An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile

Abstract

The present invention discloses a test device for measuring the critical water pressure of overturning of a cantilever retaining water baffle pile, which includes a test box body and two lifting platforms arranged on the test box body. Fixed pulleys corresponding to the pull ropes are provided on the lifting platforms. A number of acrylic plates are assembled on both sides of the inner wall of the test box body. Corner devices are provided on both sides of the test box body. The bottom of the corner device is connected to the test box body, and the top is connected to the corner device. A wooden board is provided on one side of the corner device. Two load-bearing guide rails are provided on the wooden board. One end of the load-bearing guide rail is fixed to the wooden board by bolts, and the other end is connected to a push plate. Pull rings are connected to both ends of the push plate. A pressure sensor is connected to the middle of the push plate. One end of a pull rope is wound around the pull ring. The device of the present invention obtains data that originally required more complex test conditions by a simpler method according to the principle of hydrostatic pressure distribution in hydraulics.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring the critical water pressure test for the overturning of cantilever retaining sheet piles, and specifically to a device for measuring the critical water pressure test for the overturning of cantilever retaining sheet piles. Background Technique

[0002] Dike structures have played an active role in dealing with floods. The main failure modes of dikes are overtopping, bank collapse, and piping. According to historical records of dike failure modes, the proportion of overtopping failure is the highest compared to other modes. And retaining structures are a common choice. In recent years, materials such as plastic steel and FRP are gradually being used as protective materials for dikes and revetments due to their advantages of light weight, high strength, corrosion resistance, and environmental protection. They usually adopt the form of assembled sheet piles and are pressed into the soil by a pile driver to form a cantilever retaining wall structure. Facing the lateral loading of water pressure, the critical water head at which the sheet pile becomes unstable under specific foundation conditions and the soil deformation around it are crucial for understanding the pile-soil interaction. This is of guiding significance for the design of the sheet pile penetration depth. Physical experiments are difficult to deeply study the mesoscopic behavior of soil, and the discrete element method (DEM), as a numerical simulation method, has significant advantages in studying the mesoscopic mechanics and movement laws of granular materials, so it is suitable for studying pile-soil interaction. However, the mesoscopic parameters of the foundation soil in DEM need to be calibrated based on the macroscopic mechanical indexes and phenomena of physical experiments. Generally, the mesoscopic parameters of foundation soil are calibrated according to triaxial compression tests or direct shear tests, but the accuracy of the results obtained by DEM in studying pile-soil interaction cannot be verified by this indirect calibration method. Therefore, a device for measuring the critical water pressure test for the overturning of cantilever retaining sheet piles is designed. This device measures the critical instability water pressure by measuring the change in the inclination angle of the sheet pile during the gradual loading of water pressure. During each stage of loading, the inclination angle of the sheet pile will converge or diverge. When the inclination angle diverges, the current water pressure can be considered as the critical instability water pressure. During the test process, the magnitude F of each stage of loading force, the duration T of its loading, and the data of the change in the inclination angle θ are recorded. It is also necessary to take pictures of the soil state at each stage of the sheet pile overturning process. All these data will be used for calibrating the mesoscopic parameters of the DEM soil. For this reason, we propose a device for measuring the critical water pressure test for the overturning of cantilever retaining sheet piles with higher practicability. Summary of the Invention

[0003] The purpose of the present invention is to provide a device for measuring the critical water pressure test for the overturning of cantilever retaining sheet piles, which solves the existing problems.

[0004] To achieve the above object, the present invention provides the following technical solution: A test device for measuring the overturning critical water pressure of a cantilever retaining sheet pile, comprising a test box body, and two lifting platforms arranged on the test box body. Fixed pulleys corresponding to the pulling ropes are provided on the lifting platforms. A number of acrylic plates are assembled on both sides of the inner wall of the test box body. Corner deflectors are provided on both sides of the test box body. The bottom of the corner deflector is connected to the test box body. A wooden board is provided on one side of the corner deflector. Two load-bearing guide rails are provided on the wooden board. One end of the load-bearing guide rail is fixed to the wooden board by bolts, and the other end is connected to a push plate. Pulling rings are connected to both ends of the push plate. A pressure sensor is connected to the middle of the push plate. One end of a pulling rope is wound around the pulling ring. The other end of the pulling rope bypasses the fixed pulley and is connected to a placing plate. A number of counterweight blocks are provided on the placing plate.

[0005] Preferably, the corner deflector is connected to an arm plate, and the arm plate and the wooden board are fixedly connected by bolts.

[0006] Preferably, one end of the wooden board is fixedly connected to the load-bearing guide rail by bolts, and the other end is fixedly connected to the push plate by bolts.

[0007] Preferably, the push plate is fixedly connected to the pulling ring. One end of the pulling rope is fastened to the pulling ring, and the other end is fixedly connected to the placing plate after bypassing the fixed pulley.

[0008] Preferably, the lifting platform is connected to the fixed pulley.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] The device of the present invention obtains the data that originally required more complex test conditions by a simpler method according to the principle of hydrostatic pressure distribution in hydraulics. If real water is used for loading, the required space size, the number of instruments and the operation difficulty of the test will all increase significantly, resulting in high costs. Therefore, the device of the present invention is economical and efficient for measuring the overturning critical water pressure of a cantilever retaining sheet pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic structural diagram of the present invention;

[0012] Figure 2 It is a schematic structural diagram of the push plate of the present invention;

[0013] Figure 3 It is a schematic structural diagram of the placing plate of the present invention;

[0014] Figure 4 It is a schematic diagram of the uniformly distributed load and concentrated force of the present invention;

[0015] Figure 5 It is a schematic structural diagram of the height setting of the pressure sensor of the device of the present invention;

[0016] Figure 6 This is a schematic diagram of the layout structure of the baffle of the present invention.

[0017] In the figure: test box body 1, acrylic plate 2, corner device 3, arm plate 4, wooden board 5, load-bearing guide rail 6, push plate 7, pressure sensor 8, pull ring 9, pull rope 10, lifting platform 11, fixed pulley 12, storage plate 13, counterweight 14. Specific embodiments

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0019] Embodiment 1

[0020] As Figure 1 、 Figure 2 and Figure 3 shown, a test device for measuring the critical water pressure of the overturning of a cantilevered water retaining sheet pile includes a test box body 1 and two lifting platforms 11 arranged on the test box body 1. Fixed pulleys 12 corresponding to the pull rope 10 are provided on the lifting platforms 11, and the lifting platforms 11 are connected to the fixed pulleys 12. A number of acrylic plates 2 are assembled on both sides of the inner wall of the test box body 1. Corner devices 3 are provided on both sides of the test box body 1. The bottom of the corner device 3 is connected to the test box body 1. A wooden board 5 is provided on one side of the corner device 3. The corner device 3 is connected to the arm plate 4, and the arm plate 4 and the wooden board 5 are fixedly connected by bolts. Two load-bearing guide rails 6 are provided on the wooden board 5. One end of the load-bearing guide rail 6 is fixedly bolted to the wooden board 5, and the other end is connected to a push plate 7. One end of the wooden board 5 and the load-bearing guide rail 6 are fixedly connected by bolts, and the other end is fixedly connected to the push plate 7 by bolts. Pull rings 9 are connected to both ends of the push plate 7, and a pressure sensor 8 is connected to the middle of the push plate 7. One end of the pull rope 10 is wound around the pull ring 9, and the other end of the pull rope 10 passes around the fixed pulley 12 and is connected to a storage plate 13. The push plate 7 is fixedly connected to the pull ring 9. One end of the pull rope 10 is tied to the pull ring 9, and the other end passes around the fixed pulley 12 and is fixedly connected to the storage plate 13. A number of counterweights 14 are provided on the storage plate 13. Through the action of the corner device 3, the wooden board 5 can be pushed to rotate by the arm plate 4, and the height of the wooden board 5 can be adjusted, and the wooden board 5 can be adjusted to a suitable position. The load-bearing guide rail 6 on the wooden board 5 and the central axis of the pull rope 10 can be located on the same horizontal plane, and a number of counterweights 14 can be added to the storage plate 13. The counterweights 14 act on the storage plate 13 with gravity, and the storage plate 13 acts on the pull ring 9 and the push plate 7 with traction through the pull rope 10. The load-bearing guide rail 6 on the wooden board 5 provides support for the push plate 7, and restricts the movement trajectory and range of the push plate 7. And the pressure sensor 8 on the push plate 7 is used to measure the traction force applied by the baffle such as Figure 6 applied.

[0021] Specific implementation case two

[0022] 1. Preset position of the pressure sensor

[0023] The uniform load acting on the upstream side of the retaining wall by the upstream water level is simplified into a horizontal concentrated force in the physical test , The magnitude of which can be calculated by the following formula:

[0024] (1)

[0025] In the formula, is the length of the retaining wall, is the water density, ; is the gravity, 9.8 ; is the upstream water level height, with the direction perpendicular to the upstream side of the hydraulic structure and pointing downstream, and the acting point is at the midline of the upstream structural surface of the structure, from the bottom, and the initial is set to be the same height as the baffle protection height H, without considering the hydrostatic pressure on the upstream soil base surface;

[0026] When the initial water head increases step by step to , the acting point of the concentrated force can always be divided into the horizontal concentrated force of the triangular area a of the uniform load at the position from the bottom, and the horizontal concentrated force of the rectangular area of the uniform load at the position from the bottom, as shown in Figure 4 ; In this way, the height of the pressure sensor 8 is determined, as shown in Figure 5 ;

[0027] The magnitude of the force acting at the position is a fixed value. The initial hw is set to be the same height as the baffle protection height H and is calculated by the above formula 1; the magnitude of the force acting at the position is calculated by the following formula 2:

[0028] (2)

[0029] 2. Test methods and means

[0030] 21. Method for filling clay in the soil box

[0031] The clay is filled in layers, with a pre-filled height of 10 cm for each layer, and it reaches the required density after being compacted by a rammer until the height of 75 cm. The mass of each layer of soil is calculated by the following formula:

[0032]

[0033] In the formula: is the filling height of each layer, taking = 10 cm; is the designed dry density; is the length of the soil box, l = 1.2 m; is the width of the soil box, = 1.0 m.

[0034] 22. Concentrated load loading method

[0035] As Figure 6 shown, the concentrated load drives the pull rope 10 on the fixed pulley 12 by adding load, the vertical load becomes a horizontal pulling force, the pull rope 10 pulls the load-bearing guide rail 6, so that the pressure head equipped with the pressure sensor 8 acts horizontally on the baffle. When the protection height of the baffle is H, according to the theoretical basis for determining the acting position by the height of the pressure head described above, the positions are respectively marked as point A at H / 2 of the baffle height and point B at H / 3. The horizontal pressure magnitudes at the two acting points are obtained through the pressure sensors 8 at points A and B, and the magnitudes of the forces are calculated according to Formulas 1 and 2 described above; during step-by-step loading, the pressure duration for each level is kept at 10 min; after each level of loading, the acting angle between the pressure head and the sheet pile is adjusted by the angle adjuster 3 to keep them perpendicular. At this time, the lifting platform should also adjust the height so that the guide rail is collinear with the moving direction of the connecting pull rope.

[0036] 23. Baffle instability judgment method

[0037] During step-by-step loading, the inclination angle sensor on the baffle records data at all times. When the inclination angle data diverges, it is determined as instability, and the current water head level is recorded.

[0038] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile, comprising a test box body (1), and two lifting platforms (11) arranged on the test box body (1). A fixed pulley (12) corresponding to a pulling rope (10) is provided on the lifting platform (11). Characterized in that: On both sides of the inner wall of the test box body (1), a number of acrylic plates (2) are assembled. On both sides of the test box body (1), corner deflectors (3) are provided. The bottom of the corner deflector (3) is connected to the test box body (1). On one side of the corner deflector (3), a wooden board (5) is provided. On the wooden board (5), two load-bearing guide rails (6) are provided. One end of the load-bearing guide rail (6) is fixed to the wooden board (5) by bolts, and the other end is connected to a push plate (7). Both ends of the push plate (7) are connected with pull rings (9). A pressure sensor (8) is connected to the middle of the push plate (7). One end of a pulling rope (10) is wound around the pull ring (9), and the other end of the pulling rope (10) bypasses the fixed pulley (12) and is connected to a placement board (13). A number of counterweight blocks (14) are provided on the placement board (13). The concentrated load drives the pulling rope (10) on the fixed pulley (12) by adding load, and the vertical load becomes a horizontal pulling force. The pulling rope (10) pulls the load-bearing guide rail (6), so that the pressure head equipped with the pressure sensor (8) acts horizontally on the baffle. When the protection height of the baffle is H, and the heights of the loading pressure heads are determined to act at positions. Denote the height H / 2 of the baffle as point A and H / 3 as point B. The horizontal pressure magnitudes at the two acting points are obtained through the pressure sensors (8) at points A and B.

2. An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile according to claim 1, Characterized in that: The corner deflector (3) is connected to an arm plate (4), and the arm plate (4) and the wooden board (5) are fixedly connected by bolts.

3. An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile according to claim 1, Characterized in that: One end of the wooden board (5) and the load-bearing guide rail (6) are fixedly connected by bolts, and the other end is fixedly connected to the push plate (7) by bolts.

4. An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile according to claim 1, Characterized in that: The push plate (7) is fixedly connected to the pull ring (9). One end of the pulling rope (10) is fastened to the pull ring (9), and the other end is fixedly connected to the placement board (13) after bypassing the fixed pulley (12).

5. An experimental device for measuring the critical water pressure for the overturning of a cantilever retaining sheet pile according to claim 1, Characterized in that: The lifting platform (11) is connected to the fixed pulley (12).

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