High and low temperature controllable geosynthetic material interface large-size direct shear apparatus

Abstract

The utility model relates to a high and low temperature controllable geosynthetic material interface large-size direct shear apparatus, which comprises a vertical load rod, a horizontal load rod, a water tank, a lower shear box, an upper shear box, an environment temperature box, a displacement sensor and a normal stress control device, wherein the displacement sensor and the normal stress control device are arranged at the top of the environment temperature box; the force measuring ring and the temperature controller are located in the environment temperature box; the vertical load rod, the horizontal load rod, the lower shear box and the upper shear box are positioned in the environment temperature box; the normal stress control device is connected with a vertical load rod through a force measuring ring, and the other end of the vertical load rod is connected with an upper shear box; the horizontal load rod is connected with the lower shear box; the force measuring ring is also connected with the displacement sensor; and the water tank is fixedly connected with the lower shear box. Compared with the prior art, the temperature-controllable interface shear test device has the advantages of being controllable in temperature, capable of supporting interface shear tests between geosynthetics and between the geosynthetics and a soil body interface and the like.

Description

Technical Field

[0001] This utility model relates to the field of direct shear testing equipment for geotechnical materials, and in particular to a large-size direct shear tester for geosynthetic material interfaces with controllable high and low temperatures. Background Technology

[0002] Geosynthetics, including geotextiles, geomembranes, geogrids, and geonets, have become indispensable key materials in modern geotechnical engineering due to their functions such as reinforcement, seepage prevention, drainage, and protection. With the increasing complexity of geotechnical engineering, the interfacial mechanical properties of geosynthetics in projects such as slope anchoring, foundation treatment, and tunnel support have become a crucial research topic. Especially in high- and low-temperature environments such as high-temperature geothermal zones and freeze-thaw zones, the interfacial shear properties between geosynthetics and soil, and between geosynthetics themselves, directly affect the stability of engineering structures. For example, the temperature of the soil and rock surrounding geothermal well casing can reach 60-80℃, and the soil-concrete interface softens due to high temperatures, leading to a decrease in cohesion. In freeze-thaw cycles within the range of -30 to 20℃, the periodic phase transition at the geosynthetic-soil interface causes fluctuations in the friction coefficient, significantly weakening the stability of the anchored structure. The interfacial shear properties between geosynthetics directly affect the stability and functionality of the composite system. Geosynthetic interfaces are the weakest link in composite systems. Insufficient shear strength can lead to interlayer slippage in geosynthetics, causing structural instability. For example, slippage at the geomembrane-geotextile interface in landfills can tear the impermeable layer, causing leakage and pollution; failure at the geogrid-geotextile interface in reinforced soil retaining walls can lead to wall collapse. Therefore, there is an urgent need for a large-scale direct shear apparatus for geosynthetic interfaces that can be controlled at high and low temperatures to meet the needs of studying the shear mechanical properties of geosynthetic interfaces under high and low temperature conditions.

[0003] Currently, research on the interfacial shear mechanical properties of geosynthetics still faces numerous technical bottlenecks. Traditional equipment designed for analyzing the interfacial mechanical properties of geosynthetics lacks the ability to change and control temperatures over a wide range, failing to meet the needs of research on the interfacial mechanical properties of geosynthetics under low and high temperature environments. Due to the lack of such instruments, a large gap remains in this research field, hindering its effective application in practical engineering and scientific research. Therefore, developing a large-scale direct shear apparatus for geosynthetic interfaces with controllable high and low temperatures has become a key technical problem urgently needing to be solved in the current geotechnical engineering field for research on the interfacial shear mechanical properties of geosynthetics.

[0004] Chinese invention patent application publication number CN200910200536.7 discloses a large-scale direct shear apparatus for tests between geosynthetics and between geosynthetics and soil. The disclosed modified shear box solves the previous problem of not being able to simultaneously perform direct shear tests on geosynthetics and granular materials or between geosynthetics. It has a reasonable and simple structure, is easy to operate, and can be used for both rigid and flexible direct shear tests between geosynthetics and granular materials, and between geosynthetics. It ensures that the effective shear area remains constant during the test, the specimen is uniformly stressed, and the shear box adheres closely to the specimen, improving the accuracy of the test results and greatly increasing the utilization rate of the testing device. However, it lacks the ability to change and control the temperature over a wide range, and cannot meet the requirements for studying the interfacial mechanical properties of geosynthetics under low and high temperature environments.

[0005] Chinese utility model patent application publication number CN202420332715.6 discloses an intelligent temperature-controlled testing device for soil creep strength, relating to the field of frozen soil geotechnical testing. It achieves precise temperature control through a freeze-thaw cycle test chamber, solving the problems of insufficient temperature control accuracy in traditional methods and the large error in uniaxial compression tests caused by the significant difference between the final freezing temperature and the expected freezing temperature. However, it primarily focuses on the mechanical properties of geosynthetics under frozen soil conditions and does not address the study of the interfacial mechanical properties of geosynthetics under high-temperature conditions.

[0006] Chinese utility model patent application publication number CN202020483170.0 discloses a temperature-controlled multifunctional direct shear and consolidation apparatus for unsaturated soil. This apparatus can meet the requirements for direct shear and consolidation experiments of unsaturated soil under different temperatures and humidity conditions. The high and low temperature circulator and constant humidity mechanism can ensure that the experiment can be closer to the actual soil conditions and improve the accuracy of the experiment. However, it has the problem that it cannot be used to study the mechanical properties of the interface between geosynthetics.

[0007] Therefore, how to develop a large-scale direct shear apparatus for geosynthetic interfaces that allows for controllable high and low temperatures and enables the study of the mechanical properties of geosynthetic interfaces has become a technical problem that needs to be solved. Utility Model Content

[0008] The purpose of this invention is to overcome the defects of the existing technology and provide a large-size direct shear apparatus for geosynthetic material interfaces with controllable high and low temperatures.

[0009] The objective of this utility model can be achieved through the following technical solutions:

[0010] According to one aspect of this utility model, a large-size direct shear apparatus for geosynthetic interfaces with controllable high and low temperatures is provided. The apparatus includes a vertical load bar, a horizontal load bar, a water tank, a lower shear box, and an upper shear box. The apparatus further includes an ambient temperature chamber, a displacement sensor and a normal stress control device mounted on the top of the ambient temperature chamber, and a force-measuring ring and a temperature controller located inside the ambient temperature chamber. The vertical load bar, horizontal load bar, lower shear box, and upper shear box are located inside the ambient temperature chamber. The normal stress control device is connected to the vertical load bar via the force-measuring ring, and the other end of the vertical load bar is connected to the upper shear box. The horizontal load bar is connected to the lower shear box. The force-measuring ring is also connected to the displacement sensor. The water tank is fixedly connected to the lower shear box.

[0011] Preferably, the device further includes a plurality of annular pistons, which are respectively installed between the ambient temperature chamber and the vertical load bar, and between the ambient temperature chamber and the horizontal load bar.

[0012] Preferably, the external part of the drilled hole of the force measuring ring is fixed with a nut using a threaded end, and the internal part is fixed with an aluminum ring.

[0013] Preferably, the geosynthetic material specimens used in the experiment are fixed on the water tank.

[0014] Preferably, the device further includes a horizontal stop bar and a handwheel, with the upper shear box connected to the handwheel via the horizontal stop bar.

[0015] More preferably, an annular piston is installed at the connection between the ambient temperature chamber and the horizontal stop.

[0016] Preferably, the device further includes a fan, which is directly connected to the temperature controller.

[0017] More preferably, the fan is fixedly installed on the side of the ambient temperature chamber.

[0018] Preferably, the device further includes a hydraulic device connected to the horizontal load bar.

[0019] Preferably, the ambient temperature chamber also includes a door.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) In this utility model, inside the ambient temperature chamber, a horizontal load bar connects to the lower shear box and a vertical load bar connects to the upper shear box. The temperature controller can adjust the temperature required for the test. Within the temperature range of -50-200℃, it can not only conduct research on the shear mechanical properties of the interface between geosynthetics and soil under high and low temperature conditions, but also conduct research on the shear mechanical properties of the interface between geosynthetics.

[0022] 2) This utility model can handle two different types of shear tests: one is the interfacial shear test between geosynthetics, and the other is the interfacial shear test between geosynthetics and soil. It greatly improves the utilization rate of the equipment. Its vertical load bar and horizontal load bar can accurately apply the preset pressure. The displacement sensor can monitor the shear displacement and deformation data throughout the process. The clamp fixing device can effectively prevent the sample from slipping, ensuring the accuracy and stability of the test.

[0023] 3) Compared with traditional direct shear apparatus, the direct shear apparatus of this invention can realize shearing between geosynthetics and between geosynthetics and soil, and can automatically adjust the temperature during the shear test. It covers the most practical temperature variation range for engineering applications, and provides efficient technical support for the study of interfacial shear mechanical behavior between geosynthetics and between geosynthetics and soil under complex temperature environment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the straight shear device in this utility model;

[0025] Figure 2 In this utility model Figure 1 A schematic cross-sectional view of the direct shear apparatus along direction A;

[0026] Figure 3 This is a schematic diagram showing the relationship between shear stress and shear displacement at the interface between the geogrid and coral sand at different temperatures in this utility model.

[0027] Figure 4 This is a schematic diagram showing the relationship between temperature and peak shear strength under different normal stresses in this invention.

[0028] In the attached diagram, 1 is a vertical load bar, 2 is a horizontal load bar, 3 is a water tank, 4 is a force measuring ring, 5 is a displacement sensor, 6 is a normal stress control device, 7 is an ambient temperature chamber, 8 is a fan, 9 is a temperature controller, 10 is a lower shear box, 11 is an upper shear box, 12 is a horizontal stop bar, 13 is a drain pipe, 14 is a ring piston, 15 is a hydraulic device, and 16 is a handwheel. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present utility model.

[0030] This embodiment relates to a large-scale direct shear test apparatus for geosynthetic interfaces with controllable high and low temperatures. It can automatically adjust the temperature during direct shear testing and cover the most practical temperature range for engineering applications. It not only meets the temperature control requirements of -50-200℃, but also ensures that the geosynthetic interface is tested at the required temperature through a temperature control system. When the ambient chamber temperature rises, it absorbs heat from the outside air, thereby increasing the temperature of the temperature chamber. When the ambient chamber temperature falls below the set test temperature, the temperature control system automatically triggers the heating function. This can cover the most practical temperature range for engineering applications. This invention has significant advantages in the study of interfacial shear mechanical properties between geosynthetics and between geosynthetics and soil.

[0031] This invention boasts exceptional versatility, capable of handling two distinct shear tests: interfacial shear tests between geosynthetics and interfacial shear tests between geosynthetics and soil, significantly enhancing equipment utilization. Its vertical and horizontal load bars enable precise application of preset pressures, displacement sensors monitor shear displacement and deformation data throughout the test, and clamping devices effectively prevent sample slippage, ensuring the accuracy and stability of the test. This invention can be used not only for studying the interfacial shear mechanical properties of geosynthetics and soil under high and low temperature conditions, but also for studying the interfacial shear mechanical properties of geosynthetics.

[0032] like Figure 1 and Figure 2As shown, the direct shear apparatus includes a vertical load bar 1, a horizontal load bar 2, a water tank 3, a force measuring ring 4, a displacement sensor 5, a normal stress control device 6, an ambient temperature chamber 7, a fan 8, a temperature controller 9, a lower shear box 10, an upper shear box 11, a horizontal stop bar 12, a drain pipe 13, a ring piston 14, a hydraulic device 15, and a handwheel 16. The normal stress control device 6 is installed on top of the ambient temperature chamber 7, and transmits force to the ambient temperature chamber 7 by pushing the vertical load bar 1. The force measuring ring 4 is connected to the top of the vertical load bar 1, and the force is transmitted to the force measuring ring 4 through the contact between the vertical load bar 1 and the ambient temperature chamber 7. The displacement sensor 5 is connected to the force measuring ring 6. Ring 4 is connected by wires, and displacement sensor 5 is located on top of ambient temperature chamber 7, enabling the direct shear apparatus to read horizontal displacement, normal displacement, and force data in real time while applying normal stress. Water tank 3 is welded to the lower shear box 10 to form a whole, ensuring that the upper shear box 11 will not cause the water tank to move during shearing, thus ensuring the accuracy of the obtained horizontal displacement data. Fan 8 is located at the rear of ambient temperature chamber 7 for adjustment, allowing the direct shear apparatus to adjust the internal temperature of ambient temperature chamber 7 in a timely manner according to the set test temperature during the experiment. Fan 8 is directly connected to temperature controller 9 for transmitting temperature adjustment signals. Horizontal load bar 2 is directly connected to hydraulic device 15, which controls the horizontal load bar 2 and provides the required horizontal load by adjusting the hydraulic device 15. Horizontal stop bar 12 is directly connected to handwheel 16, which controls the position of horizontal stop bar 12 by rotating the handwheel 16, fixing the upper shear box 11, making the equipment more stable during the experiment, reducing experimental errors, and making the obtained experimental data more reliable.

[0033] The vertical load bar 1, water tank 3, lower shear box 10, and upper shear box 11 are all made of high-strength aluminum. High-strength aluminum has good thermal conductivity, reducing heat loss in the water tank 3 and lower shear box 10 during heat transfer, and keeping the test temperature as consistent as possible with the controlled temperature. Furthermore, high-strength aluminum maintains high strength and does not deform at high temperatures; its tensile strength and yield strength increase at low temperatures, while its toughness remains stable or slightly improved. It is less prone to deformation in low-temperature experiments, avoiding shear force measurement errors caused by structural deformation. The fan 8 is fixedly installed on the side of the ambient temperature chamber 7, including but not limited to the rear, and is controlled by the temperature controller 9. The displacement sensor 5 is connected to the opening of the force measuring ring 4, transmitting signals to the displacement sensor 5. One end of the displacement sensor 4 is embedded in the force measuring ring 4 through a drilled hole, and the force measuring ring 4 and the displacement sensor 5 are connected by wires to achieve synchronous data transmission.

[0034] The water tank 3 uses a high-strength fire-resistant and low-temperature resistant composite coating to ensure its stability in high and low temperature environments, making the geosynthetic interface shear test safer and more stable over a wide temperature range.

[0035] All components of this direct shear apparatus are made of heat-resistant materials, including cold-resistant rubber and stainless steel, which facilitates normal operation of the components in high and low temperature environments. Thermally insulated double-ring pistons 14 are installed between the ambient temperature chamber 7 and the vertical load rod 1, between the ambient temperature chamber 7 and the horizontal load rod 2, and at the connection between the ambient temperature chamber 7 and the horizontal stop rod 12. This prevents heat from dissipating from or entering the ambient temperature chamber 7 during the relative movement between the ambient temperature chamber 7 and the rods, ensuring more stable and reliable temperature data obtained from the experiment.

[0036] When conducting shear tests at the interface between geosynthetics and soil, the geosynthetic specimen is fixed to the water tank 3 with clamps, the specimen is placed in the upper shear box 11, the door of the ambient temperature chamber 7 is closed, the temperature controller 9 is activated to adjust the temperature to the required temperature, the vertical load bar 1 is driven by the normal stress control device 6 to consolidate, and after the predetermined consolidation requirements are met, the horizontal load bar 2 is driven to perform shearing. The shearing state of the specimen is monitored by the displacement sensor 5.

[0037] When conducting shear tests between geosynthetics using a direct shear apparatus, the upper shear box 11 is replaced with a solid shear box. The first geosynthetic specimen is fixed to the bottom of the solid shear box with clamps, and the second geosynthetic specimen is fixed to the water tank 3 with clamps. The door of the ambient temperature chamber 7 is closed, and the temperature controller 9 is activated to adjust the temperature to the required temperature. The vertical load bar 1 is driven by the normal stress control device 6 to consolidate the specimen. After the predetermined consolidation requirements are met, the horizontal load bar 2 is driven by the hydraulic device 15 to perform shearing. The shearing state of the specimen is monitored by the displacement sensor 5.

[0038] The force measuring ring 4 is fixed externally with a threaded end and a nut at the drilled hole, and internally with an aluminum ring. The material is high-strength aluminum alloy. This ensures that the displacement sensor 5 will not lose stability due to the movement of the force measuring ring 4 during the application of normal stress, making the horizontal displacement, normal displacement and force data obtained during the test more accurate and reliable.

[0039] Using coral sand as the experimental sample, the shear stress-shear displacement relationship at the interface between the geogrid and the coral sand was investigated at different temperatures. The specific steps included:

[0040] This experiment used a bidirectional geogrid with dimensions of 450 mm × 258 mm. The coral sand sample consisted of 13 kg of dry coral sand and 0.65 kg of pure water. The coral sand particle size used in this experiment ranged from 0.25 to 1.0 mm, with a thickness of 120 mm. The normal stresses were 50 kPa, 150 kPa, and 250 kPa. The experimental temperatures were selected as 5℃, 20℃, 60℃, and 80℃.

[0041] Coral sand is filled into the shear box in six layers and compacted with a rubber mallet to ensure the same compaction energy. The horizontal stop bar 12 is fixed to the bayonet of the upper shear box 11, so that the upper shear box 11 and the horizontal stop bar 12 are fixedly connected, and the lower shear box 10 is connected to the horizontal load bar 2.

[0042] Coral sand was loaded into the upper shear box 11, the door of the ambient temperature chamber 7 was closed, the power supply was connected, the temperature controller 9 was started, and the vertical load rod 1 was driven to consolidate. At the same time, the experimental temperature was controlled at the selected experimental temperature by the temperature controller 9. After the predetermined consolidation requirements were met, the horizontal load rod 2 was driven to shear. The shear state of the coral sand was monitored by the displacement sensor 5, and the shear stress-shear displacement relationship at the interface between the geogrid and the coral sand was recorded at different temperatures. The shear stress-shear displacement relationship at the interface between the geogrid and the coral sand at 5℃ is shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] Table 1 shows that at 5℃, the peak interfacial shear strength under normal stresses of 50 kPa, 150 kPa, and 250 kPa increases with increasing shear displacement. The peak shear strengths under different normal stresses at 5℃ are 42.44 kPa, 123.00 kPa, and 204.78 kPa, respectively. Table 2 shows the shear stress-shear displacement relationship at the interface between the geogrid and coral sand at 20℃.

[0047] Table 2

[0048]

[0049]

[0050] As shown in Table 2, when shearing with the large-size direct shear apparatus for geosynthetic interfaces of this invention, the peak shear strengths under different normal stresses at 20℃ are 45.72 kPa, 125.83 kPa and 203.05 kPa, respectively.

[0051] By comparing the experimental data, the shear stress-shear displacement relationship of coral sand within the same path range was slightly different under different normal stress conditions. The shear stress-shear displacement relationship at the interface between the geogrid and coral sand was recorded at 60℃ and 80℃, as shown in Tables 3 and 4, respectively.

[0052] Table 3

[0053]

[0054] As shown in Table 3, when shearing with the large-size direct shear apparatus for geosynthetic interfaces of this invention, the peak shear strengths under different normal stresses at 60℃ are 45.39 kPa, 132.95 kPa and 208.61 kPa, respectively.

[0055] Table 4

[0056]

[0057] As shown in Table 4, when shearing with the large-size direct shear apparatus for geosynthetic interfaces of this invention, the peak shear strengths under different normal stresses at 80℃ are 45.39 kPa, 132.95 kPa and 208.61 kPa, respectively.

[0058] Four sets of data at 5℃, 20℃, 60℃, and 80℃ were compared. The shear stress-shear displacement relationship at the interface between the geogrid and coral sand under different temperatures is shown below. Figure 3 As shown, the relationship between peak shear strength under different normal stresses at different temperatures is as follows: Figure 4 As shown.

[0059] When the temperature is within the range of 5-60℃, the peak shear strength under different normal stresses does not fluctuate much and generally shows an upward trend. However, when the temperature reaches 80℃, the peak shear strength under different normal stresses is significantly lower than that at previous temperatures. Compared with traditional direct shear apparatus, this invention verifies that the interface of geosynthetics softens under high temperature conditions, has the ability to change and control the temperature over a wide range, and can meet the requirements for studying the interfacial mechanical properties of geosynthetics under both low and high temperature environments.

[0060] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A high and low temperature controllable geosynthetic interface large-scale direct shear apparatus device, the device comprising a vertical load rod (1), a horizontal load rod (2), a water tank (3), a lower shear box (10) and an upper shear box (11), characterized in that, The device also comprises an ambient temperature box (7), a displacement sensor (5) and a normal stress control device (6) installed on the top of the ambient temperature box (7), and a load cell (4) and a temperature controller (9) located inside the ambient temperature box (7); the vertical load rod (1), the horizontal load rod (2), the lower shear box (10) and the upper shear box (11) are located inside the ambient temperature box (7); the normal stress control device (6) is connected with the vertical load rod (1) through the load cell (4), and the other end of the vertical load rod (1) is connected with the upper shear box (11); the horizontal load rod (2) is connected with the lower shear box (10); the load cell (4) is also connected with the displacement sensor (5); and the water tank (3) is fixedly connected with the lower shear box (10).

2. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The device also comprises a plurality of annular pistons (14), and the plurality of annular pistons (14) are respectively installed between the ambient temperature box (7) and the vertical load rod (1) and between the ambient temperature box (7) and the horizontal load rod (2).

3. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The load cell (4) is fixed by a threaded hole and a nut outside the drilled hole and is fixed by an aluminum sheet ring inside the drilled hole.

4. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The geosynthetic material test specimen for testing is fixed on the water tank (3).

5. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The device also comprises a horizontal rod (12) and a hand wheel (16), and the upper shear box (11) is connected with the horizontal rod (12) and the hand wheel (16).

6. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 5, wherein, An annular piston (14) is installed at the connection between the ambient temperature box (7) and the horizontal rod (12).

7. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The device also comprises a fan (8), and the fan (8) is directly connected with the temperature controller (9).

8. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 7, wherein, The fan (8) is fixedly installed on the side of the ambient temperature box (7).

9. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The device also comprises a hydraulic device (15) connected with the horizontal load rod (2).

10. The high and low temperature controllable geosynthetic interface large-scale direct shear apparatus of claim 1, wherein, The ambient temperature box (7) also comprises a box door.

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