Device for testing vertical foundation bed coefficient through test pit

Abstract

The utility model provides a device for testing the coefficient of a vertical foundation bed in a test pit, which comprises a bearing plate, two reference piles are arranged on two sides of the bearing plate in the test pit at intervals, a reference beam is horizontally arranged on the reference piles, a jack is further arranged at the central position of the bearing plate, and the jack is arranged on the bearing plate. Two displacement measuring instruments are symmetrically arranged on the two sides of the jack on the bearing plate, the measuring ends of the displacement measuring instruments are in close contact with the datum line beam, the base ends of the displacement measuring instruments are fixed on the bearing plate, a force transmission device is arranged above the jack, the force transmission device is connected with a counter-force plate through a counter-force transmission arm, and the counter-force plate is matched with the inner wall surface of the test pit. The defects that in the prior art, the tested stratum depth is limited, and test data are inaccurate due to the influences of the test depth, ground loading and the like can be overcome.

Description

Technical Field

[0001] The utility model relates to the technical field of geotechnical engineering, in particular to a device for testing a vertical base bed coefficient in a test pit. Background Art

[0002] The foundation soil base coefficient (also known as the Winkel coefficient) is the proportional coefficient of the displacement increasing with the load value when the Winkel hypothesis is used to describe the stress and deformation characteristics of the stratum. It is divided into horizontal base coefficient and vertical base coefficient according to the direction of force, which respectively reflect the pressure required for the foundation soil to produce unit deformation under horizontal and vertical external forces.

[0003] The subgrade coefficient, a crucial geotechnical engineering parameter, is widely used in foundation and structural design for buildings, municipal engineering, underground projects, highways, and airports. It is primarily used to simulate the interaction between subgrade and structure and calculate the internal forces and displacements of structures. The appropriateness of the subgrade coefficient directly impacts the accuracy of the internal force and displacement calculations, is closely related to structural safety, and significantly influences construction project costs.

[0004] The size of the foundation soil subgrade coefficient is closely related to factors such as soil type, foundation depth, base area, base shape, foundation stiffness and load duration. Therefore, it is very important to obtain accurate foundation soil subgrade coefficient through scientific means. According to the current relevant specifications and standards in my country, the on-site in-situ test of foundation soil subgrade coefficient adopts K 30 The flat plate load test is carried out by using a rigid bearing plate with a diameter of 30 cm and a thickness greater than or equal to 20 mm to determine the base bed coefficient of the foundation soil.

[0005] In the use of K 30 When the vertical bed coefficient of deep foundation soil is determined by plate load test, the traditional test method is to transfer the applied load on the ground to the deep K through the force transfer column. 30 However, the following problems exist in the actual test process, which makes it difficult to obtain accurate deep vertical bed coefficient test results:

[0006] First, digging a test pit (hole) can only complete the test of one layer of stratum, and the test depth is very limited, so only shallow stratum tests can be carried out;

[0007] Second, the force transmission column is prone to friction with the pit (hole) wall, and the applied ground load cannot be effectively transmitted to K 30 On the load plate;

[0008] Third, when the ground load is applied by stacking, the force transmission column produces elastic flexural deformation. The greater the applied ground load, the greater the deformation of the force transmission column, resulting in inaccurate vertical displacement measurement data measured by the displacement measuring instrument (dial indicator);

[0009] Fourth, the greater the test depth, the worse the transmission effect of the above-mentioned ground-applied load, the lower the accuracy of the vertical displacement measurement data measured by the displacement meter, and the worse the deep vertical base coefficient test effect.

[0010] Therefore, when testing the vertical base coefficient of deep foundation soil, a device is needed that can solve the above problems and accurately measure the vertical base coefficient of multiple layers of deep foundation soil in one test pit (hole). Utility Model Content

[0011] Therefore, the utility model provides a test pit vertical base bed coefficient testing device, which can overcome the defects of the existing technology that the test stratum depth is limited and the test data is inaccurate due to the influence of the test depth, ground load, etc. on the transmission force.

[0012] In order to solve the above problems, the utility model provides a test pit vertical base coefficient test device, including a pressure plate, two reference piles are arranged at intervals on both sides of the pressure plate in the test pit, a reference beam is arranged horizontally on the reference pile, one end of the reference beam is fixedly connected to the first reference pile, and the other end is simply supported and connected to the second reference pile, a jack is also provided at the center of the pressure plate, two displacement measuring instruments are symmetrically arranged on both sides of the jack on the pressure plate, the measuring end of the displacement measuring instrument is in close contact with the reference beam, and the displacement measuring instrument The base end is fixed on the pressure plate, and a force transmission device is arranged above the jack. The force transmission device is connected to the reaction plate through a reaction force transmission arm. The reaction plate is adapted to the inner wall surface of the test pit. When the jack applies pressure to the force transmission device, the pressure is applied to the reaction plate and the pressure plate through the reaction force transmission arm. The reaction plate is in close contact with the inner wall surface of the test pit to prevent the force transmission device from generating vertical upward and horizontal displacement. The pressure is finally applied to the pressure plate, causing the pressure plate to generate settlement displacement.

[0013] In some embodiments, the reference pile includes a first reference pile and a second reference pile, one end of the reference beam is fixed to the first reference pile, and the other end is simply supported on the second reference pile.

[0014] In some embodiments, the displacement measuring instruments are symmetrically arranged on both sides of the jack, and the two displacement measuring instruments are equidistant from the center of the pressure plate.

[0015] In some embodiments, the force transmission device includes two force transmission plates and a force transmission column located between the two force transmission plates, and the force transmission column is fixedly connected to the force transmission plates.

[0016] In some embodiments, the force transmission column is a cylindrical steel member with a diameter greater than or equal to 20 cm and a wall thickness greater than or equal to 2 cm.

[0017] In some embodiments, one end of the reaction force transmission arm is rotatably connected to the force transmission device, and the other end is hinged to the reaction plate.

[0018] In some embodiments, the reaction force transmission arm includes a force transmission rod with hollow structures at both ends, and screws are connected to both ends of the force transmission rod through threads. The screws are rotated to adjust the length of the reaction force transmission arm.

[0019] In some embodiments, the test pits are stepped from top to bottom, and the diameters of the test pits decrease successively.

[0020] In some embodiments, the angle between the reaction force transmission arm and the radial direction of the test pit ranges from 40° to 50°.

[0021] The utility model provides a device for testing the vertical base bed coefficient in a test pit, wherein the device for testing the vertical base bed coefficient in the test pit is provided with a force transmission device and a jack is used to apply pressure to the force transmission device. At this time, the reaction force transmission arm transmits the pressure to the reaction plate and the pressure plate. Since the reaction plate is in contact with the inner wall of the test pit, the inner wall of the test pit plays an effective supporting reaction role to limit the vertical upward and horizontal displacement of the force transmission device, thereby causing the pressure plate to produce a settlement displacement. The displacement measuring instrument uses the reference beam as a reference, so that its axis is parallel to the vertical direction, accurately measures the settlement displacement of the pressure plate, and completes the measurement work. This method does not require the application of ground loads. The load is applied by replacing the heavy ground load with the limiting reaction force of the inner wall of the test pit, saving space. The solution is simpler, more economical, convenient, safe, and easy to implement. Since there is no need to set up ground loads and longer force transmission columns, target strata of any depth can be tested, and the problem of inaccurate measurement data caused by elastic flexural deformation of the force transmission column will not occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of a device for testing vertical bed coefficient in a test pit according to an embodiment of the present utility model;

[0023] Figure 2 A top view of a force transmission device of a test pit vertical bed coefficient testing device according to an embodiment of the present utility model;

[0024] Figure 3 This is a schematic diagram of the reaction plate structure of a test pit vertical base coefficient testing device according to an embodiment of the utility model.

[0025] The reference numerals indicate:

[0026] 1. Guard wall; 2. Pressure plate; 3. Jack; 4. Reference beam; 5. Reference pile; 6. Displacement measuring instrument; 7. Force transfer plate; 8. Force transfer column; 9. Reaction plate; 10. Anchor steel plate; 11. Hinge support; 12. Reaction force transfer arm; 13. Manual pressure oil pump; 14. Hydraulic pipe. DETAILED DESCRIPTION

[0027] See also Figures 1 to 3 As shown, according to an embodiment of the present invention, a test pit vertical base coefficient test device is provided, comprising a pressure plate 2, a displacement measuring instrument 6 is provided on the pressure plate 2, two reference piles 5 are spaced apart on both sides of the pressure plate 2 in the test pit, a reference beam 4 is horizontally provided on the reference pile 5, the measuring end of the displacement measuring instrument 6 is in close contact with the reference beam 4, the base end of the displacement measuring instrument 6 is fixed on the pressure plate 2, a jack 3 is further provided at the center of the pressure plate 2, and the upper part of the jack 3 is provided with a jack 3. A force transmission device is provided, and the force transmission device is connected to the reaction plate 9 through a reaction force transmission arm 12. The reaction plate 9 is adapted to the inner wall surface of the test pit. When the jack 3 applies pressure to the force transmission device, the pressure is applied to the reaction plate 9 and the pressure plate 2 through the reaction force transmission arm 12. The reaction plate 9 is in close contact with the inner wall surface of the test pit to prevent the force transmission device from generating vertical upward and horizontal displacement. The pressure is ultimately applied to the pressure plate 2, causing the pressure plate 2 to generate a settlement displacement. The jack 3 is used to apply pressure to the force transmission device. At this time, the reaction force transmission arm 12 transmits the pressure to the reaction plate 9. Since the reaction plate 9 is in contact with the inner wall surface of the test pit, the inner wall of the test pit plays an effective supporting reaction role to limit the force transmission device from generating vertical upward and horizontal displacement, thereby causing the pressure plate 2 to generate a settlement displacement. The displacement measuring instrument 6 uses the reference beam 4 as a reference, aligning its axis with the vertical direction to accurately measure the settlement displacement of the bearing plate 2 and complete the measurement. This device eliminates the need for heavy ground loading. Instead, it applies the load through the limiting reaction force of the test pit's inner wall, replacing the ground loading. This saves space and creates a simpler, more economical, convenient, safer, and easier-to-implement solution. Because there's no need for ground loading or a long force transmission column, target strata of any depth can be tested without the risk of inaccurate measurement data due to elastic flexural deformation of the force transmission column.

[0028] Specifically, the pressure plate is a circular steel plate with a diameter of 30 cm and a thickness greater than or equal to 20 mm.

[0029] Specifically, the jack is a hydraulic jack. The jack 3 is connected to a manual oil pump 13 via a hydraulic pipe 14. During operation, the manual oil pump 13 slowly applies pressure to the jack 3 and relieves pressure in stages. Loading and unloading should ensure uniform, continuous, and shock-free load transfer. The amplitude of each load stage during maintenance should not exceed ±10% of the stage load to improve the accuracy of the experimental data.

[0030] Specifically, the reaction plates 9 are dense wooden boards with a thickness of 50 mm or greater. Two square anchor steel plates 10, each 30 cm long and 2 cm thick, are fixed to each reaction plate with anchor bolts. A fixed hinge support 11 is welded to each anchor steel plate for hinged connection to the reaction force transmission arm 12. The reaction plates 9 can also be made of other materials, such as steel or iron. The reaction plates must not deform when providing reaction force and must have sufficient rigidity and strength.

[0031] Specifically, the reference beam 4 is an I-beam reference beam. The I-beam reference beam has sufficient rigidity and strength and is not easily deformed. In addition, scaffolding steel pipes, triangular trusses, channel steels and other components can also be used as the reference beam.

[0032] In one specific embodiment, the reference stakes 5 include a first reference stake and a second reference stake. One end of the reference beam 4 is fixed to the first reference stake, and the other end is simply supported on the second reference stake. Fixing one end of the reference beam 4 and simply supporting the other end can reduce the deflection of the reference beam 4 caused by temperature changes, thereby improving the accuracy of measurement data.

[0033] In a specific embodiment, the displacement measuring instrument 6 is located on opposite sides of the jack 3, and the two displacement measuring instruments 6 are at equal distances from the center of the pressure plate 2, so that a set of two settlement deformation data can be measured simultaneously and equivalently, making the measurement data more scientific.

[0034] In a specific embodiment, the force transmission device includes two force transmission plates 7 and a force transmission column 8 located between the two force transmission plates 7. The force transmission column 8 is fixedly connected to the force transmission plates 7 and can evenly and effectively transmit the pressure applied by the jack to the upper and lower force transmission plates 7, and evenly transmit it to the reaction plate 9 through four reaction force transmission arms. Setting up two upper and lower force transmission plates is conducive to the balance of force transmission and ensures that the four force transmission arms on the upper and lower force transmission plates transmit force evenly. The force transmission column is designed as a cylindrical component with high rigidity along the length direction and not easy to deform, ensuring effective and uniform force transmission between the upper and lower force transmission plates.

[0035] Specifically, the force transfer plates are two square steel plates with a side length of 50 cm and a thickness of 5 cm, which are placed parallel to the center on the jack 3, and a force transfer column 8 is fixedly connected between the two force transfer plates 7 at the centroid.

[0036] In one specific embodiment, the force transmission column 8 is a cylindrical steel member with a diameter greater than or equal to 20 cm and a wall thickness greater than or equal to 2 cm. This cylindrical steel member's high longitudinal rigidity and resistance to deformation ensures effective and uniform force transmission between the upper and lower force transmission plates. Preferably, the force transmission column is greater than or equal to 20 cm in height for ease of operation.

[0037] In a specific embodiment, one end of the reaction force transmission arm 12 is rotatably connected to the force transmission device, and the other end is hinged to the reaction plate 9. Through the hinged connection, the angle between the reaction force transmission arm 12 and the horizontal plane can be adjusted according to the diameter of the test pit to adjust the force direction.

[0038] In one specific embodiment, the reaction force transmission arm 12 comprises a force transmission rod with hollow ends. Screws are threadedly connected to each end of the force transmission rod. Rotating the screws adjusts the length of the reaction force transmission arm 12. This adjustable length of the reaction force transmission arm 12 allows the device to adapt to a wider range of application scenarios, accommodating various test pit diameters (widths), and providing greater versatility. The hollow ends ensure both installation requirements and sufficient strength.

[0039] Specifically, the reaction force transmission arm 12 is a force transmission rod with a hollow structure at both ends or throughout the entire length.

[0040] In a specific embodiment, the test pit is stepped from top to bottom, with the diameter of the test pit decreasing gradually. The pit sidewall is formed into a stepped shape with a diameter decreasing gradually, which facilitates the wall support and concrete pouring construction and is also beneficial to the stability of the pit wall.

[0041] In a specific embodiment, the angle between the reaction force transmission arm 12 and the horizontal plane ranges from 40° to 50°. Preferably, the angle is set to 45 degrees; this angle setting can provide more effective reaction force.

[0042] The present application also provides a method for testing a bed coefficient in a test pit, including the above-mentioned device for testing a vertical bed coefficient in a test pit, and the steps are as follows:

[0043] Step 1: Excavate the test pit in sections and set up cast-in-situ reinforced concrete retaining wall 1 in sections.

[0044] Step 2: Install the test pit vertical base bed coefficient test device in the test pit.

[0045] Step 3: Use the slow-maintained load method to gradually apply pressure to the jack 3, and then unload in stages to complete the vertical bed coefficient test of the stratum at this depth.

[0046] Step 4: Repeat steps 1 to 3 to complete the vertical bed coefficient test of the target strata at all depths below the ground.

[0047] Specifically, in the process of excavating the test pit in sections in step 1, the height of the reinforced concrete of each section of the retaining wall 1 is different, for example, 1.0m for hard rock layer and 0.5m for other strata.

[0048] The specific construction process is as follows:

[0049] (1) Excavate the test pit in sections from top to bottom, and set up cast-in-situ reinforced concrete retaining wall 1 in sections. The height of each retaining wall 1 is determined according to the specific soil properties;

[0050] ⑵. Dig the test pit to the test soil layer and level the bottom of the pit to form the test surface;

[0051] (3) Place a circular pressure plate 2 with a diameter of 30 cm and a thickness greater than or equal to 20 mm horizontally on the test surface;

[0052] (4) Place the hydraulic jack 3 vertically upward on the pressure plate 2;

[0053] (5) Place a reference beam 10 cm away from the hydraulic jack, parallel to the bearing plate 2, and 25 cm from the bottom of the test pit. Fix one end of the beam to the preset reference pile 5 in the test pit, and simply support the other end on the preset reference pile 5.

[0054] (6) Two displacement measuring instruments (dial indicators) 6 are symmetrically placed on both sides of the hydraulic jack, equidistant from the center of the pressure plate 2. The end with the base is fixed to the pressure plate 2, and the end with the displacement measuring instrument is so that the axis of the displacement measuring instrument is parallel to the vertical direction and in close contact with the reference beam 4.

[0055] ⑺. Place two square force transfer plates 7 with a side length of 50 cm and a thickness of 5 cm in parallel on the hydraulic jack 3. Place a cylindrical thick-walled steel pipe force transfer column 8 with a diameter greater than or equal to 20 cm vertically between the two force transfer plates 7 at the centroid, and fully weld it to the upper and lower force transfer plates 7 to ensure that the vertical force of the upper and lower force transfer plates 7 and the force transfer column 8 is uniform; set four bolt holes symmetrically at the four corners of the force transfer plate 7;

[0056] ⑻. Place four reaction plates 9, two on each side, parallel and symmetrically on both sides of the pressure plate 2, and place them vertically close to the side walls of the test pit; the reaction plates 9 are dense wooden boards with a thickness greater than or equal to 50 mm. Two square anchor steel plates 10 with a side length of 30 cm and a thickness of 2 cm are fixed to each reaction plate with anchor bolts, and a fixed hinge support 11 is welded to each anchor steel plate;

[0057] (9) Connect eight reaction force transmission arms 12 with holes at both ends to the hinge support 11 of the reaction plate 9 and the bolt holes of the force transmission steel plate with bolts to form four groups of symmetrical reaction force transmission arms 12;

[0058] ⑽. Adjust the retractable screws at both ends of the reaction force transmission arm 12 to an appropriate length so that the reaction plate 9 is close to the side wall of the test pit to ensure effective provision of the test reaction force;

[0059] ⑾. After the vertical test device is installed, pressurize it on the ground through the manual pressure oil pump 13, and transmit the pressure to the hydraulic jack 3 through the hydraulic pipe 14;

[0060] ⑿. The test loading adopts the slow maintenance load method, which is applied step by step until the termination test requirements specified in the relevant specifications, and then unloaded in stages to complete the vertical bed coefficient test of the depth formation;

[0061] ⒀. Repeat the above steps (1) to (10) to complete the vertical bed coefficient test of the target strata at all depths below the ground;

[0062] ⒁. Compact and backfill the test pit in layers.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. Such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A device for testing vertical base bed coefficient in a test pit, characterized in that: The invention comprises a pressure plate (2), two reference piles (5) are arranged at intervals on both sides of the pressure plate (2) in the test pit, a reference beam (4) is arranged horizontally on the reference pile (5), a jack (3) is also arranged at the center of the pressure plate (2), two displacement measuring instruments (6) are arranged on the pressure plate (2) symmetrically on both sides of the jack (3), the measuring end of the displacement measuring instrument (6) is in close contact with the reference beam (4), the base end of the displacement measuring instrument (6) is fixed on the pressure plate (2), and a force transmission device is arranged above the jack (3). The force transmission device is connected to the reaction plate (9) through the reaction force transmission arm (12), and the reaction plate (9) is adapted to the inner wall surface of the test pit. When the jack (3) applies pressure to the force transmission device, the pressure is applied to the reaction plate (9) and the pressure plate (2) through the reaction force transmission arm (12). The reaction plate (9) is in close contact with the inner wall surface of the test pit to prevent the force transmission device from generating vertical upward and horizontal displacement. The pressure is finally applied to the pressure plate (2), causing the pressure plate (2) to generate a settlement displacement.

2. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The reference pile (5) comprises a first reference pile and a second reference pile, one end of the reference beam (4) is fixed to the first reference pile, and the other end is simply supported on the second reference pile.

3. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The displacement measuring instruments (6) are symmetrically arranged on both sides of the jack (3), and the two displacement measuring instruments (6) are equidistant from the center of the pressure plate (2).

4. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The force transmission device comprises two force transmission plates (7) and a force transmission column (8) located between the two force transmission plates (7), and the force transmission column (8) is fixedly connected to the force transmission plates (7).

5. The device for testing vertical bed coefficient in a test pit according to claim 4, characterized in that: The force transmission column (8) is a cylindrical steel member with a diameter greater than or equal to 20 cm and a wall thickness greater than or equal to 2 cm.

6. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: One end of the reaction force transmission arm (12) is rotatably connected to the force transmission device, and the other end is hinged to the reaction plate (9).

7. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The reaction force transmission arm (12) comprises a transmission rod with a hollow structure at both ends, and screw rods are connected to both ends of the transmission rod via threads, and the screw rods are rotated to adjust the length of the reaction force transmission arm (12).

8. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The test pits are stepped from top to bottom, and the diameters of the test pits decrease successively.

9. The device for testing vertical bed coefficient in a test pit according to claim 1, characterized in that: The angle between the reaction force transmission arm (12) and the radial direction of the test pit ranges from 40° to 50°.

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