Geosynthetic material drawing device with controllable boundary conditions and test method

Abstract

The invention discloses a geosynthetic material drawing device capable of controlling boundary conditions and a test method. The drawing device comprises a model box system, a top air bag, a steel frame counter-force system, a vertical loading system, a lateral supporting system, a horizontal loading system and a comprehensive control system. According to the geosynthetic drawing device with the controllable boundary conditions, the boundary conditions of the drawing box can be controlled and adjusted in real time, lateral stress and displacement can be accurately controlled, simulation of interaction of reinforcement and soil interfaces in a complex stress state is achieved, and the mutual influence degree between different reinforcement layers can be reflected; the drawing device can more truly reflect the actual condition of the reinforced soil structure, and is suitable for the requirements of different types of structures, so that the reliability and applicability of test results are improved.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical material testing, and in particular to a geosynthetic material pulling device with controllable boundary conditions and a testing method. Background Art

[0002] Geosynthetics such as geogrids and geotextiles play an increasingly important role in the construction of transportation infrastructure. The interaction mechanism and interface characteristics between them and the soil are key factors in engineering design and analysis. At present, indoor pull-out tests are the main means to study this interaction characteristic. However, the existing pull-out test device can only impose rigid boundary conditions on the lateral boundaries during the test. But this boundary condition does not reflect the actual working conditions in reinforced soil structures. Therefore, the traditional pull-out device cannot truly simulate the engineering situation, resulting in deviations between the test results and the actual situation. On the other hand, the actual boundary conditions and stress states of different types of reinforced soil structures may also be different. However, the existing device cannot adjust each boundary condition according to demand, and it is difficult to simulate a variety of actual engineering situations. Summary of the invention

[0003] The purpose of the present invention is to provide a geosynthetics pulling device and a test method with controllable boundary conditions in view of the problems existing in the prior art.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A geosynthetics pulling device with controllable boundary conditions, comprising a model box system, a plurality of first slots are provided on the side of the model box system, and a clamp is arranged near the first slots, the clamp is used to fix the geosynthetics passing through the first slots; The model box system is arranged with an opening above and a top airbag is arranged at the opening. A steel frame reaction force system is arranged above the model box system. The steel frame reaction force system is provided with a plurality of vertical loading systems toward the model box system. The vertical loading systems apply vertical loading force to the top airbag. A lateral support system is provided inside the model box system, and the lateral support system includes a metal stacked ring frame and a lateral airbag which can be replaced with each other to provide adjustable boundary conditions, and the lateral airbag is connected to a pressure controller through a catheter; A horizontal loading system is also provided on one side of the exterior of the model box system. The horizontal loading system is provided with a height-adjustable horizontal actuator. The horizontal actuator is used to connect one of the geosynthetics and apply a pulling force or pulling rate. It also includes an integrated control system, which includes at least control and data monitoring of the pressure of the side airbags, the pressure of the top airbags, the pulling force and displacement of the horizontal actuator, and the vertical loading force and displacement of the vertical loading system.

[0005] The geosynthetics pulling device with controllable boundary conditions can not only control and adjust the boundary conditions of the pulling box in real time, but also accurately control the lateral stress and displacement, realize the simulation of the interaction between the reinforcement and soil interface under complex stress states, and reflect the degree of mutual influence between different reinforcement layers. The pulling device can more realistically reflect the actual situation of the reinforced soil structure, adapt to the needs of different types of structures, thereby improving the reliability and applicability of the test results, which is of great significance to related scientific research and engineering practice.

[0006] The horizontal actuator can adjust the height relative to the model box system so as to better correspond to the geosynthetics and ensure that it can pull the geosynthetics horizontally; the horizontal actuator is used to apply a constant pulling force or a constant pulling rate and can accurately control the pulling force and speed.

[0007] The lateral support system can flexibly adjust the required boundary conditions according to the test requirements to achieve simulation of different working conditions such as zero displacement, constant pressure, and constant stiffness; the lateral airbags are connected by catheters, which can adjust the lateral stress according to actual needs and provide flexible boundary conditions; the metal stacked ring frame can provide a boundary with restrictive conditions, which is different from the limitation directly using the model box frame.

[0008] Furthermore, the model box system includes a box bottom plate, on which a first baffle and a second baffle are arranged opposite to each other, the first baffle and the second baffle are respectively provided with the first slot, and the box bottom plate is also provided with a pair of transparent baffles connected to the first baffle and the second baffle.

[0009] Furthermore, the horizontal actuator is provided on the outer side of the first baffle plate, and the first slot is provided in the middle of the first baffle plate; the first slots are provided at the upper and lower parts of the second baffle plate respectively, and a support platform is provided on the outer side of the second baffle plate, and the clamp is provided on the support platform.

[0010] In some embodiments, a pair of guard plates are further provided on the inner side of the first baffle at the first slot, the pair of guard plates are respectively provided on the upper and lower sides of the first slot, and the pair of guard plates extend inwardly through the lateral support system.

[0011] Furthermore, the steel frame reaction system includes a reaction frame erected on the model box system, and the vertical loading system includes a plurality of vertical actuators installed below the reaction frame. The output end of the vertical actuator is provided with a loading pad, and the loading pad abuts against the top airbag.

[0012] Furthermore, the horizontal loading system includes a column arranged on one side of the model box system, the column is provided with a liftable horizontal support plate, the horizontal actuator is arranged on the horizontal support plate, and the output end of the horizontal actuator is connected to a clamp for clamping the geosynthetics.

[0013] Furthermore, the lateral airbag includes a plurality of airbag units, adjacent airbag units are connected by conduits and are provided with gaps for geosynthetics to pass through, at least one of the airbag units is also connected to an air compressor via a conduit and is connected to a pressure gauge; fillers are provided in the area maintained by the lateral airbags and the top airbags.

[0014] Furthermore, the top airbag is arranged at the upper opening of the metal stacking ring frame, and fillers are arranged in the metal stacking ring frame; the metal stacking ring frame includes a plurality of stacked metal stacking rings, wherein at least one pair of the metal stacking rings has a second groove at its mating surface.

[0015] A test method for a geosynthetics pulling device with controllable boundary conditions, the test method comprising the following steps: Test preparation, including at least the preparation of filler, geosynthetics and pulling device; Setting the boundary conditions of the test, including at least setting the flexible boundary condition of the side airbag only, setting the limited displacement boundary condition of the metal stacked ring frame only, and setting the rigid boundary condition of neither the side airbag nor the metal stacked ring frame; Filling the model, placing the filler layer by layer in the model box system, and laying a layer of geosynthetics from the first groove every time the filler is compacted to the height of the first groove; The fixture and loading system are prepared, the geosynthetics extending out of the model box system are placed flatly on the fixture, the height of the fixture is ensured to be consistent with the height of the geosynthetics, and the geosynthetics are clamped and fixed, wherein one layer of the geosynthetics is connected to the horizontal actuator after being clamped by the fixture; the top airbag is arranged on the topmost filler, and then the vertical loading system is installed, and the output end of the vertical loading system acts on the top airbag; Preloading, setting the applied vertical loading force, the pressure of the top airbag or the stress of the side airbag in the integrated control system, gradually applying the vertical loading force, and monitoring the pressure and displacement changes in real time; The pull-out test is performed by setting the horizontal pull-out force and pull-out rate applied by the horizontal actuator in the integrated control system, starting the horizontal actuator, gradually loading, and recording the pull-out force, displacement, and strain data until a predetermined test termination condition is reached; Disassembly and cleaning: dismantle the vertical loading system and the horizontal loading system, dismantle the model box system, remove fillers and geosynthetics, and clean up the test site.

[0016] Furthermore, under the flexible boundary condition, the filler is filled in the area between the side airbag, the top airbag and a pair of transparent baffles of the model box system; under the limited displacement boundary condition, the filler is filled in the area enclosed by the metal stacking ring frame and the top airbag; under the rigid boundary condition, the filler is directly filled in the area enclosed by the first baffle, the second baffle, the transparent baffle and the top airbag of the model box system; the geosynthetics are arranged in at least three layers, and the middle layer of geosynthetics is connected to the horizontal actuator.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The geosynthetics drawing device with controllable boundary conditions can not only control and adjust the boundary conditions of the drawing box in real time, but also accurately control the lateral stress and displacement, realize the simulation of the interaction between the reinforcement and soil interface under complex stress state, and reflect the degree of mutual influence between different reinforcement layers; 2. The drawing device can more realistically reflect the actual situation of the reinforced soil structure, adapt to the needs of different types of structures, thereby improving the reliability and applicability of the test results, which is of great significance to relevant scientific research and engineering practice; 3. The horizontal actuator can be relative to the The model box system adjusts the height to better correspond to the geosynthetics and ensure that it can pull the geosynthetics horizontally; the horizontal actuator is used to apply a constant pulling force or a constant pulling rate, and can accurately control the pulling force and speed; 4. The lateral support system can flexibly adjust the required boundary conditions according to the test requirements to achieve simulation of different working conditions such as zero displacement, constant pressure, and constant stiffness; each lateral airbag is connected by a catheter, which can adjust the lateral stress according to actual needs and provide flexible boundary conditions; the metal stacked ring frame can provide a boundary with restrictive conditions, which is different from the limitation directly using the model box frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an overall schematic diagram of a geosynthetics pulling device with controllable boundary conditions according to the present invention; Figure 2 This is a schematic diagram of the metal stacked ring frame provided by the present invention; Figure 3 A schematic diagram of the airbag connection method provided by the present invention; Figure 4 A schematic diagram of a first baffle provided by the present invention; Figure 5 A schematic diagram of a second baffle provided by the present invention; Figure 6A schematic diagram of equipment installation under flexible boundary conditions provided by the present invention; Figure 7 A schematic diagram of equipment installation under the finite displacement boundary conditions provided by the present invention; Figure 8 This is a schematic diagram of equipment installation under rigid boundary conditions provided by the present invention; Fig. 9 Schematic diagram of shear / tensile deformation under different boundary conditions; In the figure: 1. column; 2. horizontal actuator; 3. front clamp; 4. catheter; 5. front lateral airbag; 6. pressure gauge; 7. reaction frame; 8. top airbag; 9. loading pad; 10. vertical actuator; 11. second baffle; 12. rear clamp; 13. rear lateral airbag; 14. lower geosynthetics; 15. middle geosynthetics; 16. upper geosynthetics; 17. metal stacking ring frame; 1701. metal stacking ring; 1702. second slot; 18. first baffle; 19. guard plate; 20. first slot. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0021] like Figures 1 to 8 As shown, a geosynthetic material pulling device with controllable boundary conditions includes a model box system, a plurality of first slots 20 are provided on the side of the model box system, and a clamp arranged near the first slots 20, including a front clamp 3 and a rear clamp 12, and the clamp is used to fix the geosynthetic material passing through the first slots 20; The model box system is arranged with an opening above and a top airbag 8 is arranged at the opening. A steel frame reaction force system is arranged above the model box system. The steel frame reaction force system is provided with a plurality of vertical loading systems toward the model box system. The vertical loading systems apply vertical loading force to the top airbag 8. The model box system is provided with a lateral support system inside, and the lateral support system includes a replaceable metal stacked ring frame 17 and a lateral airbag to provide adjustable flexibility or rigidity or limited boundary conditions, and the lateral airbag is connected to a pressure controller through a catheter; A horizontal loading system is also provided on one side of the exterior of the model box system. The horizontal loading system is provided with a height-adjustable horizontal actuator 2. The horizontal actuator 2 is used to connect one of the geosynthetics and apply a constant pulling force or a constant pulling rate. It also includes an integrated control system, which includes at least control and data monitoring of the pressure of the side airbags, the pressure of the top airbags, the pulling force and displacement of the horizontal actuator, and the vertical loading force and displacement of the vertical loading system.

[0022] The geosynthetics pulling device with controllable boundary conditions can not only control and adjust the boundary conditions of the pulling box in real time, but also accurately control the lateral stress and displacement, realize the simulation of the interaction between the reinforcement and soil interface under complex stress states, and reflect the degree of mutual influence between different reinforcement layers. The pulling device can more realistically reflect the actual situation of the reinforced soil structure, adapt to the needs of different types of structures, thereby improving the reliability and applicability of the test results, which is of great significance to related scientific research and engineering practice.

[0023] The steel frame reaction system is rigidly connected to the model box to provide stable support for the entire device and ensure the stability of the vertical force applied by the vertical loading system to the specimen. The vertical loading system is provided with a plurality of vertical actuators arranged in parallel, and contacts the top of the specimen through the top airbag, and can independently apply vertical force to ensure that the specimen is evenly stressed and avoid local stress concentration.

[0024] The horizontal actuator 2 can adjust the height relative to the model box system so as to better correspond to the geosynthetics and ensure that it can pull the geosynthetics horizontally; the horizontal actuator is used to apply a constant pulling force or a constant pulling rate and can accurately control the pulling force and speed.

[0025] The lateral support system can flexibly adjust the required boundary conditions according to the test requirements to achieve simulation of different working conditions such as zero displacement, constant pressure, and constant stiffness; the lateral airbags are connected by catheters, which can adjust the lateral stress according to actual needs and provide flexible boundary conditions; the metal stacked ring frame can provide a boundary with restrictive conditions, which is different from the limitation directly using the model box frame.

[0026] Furthermore, the model box system includes a box bottom plate, on which a first baffle 18 and a second baffle 11 are arranged opposite to each other, the first baffle 18 and the second baffle 11 are respectively provided with the first groove 20, and the box bottom plate is also provided with a pair of transparent baffles connected to the first baffle 18 and the second baffle 11.

[0027] The model box system adopting this structure has a simple structure and is easy to install and disassemble. Specifically, the metal box frame is rigidly connected to the box bottom plate, the front baffle (the first baffle 18), the rear baffle (the second baffle 11), the left baffle and the right baffle (a pair of transparent baffles) by bolts. The pair of transparent baffles is organic glass or tempered glass, which is convenient for directly observing the internal situation of the model box from the outside during the test and facilitating the observation of the deformation process of the sample.

[0028] Furthermore, the horizontal actuator 2 is provided on the outer side of the first baffle 18, and the first slot 20 is provided in the middle of the first baffle 18; the first slots 20 are respectively provided on the upper and lower sides of the second baffle 11, and a support platform is provided on the outer side of the second baffle 11, and the rear clamp 12 is provided on the support platform.

[0029] The first slot 20 is a long strip opening that allows the geosynthetics to pass through so that the external clamps can clamp them. The front clamp 3 outside the first baffle 18 is connected to the horizontal actuator 2, and the rear clamp 12 outside the second baffle 11 is supported and fixed by the support platform to ensure that the clamp can clamp the geosynthetics horizontally and stably. The number of clamps is the same as the number of the first slots, and the height of the clamps is also corresponding to the first slots.

[0030] The clamp is designed to be adjustable to accommodate geosynthetics of varying thicknesses, and is equipped with rubber pads inside to increase friction and ensure that the material does not slip during pulling.

[0031] In some embodiments, a pair of guard plates 19 are further provided on the inner side of the first baffle 18 at the first slot 20 , and the pair of guard plates 19 are respectively provided on the upper and lower sides of the first slot, and the pair of guard plates 19 extend inwardly through the lateral support system.

[0032] The cross section of the guard plate 19 is L-shaped, one side is bolted to the first baffle 18, and the other side extends inward in parallel; the gap between the pair of guard plates 19 corresponds to the first slot on the first baffle 18, and the geosynthetics can extend between the pair of guard plates 19 in the direction of the first slot. The advantage of this arrangement is that it can prevent the stress concentration of the filler at the slot, avoid the negative impact of the filler on the geosynthetics in the middle layer, and facilitate the horizontal actuator to effectively pull the geosynthetics at this location. When using lateral airbags, it can also prevent the lateral airbags from compressing the geosynthetics at this location to avoid affecting horizontal pulling.

[0033] Furthermore, the steel frame reaction system includes a reaction frame 7 erected on the model box system, and the vertical loading system includes a plurality of vertical actuators 10 installed below the reaction frame 7, and a loading pad 9 is provided at the output end of the vertical actuator 10, and the loading pad 9 abuts against the top airbag 8.

[0034] A plurality of vertical actuators 10 arranged in parallel cooperate with the setting of the loading pad 9 and contact the top of the filler through the top airbag 8, which can not only independently apply vertical force but also ensure that the specimen is evenly stressed and avoid local stress concentration.

[0035] Furthermore, the horizontal loading system includes a column 1 arranged on one side of the model box system, the column 1 is provided with a liftable horizontal support plate, the horizontal actuator 2 is arranged on the horizontal support plate, and the output end of the horizontal actuator 2 is connected to a clamp for clamping geosynthetics.

[0036] The horizontal loading system is connected to the model box system through the height-adjustable vertical metal column and the horizontal support plate. The column 1 is made of high-strength steel to provide overall structural support for the horizontal loading system. The bottom of the column 1 is fixed to the ground, and can also be directly installed on the bottom plate of the box to prevent tilting or displacement when force is applied.

[0037] One end of the horizontal support plate is connected to the column 1 through a locking bolt, and the locking height position can be adjusted as needed. The other end of the horizontal support plate abuts against the outer wall of the first baffle, and a sliding groove can be set on the outer wall to support the horizontal support plate and perform sliding limitation and guidance.

[0038] Further, such as Figure 5 As shown, the lateral airbag includes a plurality of airbag units, adjacent airbag units are connected by conduits and are provided with gaps for geosynthetics to pass through, at least one of the airbag units is also connected to an air compressor by a conduit and is connected to a pressure gauge; fillers are provided in the area maintained by the lateral airbags and the top airbags.

[0039] The lateral airbags include a front lateral airbag 5 and a rear lateral airbag 13. The front lateral airbag 5 is provided with two upper and lower airbag units, and the rear lateral airbag 13 is provided with three upper, middle and lower airbag units, so that two upper and lower gaps can be formed, respectively corresponding to the upper and lower layers of geosynthetics.

[0040] The front side airbag 5 and the rear side airbag 13 can also be connected by a conduit so as to be inflated by an air compressor, or they can be connected to air compressors separately; the airbag material needs to have high strength and wear resistance to withstand multiple tests, and the length and curvature of the conduit need to be designed to avoid affecting the reaction speed of the airbag. The pressure gauge can monitor the pressure in the airbag in real time to ensure that the airbag is always within the set pressure range to ensure the stability and reliability of the test.

[0041] In some embodiments, an upper baffle is further provided on the inner upper edges of the first baffle 18 and the second baffle 11, and the upper baffle is arranged corresponding to the area where the side airbags are arranged, so that when the side airbags are inflated, the upper baffle can form an upper limit to prevent the side airbags from expanding to the outside of the model box system; at this time, the top front bag is arranged in the interval enclosed by the upper baffle, which also has a limiting effect on the circumference of the top airbag.

[0042] Furthermore, the top airbag is arranged at the upper opening of the metal stacking ring frame 17, and filler is arranged inside the metal stacking ring frame 17; the metal stacking ring frame 17 includes a plurality of stacked metal stacking rings 1701, wherein at least one pair of the metal stacking rings 1701 has a second groove 1702 at the mating surface to facilitate the passage of geosynthetics and also to allow a pair of the guard plates 19 to pass through.

[0043] The metal stacking ring 1701 is made of high-strength metal material. The front end of the metal stacking ring 1701 is provided with the second slot 1702 at the height of the middle layer of geosynthetics, that is, corresponding to the first slot on the first baffle 18. Lubricating oil is applied between each layer of the metal stacking ring 1701 to reduce resistance. Each layer of the metal stacking ring 1701 can have relative slip during the test, and can achieve single shear deformation, such as Fig. 9 shown.

[0044] A test method for a geosynthetics pulling device with controllable boundary conditions, the test method comprising the following steps: Step 1: Test preparation, including at least the preparation of filler, geosynthetics and pulling device; Specifically, it includes necessary fillers, geosynthetics, such as lower geosynthetics 14, middle geosynthetics 15 and upper geosynthetics 16, as well as lubricating oil, cleaning tools, etc., and measuring instruments such as calipers and levels are prepared according to test requirements.

[0045] Step 2: installing the pulling device and setting the boundary conditions of the test, including at least setting the flexible boundary conditions of the side airbag only, setting the limited displacement boundary conditions of the metal stacked ring frame only, and setting neither the side airbag nor the metal stacked ring frame with rigid boundary conditions; Specifically, fix the metal box frame at a predetermined position to ensure that it is level and stable. Use a level to confirm that the box bottom plate is firmly connected to the model box frame. Then, install the first baffle 18 on the front side, the second baffle 11 on the rear side, and a pair of transparent baffles on the left and right sides in sequence and fasten them with bolts. According to the boundary conditions selected in the experiment, perform the corresponding equipment installation: Case 1-Flexible boundary conditions: If Figure 6 As shown, only the front lateral airbag 5 and the rear lateral airbag 13 are installed on the side wall of the model box. The installation position of each lateral airbag needs to be designed according to the predetermined pressure distribution to ensure that the connection between the lateral airbag and the model box frame is stable; the pressure controller of the lateral airbag should be connected to the airbag and ensure that the pressure can be adjusted independently and accurately during the experiment to simulate the stress distribution under the fully flexible boundary condition; the installation of the lateral airbag should ensure that it can expand evenly when under pressure and can provide appropriate lateral support under different loading conditions. Case 2-Limited displacement boundary condition: Figure 7 As shown, only metal stacking rings 1701 are installed on the four side walls of the model box. The function of the metal stacking ring is to simulate the constraint boundary in the simple shear test, maintain the relative stability of the boundary, and prevent excessive deformation. Its installation needs to ensure that the second slot 1702 of the metal stacking ring is at the height of the middle layer of geosynthetics 15, so that there is no contact or uniform contact between the metal stacking ring and the geosynthetics to avoid unnecessary friction or interference. Case 3-Rigid boundary conditions: Figure 8 As shown, neither the front lateral airbag 5 nor the rear lateral airbag 13 is installed, nor is the metal stacking ring 1701 installed. The side walls of the model box remain completely rigid and can provide stable lateral constraints. In this configuration, the lateral pressure on the geosynthetics is completely provided by the side walls of the model box, ensuring that the boundaries will not undergo any deformation or displacement. The structural strength of the model box should be able to withstand high-intensity loading without any deformation.

[0046] After completing the above installation, carefully check each connection point to ensure that the model box frame, each baffle, side airbag, metal stacking ring and other equipment components are installed firmly and correctly. In particular, check whether the connection of each airbag system is tight to ensure that each airbag can expand and apply pressure normally during the test. The installation of the metal stacking ring should ensure that it does not deviate to prevent affecting the test results. If necessary, perform a low-pressure test to check whether the connection between the components is stable and whether each side airbag can work as expected.

[0047] Step 3: Filling the model, placing the filler layer by layer in the model box system, and laying a layer of geosynthetics from the first slot whenever the filler is compacted to the height of the first slot; Specifically, the prepared fillers are placed layer by layer in the model box or the lateral airbag enclosure area or the metal stacking ring frame 17, and the fillers are compacted to the specified compaction degree and height; each layer of filler should be compacted evenly and the compaction surface should be kept flat to ensure the reliability of the test; when the fill height reaches the opening height of each first slot on the first and second baffles, the geosynthetics are laid: ensure that one end of the geosynthetics passes through the first slot, such as the first slot at the upper part of the second baffle and the first slot at the lower part, and the extended length should be able to be completely clamped by the clamp, and wrinkles or damage should be avoided during the laying process.

[0048] Step 4: Prepare the fixture and loading system, place the geosynthetics extending out of the model box system flatly on the fixture, cut off the excess geosynthetics so that it just fits the size of the fixture and is moderately tight; ensure that the height of the fixture is consistent with the height of the geosynthetics to ensure the overall fixed connection of the pulling system; clamp and fix the geosynthetics, and the middle layer of geosynthetics is connected to the horizontal actuator after being clamped by the fixture; set the top airbag on the topmost layer of filler, and then install the vertical loading system, and the output end of the vertical loading system acts on the top airbag; ensure that the vertical actuator is firmly connected to avoid displacement during loading.

[0049] Step 5: preloading, setting the applied vertical loading force, the pressure of the top airbag or the stress of the side airbag in the integrated control system, gradually applying the vertical loading force, and monitoring the pressure and displacement changes in real time; Specifically, set the data acquisition frequency to ensure that all parameters meet the test requirements; gradually apply vertical stress to the top airbag 8 and the vertical actuator 10 until the set value is reached; for situation 1, apply pressure to the front side airbag 5 and the rear side airbag 13 at the same time until the set value is reached; during the preloading process, monitor the pressure and displacement changes in real time to ensure system stability.

[0050] Step 6: Pull-out test: set the horizontal pull-out force and pull-out rate applied by the horizontal actuator in the integrated control system, start the horizontal actuator, load gradually, and record the pull-out force, displacement and strain data until the predetermined test termination condition is reached; ensure that various parameters during the test are kept within the set range. During the test, monitor and record the pull-out force, displacement, strain and other data in real time until the predetermined test termination condition is reached, record the final data and save it.

[0051] Step 7: Disassembly and cleaning: dismantle the vertical loading system and the horizontal loading system, dismantle the model box system, remove fillers and geosynthetics, and clean up the test site.

[0052] Specifically, after the test is completed, first cancel the horizontal pulling force to ensure that the geosynthetics are separated from the fixture smoothly, cancel the vertical pressure to separate the vertical loading system from the model box, turn off the loading system device, disassemble the model box, remove the filler and geosynthetics, carefully check the equipment to ensure that there is no damage, keep maintenance records, clean up the test site, dispose of all waste materials, and ensure that the site is clean.

[0053] Furthermore, under the flexible boundary condition, the filler is filled in the area between the side airbag, the top airbag and a pair of transparent baffles of the model box system; under the limited displacement boundary condition, the filler is filled in the area enclosed by the metal stacking ring frame and the top airbag; under the rigid boundary condition, the filler is directly filled in the area enclosed by the first baffle, the second baffle, the transparent baffle and the top airbag of the model box system; the geosynthetics are arranged in at least three layers, and the middle layer of geosynthetics is connected to the horizontal actuator.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A geosynthetics pulling device with controllable boundary conditions, characterized in that: It comprises a model box system, wherein a plurality of first slots are arranged on the side of the model box system, and a clamp is arranged near the first slots, and the clamp is used to fix the geosynthetics passing through the first slots; The model box system is arranged with an opening above and a top airbag is arranged at the opening. A steel frame reaction force system is arranged above the model box system. The steel frame reaction force system is provided with a plurality of vertical loading systems toward the model box system. The vertical loading systems apply vertical loading force to the top airbag. The model box system is provided with a lateral support system inside, and the lateral support system includes a metal stacked ring frame and a lateral airbag which can be replaced with each other to provide adjustable boundary conditions, and the lateral airbag is connected to a pressure controller through a catheter; A horizontal loading system is also provided on the external side of the model box system. The horizontal loading system is provided with a height-adjustable horizontal actuator. The horizontal actuator is used to connect one of the geosynthetics and apply a pulling force or pulling rate. It also includes an integrated control system, which includes at least control and data monitoring of the pressure of the side airbags, the pressure of the top airbags, the pulling force and displacement of the horizontal actuator, and the vertical loading force and displacement of the vertical loading system.

2. The geosynthetics pulling device with controllable boundary conditions according to claim 1, characterized in that: The model box system includes a box bottom plate, on which a first baffle and a second baffle are arranged opposite to each other, the first baffle and the second baffle are respectively provided with the first slot, and the box bottom plate is also provided with a pair of transparent baffles connected to the first baffle and the second baffle.

3. The geosynthetics pulling device with controllable boundary conditions according to claim 2, characterized in that: The horizontal actuator is provided on the outer side of the first baffle plate, and the first slot is provided in the middle of the first baffle plate; the first slots are provided at the upper and lower parts of the second baffle plate, respectively, and a support platform is provided on the outer side of the second baffle plate, and the clamp is provided on the support platform.

4. The geosynthetics pulling device with controllable boundary conditions according to claim 2, characterized in that: A pair of guard plates are also provided on the inner side of the first baffle at the first slot, the pair of guard plates are respectively provided on the upper and lower sides of the first slot, and the pair of guard plates extend inwardly through the lateral support system.

5. The geosynthetics pulling device with controllable boundary conditions according to claim 1, characterized in that: The steel frame reaction system includes a reaction frame erected on the model box system, and the vertical loading system includes a plurality of vertical actuators installed below the reaction frame. The output end of the vertical actuator is provided with a loading pad, and the loading pad abuts against the top airbag.

6. The geosynthetics pulling device with controllable boundary conditions according to claim 1, characterized in that: The horizontal loading system comprises a column arranged on one side of the model box system, the column is provided with a liftable horizontal support plate, the horizontal actuator is arranged on the horizontal support plate, and the output end of the horizontal actuator is connected to a clamp for clamping geosynthetics.

7. The geosynthetics pulling device with controllable boundary conditions according to claim 1, characterized in that: The lateral airbag includes a plurality of airbag units, adjacent airbag units are connected by conduits and are provided with gaps for geosynthetics to pass through, at least one of the airbag units is also connected to an air compressor by a conduit and is connected to a pressure gauge; fillers are provided in the area maintained by the lateral airbags and the top airbags.

8. The geosynthetics pulling device with controllable boundary conditions according to claim 1, characterized in that: The top airbag is arranged at the upper opening of the metal stacking ring frame, and fillers are arranged in the metal stacking ring frame; the metal stacking ring frame comprises a plurality of stacked metal stacking rings, wherein a second groove is arranged at the mating surface of at least one pair of the metal stacking rings.

9. A test method for a geosynthetics pulling device with controllable boundary conditions according to any one of claims 1 to 8, characterized in that: The test method comprises the following steps: Test preparation, including at least the preparation of filler, geosynthetics and pulling device; Setting the boundary conditions of the test, including at least setting the flexible boundary condition of the side airbag only, setting the limited displacement boundary condition of the metal stacked ring frame only, and setting the rigid boundary condition of neither the side airbag nor the metal stacked ring frame; Filling the model, placing the filler layer by layer in the model box system, and laying a layer of geosynthetics from the first groove every time the filler is compacted to the height of the first groove; The fixture and loading system are prepared, the geosynthetics extending out of the model box system are placed flatly on the fixture, the height of the fixture is ensured to be consistent with the height of the geosynthetics, and the geosynthetics are clamped and fixed, wherein one layer of the geosynthetics is connected to the horizontal actuator after being clamped by the fixture; the top airbag is arranged on the topmost filler, and then the vertical loading system is installed, and the output end of the vertical loading system acts on the top airbag; Preloading, setting the applied vertical loading force, the pressure of the top airbag or the stress of the side airbag in the integrated control system, gradually applying the vertical loading force, and monitoring the pressure and displacement changes in real time; The pull-out test is performed by setting the horizontal pull-out force and pull-out rate applied by the horizontal actuator in the integrated control system, starting the horizontal actuator, gradually loading, and recording the pull-out force, displacement, and strain data until a predetermined test termination condition is reached; Disassembly and cleaning: dismantle the vertical loading system and the horizontal loading system, dismantle the model box system, remove fillers and geosynthetics, and clean up the test site.

10. A test method for a geosynthetics pulling device with controllable boundary conditions according to claim 9, characterized in that: Under the flexible boundary condition, the filler is filled in the area between the side airbag, the top airbag and a pair of transparent baffles of the model box system; under the limited displacement boundary condition, the filler is filled in the area enclosed by the metal stacking ring frame and the top airbag; under the rigid boundary condition, the filler is directly filled in the area enclosed by the first baffle, the second baffle, the transparent baffle and the top airbag of the model box system; the geosynthetics are arranged in at least three layers, and the middle layer of geosynthetics is connected to the horizontal actuator.

Images