Pile-soil contact surface mechanical property testing device based on temperature control triaxial apparatus

Abstract

The invention discloses a pile-soil contact surface mechanical property testing device based on a temperature control triaxial apparatus. The pile-soil contact surface mechanical property testing device comprises a sample device, a pressurizing device, a temperature control device and a data acquisition device, through the arrangement of the pressurizing device, the actual stress of a soil body in a pile foundation system is effectively simulated; a heat transfer channel is arranged in a pile sample, and a constant-temperature water bath assembly is communicated with a pressure chamber and the heat transfer channel through a liquid pipeline, so that the temperature of the pile sample and a soil sample is effectively controlled, and the problem of measuring the friction force of a pile-soil contact surface is effectively solved by modifying a pressure chamber of a conventional temperature control triaxial apparatus; according to the device and the method, the measurement of the consolidation process of soil around a pile, the influence of a pile sample and the mechanical property change of a pile-soil contact surface in the shearing process under the conditions of different temperatures, axial loads and pressures is effectively realized, and intuitive and three-dimensional observation and test are facilitated; the method is simple in operation steps, high in operability, convenient to control and easy to implement.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering geotechnical testing instruments, and in particular to a pile-soil contact surface mechanical property testing device based on a temperature-controlled triaxial instrument. Background Art

[0002] The contact surface problem is an important research topic in the field of geotechnical engineering. The contact surface problem between soil and structure, soil and soil is involved in earth-rock dam projects, port terminals, bridges and tunnels, foundations and other projects. Under the action of external loads, due to the large differences in the stress-deformation characteristics of soil or structures of different materials, stress concentration, large shear deformation, slip, displacement discontinuity, fracture, mutual embedding and other phenomena often occur at the contact surface. Improper handling of the contact surface problem will lead to local damage or even overall destruction of the structure. Therefore, the study of the stress and deformation coordination characteristics at the contact surface has important theoretical and engineering practical significance.

[0003] The pile body will produce thermal deformation under the influence of temperature changes, which will cause cyclic shearing of the soil around the pile, weaken the bearing capacity of the foundation, and bring risks to the normal use of the pile body. Since the traditional triaxial instrument cannot simulate the temperature changes during the working process of the pile body, there is little research on the change law of the mechanical properties of the pile-soil contact surface under the influence of temperature. For example, the Chinese invention patent "A pile-soil contact surface mechanical properties test device and test method" with patent number 201210078542.1 discloses a pile-soil contact surface friction test device and test method based on a conventional geotechnical triaxial instrument; concrete samples and hollow cylindrical soil samples are arranged in the pressure chamber of the conventional geotechnical triaxial instrument, and the pile-soil contact surface friction value is measured by compressing the samples. Compared with conventional direct shear instrument and single shear instrument tests, this technical method can consider the working conditions of the surrounding soil samples such as drainage and non-drainage, and can measure the axial deformation and volume deformation of the soil at the same time; however, this test device cannot consider the influence of factors such as the temperature of the pile sample and the test temperature of the surrounding soil. Summary of the invention

[0004] The purpose of the present invention is to provide a pile-soil contact surface mechanical property testing device based on a temperature-controlled triaxial instrument to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides a device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus, comprising a sample device, a pressurizing device, a temperature control device and a data acquisition device;

[0006] The sample device comprises a reaction frame, a pressure chamber installed on the reaction frame and a sample arranged in the pressure chamber, wherein the sample comprises a pile sample, the periphery of the pile sample is covered with a soil sample, and the outer side of the soil sample is covered with a rubber film;

[0007] The pressurizing device comprises a loading assembly, a confining pressure regulating assembly and a back pressure regulating assembly; the loading assembly contacts and cooperates with the pile sample, and the loading assembly is fixedly mounted on the back force frame; the confining pressure regulating assembly is connected to the pressure chamber through a confining pressure pipeline, and applies surrounding pressure to the rubber membrane through the pressure chamber; the back pressure regulating assembly is connected to the soil sample through a back pressure pipeline, and directly applies back pressure to the soil sample;

[0008] The temperature control device comprises a constant temperature water bath assembly, a heat transfer channel is arranged inside the pile sample, the constant temperature water bath assembly is connected with the pressure chamber and the heat transfer channel respectively through a liquid pipeline, and is used to control the temperature of the soil sample and the temperature of the pile sample respectively;

[0009] The data acquisition device is used to collect the axial displacement, axial force, pore water pressure and volume deformation data of the sample during the test.

[0010] Preferably, the pressure chamber includes a base, the bottom end of the base is fixedly mounted on the reaction frame via a supporting platform, a top cover is arranged above the base, the base and the top cover are connected via a screw, a sealing cover is arranged between the base and the top cover, and the two ends of the sealing cover are respectively sealed and fixed to the base and the top cover; the sample is arranged in the sealing cover and installed between the base and the top cover; a bottom drain pipe, the confining pressure pipeline and the back pressure pipeline are installed on the base, and an exhaust pipeline and the liquid pipeline are installed on the top cover.

[0011] Preferably, the top of the base and the bottom of the top cover are both provided with mounting grooves, a bottom sealing block is provided in the mounting groove of the base, a lower water-permeable plate is provided at the top of the bottom sealing block, the bottom end of the pile sample passes through the lower water-permeable plate, the bottom sealing block, and the base in sequence and extends to the bottom of the base, the soil sample contacts the top of the lower water-permeable plate; the back pressure pipeline passes through the bottom sealing block and contacts the lower water-permeable plate;

[0012] A top sealing block is arranged in the mounting groove of the top cover, an upper water-permeable plate is arranged at the bottom end of the top sealing block, and the soil sample contacts the bottom end of the upper water-permeable plate; a groove is opened at the bottom end of the top sealing block, the pile sample is slidably connected in the groove, a sample cap is arranged at the top end of the pile sample, and the bottom end of the loading assembly passes through the top cover and the top sealing block in sequence and contacts the top end of the sample cap; the two ends of the rubber membrane are fixedly connected to the top sealing block and the bottom sealing block respectively.

[0013] Preferably, a connecting pipe is provided through the sample cap, the bottom end of the connecting pipe is connected to the heat transfer channel in the pile sample, the top end of the connecting pipe is connected to the groove, and a top drain pipe is installed on the top cover, the bottom end of the top drain pipe passes through the top sealing block and is connected to the groove.

[0014] Preferably, threads are provided on the outer wall of the top drain pipe, the top drain pipe is threadedly connected to the top cover, and the bottom end of the top drain pipe is threadedly connected to the top sealing block.

[0015] Preferably, the thickness of the rubber film is 0.1 mm to 0.2 mm, and both ends of the rubber film are fastened to the top sealing block and the bottom sealing block through rubber rings.

[0016] Preferably, the supporting platform is a lifting platform, and the top end of the screw rod contacts the top end of the reaction frame.

[0017] Preferably, temperature sensors are provided in the sealing cover and the heat transfer channel.

[0018] Preferably, an annular buffer block is provided between the sample cap and the pile sample, the annular buffer block is made of rubber or polyurethane material, and the compression amount of the annular buffer block is 0.3-0.6.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] The device for testing the mechanical properties of the pile-soil contact surface based on the temperature-controlled triaxial instrument provided by the present invention effectively simulates the actual stress of the soil in the pile foundation system by setting a pressurizing device; by setting a heat transfer channel inside the pile sample and connecting the constant temperature water bath assembly with the pressure chamber and the heat transfer channel through a liquid pipeline, the temperature of the pile sample and the soil sample is effectively controlled, and by modifying the pressure chamber of the conventional temperature-controlled triaxial instrument, the problem of measuring the friction force of the pile-soil contact surface is effectively realized; the present invention effectively realizes the measurement of the consolidation process of the soil around the pile under different temperatures, axial loads and pressure conditions, the extent of the influence on the pile sample, and the change of the mechanical properties of the pile-soil contact surface during the shearing process, which is convenient for intuitive and three-dimensional observation and testing; the present invention has a simple structure, and the improved pressure chamber and the combined temperature control device can be directly used on the existing instrument; the present invention has simple operating steps, strong operability, is easy to control, and is easy to realize. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a structural schematic diagram of a pile-soil contact surface mechanical property testing device of the present invention;

[0023] In the figure: 1. reaction frame; 2. pile sample; 3. soil sample; 4. rubber membrane; 5. loading assembly; 6. confining pressure pipeline; 7. back pressure pipeline; 8. heat transfer channel; 9. liquid pipeline; 10. base; 11. support platform; 12. top cover; 13. screw; 14. sealing cover; 15. bottom drain pipe; 16. exhaust pipeline; 17. bottom sealing block; 18. lower water-permeable plate; 19. top sealing block; 20. upper water-permeable plate; 21. sample cap; 22. connecting pipe; 23. top drain pipe; 24. annular buffer block. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0025] like Figure 1 As shown, the present invention provides a pile-soil contact surface mechanical property testing device based on a temperature-controlled triaxial instrument, comprising a sample device, a pressurizing device, a temperature control device and a data acquisition device;

[0026] The sample device comprises a reaction frame 1, a pressure chamber installed on the reaction frame 1 and a sample arranged in the pressure chamber, wherein the sample comprises a pile sample 2, the periphery of the pile sample 2 is covered with a soil sample 3, and the outer side of the soil sample 3 is covered with a rubber film 4;

[0027] The pressurizing device includes a loading component 5, a confining pressure regulating component and a back pressure regulating component; the loading component 5 is in contact with the pile sample 2, and the loading component 5 is fixedly installed on the reaction frame 1; the confining pressure regulating component is connected to the pressure chamber through the confining pressure pipeline 6, and applies surrounding pressure to the rubber membrane 4 through the pressure chamber; the back pressure regulating component is connected to the soil sample 3 through the back pressure pipeline 7, and directly applies back pressure to the soil sample 3;

[0028] The temperature control device includes a constant temperature water bath assembly, and a heat transfer channel 8 is provided inside the pile sample 2. The constant temperature water bath assembly is connected to the pressure chamber and the heat transfer channel 8 through a liquid pipeline 9, and is used to control the temperature of the soil sample 3 and the temperature of the pile sample 2 respectively;

[0029] The data acquisition device uses a temperature-controlled triaxial instrument purchased from the market, such as the TSZ series fully automatic triaxial instrument. Its working principle and usage are known prior art and will not be described in detail here. The data acquisition device is used to collect the axial displacement, axial force, pore water pressure and volume deformation data of the sample during the test.

[0030] The present invention effectively simulates the actual stress of the soil in the pile foundation system by setting a pressurizing device; by setting a heat transfer channel 8 inside the pile sample 2 and connecting a constant temperature water bath assembly with a pressure chamber and the heat transfer channel 8 through a liquid pipeline 9, the temperature of the pile sample 2 and the soil sample 3 is effectively controlled; and by modifying the pressure chamber of a conventional temperature-controlled triaxial instrument, the problem of measuring the friction force on the pile-soil contact surface is effectively achieved.

[0031] A further optimized solution is provided to ensure the sealing and stability of the pressure chamber, wherein the pressure chamber comprises a base 10, the bottom end of the base 10 is fixedly mounted on the reaction frame 1 through a supporting platform 11, a top cover 12 is arranged above the base 10, the base 10 and the top cover 12 are connected by a screw 13, a sealing cover 14 is arranged between the base 10 and the top cover 12, and the two ends of the sealing cover 14 are respectively sealed and fixed to the base 10 and the top cover 12; the sample is arranged in the sealing cover 14 and mounted between the base 10 and the top cover 12; a bottom drain pipe 15, a confining pressure pipeline 6 and a back pressure pipeline 7 are installed on the base 10, and an exhaust pipeline 16 and a liquid pipeline 9 are installed on the top cover 12.

[0032] The scheme is further optimized to facilitate the application of loading force to the pile sample 2. The top of the base 10 and the bottom of the top cover 12 are both provided with installation grooves. A bottom sealing block 17 is provided in the installation groove of the base 10. A lower water-permeable plate 18 is provided at the top of the bottom sealing block 17. The bottom end of the pile sample 2 passes through the lower water-permeable plate 18, the bottom sealing block 17, and the base 10 in sequence and extends to the bottom of the base 10. The soil sample 3 contacts the top of the lower water-permeable plate 18; the back pressure pipeline 7 passes through the bottom sealing block 17 and contacts the lower water-permeable plate 18.

[0033] A top sealing block 19 is arranged in the mounting groove of the top cover 12, an upper water-permeable plate 20 is arranged at the bottom end of the top sealing block 19, and the soil sample 3 contacts the bottom end of the upper water-permeable plate 20; a groove is opened at the bottom end of the top sealing block 19, the pile sample 2 is slidably connected in the groove, a sample cap 21 is arranged at the top end of the pile sample 2, and the bottom end of the loading assembly 5 passes through the top cover 12 and the top sealing block 19 in sequence and contacts the top end of the sample cap 21; the two ends of the rubber membrane 4 are fixedly connected to the top sealing block 19 and the bottom sealing block 17 respectively.

[0034] A further optimized solution is that when controlling the temperature of the pile sample 2, in order to facilitate the discharge of water in the pile sample 2, a connecting pipe 22 is provided through the sample cap 21, the bottom end of the connecting pipe 22 is connected to the heat transfer channel 8 in the pile sample 2, the top end of the connecting pipe 22 is connected to the groove, and a top drain pipe 23 is installed on the top cover 12, the bottom end of the top drain pipe 23 passes through the top sealing block 19 and is connected to the groove.

[0035] To further optimize the solution, in order to ensure that the pile sample 2 and the soil sample 3 can normally produce relative displacement during the test, a thread is opened on the outer wall of the top drainage pipe 23, the top drainage pipe 23 is threadedly connected to the top cover 12, and the bottom end of the top drainage pipe 23 is threadedly connected to the top sealing block 19.

[0036] According to a further optimized solution, the thickness of the rubber film 4 is 0.1 mm to 0.2 mm, and both ends of the rubber film 4 are fastened to the top sealing block 19 and the bottom sealing block 17 through rubber rings.

[0037] To further optimize the solution, in order to facilitate the consolidation of the soil around the pile, the support platform 11 is a lifting platform, and the top end of the screw rod 13 is in contact with the top end of the reaction frame 1.

[0038] To further optimize the solution, temperature sensors are provided in the sealing cover 14 and the heat transfer channel 8 to facilitate the control of the temperature of the sample.

[0039] A further optimization scheme is to prevent the uneven contact between the sample cap 21 and the pile sample 2 from affecting the force on the pile sample 2 and damaging the pile sample 2 during the loading process, an annular buffer block 24 is provided between the sample cap 21 and the pile sample 2. The annular buffer block 24 is made of rubber or polyurethane material, and the compression amount of the annular buffer block 24 is 0.3 to 0.6.

[0040] By controlling the compression amount of the annular buffer block 24 , the annular buffer block 24 can adapt to the shape of the top end of the pile sample 2 while having a good force transmission effect, ensuring that the force applied by the loading assembly 5 can act on the pile sample 2 .

[0041] The pile-soil contact surface mechanical property testing device based on the temperature-controlled triaxial instrument provided by the present invention is used in the following process:

[0042] First, install the sample, set a rubber membrane 4 on the outside of the sample, and use a rubber ring to tighten it between the top sealing block 19 and the bottom sealing block 17, then align the top sealing block 19 and the bottom sealing block 17 with the mounting grooves on the top cover 12 and the base 10, then snap the top sealing block 19 into the mounting groove of the top cover 12, snap the bottom sealing block 17 into the mounting groove of the base 10, and then use the top drain pipe 23 to connect and fix the top sealing block 19 to the top cover 12; then use the screw 13 to limit the distance between the base 10 and the top cover 12, and make the top end of the screw 13 contact with the reaction frame 1, then use the support platform 11 to install the base 10 on the reaction frame 1, and control the loading assembly 5 to contact with the sample cap 21 to complete the assembly of the device.

[0043] Then, according to the test needs, the sample is pressurized through the confining pressure pipeline 6 or the back pressure pipeline 7. During this process, the gas in the sealing cover 14 is discharged through the exhaust pipeline 16 and the valve on the exhaust pipeline 16 is closed. After the sample is pressurized, the sample is heated according to the test requirements. The liquid in the pressure chamber can be isobarically replaced through the liquid pipeline 9 connected to the pressure chamber to achieve heating of the soil sample 3 while keeping the confining pressure unchanged. The pile sample 2 can be heated through the liquid pipeline 9 connected to the heat transfer channel 8 inside the pile sample 2, and the water used for heating can be discharged through the top drain pipe 23. After the test conditions are met, the pile sample 2 is pressurized through the loading assembly 5, and the axial displacement, axial force, pore water pressure and volume deformation data during the test can be obtained using the data acquisition device.

[0044] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A pile-soil contact surface mechanical properties testing device based on a temperature-controlled triaxial instrument, characterized in that: It includes a sample device, a pressurizing device, a temperature control device and a data acquisition device; The sample device comprises a reaction frame (1), a pressure chamber installed on the reaction frame (1), and a sample arranged in the pressure chamber, wherein the sample comprises a pile sample (2), the periphery of the pile sample (2) is covered with a soil sample (3), and the outer side of the soil sample (3) is covered with a rubber film (4); The pressurizing device comprises a loading component (5), a confining pressure regulating component and a back pressure regulating component; the loading component (5) is in contact with the pile sample (2), and the loading component (5) is fixedly mounted on the reaction frame (1); the confining pressure regulating component is connected to the pressure chamber through a confining pressure pipeline (6), and applies surrounding pressure to the rubber membrane (4) through the pressure chamber; the back pressure regulating component is connected to the soil sample (3) through a back pressure pipeline (7), and directly applies back pressure to the soil sample (3); The temperature control device comprises a constant temperature water bath component, a heat transfer channel (8) is arranged inside the pile sample (2), the constant temperature water bath component is connected to the pressure chamber and the heat transfer channel (8) through a liquid pipeline (9), and is used to control the temperature of the soil sample (3) and the temperature of the pile sample (2) respectively; The data acquisition device is used to collect the axial displacement, axial force, pore water pressure and volume deformation data of the sample during the test.

2. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 1, characterized in that: The pressure chamber comprises a base (10), the bottom end of the base (10) is fixedly mounted on the reaction frame (1) via a support platform (11), a top cover (12) is arranged above the base (10), the base (10) and the top cover (12) are connected via a screw (13), a sealing cover (14) is arranged between the base (10) and the top cover (12), and the two ends of the sealing cover (14) are respectively sealed and fixed to the base (10) and the top cover (12); the sample is arranged in the sealing cover (14) and installed between the base (10) and the top cover (12); a bottom drain pipe (15), the confining pressure pipeline (6) and the back pressure pipeline (7) are installed on the base (10), and an exhaust pipeline (16) and the liquid pipeline (9) are installed on the top cover (12).

3. The device for testing the mechanical properties of the pile-soil contact surface based on the temperature-controlled triaxial apparatus according to claim 2 is characterized in that: The top end of the base (10) and the bottom end of the top cover (12) are both provided with mounting grooves, a bottom sealing block (17) is arranged in the mounting groove of the base (10), a lower water-permeable plate (18) is arranged at the top end of the bottom sealing block (17), the bottom end of the pile sample (2) passes through the lower water-permeable plate (18), the bottom sealing block (17), and the base (10) in sequence and extends to the bottom of the base (10), the soil sample (3) contacts the top end of the lower water-permeable plate (18); the back pressure pipeline (7) passes through the bottom sealing block (17) and contacts the lower water-permeable plate (18); A top sealing block (19) is arranged in the installation groove of the top cover (12), an upper water-permeable plate (20) is arranged at the bottom end of the top sealing block (19), and the soil sample (3) contacts the bottom end of the upper water-permeable plate (20); a groove is opened at the bottom end of the top sealing block (19), the pile sample (2) is slidably connected in the groove, a sample cap (21) is arranged at the top end of the pile sample (2), and the bottom end of the loading assembly (5) passes through the top cover (12) and the top sealing block (19) in sequence and contacts the top end of the sample cap (21); the two ends of the rubber membrane (4) are fixedly connected to the top sealing block (19) and the bottom sealing block (17) respectively.

4. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 3, characterized in that: A connecting pipe (22) is provided through the sample cap (21), the bottom end of the connecting pipe (22) is connected to the heat transfer channel (8) in the pile sample (2), the top end of the connecting pipe (22) is connected to the groove, and a top drain pipe (23) is installed on the top cover (12), the bottom end of the top drain pipe (23) passes through the top sealing block (19) and is connected to the groove.

5. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 4, characterized in that: The outer wall of the top drain pipe (23) is provided with threads, the top drain pipe (23) is threadedly connected to the top cover (12), and the bottom end of the top drain pipe (23) is threadedly connected to the top sealing block (19).

6. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 3, characterized in that: The thickness of the rubber film (4) is 0.1 mm to 0.2 mm, and both ends of the rubber film (4) are fastened to the top sealing block (19) and the bottom sealing block (17) via rubber rings.

7. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 2, characterized in that: The supporting platform (11) is a lifting platform, and the top end of the screw rod (13) is in contact with the top end of the reaction frame (1).

8. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 2, characterized in that: Temperature sensors are provided in the sealing cover (14) and in the heat transfer channel (8).

9. The device for testing the mechanical properties of the pile-soil contact surface based on a temperature-controlled triaxial apparatus according to claim 3, characterized in that: An annular buffer block (24) is arranged between the sample cap (21) and the pile sample (2). The annular buffer block (24) is made of rubber or polyurethane material, and the compression amount of the annular buffer block (24) is 0.3-0.6.

Images