CN116840125B - Device and method for testing water permeability anisotropy of road base granule - Google Patents

Abstract

The present invention belongs to the technical field of granular material penetration testing equipment, and relates to a kind of granular material permeability anisotropy testing equipment for road base, including: a test box, a water storage tank, a water head height control part, composed of a first vertical pipe, a second vertical pipe, a plurality of horizontal pipes and a regulating valve, the first vertical pipe and the second vertical pipe are relatively vertically arranged and the upper ends are both closed structures, the water head height control part is used to adjust the water head height sent into the test box; a sand settling tank is connected to the other side of the test box; a conveying assembly is respectively connected to the water storage tank and the water head height control part, and is used to convey the water inside the water storage tank to the test box through the water head height control part. The present invention can adjust the water head height sent into the test box through the setting of the water head height control part, so that the test box can perform a lateral seepage test, thereby being able to evaluate the difference between the lateral and vertical permeability coefficients, and improving the accuracy of the granular material penetration test.

Description

A kind of testing device and method for water permeability anisotropy of road base aggregate

Technical Field

The invention belongs to the technical field of granular material penetration testing equipment, and relates to an anisotropic water permeability testing equipment and method for road base granular materials.

Background technique

The main function of the drainage base is to remove the water that seeps from the road surface. The permeability coefficient is an indicator used to characterize the permeability. The correct determination of the permeability coefficient value is of great significance to the permeability calculation and the design of the drainage layer. Therefore, it is necessary to conduct a more in-depth study on the permeability coefficient. According to the different principles of permeability test, the methods for determining the permeability coefficient of large-void asphalt mixture in my country are mainly divided into two categories. One is the variable head permeability test represented by T0730 in the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering" (JTGE20-2011), which uses a variable head permeability meter for testing; the other is the constant head permeability coefficient test method represented by the "Technical Specification for Design and Construction of Drained Asphalt Pavement" (JTG T3350-03-2020). In recent years, relevant scholars at home and abroad have analyzed and compared the two methods and believe that the variable head permeability test is suitable for measuring materials with a smaller permeability coefficient, and the constant head permeability meter is suitable for measuring materials with a larger permeability coefficient.

Currently, most granular material permeability tests use vertical seepage equipment, which cannot evaluate the anisotropy of granular material permeability coefficient, that is, the difference between the lateral and vertical permeability coefficients, reducing the accuracy of granular material permeability tests.

Summary of the invention

The present invention aims to provide a device and method for testing the anisotropy of water permeability of road base aggregates. The water head height sent into the test box is adjusted by a water head height control component, so that the test box can perform a lateral seepage test, thereby evaluating the difference between the lateral and vertical permeability coefficients and improving the accuracy of the aggregate permeability test.

To achieve the above-mentioned purpose, the specific technical scheme of the present invention is a device and method for testing the water permeability anisotropy of road base aggregate as follows:

A device for testing the water permeability anisotropy of road base aggregate, comprising:

Test chamber;

A water storage tank is arranged at the lower part of the test chamber;

The water head height control component is connected to one side of the test box, and is composed of a first vertical pipe, a second vertical pipe, a plurality of horizontal pipes and a regulating valve. The first vertical pipe and the second vertical pipe are relatively vertically arranged and the upper ends are both closed structures. The plurality of horizontal pipes are evenly arranged horizontally from top to bottom between the first vertical pipe and the second vertical pipe. The two ends of each horizontal pipe are respectively connected to the first vertical pipe and the second vertical pipe. The plurality of regulating valves correspond to the plurality of horizontal pipes one by one, and each regulating valve is arranged on the corresponding horizontal pipe. The water head height control component is used to adjust the water head height sent into the test box.

A grit chamber connected to the other side of the test chamber;

The conveying assembly is connected to the water storage tank and the water head height control component respectively, and is used to convey the water in the water storage tank to the test box through the water head height control component.

The present invention is also characterized in that:

The conveying component includes a water pump, the input end of the water pump is connected to the side of the water tank near the lower part through a first connecting pipe, the output end of the water pump is connected to the lower end of the first vertical pipe through a second connecting pipe, a third connecting pipe is provided at the lower end of the second vertical pipe, the tube body of the third connecting pipe is connected to the lower end of the second vertical pipe, the two ends of the third connecting pipe are respectively connected to the side of the water tank near the upper part and the first vertical pipe near the lower end, a fourth connecting pipe is provided at the upper part of the third connecting pipe, the two ends of the fourth connecting pipe are respectively connected to the first vertical pipe located at the upper part of the third connecting pipe and the test box, the third connecting pipe is provided with a first valve, and a second valve is provided on the first vertical pipe at a position between the third connecting pipe and the fourth connecting pipe.

The grit chamber and the test box are connected via a fifth connecting pipe, one end of the fifth connecting pipe is connected to the lower part of the test box near the other side, the other end of the fifth connecting pipe is connected to the upper part of the grit chamber, the end of the fourth connecting pipe is connected to the lower part of the test box near one side, and the third valve is respectively provided on the fourth connecting pipe and the fifth connecting pipe.

An observation window is arranged on the front of the test box, and a plurality of observation tubes are vertically arranged on the back of the test box. The plurality of observation tubes are evenly arranged along the length direction of the test box, and the lower end of each observation tube is connected to the inside of the test box.

The lower part of the grit chamber is connected to the water tank through a sixth connecting pipe, the two ends of the sixth connecting pipe are respectively connected to the lower part of the grit chamber and the side of the water tank near the lower part, the upper part of the grit chamber is connected to the sixth connecting pipe through a seventh connecting pipe, and a flow meter is provided on the seventh connecting pipe.

Screens are vertically arranged near both sides of the test box, the fourth connecting pipe is located between the corresponding screen and one inner wall of the test box, and the fifth connecting pipe is located between the corresponding screen and the other inner wall of the test box.

It also includes a sleeve, which is vertically arranged on the upper part of the test box. A mounting hole is arranged on the upper part of the test box near the lower end of the sleeve. A cover is arranged in the mounting hole. The lower end of the sleeve is detachably connected to the inner wall of the mounting hole. The inside of the sleeve is used to place a seepage meter, and the seepage meter is used to cooperate with the test box to carry out vertical seepage test.

A method for using a road base material water permeability anisotropy testing device, the specific steps are:

Step S1, batching the base granules according to the target moisture content, compacting the base granules, measuring the unit dry weight of the base granules and recording the moisture content and total mass of the base granules, and then filling the base granules into a test box;

Step S2, filling the water tank with water. After the water filling is completed, the water tank is evacuated by a vacuum pump to remove the air inside the water tank so that the water is basically saturated;

Step S3, start the water pump to allow the water flow to penetrate and soak the base granular materials in the test box, and turn off the water pump after the water flows into the grit chamber;

Step S4, conduct a lateral seepage test, open the two third valves on the fourth connecting pipe and the fifth connecting pipe, start the water pump, and then repeatedly open and close the regulating valves on multiple horizontal pipes from bottom to top until the appropriate regulating valve is opened to control the water head height to reach the target value, and observe whether the water level heights in the two observation tubes on the test box respectively close to the fourth connecting pipe and the fifth connecting pipe are equal. If the water head heights in the two observation tubes are equal, the water flow saturation is estimated; after the water head is stable, the water head height data in the process of water flow passing through the base material is recorded through the multiple observation tubes connected to the test box, the water flow rate is measured by a flow meter, and the water temperature is measured to calculate the lateral permeability coefficient;

Step S5, conduct a vertical seepage test, close the two third valves on the fourth connecting pipe and the fifth connecting pipe, open the cover on the mounting hole, install the lower end of the sleeve in the mounting hole, and then place the seepage meter in the sleeve, set the liquid level using a hydraulic gauge, and conduct a permeability test on the base granular material through the top cover of the test box. For base granular materials with a slower permeability rate, read the thin tube scale on the top of the seepage meter, and for base granular materials with a faster permeability rate, read the thick tube scale on the bottom of the seepage meter, and then calculate to obtain the vertical permeability coefficient.

The calculation process of the lateral permeability coefficient in step 4 is as follows:

Wherein, _kT is the permeability coefficient of the material at temperature T, _k20℃ is the permeability coefficient of the material at 20℃, _ηT is the viscosity of water at temperature T, _η20℃ is the viscosity of water at 20℃, _γw (T) is the unit weight of water at temperature T, and the unit of T is ℃.

The calculation process of the vertical permeability coefficient in step 5 is as follows:

R _t = 2.2902(0.9842 ^T )/T ^0.1702 (3)

Among them, _Rt is the ratio of the kinematic viscosity of the permeate at the test temperature during the time from _t1 to _t2 to the kinematic viscosity of water at 20℃, d is the diameter of the top capillary tube, _D1 is the diameter of the bottom thick tube, a is the coefficient, for impermeable base layer a＝+1, the measured material has infinite depth, that is, a＝0 when it is more than 20 times _D1 , for permeable base layer a＝-1, _b1 is the thickness of the base layer granular material, _H1 is the effective water head height at _t1 , that is, the top capillary scale or the bottom thick tube scale at _t1 , _H2 is the effective water head height at _t2 , that is, the top capillary scale or the bottom thick tube scale at _t2 , _G1 is the seepage meter coefficient, and K is the vertical permeability coefficient.

The device and method for testing water permeability anisotropy of road base aggregate of the present invention have the following advantages:

First, by setting the water head height control part, the water head height sent into the test box can be adjusted, so that the test box can carry out a lateral seepage test, thereby being able to evaluate the difference between the lateral and vertical permeability coefficients and improve the accuracy of the granular material permeability test.

Secondly, by coordinating the conveying components with the water head height control components, the test box and the water storage tank, not only can the lateral seepage test be carried out, but the test box and the water storage tank can also be drained, and the application range is wide.

Third, by coordinating the sixth connecting pipe with the grit chamber and the water storage tank, the water in the grit chamber can flow back into the water storage tank, thereby realizing the recycling of water in the entire device and saving water.

Fourth, through the coordinated setting of the seepage meter and the test box, not only the horizontal seepage test can be carried out, but also the vertical seepage test can be carried out, which is convenient for quickly evaluating the difference between the horizontal and vertical permeability coefficients. At the same time, many tests have shown that the seepage test carried out by this device has a high repeatability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the overall structure of the present invention;

FIG2 is a schematic diagram of the structure of the water head height control member in the present invention;

FIG3 is a schematic diagram of the structure of the test box in the present invention;

FIG4 is a schematic diagram of the structure of the screen in the present invention;

FIG. 5 shows the lateral permeability coefficients of base layer granular materials with different granularity in the present invention.

Reference numerals:

1. Test chamber; 2. Water storage tank; 3. Grit chamber; 4. Flow meter; 5. Observation tube; 6. Screen; 7. Observation window; 8. Water head height control element; 81. First vertical pipe; 82. Horizontal pipe; 83. Regulating valve; 84. Second vertical pipe; 9. Sleeve; 10. Water pump; 14. First connecting pipe; 16. Second connecting pipe; 17. Third connecting pipe; 18. Fourth connecting pipe; 19. Fifth connecting pipe; 20. Sixth connecting pipe; 21. Seventh connecting pipe.

Detailed ways

In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a device and method for testing the anisotropy of water permeability of road base aggregates of the present invention in conjunction with the accompanying drawings.

As shown in FIGS. 1 and 2 , a device for testing the water permeability anisotropy of road base granular materials of the present invention comprises a test box 1 having a size of 1 m×0.5 m×0.4 m, which is large enough to perform a combined test on multi-layer roadbed materials. A water storage tank 2 is disposed at the lower portion of the test box 1, and the water storage tank 2 is used to supply water to the inside of the test box 1. A water head height control member 8 is connected to one side of the test box 1, and the water head height control member 8 is composed of a first vertical pipe 81, a second vertical pipe 84, a plurality of transverse pipes 82 and a regulating valve 83. The first vertical pipe 81 and the second vertical pipe 84 are relatively vertically arranged and the upper ends are both closed structures. The plurality of transverse pipes 82 are evenly and horizontally arranged between the first vertical pipe 81 and the second vertical pipe 84 from top to bottom, and the two ends of each transverse pipe 82 are respectively connected to the first vertical pipe 81 and the second vertical pipe 84. Two vertical pipes 84 are connected, and multiple regulating valves 83 correspond to multiple horizontal pipes 82 one by one. Each regulating valve 83 is set on the corresponding horizontal pipe 82. The head height control part 8 is used to adjust the head height of the water sent into the test box 1. The other side of the test box 1 is connected to the sand settling tank 3. A conveying component is arranged between the water storage tank 2 and the head height control part 8. The conveying component is connected to the water storage tank 2 and the head height control part 8 respectively. The conveying component is used to convey the water inside the water storage tank 2 to the test box 1 through the head height control part 8. Through the setting of the head height control part 8, the head height of the water sent into the test box 1 can be adjusted, so that the test box can carry out a lateral seepage test, thereby being able to evaluate the difference between the lateral and vertical permeability coefficients and improve the accuracy of the granular material penetration test.

As shown in FIG1 , the conveying assembly includes a water pump 10. The input end of the water pump 10 is connected to the side of the water storage tank 2 near the lower part through a first connecting pipe 14. The output end of the water pump 10 is connected to the lower end of the first vertical pipe 81 through a second connecting pipe 16. A tee is provided between the output end of the water pump 10 and the second connecting pipe 16. Both ends of the tee are connected to the output end of the water pump 10 and the second connecting pipe 16. The other end of the tee is connected to a drain pipe. A drain valve is provided on the drain pipe. A third connecting pipe 17 is provided at the lower end of the second vertical pipe 84. The pipe body of the third connecting pipe 17 is connected to the lower end of the second vertical pipe 84. Both ends of the third connecting pipe 17 are respectively connected to the water storage tank 2. The side of the box 2 is connected to the position near the upper part and the position near the lower end of the first vertical pipe 81. The upper part of the third connecting pipe 17 is provided with a fourth connecting pipe 18. The two ends of the fourth connecting pipe 18 are respectively connected to the position of the first vertical pipe 81 located at the upper part of the third connecting pipe 17 and the test box 1. The third connecting pipe 17 is provided with a first valve. The first vertical pipe 81 is provided with a second valve at a position between the third connecting pipe 17 and the fourth connecting pipe 18. When it is necessary to penetrate and soak the base granular material in the test box 1, the first valve is closed, the second valve on the first vertical pipe 81 is opened, and the multiple regulating valves 83 are all in a closed state. The water pump 10 is started, and the water pump 10 is The water in the water storage tank 2 is transported to the second connecting pipe 16 through the first connecting pipe 14, then enters the fourth connecting pipe 18 through the first vertical pipe 81, and finally enters the interior of the test box 1. When a horizontal penetration test is required, the first valve is closed, the second valve on the first vertical pipe 81 is closed, the water pump 10 is started, and then the plurality of regulating valves 83 are repeatedly opened and closed from top to bottom until the appropriate regulating valve 83 is opened to control the water head height to reach the target value. The water pump 10 transports the water in the water storage tank 2 through the first connecting pipe 14 to the second connecting pipe 16, then enters the third connecting pipe 17 through the first vertical pipe 81, and enters the second vertical pipe 84 from the third connecting pipe 17, and then enters the test box 1. The water enters the first vertical pipe 81 through the horizontal pipe 82 corresponding to the opened regulating valve 83, and then enters the inside of the test box 1 from the fourth connecting pipe 18. When it is necessary to drain the inside of the test box 1 and the water storage tank 2, open the first valve, the second valve and the drain valve (the drain valve is only opened when draining), and the multiple regulating valves 83 are all in the closed state. Start the water pump 10, and the water in the test box 1 enters the first vertical pipe 81 through the fourth connecting pipe 18, and then enters the third connecting pipe 17 from the first vertical pipe 81, and enters the water storage tank 2 from the third connecting pipe 17. The water in the water storage tank 2 enters the water pump 10 through the first connecting pipe 14, and is discharged from the water outlet provided on the water pump 10.

The grit chamber 3 is connected to the test box 1 through the fifth connecting pipe 19, one end of the fifth connecting pipe 19 is connected to the lower part of the test box 1 near the other side, and the other end of the fifth connecting pipe 19 is connected to the upper part of the grit chamber 3. The end of the fourth connecting pipe 18 is connected to the lower part of the test box 1 near one side. The fourth connecting pipe 18 and the fifth connecting pipe 19 are respectively connected to the two sides of the lower part of the test box 1, so that the lateral seepage test can be carried out and drainage is convenient. The fourth connecting pipe 18 and the fifth connecting pipe 19 are respectively provided with a third valve.

As shown in FIG3 , an observation window 7 is provided on the front of the test box 1, and the observation window 7 is used to observe the test phenomena during the process of water flowing through the base granular material inside the test box. A plurality of observation tubes 5 are vertically provided on the back of the test box 1, and the plurality of observation tubes 5 are evenly arranged along the length direction of the test box 1. The lower end of each observation tube 5 is connected to the inside of the test box 1, and the observation tubes 5 are used to observe the water head height at the corresponding position of the test box 1.

The lower part of the grit chamber 3 is connected to the water storage tank 2 via the sixth connecting pipe 20, and the two ends of the sixth connecting pipe 20 are respectively connected to the lower part of the grit chamber 3 and the side of the water storage tank 2 near the lower part. The sixth connecting pipe 20 facilitates the water in the grit chamber 3 to flow back into the water storage tank 2, thereby realizing the recycling of water in the entire device and saving water. The upper part of the grit chamber 3 is connected to the sixth connecting pipe 20 via the seventh connecting pipe 21, and the seventh connecting pipe 21 is provided with a flow meter 4, and the flow rate of the water flow is detected by the flow meter 4.

As shown in FIG4 , screens 6 are vertically arranged near both sides of the inside of the test box 1, the fourth connecting pipe 18 is located between the corresponding screen 6 and the inner wall of one side of the test box 1, and the fifth connecting pipe 19 is located between the corresponding screen 6 and the inner wall of the other side of the test box 1. The screen 6 has three layers, and the mesh size decreases from the inner wall of the test box 1 toward the inside to prevent the loss of granular materials of the main particle size. At the same time, a barrier strip 22 is arranged on the inner wall of the test box 1 to prevent the wall effect of water flow.

The present invention provides an anisotropic water permeability testing device for road base granular materials, which also includes a sleeve 9, which is vertically arranged on the upper part of a test box 1. A mounting hole is arranged at a position near the lower end of the sleeve 9 on the upper part of the test box 1, and a cover is arranged in the mounting hole. The lower end of the sleeve 9 is detachably connected to the inner wall of the mounting hole. The inside of the sleeve 9 is used to place a seepage meter, and the seepage meter is used to cooperate with the test box 1 to perform a vertical seepage test.

A method for using a road base material water permeability anisotropy testing device, the specific steps are:

Step S1, batching the base granules according to the target moisture content, compacting the base granules, measuring the unit dry weight of the base granules and recording the moisture content and total mass of the base granules, and then filling the base granules into the test box 1;

Step S2, filling the water storage tank 2 with water. After the filling is completed, the water storage tank 2 is evacuated by a vacuum pump to remove the air inside the water storage tank 2 so that the water is in a basically saturated state;

Step S3, start the water pump 10 to allow the water flow to penetrate and soak the base granular materials in the test box 1, and turn off the water pump 10 after the water flows into the grit chamber 3;

Step S4, conduct a lateral seepage test, open the two third valves on the fourth connecting pipe 18 and the fifth connecting pipe 19, start the water pump 10, and then repeatedly open and close the regulating valves 83 on the multiple horizontal pipes 82 from bottom to top until the appropriate regulating valve 83 is opened to control the water head height to reach the target value, and observe whether the water level heights in the two observation tubes 5 on the test box 1, which are respectively close to the fourth connecting pipe 18 and the fifth connecting pipe 19, are equal. If the water head heights in the two observation tubes 5 are equal, the water flow saturation is estimated; after the water head is stable, the water head height data in the process of water flow passing through the base material is recorded through the multiple observation tubes 5 connected to the test box, the water flow rate is measured by the flowmeter 4, and the water temperature is measured to calculate the lateral permeability coefficient;

Step S5, conduct a vertical seepage test, close the two third valves on the fourth connecting pipe 18 and the fifth connecting pipe 19, open the cover on the mounting hole, install the lower end of the sleeve 9 in the mounting hole, and then place the seepage meter in the sleeve 9, set the liquid level using a hydraulic gauge, and conduct a permeability test on the base granular material through the top cover of the test box. For base granular materials with a slower permeability rate, read the thin tube scale on the top of the seepage meter, and for base granular materials with a faster permeability rate, read the thick tube scale on the bottom of the seepage meter, and then calculate to obtain the vertical permeability coefficient.

The calculation process of the lateral permeability coefficient in step 4 is as follows:

Wherein, _kT is the permeability coefficient of the material at temperature T, _k20℃ is the permeability coefficient of the material at 20℃, _ηT is the viscosity of water at temperature T, _η20℃ is the viscosity of water at 20℃, _γw (T) is the unit weight of water at temperature T, and the unit of T is ℃.

The calculation process of the vertical permeability coefficient in step 5 is as follows:

R _t = 2.2902(0.9842 ^T )/T ^0.1702 (3)

Among them, _Rt is the ratio of the kinematic viscosity of the permeate at the test temperature during the time from _t1 to _t2 to the kinematic viscosity of water at 20℃, d is the diameter of the top capillary tube, _D1 is the diameter of the bottom thick tube, a is the coefficient, for impermeable base layer a＝+1, the tested material has infinite depth, that is, a＝0 when it is more than 20 times _D1 , for permeable base layer a＝-1, _b1 is the thickness of the base layer granular material, _H1 is the effective water head height at _t1 , that is, the top capillary scale or the bottom thick tube scale at _t1 , _H2 is the effective water head height at _t2 , that is, the top capillary scale or the bottom thick tube scale at _t2 , K is the vertical permeability coefficient, _G1 is the seepage meter coefficient, and its calculation formula is obtained according to the specification ASTMD6391-06.

As shown in Figure 5, a lateral seepage test was conducted, using gravel as the base aggregate, and six groups of repeated permeability tests were performed with different head heights (50mm-300mm). The particle sizes of the base aggregates in the six groups of permeability tests were 50mm, 100mm, 150mm, 200mm, 250mm, and 300mm, respectively. The standard deviations of the test material samples of K (permeability coefficient) were calculated to be 2.96%, 1.01%, 1.30%, 2.03%, 1.00%, and 1.58%, respectively, which had good repeatability. Further, from image observation, it can be seen that the variation range of the permeability coefficient K of different base aggregates at different target head heights is basically the same, and the test results have high repeatability.

Working principle: When in use, firstly, the base granules are batched according to the target moisture content, then the base granules are compacted, the unit dry weight of the base granules is measured and the moisture content and total mass of the base granules are recorded, then the base granules are filled into the test box 1, and then the water storage tank 2 is filled with water. After the filling is completed, the water storage tank 2 is evacuated by a vacuum pump to remove the air inside the water storage tank 2, so that the water is basically saturated, and then the first valve is closed, and the second valve on the first vertical pipe 81 is opened, and the multiple regulating valves 83 are all in the closed state, and the water pump 10 is started, and the water pump 10 pumps the water in the water storage tank 2 through the first connecting pipe 14. The water is transported to the second connecting pipe 16, then enters the fourth connecting pipe 18 through the first vertical pipe 81, and finally enters the inside of the test box 1 to penetrate and soak the base granular material in the test box 1. After the water flows into the sand settling tank 3, the water pump 10 is turned off, and then a lateral seepage test is performed. The two third valves on the fourth connecting pipe 18 and the fifth connecting pipe 19 are opened, the first valve is closed, the second valve on the first vertical pipe 81 is closed, the water pump 10 is started, and then the plurality of regulating valves 83 are repeatedly opened and closed from top to bottom until the appropriate regulating valve 83 is opened to control the water head height to reach the target value. The water pump 10 transfers the water in the water storage tank 2 through the first connecting pipe 8 The water is transported to the second connecting pipe 16 through the first vertical pipe 81, then enters the third connecting pipe 17 through the first vertical pipe 81, enters the second vertical pipe 84 from the third connecting pipe 17, enters the first vertical pipe 81 through the horizontal pipe 82 corresponding to the opened regulating valve 83, and then enters the inside of the test box 1 from the fourth connecting pipe 18. By observing whether the water levels in the two observation pipes 5 on the test box 1 are equal, if the water levels in the two observation pipes 5 are equal, the water saturation is estimated; after the water head is stable, the water flow through the base material process is recorded through the multiple observation pipes 5 connected to the test box. Head height data, use flowmeter 4 to measure water flow, and measure water temperature, and calculate the lateral permeability coefficient; finally, conduct a vertical seepage test, close the two third valves on the fourth connecting pipe 18 and the fifth connecting pipe 19, open the cover on the mounting hole, install the lower end of the sleeve 9 in the mounting hole, and then place the seepage meter in the sleeve 9, use the hydraulic gauge to set the liquid level, and conduct a permeability test on the base granular material through the top cover of the test box. For base granular materials with a slower permeability rate, read the thin tube scale on the top of the seepage meter, and for base granular materials with a faster permeability rate, read the thick tube scale at the bottom of the seepage meter, and then calculate the vertical permeability coefficient.

The device and method for testing water permeability anisotropy of road base aggregate of the present invention have the following advantages:

First, by setting the water head height control part, the water head height sent into the test box can be adjusted, so that the test box can carry out a lateral seepage test, thereby being able to evaluate the difference between the lateral and vertical permeability coefficients and improve the accuracy of the granular material permeability test.

Secondly, by coordinating the conveying components with the water head height control components, the test box and the water storage tank, not only can the lateral seepage test be carried out, but the test box and the water storage tank can also be drained, and the application range is wide.

Third, by coordinating the sixth connecting pipe with the grit chamber and the water storage tank, the water in the grit chamber can flow back into the water storage tank, thereby realizing the recycling of water in the entire device and saving water.

Fourth, through the coordinated setting of the seepage meter and the test box, not only the horizontal seepage test can be carried out, but also the vertical seepage test can be carried out, which is convenient for quickly evaluating the difference between the horizontal and vertical permeability coefficients. At the same time, many tests have shown that the seepage test carried out by this device has a high repeatability.

It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims (3)

1. A water permeability anisotropy test apparatus for a road base granule, comprising:

A test chamber (1);

The water storage tank (2) is arranged at the lower part of the test box (1);

The water head height control part (8) is communicated with one side of the test box (1) and consists of a first vertical pipe (81), a second vertical pipe (84), a plurality of transverse pipes (82) and regulating valves (83), the first vertical pipe (81) and the second vertical pipe (84) are vertically arranged relatively, the upper ends of the first vertical pipe and the second vertical pipe are of a closed structure, the transverse pipes (82) are horizontally and uniformly arranged between the first vertical pipe (81) and the second vertical pipe (84) from top to bottom, the two ends of each transverse pipe (82) are respectively communicated with the first vertical pipe (81) and the second vertical pipe (84), the regulating valves (83) are in one-to-one correspondence with the transverse pipes (82), and each regulating valve (83) is arranged on the corresponding transverse pipe (82), and the water head height control part (8) is used for regulating the water head height fed into the test box (1);

The grit chamber (3) is communicated with the other side of the test box (1);

The conveying component is respectively connected with the water storage tank (2) and the water head height control piece (8) and is used for conveying water in the water storage tank (2) into the test box (1) through the water head height control piece (8);

The conveying assembly comprises a water pump (10), an input end of the water pump (10) is communicated with a position, close to the lower part, of the side surface of the water storage tank (2) through a first connecting pipe (14), an output end of the water pump (10) is connected with the lower end of a first vertical pipe (81) through a second connecting pipe (16), the lower end of a second vertical pipe (84) is provided with a third connecting pipe (17), a pipe body of the third connecting pipe (17) is communicated with the lower end of the second vertical pipe (84), two ends of the third connecting pipe (17) are respectively communicated with the position, close to the upper part, of the side surface of the water storage tank (2) and the position, close to the lower end, of the first vertical pipe (81), a fourth connecting pipe (18) is arranged on the upper part of the third connecting pipe (17), two ends of the fourth connecting pipe (18) are respectively connected with the position, close to the upper part of the third connecting pipe (17) and the test box (1), a first valve is arranged on the third connecting pipe (17), and the first valve (81) is arranged between the third connecting pipe (17) and the fourth connecting pipe (18);

The front of the test box (1) is provided with an observation window (7), the back of the test box (1) is vertically provided with a plurality of observation pipes (5), the observation pipes (5) are uniformly arranged along the length direction of the test box (1), and the lower end of each observation pipe (5) is communicated with the inside of the test box (1);

the sand setting tank (3) is communicated with the test box (1) through a fifth connecting pipe (19), one end of the fifth connecting pipe (19) is connected to the position, close to the other side, of the lower part of the test box (1), the other end of the fifth connecting pipe (19) is connected with the upper part of the sand setting tank (3), the end part of a fourth connecting pipe (18) is connected to the position, close to one side, of the lower part of the test box (1), and third valves are respectively arranged on the fourth connecting pipe (18) and the fifth connecting pipe (19);

The screen (6) is vertically arranged at positions, close to two sides, inside the test box (1), the end parts of the fourth connecting pipes (18) are positioned between the corresponding screen (6) and the inner wall of one side of the test box (1), and one ends of the fifth connecting pipes (19) are positioned between the corresponding screen (6) and the inner wall of the other side of the test box (1);

the screen (6) is provided with three layers, the mesh number of the three layers of screen (6) is sequentially reduced from the inner wall of the test box (1) to the inner direction, and the inner wall of the test box (1) is provided with a barrier strip (22);

still include sleeve (9), sleeve (9) vertical setting is in the upper portion of test box (1), the position that is close to sleeve (9) lower extreme on test box (1) upper portion is provided with the mounting hole, be provided with the lid in the mounting hole, the lower extreme and the mounting hole inner wall of sleeve (9) can be dismantled and be connected, the inside seepage flow appearance that is used for laying of sleeve (9), the seepage flow appearance is used for cooperating test box (1) to carry out vertical seepage flow test.

2. The water permeability anisotropy test equipment for the road base granules according to claim 1, wherein the lower part of the grit chamber (3) is communicated with the water storage tank (2) through a sixth connecting pipe (20), two ends of the sixth connecting pipe (20) are respectively connected to the lower part of the grit chamber (3) and the position, close to the lower part, of the side surface of the water storage tank (2), of the grit chamber (3), the upper part of the grit chamber (3) is communicated with the sixth connecting pipe (20) through a seventh connecting pipe (21), and a flowmeter (4) is arranged on the seventh connecting pipe (21).

3. The method for using the road base granule water permeability anisotropy test equipment according to claim 2, wherein the specific steps are as follows:

Step S1, proportioning base layer granules according to a target water content, compacting the base layer granules, measuring the unit dry weight of the base layer granules, recording the water content and the total mass of the base layer granules, and filling the base layer granules into a test box (1);

s2, filling water into the water storage tank (2), and vacuumizing the water storage tank (2) by using a vacuum pump after the water filling is finished to remove air in the water storage tank (2) so that the water is in a basic saturated state;

S3, starting a water pump (10), enabling water flow to permeate and soak base layer granules in the test box (1), and closing the water pump (10) after the water flows into the grit chamber (3);

s4, performing a transverse seepage test, opening two third valves on a fourth connecting pipe (18) and a fifth connecting pipe (19), starting a water pump (10), sequentially rotating regulating valves (83) on a plurality of transverse pipes (82) from bottom to top to control the water head height to reach a target value, and estimating the water flow saturation if the water head heights in the two observing pipes (5) which are respectively close to the fourth connecting pipe (18) and the fifth connecting pipe (19) on the test box (1) are equal; after the water head is stable, recording water head height data in the process that water flows pass through the base material through a plurality of observation pipes (5) connected with the test box, measuring the water flow by using a flowmeter (4), measuring the water temperature, and calculating to obtain a transverse permeability coefficient;

S5, performing vertical seepage test, namely closing two third valves on a fourth connecting pipe (18) and a fifth connecting pipe (19), opening a cover body on a mounting hole, mounting the lower end of a sleeve (9) in the mounting hole, placing a seepage meter in the sleeve (9), setting a liquid level by using a hydraulic meter, performing permeability test on base layer granules by using a top cover of a test box, reading the fine tube scale at the top of the seepage meter for base layer granules with slower permeability, reading the coarse tube scale at the bottom of the seepage meter for base layer granules with faster permeability, and calculating to obtain a vertical permeability coefficient;

The lateral permeability coefficient calculation process in the step S4 is as follows:

Wherein k _T is the permeability coefficient of the material at T temperature, k _20℃ is the permeability coefficient of the material at 20 ℃, eta _T is the viscosity of water at temperature T, eta _20℃ is the viscosity of water at 20 ℃, gamma _w(T) is the unit weight of water at T temperature, and T is the unit of temperature;

The vertical permeability coefficient calculation process in the step S5 is as follows:

R_t＝2.2902(0.9842^T)/T^0.1702 (3)

Wherein R _t is the ratio of the kinematic viscosity of the permeate to the kinematic viscosity of water at 20 ℃ at the test temperature in t ₁～t₂ time, D is the diameter of the top tubule, D ₁ is the diameter of the bottom tubule, a is a coefficient, for a watertight substrate a= +1, the infinite depth of the tested material is 20 times or more D ₁ a=0, for a watertight substrate a= -1, b ₁ is the thickness of the substrate granule, H ₁ is the effective head height at t ₁, i.e. the top tubule scale or the bottom tubule scale at t ₁, H ₂ is the effective head height at t ₂, i.e. the top tubule scale or the bottom tubule scale at t ₂, G ₁ is the coefficient of the seepage meter, and K is the vertical permeability coefficient.