Device and method for testing impact shear performance of concrete-rock interface using Hopkinson bar

Abstract

The present invention discloses a device and method for testing the impact shear performance of a concrete-rock interface using a Hopkinson bar. The device includes a lower shear box fixed to an equipment support through a fixing device. The lower shear box comprises two symmetrically arranged steel plates, one of which is a slidable steel plate of the lower shear box, and the other is integrally arranged with the fixing device. An upper shear box is provided above the lower shear box. The upper shear box comprises two symmetrically arranged steel plates. An incident bar is provided outside one of the steel plates, and a transmission bar is provided outside the other steel plate. Compared with the prior art, the present invention has the following advantages: the device optimizes the overall structure, mostly adopts a detachable installation method, and integrally arranges the incident bar and the upper shear box to ensure that they move together when a load is applied; the device and method can directly measure the shear load at different impact rates; and it is applicable to specimens of multiple sizes, realizing compression-shear failure under complex stresses.

Description

Technical Field

[0001] The present invention belongs to the field of concrete material testing, and relates to a shear test device for the concrete-rock interface, specifically a device and method for testing the impact shear resistance of the concrete-rock interface used in a Hopkinson bar. Background Art

[0002] The interface performance at the heel of a dam is affected by the interaction between rock and concrete. Studying the bonding performance of these two materials, concrete and rock, is extremely important for evaluating and mastering the reinforcement and seismic performance at the heel of a dam in a water conservancy project.

[0003] Currently, most of the interface shear tests are static loading. In actual situations, structures are also subjected to seismic loads and impact loads, such as the impact of river water, etc. Currently, there is very little research on the shear performance of the concrete-rock interface under dynamic loading, especially impact loads. One of the reasons is that the interface shear test under impact requires high equipment requirements and data acquisition is difficult. How to perform impact loading for the interface shear test using existing test devices has become a difficult point.

[0004] Currently, there are many ways to test the bonding performance between concrete and rock, such as a closed-box direct shear box and cube diagonal shear. However, these two methods have not been applied to the Hopkinson bar for the interface shear test of two-phase materials. From the perspective of application difficulty: on the one hand, the fit between the closed-box direct shear box and the specimen affects the test results; on the other hand, the shear and compression loads in the diagonal shear test are controlled by the interface angle, and the change range is limited. Therefore, both of these methods have certain deficiencies in testing the impact shear resistance. Summary of the Invention

[0005] Technical problems to be solved: In order to overcome the deficiencies of the prior art, solve the problems of loading rate limitation and difficult data acquisition existing in the test of the concrete-rock interface shear performance, and achieve the test of interface shear failure under different impact rates and different compressive stresses, the present invention provides a device and method for testing the impact shear resistance of the concrete-rock interface used in a Hopkinson bar.

[0006] Technical solution: A device for testing the impact shear resistance of the concrete-rock interface of a Hopkinson bar. The device includes a lower shear box fixed to an equipment support through a fixing device. The lower shear box includes two symmetrically arranged steel plates, one of which is a slidable steel plate of the lower shear box, and the other is integrally arranged with the fixing device. An upper shear box is provided above the lower shear box. The upper shear box includes two symmetrically arranged steel plates. An incident bar is provided outside one of the steel plates, and a transmission bar is provided outside the other steel plate. A PVDT dynamic pressure sensor is provided between the incident bar and the steel plate, and strain gauges are provided on the incident bar. A bearing plate is provided inside the upper shear box, and a tension-compression sensor is provided above the bearing plate. The sensor is connected to a digital display meter.

[0007] Preferably, shear box screws are provided on both the upper shear box and the lower shear box. The shear box screws are provided at the four corners of the steel plates and penetrate through the two steel plates.

[0008] Preferably, a connecting piece is provided between the upper shear box and the incident bar, and the incident bar and the connecting piece are fixedly connected through an adhesive layer.

[0009] Preferably, the connecting piece is fixed to the steel plate through a shear box screw.

[0010] Preferably, screw hole positions corresponding to the lower shear box and the fixing device are provided between the lower shear box and the fixing device, and they are fixedly connected through bolts.

[0011] Preferably, a concrete-rock specimen is provided inside the lower shear box, and the interface of the concrete-rock specimen is higher than the interface of the steel plate of the lower shear box.

[0012] Preferably, the bearing plate is placed on the concrete-rock specimen, and the interface of the concrete-rock specimen is lower than the interface of the steel plate of the upper shear box; and the interface of the concrete-rock specimen is located on the horizontal center line between the interface of the steel plate of the lower shear box and the interface of the steel plate of the upper shear box.

[0013] The method for testing the impact shear resistance of the concrete-rock interface of a Hopkinson bar as described in any one of the above, the method includes the following steps:

[0014] S1. Pretreat the bonding surface of the rock specimen. Put the rock specimen into a prepared test mold, pour concrete, and cure it to the age to be measured to obtain a concrete-rock specimen.

[0015] S2. Calibrate the PVDT dynamic pressure sensor. Regard the sensor as an ordinary compressive cylindrical specimen, paste it between the incident bar and the transmission bar, use the Hopkinson bar equipment to impact, and obtain the stress at different impact speeds by adjusting the bullet speed to complete the calibration of the sensor.

[0016] S3. Paste a PVDT dynamic pressure sensor on one side of the steel plate of the upper shear box. Fix the connecting piece on the incident bar with an adhesive layer. Align the connecting piece with the threaded hole on the steel plate of the upper shear box, pass through the shear box screw, and fix the incident bar and the connecting piece on the steel plate of the upper shear box with bolts;

[0017] S4. Fix the lower shear box on the equipment support through the fixing device. Place the concrete-rock specimen, adjust the shear box screw, and move the slidable steel plate of the lower shear box to clamp the specimen to ensure that there is no relative slip between the specimen and the lower shear box;

[0018] S5. Adjust the height of the incident bar so that the distance from the upper shear box to the interface of the concrete-rock specimen is equal to the distance from the lower shear box below the interface of the concrete-rock specimen;

[0019] S6. Adjust the shear box screw on the upper shear box so that the steel plate on the upper shear box clamps the concrete-rock specimen;

[0020] S7. After connecting the tension-compression sensor and the bearing plate, place them on the upper surface of the specimen in S6, and apply compressive stress through a split hydraulic jack;

[0021] S8. Conduct impact loading using a Hopkinson pressure bar, adjust the bullet speed, and obtain the shear stress-displacement curve of the concrete-rock specimen interface under different impact speeds and compressive stresses.

[0022] When testing the impact shear resistance of the concrete-rock interface through the above device and method, the impact load is transmitted from the incident bar to the upper shear box, and the incident bar and the upper shear box move together when applying the load; the load is transmitted from the upper shear box to the concrete, and at the same time, the rock on the lower side of the concrete-rock interface is restricted from displacement by the lower shear box fixed on the equipment support, so the interface between the concrete and the rock is in a shear stress state. The compressive stress is transmitted from the jack to the concrete-rock specimen through the bearing plate. The lower shear box is fixed on the equipment support through the fixing device, jointly restricting the movement of the concrete-rock specimen in the loading direction, so that the interface undergoes shear failure under the impact load. The shear displacement is measured by a strain gauge, and the calculation formula is: where c 0 is the wave propagation speed in the bar, which is 5060 - 5100 m / s, ε i is the incident strain, and ε r is the reflected strain; the impact load F is measured by the PVDT dynamic pressure sensor, and the schematic diagram of the measurement principle of the PVDT dynamic pressure sensor is as Figure 1 shown; the normal load P is measured by the tension-compression sensor and read through an external digital display instrument. The finally obtained shear stress-displacement curve of the concrete-rock specimen interface is as Figure 2As shown in the figure, the shear strength is obtained by dividing the impact load F by the bonding area As between the PVDT dynamic pressure sensor and the steel plate, and the compressive stress is obtained by dividing the normal load P by the loading area A on the load-bearing plate.

[0023] Beneficial effects: (1) The device of the present invention optimizes the overall structure, mostly adopts a detachable installation method, and integrates the incident bar and the upper shear box, ensuring that the two move together when applying the load, so that the shear displacement can be calculated through the incident pulse and the reflected pulse; (2) The device and method can be applied to the Hopkinson bar test for the impact shear performance of the concrete-rock interface, directly measure the shear load at different impact rates; and are applicable to specimens of multiple sizes, realizing the compressive failure under complex stresses. Description of the drawings

[0024] Figure 1 is the circuit diagram for PVDT voltage acquisition;

[0025] Figure 2 is the shear stress-shear displacement curve of the concrete-rock specimen interface;

[0026] Figure 3 is the three-dimensional structure schematic diagram of the device of the present invention;

[0027] Figure 4 is the two-dimensional structure schematic diagram of the device of the present invention, where (a) is the top view and (b) is the front view;

[0028] Figure 5 is the two-dimensional drawing of the connecting piece between the upper shear box and the incident bar, where (a) is the top view and (b) is the front view;

[0029] Figure 6 is the two-dimensional drawing of the fixing device between the lower shear box and the equipment support, where (a) is the top view and (b) is the left view;

[0030] Among them, 1, connecting piece; 2, glue layer; 3, upper shear box; 4, shear box screw; 5, load-bearing plate; 6, tension-compression sensor; 7, incident bar; 8, strain gauge; 9, transmission bar; 10, PVDT dynamic pressure sensor; 11, sliding steel plate of the lower shear box; 12, lower shear box; 13, fixing device; 14, interface of the concrete-rock specimen; 15, equipment support; 16, digital display instrument; 17, screw hole positions corresponding to the lower shear box and the fixing device. Detailed implementation manners

[0031] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0032] Embodiment 1

[0033] As Figures 3 - 6 shown, a device for testing the impact shear resistance of a concrete-rock interface for a Hopkinson bar, the device includes a lower shear box 12 fixed to an equipment support 15 through a fixing device 13, the lower shear box 12 includes two symmetrically arranged steel plates, one of which is a slidable steel plate 11 of the lower shear box, and the other is integrally arranged with the fixing device 13; an upper shear box 3 is provided above the lower shear box 12, the upper shear box 3 includes two symmetrically arranged steel plates, an incident bar 7 is provided outside one of the steel plates, and a transmission bar 9 is provided outside the other steel plate, a PVDT dynamic pressure sensor 10 is provided between the incident bar 7 and the steel plate, and a strain gauge 8 is provided on the incident bar 7; a bearing plate 5 is provided in the upper shear box 3, a tension-compression sensor 6 is provided above the bearing plate 5, and the sensor is connected to a digital display instrument 16.

[0034] Shear box screws 4 are provided on both the upper shear box 3 and the lower shear box 12, the shear box screws 4 are provided at the four corners of the steel plates and penetrate through the two steel plates.

[0035] A connecting piece 1 is provided between the upper shear box 3 and the incident bar 7, and the incident bar 7 and the connecting piece 1 are fixedly connected through an adhesive layer 2.

[0036] The connecting piece 1 is fixed to the steel plate through the shear box screw 4.

[0037] Screw holes 17 corresponding to the lower shear box and the fixing device are opened between the lower shear box 12 and the fixing device 13, and they are fixedly connected through bolts.

[0038] A concrete-rock specimen is provided in the lower shear box 12, and the interface 14 of the concrete-rock specimen is higher than the interface of the steel plate of the lower shear box 12.

[0039] The bearing plate 5 is placed on the concrete-rock specimen, and the interface 14 of the concrete-rock specimen is lower than the interface of the steel plate of the upper shear box 3; and the interface 14 of the concrete-rock specimen is located on the horizontal center line between the interface of the steel plate of the lower shear box 12 and the interface of the steel plate of the upper shear box 3.

[0040] The method for testing the impact shear resistance of a concrete-rock interface for a Hopkinson bar, the method includes the following steps:

[0041] S1. Pretreat the bonding surface of the rock specimen. Place the rock specimen into the prepared test mold, pour concrete, and cure it until the specified age to obtain a concrete-rock specimen.

[0042] S2. Calibrate the PVDT dynamic pressure sensor 10. Treat the sensor as an ordinary compressive cylindrical specimen, attach it between the incident bar 7 and the transmission bar 9, use the Split Hopkinson Pressure Bar (SHPB) device to impact, and obtain the stress at different impact velocities by adjusting the bullet velocity to complete the calibration of the sensor.

[0043] S3. Paste the PVDT dynamic pressure sensor 10 on one side of the steel plate of the upper shear box 3. Use the glue layer 2 to fix the connector 1 on the incident bar 7, align the threaded holes on the connector 1 and the steel plate of the upper shear box 3, pass through the shear box screw 4, and fix the incident bar 7 and the connector 1 to the steel plate of the upper shear box 3 with bolts.

[0044] S4. Fix the lower shear box 12 to the equipment support 15 through the fixing device 13, place the concrete-rock specimen, adjust the shear box screw 4, and move the slidable steel plate 11 of the lower shear box to clamp the specimen to ensure that there is no relative slip between the specimen and the lower shear box 12.

[0045] S5. Adjust the height of the incident bar 7 so that the distance from the upper shear box 3 above the interface 14 of the concrete-rock specimen is equal to the distance from the lower shear box 12 below the interface 14 of the concrete-rock specimen.

[0046] S6. Adjust the shear box screw 4 on the upper shear box 3 so that the steel plate on the upper shear box 3 clamps the concrete-rock specimen.

[0047] S7. Connect the tensile-compressive sensor 6 and the load-bearing plate 5 and place them on the upper surface of the specimen in S6, and apply compressive stress through a split hydraulic jack.

[0048] S8. Use the Split Hopkinson Pressure Bar for impact loading, adjust the bullet velocity, and obtain the shear stress-displacement curve of the interface of the concrete-rock specimen at different impact velocities and compressive stresses.

[0049] When testing the impact shear resistance of the concrete-rock interface by the above device and method, the impact load is transmitted from the incident bar 7 to the upper shear box 3. When applying the load, the incident bar 7 and the upper shear box 3 move together. The load is transmitted from the upper shear box 3 to the concrete, and at the same time, the displacement of the rock on the lower side of the concrete-rock interface 14 is restricted by the lower shear box 12 fixed on the equipment support 15. Therefore, the interface between the concrete and the rock is in a shear stress state. The compressive stress is transmitted from the jack to the concrete-rock specimen through the bearing plate 5. The lower shear box 12 is fixed on the equipment support 15 by the fixing device 13, jointly restricting the movement of the concrete-rock specimen in the loading direction, so that the interface undergoes shear failure under the impact load. The shear displacement is measured by the strain gauge 8, and the calculation formula is: where c 0 is the wave propagation velocity in the bar, which is 5060 - 5100 m / s, and ε i is the incident strain, and ε r is the reflected strain; the impact load F is measured by the PVDT dynamic pressure sensor 10, and the schematic diagram of the measurement principle of the PVDT dynamic pressure sensor 10 is as shown in Figure 1 ; the normal load P is measured by the tension-compression sensor 6 and read through the external digital display instrument 16. The final shear stress-displacement curve of the interface 14 of the concrete-rock specimen is as shown in Figure 2 . Among them, the shear strength is obtained by dividing the impact load F by the bonding area As between the PVDT dynamic pressure sensor 10 and the steel plate, and the compressive stress is obtained by dividing the normal load P by the loading area A on the bearing plate 5.

Claims

1. Device for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar, Characterized in that, The device includes a lower shear box (12) fixed to an equipment support (15) through a fixing device (13). The lower shear box (12) includes two symmetrically arranged steel plates, one of which is a slidable steel plate (11) of the lower shear box, and the other is integrally arranged with the fixing device (13); above the lower shear box (12) is an upper shear box (3). The upper shear box (3) includes two symmetrically arranged steel plates. On the outside of one steel plate is an incident bar (7), and on the outside of the other steel plate is a transmission bar (9). Between the incident bar (7) and the steel plate is a PVDT dynamic pressure sensor (10), and on the incident bar (7) is a strain gauge (8); inside the upper shear box (3) is a bearing plate (5), above the bearing plate (5) is a tension-compression sensor (6), and the sensor is connected to a digital display instrument (16); Shear box screws (4) are provided on both the upper shear box (3) and the lower shear box (12). The shear box screws (4) are arranged at the four corners of the steel plates and penetrate through the two steel plates; A connecting piece (1) is provided between the upper shear box (3) and the incident bar (7), and the incident bar (7) and the connecting piece (1) are fixedly connected through an adhesive layer (2); The Hopkinson bar is used for impact loading. By adjusting the bullet velocity, the shear stress-displacement curves of the concrete-rock specimen interface under different impact velocities and compressive stresses are obtained. The shear displacement μ is measured by a strain gauge (8), and the calculation formula is as follows: where c 0 is the wave propagation velocity in the bar, which is 5060 - 5100 m / s, and ε i is the incident strain, and ε r is the reflected strain.

2. The device for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar according to claim 1, Characterized in that, The connecting piece (1) is fixed to the steel plate through the shear box screw (4).

3. The device for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar according to claim 1, Characterized in that, Screw hole positions (17) corresponding to the lower shear box and the fixing device are opened between the lower shear box (12) and the fixing device (13), and they are fixedly connected by bolts.

4. The device for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar according to claim 1, Characterized in that, A concrete-rock specimen is provided inside the lower shear box (12), and the interface (14) of the concrete-rock specimen is higher than the interface of the steel plate of the lower shear box (12).

5. The device for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar according to claim 1, Characterized in that, The bearing plate (5) is placed on the concrete-rock specimen, and the interface (14) of the concrete-rock specimen is lower than the interface of the steel plate of the upper shear box (3); and the interface (14) of the concrete-rock specimen is located on the horizontal midline between the interface of the steel plate of the lower shear box (12) and the interface of the steel plate of the upper shear box (3).

6. Method for using the device according to any one of claims 1-5 for testing the impact shear resistance performance of the concrete-rock interface for a Hopkinson bar, Characterized in that, The method includes the following steps: S1. Pretreat the bonding surface of the rock specimen, put the rock specimen into a prepared test mold, pour concrete, cure to the age to be measured, and make a concrete-rock specimen; S2. Calibrate the PVDT dynamic pressure sensor (10). Treat the sensor as an ordinary compressive cylindrical specimen and attach it between the incident bar (7) and the transmission bar (9). Use the Split Hopkinson Pressure Bar (SHPB) device to impact. By adjusting the bullet velocity, obtain the stresses at different impact velocities to complete the calibration of the sensor. S3. Paste the PVDT dynamic pressure sensor (10) on one side of the steel plate of the upper shear box (3). Use the glue layer (2) to fix the connector (1) on the incident bar (7). Align the threaded holes on the connector (1) and the steel plate of the upper shear box (3), pass the shear box screw (4) through, and fix the incident bar (7) and the connector (1) to the steel plate of the upper shear box (3) with bolts. S4. Fix the lower shear box (12) to the equipment support (15) through the fixing device (13). Place the concrete-rock specimen, adjust the shear box screw (4), and move the slidable steel plate (11) of the lower shear box to clamp the specimen to ensure that there is no relative slip between the specimen and the lower shear box (12). S5. Adjust the height of the incident bar (7) so that the distance from the upper shear box (3) above the interface (14) of the concrete-rock specimen is equal to the distance from the lower shear box (12) below the interface (14) of the concrete-rock specimen. S6. Adjust the shear box screw (4) on the upper shear box (3) so that the steel plate on the upper shear box (3) clamps the concrete-rock specimen. S7. After connecting the tension-compression sensor (6) and the load-bearing plate (5), place them on the upper surface of the specimen in S6, and apply compressive stress through a split hydraulic jack. S8. Conduct impact loading using the Split Hopkinson Pressure Bar (SHPB), adjust the bullet velocity, and obtain the shear stress-displacement curve of the interface of the concrete-rock specimen under different impact velocities and compressive stresses.

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