A pile-soil friction indoor test device under horizontal cyclic / monotonous action and its installation method

Abstract

The present invention discloses an indoor test device for pile-soil friction under horizontal cyclic / monotonic action, comprising a reaction force system and a model box, wherein the model box is filled with soil and a plurality of soil physical and mechanical parameter acquisition elements, a loading system is provided on the reaction force system, the loading system is located above and corresponding to the simulation box, the end face of the model box facing the loading system is an open end, one end of the simulation pile is mounted on the loading system, the other part of the simulation pile is inserted into the soil and placed in the simulation box, the pile body of the simulation pile is provided with a plurality of physical and mechanical state acquisition elements, the top of the simulation pile is provided with a horizontal displacement meter, and the loading system has cyclic force loading and continuous force loading functions. The test device can carry out indoor tests of pile-soil contact friction under horizontal cyclic and monotonic action with different soil properties and different pile foundation forms, can intuitively display the evolution characteristics of pile-soil contact, reveal the dynamic shear friction law of pile-soil contact under horizontal load, and provide reasonable experimental comparison data for theoretical and numerical analysis verification.

Description

Technical Field

[0001] The invention relates to an indoor test device for pile-soil friction, in particular to an indoor test device for pile-soil friction under horizontal circulation / monotonous action, and also to an installation method of the indoor test device for pile-soil friction under horizontal circulation / monotonous action. Background Art

[0002] Due to the influence of the pile foundation supporting structure and the environment in which it is located (such as the marine environment), it will be affected by horizontal loads and often bear the effects of horizontal cyclic loads, such as wave loads in the ocean and rivers. At present, there are many studies in this area, and most of the studies focus on the weakening characteristics of the soil around the pile under the action of horizontal cyclic loads. However, in fact, the pile-soil contact friction characteristics will also change with the action of horizontal cyclic loads. On the other hand, in order to study the limit state of pile-soil shear contact under horizontal loads, it is necessary to carry out research on the pile-soil contact characteristics under the action of extreme monotonic horizontal loads. However, there is currently a lack of relevant indoor test equipment, and there is a lack of indoor test equipment for intuitively studying the pile-soil shear friction characteristics. The present invention discloses an indoor test equipment and a method for using pile foundation shear friction under horizontal cyclic and monotonic loads. Summary of the Invention

[0003] In view of the shortcomings of the background technology, the technical problem to be solved by the present invention is to provide an indoor test device for pile-soil friction under horizontal cyclic / monotonous action. The test device can carry out indoor tests on pile-soil contact friction under horizontal cyclic and monotonic action of different soil properties and different pile foundation forms, and can intuitively display the evolution characteristics of pile-soil contact, and reveal the dynamic shear friction law of pile-soil contact under horizontal load.

[0004] To this end, the present invention provides an indoor test device for pile-soil friction under horizontal cyclic / monotonic action, including a reaction force system and a model box, wherein the model box is filled with soil and multiple soil physical and mechanical parameter collection elements, the reaction force system is provided with a loading system, the loading system is located above the simulation box and corresponds to it, the end face of the model box facing the loading system is an open end, one end of the simulation pile is installed on the loading system, and the other part of the simulation pile is inserted into the soil and placed in the simulation box, the pile body of the simulation pile is provided with multiple physical and mechanical state collection elements, and the top of the simulation pile is provided with a horizontal displacement meter, and the loading system has cyclic force loading and continuous force loading functions.

[0005] In the present invention, the horizontal loading servo motor in the horizontal loading system controls the loading mode through a computer, selects the horizontal cyclic force loading or monotonic continuous force loading function, and selects the displacement or force control loading magnitude. The horizontal loading servo motor is used to simulate the pile body bearing horizontal cyclic load or monotonic continuous limit load, intuitively showing the dynamic shear friction law of the pile body in contact with the soil under the action of horizontal cyclic or monotonic drop load, and intuitively observing the physical response of the pile body and the deformation characteristics of the soil body. Data collection is carried out by connecting the soil body physical and mechanical parameter collection element with an external computer collection instrument to provide reasonable experimental comparison data for theoretical and numerical analysis verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Schematic diagram of the cross-sectional structure of an indoor test device for pile-soil friction under horizontal cyclic / monotonous action in the present invention;

[0007] Figure 2 for Figure 1 A schematic diagram of the top view of an indoor test device for pile-soil friction under horizontal cyclic / monotonous action;

[0008] Figure 3 for Figure 1 A schematic cross-sectional structure diagram of a simulation box of an indoor test device for pile-soil friction under horizontal cyclic / monotonous action;

[0009] Figure 4 for Figure 1 Schematic diagram of the structure of the horizontal loading bracket of the indoor test device for pile-soil friction under horizontal cyclic / monotonic action. DETAILED DESCRIPTION

[0010] Reference Figure 1-Figure 4As shown, the present invention provides an indoor test apparatus for pile-soil friction under horizontal cyclic / monotonous action, comprising a reaction force system 1 and a model box 2. The model box 2 is filled with soil 3 and multiple soil physical and mechanical parameter acquisition elements 4, which can be soil pressure sensors, piezometers, or fiber-optic micro-soil pressure cells. The reaction force system 1 is equipped with a liftable loading system, which is located above and in correspondence with the simulation box. The end of the model box 1 facing the loading system is open. One end of a simulated pile 5 is mounted on the loading system. The simulated pile 5 is inserted into the soil and placed within the simulation box. A horizontal displacement meter 6, which can be a dial indicator or an electronic displacement acquisition device, is installed on the top of the simulated pile 5. The simulated pile 5 is also equipped with multiple pile body physical and mechanical state acquisition elements 7, which utilize FBG optical fiber gratings. The horizontal displacement meters 6 record horizontal displacement manually or automatically by computer. The soil physical and mechanical parameter acquisition elements 4 and the pile body physical and mechanical state acquisition elements 7 are connected to external computer data acquisition equipment for data collection. The loading system has the functions of cyclic force loading and continuous force loading. Cyclic force loading means that different loading forces appear within a cycle time, and the loading cycle is repeated.

[0011] The reaction system 1 includes a reaction frame 8, a threaded rigid column 9 and a rigid base 10. The rigid base 10 is fixed to the bottom of the threaded rigid column 9. The reaction frame 8 is connected to the threaded rigid column 9 and is raised and lowered by a main electric lift 11. A jack reaction frame 12 is fixed to the end of the reaction frame 8 facing the simulation box 2. The model box 2 is fixedly mounted on the rigid base 10 by a rigid block 26. When installing the simulation box, the reaction frame 8 is adjusted to the highest position by the main electric lift 11, and then the simulation box 2 is placed and fixed to the rigid base 10 by the rigid block 26.

[0012] The simulation box 2 is semi-cylindrical and consists of a rigid steel plate 13 and a transparent plate 14. The rigid steel plate 13 and transparent plate 14 are connected by glue with a waterproof rubber pad 15. The transparent plate 14 is a high-strength resin transparent plate. The contact surface of the simulated pile 5 with the transparent plate 14 is adhered with rubber. Lubricating oil is applied between the simulated pile 5 and the transparent plate 14 to minimize friction between the simulated pile 5 and the transparent plate 14. The rigid steel plate 13 is distributed with a number of drainage holes 16. Several microgrooves 17 are arranged on the outside of the rigid plate 13, and the microgrooves 17 are connected to the drainage holes 16. The number and arrangement of the drainage holes 16 are set according to the drainage requirements of the test. When the test requires undrained conditions, the drainage holes 16 are sealed. When the test requires drainage and consolidation of the soil, vacuum preloading and other methods can be used for consolidation and reinforcement. Water in the soil is drained through the drainage holes 16 and microgrooves 17 for drainage and consolidation. Relevant indoor tests are conducted under both drainage and undrained conditions.

[0013] The loading system includes a vertical loading system and a horizontal loading system 18. The vertical loading system includes a semi-annular jack 19, which is a semi-annular special hydraulic jack. The semi-annular jack 19 is fixed to the jack reaction frame 12 of the reaction system. The semi-annular jack 19 is placed in the center above the simulation box 9. The lower end of the semi-annular jack 19 is loaded on the upper surface of the soil. The semi-annular jack 19 is used to provide a stable overburden pressure to ensure that the initial stress state of the soil is close to that of the site. The semi-annular jack is controlled manually or by computer intelligence according to the test requirements. If it is a geotechnical centrifuge test, a servo-controlled jack is used, and mechanical control is used as much as possible.

[0014] The horizontal loading system 18 includes a horizontal loading bracket 20, two horizontal loading servo motors 21, and a horizontal loading force transmission rigid rod 22. The horizontal loading bracket 20 is connected to the threaded rigid column 9 of the reaction system 1 and is controlled by a secondary electric lift 23 to adjust the height of the horizontal loading system 18, thereby maintaining a vertical and appropriate loading position relative to the simulated pile 5. The two horizontal loading servo motors 21 are respectively arranged at both ends of the horizontal loading bracket 20. The two ends of the horizontal loading force transmission rigid rod 22 are respectively connected to the horizontal loading servo motors 21 at both ends. The horizontal loading force transmission rigid rod 22 is provided with a pile cap 24. The horizontal loading bracket 20 has a slot 25 at a position corresponding to the pile cap 24. One end of the simulated pile 5 passes through the slot 25 and is connected to the pile cap 24. The simulated pile 5 is subjected to cyclic displacement loading or continuous force loading within the arc-shaped slot 25. The horizontal loading system 18 is arranged near the transparent plate 14, through which the contact state of the simulated pile 5 with the surrounding soil can be observed.

[0015] A method for installing an indoor test device for pile-soil friction under horizontal cyclic / monotonous action, comprising the following steps:

[0016] (1) According to the test requirements, determine the dimensions of the simulated pile 5, the simulation box 2, and the reaction force system 1, and determine the arrangement and number of the drainage holes 16, the number and arrangement positions of the soil physical and mechanical state acquisition elements 4 and the pile body physical and mechanical state acquisition elements 7, and lay the pile body physical and mechanical state acquisition elements 7 on the pile body of the simulated pile according to the number and position requirements;

[0017] (2) Build the reaction system. The reaction frame 8 and the jack reaction frame 12 are fixed together by rivets. The reaction frame 8 is connected to the threaded rigid column 9 and is controlled to rise and fall by the main electric lift 11. The reaction frame and the jack reaction frame are adjusted to the highest position by the main electric lift 22. The model box 2 is placed and fixed to the rigid base 10 by the rigid block 26. The ring jack is fixed to the jack reaction frame.

[0018] (3) Install the horizontal loading bracket 20, connect the horizontal loading bracket 20 to the threaded rigid column and install the secondary electric lift 23. Use the secondary electric lift to control the lifting of the horizontal loading bracket 20. First, adjust the horizontal loading bracket 20 to the highest position;

[0019] (4) laying a model pile body physical and mechanical state acquisition element 7 on the pile body of the model pile 5, laying soil in the model box 2 and arranging a soil body physical and mechanical state acquisition element 4 in the soil body, arranging the simulation pile 5 with the pile body physical and mechanical state acquisition element in the soil body, and pre-treating the soil body to be tested according to the different tests and soil properties, such as drainage consolidation, etc., and a vacuum preloading consolidation system can be used for soil drainage consolidation;

[0020] (5) Install the horizontal loading system, install the horizontal loading servo motors 21 on both sides of the horizontal loading bracket, install the pile cap, and connect the two ends of the horizontal loading force transmission rigid rod 22 to the horizontal loading servo motors 21 on both sides and install them in place;

[0021] (6) The main electric lift controls the lifting and lowering of the annular jack 19, adjusting the annular jack 19 until its lower end rests on the soil surface. The secondary electric lift controls the pile cap, adjusting it to the top of the simulated pile and securing it to the simulated pile. After completing the above work, the various systems are adjusted to their appropriate positions and the experiment is carried out.

[0022] The soil in the simulation box 2 can be selected from soils of different soil properties, such as sand and clay, according to the actual soil, to construct the stress state of the soil. The model pile 5 selects different pile foundation forms according to the actual pile size and pile type. The simulation pile 5 determines the number and position of the pile body physical and mechanical state acquisition element 7 according to the test requirements. The horizontal loading servo motor 21 in the horizontal loading system 18 controls the loading mode through a computer, selects the horizontal cyclic force loading or monotonic continuous force loading function, and selects the displacement or force control loading magnitude. When the horizontal loading servo motor 21 uses the horizontal cyclic force loading function to work, it drives the pile cap to perform horizontal cyclic displacement. The simulated pile performs horizontal cyclic displacement within the arc slot under the action of the pile cap, and the simulated pile body is subjected to horizontal cyclic force load. When the horizontal loading servo motor 21 uses the continuous load function, the simulated pile is subjected to monotonic continuous force load.

[0023] Through the transparent plate 14, the dynamic shear friction law of the simulated pile 5 under the action of horizontal cyclic or single drop load is intuitively displayed, and the physical response of the pile body and the deformation characteristics of the soil are intuitively observed. Indoor tests of pile-soil shear contact friction under horizontal cyclic or monotonic action of different soil properties and different pile foundation forms are carried out. In order to be able to collect intuitive pile-soil contact characteristics in real time, a high-speed high-definition digital camera can be used to record the pile-soil contact friction process during the test. The soil physical and mechanical parameter acquisition element 4 and the pile body physical and mechanical parameter acquisition element 7 are connected to external computer acquisition instruments to perform data acquisition work, providing reasonable experimental comparison data for theoretical and numerical analysis verification.

[0024] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0025] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An indoor test device for pile-soil friction under horizontal cyclic / monotonous action, characterized by: It includes a reaction force system and a model box. The model box is filled with soil and multiple evenly distributed soil physical and mechanical parameter collection elements. The reaction force system is provided with a liftable loading system. The loading system is located above the model box and corresponds to it. The end face of the model box facing the loading system is an open end. One end of the model pile is installed on the loading system. The other part of the model pile is inserted into the soil and placed in the model box. The model pile is provided with multiple pile body physical and mechanical state collection elements. A horizontal displacement meter is provided on the top of the model pile. The loading system has cyclic force loading and continuous force loading functions. The loading system includes a vertical loading system and a horizontal loading system, the horizontal loading system includes a horizontal loading bracket, two horizontal loading servo motors and a horizontal loading force transmission rigid rod, the horizontal loading bracket is connected to the reaction force system and controls the lifting of the horizontal loading system through a secondary electric lift, the two horizontal loading servo motors are respectively arranged at both ends of the horizontal loading bracket, the two ends of the horizontal loading force transmission rigid rod are respectively connected to the horizontal loading servo motors at both ends, a pile cap is provided on the horizontal loading force transmission rigid rod, and one end of the model pile is installed on the pile cap, the cyclic force loading is different loading forces within a cycle time, and the loading cycle is repeated, when the horizontal loading servo motor uses the horizontal cyclic force loading function to work, it drives the pile cap to perform horizontal cyclic displacement, and the model pile body is subjected to the horizontal cyclic force load, when the horizontal loading servo motor uses the continuous load function, the model pile is subjected to the monotonic continuous force load, The vertical loading system includes a semi-annular jack, which is fixed on the reaction system, and the lower end of the semi-annular jack loads the soil surface.

2. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 1, characterized in that: The reaction system includes a reaction frame, a threaded rigid column and a rigid base. The rigid base is fixed to the bottom of the threaded rigid column. The reaction frame is connected to the upper end of the threaded rigid column and is controlled to rise and fall by a main electric lift. A jack reaction frame is fixed to the end of the reaction frame facing the model box, and the semi-annular jack is fixedly connected to the jack reaction frame.

3. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 1 or 2, characterized in that: The model box is semi-cylindrical and consists of a rigid steel plate and a transparent plate. The rigid steel plate is provided with a plurality of drainage holes and a plurality of micro grooves are arranged on the outside of the rigid plate. The model box is fixedly mounted on a rigid base through a rigid block.

4. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 3 is characterized by: The connection between the rigid steel plate and the transparent plate is provided with a water-proof rubber pad and is connected by glue.

5. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 1, 2 or 4, characterized in that: The soil body physical and mechanical parameter acquisition element is a soil pressure sensor or a piezometer or an optical fiber micro soil pressure box, and the pile body physical and mechanical state acquisition element is an FBG grating optical fiber element.

6. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 1, 2 or 4, characterized in that: The horizontal loading bracket is provided with an arc-shaped slot hole at a position corresponding to the pile cap. One end of the model pile passes through the arc-shaped slot hole and is connected to the pile cap. The model pile is cyclically displaced or continuously loaded with force in the arc-shaped slot hole.

7. The indoor testing device for pile-soil friction under horizontal cyclic / monotonous action according to claim 6 is characterized by: A rubber skin is pasted on the side of the model pile that contacts the transparent plate, and lubricating oil is applied between the model pile and the transparent plate.

8. The method for installing the indoor test device for pile-soil friction under horizontal cyclic / monotonous action according to claim 1 is characterized by: The steps are as follows, (1) According to the test requirements, determine the dimensions of the model pile, model box, and reaction system, and determine the arrangement and number of drainage holes, the number and arrangement positions of soil physical and mechanical parameter collection elements, and pile body physical and mechanical state collection elements, and lay the pile body physical and mechanical state collection elements on the pile body according to the quantity and position requirements; (2) Build a reaction system, anchor the reaction frame and the jack reaction frame into one piece by rivets, connect the reaction frame to the threaded rigid column and control the lifting and lowering by the main electric lift, adjust the reaction frame and the jack reaction frame to the highest position by the main electric lift, place the model box and fix the model box on the rigid base by the rigid block, and fix the semi-circular jack on the jack reaction frame; (3) Install the horizontal loading bracket, connect the horizontal loading bracket to the threaded rigid column and install the secondary electric lifter, and control the lifting and lowering of the horizontal loading bracket by the secondary electric lifter. First, adjust the horizontal loading bracket to the highest position; (4) laying a pile body physical and mechanical state collection element on the pile body of the model pile, laying soil in the model box and arranging soil body physical and mechanical parameter collection elements in the soil body, arranging the model pile with the pile body physical and mechanical state collection element in the soil body, and pre-treating the soil body to be tested according to the different tests and soil properties; (5) Install the horizontal loading system, install the horizontal loading servo motors on both sides of the horizontal loading bracket, install the pile cap, and connect the two ends of the horizontal loading force transmission rigid rod to the horizontal loading servo motors on both sides and install them in place; (6) The semi-circular jack is raised and lowered by the main electric lift, and the semi-circular jack is adjusted until the lower end face of the semi-circular jack is against the soil surface. The pile cap is controlled by the secondary electric lift, and the pile cap is adjusted to the top of the model pile and fixed to the model pile. Each system is adjusted to the appropriate position and the experiment is carried out.

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