Testing device for measuring moisture characteristic curve of geotechnical cloth

Abstract

The utility model provides a testing device for measuring a moisture characteristic curve of geotechnical cloth, which comprises a support main body, and a cylinder body and a separated cylinder body are arranged on the support main body, wherein the height of the cylinder body can be freely adjusted; the upper part and the lower part of the barrel are provided with water outlet holes and are connected with a multi-port water valve, and the upper part is also provided with a water adding hole; the separated cylinder comprises an upper cylinder and a lower cylinder which are connected through a flange, an argil plate is horizontally arranged in the lower cylinder, the air inlet value of the argil plate is greater than that of a geotechnical cloth sample, the edge of the argil plate is hermetically connected with the side wall of the lower cylinder, and the upper part and the lower part of the separated cylinder are provided with water outlet holes and are connected with a single-port water valve; the separated cylinder upper single-port water valve is communicated with the cylinder upper multi-port water valve through a water pipe, and the lower single-port water valve is communicated with the lower multi-port water valve. The device is simple in composition and convenient to construct, can simultaneously test a plurality of samples, effectively solves the problem of influence of environment temperature on test results, and can simultaneously test moisture characteristic curves of geotechnical cloth under various working conditions.

Description

Technical Field

[0001] The utility model belongs to the technical field of geotextile unsaturated characteristic measurement, in particular to a test device for measuring a geotextile moisture characteristic curve. Background Art

[0002] Geotextile is a kind of geosynthetic material made of synthetic fibers by needle punching or weaving. Its main functions include isolation, filtration, drainage, reinforcement and protection. It is widely used in highway, railway, hydraulic and construction projects. In the construction of the capping cover layer of the landfill, geotextile can be used as a part of the cover layer to play an anti-seepage role. Specifically, when the cover layer contains a geotextile structure lined with fine-grained soil, a capillary barrier effect will be formed at the contact surface between the fine-grained soil and the geotextile. This effect will limit the infiltration of water from the fine-grained soil to the geotextile, so that most of the water is stored in the fine-grained soil, thereby reducing the production of leachate in the garbage. The capillary barrier effect of the contact surface between fine-grained soil and geotextile is closely related to the unsaturated hydraulic properties of the geotextile. Specifically, under low water content (or high matrix suction) conditions, the permeability coefficient of the geotextile is smaller than that of the fine-grained soil. Therefore, when water infiltrates from the fine-grained soil to the geotextile, it will be blocked by the geotextile, that is, the capillary barrier effect is formed. Under high water content (or low matrix suction) conditions, the permeability coefficient of geotextile is greater than that of fine-grained soil. At this time, when water infiltrates from fine-grained soil to geotextile, it will not be blocked by the geotextile. At this time, the capillary blocking effect is in a failed state, and water can easily infiltrate into the garbage under the cover layer. From the above, it can be seen that in order to ensure the actual anti-seepage effect of the cover layer, it is necessary to form a good capillary blocking effect at the contact surface between fine-grained soil and geotextile. The moisture characteristic curve is a curve that describes the relationship between the matrix suction and volumetric water content of geotextiles. It is an important parameter for measuring and designing the capillary blocking effect. Therefore, it is very important to use geotextiles of different specifications according to different engineering needs to achieve scientific design of actual projects and accurately obtain the moisture characteristic curve of geotextiles.

[0003] At present, the methods for measuring the moisture characteristic curve of geotextiles mainly include the capillary rise method and the pressure chamber method. Among them, the capillary rise method test process is relatively simple, but when the ambient temperature is high, the test results are easily affected by evaporation and have large errors; the pressure chamber method is more accurate in measuring the moisture characteristic curve of geotextiles, but the test system is complex, the number of equipment is large, the cost of setting up the test system is high, and only one sample can be tested at a time, and the test efficiency is low. Utility Model Content

[0004] The purpose of the utility model is to provide a test device for measuring the moisture characteristic curve of geotextile. The device has a simple composition and is easy to build. It can test multiple samples at the same time, effectively solving the problem of the influence of ambient temperature on the test results. It can test the moisture characteristic curve of geotextile under various working conditions at the same time, solving the problems of high equipment cost for measuring the moisture characteristic curve of geotextile, complex equipment composition, low test efficiency and high sensitivity of the test process to the environment.

[0005] The working principle of the utility model is as follows: the moisture characteristic curve of the geotextile is one of its unsaturated hydraulic characteristics, which describes the relationship between the volumetric water content and the matrix suction, and can be divided into: a wet curve and a dry curve. The wet curve is obtained by wetting the sample, and the matrix suction at the starting point is the largest. As the matrix suction gradually decreases, the sample water content gradually increases; the dry curve is opposite to the wet curve, and is obtained by draining the sample. The starting point is a saturated state, at which the matrix suction is close to zero, and the sample water content gradually decreases as the matrix suction increases.

[0006] In order to achieve the above purpose, this application adopts the following technical solutions:

[0007] The utility model provides a test device for measuring the moisture characteristic curve of geotextile, the test device comprises a supporting body, the supporting body is provided with a cylinder body and a separate cylinder body whose height can be freely adjusted;

[0008] The upper and lower parts of the cylinder are both provided with water outlet holes and connected with multiple water valves, and the upper part is also provided with a water filling hole;

[0009] The separate cylinder includes an upper cylinder and a lower cylinder connected by flanges, a clay plate is horizontally arranged in the lower cylinder, the air intake value of the clay plate is greater than the air intake value of the geotextile sample, the edge of the clay plate is sealed and connected to the side wall of the lower cylinder, and the upper and lower parts of the separate cylinder are both provided with water outlets and connected to a single-outlet water valve;

[0010] The single-outlet water valve located at the upper part of the separate cylinder is connected to one of the interfaces of the multi-outlet water valve located at the upper part of the cylinder through a water pipe, and the single-outlet water valve located at the lower part of the separate cylinder is connected to one of the interfaces of the multi-outlet water valve located at the lower part of the cylinder through a water pipe.

[0011] In the above technical solution, the lower cylinder is in the shape of a funnel.

[0012] In the above technical solution, there are one or more separate cylinders.

[0013] In the above technical solution, a plurality of transverse support rods are provided on the support body, a plurality of pulleys are provided on the transverse support rods, and the cylinder body and the separate cylinder body are both hoisted on the pulleys by steel wire ropes.

[0014] In the above technical solution, the clay plate is arranged at the flange position of the lower cylinder.

[0015] In the above technical solution, the clay plate is connected to the side wall of the lower cylinder by epoxy resin sealing.

[0016] The beneficial effects of the utility model are:

[0017] 1. The utility model greatly improves the working efficiency of measuring the moisture characteristic curve of geotextiles. The cylinder can be connected with multiple separate cylinders, and multiple geotextile samples can be tested at the same time, which greatly shortens the overall test time. If the number of test samples is small, the corresponding number of valves can be closed.

[0018] 2. According to the actual test needs, the moisture characteristic points of the samples under different matrix suction can be measured at the same time. That is, keep the height of the cylinder unchanged and adjust the height of the separate cylinder. Because each cylinder is equipped with a pulley, multiple cylinders can be at different heights, thereby realizing the measurement of multiple geotextile samples under multiple matrix suction values.

[0019] 3. The cylinder and the top of the separate cylinder are connected by water pipes, which minimizes the impact of the evaporation of water in the sample due to ambient temperature on the test results.

[0020] 4. The whole test process is easy to operate. The water level difference between the two cylinders (cylinder and separate cylinder) is used with the help of clay plates to apply different matrix suction values ​​to the geotextile samples. By weighing the weight of the geotextile samples at different matrix suction values, the corresponding sample moisture content can be obtained, thereby obtaining the moisture characteristic points of the geotextile samples, and then the geotextile moisture characteristic curve can be obtained.

[0021] 5. The application of matrix suction mainly depends on the water level difference and clay board. Clay board is an inorganic non-metallic sintered body with certain pores. It is resistant to high temperature, wear and tear, has high mechanical strength, and has a controllable pore structure. Clay boards with different pore sizes can be used according to different test samples, so that the test equipment can be used for the determination of moisture characteristic curves of geotextiles of various specifications.

[0022] 6. The utility model has a simple structure, low construction cost and low processing difficulty, which not only meets the equipment requirements but also effectively controls the equipment cost. The components used in the system are all common equipment or materials on the market, such as silicone water pipes, pulleys, acrylic cylinders, etc. The equipment purchase cost is low and easy to obtain.

[0023] 7. The separate cylinder is connected by flanges, and a sealing rubber ring is added between the flanges. It is firmly fixed by bolts to ensure the sealing of the cylinder and prevent the sample from being affected by the external environment. At the same time, it is convenient to take the sample and weigh it to obtain test data. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the test device of the utility model;

[0025] Figure 2 yes Figure 1 Schematic diagram of the center separation cylinder structure;

[0026] Figure 3 yes Figure 1 Schematic diagram of the middle cylinder structure;

[0027] Figure 4 yes Figure 1 Schematic diagram of the top structure of the middle cylinder;

[0028] Figure 5 It is the geotextile moisture characteristic data points and fitting curve (matrix suction-volume water content);

[0029] Among them, 1. cylinder; 2. separate cylinder; 2a. upper cylinder; 2b. lower cylinder; 3. water outlet; 4. sealing rubber ring; 5. single-outlet water valve; 6. multi-outlet water valve; 7. water pipe; 8. clay plate; 9. epoxy resin; 10. supporting body; 11. water filling hole; 12. horizontal support rod; 13. pulley. DETAILED DESCRIPTION

[0030] In order to better illustrate the purpose, technical solutions and advantages of the utility model, the utility model will be further described below in conjunction with specific embodiments. The utility model can be implemented in many different forms and should not be understood as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the disclosure will be thorough and complete, and the concept of the utility model will be fully conveyed to those skilled in the art, and the utility model will only be limited by the claims.

[0031] As one embodiment, the utility model provides a test device for measuring the moisture characteristic curve of geotextile, such as Figure 1 As shown, it includes a supporting body 10, on which are three transverse supporting rods 12, each of which is provided with a certain number of pulleys 13, and wing-shaped handles are provided on both sides of the cylinder 1 and the separate cylinder 2, and the wire rope passes through the wing-shaped handles and is hoisted on the pulley 13, and the height of the cylinder 1 and the separate cylinder 2 can be freely adjusted.

[0032] The number of cylinders 1 on the entire test device is 1, and the number of separate cylinders 2 is 3. Of course, other numbers of separate cylinders 2 can also be set, and they only need to be connected according to the connection method of the utility model. The cylinder 1 and the separate cylinder 2 can be made of acrylic material, glass material, or other materials.

[0033] like Figure 3-4 As shown, the upper and lower parts of the cylinder 1 are provided with water outlets 3 and connected to a multi-port water valve 6. The number of water valves provided on the multi-port water valve 6 is set according to needs, such as Figure 3 5 are provided. Simultaneously, the upper part of the cylinder 1 is also provided with a water adding hole 11 for supplementing the test water.

[0034] like Figure 2 As shown, the upper and lower parts of the separate cylinder 2 are provided with water outlets 3 and connected to a single-outlet water valve 5. The separate cylinder 2 includes an upper cylinder 2a and a lower cylinder 2b connected by flanges, and the sealing is ensured by the bolt structure of the flange and the rubber sealing ring 4. The rubber sealing ring 4 is arranged between the upper and lower flanges, and the upper and lower flanges are tightened and pressed by the bolt structure to achieve sealing, thereby avoiding interference of the external environment on the measurement system. The detachable bolt structure ensures that the flange can be opened at any time to take out samples for weighing and recording data.

[0035] The side wall of the lower cylinder 2b is horizontally provided with a clay plate 8, which is a high air intake value clay plate, and its air intake value is greater than the air intake value of the geotextile sample. The clay plate is an inorganic non-metallic sintered body with certain pores. It is resistant to high temperature, wear and tear, has high mechanical strength, and has a controllable pore structure. Clay plates with different pore sizes can be used according to different test samples, so that the test equipment can be used for the determination of moisture characteristic curves of geotextiles of various specifications.

[0036] The edge of the clay plate 8 is sealed and connected with the side wall of the lower cylinder 2b. The clay plate 8 is arranged at the flange position of the lower cylinder 2b. The clay plate 8 is sealed and connected with the side wall of the lower cylinder 2b by epoxy resin 9, so as to achieve the effect of fixing and sealing.

[0037] The lower cylinder 2b is in the shape of a funnel. There are two main reasons for adopting this structure: ① This structure can more accurately control the matrix suction value applied to the geotextile through the water level difference between the cylinder 1 and the separated cylinder 2. ② The funnel structure can support the clay board 8 and then achieve a complete sealing effect through the epoxy resin 9.

[0038] The single-outlet water valve 5 located at the upper part of the separate cylinder 2 is connected to one of the interfaces of the multi-outlet water valve 6 located at the upper part of the cylinder 1 through the water pipe 7, and the single-outlet water valve 5 located at the lower part of the separate cylinder 2 is connected to one of the interfaces of the multi-outlet water valve 6 located at the lower part of the cylinder 1 through the water pipe 7.

[0039] The upper water valve is connected through a water pipe 7 to ensure the consistency of the internal environment of the two cylinders and reduce the test result error caused by evaporation. The lower water valve is connected through a water pipe 7, that is, different matrix suction values ​​are applied to the sample through the water level difference in the two cylinders.

[0040] The utility model mainly uses the porous material, namely the clay plate 8, and the water level difference between the two cylinders to achieve the application of different matrix suctions. The clay plate 8 is a porous medium material, and the size of the pore size can be controlled manually; the geotextile is placed on the clay plate 8, and a certain load is added above the geotextile to achieve good contact between it and the clay plate 8. Through the height difference between the water level at the bottom of the clay plate 8 and the connected water level, different matrix suctions are applied to the geotextile sample. The calculation of the matrix suction size is shown in Formula 1.

[0041]

[0042] Where: is the matrix suction (Pa); ρ is the density of water (kg / m 3 ), g is the acceleration due to gravity (N / kg), and h is the water level difference between the water level in the cylinder 1 and the water level in the separate cylinder 2 (m).

[0043] When the geotextile reaches equilibrium, weigh it and calculate the volumetric moisture content to draw the geotextile moisture characteristic curve (matrix suction-volume moisture content), such as Figure 5 The calculation of volumetric water content is shown in formula 4.

[0044] θ=S*n (4)

[0045] Where: θ is the volumetric water content (%); S is the saturation (%); n is the porosity (%).

[0046] Wherein, n and S are calculated as shown in Equations 5 and 6.

[0047]

[0048]

[0049] Where: M A is the mass per unit area (g / m 2 );ρ f is the fiber density (g / cm 3 ); t is the sample thickness (cm); w is the water content (g); ρ w is the density of water (g / cm 3 ). Among them, w can be obtained by subtracting the weight of the geotextile in a dry state from the weight when it reaches equilibrium.

[0050] After obtaining data points through experiments, the geotextile moisture characteristic curve fitting parameters α, n, and m are obtained using the data point fitting formula 2:

[0051]

[0052] Where: θ is the volumetric water content; θ r is the residual volume water content; θ s is the saturated volume water content; is the matrix suction (Pa); α, n, and m are fitting parameters.

[0053] Test process

[0054] The operation process of the drying path curve test is as follows:

[0055] 1. Cut several pieces of geotextile samples with a diameter of 6mm, and use an electronic scale with an accuracy of 0.01g to weigh the weight of the completely dry geotextile. After weighing, place the sample on top of the clay board and place a 225g load to ensure good contact between the geotextile and the clay board.

[0056] 2. Inject a certain amount of water into cylinder 1, keep cylinder 1 higher than separate cylinder 2, and keep this state for at least 24 hours to make the geotextile saturated. At this time, take out the geotextile and weigh its mass in the saturated state to calculate the saturated volume water content θ s After weighing, put the geotextile back and place the load. Adjust the height of the separated cylinder 2 so that the clay plate 8 is level with the water level in the cylinder 1, that is, the zero suction level, to remove excess water from the geotextile.

[0057] 3. After the above steps are completed, the geotextile sample is gradually dried by adjusting the height of the separate cylinder 2 and gradually increasing the suction by 0.05-0.2 kPa. After each adjustment of the suction value, the sample is taken out of the cylinder and weighed after at least 24-48 hours of balancing. After the matrix suction is changed and stabilized, there is no obvious change in the sample weight. The moisture content of the sample in this state can be considered as the residual volume moisture content θ r The volumetric moisture content of the geotextile under different matrix suction conditions was calculated by weighing data and known quantities, and then the moisture characteristic curve of the drying path was drawn.

[0058] The measurement of the wet path curve is the opposite process. The dry path sample state is used as the starting state. By adjusting the height of the separate cylinder 2, the matrix suction is gradually reduced by 0.05-0.2kPa. After each adjustment of the suction value, the sample is taken out of the cylinder and weighed after at least 24-48 hours of balancing until the matrix suction is changed and stabilized, and the sample weight does not change significantly. The volume water content of the geotextile under different matrix suction conditions is calculated by weighing data and known quantities, and then the moisture characteristic curve of the wet path is drawn.

[0059] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention of the utility model.

Claims

1. A test device for measuring the moisture characteristic curve of geotextile, characterized by: The test device comprises a supporting body (10), on which a cylinder (1) whose height can be freely adjusted and a separate cylinder (2) are provided; The upper and lower parts of the cylinder (1) are both provided with water outlet holes (3) and connected to a multi-port water valve (6), and the upper part is also provided with a water supply hole (11); The separate cylinder (2) comprises an upper cylinder (2a) and a lower cylinder (2b) connected by flanges, a clay plate (8) is horizontally arranged in the lower cylinder (2b), the air intake value of the clay plate (8) is greater than the air intake value of the geotextile sample, the edge of the clay plate (8) is sealedly connected to the side wall of the lower cylinder (2b), and the upper and lower parts of the separate cylinder (2) are both provided with water outlet holes (3) and connected to a single-outlet water valve (5); The single-outlet water valve (5) located at the upper part of the detachable cylinder (2) is connected to one of the interfaces of the multi-outlet water valve (6) located at the upper part of the cylinder (1) through a water pipe (7), and the single-outlet water valve (5) located at the lower part of the detachable cylinder (2) is connected to one of the interfaces of the multi-outlet water valve (6) located at the lower part of the cylinder (1) through a water pipe (7).

2. The test device according to claim 1, characterized in that: The lower cylinder (2b) is in the shape of a funnel.

3. The test device according to claim 1, characterized in that: The separate cylinder (2) is provided with one or more.

4. The test device according to claim 1, characterized in that: The supporting body (10) is provided with a plurality of transverse supporting rods (12), the transverse supporting rods (12) are provided with a plurality of pulleys (13), and the cylinder (1) and the separate cylinder (2) are both suspended on the pulleys (13) by means of steel wire ropes.

5. The test device according to claim 1, characterized in that: The clay plate (8) is arranged at the flange position of the lower cylinder (2b).

6. The test device according to claim 1, characterized in that: The clay plate (8) is sealed and connected to the side wall of the lower cylinder (2b) via epoxy resin (9).

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