Device for measuring saturated hydraulic conductivity of soil

Abstract

The utility model discloses a device for measuring the saturated hydraulic conductivity of soil. The device comprises a variable water measuring part, a constant water measuring part and a sealed cylinder with a through top, the interior of the sealing cylinder is sequentially divided into a placing area for placing a soil sample and a water outlet area from top to bottom through a permeable component, a water outlet pipe penetrating through the water outlet area is arranged on one side of the bottom of the sealing cylinder, a water outlet valve is arranged on the water outlet pipe, and the water outlet pipe is communicated with a graduated tube arranged in the vertical direction; the variable-water measuring part or the constant-water measuring part is detachably assembled at the top end of the graduated tube, and the arranged sealing cylinder and the graduated tube are matched with the variable-water measuring part and the constant-water measuring part, so that the saturated hydraulic conductivity of the soil can be measured by a variable-water-head method, and the saturated hydraulic conductivity of the soil can also be measured by a constant-water-head method; therefore, one tool has two purposes.

Description

Technical Field

[0001] The utility model relates to the technical field of soil physics, in particular to a device for measuring soil saturated hydraulic conductivity. Background Art

[0002] Soil saturated hydraulic conductivity is one of the main indicators of soil hydraulic conductivity, which is closely related to the migration capacity of soil nutrients, salts, pollutants, etc. At present, there are two methods for measuring soil saturated hydraulic conductivity: the fixed head method and the variable head method. The fixed head method is generally used for soils with high hydraulic conductivity (0-10 -5 cm s -1 ) soil samples, while the variable head method is mostly used for soil samples with lower hydraulic conductivity (10 -4 -10 -7 cm s -1 ) determination.

[0003] Since the hydraulic conductivity of soil in different depths and in different regions varies greatly, it is often difficult to meet actual needs using only one method, either constant water head or variable water head. Therefore, there is an urgent need for a device that can meet the needs of different soil samples at the same time, that is, a device that can use both constant water head and variable water head methods for measurement. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides a device for measuring soil saturated hydraulic conductivity, which can simultaneously measure soil saturated hydraulic conductivity by using constant water head method and variable water head method.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A device for measuring soil saturated hydraulic conductivity comprises a variable water measuring component, a fixed water measuring component and a sealing cylinder with a through top; the interior of the sealing cylinder is divided into a placement area and a water outlet area for placing soil samples from top to bottom in sequence by a water-permeable component; a water outlet pipe penetrating the water outlet area is arranged on one side of the bottom of the sealing cylinder; a water outlet valve is arranged on the water outlet pipe and the water outlet pipe is connected to a graduated tube arranged in a vertical direction; the variable water measuring component or the fixed water measuring component can be detachably assembled on the top of the graduated tube.

[0007] Specifically, the variable water measuring component includes a fine scale tube, the bottom of which is detachably connected to the scale tube via a transfer tube, and the fixed water measuring component includes a vent tube, which is detachably connected to the scale tube via a rubber stopper.

[0008] Preferably, the top port of the sealing cylinder is detachably connected to a ring knife for collecting soil samples through a connecting piece, and the ring knife and the placement area together form a filling portion for filling the soil sample.

[0009] Preferably, the connecting member comprises a connecting tube with two through ends, one end of the connecting tube is screwed onto the sealing tube, and the other end is screwed onto the ring cutter.

[0010] Preferably, a mounting sleeve which can move up and down is sleeved on the graduation tube, and a positioning rod is provided on one side of the mounting sleeve.

[0011] Compared with the prior art, the utility model has the following beneficial effects:

[0012] The utility model has a simple structure and is easy to use. The provided sealing cylinder and the graduated tube cooperate with the provided variable water head measuring component and the fixed water head measuring component to measure the saturated hydraulic conductivity of the soil by the variable water head method or the fixed water head method, thereby achieving dual purposes. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall cross-sectional structure after the water-variable measuring component is assembled on the graduated tube in the utility model;

[0014] Figure 2 It is a structural schematic diagram of the water change measuring component of the utility model;

[0015] Figure 3 It is a structural schematic diagram of the water determination component of the utility model.

[0016] Figure identification: 1. variable water measuring component, 11. fine scale tube, 12. adapter tube, 2. fixed water measuring component, 21. ventilation tube, 22. rubber stopper, 3. sealing cylinder, 31. placement area, 32. water outlet area, 33. water outlet pipe, 34. water outlet valve, 4. water permeable component, 5. scale tube, 6. connecting part, 7. ring knife, 8. assembly set, 9. positioning rod, A, reference surface. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments and drawings. The schematic implementation manner of the utility model and its description are only used to explain the utility model and are not intended to limit the utility model.

[0018] Example 1

[0019] like Figure 1-3A device for measuring soil saturated hydraulic conductivity shown in the figure comprises a variable water measuring component 1, a fixed water measuring component 2, and a sealing cylinder 3 with a through top. The interior of the sealing cylinder 3 is divided into a placement area 31 for placing soil samples and a water outlet area 32 from top to bottom by a water-permeable component 4. A water outlet pipe 33 penetrating the water outlet area 32 is provided on one side of the bottom of the sealing cylinder 3. A water outlet valve 34 is provided on the water outlet pipe 33, and the water outlet pipe 33 is connected to a calibrated tube 5 arranged in a vertical direction. When measuring the soil saturated hydraulic conductivity, the variable water measuring component 1 is assembled at the top of the top of the calibrated tube 5 to measure the soil saturated hydraulic conductivity by the variable water head method; the fixed water measuring component 2 is assembled at the top of the top of the calibrated tube 5 to measure the soil saturated hydraulic conductivity by the fixed water head method.

[0020] Specifically, Figure 2-3 As shown, the variable water measuring component 1 includes a fine scale tube 11, the bottom of which is detachably connected to the scale tube 5 via a transfer tube 12, and the fixed water measuring component 2 includes a vent tube 21, which is detachably connected to the scale tube 5 via a rubber stopper 22.

[0021] As a preferred embodiment of the above, the top port of the sealing cylinder 3 is detachably connected to the ring knife 7 for collecting soil samples through a connector 6. The ring knife 7 and the placement area 31 together form a filling portion for filling the soil sample. After the ring knife 7 collects the soil sample, the soil sample can be directly placed on the sealing cylinder for measuring the saturated hydraulic conductivity of the soil without removing it.

[0022] As a preferred embodiment of the above-mentioned embodiment, the connecting member 6 includes a connecting tube with two through ends, one end of the connecting tube is screwed onto the sealing tube 3, and the other end is screwed onto the ring knife 7. In some embodiments, the connecting member 6 can be a rubber sleeve. When the ring knife 7 is placed on the sealing tube 3, the rubber sleeve is simultaneously mounted on the ring knife 7 and the sealing tube 3, thereby realizing a sealed connection between the ring knife 7 and the sealing tube 3.

[0023] As a preferred solution of the above embodiment, a mounting sleeve 8 which can move up and down is sleeved on the graduated tube 5 , and a positioning rod 9 is provided on one side of the mounting sleeve 8 to facilitate reading of the scale on the graduated tube 5 .

[0024] In this embodiment, the basic theoretical basis for determining soil saturated hydraulic conductivity by the constant head and variable head methods is Darcy's law, that is, the water flux through the soil is proportional to the soil water potential gradient, and its expression is as follows:

[0025]

[0026] Where: Q is the water flow rate, K s is the saturated hydraulic conductivity, which is a parameter that has nothing to do with water flow conditions and is only related to soil characteristics; L is the soil length, A soilis the soil cross-sectional area; H is the water head height, and the negative sign indicates that the direction of water flow is opposite to the direction of hydraulic gradient.

[0027] In the process of determining soil saturated hydraulic conductivity by the constant water head method, the water head height of the upper layer of the soil sample is kept constant. The saturated hydraulic conductivity calculation formula can be derived using formula (1):

[0028]

[0029] Among them, K s is the saturated hydraulic conductivity, L is the height of the soil column, H 1 H is the height of the initial calibration tube water surface from the reference surface, 2 is the height of the water surface of the scale tube from the reference surface at the end time, t 1 is the start time, t 2 is the end time, H is the height of the bottom of the vent pipe from the reference surface, that is, the water head height.

[0030] During the measurement of the variable water head method, the amount of water added to the water inlet is constant. During the measurement, the pressure head applied to the upper end of the soil column is variable. Figure 3 As shown in the figure, the variable head method does not need to measure the water output, but only needs to measure a set of data on the change of water head over time. According to the law of conservation of mass, the water output flow calculated by Darcy's law should be equal to the change of water volume per unit time at the inlet end, that is, the soil saturated hydraulic conductivity is calculated using the following formula:

[0031]

[0032] Among them, K s is the saturated hydraulic conductivity of the soil, r is the radius of the fine-scale tube, R is the diameter of the soil sample, L is the height of the soil column, H 1 H is the height of the initial calibration tube water surface from the soil sample surface, 2 The height of the water surface in the scale pipe from the surface of the soil sample at the end time, t 1 is the start time, t 2 is the end time.

[0033] The steps for determining soil saturated hydraulic conductivity using the constant water head method are as follows:

[0034] 1. Take soil samples using the ring knife 7, and place the soil samples to be measured on the permeable stone to saturate them;

[0035] 2. According to Figure 1 Set up and assemble the variable water head method measuring device, and open the water outlet valve 34 so that the water level in the sealing cylinder 3 reaches the upper part of the water-permeable component 4, and then close the water outlet valve 34;

[0036] 3. Transfer the saturated soil sample in the ring cutter 7 to the placement area 31 of the sealing tube 3, and seal the ring cutter 7 and the sealing tube 3 through the connecting piece 6 to ensure that the connection between the ring cutter 7 and the sealing tube 3 is sealed and watertight;

[0037] 4. Open the water outlet valve 34, and start the test after the soil surface reaches stable water outlet;

[0038] 5. Close the water outlet valve 34 to ensure that there is enough water in the fine-scale tube 11 to satisfy one measurement experiment. Use a stopwatch to record the start time (t 1 ) and end time (t 2 ), and record the height of the water surface of the scale tube 5 from the reference surface A at the initial time (H 1 ) and the height of the water surface of the scale tube 5 from the reference surface A at the end (H 2 );

[0039] 6. Substitute the above data into Formula 3 to calculate the saturated hydraulic conductivity of the soil.

[0040] Determination of soil saturated hydraulic conductivity by variable water head method

[0041] 1. In Figure 1 On the basis of the water change determination component 1, remove it and replace it with Figure 3 The fixed water head measuring component shown realizes the transformation from a variable water head measuring device to a fixed water head;

[0042] 2. Take soil samples using the ring knife 7, and place the soil samples to be measured on the permeable stone to saturate them;

[0043] 3. Open the water outlet valve 34 so that the water level in the sealing tube 3 reaches the upper part of the water-permeable component 4, and then close the water outlet valve 34;

[0044] 4. Transfer the saturated soil sample in the ring cutter 7 to the placement area 31 of the sealing tube 3, and seal the ring cutter 7 and the sealing tube 3 through the connecting piece 6 to ensure that the connection between the ring cutter 7 and the sealing tube 3 is sealed and watertight;

[0045] 5. Open the water outlet valve 34, and start the test after the soil surface reaches stable water outlet;

[0046] 6. Close the water outlet valve 34 and use a stopwatch to record the start time (t 1 ) and end time (t 2 ), and record the initial water level reading in the graduated tube 5 (H 1 ) and the water level reading in the scale tube 5 at the end (H 2 );

[0047] 7. Substitute the above data into Formula 2 to calculate the saturated hydraulic conductivity of the soil.

[0048] In summary, the device for measuring soil saturated hydraulic conductivity disclosed in the utility model can measure soil saturated hydraulic conductivity by variable water head method or constant water head method by replacing variable water measuring component or fixed water measuring component, thus achieving dual purpose.

[0049] Of course, the present invention may have many other implementation modes. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A device for measuring soil saturated hydraulic conductivity, characterized in that: It comprises a variable water measuring component (1), a fixed water measuring component (2), and a sealing cylinder (3) with a through top; The interior of the sealing cylinder (3) is divided into a placement area (31) for placing soil samples and a water outlet area (32) from top to bottom in sequence by a water-permeable component (4). A water outlet pipe (33) penetrating the water outlet area (32) is provided on one side of the bottom of the sealing cylinder (3). The water outlet pipe (33) is provided with a water outlet valve (34) and is connected to a graduated tube (5) arranged in a vertical direction. The variable water measuring component (1) or the fixed water measuring component (2) can be detachably assembled on the top of the graduated tube (5).

2. The device for measuring soil saturated hydraulic conductivity according to claim 1, characterized in that: The variable water measuring component (1) comprises a fine graduated tube (11), the bottom of which is detachably connected to the graduated tube (5) via a transfer tube (12); the fixed water measuring component (2) comprises a vent tube (21), the vent tube (21) being detachably connected to the graduated tube (5) via a rubber stopper (22).

3. The device for measuring soil saturated hydraulic conductivity according to claim 2, characterized in that: The top port of the sealing cylinder (3) is detachably connected to a ring knife (7) for collecting soil samples via a connecting piece (6); the ring knife (7) and the placement area (31) together form a filling portion for filling the soil sample.

4. The device for measuring soil saturated hydraulic conductivity according to claim 3, characterized in that: The connecting member (6) comprises a connecting tube with two through ends, one end of the connecting tube being screwed onto the sealing tube (3) and the other end being screwed onto the ring cutter (7).

5. The device for measuring soil saturated hydraulic conductivity according to any one of claims 1 to 4, characterized in that: The graduated tube (5) is sleeved with an assembly sleeve (8) that can move up and down, and one side of the assembly sleeve (8) is provided with a positioning rod (9).

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