CN204439487U - A kind of system utilizing centrifuge method to measure characteristic curve of soil moisture - Google Patents

Abstract

The utility model discloses a system for measuring the characteristic curve of soil moisture by using a centrifuge method, which comprises a centrifuge, a centrifuge tube, a water collection cylinder, a magnetostrictive ruler, a balance cylinder and a baffle plate, wherein the centrifuge has a rotating shaft, a turntable and a display screen; the bottom of the centrifuge tube has a water outlet hole, and the cap of the centrifuge tube has a measuring hole; the water collecting cylinder includes a cylinder body, a water collecting partition, a one-way water valve, a waterproof and breathable valve, and a threaded water inlet and a The threaded air hole is used to collect the water discharged from the soil sample; the magnetostrictive ruler is installed on the cap of the centrifuge tube to measure the expansion and contraction of the soil sample; the balance cylinder is used to ensure the balance of the centrifuge turntable. The utility model can calculate and correct the water content of the soil sample according to the compression amount and displacement of the soil sample, and can measure the characteristic curve of the soil sample according to the soil water potential corresponding to the centrifugal speed, and the result is more accurate, and at the same time, it is not necessary to complete the measurement every time Finally, the water is poured out, weighed and rebalanced, which saves the measurement steps.

Description

A System for Measuring Soil Moisture Characteristic Curve Using Centrifuge Method

technical field

The utility model relates to a measuring system for soil moisture characteristic curves, in particular to a system for measuring soil moisture characteristic curves by using a centrifuge method.

Background technique

Soil moisture characteristic curve is generally also called soil moisture characteristic curve or soil pF curve, which expresses the relationship between soil water potential and soil moisture content. It is an essential parameter to study the hydrodynamic properties of soil, and it is of great significance in production practice.

The method of directly measuring the soil moisture characteristic curve by experimental method is called direct method. There are many laboratory and field methods in the direct method, such as tensiometer method, pressure membrane method, centrifuge method, sand core funnel method, equilibrium water vapor pressure method, etc., and the first three are the most commonly used:

Tensiometer method - the soil absorbs water from the tensiometer through the clay cup to create a certain vacuum or suction. When the soil reaches equilibrium with the outside world, the soil matrix potential is measured, and then the soil moisture content around the clay cup is measured. By changing the soil moisture content and measuring the corresponding suction, the determination of the soil moisture characteristic curve can be completed. The tensiometer method can be used in two processes of dehydration and water absorption, and can measure the characteristic curves of disturbed soil and undisturbed soil. It is an important means for monitoring the dynamic changes of soil moisture in the field and has been widely used in practical work. But the tensiometer can only measure the characteristic curve of low suction range 0-0.08Mpa.

Pressure film method - is to pressurize the soil water to flow out, causing the soil matric potential to decrease until the matric potential is balanced with the applied pressure, and measure the soil water content at this time. By changing the pressure and gradually obtaining the water content under different pressures, it can be obtained Moisture characteristic curve. The pressure membrane method can be applied to disturbed soil and undisturbed soil. The shape of the measured characteristic curve is consistent with the inherent characteristic curve of the soil. It can be applied to the dynamic simulation of soil moisture, but the measurement cycle is long and there is a problem of soil bulk density change.

Centrifuge method - to measure the water content corresponding to a certain suction force, the principle and experimental process are similar to the pressure membrane method, but the pressure comes from the centrifugal force generated by the high-speed rotation of the centrifuge. The centrifuge method can be applied to disturbed soil and undisturbed soil, and the measurement period is short. The relative shape of the characteristic curve matches the inherent characteristic curve of the soil, which can be used for soil moisture dynamic simulation. However, the centrifuge can only measure the dehydration process, and the soil bulk density changes greatly during the measurement process. If the influence of the bulk density can be corrected, it is expected to have a higher measurement accuracy. Shao Mingan (1985) preliminarily studied the difference and accuracy of the above three methods for measuring soil matric potential from the degree of deviation between the prediction of soil evaporation test and the measured water content. The results showed that the centrifuge method considering the change of bulk density has higher accuracy. .

The current measurement process of the centrifuge method is: after taking the soil with a ring knife, soaking it in water to saturate it, then putting it into a centrifuge tube, and measuring the soil moisture content under different centrifugal forces. The disadvantage is that the centrifuge tube needs to be taken out and weighed after each speed is turned, poured out the centrifuged water, and then put into the centrifuge after balancing, so the process is cumbersome and complicated; at the same time, the bulk density will increase during the process of measuring the characteristic curve of soil moisture by centrifugation. Changes will have a greater impact on the accuracy of the soil moisture characteristic curve, so the change in soil bulk density needs to be measured during the measurement process, so that the model can be used to revise the soil moisture characteristic curve.

Utility model content

In order to solve the above-mentioned problems in the prior art, the utility model provides a system for measuring the characteristic curve of soil moisture by using the centrifuge method.

The technical scheme adopted by the utility model is: a system for measuring the soil moisture characteristic curve by using the centrifuge method, including a centrifuge, a centrifuge tube, a water collection tube, a magnetostrictive ruler, a balance tube, and a baffle, wherein:

The inside of the centrifuge has a rotating shaft and a turntable, and the outside of the centrifuge has an operation display screen for setting and displaying centrifugation parameters;

The centrifuge tube is arranged on the turntable of the centrifuge, including a tube body, a tube cover and a tube bottom, wherein the tube body and the tube bottom are integrally structured, the tube body is a cylindrical structure, and the middle part of the tube cover is provided with a measuring hole, the bottom of the tube is provided with a water outlet hole, the inside of the tube body is provided with a filter plate matching the inner diameter of the tube body near the bottom of the tube, and the tube body and the bottom of the tube are provided with interconnected air holes;

The water collection tube is set on the bottom of the centrifuge tube. The water collection tube includes a cylinder body, a detachable water collection partition located inside the cylinder body, a one-way water valve and a waterproof and breathable valve. The water collection partition and the cylinder body Combined to form a closed hollow structure, the water collecting partition is provided with a threaded water outlet hole, the water inlet end of the one-way water valve is installed on the threaded water outlet hole through threaded connection, and the water outlet end of the one-way water valve is set In the hollow structure formed by the water-collecting partition and the cylinder body, the water-collecting partition is provided with a stepped protrusion, and the stepped protrusion is provided with a threaded air hole, and the waterproof and breathable valve is arranged on the water-collecting partition. In the hollow structure formed by the plate and the cylinder body, it is installed on the threaded air hole through threaded connection;

The magnetostrictive ruler includes a long rod, a main body, a position magnet, a display instrument and a wire, wherein the long rod extends into the inside of the centrifuge tube through a measuring hole in the middle part of the tube cover of the centrifuge tube, and the main body is located in the centrifuge tube Outside the tube cover, the position magnet is set on the long rod and set in the centrifuge tube, and the display is set on the top of the centrifuge shaft and connected to the main body through wires;

The baffle plate is a circular plate with a round hole in the center, the baffle plate is installed on the long rod of the magnetostrictive ruler and is located between the position magnet and the bottom of the cylinder, and the radius of the baffle plate is smaller than the inner diameter of the centrifuge tube ;

The balance tube is arranged on the turntable of the centrifuge, and is symmetrical to the center of the centrifuge tube relative to the rotating shaft of the centrifuge.

Under the action of centrifugal force generated by high-speed rotation, the water contained in the soil sample flows out through the filter plate and through the water outlet hole, and then enters the interior of the water collection cylinder through the threaded water outlet hole and the one-way water valve on the water collection separator and collects it. The air in the water collection tube can be discharged out of the centrifuge tube through the waterproof breathable valve and the air hole, and it is guaranteed that the water will not leak out so that the test result is inaccurate. At the same time, the soil sample will be compressed under the action of centrifugal force, and the position magnet of the baffle and the magnetostrictive ruler slides on the long rod together with the depth change of the soil sample, while the baffle prevents the position magnet from sinking into the soil sample and causing The test results are inaccurate.

Compared with the prior art, the utility model has the beneficial effects of:

①This utility model uses centrifugal force to provide pressure for the soil sample, and the water discharged from the soil sample at a certain rotational speed is introduced into the water collecting cylinder through the water outlet hole, the water collecting partition, and the one-way water valve for collection, and the water under the corresponding centrifugal force is calculated by weighing. Displacement, no need to pour out and measure the water discharged at each set speed, so only one balance is needed, no need to pour out water and balance again after each measurement, which greatly reduces the measurement steps;

② The utility model adopts a one-way water valve to prevent the water from flowing backwards, which ensures the accuracy of the measurement results;

③The utility model can effectively prevent the soil particles from coming out through the outlet hole and block the water collecting hose by setting the filter plate in the centrifuge tube;

④ The utility model can directly read the soil expansion and contraction at each set speed through the magnetostrictive ruler, thereby calculating the bulk density of the soil sample at each set speed, and then correcting the water content of the soil sample, so that The measured moisture characteristic curve is more accurate, and the measurement steps are simple and easy to operate.

Description of drawings

Fig. 1 is the overall schematic diagram of the utility model.

Fig. 2 is the structure schematic diagram of centrifuge tube, water collection cylinder and magnetostrictive scale described in the utility model.

In the figure: 1-centrifuge, 11-rotating shaft, 12-turntable, 13-operation display, 2-centrifuge tube, 21-tube body, 22-tube cover, 23-tube bottom, 24-measurement hole, 25-water outlet Hole, 26-filter plate, 27-air hole, 3-water collecting cylinder, 31-cylinder body, 32-water collecting partition, 33-one-way water valve, 34-waterproof and breathable valve, 35-thread outlet hole, 36-thread Air hole, 4-magnetostrictive ruler, 41-long rod, 42-main body, 43-position magnet, 44-display instrument, 45-wire, 5-balance tube, 6-baffle plate, 7-ring knife, 8-soil sample.

Detailed ways

The technical scheme of the utility model is further described in conjunction with the accompanying drawings and embodiments.

As shown in Fig. 1 and Fig. 2, the technical scheme adopted by the utility model is: a kind of system utilizing the centrifuge method to measure the characteristic curve of soil moisture, comprising a centrifuge 1, a centrifuge tube 2, a water collection cylinder 3, and a magnetostrictive ruler 4 , balance tube 5, baffle plate 6, wherein:

The inside of the centrifuge 1 is provided with a rotating shaft 11 and a turntable 12, and the outside of the centrifuge 1 is provided with an operation display screen 13 for setting and displaying centrifugal parameters;

As shown in Figure 2, the centrifuge tube 2 is arranged on the centrifuge turntable 12, including a tube body 21, a tube cover 22 and a tube bottom 23, wherein the tube body 21 and the tube bottom 23 are integrally structured, and the tube body 21 is a cylindrical structure, the middle part of the tube cover 22 is provided with a measuring hole 24, the tube bottom 23 is provided with a water outlet hole 25, and the inside of the tube body 21 near the tube bottom 23 is provided with a size matching the inner diameter of the tube body 21. The filter plate 26, the tube body 21 and the bottom 23 of the tube are provided with interconnected air holes 27; the water collecting tube 3 is set on the bottom of the centrifuge tube 2, and the water collecting tube includes a tube body 31, which is located on the tube body The internal detachable water-collecting baffle 32, one-way water valve 33 and waterproof breathable valve 34, wherein the water-collecting baffle 32 is combined with the cylinder body 31 to form a closed hollow structure; the water-collecting baffle 32 is provided with There is a threaded water outlet hole 35, the water inlet end of the one-way water valve 33 is installed on the threaded water outlet hole 35 through threaded connection, and the water outlet end of the one-way water valve 33 is set on the water collecting partition 32 and the cylinder body 31 to form In the hollow structure; the water-collecting partition 32 is provided with a stepped protrusion, and the stepped protrusion is provided with a threaded air hole 36, and the waterproof and breathable valve 34 is arranged on the water-collecting partition 32 and the cylinder body 31 In the hollow structure that forms and be installed on the threaded air hole 36 by screw connection; Described magnetostrictive ruler 4 comprises long rod 41, main body 42, position magnet 43, display instrument 44 and lead wire 45, wherein said long rod 41 passes through the The measuring hole 24 in the middle part of the tube cover 22 of the centrifuge tube 2 extends into the inside of the centrifuge tube 2, the main body 42 is arranged outside the tube cover 22, the position magnet 43 is sleeved on the long rod 41 and is arranged in the centrifuge tube 2, Described display instrument 44 is located at the top of centrifuge rotating shaft 11 and connects main body 42 by lead wire 45; On the rod and between the position magnet 43 and the cylinder bottom 23, the radius of the baffle plate 6 is less than the inner diameter of the centrifuge tube 2; The machine shaft 12 is symmetrical about the center.

The utility model uses the centrifugal force generated by high-speed rotation as the pressure, uses the ring 7 knife to take the soil sample 8 and puts it into the centrifuge tube 2 after being soaked to saturation, and then starts to set the speed for measurement, wherein the water discharged by the soil sample 8 is filtered plate 26 and flows out through the water outlet hole 25, and then enters the inside of the water collecting tube 3 through the threaded water outlet hole 35 and the one-way water valve 33 on the water collecting partition 31 and collects it. The air in the water collecting tube 3 can be passed through the waterproof The breathable valve 34 and the air hole 27 are discharged to the outside of the centrifuge tube 2, and it is ensured that the water will not leak out so that the test result is inaccurate, and then the water displacement at the corresponding speed can be calculated by weighing the water collecting cylinder 3, which avoids the need for prior art After each measurement, the water must be poured out, weighed and rebalanced; at the same time, the height change of the soil sample can be directly measured through the magnetostrictive ruler 4, and the bulk density of the soil sample at the set speed can be obtained through calculation And the water content of the soil sample 8 is corrected, the operation is simple, the measurement steps and workload are saved, and the measured water characteristic curve is more accurate.

Claims (1)

1. the system utilizing centrifuge method to measure characteristic curve of soil moisture, it is characterized in that, comprise hydro-extractor (1), centrifuge tube (2), Water collecting tube (3), magnetostriction chi (4), balance pipe (5), baffle plate (6), wherein:

The inside of described hydro-extractor (1) is provided with rotating shaft (11) and rotating disk (12), and the outside of described hydro-extractor (1) is provided with operating display (13);

Described centrifuge tube (2) is located on the rotating disk (12) of hydro-extractor (1), comprise pipe shaft (21), at the bottom of pipe lid (22) and pipe (23), wherein said pipe shaft (21) is structure as a whole with (23) at the bottom of pipe, described pipe shaft (21) is cylindrical structural, described pipe lid (22) middle part is provided with measured hole (24), (23) at the bottom of described pipe are provided with apopore (25), at the bottom of the inner close pipe of described pipe shaft (21), (23) place is provided with the filter plate (26) matched with pipe shaft (21) internal diameter size, at the bottom of described pipe shaft (21) and pipe, (23) are provided with the pore (27) interconnected,

Described Water collecting tube (3) is sleeved on the bottom of centrifuge tube (2), described Water collecting tube (3) comprises stack shell (31), be located at dismountable dividing plate that catchments (32) that stack shell (31) is inner, water check valve (33) and waterproof vent valve (34), the described dividing plate that catchments (32) and stack shell (31) are combined to form closed hollow structure, the described dividing plate that catchments (32) is provided with screw thread apopore (35), the water inlet end of described water check valve (33) is threaded connection and is arranged on screw thread apopore (35), the water side of described water check valve (33) is located in the hollow structure that the dividing plate that catchments (32) and stack shell (31) formed, the described dividing plate that catchments (32) is provided with stepped appearance projection, described stepped appearance high spot is provided with threaded air vent (36), described waterproof vent valve (34) to be located in hollow structure that the dividing plate that catchments (32) and stack shell (31) formed and to be threaded connection and is arranged on threaded air vent (36),

Described magnetostriction chi (4) comprises stock (41), main body (42), position magnet (43), display instrument (44) and wire (45), it is inner that wherein said stock (41) stretches into centrifuge tube (2) by the measured hole (24) at pipe lid (22) middle part of described centrifuge tube (2), it is outside that described main body (42) is located at pipe lid (22), described position magnet (43) is enclosed within stock (41) and goes up and be located in centrifuge tube (2), described display instrument (44) is located at the top of hydro-extractor rotating shaft (11) and is connected main body (42) by wire (45),

Described baffle plate establishes round-meshed circular slab centered by (6), the stock that described baffle plate is installed on magnetostriction chi (4) is positioned at the bottom of position magnet (43) and cylinder between (23), and the radius of described baffle plate (6) is less than the internal diameter of centrifuge tube (2);

Described balance pipe (5) is located on the rotating disk (12) of hydro-extractor (1), and symmetrical centered by hydro-extractor rotating shaft (12) relative to centrifuge tube (2).