical tower-type seepage box with a built-in suitable sand-free concrete slab; the water recovery system accurately measures the seepage flow rate through a right-angled triangular weir and a water level gauge in the drainage channel. The testing method selects three sand-free concrete slabs with different densities, collects seepage flow data under different influent heads, analyzes the siltation patterns through long-term observation, and then compares and tests the siltation recovery capacity using three silt removal methods, quantifying the effect by the seepage recovery rate. This invention achieves integrated testing of seepage characteristics, siltation patterns, and recovery capacity under sediment-laden water flow, providing accurate data and technical support for seepage water intake projects in areas with high sediment content. Attached Figure Description

[0018] Figure 1 This is an architectural diagram of the seepage water sampling test system provided in an embodiment of the present invention; Figure 2 A schematic diagram of the experimental sediment particle size distribution curve provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the seepage box structure provided in an embodiment of the present invention; Figure 4 A schematic diagram of the relationship between seepage flow rate and influent head of a sand-containing concrete slab under sand-containing water flow, provided for an embodiment of the present invention. Figure 5 A schematic diagram of the relationship between seepage flow rate and flow time provided in an embodiment of the present invention; Figure 6 The seepage recovery rate of the sand-free concrete slab provided in the embodiments of the present invention under different dredging methods; Figure 7 The seepage recovery rate of the sand-free concrete slab provided in the embodiments of the present invention under different dredging methods; Figure 8 The seepage recovery rate of the sand-free concrete slab provided in the embodiments of the present invention under different dredging methods.

[0019] Explanation of reference numerals in the attached figures: 1. Water supply tank; 2. Sediment mixing device; 3. Sediment concentration monitoring device; 4. Centrifugal pump; 5. Water supply pipeline; 6. Seepage tank; 7. Pressure detection device; 8. Drainage channel; 9. Drainage pipe; 10. Sand-free concrete slab; 11. Filter media. Detailed Implementation

[0020] The technical solution of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0021] It should be noted that, unless otherwise specifically stated, the relative arrangement and numerical expressions of the components and steps described in these embodiments should not be construed as limiting the scope of the invention.

[0022] The following description of exemplary embodiments is merely illustrative and is not intended to limit the invention or its application or use in any way. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail herein, but where applicable, such techniques, methods, and apparatus should be considered part of this specification.

[0023] Example 1 See Figure 1 , Figure 1 This is a diagram of the architecture of a sand-free concrete slab seepage water sampling test system proposed in this invention, which includes: a water supply system, a test system and a water recovery system; M1, the water supply system provides a stable concentration of sediment-containing water for the experiment. The water supply system includes a water supply tank 1, a centrifugal pump 4 and a water supply pipeline 5. The water supply tank 1 is equipped with a sediment mixing device 2 and a sediment concentration monitoring device 3. The water supply tank 1 is equipped with a sediment mixing device 2 and a sediment concentration monitoring device 3. The sediment mixing device 2 continuously stirs the water to ensure that the sediment in the sediment-laden water is always in a suspended state, preventing sediment sedimentation that could lead to uneven concentration and affect the accuracy of the test. The sediment concentration monitoring device 3 monitors the sediment concentration in the water in the tank in real time to ensure that the concentration is stable at the value required for the test. One end of the water supply pipe 5 is connected to the outlet of the water supply tank 1, and the other end extends to the test system. A centrifugal pump 4 is connected in series with the water supply pipe 5 to provide power for the transport of the sediment-laden water. Pipeline valves are used to control the start and stop of the transport of the sediment-laden water and the flow rate. Specifically, it includes: Water supply tank 1: Provides storage and preparation space for sand-containing water for the experiment. It is equipped with components for maintaining the suspension of sediment and for monitoring the concentration. Sediment mixing device 2: By continuously mixing, it ensures that the sediment in the sand-containing water flow in the water supply tank 1 is always in a suspended state, avoiding sedimentation that leads to uneven concentration and affects the accuracy of the test; Sediment concentration monitoring device 3: Installed inside water supply tank 1, it is used to monitor the sediment concentration of the water containing sand in water supply tank 1 in real time, to ensure that the concentration is stable at the value required for the test, and to provide uniform water flow conditions for the test. Centrifugal pump 4: connected in series in the water supply pipeline 5, it provides power for the transportation of sand-containing water and transports the sand-containing water in the water supply tank 1 to the seepage tank 6; Water supply pipe 5: One end is connected to the outlet of water supply tank 1, and the other end extends to the seepage tank 6 of the test system, serving as a channel for transporting sand-containing water from the water supply system to the test system. Valves: Installed on the water supply pipeline 5, used to control the start and stop of sand-containing water transportation, and can also adjust the water flow rate, working with the centrifugal pump 4 to maintain the stability of the inlet water head in the seepage tank 6.

[0024] M2. The test system includes a seepage chamber 6 and a no-fines concrete slab 10. The seepage chamber 6 is a vertical tower structure, and the no-fines concrete slab 10 is placed horizontally in the middle of the seepage chamber 6, dividing the seepage chamber 6 into upper and lower parts. The upper part of the seepage chamber 6 has an inlet and the lower part has an outlet. The inlet is connected to the water supply tank 1 through a water supply pipe 5, and a centrifugal pump 4 is connected in series with the water supply pipe 5. Specifically, it includes: Seepage Box 6: It adopts a vertical tower structure, with the main body made of steel plate with a thickness of 5mm. The overall dimensions are 0.5m in diameter and 3m in height, providing test space for seepage of sand-containing water and ensuring sufficient seepage path length; No-fines concrete slab 10: A supporting part placed horizontally in the middle of the seepage box 6. The slab has a diameter of 0.5m and a height of 0.2m, which is compatible with the inner diameter of the seepage box 6 to prevent water from leaking through the gap between the slab and the box wall. The no-fines concrete slab 10 is made of ordinary Portland cement with a strength grade of C32.5, uniform gravel aggregate with a particle size of 10~20mm and tap water, and has both permeability and structural strength. Filter media 11: laid on the upper surface of the sand-free concrete slab 10, used for preliminary filtration of large particles of silt in sandy water, reducing the initial clogging of the sand-free concrete slab 10, and providing more realistic seepage conditions for the experiment. Pressure detection device 7: Installed on the upper part of seepage box 6 and connected to the inside of seepage box 6, it is used to detect the inlet water head in seepage box 6 in real time and provide head data for seepage characteristic analysis; Inlet and outlet: An inlet is provided at the top of the seepage box 6, which is connected to the water supply box 1 through the water supply pipeline 5. Sand-containing water enters the seepage box 6 from the inlet. An outlet is provided at the bottom of the seepage box 6, which is connected to the drainage channel 8 of the water flow recovery system and is used to discharge the water flow filtered by the sand-free concrete slab 10.

[0025] M3, the water recycling system includes a drainage channel 8 and a drain pipe 9. The drainage channel 8 is connected to the outlet of the seepage box 6, and the drain pipe 9 is connected to the drainage channel 8. Specifically, it includes: Drainage channel 8: One end is connected to the outlet of the seepage box 6, and is used to receive the water flow after being filtered by the sand-free concrete slab 10; a right-angled triangular weir is arranged inside the drainage channel 8, and a water level measuring needle is installed on the side wall. The water head height on the right-angled triangular weir is read by the water level measuring needle, and the real-time seepage flow of the sand-free concrete slab 10 can be calculated by combining the triangular weir flow formula. Drainage pipe 9: One end is connected to the drainage ditch 8, which is used to recycle or discharge the water collected in the drainage ditch 8, so as to realize the centralized treatment of the test water flow.

[0026] The system in this embodiment, through the coordinated action of the water supply system, the testing system, and the water flow recovery system, can accurately control the concentration of sand-containing water and the influent head, and monitor the seepage flow in real time.

[0027] Example 2 The present invention proposes a method for testing seepage water sampling of a no-fines concrete slab. Based on the aforementioned no-fines concrete slab seepage water sampling test system, before the test, the no-fines concrete slab 10 is hoisted to the support portion inside the seepage box 6 and placed horizontally. Then, filter media 11 is laid on top of it. The arrangement of the no-fines concrete slab 10 inside the seepage box 6 is visible. Figure 3 After the internal arrangement of the seepage tank 6 is completed, the centrifugal pump 4 can be turned on. Sand-laden water flows into the seepage device from the top through the test water supply system, then flows through the sand-free concrete slab 10 and seeps out from its bottom. By reading the water level gauge on the drainage channel 8, the seepage flow rate of the sand-free concrete slab 10 under different working conditions can be calculated. The inlet water head under each working condition can be read through the pressure monitoring system 7. Specifically, this includes: S1. Selecting test subjects Three types of no-fines concrete slabs were selected with bulk densities of γ1=18214N / m³, γ2=20489N / m³, and γ3=23214N / m³. All three types of slabs were prepared using the same material mix ratio, which included ordinary Portland cement with a strength grade of C32.5, uniform gravel aggregate with a particle size of 10~20mm, and tap water. The bulk density of the slabs was controlled only by adjusting the amount of gravel aggregate. The purpose was to study the influence of bulk density on the seepage characteristics of sediment-laden water by comparing slabs with different bulk densities.

[0028] S2. Arrange the test apparatus The no-fines concrete slab 10 selected in step S1 is hoisted into the support part inside the seepage box 6, ensuring that the no-fines concrete slab 10 is placed horizontally. If the seepage box 6 contains filter material 11, then the filter material 11 is laid on the upper surface of the no-fines concrete slab 10. The specific operation includes: S21. Hoist the three types of no-fines concrete slabs 10 with different densities into three seepage boxes 6 of the same size. Adjust the position of the slabs using a leveling tool to ensure that each no-fines concrete slab 10 is in a horizontal state, so as to avoid uneven seepage path due to slab tilting, which would affect the accuracy of test data. S22. Filter material 11 is evenly laid on the upper surface of each no-fines concrete slab 10. The thickness of the filter material 11 is kept consistent to ensure that the initial filtration conditions of each test group are the same and to reduce the interference of the filter material 11 thickness difference on the seepage test. S23. Check the connection status of each system component: confirm that the water supply pipe 5 between the water supply tank 1 and the seepage tank 6 is connected and there is no leakage; confirm that the outlet of the seepage tank 6 is connected to the drainage channel 8 of the water recovery system normally; confirm that the pressure detection device 7 is connected to the inside of the seepage tank 6 and that the device displays normally; finally, close the valve on the water supply pipe 5 to prepare for the subsequent introduction of sand-containing water.

[0029] S3. Introduce sediment-laden water and collect basic data. Centrifugal pump 4 is turned on, and the sand-laden water, which has been mixed by the mud and sand mixing device 2 in water supply tank 1, is transported to infiltration tank 6 through water supply pipe 5. The sand-laden water flows through filter media 11 and sand-free concrete slab 10, and then flows into drainage channel 8 from the outlet of infiltration tank 6. The water level in drainage channel 8 is read by water level probe to calculate infiltration flow rate, and the inlet water head is read by pressure detection device 7. Specifically, this includes: S31. Pour tap water and sediment into water supply tank 1, turn on sediment concentration monitoring device 3, and monitor the concentration of sediment-containing water in the tank in real time. Adjust the amount of sediment to stabilize the concentration at 7.5 kg / m³. During this period, keep sediment stirring device 2 running continuously to ensure that the sediment is evenly suspended in the water and avoid sedimentation that could lead to uneven concentration. The sediment particle size distribution curve of the sediment-containing water used in the experiment is as follows: Figure 2 As shown; S32. Slowly open the valve on the water supply pipe 5 and start the centrifugal pump 4 at the same time to transport the sand-containing water with the standard concentration in the water supply tank 1 to the inlet at the top of the seepage tank 6. After the sand-containing water enters the seepage tank 6, it first flows through the filter media 11 for preliminary filtration to remove some large particles of mud and sand, then permeates through the sand-free concrete slab 10, and finally flows into the drainage channel 8 from the outlet at the bottom of the seepage tank 6. S33. After the water flow stabilizes (approximately 10 minutes), the water head height on the internal right-angled triangular weir is read using the water level probe installed on the side wall of the drainage channel 8. The initial seepage flow rate of the three types of density no-fines concrete slabs 10 is calculated using the triangular weir flow rate formula. At the same time, the inlet water head data in each seepage box is read using the pressure detection device 7 on the upper part of the seepage box 6. The initial seepage flow rate and initial inlet water head are recorded and archived as benchmark data for subsequent comparative analysis.

[0030] Seepage Flow Pattern Determination: Determining the seepage flow pattern is crucial for analyzing and evaluating the seepage characteristics of sand-laden concrete slabs under sediment-laden water flow. Before analyzing test results, it is necessary to determine and analyze the flow pattern. The seepage flow pattern is primarily analyzed at the microscopic level, that is, by using discriminant equations to determine whether the seepage flow pattern under different operating conditions conforms to laminar, turbulent, or transitional flow.

[0031] seepage flow The calculation formula is:

[0032] in, The seepage coefficient ( , For seepage area, Permeability coefficient, (where the seepage path length is...) The permeability index ( (where m is the flow index). When When the seepage flow is in a state of complete turbulence; when At this time, the seepage flow regime is a transitional flow from laminar to turbulent; when At that time, the seepage flow pattern is laminar.

[0033] Seepage flow rate of sand-laden water under sand-free concrete slab 10 With the water inlet head Changes such as Figure 4 As shown, and also based on the seepage flow rate The calculation formula was fitted to this change, and the fitting results are shown in Table 1: Table 1. Fitting relationship between seepage flow rate and inlet head of sand-laden water flowing through a sand-containing concrete slab.

[0034] See Figure 4 As shown, with the gradual increase of the influent head, the seepage flow of the no-fines concrete slab 10 with different densities increases significantly. According to the hydraulic formula:

[0035] in, For hydraulic gradient, Due to head difference, Let be the seepage path length. When the seepage path length remains constant, the hydraulic gradient increases with the increase of the influent head. Furthermore, since the seepage velocity is positively correlated with the hydraulic gradient, according to the formula:

[0036] in, The seepage velocity, Since γ is the permeability coefficient, the seepage velocity also increases, and the seepage flow rate increases accordingly. It can also be seen that as the influent head increases, the seepage flow rate of the no-fines concrete slab 10 with different densities increases at different rates. Specifically, the increase in density γ1 is greater than that of density γ2, and the increase in density γ2 is greater than that of γ3. This indicates that as the influent head increases, the no-fines concrete slab 10 with a smaller density experiences a greater increase in seepage flow rate.

[0037] As shown in Table 1 above, in this sediment-laden flow test, the seepage flow rate was... The seepage coefficient obtained by fitting the calculation formula with the change of influent head The value ranges from 0.0009 to 0.00304, indicating a permeability index. The value ranges from 0.5 to 0.9. Based on the analysis above, it can be concluded that when sediment-laden water flows through no-fines concrete slabs 10 with different unit densities, the seepage flow pattern is always transitional. The higher the unit density of the no-fines concrete slab 10, the greater its seepage coefficient. The smaller the permeability index The closer the value is to 1, the greater the density of the sand-laden concrete slab 10, the smaller the seepage coefficient, the larger the seepage index, and the closer the corresponding seepage flow state is to laminar flow when the sand-laden water flows through the sand-free concrete slab 10.

[0038] S4. Long-term seepage observation The sand-laden water was continuously introduced into the seepage chamber 6 for a total duration of 48 hours. Step S3 was repeated at five time points: 6 hours, 12 hours, 24 hours, 36 hours, and 48 hours after the sand-laden water was introduced. The seepage flow rate and corresponding influent head data of the three types of sand-laden concrete slabs 10 were collected at each time point. By comparing the changes in seepage flow rate at different time points, the change law of seepage capacity of sand-laden concrete slabs 10 under the long-term action of sand-laden water flow was observed.

[0039] Analysis of long-term seepage observation results: Prolonged flow of sediment-laden water gradually reduces the seepage rate of the sand-free concrete slab 10. To investigate the effect of flow time on the seepage rate of the sand-laden concrete slab 10 under sediment-laden water flow, sand-free concrete slabs 10 with densities γ1, γ2, and γ3 were used as the research object. The influent head was set to 7m, and the three sand-free concrete slabs 10 were flowed with water for 48 hours respectively. The seepage rate of the sand-free concrete slabs 10 at different time periods was measured. The relationship curve between the seepage rate and flow time of the sand-free concrete slab 10 is shown below. Figure 5 As shown in the figure, and based on the relative changing trends of the two, the final selection is... The formula in the form of a time-flow-time functional relationship of the seepage flow rate is fitted, as shown in Table 2: Table 2. Fitting equations for seepage flow rate and flow time

[0040] See Figure 5 As shown, when the bulk density of the no-fines concrete slab 10 is γ1, γ2, and γ3, the reduction in seepage flow of the horizontally arranged no-fines concrete slab 10 within 48 hours after the introduction of sand-laden water is 0.0026 m³ / s, 0.0021 m³ / s, and 0.0007 m³ / s, respectively. This indicates that as the bulk density increases, the reduction in seepage flow of the no-fines concrete slab 10 under sand-laden water flow decreases. Furthermore, over time, the seepage curve of the no-fines concrete slab 10 tends to flatten, and the reduction in seepage flow also decreases slowly. This is because under sand-laden water flow, as the flow time increases, the effective permeable pores inside the no-fines concrete slab 10 will gradually be blocked by sediment. However, when the blockage reaches a certain level, the internal permeable pore structure will remain relatively stable. At this point, the change in seepage flow decreases with increasing flow time.

[0041] As can be seen from the table above, the seepage capacity of the no-fines concrete slab 10 decreases with the increase of the flow time of sand-containing water. The fitting formula for seepage flow rate versus flow time is a monotonically decreasing exponential function, i.e., Q=ae. -b A formal expression can better describe this relationship. The values ​​of 'a' obtained by fitting the formula for calculating the seepage flow rate as a function of flow time range from 0.0017 to 0.005, and the values ​​of 'b' range from -0.03 to -0.01. For no-fines concrete slabs with higher unit density, the values ​​of 'a' and 'b' are smaller, and the change in seepage flow rate with increasing flow time is relatively smaller.

[0042] S5, Stasis Recovery Capability Test Three types of no-fines concrete slabs 10 that had become clogged after the test in step S4 were removed. After being treated with different dredging methods, they were reinstalled in their corresponding seepage boxes 6 and filled with clean water. Seepage flow data were collected after dredging, and the effects of different dredging methods on the clogging recovery ability of the no-fines concrete slabs 10 were compared and analyzed. Specifically, this included: S51. During the test, the sand-free concrete slab 10 was continuously silted up to varying degrees after 48 hours of sand-containing water flow, and its flow capacity was continuously reduced. Therefore, when sand-free concrete slab 10 is selected as a seepage water intake component under sand-containing water flow, the accumulated mud and sand should be cleaned regularly.

[0043] Specifically, after the 48-hour long-term seepage test, the valves on the centrifugal pump 4 and the water supply pipe 5 were closed. The silted-up no-fines concrete slabs 10 were removed from the three seepage tanks 6, and the residual filter material 11 on the surface of the slabs was removed. Then, three different sludge removal methods were used to treat them respectively: Method 1: After manually removing the surface mud and sand from the board, slowly rinse the upper surface of the board with clean water until the rinse water is clear; Method 2: After manually removing the surface mud and sand from the board, backwashing is used to flush the board from the bottom surface upwards. The backwash water pressure is controlled at 0.2 MPa. Method 3: After manually removing the surface mud and sand from the board, rinse the upper surface of the board with a high-pressure water gun, keeping the rinsing direction perpendicular to the board. S52. The sand-free concrete slab 10, which has been treated by the three dredging methods, is re-hoisted to the internal support of the corresponding seepage box 6. The slab is adjusted to be level according to the requirements of step S2, and the filter material 11 is re-laid. At the same time, the connection status of each system component is checked. S53. Inject clean water (excluding silt) into the water supply tank 1, open the valves on the centrifugal pump 4 and the water delivery pipe 5, and deliver the clean water to the seepage tank 6; after the water flow stabilizes, read the seepage flow rate and corresponding inlet head data of each plate after dredging through the water level probe and pressure detection device 7 of the drainage channel 8. S54. Calculate the seepage recovery rate: Seepage recovery rate n = (seepage flow after dredging / clear water seepage flow before siltation) × 100% Wherein, clear water seepage flow before siltation is the initial seepage flow of each no-fines concrete slab 10 when clear water is introduced into the seepage box 6 alone before the start of the test; the larger the value of seepage recovery rate n, the stronger the siltation recovery ability of the no-fines concrete slab 10. S55. Compare the seepage recovery rate data under three dredging methods; see reference. Figures 6-8 The recovery rate corresponding to different density plates and different inlet water heads was used to derive the pattern of dredging effect: Under the same influent head, the seepage recovery rate of the no-fines concrete slab 10 with a bulk density of γ1 is less than that of the no-fines concrete slab 10 with a bulk density of γ2 and less than that of the no-fines concrete slab 10 with a bulk density of γ3. This is because the no-fines concrete slab 10 with a larger bulk density has a relatively smaller porosity, and therefore less silt and sand are trapped in the pores. When using the same method to clean the no-fines concrete slab 10 with different bulk densities, the no-fines concrete slab 10 with a smaller porosity is easier to clean completely, while the no-fines concrete slab 10 with a larger porosity is more severely blocked by silt and sand, and the water flow is difficult to disperse the silt and sand, making it difficult to clean completely. It can also be seen that when method 3 is used, that is, when the surface mud and sand are removed manually and then flushed with a high-pressure water gun, the seepage recovery rate of the no-fines concrete slab 10 with different densities is the highest. The seepage recovery rate of the no-fines concrete slab 10 with a density of γ3 reached 82.4% under the maximum inlet water head in this test, which is 15.6% and 10.6% higher than that of method 1 and method 2, respectively. For the same density of no-fines concrete slab 10, under different dredging methods, its siltation recovery ability increases with the increase of the inlet water head. Three different dredging methods can enable the seepage recovery rate of sand-free concrete slabs 10 with different densities to reach more than 55% under each water head. Therefore, in the seepage water intake project of sand-containing water flow, the sand-free concrete slabs 10 should be dredged regularly to restore their flow capacity in a timely manner.

[0044] In summary, this invention provides a seepage sampling test system and method for sand-free concrete slabs. This device and method can effectively address the study of seepage characteristics of sand-containing water flow on sand-free concrete slabs, providing a research method combining model experiments and theoretical analysis for exploring the seepage characteristics and siltation recovery capacity of sand-containing concrete slabs under sand-containing water flow.

[0045] The above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A seepage sampling test system for no-fines concrete slabs, characterized in that, include: Water supply system, testing system and water recycling system; The water supply system includes a water supply tank, a centrifugal pump, and a water supply pipeline. The water supply tank is equipped with a sediment mixing device and a sediment concentration monitoring device. The test system includes a seepage box and a sand-free concrete slab. The seepage box is a vertical tower structure. The sand-free concrete slab is placed horizontally in the middle of the seepage box and divides the seepage box into upper and lower parts. The upper part of the seepage box is provided with an inlet and the lower part with an outlet. The inlet is connected to the water supply box through a water supply pipe. The centrifugal pump is connected in series with the water supply pipe. The water recycling system includes a drainage channel and a drain pipe. The drainage channel is connected to the outlet of the seepage box, and the drain pipe is connected to the drainage channel.

2. The seepage water sampling test system for no-fines concrete slabs according to claim 1, characterized in that, The drainage channel is equipped with a right-angled triangular weir. The seepage flow of the sand-free concrete slab can be calculated by measuring the water head on the weir. The drainage channel is also equipped with a water level gauge for reading the water level.

3. The seepage water sampling test system for no-fines concrete slabs according to claim 1, characterized in that, The main body of the seepage box is made of steel plate with a thickness of 5mm. The dimensions of the seepage box are 0.5m in diameter and 3m in height. The dimensions of the no-fines concrete slab are 0.5m in diameter and 0.2m in height, which are adapted to the inner diameter of the seepage box.

4. The seepage water sampling test system for no-fines concrete slabs according to claim 1, characterized in that, The no-fines concrete slab is made by mixing ordinary Portland cement with a strength grade of C32.5, uniform gravel aggregate with a particle size of 10~20mm, and tap water.

5. The seepage water sampling test system for no-fines concrete slabs according to claim 1, characterized in that, The test system also includes filter media and a pressure testing device. The filter media is laid on the upper surface of the sand-free concrete slab, and the pressure testing device is installed on the upper part of the seepage box to detect the inlet water head.

6. The seepage water sampling test system for no-fines concrete slabs according to claim 1, characterized in that, The water supply system also includes valves, which are installed on the water supply pipes.

7. A method for testing seepage water in a no-fines concrete slab, characterized in that, include: S1. Selecting test subjects: Select subjects with bulk densities of... Three types of sand-free concrete slabs; S2. Set up the test device: hoist the no-fines concrete slab selected in step S1 to the support part inside the seepage box, ensuring that the no-fines concrete slab is placed horizontally. If the seepage box contains filter material, lay the filter material on the surface of the no-fines concrete slab. S3. Introduce sand-laden water and collect basic data: Turn on the centrifugal pump and transport the sand-laden water, which has been mixed by the mud and sand mixing device in the water supply tank, to the infiltration tank through the water supply pipeline. The sand-laden water flows through the filter media and the sand-free concrete slab and then flows into the drainage ditch from the outlet of the infiltration tank. The water level in the drainage ditch is read by the water level probe to calculate the seepage flow rate, and the inlet water head is read by the pressure detection device. S4. Long-term seepage observation: Keep the sand-containing water continuously flowing into the seepage box for 48 hours. Repeat step S3 at 6 hours, 12 hours, 24 hours, 36 hours and 48 hours after the sand-containing water is introduced to collect the seepage flow rate and influent head at each time point and observe the changes in seepage capacity. S5. Siltation recovery capacity test: Remove the silted no-fines concrete slab after the test in step S4, treat it with different sludge removal methods, reinstall it in the seepage box and introduce clean water, collect the seepage flow data after sludge removal, and compare and analyze the siltation recovery capacity.

8. The method for testing seepage water in no-fines concrete slabs according to claim 1, characterized in that, In step S3, the sediment concentration of the sand-containing water is 7.5 kg / m³, and the water is introduced into the seepage box only after the sediment concentration monitoring device in the water supply tank confirms that the concentration meets the standard.

9. The method for testing seepage water in no-fines concrete slabs according to claim 1, characterized in that, In step S5, the different dredging methods include: manually removing surface mud and sand followed by rinsing with clean water, manually removing surface mud and sand followed by backwashing, and manually removing surface mud and sand followed by high-pressure water gun rinsing.

10. The method for testing seepage water in no-fines concrete slabs according to claim 1, characterized in that, In step S5, the siltation recovery capacity is quantitatively evaluated by the seepage recovery rate, which is the percentage of the seepage flow after siltation to the clear water seepage flow before siltation.

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