A pendulum tester and testing method for measuring the friction coefficient between concrete and rock

Abstract

The present invention belongs to the technical field of bridge engineering, and particularly relates to a pendulum instrument and a testing method for measuring the friction coefficient between concrete and rock. The pendulum instrument for measuring the friction coefficient between concrete and rock includes a test system and a control system. The test system includes a skid block and a concrete slide plate, and the concrete slide plate is fixed on the skid block with fixing screws. The control system includes a solenoid valve type hydraulic oil pump, and the positive pressure generated by the solenoid valve hydraulic oil pump is transmitted to the skid block through a hydraulic oil pipe and a spring. The present invention provides a pendulum instrument and a testing method for measuring the friction coefficient between concrete and rock, which can consider different overburden pressures and realize the rapid testing of the friction coefficient between concrete and rock.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge engineering, and particularly relates to a pendulum tester for measuring the friction coefficient between concrete and rock and a testing method therefor. Background Art

[0002] Prior Art:

[0003] For the anchor foundation of a long-span suspension bridge, the friction effect between the core concrete and the base rock is a very important research topic in bridge design. After the cable force is transmitted to the anchor, the vertical component force offsets part of the gravity, and the horizontal component force has a tendency to pull the foundation to move. This part of the force needs to be borne by the friction force at the bottom of the anchor foundation. Therefore, accurately measuring the friction coefficient of the anchor base is of great significance for guiding the design of bridge foundations.

[0004] Before the present invention, a patent (authorization number: CN 105547994 B) disclosed a method for measuring the friction coefficient of rock. After taking rock samples on-site, indoor rock triaxial tests were carried out. By applying different confining pressures and axial pressures to the rock samples, the actual working conditions were simulated, and the friction coefficients of different strata were measured. The friction coefficient data measured by this patent has good uniformity, but the process of taking rock samples is cumbersome. Especially for rocks under some high confining pressure conditions, the rock is prone to disintegration after unloading, and it is difficult to obtain a complete sample. For the anchor foundation, after the foundation pit excavation is completed, in order to obtain more accurate friction coefficient data, it is necessary to further explore in-situ testing techniques.

[0005] A patent (authorization number: CN 201508308 U) disclosed a computer pendulum friction coefficient tester, which measures the friction coefficient by the potential energy loss caused by the frictional resistance generated when the pendulum contacts the road surface under certain conditions. The rubber slip block at the end of the pendulum is used to rub against the asphalt road surface, and the test results are directly displayed digitally, with accurate, stable and reliable readings. This patent can simulate the friction between rubber and asphalt, but cannot set different overlying normal pressures and cannot simulate the friction between the anchor core concrete with a designed thickness and the base rock, and needs to be further improved.

[0006] A patent (authorization number: CN201269850 Y) disclosed a constant-pressure pendulum tester, which is provided with a force measuring sensor at the pendulum head at the top of the pendulum arm to measure the maximum positive pressure between the pendulum head and the road surface, and defines the starting detection conditions and the test process control, improving the objectivity, comparability and accuracy of the test results. This patent realizes the function of measuring the positive pressure between the test pendulum head and the road surface, but also cannot set different positive pressures and needs to be further improved.

[0007] Difficulty and Significance of Solving the Above Technical Problems:

[0008] Therefore, based on these problems, it is of great practical significance to provide a pendulum tester and a testing method for measuring the friction coefficient between concrete and rock, which can consider different overlying pressures and achieve rapid testing of the friction coefficient between concrete and rock. Summary of the Invention

[0009] The purpose of this application is to provide a pendulum tester and a testing method for measuring the friction coefficient between concrete and rock, which can consider different overlying pressures and achieve rapid testing of the friction coefficient between concrete and rock, so as to solve the technical problems in the prior art.

[0010] The technical solution adopted by the embodiments of this application to solve the technical problems existing in the well-known technology is:

[0011] A pendulum tester for measuring the friction coefficient between concrete and rock, the pendulum tester for measuring the friction coefficient between concrete and rock includes a test system and a control system. The test system includes a skid block and a concrete sliding plate, and the concrete sliding plate is fixed on the skid block with fixing screws; the control system includes an electromagnetic valve type hydraulic oil pump, and the positive pressure generated by the electromagnetic valve hydraulic oil pump is transmitted to the skid block through a hydraulic oil pipe and a spring.

[0012] The embodiments of this application can also adopt the following technical solutions:

[0013] In the above-mentioned pendulum tester for measuring the friction coefficient between concrete and rock, further, the concrete sliding plate rubs against the rock ground, and the edge position of the concrete sliding plate is arc-shaped.

[0014] Avoid damage when testing and contacting the ground.

[0015] In the above-mentioned pendulum tester for measuring the friction coefficient between concrete and rock, further, a pressure sensor is provided between the skid block and the concrete sliding plate.

[0016] The pressure sensor is used to measure the positive pressure between the concrete sliding plate and the rock ground when they are in contact, which is convenient for adjustment and control.

[0017] In the above-mentioned pendulum tester for measuring the friction coefficient between concrete and rock, further, the electromagnetic valve hydraulic oil pump is controlled by a control host, and the control host receives the positive pressure data from the pressure sensor.

[0018] A testing method for measuring the friction coefficient between concrete and rock, the testing method for measuring the friction coefficient between concrete and rock includes the following steps:

[0019] Step 1: Conduct tests at the bottom of the anchor foundation. If the formation is relatively uniform, select five flat and smooth measuring points; if the foundation involves multiple formations, then select five measuring points in each formation;

[0020] Step 2: Place the instrument on the measuring point and turn the leveling bolt to center the spirit level bubble; loosen the upper fastening handle and the lower fastening handle, turn the lifting handle to raise the pendulum so that it can swing freely, and then tighten the upper fastening handle and the lower fastening handle; move the pendulum to the right, press the release switch so that the snap ring on the pendulum enters the switch slot, release the release switch, the pendulum will be in a horizontal position, and lift the pointer to be parallel to the pendulum rod; press the release switch so that the pendulum drives the pointer to swing to the left. When the pendulum reaches the highest position and then falls, catch the pendulum rod with your hand. At this time, the pointer should point to zero; if it does not point to zero, slightly tighten or loosen the adjusting nut of the pendulum and repeat this operation until the pointer points to zero. The allowable zero adjustment error is ±1 BPN;

[0021] Step 3: Let the pendulum hang naturally. Loosen the upper fastening handle and the lower fastening handle, turn the lifting handle to lower the pendulum; at the same time, lift the lifting handle to move the pendulum to the left, and then lower the lifting handle so that the lower edge of the concrete slide gently touches the ground. Place the sliding length scale close to the concrete slide so that the left end of the scale aligns with the lower edge of the concrete slide; then lift the lifting handle to move the pendulum to the right, and then lower the lifting handle so that the lower edge of the concrete slide gently touches the ground. Check that the lower edge of the concrete slide should be flush with the right end of the sliding length scale; if it is flush, it means that the distance between the two touches of the concrete slide meets the 126 mm requirement; if it is not flush, raise or lower the height of the pendulum or the instrument base, and pay attention to keeping the spirit level bubble centered. Repeat the above actions until the sliding length meets the 126 mm requirement;

[0022] Step 4: Fix the pendulum on the right cantilever so that the pendulum is in the horizontal release position, and move the pointer to the right end to be parallel to the pendulum rod; use a brush to remove the loose particles and debris on the rock surface within the swinging range, sprinkle water on the rock surface to wash away the mud; turn on the control host, provide positive pressure to the concrete slide through the solenoid valve type hydraulic oil pump, hydraulic oil pipe, and sliding block to the design value, and then press the release switch to make the pendulum move and contact and slide on the rock surface. Use the pressure sensor to record the normal stress when the concrete slide rubs against the rock. When the pendulum falls back, catch it with your hand, and then place the pendulum rod and the pointer back to the horizontal release position;

[0023] Conduct the test processes of Step 2 to Step 4 at five measuring points within a single stratigraphic unit, and record the pendulum values measured each time; the difference between the maximum value and the minimum value among the 5 values measured at a single point shall not be greater than 3. If the difference is greater than 3, check the reasons and repeat the above operations again until they meet the requirements.

[0024] In the above test method for measuring the friction coefficient between concrete and rock, further, after the said Step 4, there are the following steps:

[0025] Step 5: Measure the temperature of the rock surface with a rock surface thermometer at the measuring point positions, accurate to 1°C. When the rock ground temperature is t (°C), the measured skid value is BPN t It is necessary to convert it to the skid value BPN at the standard temperature of 20°C 20 , BPN 20 = BPN t + △BPN, where △BPN is taken according to the following table;

[0026] Temperature correction value

[0027] Temperature (°C) 0 5 10 15 20 25 30 35 40 Temperature correction value △BPN -6 -4 -3 -1 0 +2 +3 +5 +7

[0028] The average value of five measurement readings at each measuring point represents the skid value of the measuring point, and the average value of the skid values of five measuring points represents the skid value of the test site; the skid value reading is divided by 100 to obtain the friction coefficient;

[0029] Step 6: If there is variability in the site, conduct the above tests in each geological unit. After measuring the friction coefficients of each geological unit, calculate the weights according to the area proportion of the geological unit and perform weighted averaging to obtain the comprehensive friction coefficient as the design basis.

[0030] One or more technical solutions provided in the embodiments of the present application have at least the following beneficial effects:

[0031] 1. The present invention is mainly used for quickly testing the friction coefficient between the core concrete of the suspension bridge anchor block and the base rock with different designed thicknesses. It uses a concrete sliding plate with variable pressure to rub against the bedrock, and uses a control host to operate a solenoid valve type hydraulic oil pump to pressurize the hydraulic oil pipe. The pressure acts on the skid block and the concrete sliding plate to provide a normal pressure consistent with the on-site working conditions when the concrete sliding plate contacts the rock. Different from the constant pressure pendulum tester in the prior art, it can realize the test of the sliding friction coefficient between concrete and rock under different normal pressures, and can realize the measurement of the friction coefficient between the core concrete of the suspension bridge anchor block with different designed thicknesses and the base rock.

[0032] 2. The working principle of the equipment of the present invention is clear and the operation is simple. After entering the site, the test can be quickly carried out, which has important practical significance for realizing the accurate measurement of the friction coefficient of the anchor block base. Description of the Drawings

[0033] The technical solutions of the embodiments of the present application will be further described in detail below with reference to the drawings. However, it should be noted that these drawings are only designed for explanatory purposes and therefore do not limit the scope of the present application. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0034] Figure 1Schematic diagram of the pendulum instrument structure for measuring the friction coefficient between concrete and rock in the present invention;

[0035] Figure 2 Schematic diagram of the slider structure of the present invention;

[0036] Figure 3 Structure diagram of the connection between the hydraulic oil pipe and the slider of the present invention.

[0037] In the figure:

[0038] 1 is the upper fastening handle; 2 is the lower fastening handle; 3 is the lifting handle; 4 is the release switch; 5 is the steering knuckle screw cap; 6 is the adjusting nut; 7 is the needle spring piece; 8 is the pointer; 9 is the connecting nut; 10 is the leveling bolt; 11 is the base; 12 is the cushion block; 13 is the spirit level; 14 is the snap ring; 15 is the positioning screw; 16 is the lifting handle; 17 is the balance weight; 18 is the tightening nut; 19 is the slider; 20 is the concrete sliding piece; 21 is the anti-slip screw; 22 is the handle; 23 is the hydraulic oil pipe; 24 is the solenoid valve type hydraulic oil pump; 25 is the control host; 26 is the fixing screw; 27 is the pressure sensor; 28 is the spring. Detailed implementation mode

[0039] In order to better understand the above technical solution, the above technical solution will be described in detail below in combination with the specification drawings and specific implementation modes.

[0040] Example 1

[0041] A pendulum instrument for measuring the friction coefficient between concrete and rock, the pendulum instrument for measuring the friction coefficient between concrete and rock includes a test system and a control system, the test system includes a slider and a concrete sliding piece, and the concrete sliding piece is fixed on the slider with fixing screws; the control system includes a solenoid valve type hydraulic oil pump, and the positive pressure generated by the solenoid valve hydraulic oil pump is transmitted to the slider through the hydraulic oil pipe and the spring. The concrete sliding piece rubs against the rock ground, and the edge position of the concrete sliding piece is arc-shaped. A pressure sensor is arranged between the slider and the concrete sliding piece. The solenoid valve hydraulic oil pump is controlled by the control host, and the control host receives the positive pressure data from the pressure sensor.

[0042] Example 2

[0043] A pendulum instrument for measuring the friction coefficient between concrete and rock mainly consists of two parts: a test system and a control system.

[0044] The described test system is the main part of the pendulum tester, including an upper fastening handle 1, a lower fastening handle 2, a lifting handle 3, a release switch 4, a knuckle cover 5; an adjusting nut 6, a needle spring piece 7, a pointer 8, a connecting nut 9, a leveling bolt 10, a base 11, a cushion block 12, a spirit level 13, a snap ring 14, a positioning screw 15, a lifting handle 16, a balance weight 17, a locking nut 18, a sliding block 19, a concrete sliding piece 20, an anti-slip screw 21, a handle 22, a hydraulic oil pipe 23, a fixing screw 26, a pressure sensor 27 and a spring 28.

[0045] The upper fastening handle 1, the lower fastening handle 2 and the lifting handle 3 are used to adjust and fix the height of the pendulum up and down; the release switch 4 is connected to the snap ring 14 and is used to release the pendulum so that the pendulum swings downward from the highest horizontal position; the knuckle cover 5 is used to fix the pendulum, and the adjusting nut 6 is used to adjust the initial value of the pointer 8 to 0; the scale corresponding to the pointer 8 is the pendulum value, and the friction coefficient can be obtained after correction and conversion; the needle spring piece 7 is located below the adjusting nut 6 and serves as a buffer pad; the connecting nut 9 is used to connect the knuckle cover 5 and the pendulum. The leveling bolt 10 is used to adjust the level of the base 11. When the base 11 is level, the spirit level 13 is in the centered position; the base 11 plays a role in leveling and supporting the instrument. The cushion block 12 is located at the bottom of the base 11 and plays a certain buffering role during instrument operation. The snap ring 14 is used to connect to the release switch 4 and is used to keep the pendulum in the horizontal position before testing. The positioning screw 15 is used to calibrate the pendulum tester and shall not be rotated without permission after calibration. The lifting handle 16 is used to lift the lifting handle 16 when the concrete sliding piece 20 just touches the ground, so that the concrete sliding piece 20 is lifted and the pendulum moves to the right. The balance weight 17 is used to adjust the moment balance of the instrument in the front-back and left-right directions. The locking nut 18 is used to prevent the balance weight 17 from loosening due to fatigue during rotation or vibration when contacting the ground.

[0046] The described sliding block 19 is composed of a concrete sliding piece 20, a fixing screw 26 and a pressure sensor 27. The concrete sliding piece 20 rubs against the rock ground, and its corner positions are arc-shaped to avoid damage when testing and contacting the ground; the concrete sliding piece is fixed on the sliding block 19 with the fixing screw 26, and the pressure sensor 27 is used to measure the normal pressure between the concrete sliding piece 20 and the rock ground when they are in contact, so as to facilitate adjustment and control.

[0047] The anti-slip screw 21 is used to adjust the distance between the end of the concrete sliding piece 20 and the swing center to 508 mm to meet the instrument requirements. The handle 22 is used to lift, transfer and place the pendulum tester.

[0048] The described control system is the test control part of the pendulum tester, including a hydraulic oil pipe 23, a solenoid valve type hydraulic oil pump 24, and a control host 25. The positive pressure generated by the solenoid valve hydraulic oil pump 24 is transmitted to the sliding block 19 through the hydraulic oil pipe 23 and the spring 28, so that the sliding block 19 has a stable positive pressure when it slides in contact with the ground. The control host 25 controls the solenoid valve hydraulic oil pump 24 to apply a positive pressure to the sliding block 19 and receives the positive pressure data from the pressure sensor 27 for easy adjustment and control.

[0049] Embodiment 3

[0050] This invention patent also relates to a test method for a pendulum tester used to measure the friction coefficient between concrete and rock, which includes the following steps:

[0051] Step 1: Select measurement points

[0052] Conduct tests at the bottom of the anchor foundation. If the formation is relatively uniform, select five flat and smooth measurement points; if the foundation involves multiple formations, select five measurement points in each formation.

[0053] Step 2: Level and zero the instrument

[0054] Place the instrument on the measurement point and turn the leveling bolt 10 to center the spirit level 13. Loosen the upper fastening handle 1 and the lower fastening handle 2, turn the lifting handle 3 to raise the pendulum so that it can swing freely, and then tighten the upper fastening handle 1 and the lower fastening handle 2. Move the pendulum to the right, press the release switch 4 so that the snap ring 14 on the pendulum enters the switch groove, release the release switch 4, the pendulum will be in a horizontal position, and lift the pointer 8 to be parallel to the pendulum rod. Press the release switch 4 to make the pendulum drive the pointer 8 to swing to the left. When the pendulum reaches the highest position and then falls, catch the pendulum rod with your hand. At this time, the pointer 8 should point to zero. If it does not point to zero, slightly tighten or loosen the adjustment nut 6 of the pendulum and repeat this operation until the pointer 8 points to zero. The allowable zeroing error is ±1 BPN.

[0055] Step 3: Calibrate the sliding length

[0056] (1) Let the pendulum be in a natural hanging state, loosen the upper fastening handle 1 and the lower fastening handle 2, and turn the lifting handle 3 to lower the pendulum. At the same time, lift the lifting handle 16 to move the pendulum to the left, then lower the lifting handle 16 so that the lower edge of the concrete sliding plate 20 gently touches the ground. Place the sliding length measuring scale closely to the concrete sliding plate 20 so that the left end of the scale aligns with the lower edge of the concrete sliding plate 20; then lift the lifting handle 16 to move the pendulum to the right, and then lower the lifting handle 16 so that the lower edge of the concrete sliding plate 20 gently touches the ground, and check that the lower edge of the concrete sliding plate 20 should be flush with the right end of the sliding length measuring scale.

[0057] (2) If it is flush, it means that the distance between the two touches of the concrete sliding plate 20 meets the requirement of 126 mm.

[0058] (3) If it is not flush, raise or lower the height of the pendulum or the instrument base 11, and pay attention to keeping the bubble level centered. Repeat the above actions until the sliding length meets the requirement of 126 mm.

[0059] Step Four: Testing

[0060] (1) Fix the pendulum on the right cantilever, make the pendulum in the horizontal release position, and move the pointer 8 to the right end parallel to the pendulum rod.

[0061] (2) Use a brush to remove loose particles and debris on the rock surface within the swinging range, sprinkle water on the rock surface, and wash away the mud.

[0062] (3) Turn on the control host 25, provide positive pressure to the concrete sliding piece 20 through the solenoid valve type hydraulic oil pump 24, hydraulic oil pipe 23, and sliding block 19 to the design value. Then press the release switch 4 to make the pendulum move and slide in contact with the rock surface. Use the pressure sensor 27 to record the normal stress when the concrete sliding piece 20 rubs against the rock. When the pendulum falls back, catch it by hand, and then place the pendulum rod and the pointer 8 back to the horizontal release position.

[0063] (4) Conduct tests at five measuring points within a single stratigraphic unit respectively, and record the pendulum values measured each time. The difference between the maximum value and the minimum value among the five values measured at a single point shall not be greater than 3. If the difference is greater than 3, check the reasons and repeat the above operations again until it meets the requirements.

[0064] (5) Measure the temperature of the rock surface at the measuring point position with a rock surface thermometer, accurate to 1 °C. When the temperature of the rock ground is t (°C), the measured pendulum value is BPN t The pendulum value BPN needs to be converted to the pendulum value BPN at the standard temperature of 20 °C 20 , BPN 20 = BPN t + △BPN, where △BPN is taken according to the following table.

[0065] Table Temperature Correction Value

[0066] Temperature (°C) 0 5 10 15 20 25 30 35 40 Temperature correction value △BPN -6 -4 -3 -1 0 +2 +3 +5 +7

[0067] (6) Use the average value of five measurement readings at each measuring point to represent the pendulum value of the measuring point, and use the average value of the pendulum values of the five measuring points to represent the pendulum value of the test site; divide the pendulum value reading by 100 to obtain the friction coefficient. If there is variability in the site, conduct the above tests in each geological unit. After obtaining the friction coefficients of each geological unit, calculate the weights according to the area ratio of the geological units and perform weighted averaging to obtain the comprehensive friction coefficient as the design basis.

[0068] The technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0069] In this embodiment, a variable-pressure concrete sliding block is used to friction with the bedrock; a solenoid valve is used to control the oil circuit to supply oil to the oil bladder, providing a positive pressure that conforms to the on-site working conditions when the concrete sliding block contacts the rock. Different from the constant-pressure pendulum tester in the prior art, it can realize the test of the sliding friction coefficient between concrete and rock under different positive pressures, and can realize the determination of the friction coefficient between the core concrete of the suspension bridge anchor and the base rock with different designed thicknesses.

[0070] In summary, the present invention provides a pendulum tester and a test method for measuring the friction coefficient between concrete and rock, which can consider different overlying pressures and realize the rapid test of the friction coefficient between concrete and rock.

[0071] The above embodiments have described the present invention in detail, but the described content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application shall still fall within the scope covered by the patent of the present invention.

Claims

1. A pendulum tester for measuring the friction coefficient between concrete and rock, characterized in that: The pendulum tester for measuring the friction coefficient between concrete and rock includes a test system and a control system. The test system includes a skid block and a concrete slide plate, and the concrete slide plate is fixed on the skid block with fixing screws. The control system includes a solenoid valve type hydraulic oil pump. The positive pressure generated by the solenoid valve hydraulic oil pump is transmitted to the skid block through a hydraulic oil pipe and a spring, and the concrete slide plate with variable pressure is used to friction with the bedrock. The concrete slide plate frictions with the rock ground, and the corners of the concrete slide plate are arc-shaped. A pressure sensor is arranged between the skid block and the concrete slide plate. When the pendulum arm swings from the horizontal to just touching the ground, the spring pressure is constant at this time, and the stable positive pressure is provided by the solenoid valve hydraulic oil pump. When the pendulum arm swings from just touching the ground to the vertical position, since the ground is flat, the swing radius gradually decreases, the spring is further compressed, and the hydraulic oil pump increases on the basis of the provided stable positive pressure, and the increased value is the pressure increased by the further compression of the spring. When the pendulum arm swings from the vertical to leaving the ground, the swing radius gradually increases, the spring elongates, and the pressure provided by the hydraulic oil pump decreases, and the decreased value is the pressure decreased by the spring release. Until leaving the ground, it decreases to the stable positive pressure.

2. The pendulum instrument for measuring the friction coefficient between concrete and rock according to claim 1, characterized in that: The solenoid valve hydraulic oil pump is controlled by a control host, and the control host receives the positive pressure data from the pressure sensor.

3. A test method for measuring the friction coefficient between concrete and rock, characterized in that: The test method for measuring the friction coefficient between concrete and rock includes the following steps: Step 1: Conduct tests at the bottom of the anchor foundation. If the formation is relatively uniform, select five smooth and flat measuring points; if the base involves multiple formations, select five measuring points in each formation. Step 2: Place the instrument on the measuring point and turn the leveling bolt to make the spirit level bubble centered. Loosen the upper fastening handle and the lower fastening handle, turn the lifting handle to raise the pendulum and make it swing freely, and then tighten the upper fastening handle and the lower fastening handle. Move the pendulum to the right, press the release switch to make the snap ring on the pendulum enter the switch groove, release the release switch, the pendulum is in the horizontal position, and lift the pointer to be parallel to the pendulum rod. Press the release switch to make the pendulum drive the pointer to swing to the left. When the pendulum reaches the highest position and then falls, catch the pendulum rod with your hand. At this time, the pointer should point to zero. If it does not point to zero, slightly tighten or loosen the adjusting nut of the pendulum and repeat this operation until the pointer points to zero. The allowable zero adjustment error is ±1 BPN. Step 3: Let the pendulum be in the natural hanging state, loosen the upper fastening handle and the lower fastening handle, turn the lifting handle to lower the pendulum. At the same time, lift the lifting handle to move the pendulum to the left, and then lower the lifting handle to gently touch the ground with the lower edge of the concrete slide plate. Place the sliding length scale closely beside the concrete slide plate so that the left end of the scale aligns with the lower edge of the concrete slide plate. Then lift the lifting handle to move the pendulum to the right, and then lower the lifting handle to gently touch the ground with the lower edge of the concrete slide plate, and check that the lower edge of the concrete slide plate should be flush with the right end of the sliding length scale. If it is flush, it means that the distance between the two touches of the concrete slide plate meets the 126 mm requirement. If it is not flush, raise or lower the height of the pendulum or the instrument base, and pay attention to keeping the spirit level bubble centered. Repeat the above actions until the sliding length meets the 126 mm requirement. Step 4: Fix the pendulum on the right cantilever, place the pendulum at the horizontal release position, and turn the pointer to the right end parallel to the pendulum rod; use a brush to remove loose particles and debris on the rock surface within the swinging range, sprinkle water on the rock surface to wash away the mud; turn on the control host, provide positive pressure to the concrete slide by means of a solenoid valve type hydraulic oil pump, hydraulic oil pipe, and sliding block to the design value, then press the release switch to make the pendulum move and contact and slide on the rock surface, use a pressure sensor to record the normal stress when the concrete slide rubs against the rock, when the pendulum falls back, catch it by hand, and then place the pendulum rod and pointer back at the horizontal release position; Carry out the test processes of Step 2 to Step 4 at five measuring points within a single stratigraphic unit respectively, and record the pendulum values measured each time; the difference between the maximum value and the minimum value among the 5 values measured at a single point shall not be greater than 3. If the difference is greater than 3, the reasons shall be checked and the above operations shall be repeated until the requirements are met.

4. The test method for measuring the friction coefficient between concrete and rock according to claim 3, characterized in that: There are the following steps after the said Step 4: Step 5: Measure the temperature of the rock surface with a rock surface thermometer at the measuring point position, accurate to 1 °C. When the ground temperature of the rock is t (°C), the measured pendulum value is BPN t The pendulum value BPN needs to be converted to the pendulum value at the standard temperature of 20 °C 20 , BPN 20 = BPN t + △BPN, where △BPN is taken according to the following table; Temperature correction value The average value of five measurement readings at each measuring point represents the pendulum value of the measuring point, and the average value of the pendulum values of the five measuring points represents the pendulum value of the test site; the pendulum value reading divided by 100 is the friction coefficient; Step 6: If there is variability in the site, conduct the above tests in each geological unit. After obtaining the friction coefficients of each geological unit, calculate the weights according to the area proportion of the geological units and perform weighted averaging to obtain the comprehensive friction coefficient as the design basis.

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