A drop-hammer deflection detection device

Abstract

This invention relates to a falling weight deflection testing device, comprising a device support and a falling weight capable of vertical movement for impacting the ground. The device also includes a detection beam with a displacement measuring component located at the center of the falling weight for measuring road surface settlement. The detection beam is supported on the road surface by detection beam legs, and the distance between the detection beam legs and the displacement measuring component is greater than the radius of influence of the falling weight on the road surface under test. The falling weight has a clearance space to avoid the displacement measuring component. This invention solves the technical problem in the prior art where the displacement sensor cannot accurately measure road surface settlement displacement because the leveling screw is within the deflection influence range.

Description

Technical Field

[0001] This invention relates to a falling weight type deflection testing device in the field of road deflection testing. Background Technology

[0002] In recent years, the research and development of non-destructive testing technology for pavements has received increasing attention both domestically and internationally. Deflection, as the most important indicator for evaluating pavement structural condition, has seen rapid development in its measurement equipment and analysis techniques. Since the invention of the beam deflectometer, pavement deflection testing equipment has evolved from static deflectometers to falling weight deflectometers that simulate traffic loads.

[0003] Existing falling weight deflectometers, such as the portable falling weight deflectometer disclosed in Chinese patent CN2869109Y, consist of a release mechanism, a circular weight, a guide rod, a bearing device, and a measurement system. The lower guide rod passes through the weight, a buffer pad, and a transition plate, and is vertically fixed to the bearing frame. The release mechanism is fixed to the guide rod according to the falling height of the weight. The bearing frame is fixed to the bearing plate. A force sensor is located between the bearing frame and the transition plate. An auxiliary deflection measuring device is connected to the bearing plate via a positioning pin. The auxiliary deflection measuring device consists of a crossbeam, a displacement sensor fixed to the crossbeam, a leveling screw, and a leveling bubble. The displacement sensor is used to measure the ground subsidence displacement.

[0004] During measurement, the weight is manually fixed to the release device, allowing it to fall freely along the guide rod. The signals output by the force sensor and displacement sensor are processed by the signal acquisition and processing system to ultimately plot the deflection basin curve centered on the point of impact. The existing falling weight deflectometer has the following problem: the displacement sensor is located next to the falling weight, not at its center, while the maximum deflection value is at the exact center of the falling weight. Therefore, it cannot accurately measure the maximum deflection value of the deflection basin. More importantly, when the falling weight impacts the ground, a deflection basin is generated centered on the impact point. For various types of pavement structures, the radius of influence of this basin generally does not exceed 3.6 meters; for flexible base asphalt pavements, it generally does not exceed 2.4 meters. However, in the existing technology, the leveling screw is located within the basin, i.e., within the deflection influence range. When the falling weight impacts the ground, the ground forms a basin, and the position of the leveling screw also drops as the basin forms. This causes the base position of the displacement sensor to change, making it impossible to accurately obtain the ground's downward displacement. Summary of the Invention

[0005] The purpose of this invention is to provide a falling weight type deflection detection device to solve the technical problem in the prior art that the displacement sensor cannot accurately measure the road surface settlement displacement because the leveling screw is within the deflection influence range.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A falling weight deflection testing device includes a device support and a falling weight that can move up and down to impact the ground. The falling weight deflection testing device also includes a testing beam with a displacement measuring component located at the center of the falling weight for measuring road surface settlement. The testing beam is supported on the road surface by testing beam legs. The distance between the testing beam legs and the displacement measuring component is greater than the radius of influence of the falling weight on the deflection of the road under test. The falling weight is provided with a measuring component avoidance space to avoid the displacement measuring component.

[0008] The detection beam passes through the clearance space of the measuring component in the front-to-back direction, and the detection beam legs are respectively set at both ends of the detection beam. The displacement measuring component is a displacement measuring sensor.

[0009] The detection beam is fixedly connected to the detection beam support legs.

[0010] The detection beam has one support leg, and the detection beam is hinged to the detection beam support leg. The displacement measuring component consists of a measuring rod with its lower end for contacting the road surface. A displacement measuring sensor is installed between the detection beam and the road surface, and the displacement measuring sensor and the measuring rod are respectively located on both sides of the detection beam support leg.

[0011] The space for the measuring component to avoid obstacles includes an upper space and a lower space. The width of the lower space is smaller than that of the upper space. The displacement measuring component is inserted into the lower space along the vertical direction, and the detection beam extends into the upper space.

[0012] The drop hammer is guided and moved along the vertical direction to be assembled on the device frame.

[0013] The bottom of the device frame is equipped with wheels.

[0014] The beneficial effects of this invention are as follows: In this invention, the detection beam is supported on the road surface by the detection beam legs. The distance between the detection beam legs and the displacement measuring component is greater than the radius of influence of the drop hammer on the deflection of the road under test. When the drop hammer impacts the road surface and a deflection basin is generated on the road surface, the detection beam legs are not affected by the deflection basin, thus providing a reliable basis for the measurement of the displacement measuring component. The measurement component avoidance space is set on the drop hammer so that the displacement measuring component can be located at the center of the drop hammer. The maximum deflection value of the deflection basin is generated at the center of the drop hammer, thus the maximum deflection value of the deflection basin can be obtained. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0016] Figure 2This is a schematic diagram showing the cooperation between the falling hammer, the detection beam, and the displacement measuring component in this invention;

[0017] Figure 3 yes Figure 1 A schematic diagram of the structure of a medium-pressure hydraulic sensor;

[0018] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the present invention. Detailed Implementation

[0019] Example 1 of a falling weight deflection testing device Figures 1-3 As shown: a device bracket 12 with a walking wheel 3 at the bottom is provided, and a drop hammer 6 for impacting the ground is mounted on the device bracket along the vertical direction. In this invention, the device support 12 includes a support sleeve 11 and a sleeve top cover 10 fixed to the top of the support sleeve 11. The traveling wheel 3 is installed at the bottom of the support sleeve 11. The drop hammer 6 is guided and moved in the inner hole of the support sleeve 11. A vertical pull rod 22 is fixed to the top of the drop hammer 6. The upper end of the vertical pull rod 22 protrudes from the upper side of the sleeve top cover 10. A pull rod handle 9 is provided at the top of the vertical pull rod. A pull rod sleeve 7 is fixed on the sleeve top cover 10 and sleeved around the vertical pull rod. A tightening screw 8 is connected radially to the pull rod sleeve 7 for tightening the vertical pull rod and fixing the position of the drop hammer. When performing deflection testing, the tightening screw needs to be loosened. The tightening screw does not affect the up and down movement of the drop hammer. When it is necessary to move the position of the deflection testing device, the drop hammer is raised to a high position and the tightening screw is tightened to fix the position of the drop hammer.

[0020] The falling weight deflection testing device also includes a testing beam 5 extending along the front-to-back direction. A displacement measuring component 2 for measuring road surface settlement is installed on the testing beam 5 at the center of the falling weight. In this embodiment, the displacement measuring component 2 is a displacement measuring sensor, which is a linear displacement sensor resistance ruler, including a telescopic probe at the lower end for contacting the road surface. The detection beam 5 is supported on the road surface by detection beam legs 4. In this embodiment, there are two detection beam legs, which are fixed at both ends of the detection beam. The distance between each detection beam leg and the displacement measuring component is greater than the radius of influence of the drop hammer on the deflection of the road to be measured. The drop hammer is provided with a measuring component avoidance space 15 to avoid the displacement measuring component. The radius of influence of deflection varies for different road surfaces. For flexible base asphalt pavement, the radius of influence of the bend generally does not exceed 2.4 meters. Therefore, when performing deflection testing on flexible base asphalt pavement, the distance between the detection beam legs 4 and the displacement measuring component 2 is 2.4 meters. For various types of structural pavement, the radius of influence of the bend generally does not exceed 3.6 meters. Therefore, when the distance between the detection beam legs and the displacement measuring component is 3.6 meters, this drop hammer deflection testing device can perform deflection testing on various types of structural pavement.

[0021] The clearance space for the measuring components includes an upper clearance space 13 and a lower clearance space 14. The width of the lower clearance space is smaller than that of the upper clearance space. The displacement measuring component 2 passes through the lower clearance space in the vertical direction, and the detection beam 5 passes through the upper clearance space 13 in the front-back direction. The device support is provided with a detection beam channel 24 for the detection beam to pass through in the front-back direction. The vertical height of the detection beam channel 24 is higher than that of the detection beam 5. When the falling weight deflection testing device needs to be moved, the height of the detection beam can be raised, and a pad can be placed between the bottom of the detection beam and the detection beam channel. This can prevent the detection beam legs from contacting the road surface and affecting the movement of the falling weight deflection testing device. Alternatively, the detection beam can be manually lifted to the next testing position first, and then the device support can be moved to the corresponding position. That is to say, in this invention, the detection beam and the displacement measuring component are set independently of the falling weight and do not move with the falling weight.

[0022] A hydraulic pressure sensor 1, arranged around the displacement measuring component, is fixed to the bottom of the drop hammer 6. The hydraulic pressure sensor 1 includes an inner sleeve 19, an outer sleeve 17, a sensor fixing plate 18 fixed to the top of the inner sleeve 19 and the outer sleeve 17, and a force-transmitting diaphragm 20 fixed to the bottom of the inner sleeve 19 and the outer sleeve 17. The inner sleeve 19, the outer sleeve 17, the sensor fixing plate 18, and the force-transmitting diaphragm 20 form a hydraulic cavity filled with liquid. A hydraulic sensor 16 for detecting liquid pressure is fixed on the outer sleeve and connected to the hydraulic cavity. The force-transmitting diaphragm 20 can transmit force to the liquid through deformation in the vertical direction. In this embodiment, the force-transmitting diaphragm is welded and sealed to the inner sleeve and the outer sleeve. The lower end of the force-transmitting diaphragm has a force-transmitting head 21 for contacting the road surface. When the hammer moves downward and impacts the road surface, the impact force of the hammer is transmitted to the road surface through a hydraulic pressure sensor. The force transmission head is subjected to a reaction force, and the force transmission diaphragm applies pressure to the liquid. The hydraulic sensor detects the liquid pressure, and the impact force of the hammer on the road surface can be obtained through the effective force transmission area of ​​the force transmission diaphragm.

[0023] In this invention, the distance between the two detection beam legs on the detection beam and the displacement measuring component is greater than the radius of influence of the falling hammer on the road surface. In other words, the two detection beam legs are outside the radius of influence of the falling hammer on the road surface. Therefore, when the falling hammer impacts the road surface, the position and height of the detection beam will not change, thus providing a stable measuring base for the displacement measuring component. Before the falling hammer impacts the road surface, the displacement measuring component measures the height h1 of the center position of the falling hammer. After the falling hammer impacts the road surface, the displacement measuring component measures the maximum displacement h2 of the center position of the falling hammer. Then, the impact bend of the road surface = h2 - h1. After the impact ends, after a period of time, when the bend rebounds, the displacement measuring component measures the height h3 of the center position of the falling hammer. Then, h2 - h3 is equal to the rebound bend of the road surface. In other words, the impact bend and rebound bend of the road surface can be accurately detected by this device. A hydraulic pressure sensor can be used to obtain the impact force of the drop hammer on the road surface to determine whether the impact force meets the test requirements. Hydraulic pressure sensors can withstand high impact forces, have a long service life, and are positioned between the drop hammer and the road surface, directly contacting the road surface, thus accurately obtaining the impact force on the road surface. In other embodiments of the invention, the displacement measuring component can also be a laser displacement sensor; the drop hammer can also be guided and moved vertically in conjunction with the device support via a vertical tie rod and the device support; the hydraulic pressure sensor does not necessarily have to be a diaphragm structure. For example, a hydraulic pressure sensor includes a cylinder and a piston, with liquid filling the piston chamber. The piston is used to transmit force in contact with the road surface. When the piston impacts the road surface, the piston moves and applies pressure to the liquid in the piston chamber. The pressure sensor measures the liquid pressure at this time and calculates the force on the piston based on the effective force transmission area of ​​the piston.

[0024] Example 2 of a falling weight deflection testing device Figure 4 As shown: Example 2 differs from Example 1 in that there is one detection beam leg 4, and the detection beam 5 is hinged to the detection beam leg 4. The displacement measuring component 2 consists of a measuring rod whose lower end is used to contact the road surface. The measuring rod is a rigid rod. A displacement measuring sensor 30 is set between the detection beam and the road surface. The displacement measuring sensor 30 and the measuring rod are respectively set on both sides of the detection beam leg 4. Item 31 in the figure shows a sensor bracket that facilitates the cooperation of the displacement measuring sensor. When in use, it is placed on the road surface and includes a vertical arm and a horizontal arm. When in use, the sensor 30 is placed between the detection beam and the horizontal arm of the sensor bracket. When the detection beam rotates around the hinge axis, the displacement sensor 30 can measure the swing displacement of the right end of the detection beam. According to the lever arm conversion, the displacement change at the measuring rod can be obtained.

Claims

1. A falling weight type deflection testing device, comprising a device support and a falling weight capable of moving up and down to impact the ground, characterized in that: The falling weight deflection testing device also includes a testing beam, on which a displacement measuring component for measuring road surface settlement is located at the center of the falling weight. The testing beam is supported on the road surface by testing beam legs. The distance between the testing beam legs and the displacement measuring component is greater than the radius of influence of the falling weight on the road surface under test. The falling weight is provided with a measuring component avoidance space to avoid the displacement measuring component. A hydraulic pressure sensor is fixed at the bottom of the falling weight and arranged around the displacement measuring component. The hydraulic pressure sensor includes an inner sleeve, an outer sleeve, a sensor fixing plate fixed to the top of the inner sleeve and the outer sleeve, and a force transmitting diaphragm fixed to the bottom of the inner sleeve and the outer sleeve. The inner sleeve, the outer sleeve, the sensor fixing plate, and the force transmitting diaphragm form a hydraulic cavity, which is filled with liquid.

2. The falling weight deflection testing device according to claim 1, characterized in that: The detection beam passes through the clearance space of the measuring component in the front-to-back direction, and the detection beam legs are respectively set at both ends of the detection beam. The displacement measuring component is a displacement measuring sensor.

3. The falling weight deflection testing device according to claim 2, characterized in that: The detection beam is fixedly connected to the detection beam support legs.

4. The falling weight deflection testing device according to claim 1, characterized in that: The detection beam has one support leg, and the detection beam is hinged to the detection beam support leg. The displacement measuring component consists of a measuring rod with its lower end for contacting the road surface. A displacement measuring sensor is installed between the detection beam and the road surface, and the displacement measuring sensor and the measuring rod are respectively located on both sides of the detection beam support leg.

5. The falling weight deflection testing device according to claim 1, characterized in that: The space for the measuring component to avoid obstacles includes an upper space and a lower space. The width of the lower space is smaller than that of the upper space. The displacement measuring component is inserted into the lower space along the vertical direction, and the detection beam extends into the upper space.

6. The falling weight deflection testing device according to any one of claims 1 to 5, characterized in that: The drop hammer is guided and moved along the vertical direction to be mounted on the device support.

7. The falling weight deflection testing device according to claim 6, characterized in that: The device support is equipped with wheels at the bottom.

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