On-site lossless evaluation method for compressive strength of release structure concrete after washing and grinding

Abstract

The invention discloses an on-site nondestructive evaluation method for compressive strength of release structure concrete after impact grinding, and the method comprises the following specific steps: step 1, preparing a concrete test block, obtaining a surface model of the concrete test block, and carrying out meshing on the surface model to obtain a first meshing model; 2, the concrete test block is installed in a punching and grinding device to be subjected to a punching and grinding test, a springback test is conducted on the punching and grinding face of the concrete test block after punching and grinding, and a punching and grinding depth-springback value curve is constructed; step 3, reconstructing a punching and grinding depth-rebound value curve as a punching and grinding depth-compressive strength curve; and 4, carrying out in-situ test in the floodway, and combining with the punching and grinding depth-compressive strength curve to obtain the final compressive strength. The method provided by the invention can detect the compressive strength of the water release structure after the concrete is washed and abraded under the condition of no damage.

Description

Technical Field

[0001] This invention belongs to the technical field of non-destructive evaluation methods for hydraulic concrete, specifically relating to a non-destructive evaluation method for the compressive strength of concrete after impact grinding in spillway structures. Background Technology

[0002] High-speed, sand-laden water flows can cause severe erosion damage to hydraulic concrete spillway structures. While studying this damage, researchers have also noted the impact of erosion on other mechanical properties of the spillway structures, particularly the compressive strength of the concrete. Furthermore, non-destructive testing methods for evaluating the compressive strength after erosion in spillways are scarce and immature. Traditional methods often involve core drilling, which can cause irreversible damage to the spillway structures. Therefore, a non-destructive testing method is needed to perform real-time, non-destructive, and intuitive testing of spillways. Summary of the Invention

[0003] The purpose of this invention is to provide a non-destructive evaluation method for the compressive strength of concrete after impact grinding in drainage structures, thereby solving the problem that existing testing methods can cause irreversible damage to drainage structures.

[0004] The technical solution adopted in this invention is a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after scouring and polishing. The specific steps are as follows: Step 1: Prepare concrete test blocks. Use a handheld 3D scanner to scan and obtain the surface model of the concrete test blocks, and then mesh the surface model to obtain the first meshed model. Step 2: Install the concrete test block in the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete test block after grinding to construct the grinding depth-rebound value curve. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

[0005] The invention is further characterized by: In step 1, the concrete test block is a cube with a size of 50cm×50cm×50cm; the concrete test block is marked with graduations along its height.

[0006] In step 2, the grinding device includes a tank with an open top and a conical bottom. Four electrically operated telescopic rods are evenly spaced along the circumference of the inner wall of the tank. The fixed end of each electric telescopic rod is connected to the inner wall of the tank. A mixing chamber is located on the inner wall of the tank, containing a mixing rod connected to the output shaft of a motor. The motor is connected to the outer wall of the tank. A circulation chamber is located on the inner wall of the tank, directly below the mixing chamber. A first solenoid valve is located at the outlet of the mixing chamber. Several jet nozzles are located at the bottom of the circulation chamber, above the electric telescopic rods. One end of a circulation pipe is connected to the bottom of the tank, and the other end of the circulation pipe is connected to the side wall of the circulation chamber. A sand storage tank and a water storage tank are located directly above the mixing chamber. A second solenoid valve is located at the outlet of the sand storage tank, and a third solenoid valve is located at the outlet of the water storage tank.

[0007] The specific process of step 2 is as follows: Step 2.1: Place the concrete test block between the four electric telescopic rods and extend the electric telescopic rods to clamp and fix the concrete test block. Open the second and third solenoid valves to add sand from the sand storage tank and water from the water storage tank into the mixing chamber for mixing to obtain a sand-water mixture. Open the first solenoid valve and input the sand-water mixture into the circulation chamber. The sand-water mixture is then sprayed onto the upper surface of the concrete test block through the jet nozzle for grinding for a set time. The ground sand-water mixture then flows through the circulation pipe into the circulation chamber for reuse.

[0008] Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a grinding depth-springback value curve with the average grinding depth as the x-axis and the final experimental springback value as the y-axis.

[0009] In step 2.2, the five points are set at the center of the polished surface of the concrete test block and at the four corners of the flat position.

[0010] The specific process of step 3 is as follows: Step 3.1: After the last impact grinding and rebound test, cut out several small cube concrete blocks of equal size from the impact grinding surface of the concrete block after the rebound test. Divide the small cube concrete blocks into several groups for compressive strength test and obtain several groups of compressive strength data. Remove one outlier from the compressive strength data obtained from each group and retain the remaining data. Calculate the average value of all the retained compressive strengths in several groups as the compressive strength after impact grinding. Step 3.2: Prepare a small test block using the same raw materials and process as the concrete test block in Step 1. The size of the small test block is the same as that of the small cube concrete test block obtained in Step 3.1. Perform rebound test and compressive strength test on the small test block to obtain the rebound value and compressive strength. Step 3.3: Locate the results of the last grinding and springback test on the grinding depth-springback curve. Mark the vertical axis position corresponding to the found point as the compressive strength after grinding. Based on the compressive strength and springback value after grinding at this point and the compressive strength and springback value obtained in step 3.2, construct a functional relationship between compressive strength and springback value. According to the functional relationship, modify all springback values ​​on the grinding depth-springback curve to the compressive strength after grinding, and modify the vertical axis to compressive strength while keeping the horizontal axis unchanged to obtain the grinding depth-compressive strength curve. The expression for the functional relationship is: (1) In the formula, R represents the compressive strength after grinding, in MPa. m This is the rebound value; The specific process of step 4 is as follows: Step 4.1: During the pouring of the spillway of the spillway structure, several ultrasonic sensor units are pre-embedded at equal intervals along the length of the spillway to monitor the thickness of the concrete layer of the spillway. The average value of the concrete layer thickness monitored by each ultrasonic sensor unit is calculated to obtain the average concrete layer thickness. The thickness of the concrete layer of the spillway that has just been poured but not yet put into use is taken as the initial thickness. The difference between the initial thickness and the average concrete layer thickness is used to obtain the scouring depth of the spillway. Each ultrasonic sensor unit includes four sets of ultrasonic sensors, which are pre-embedded on the top, two sides and bottom of the flood discharge channel. Step 4.2: Substitute the scouring depth of the spillway obtained in Step 4.1 into the scouring depth-compressive strength curve to obtain the compressive strength of the spillway at the scouring depth. Step 4.3: Select 5 points on the concrete surface of the spillway corresponding to each group of ultrasonic sensors and use a rebound hammer to conduct rebound tests to obtain the field rebound value of each point. Calculate the average of the field rebound values ​​of the 5 points as the final field rebound value. Calculate a correction coefficient by comparing the final field rebound value with the final experimental rebound value obtained in step 2.2. Use the correction coefficient to correct the compressive strength of the spillway obtained in step 4.2 to obtain the final compressive strength.

[0011] In step 4.1, each set of ultrasonic sensors is buried at a depth of not less than 4.5 mm from the surface concrete, and the center points of the four sets of ultrasonic sensors are located on the same plane, which is perpendicular to the water flow direction. This plane serves as the sensor monitoring surface.

[0012] In step 4.1, each group of ultrasonic sensors includes 9 ultrasonic sensors arranged in a 3×3 matrix, with the ultrasonic sensor at the center located on the sensor monitoring surface. The distance between two adjacent ultrasonic sensors in each row and between two adjacent ultrasonic sensors in each column is 10cm.

[0013] In step 4.3, the expression for the correction coefficient is: (2) In the formula, This is the final on-site rebound value. This is the final experimental rebound value; k >1 indicates that the concrete strength of the spillway is higher than that of the concrete test block; k <1 indicates that the concrete strength of the spillway is lower than that of the concrete test block; The expression for the final compressive strength is: (3) In the formula, For the compressive strength of the flood discharge channel, This represents the final compressive strength.

[0014] The beneficial effects of this invention are: the present invention provides a non-destructive evaluation method for the compressive strength of concrete after scouring of a drainage structure. It constructs a mathematical formula to derive the compressive strength of the drainage structure wall after scouring through the scouring depth, and then corrects the compressive strength through in-situ rebound tests, thus realizing non-destructive testing. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the grinding device in the method of the present invention; Figure 2 This is a curve showing the springback value versus the grinding depth in the method of this invention. Figure 3 This is a curve showing the compressive strength versus grinding depth in the method of this invention. Figure 4This is a schematic diagram showing the layout of each ultrasonic sensor unit in the method of the present invention; Figure 5 This is a schematic diagram of the ultrasonic sensor installation in the method of the present invention; Figure 6 This is a schematic diagram showing the layout of each group of ultrasonic sensors in the method of the present invention.

[0016] In the diagram, 1. Water storage tank, 2. Sand storage tank, 3. Electric telescopic rod, 4. Circulation pipe, 5. Jet nozzle, 6. Circulation chamber, 7. Mixing chamber, 8. Tank body, 9. Concrete test block, 10. First solenoid valve, 11. Second solenoid valve, 12. Third solenoid valve, 13. Mixing rod, 14. Motor, 15. Ultrasonic sensor. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 The present invention provides a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after impact and grinding. The specific steps are as follows: Step 1: Prepare concrete specimen 9. Obtain the surface model of concrete specimen 9 by scanning with a handheld 3D scanner, and mesh the surface model to obtain the first mesh model. Concrete test block 9 is a cube, with a size of 50cm×50cm×50cm; The concrete test block 9 has markings along its height, with a spacing of 1 cm between two adjacent markings. Step 2: Install concrete specimen 9 into the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete specimen after grinding to construct the grinding depth-rebound value curve. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

[0019] Example 2 The present invention provides a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after impact and grinding. The specific steps are as follows: Step 1: Prepare concrete specimen 9. Obtain the surface model of concrete specimen 9 by scanning with a handheld 3D scanner, and mesh the surface model to obtain the first mesh model. Concrete test block 9 is a cube, with a size of 50cm×50cm×50cm; The concrete test block 9 has markings along its height, with a spacing of 1 cm between two adjacent markings. Step 2: Install concrete specimen 9 into the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete specimen after grinding to construct the grinding depth-rebound value curve. like Figure 1 As shown, the grinding device includes a tank 8 with an open top and a conical bottom. Four electrically operated telescopic rods 3 are evenly spaced along the circumference of the inner wall of the tank 8. The fixed end of each electric telescopic rod 3 is connected to the inner wall of the tank 8. Each telescopic rod 3 has a rubber head at its telescopic end to increase friction. A stirring chamber 7 is located on the inner wall of the tank 8. A circulation chamber 6 is located on the inner wall of the tank 8 and directly below the stirring chamber 7. A first solenoid valve 10 is located at the outlet of the stirring chamber 7. The stirring chamber 7 and the circulation chamber 6 are connected. Several jet nozzles 5 are located at the bottom of the circulation chamber 6, and the circulation chamber 6 is connected to each jet nozzle 5. The several jet nozzles 5 are located at... Above the electric telescopic rod 3, several jet nozzles 5 are arranged in a straight line and are equidistant from the top edge of the concrete test block 9 to ensure that all positions on the upper surface of the concrete test block 9 are polished. The bottom of the tank body 8 is connected to one end of the circulation pipe 4, and the other end of the circulation pipe 4 is connected to the side wall of the circulation chamber 6. A sand storage box 2 and a water storage box 1 are arranged directly above the mixing chamber 7. A second solenoid valve 11 is arranged at the outlet of the sand storage box 2, and a third solenoid valve 12 is arranged at the outlet of the water storage box 1. The sand storage box 2 is filled with sand, and the water storage box 1 is filled with water. A stirring rod 13 is arranged inside the mixing chamber 7. The stirring rod 13 is connected to the output shaft of the motor 14, and the motor 14 is connected to the outer wall of the tank body 8. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

[0020] Example 3 Based on Example 2, the specific process of step 2 is as follows: Step 2.1: Place the concrete test block 9 between the four electric telescopic rods 3 and extend the electric telescopic rods 3 to clamp and fix the concrete test block 9. Open the second solenoid valve 14 and the third solenoid valve 15 to add sand from the sand storage tank 2 and water from the water storage tank 1 to the mixing chamber 7 for mixing to obtain a sand-water mixture. Open the first solenoid valve 10 and input the sand-water mixture into the circulation chamber 6. The sand-water mixture is then sprayed onto the upper surface of the concrete test block 9 through the jet nozzle 5 for grinding for a set time. The ground sand-water mixture then flows through the circulation pipe 4 into the circulation chamber 6 for reuse.

[0021] Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Five points were set at the center of the polished surface of the concrete test block and at the four corners of the flat surface. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a graph with the average grinding depth as the x-axis and the final experimental springback value as the y-axis, as shown below. Figure 2 The grinding depth-springback curve is shown.

[0022] Example 4 The present invention provides a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after impact and grinding. The specific steps are as follows: Step 1: Prepare concrete specimen 9. Obtain the surface model of concrete specimen 9 by scanning with a handheld 3D scanner, and mesh the surface model to obtain the first mesh model. Concrete test block 9 is a cube, with a size of 50cm×50cm×50cm; The concrete test block 9 has markings along its height, with a spacing of 1 cm between two adjacent markings. Step 2: Install concrete specimen 9 into the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete specimen after grinding to construct the grinding depth-rebound value curve. The grinding device includes a tank 8 with an open top and a conical bottom. Four electrically operated telescopic rods 3 are evenly spaced along the circumference of the inner wall of the tank 8. The fixed end of each electric telescopic rod 3 is connected to the inner wall of the tank 8. Each telescopic rod 3 has a rubber head at its telescopic end to increase friction. A stirring chamber 7 is located on the inner wall of the tank 8. A circulation chamber 6 is located on the inner wall of the tank 8 and directly below the stirring chamber 7. A first solenoid valve 10 is located at the outlet of the stirring chamber 7. The stirring chamber 7 and the circulation chamber 6 are connected. Several jet nozzles 5 are located at the bottom of the circulation chamber 6, and the circulation chamber 6 is connected to each jet nozzle 5. The jet nozzles 5 are located at the electric... Above the telescopic rod 3, several jet nozzles 5 are arranged in a straight line and are equidistant from the top edge of the concrete test block 9 to ensure that all positions on the upper surface of the concrete test block 9 are polished. The bottom of the tank body 8 is connected to one end of the circulation pipe 4, and the other end of the circulation pipe 4 is connected to the side wall of the circulation chamber 6. A sand storage box 2 and a water storage box 1 are arranged directly above the mixing chamber 7. A second solenoid valve 11 is arranged at the outlet of the sand storage box 2, and a third solenoid valve 12 is arranged at the outlet of the water storage box 1. The sand storage box 2 is filled with sand, and the water storage box 1 is filled with water. A stirring rod 13 is arranged inside the mixing chamber 7. The stirring rod 13 is connected to the output shaft of the motor 14, and the motor 14 is connected to the outer wall of the tank body 8. Step 2 is as follows: Step 2.1: Place the concrete test block 9 between the four electric telescopic rods 3 and extend the electric telescopic rods 3 to clamp and fix the concrete test block 9. Open the second solenoid valve 14 and the third solenoid valve 15 to add sand from the sand storage tank 2 and water from the water storage tank 1 to the mixing chamber 7 for mixing to obtain a sand-water mixture. Open the first solenoid valve 10 and input the sand-water mixture into the circulation chamber 6. The sand-water mixture is then sprayed onto the upper surface of the concrete test block 9 through the jet nozzle 5 for grinding for a set time. The ground sand-water mixture then flows through the circulation pipe 4 into the circulation chamber 6 for reuse.

[0023] Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Five points were set at the center of the polished surface of the concrete test block and at the four corners of the flat surface. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a grinding depth-springback value curve with the average grinding depth as the x-axis and the final experimental springback value as the y-axis. Step 3, reconstruct the grinding depth-springback curve as follows: Figure 3 The grinding depth-compressive strength curve shown; Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

[0024] Example 5 The present invention provides a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after impact and grinding. The specific steps are as follows: Step 1: Prepare concrete specimen 9. Obtain the surface model of concrete specimen 9 by scanning with a handheld 3D scanner, and mesh the surface model to obtain the first mesh model. Concrete test block 9 is a cube, with a size of 50cm×50cm×50cm; The concrete test block 9 has markings along its height, with a spacing of 1 cm between two adjacent markings. Step 2: Install concrete specimen 9 into the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete specimen after grinding to construct the grinding depth-rebound value curve. The grinding device includes a tank 8 with an open top and a conical bottom. Four electrically operated telescopic rods 3 are evenly spaced along the circumference of the inner wall of the tank 8. The fixed end of each electric telescopic rod 3 is connected to the inner wall of the tank 8. Each telescopic rod 3 has a rubber head at its telescopic end to increase friction. A stirring chamber 7 is located on the inner wall of the tank 8. A circulation chamber 6 is located on the inner wall of the tank 8 and directly below the stirring chamber 7. A first solenoid valve 10 is located at the outlet of the stirring chamber 7. The stirring chamber 7 and the circulation chamber 6 are connected. Several jet nozzles 5 are located at the bottom of the circulation chamber 6, and the circulation chamber 6 is connected to each jet nozzle 5. The jet nozzles 5 are located at the electric... Above the telescopic rod 3, several jet nozzles 5 are arranged in a straight line and are equidistant from the top edge of the concrete test block 9 to ensure that all positions on the upper surface of the concrete test block 9 are polished. The bottom of the tank body 8 is connected to one end of the circulation pipe 4, and the other end of the circulation pipe 4 is connected to the side wall of the circulation chamber 6. A sand storage box 2 and a water storage box 1 are arranged directly above the mixing chamber 7. A second solenoid valve 11 is arranged at the outlet of the sand storage box 2, and a third solenoid valve 12 is arranged at the outlet of the water storage box 1. The sand storage box 2 is filled with sand, and the water storage box 1 is filled with water. A stirring rod 13 is arranged inside the mixing chamber 7. The stirring rod 13 is connected to the output shaft of the motor 14, and the motor 14 is connected to the outer wall of the tank body 8. Step 2 is as follows: Step 2.1: Place the concrete test block 9 between the four electric telescopic rods 3 and extend the electric telescopic rods 3 to clamp and fix the concrete test block 9. Open the second solenoid valve 14 and the third solenoid valve 15 to add sand from the sand storage tank 2 and water from the water storage tank 1 to the mixing chamber 7 for mixing to obtain a sand-water mixture. Open the first solenoid valve 10 and input the sand-water mixture into the circulation chamber 6. The sand-water mixture is then sprayed onto the upper surface of the concrete test block 9 through the jet nozzle 5 for grinding for a set time. The ground sand-water mixture then flows through the circulation pipe 4 into the circulation chamber 6 for reuse.

[0025] Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Five points were set at the center of the polished surface of the concrete test block and at the four corners of the flat surface. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a grinding depth-springback value curve with the average grinding depth as the x-axis and the final experimental springback value as the y-axis. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; The specific process is as follows: Step 3.1: After the last impact grinding and rebound test, cut out several small cube concrete blocks of equal size from the impact grinding surface of the concrete block after the rebound test. Divide the small cube concrete blocks into several groups and conduct compressive strength tests to obtain several groups of compressive strength data. Remove one outlier from the compressive strength data obtained from each group and retain the remaining data. Calculate the average value of all the retained compressive strengths from several groups as the compressive strength after impact grinding. Step 3.2: Prepare a small test block using the same raw materials and process as the concrete test block (9) in Step 1. The size of the small test block is the same as that of the small cube concrete test block obtained in Step 3.1. Perform rebound test and compressive strength test on the small test block to obtain the rebound value and compressive strength. Step 3.3: Locate the results of the last grinding and springback test on the grinding depth-springback curve. Mark the vertical axis position corresponding to the found point as the compressive strength after grinding. Based on the compressive strength and springback value after grinding at this point and the compressive strength and springback value obtained in step 3.2, construct a functional relationship between compressive strength and springback value. According to the functional relationship, modify all springback values ​​on the grinding depth-springback curve to the compressive strength after grinding, and modify the vertical axis to compressive strength while keeping the horizontal axis unchanged to obtain the grinding depth-compressive strength curve. Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

[0026] Example 6 The present invention provides a non-destructive on-site evaluation method for the compressive strength of concrete in spillway structures after impact and grinding. The specific steps are as follows: Step 1: Prepare concrete specimen 9. The concrete specimen 9 has scales engraved on it along its height direction. The distance between two adjacent scales is 1 cm and the depth of the scale is 2 mm. The scales are used to identify the height of the concrete specimen 9. Use a handheld 3D scanner to scan the concrete specimen 9 to obtain the surface model of the concrete specimen 9. Then, use the ScanViewer software built into the handheld 3D scanner to mesh the 3D scan model to obtain the first meshed model. Concrete test block 9 is a cube, with a size of 50cm×50cm×50cm; The concrete test block 9 has markings along its height, with a spacing of 1 cm between two adjacent markings and a depth of 2 mm. The markings are used to identify the height of the concrete test block 9. The method for preparing concrete test blocks is as follows: a 50cm×50cm×50cm mold is built using wooden templates, hydraulic concrete is poured into the mold, an electric vibrator is used for vibration during the pouring process, and curing is carried out after pouring to obtain concrete test blocks. The specific raw materials for preparing concrete test blocks are as follows: The cement was purchased from Jidong Haitian Cement Wenxi Co., Ltd., P.042.5, density 3.10 g / cm³. 3 Specific surface area 337m² 2 / kg, 28-day flexural strength 8.0MPa, compressive strength 44.7MPa; The fine aggregate was purchased from Nantian Sand and Gravel Co., Ltd., and was river sand with a fineness modulus of 2.7. The coarse aggregate was purchased from Zhengjia Building Materials Co., Ltd., consisting of crushed stone ranging from 5mm to 31.5mm, with a ratio of 5mm to 10mm: 10mm to 20mm: 16mm to 31.5mm = 2:5:3. The proportions of each raw material are shown in Table 1. This is used to prepare C25 concrete. Table 1 Mixing ratio

[0027] Step 2: Install concrete specimen 9 into the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete specimen after grinding to construct the grinding depth-rebound value curve. The grinding device includes a tank 8 with an open top and a conical bottom. Four electrically operated telescopic rods 3 are evenly spaced along the circumference of the inner wall of the tank 8. The fixed end of each electric telescopic rod 3 is connected to the inner wall of the tank 8. Each telescopic end of the electric telescopic rod 3 is equipped with a rubber head to increase friction. A stirring chamber 7 is located on the inner wall of the tank 8, and a stirring rod 13 is installed inside the stirring chamber 7. The stirring rod 13 is connected to the output shaft of a motor 14, which is connected to the outer wall of the tank 8. A circulation chamber 6 is located on the inner wall of the tank 8, directly below the stirring chamber 7. A first solenoid valve 10 is installed at the outlet of the stirring chamber 7. The stirring chamber 7 and the circulation chamber 6 are connected... The bottom of the circulation chamber 6 is equipped with several jet nozzles 5, and the circulation chamber 6 is connected to each jet nozzle 5. The jet nozzles 5 are located above the electric telescopic rod 3. The jet nozzles 5 are arranged in a straight line and are equidistant from the top edge of the concrete test block 9 to ensure that all positions on the upper surface of the concrete test block 9 are polished. The bottom of the tank body 8 is connected to one end of the circulation pipe 4, and the other end of the circulation pipe 4 is connected to the side wall of the circulation chamber 6. A sand storage tank 2 and a water storage tank 1 are set directly above the mixing chamber 7. A second solenoid valve 11 is set at the outlet of the sand storage tank 2, and a third solenoid valve 12 is set at the outlet of the water storage tank 1. The sand storage tank 2 is filled with sand, and the water storage tank 1 is filled with water. The process of obtaining sand in sand storage tank 2 is as follows: a water pump is installed in the flood discharge channel to extract in-situ water samples, and the extracted water samples are evaporated to obtain sand, so as to approximate the actual grinding effect. Step 2 is as follows: Step 2.1: Place the concrete test block 9 between the four electric telescopic rods 3 and extend the electric telescopic rods 3 to clamp and fix the concrete test block 9. Open the second solenoid valve 14 and the third solenoid valve 15 to add sand from the sand storage tank 2 and water from the water storage tank 1 to the mixing chamber 7 for mixing to obtain a sand-water mixture. Open the first solenoid valve 10 and input the sand-water mixture into the circulation chamber 6. The sand-water mixture is then sprayed onto the upper surface of the concrete test block 9 through the jet nozzle 5 at a speed of 40 m / s for grinding until the set time is reached. The grinding end time is 72 h. The ground sand-water mixture then flows through the circulation pipe 4 into the circulation chamber 6 for reuse.

[0028] The grinding time is increased in increments of 12 hours. For example, if the first grinding time is 12 hours, the second grinding time is 24 hours, the third grinding time is 36 hours, the fourth grinding time is 48 hours, and so on. The fifth grinding time is 60 hours, the sixth grinding time is 72 hours, and then the grinding test is stopped. Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Five points were set at the center of the polished surface of the concrete test block and at the four corners of the flat surface. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a grinding depth-springback value curve with the average grinding depth as the x-axis and the final experimental springback value as the y-axis. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; The specific process is as follows: Step 3.1: After the final impact grinding and rebound test, cut 25 small cube concrete blocks of 100mm×100mm×100mm from the impact grinding surface of the concrete block after the rebound test. Divide the 25 small cube concrete blocks into groups of 3 for compressive strength test, and the extra blocks are reserved. Remove one outlier from the compressive strength data obtained from each group, retain the remaining data, and calculate the average value of all the retained compressive strengths in 8 groups as the compressive strength after impact grinding. Step 3.2: Prepare a small test block using the same raw materials and process as the concrete test block in Step 1. The size of the small test block is the same as that of the small cube concrete test block obtained in Step 3.1. Perform rebound test and compressive strength test on the small test block to obtain the compressive strength and rebound value. Step 3.3: Locate the results of the last grinding and springback test on the grinding depth-springback curve. Mark the vertical axis position corresponding to the found point as the compressive strength after grinding. Based on the compressive strength and springback value after grinding at this point and the compressive strength and springback value obtained in step 3.2, construct a functional relationship between compressive strength and springback value. According to the functional relationship, modify all springback values ​​on the grinding depth-springback curve to the compressive strength after grinding, and modify the vertical axis to compressive strength while keeping the horizontal axis unchanged to obtain the grinding depth-compressive strength curve. The expression for the functional relationship is: (1) In the formula, R represents the compressive strength after grinding, in MPa. m This is the rebound value; Step 4: Conduct in-situ tests in the spillway and combine the scouring depth-compressive strength curve to obtain the final compressive strength; The specific process is as follows: Step 4.1: During the pouring of the spillway of the spillway structure, several ultrasonic sensor units are pre-embedded at equal intervals along the length of the spillway to monitor the thickness of the concrete layer of the spillway. The average value of the concrete layer thickness monitored by each ultrasonic sensor unit is calculated to obtain the average concrete layer thickness. The thickness of the concrete layer of the spillway that has just been poured but not yet put into use is taken as the initial thickness. The difference between the initial thickness and the average concrete layer thickness is used to obtain the scouring depth of the spillway. The distance between two adjacent ultrasonic sensor units is 5m; like Figure 4 Each ultrasonic sensor unit shown includes four sets of ultrasonic sensors, which are pre-embedded on the top surface, two sides and bottom surface of the flood discharge channel. like Figure 5 As shown, each set of ultrasonic sensors is buried at a depth of not less than 4.5 mm from the surface concrete, and the center points of the four sets of ultrasonic sensors are located on the same plane, which is perpendicular to the water flow direction. This plane serves as the sensor monitoring surface. like Figure 6 As shown, each group of ultrasonic sensors includes nine ultrasonic sensors 15 arranged in a 3×3 matrix, with the ultrasonic sensor 15 located in the center on the sensor monitoring surface. The distance between two adjacent ultrasonic sensors 15 in each row and between two adjacent ultrasonic sensors 15 in each column is 10cm. The average value is calculated after removing the four maximum values ​​and four minimum values ​​from the 36 concrete layer thickness data of the spillway monitored by each ultrasonic sensor unit. The ultrasonic pulse emitted by the ultrasonic sensor 15 propagates in the concrete and is reflected when it reaches the interface between the concrete layer of the spillway and the air. The reflected wave is received by the sensor. By measuring the time difference between the emission and reception of the ultrasonic wave and combining it with the propagation speed of the ultrasonic wave in the concrete, the thickness of the concrete layer of the spillway can be obtained using the following formula. The formula for the thickness of the concrete layer in the spillway is as follows:

[0029] In the formula, d is the thickness of the concrete layer of the spillway, in mm; v is the wave velocity, in m / s; Δt is the time difference of ultrasonic wave propagation, in s; in,

[0030] In the formula, v is the wave velocity, in m / s; E is the elastic modulus of the concrete layer of the spillway, in Pa; and ρ is the density, in kg / m³. Step 4.2: Substitute the scouring depth of the spillway obtained in Step 4.1 into the scouring depth-compressive strength curve to obtain the compressive strength of the spillway at the scouring depth. Step 4.3: Select 5 points on the concrete surface of the spillway corresponding to each group of ultrasonic sensors and use a rebound hammer to conduct rebound tests to obtain the field rebound value of each point. Calculate the average of the field rebound values ​​of the 5 points as the final field rebound value. Calculate a correction coefficient by comparing the final field rebound value with the final experimental rebound value obtained in Step 2.2. Use the correction coefficient to correct the compressive strength of the spillway obtained in Step 4.2 to obtain the final compressive strength. The expression for the correction factor is as follows: (2) In the formula, This is the final on-site rebound value. This is the final experimental rebound value; k >1 indicates that the concrete strength of the spillway is higher than that of the concrete test block; k <1 indicates that the concrete strength of the spillway is lower than that of the concrete test block; The expression for the final compressive strength is: (3) In the formula, For the compressive strength of the flood discharge channel, This represents the final compressive strength.

Claims

1. A non-destructive on-site evaluation method for the compressive strength of concrete after impact grinding in spillway structures, characterized in that, The specific steps are as follows: Step 1: Prepare concrete test blocks (9), obtain the surface model of the concrete test blocks (9) by scanning with a handheld 3D scanner, and mesh the surface model to obtain the first mesh model; Step 2: Install the concrete test block (9) in the grinding device for grinding test, and perform rebound test on the grinding surface of the concrete test block after grinding to construct the grinding depth-rebound value curve. Step 3: Reconstruct the grinding depth-springback curve into a grinding depth-compressive strength curve; Step 4: Conduct in-situ tests in the spillway and combine the erosion depth-compressive strength curve to obtain the final compressive strength.

2. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 1, characterized in that, In step 1, the concrete test block (9) is a cube with a size of 50cm×50cm×50cm; The concrete test block (9) has markings along its height, with a spacing of 1 cm between two adjacent markings.

3. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 1, characterized in that, In step 2, the grinding device includes a tank (8) with an open top. The bottom of the tank (8) is cone-shaped. Four electric telescopic rods (3) are evenly spaced on the inner wall of the tank (8) along its circumference. The fixed end of each electric telescopic rod (3) is connected to the inner wall of the tank (8). A stirring chamber (7) is provided on the inner wall of the tank (8). A stirring rod (13) is provided inside the stirring chamber (7). The stirring rod (13) is connected to the output shaft of a motor (14). The motor (14) is connected to the outer wall of the tank (8). A stirring rod (13) is provided on the inner wall of the tank (8) directly below the stirring chamber (7). A circulation chamber (6) is provided, and a first solenoid valve (10) is provided at the outlet of the mixing chamber (7). Several jet nozzles (5) are provided at the bottom of the circulation chamber (6). Several jet nozzles (5) are located above the electric telescopic rod (3). The bottom of the tank (8) is connected to one end of the circulation pipe (4), and the other end of the circulation pipe (4) is connected to the side wall of the circulation chamber (6). A sand storage tank (2) and a water storage tank (1) are provided directly above the mixing chamber (7). A second solenoid valve (11) is provided at the outlet of the sand storage tank (2), and a third solenoid valve (12) is provided at the outlet of the water storage tank (1).

4. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 2, characterized in that, The specific process of step 2 is as follows: Step 2.1: Place the concrete test block (9) between the four electric telescopic rods (3) and extend the electric telescopic rods (3) to clamp and fix the concrete test block (9). Open the second solenoid valve (14) and the third solenoid valve (15), add the sand in the sand storage tank (2) and the water in the water storage tank (1) to the mixing chamber (7) for mixing and mixing to obtain a sand-water mixture. Open the first solenoid valve (10) and input the sand-water mixture into the circulation chamber (6). The sand-water mixture is then sprayed onto the upper surface of the concrete test block (9) through the jet nozzle (5) for grinding for a set time. The ground sand-water mixture then flows into the circulation chamber (6) through the circulation pipe (4) for reuse. Step 2.2: After each grinding, remove the ground concrete test block from the grinding device. After all surfaces of the ground concrete test block are completely dry, use a rebound hammer to select 5 points on the ground surface of the ground concrete test block for rebound testing, obtain the experimental rebound value of each point, and take the average value of the experimental rebound values ​​of the 5 points as the final experimental rebound value. Step 2.3: After the rebound test, use a 3D scanner to scan the rebounded concrete block to obtain the surface model of the rebounded concrete block. Then, use the ScanViewer software built into the 3D scanner to mesh the surface model to obtain a second meshed model. Input both the first and second meshed models into PolyWorks software. Manually define the reference plane through pre-etched coordinates. After defining the reference plane, automatically calculate the average impact depth of the impacted surface of the rebounded concrete block using the distance from the point to the plane function in PolyWorks. Step 2.4: Repeat steps 2.1 to 2.3 to obtain multiple sets of final experimental springback values ​​and the average grinding depth corresponding to each final experimental springback value. Construct a grinding depth-springback value curve with the average grinding depth as the x-axis and the final experimental springback value as the y-axis.

5. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 4, characterized in that, In step 2.2, the five points are set at the center of the polished surface of the concrete test block and at the four corners of the flat position.

6. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a spillway structure according to claim 2, characterized in that, The specific process of step 3 is as follows: Step 3.1: After the last impact grinding and rebound test, cut out several small cube concrete blocks of equal size from the impact grinding surface of the concrete block after the rebound test. Divide the small cube concrete blocks into several groups and conduct compressive strength tests to obtain several groups of compressive strength data. Remove one outlier from the compressive strength data obtained from each group and retain the remaining data. Calculate the average value of all the retained compressive strengths from several groups as the compressive strength after impact grinding. Step 3.2: Prepare a small test block using the same raw materials and process as the concrete test block (9) in Step 1. The size of the small test block is the same as that of the small cube concrete test block obtained in Step 3.

1. Perform rebound test and compressive strength test on the small test block to obtain the rebound value and compressive strength. Step 3.3: Locate the results of the last grinding and springback test on the grinding depth-springback curve. Mark the vertical axis position corresponding to the found point as the compressive strength after grinding. Based on the compressive strength and springback value after grinding at this point and the compressive strength and springback value obtained in step 3.2, construct a functional relationship between compressive strength and springback value. According to the functional relationship, modify all springback values ​​on the grinding depth-springback curve to the compressive strength after grinding, and modify the vertical axis to compressive strength while keeping the horizontal axis unchanged to obtain the grinding depth-compressive strength curve. The expression for the functional relationship is: （1） In the formula, R represents the compressive strength after grinding, in MPa. m This is the rebound value.

7. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 4, characterized in that, The specific process of step 4 is as follows: Step 4.1: During the pouring of the spillway of the spillway structure, several ultrasonic sensor units are pre-embedded at equal intervals along the length of the spillway to monitor the thickness of the concrete layer of the spillway. The average value of the concrete layer thickness monitored by each ultrasonic sensor unit is calculated to obtain the average concrete layer thickness. The thickness of the concrete layer of the spillway that has just been poured but not yet put into use is taken as the initial thickness. The difference between the initial thickness and the average concrete layer thickness is used to obtain the scouring depth of the spillway. Each ultrasonic sensor unit includes four sets of ultrasonic sensors, which are pre-embedded on the top, two sides and bottom of the flood discharge channel. Step 4.2: Substitute the scouring depth of the spillway obtained in Step 4.1 into the scouring depth-compressive strength curve to obtain the compressive strength of the spillway at the scouring depth. Step 4.3: Select 5 points on the concrete surface of the spillway corresponding to each group of ultrasonic sensors and use a rebound hammer to conduct rebound tests to obtain the field rebound value of each point. Calculate the average of the field rebound values ​​of the 5 points as the final field rebound value. Calculate a correction coefficient by comparing the final field rebound value with the final experimental rebound value obtained in step 2.

2. Use the correction coefficient to correct the compressive strength of the spillway obtained in step 4.2 to obtain the final compressive strength.

8. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 7, characterized in that, In step 4.1, each set of ultrasonic sensors is buried at a depth of not less than 4.5 mm from the surface concrete, and the center points of the four sets of ultrasonic sensors are located on the same plane, which is perpendicular to the water flow direction. This plane serves as the sensor monitoring surface.

9. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 7, characterized in that, In step 4.1, each group of ultrasonic sensors includes 9 ultrasonic sensors arranged in a 3×3 matrix, with the ultrasonic sensor at the center located on the sensor monitoring surface. The distance between two adjacent ultrasonic sensors in each row and between two adjacent ultrasonic sensors in each column is 10cm.

10. The method for on-site non-destructive evaluation of the compressive strength of concrete after impact grinding in a drainage structure according to claim 7, characterized in that, In step 4.3, the expression for the correction coefficient is: （2） In the formula, This is the final on-site rebound value. This is the final experimental rebound value; k >1 indicates that the hardness of the spillway concrete is higher than that of the concrete test block; k <1 indicates that the hardness of the spillway concrete is lower than that of the concrete test block; The expression for the final compressive strength is: （3） In the formula, For the compressive strength of the flood discharge channel, This represents the final compressive strength.

Images