CN102735819A - Infiltrometer - Google Patents

Abstract

The invention discloses an imbibition meter, which comprises a soil cylinder arranged on the end surface of a horizontal plate surface, a vertical panel fixed on one edge of the horizontal plate surface, a water storage tank installed on the front of the vertical panel, and a water injection tank connected above the water storage tank. The water injection tank communicates downward with the bottom of the water storage tank, the upper part of the side of the water storage tank is provided with an exhaust valve, the lower part of the side of the water storage tank is provided with a water outlet valve; the upper part of the side of the soil cylinder is provided with a water inlet, and the water inlet is connected with the outlet valve of the water storage tank. The inner cavity of the soil cylinder is provided with a horizontal porous plate, which divides the inner cavity of the soil cylinder into a soil layer and a water storage layer, and the other side of the soil cylinder is provided with a water outlet. The device of the invention is small in size, easy to move and easy to operate, and is suitable for popularization and use in the teaching and experiment of measuring soil imbibition velocity and related parameters in a laboratory.

Description

Osmometer

technical field

The invention belongs to the technical field of measuring instruments for water infiltration in soil, and relates to an imbibition instrument.

Background technique

Soil water movement is the basis of the study of soil internal energy cycle. Macroscopically, both saturated and unsaturated soil water movement obey Darcy's law. In the unsaturated state, the imbibition rate is a variable, and its value changes with the soil moisture content. The lower the moisture content, the greater the imbibition rate; in the saturated state , the imbibition rate is constant. The imbibition rate is an important physical index of the soil, which reflects the water absorption and water permeability of the soil. The determination of this parameter is of great significance to the study of soil physical properties, and it is important to accurately guide agricultural field irrigation and better determine land use methods. role.

At present, there are many methods for measuring soil imbibition rate, such as: double-ring method, ring-knife method, artificial rainfall method, disc infiltration meter method, single-ring quantitative water addition method, instantaneous profile method, vertical infiltration flux method, vertical soil column method, etc. Stable evaporation method, horizontal soil column imbibition method, etc. Among the many measurement methods, the measurement instruments widely used in field in situ measurement are large in size, which limits the experimental site, and some instruments are expensive. The commonly used experimental device for measuring soil imbibition velocity in the laboratory is also relatively large in volume, and cannot measure the variation of imbibition velocity with time and the migration law of the wetting front in soil samples in a short period of time, and is not suitable for laboratory teaching. use.

Contents of the invention

The purpose of the present invention is to provide a kind of osmosis instrument, which solves the problem in the prior art that the volume of the experimental device is relatively large and the required parameters cannot be measured in a short period of time.

The technical scheme adopted in the present invention is that a kind of imbibition instrument comprises a horizontal plate surface, a soil cylinder is arranged on the end surface of the horizontal plate surface, a vertical panel is fixedly connected to one edge of the horizontal plate surface, and a water storage tank is installed on the front of the vertical panel surface , the top of the water storage tank is connected with a water injection tank, and the water injection tank is downwardly connected with the bottom of the water storage tank through the intake pipe, the upper part of the side of the water storage tank is provided with an exhaust valve, and the lower part of the side of the water storage tank is provided with a water outlet valve;

The upper part of the side of the soil cylinder is provided with a water inlet, which communicates with the water outlet valve of the water storage tank through a hose, and a horizontal perforated plate is installed at the lower part of the inner cavity of the soil cylinder, and the perforated plate divides the inner cavity of the soil cylinder into upper chambers. The soil layer and the water holding layer of the lower layer, and the lower part of the other side of the soil cylinder is provided with a water outlet near the bottom of the water holding layer.

The beneficial effect of the present invention is that, through the improved automatic water supply device simulating the soil moisture infiltration of the vertical soil column under the condition of constant accumulated water head, the whole process of soil moisture infiltration, including the free infiltration process, can be observed in a short period of time , jacking infiltration process and infiltration process, and the determination of the variation of imbibition speed with time, which can be extended to measure the soil permeability coefficient, and can also observe the advancement process of the soil wetting front. The instrument is simple in structure, small in size and easy to move, easy to operate It is simple and can be tested by multiple instruments at the same time. It is suitable for teaching and testing the soil imbibition rate in the laboratory.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of the osmometer measuring device of the present invention.

In the figure, 1. soil cylinder; 2. vertical panel; 3. horizontal panel; 4. water injection tank; 5. air intake pipe; 6. water storage tank; 7. exhaust valve; 8. nut; 9. outlet valve; 10. Perforated plate; 11. Water inlet of soil cylinder; 12. Water outlet of soil cylinder; 13. Loading soil layer; 14. Water holding layer; 15. Support; 16. One fixing bolt;

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Fig. 1, it is the structural representation of the imbibition instrument of the embodiment of the present invention, and this device structure is, comprises horizontal plate surface 3, is provided with soil tube 1 on the upper end surface of horizontal plate surface 3, and horizontal plate surface 3 bottom four Two angles are respectively provided with bearing 15, and vertical panel 2 is fixedly connected with one edge by horizontal panel surface 3, and vertical panel 2 front is equipped with water storage tank 6 by upper section, and water storage tank 6 is supported on vertical panel 2 front by fixing bolt 2 17, The top of the water storage tank 6 is connected with a water injection tank 4, and the water injection tank 4 is fixed on the vertical panel 2 front and the water storage tank 6 by fixing bolts 16, and the water injection tank 4 is downwardly connected with the bottom of the water storage tank 6 through the air intake pipe 5, and the water storage tank 6. An exhaust valve 7 is provided on the upper section of the side. The exhaust valve 7 is provided with a venting bolt and a matching nut 8. The nut 8 is provided with a round hole. The lower section of the side of the water storage tank 6 is provided with a water outlet valve 9;

The upper part of the side of the soil cylinder 1 is provided with a water inlet 11, and the water inlet 11 communicates with the water outlet valve 9 of the water storage tank 6 through a hose. The inner cavity of the cylinder 1 is divided into an upper soil-loading layer 13 and a lower water-holding layer 14, and the lower part of the other side of the soil cylinder 1 is provided with a water outlet 12 near the bottom of the water-holding layer 14.

Example 1

Set according to the following parameters:

The height of soil cylinder 1 is 20cm, and the diameter of the inner circle is 5cm. The inside of soil cylinder 1 is provided with perforated plate 10 (plate thickness 1cm) from bottom to top at 3cm. 11 is arranged at 4cm from top to bottom of soil cylinder 1, and water outlet 12 is arranged at 0.6cm from bottom to top of soil cylinder 1, which is equivalent to the lowest point of water-holding layer 14.

The water injection groove 4 is a square groove or a circular groove without a cover, and the bottom plate of the water injection groove 4 is provided with a round mouth, which is consistent with the diameter of the air intake pipe 5 and communicates.

Air intake pipe 5 bottoms are provided with corner, and the inflection point of air intake pipe 5 bottoms is higher than the height 2cm of water storage tank 6 outlet valves 9.

The water storage tank 6 has a cross-sectional area of 15 cm ² and a height of 25 cm, and the water storage tank 6 is a container made of transparent material, on which a ruler for observing the water level reading is arranged.

The imbibition meter of the present invention is used for measuring soil imbibition speed and wetting front migration law, and the operation steps are:

Step 1) Water storage tank 6 is filled with water. Open the water outlet valve 9 and the exhaust valve 7 of the water storage tank 6, the circular hole on the exhaust valve 7 communicates with the atmosphere, so that the remaining water in the water storage tank 6 is all flowed out, and the water outlet valve 9 is closed. With the measuring cup filled with water, fill water in the water injection tank 4, at this moment, water will flow into the air intake pipe 5 by the circular hole on the water injection tank 4 bottom plates, and enter in the water storage tank 6 by the air intake pipe 5 corners. In the process of adding water, the phenomenon of flow interruption can not occur in the water injection tank 4 . Water filling until when the water surface in the water storage tank 6 is slightly lower than the exhaust valve 7 height, close the exhaust valve 7. Slowly open the water outlet valve 9, and record the initial water level of the water storage tank 6.

Step 2) Make a soil sample. At first put a layer of qualitative filter paper with the same size as the inner diameter of the soil cylinder 1 on the perforated plate 10 to prevent soil from leaking out when loading the soil. The disturbed soil is packed into the soil barrel 1 layer by layer according to the bulk density requirement, and the soil filling height is 12 cm, which is just lower than the water inlet 11 of the soil barrel 1. After the soil cylinder 1 has installed the soil, the water outlet 9 of the water storage tank 6 is connected to the water inlet 11 of the soil cylinder 1 with a flexible pipe.

Step 3) Start the experiment. Cover the soil surface with a layer of filter paper. Use a measuring cup to measure the same amount of water as the 2cm high volume in the soil cylinder, quickly pour it into the soil cylinder, and then open the water outlet valve 9 of the water storage tank 6, and the water in the water storage tank 6 will supply water to the soil cylinder 1 through the water outlet. The scale on the water tank 6 reads the data until the bottom of the soil sample begins to flow out of water and reaches the infiltration state, and the water outlet 12 of the soil cylinder 1 has water flowing out and reaches stability, then the variation law of the soil imbibition rate can be measured. While measuring the amount of infiltration water, record the advance process of the soil wetting front in the soil until the wetting front reaches the bottom of the soil sample, then the change rule of the soil infiltration speed can be measured.

Measuring principle of the imbibition meter: Using the principle of equal pressure, according to the equilibrium condition of the isobaric surface, water is automatically supplied to the soil sample through the improved Marriott water supply device, so as to achieve continuous water supply and maintain a certain height of stagnant water infiltration head. Under the action of the soil water potential gradient, water infiltrates into the soil. As the observation time increases, the soil water infiltration successively goes through the free infiltration stage, the jacking infiltration stage and the infiltration stage, until water seeps through the soil sample and falls into the soil. The water holding layer 14 at the lower end of the soil cylinder 1 flows out from the water outlet 12, and the weight of the water flowing out is weighed within the experimental design observation time.

During the test, as the infiltration progresses, the cumulative infiltration below the soil surface and the distance of the wetting front are read accordingly, and the relationship between the cumulative infiltration and time is derived, which is the soil infiltration rate change over time. According to the Philip infiltration formula (1) with physical meaning:

$\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; St.</span>}}^{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, i is the infiltration rate, S is the infiltration rate, t is the infiltration time, and _if is the stable infiltration rate. The formula shows that at the initial stage of infiltration (when t is small), the soil is far from saturated and has a large If the water potential gradient is much larger than 1, the infiltration rate i is larger, and i is much larger than _if ; as the infiltration time increases, the water content of the topsoil increases, the soil suction decreases, and i decreases rapidly in an exponential linear fashion; After a certain period of infiltration, when the suction is zero and the water potential gradient is approximately equal to 1, the infiltration velocity will decrease and approach a constant value, and the infiltration rate close to this constant value is taken as the stable infiltration rate _if .

The stable infiltration rate if is the imbibition rate _K when the soil is saturated, the height of the soil sample is known L, the cross-sectional area of the soil cylinder is A, the amount of water infiltrated into the soil sample in time t is V, and the height of the constant water head is h. West's law, the calculation of saturated imbibition velocity is shown in the following formula (2):

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; VL</span>}}{\mathrm{<span\; class="notranslate">\; At</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

A series of imbibition velocities are calculated, and when these values approach a constant, it is assumed that this constant is the vertical saturated imbibition velocity.

By observing the advancement process of the soil wetting front, and deriving the relationship between the position of the wetting front and time, the infiltration speed of water in the soil can be obtained.

Claims (6)

1. A kind of imbibition meter, it is characterized in that: comprise horizontal plate surface (3), be provided with soil tube (1) on the upper end surface of horizontal plate surface (3), be fixedly connected with vertical plate by one edge of horizontal plate surface (3). A water storage tank (6) is installed on the front of the panel (2), and the vertical panel (2), and a water injection tank (4) is connected above the water storage tank (6), and the water injection tank (4) passes downward through the air intake pipe (5) and the water storage tank The bottom of (6) is connected, the upper part of the side of the water storage tank (6) is provided with an exhaust valve (7), and the lower part of the side of the water storage tank (6) is provided with a water outlet valve (9); The upper part of the side of the soil cylinder (1) is provided with a water inlet (11), and the water inlet (11) is connected with the water outlet valve (9) of the water storage tank (6) through a hose, and the inner cavity of the soil cylinder (1) is set at the lower position There is a horizontal perforated plate (10), and the perforated plate (10) divides the inner cavity of the soil cylinder (1) into an upper soil layer (13) and a lower water-holding layer (14), the other of the soil cylinder (1) A water outlet (12) is provided at the lower part of the side near the bottom of the water holding layer (14). 2. The osmosis meter according to claim 1, characterized in that: four corners at the bottom of the horizontal plate surface (3) are respectively provided with supports (15). 3. The imbibition meter according to claim 1, characterized in that: the water storage tank (6) is fixed on the front of the vertical panel (2) by fixing bolt two (17), and the water injection tank (4) is fixed by fixing bolt one (16) is fixed on the front of the vertical panel (2) and the water storage tank (6). 4. The osmosis meter according to claim 1, characterized in that: the exhaust valve (7) is provided with a deflation bolt and a matching nut (8), and the nut (8) is provided with a round hole. 5. The osmosis meter according to claim 1, characterized in that: the bottom end of the inlet pipe (5) is provided with an inflection point, which is 2cm higher than the height of the outlet valve (9) of the water storage tank (6). 6 . The osmosis meter according to claim 1 , characterized in that: the water storage tank ( 6 ) is a transparent container on which a measuring scale is arranged. 7 .