A self-balancing concrete and rock friction coefficient measurement system and test method

Abstract

The present invention belongs to the technical field of bridge engineering, and in particular, relates to a self-balancing concrete and rock friction coefficient measuring system and testing method, wherein the self-balancing concrete and rock friction coefficient measuring system comprises two concrete blocks and a back pressure plate, wherein the two concrete blocks are connected by a horizontal jack, and the two concrete blocks support the back pressure plate, wherein the lower surface of the back pressure plate contacts a roller row, and the bottom of the vertical jack is placed on the back pressure plate, and the top of the vertical jack abuts against a force transfer block, and the force transfer block is fixed so that it abuts against the vertical jack. The present invention provides a self-balancing concrete and rock friction coefficient measuring system and testing method, which adopts a horizontal jack, offsets the reaction force through concrete self-balancing, applies positive pressure through a vertical jack and a vertical anchor rod, and does not require excavation of bedrock.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a self-balancing concrete and rock friction coefficient measuring system and a testing method. Background Art

[0002] Existing technology:

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

[0004] Prior to the present invention, an invention patent (grant number: CN105547994B) disclosed a method for measuring the friction coefficient of rock. After taking rock samples on site, the patent conducted an indoor triaxial test of rock. 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 rock sample sampling process is cumbersome, especially for some rocks under high confining pressure conditions. The rocks are prone to disintegration after unloading, and it is difficult to obtain complete samples. Indoor tests apply confining pressure and axial pressure, which also simulates the actual working conditions on site. This method is an indoor test method. Although indoor tests can also measure relatively uniform data, since the rocks are prone to disintegration after sampling, the test results are difficult to directly apply to engineering design.

[0005] For anchor foundations, after the excavation of the foundation pit is completed, in order to obtain more accurate friction coefficient data, it is necessary to further explore the in-situ testing technology. According to the "Engineering Geology Manual" (Fifth Edition), field tests mostly use on-site direct shear tests, using the flat push method, oblique push method or wedge method to carry out the test. However, in the above test methods, when the normal load is applied, a certain counterweight is generally required. When the horizontal thrust is applied, the site needs to be able to provide the reaction force of the jack. For the bedrock at the bottom of the anchor foundation, a working surface of a certain depth needs to be excavated for the jack, that is, the horizontal jack needs to be dug down, and there is a rock surface behind the pressure steel plate, which poses a construction difficulty.

[0006] The difficulty and significance of solving the above technical problems:

[0007] Therefore, based on these problems, it is of great practical significance to provide a self-balancing concrete and rock friction coefficient measurement system and test method that uses a horizontal jack to offset the reaction force through concrete self-balancing without the need to excavate the bedrock. Summary of the invention

[0008] The purpose of this application is to solve the technical problems in the prior art and to provide a self-balancing concrete and rock friction coefficient measurement system and test method that uses a horizontal jack to offset the reaction force through concrete self-balancing, and applies positive pressure through vertical jacks and vertical anchors, without the need to excavate bedrock.

[0009] The technical solution adopted by the embodiment of the present application to solve the technical problems existing in the known technology is:

[0010] A self-balancing concrete and rock friction coefficient measuring system, the self-balancing concrete and rock friction coefficient measuring system comprises two concrete blocks and a back pressure plate, the two concrete blocks are connected by a horizontal jack, the two concrete blocks support the back pressure plate, the lower surface of the back pressure plate is in contact with a roller row, the bottom of the vertical jack is placed on the back pressure plate, the top of the vertical jack is against the force transmission block, and the force transmission block is fixed so that it is against the vertical jack.

[0011] The embodiments of the present application may also adopt the following technical solutions:

[0012] In the above self-balancing concrete and rock friction coefficient measuring system, further, a pressure plate is laid on the upper surface of the concrete block, and the pressure plate is located between the concrete block and the roller row.

[0013] Make the force on the concrete block more even and avoid the concrete block being crushed and damaged when the roller row moves to both sides.

[0014] In the above self-balancing concrete and rock friction coefficient measuring system, further, both ends of the force transmission block are connected to the vertical anchor rod through steel strands, and the vertical anchor rod is fixed on the ground.

[0015] In the above self-balancing concrete and rock friction coefficient measuring system, further, pressure gauges are installed on the horizontal jack and the vertical jack.

[0016] In the above self-balancing concrete and rock friction coefficient measuring system, further, the strength of the concrete block is the same as the strength of the core-filled concrete in the anchor, and the height of the concrete block should not be less than 1 / 2 of the side length in the thrust direction.

[0017] In the above-mentioned self-balancing concrete and rock friction coefficient measuring system, further, the upper surface of the concrete block is covered with a pressure plate, the pressure plate is located between the concrete block and the roller row, the two ends of the force transmission block are connected to the vertical anchor rod through a steel strand, the vertical anchor rod is fixed on the ground, and pressure gauges are installed on the horizontal jack and the vertical jack.

[0018] A self-balancing concrete and rock friction coefficient testing method is disclosed, wherein the self-balancing concrete and rock friction coefficient testing method adopts any one of the self-balancing concrete and rock friction coefficient measuring systems described above.

[0019] A self-balancing concrete and rock friction coefficient testing method, the self-balancing concrete and rock friction coefficient testing method comprising the following steps:

[0020] Step 1: Cast concrete blocks on site. Before casting concrete blocks, the shear surface rock surface should be cleaned. After the concrete blocks are cast, they should be cured. Before testing, it should be confirmed that the concrete blocks have reached the designed strength.

[0021] Step 2: Install a horizontal jack between two concrete blocks, install a pressure plate, a roller row, a counter-pressure plate, a vertical jack, and a force transfer block on the top of the concrete block according to the self-balancing concrete and rock friction coefficient measurement system, and connect the other end of the steel strand to the force transfer block.

[0022] In the above self-balancing concrete and rock friction coefficient test method, further, the step 1 includes the following steps: leveling the foundation site and dividing the test area. Performing vertical anchor construction, and then connecting one end of the steel strand to the vertical anchor; the step 2 also includes applying lubricating oil to the side of the pressure plate in contact with the roller row.

[0023] To reduce the friction between the roller row and the pressure plate when it slides.

[0024] One or more technical solutions provided in the embodiments of the present application have at least the following beneficial effects:

[0025] 1. The present invention is mainly used for rapid testing of the friction coefficient between the rock and the core-filled concrete at the bottom of the anchor foundation of a suspension bridge. The vertical pull-out anchor rod is constructed on site. After the force is transmitted by the vertical jack, the pull-out force of the anchor rod is converted into the vertical pressure of the friction test system. The horizontal jack offsets the reaction force through the self-balancing of the concrete. There is no need to excavate the bedrock. The test process is economical and reliable, and the friction coefficient test can be carried out more conveniently at the bottom of the anchor foundation, which has certain promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The technical solutions of the embodiments of the present application will be further described in detail below in conjunction with the accompanying drawings, but it should be noted that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present application. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0027] Figure 1 This is a schematic diagram of the structure of Example 1 of the present invention.

[0028] In the figure:

[0029] 1. Concrete block, 2. Pressure plate, 3. Counter pressure plate, 4. Vertical jack, 5. Horizontal jack, 6. Vertical anchor rod, 7. Steel strand, 8. Roller row, 9. Pressure gauge, 10. Force transfer block. DETAILED DESCRIPTION

[0030] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Example 1

[0032] The self-balancing concrete and rock friction coefficient measuring system is mainly composed of a concrete block 1, a pressure plate 2, a counter-pressure plate 3, a vertical jack 4, a horizontal jack 5, a vertical anchor rod 6, a steel strand 7, a roller row 8, a pressure gauge 9, and a force transmission block 10.

[0033] Concrete block 1 is made of concrete of the same strength as the core concrete in the anchor and is cast on site. Before pouring concrete, the rock surface of the shear surface should be cleaned. The height of the concrete specimen should not be less than 1 / 2 of the side length in the thrust direction. After the specimen is cast, it should be cured. The concrete strength should be measured before the test. After confirming that the concrete has reached the design strength, the test should be carried out in a timely manner.

[0034] The use of concrete of the same strength is to make the on-site test as similar as possible to the actual working conditions. Concrete of different strengths still has different degrees of bonding with the bedrock.

[0035] The pressure plate 2 is made of stainless steel and is placed between the concrete block 1 and the roller row 8, so that the concrete block 1 is subjected to a more uniform force and the roller row 8 is prevented from rolling and damaging the concrete block 1 when it moves to both sides. The roller row 8 facilitates sliding. After the roller row 8 is installed, sliding will not generate friction on the pressure plate 2 and the concrete block 1. In this way, the friction under the normal stress is generated at the interface between the concrete and the rock.

[0036] The counter-pressure plate 3 is placed between the roller row 8 and the vertical jack 3 , and is used to evenly transfer the counter-pressure formed when the vertical jack 3 is hydraulically started to the pressure plate 2 and the concrete block 1 .

[0037] The vertical jack 4 moves upward, and the tension is borne by the vertical anchor rod 5 and the steel strand 6 after passing through the force transmission block 9, and the pressure is borne by the counter-pressure plate 3, the pressure plate 2 and the concrete block 1;

[0038] The horizontal jack 5 provides horizontal thrust, and both the thrust and the reaction force are borne by the concrete block 1, thus achieving self-balancing of the force;

[0039] The vertical anchor rod 6 is pre-drilled and buried in the rock foundation;

[0040] The pressure gauge 9 reflects the internal forces of the vertical jack 4 and the horizontal jack 5.

[0041] Now, the top of the pressure plate 2 is a roller row 8, which is smeared with lubricating oil, and the friction is very small and can be ignored.

[0042] Example 2

[0043] The self-balancing concrete-rock friction coefficient test method includes the following steps:

[0044] Step 1: Bring the equipment to the site, level the basic site, and divide the test area;

[0045] Step 2: construct the vertical anchor rod 6, and then connect one end of the steel strand 7 to the vertical anchor rod 6;

[0046] Step 3: Cast concrete blocks 1 on site. Before casting concrete blocks 1, the surface of the rock mass on the shear surface should be cleaned. After the specimen is cast, it should be cured. Before the test, it should be confirmed that the concrete reaches the designed strength. Then install the horizontal jack 5 between the two concrete blocks 1, install the pressure plate 2, roller row 8, counter pressure plate 3, vertical jack 4, and force transfer block 10 on the top of the concrete block 1, and finally connect the other end of the steel strand 7 to the force transfer block 10. The side of the pressure plate 2 in contact with the roller row 8 should be coated with lubricating oil to reduce the friction between the roller row 8 and the pressure plate 2 when sliding.

[0047] Step 4: Turn on the vertical jack 4 and apply the vertical load. The normal load should be applied in 1 to 3 levels, and the level can be determined according to the size of the normal stress and the rock properties. The loading is time-controlled, and one level of load should be applied every 5 minutes. After loading, the normal displacement under each level of load should be measured immediately, and measured again after 5 minutes, and the next level of load can be applied. After applying to the predetermined load, it should be measured every 5 minutes. When the difference between the normal displacements of two consecutive measurements is no more than 0.01mm, the horizontal load can be applied.

[0048] Step 5: Open the horizontal jack 5 and apply the horizontal load. Apply it in 8 to 12 levels according to the estimated maximum shear load. When the horizontal displacement caused by the applied load increases significantly, the horizontal load level can be appropriately increased. The horizontal load is time-controlled and applied at one level every 5 minutes. Each displacement meter should be read once before and after each level of load is applied. When it is close to shearing, the load change and the corresponding displacement should be closely observed and read. The load and displacement should be observed synchronously. After the concrete block 1 is sheared, the horizontal load should continue to be applied until a stable shear load value is measured.

[0049] Step 6: Slowly reduce the horizontal load to zero, observe the rebound of concrete block 1, and the test ends. During the load reduction process, the normal stress should still be kept constant.

[0050] Step 7: Organize the data and calculate the friction coefficient. Friction coefficient = horizontal thrust / vertical pressure.

[0051] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0052] In this embodiment, vertical pull-out anchor construction is carried out on site. After the force is transmitted by the vertical jack, the pull-out force of the anchor is converted into the vertical pressure of the friction test system. The horizontal jack offsets the reaction force through the self-balancing of the concrete. There is no need to excavate the bedrock. The test process is economical and reliable, and the friction coefficient test can be carried out more conveniently at the bottom of the anchor foundation.

[0053] In summary, the present invention provides a self-balancing concrete-rock friction coefficient measuring system and testing method which uses a horizontal jack to offset the reaction force through concrete self-balancing and does not require bedrock excavation.

[0054] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A self-balancing concrete and rock friction coefficient measurement system, characterized by: The self-balancing concrete and rock friction coefficient measuring system includes two concrete blocks and a back pressure plate. The two concrete blocks are connected by a horizontal jack. The horizontal jack provides horizontal thrust. The thrust and reaction force are both borne by the concrete blocks, thereby achieving self-balancing of the force. The two concrete blocks support the back pressure plate. The lower surface of the back pressure plate is in contact with the roller row. The bottom of the vertical jack is placed on the back pressure plate. The top of the vertical jack is against the force transmission block. The force transmission block is fixed so that it is against the vertical jack. Both ends of the force transmission block are connected to the vertical anchor rod through steel strands, and the vertical anchor rod is fixed on the ground.

2. The self-balancing concrete and rock friction coefficient measuring system according to claim 1 is characterized in that: The upper surface of the concrete block is paved with a pressure plate, and the pressure plate is located between the concrete block and the roller row.

3. The self-balancing concrete and rock friction coefficient measuring system according to claim 1 is characterized in that: Pressure gauges are installed on the horizontal jack and the vertical jack.

4. The self-balancing concrete and rock friction coefficient measuring system according to claim 1, characterized in that: The strength of the concrete block is the same as that of the core-filled concrete in the anchor, and the height of the concrete block should not be less than 1 / 2 of the side length in the thrust direction.

5. The self-balancing concrete and rock friction coefficient measuring system according to claim 1 is characterized in that: The upper surface of the concrete block is paved with a pressure plate, which is located between the concrete block and the roller row. Both ends of the force transmission block are connected to vertical anchor rods through steel strands. The vertical anchor rods are fixed on the ground. Pressure gauges are installed on the horizontal jack and the vertical jack.

6. A self-balancing concrete and rock friction coefficient test method, characterized in that: The self-balancing concrete and rock friction coefficient testing method adopts the self-balancing concrete and rock friction coefficient measuring system described in any one of claims 1-5.

7. A self-balancing concrete and rock friction coefficient test method, characterized in that: The self-balancing concrete and rock friction coefficient testing method comprises the following steps: Step 1: Cast concrete blocks on site. Before casting concrete blocks, the shear surface rock surface should be cleaned. After the concrete blocks are cast, they should be cured. Before testing, it should be confirmed that the concrete blocks have reached the designed strength. Step 2: Install a horizontal jack between two concrete blocks, install a pressure plate, a roller row, a counter-pressure plate, a vertical jack, and a force transfer block on the top of the concrete block according to the self-balancing concrete and rock friction coefficient measurement system described in any one of claims 1 to 5, and connect the other end of the steel strand to the force transfer block.

8. The self-balancing concrete-rock friction coefficient testing method according to claim 7, characterized in that: The steps before step one include: leveling the foundation site and dividing the test area; constructing vertical anchor rods, and then connecting one end of the steel strand to the vertical anchor rod; step two also includes applying lubricating oil to the side of the pressure plate in contact with the roller row.

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