CN103792336A - Field soil water potential measuring instrument as well as using method thereof - Google Patents

Abstract

The invention provides an on-site soil water potential measuring instrument, comprising a base, an induction sleeve, an outer sleeve, a pressure sensor, the base is provided with a cavity and a cone bottom, the cone bottom of the base is provided with drainage holes, and the drainage The hole communicates with the cavity, one end of the pressure sensor extends into the cavity of the base and is tightly connected with the base, the outer sleeve is sleeved on the outside of the pressure sensor and the base, and the base surrounds the cavity A groove is opened, and a prefabricated water permeable hole is also opened on the base, the prefabricated water permeable hole communicates with the groove and the cavity, and the induction sleeve is sleeved on the base and sealed outside the groove. The on-site soil water potential measuring instrument of the present invention is assembled in air-free water to ensure that the internal cavity is free of air bubbles, and the saturation step is simple, the saturation effect is good, and it is not easy to vaporize; Good contact with soil. The invention also discloses a method for using the on-site soil water potential measuring instrument.

Description

An on-site soil water potential measuring instrument and its application method

technical field

The invention relates to an on-site soil water potential measuring instrument and a using method thereof.

Background technique

The water potential in the soil can not only reflect the dryness and wetness of the soil, but also effectively reflect the difficulty of plants absorbing water. Moreover, soil water potential is used as another variable different from stress in soil mechanics and other disciplines. Therefore, the measurement of soil water potential is very important, especially the on-site soil water potential measurement data is more valuable.

In the prior art, a soil tensiometer is usually used to measure the water potential (pore pressure) in the soil, which is widely used in agriculture, forestry, and geotechnical engineering. However, the saturation process of traditional tensiometers is complicated, easy to vaporize, and is greatly affected by temperature and soil lateral pressure. The positive pressure generated during installation will cause damage to the sensing parts, and it can only measure the surface soil water potential, which is not suitable for field use. Moreover, due to the complex conditions on site, the deep measurement position, the use is limited, the water potential induction is easily damaged during the installation process, and there is no vacuum saturation process, which results in poor saturation effect, poor measurement response time and accuracy, especially poor It is suitable for deep suction measurement, but it is only suitable for indoor experiments, and the process of burial cannot guarantee close contact with the soil.

Contents of the invention

In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides an on-site soil water potential measuring instrument, including a base, an induction sleeve, an outer sleeve, a pressure sensor, and the base is provided with a cavity and a cone bottom, and the cone of the base There is a drainage hole at the bottom, and the drainage hole is connected to the cavity. One end of the pressure sensor extends into the cavity of the base and is tightly connected with the base. The outer sleeve is sleeved on the pressure sensor. On the outside of the base, a groove is formed around the cavity on the outer periphery of the base, and a prefabricated water permeable hole is also opened on the base, the prefabricated water permeable hole communicates with the groove and the cavity, and the induction sleeve is socketed on the base and cover the outside of the groove.

Further, the base includes a base cavity wall and a conical bottom enclosing the cavity, and the groove is opened in the base cavity wall.

Further, the diameter of the prefabricated permeable holes is 2mm to 10mm.

Further, the diameter of the prefabricated permeable hole is 2mm.

Further, the on-site soil water potential measuring instrument is also provided with drain hole bolts and O-rings corresponding to the drain holes, and the drain hole bolts and O-ring seals are used to seal the drain holes.

Further, a gap of 0.5 mm to 2 mm is provided between the pressure sensor and the outer sleeve.

Further, the gap between the pressure sensor and the outer casing is 1.5mm.

A method for using an on-site soil water potential measuring instrument, said on-site soil water potential measuring instrument comprising a base, an induction sleeve, an outer sleeve, a pressure sensor and a drain hole bolt, said using method comprising the following steps:

Step 1: Unscrew the drain hole bolt, place the base and pressure sensor in a closed vacuum saturation tank; add anaerobic water to the vacuum saturation tank, so that the base and pressure sensor are submerged in the air-free water in the vacuum saturation tank; seal the vacuum Saturate the cylinder and evacuate it for 2 to 3 hours;

Step 2: Install the pressure sensor above the cavity of the base in air-free water;

Step 3: Slowly screw the drain hole bolt into the drain hole of the base in anaerobic water to seal the drain hole;

Step 4: Take out the base with the pressure sensor, and install the outer sleeve on its upper part;

Step 5: Install the above-mentioned on-site tensiometer to the desired location.

Further, the on-site soil water potential measuring instrument is also equipped with a cable and a data acquisition device, and the method of use further includes the following steps: Step 6: Connect the pressure sensor to the data acquisition device through a cable for data recording.

Further, the using method also includes the following steps: installing an O-ring in anaerobic water.

Compared with the prior art, the on-site soil water potential measuring instrument of the present invention is assembled in anaerobic water to ensure that there are no air bubbles in the internal cavity, and the saturation step is simple, the saturation effect is good, and it is not easy to vaporize, which is suitable for complex conditions on site; The positive pressure generated during the installation process is avoided to damage the sensing parts; the base is equipped with a cone bottom, which is more conducive to the installation of field instruments and can ensure good contact with the soil; the design of the force transmission step avoids the damage during the installation process. The impact force damages the sensing parts; the internal cavity volume is reduced, the reaction time is shortened, and it is suitable for water potential measurement at different depths; when there is side pressure outside, the pressure sensor is not stressed due to the protection of the outer sleeve, which avoids side pressure When the external temperature changes, due to the protection of the outer casing, the temperature will not quickly affect the pressure sensor.

Description of drawings

Fig. 1 is a structural schematic diagram of an on-site soil water potential measuring instrument of the present invention.

Detailed ways

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

Referring to FIG. 1 , the present invention provides an on-site soil water potential measuring instrument 10 , which includes a base 11 , an induction sleeve 13 , a pressure sensor 15 and an outer sleeve 17 . The base 11 is provided with a cavity 111 , the induction sleeve 13 is socketed on the base 11 , the pressure sensor 15 is partly disposed in the cavity 111 of the base 11 , and the outer sleeve 17 is socketed outside the pressure sensor 15 and the outer sleeve 17 . It can be understood that the on-site soil water potential measuring instrument 10 in this embodiment is also provided with a cable 21 and a data acquisition device 23, the cable 21 is connected to the pressure sensor 15 and the data sensed by it is transmitted to the pressure data acquisition device 23, which The structure, function and principle are consistent with the prior art, and will not be repeated here.

In this embodiment, the base 11 is generally in the shape of a conical bottom column, which includes a base cavity wall 113 enclosing the cavity 111 and a conical bottom 115 disposed at the bottom of the base cavity wall 113 . The cone bottom 115 is conical, which is convenient for on-site installation or setting of the on-site soil water potential measuring instrument 10, and is especially suitable for deep water potential measurement. In this embodiment, the base cavity wall 113 is enclosed in a column shape, and a cavity 111 is opened inside it. The cavity 111 is opened from the top of the base 11 and extends along the axial direction of the base 11 towards the cone bottom 115 of the base 11. The cavity 111 One end toward the cone bottom 115 is closed. In this embodiment, in order to improve the accuracy of the on-site soil water potential measuring instrument, the diameter of the cavity 111 is 5 mm to 10 mm, and the volume capable of accommodating a stressed water body is 0.5 mL to 10 mL. As a preferred manner, the inner cavity 111 has a diameter of 6mm and can accommodate a force-bearing water body with a volume of 5mL.

A groove 117 is defined on the outer peripheral surface of the base cavity wall 113 , and the induction sleeve 13 is sleeved on the base cavity wall 113 and sealed outside the groove 117 . The induction sleeve 13 has a gap between the induction sleeve 13 and the groove bottom of the groove 117 , so as to have a certain water capacity. The induction sleeve 13 is fixedly connected to the cavity wall 113 of the base 11 . In this embodiment, the assembled tensiometer used for deep soil water potential measurement is also provided with a gasket 31 , which is bonded to the outer sleeve 17 and arranged between the outer sleeve 17 and the induction sleeve 13 . The gasket 31 has a thickness of 1-5mm, and in a preferred manner, the gasket 31 has a thickness of 2mm. In this embodiment, the outer diameter of the induction sleeve 13 is consistent with the outer diameter of the cone bottom 115 , so that the on-site soil water potential measuring instrument 10 of the present invention can penetrate deep into the soil. In this embodiment, the induction sleeve 13 is made of a clay plate or a microporous plate with a high air intake value, and micropores are arranged on it to form a capillary effect. The maximum aperture of the micropores is 0.001 mm, and the air intake value is 100kPa. In this embodiment, the induction sleeve 13 is glued to the cone bottom 115 of the base 11 through epoxy resin, and the strength of the epoxy resin is 2 MPa.

A prefabricated permeable hole 119 connecting the groove 117 and the cavity 111 is provided between the groove 117 of the base 11 and the cavity 111 . In order to connect the cavity 111 with the induction sleeve 13, the diameter of the prefabricated permeable hole 119 is 2 mm to 10 mm. As a preferred mode, the diameter of the prefabricated permeable hole 119 is 2 mm.

The cone bottom 115 of the base 11 is provided with a drain hole 1151 , and the drain hole 1151 communicates with the cavity 111 of the base 11 . In the state of use, the drainage hole 1151 is set facing downward or obliquely downward. In order to avoid damage to the pressure sensor and sensing components by the positive pressure generated during the installation process, the diameter of the drainage hole 1151 is 2 mm to 5 mm. As a preferred manner, the diameter of the drainage hole 1151 is 2 mm. The on-site soil water potential measuring instrument 10 is also provided with a drain hole bolt 31 and an O-ring 33 corresponding to the drain hole 1151, and the drain hole bolt 31 and the O-ring seal 33 are used to seal the drain hole 1151 when necessary.

The pressure sensor 15 is tightly connected to the upper part of the cavity 111 and closely fits with the cavity wall 113 of the base. A gap of 0.5 mm to 2 mm is provided between the pressure sensor 15 and the outer sleeve. As a preferred manner, the gap between the pressure sensor 15 and the outer casing is 1.5mm. The pressure sensor 15 is used to measure positive pressure and negative pressure. The negative pressure range is -100kPa, and the positive pressure range is 100-1000kPa. As a preferred method, the positive pressure range is 100kPa. In this embodiment, a cavity wall step 1133 is provided inside the cavity wall 113 of the base, and the end surface of the pressure sensor 15 bears against the cavity wall step 1133 . An O-ring 33 is provided between the pressure sensor 15 and the cavity wall step 1133 .

The outer sleeve 17 is tightly sleeved on the upper part of the cavity wall 113 of the base. A force transmission step 173 is provided on the inner side of the outer sleeve 17, and the force transmission step 173 is used to prevent the longitudinal axial force from being transmitted to the induction sleeve 13, causing damage to the induction component. It can be understood that the on-site soil water potential measuring instrument 10 of the present invention can use a plurality of outer sleeves 17 to be spliced together so as to obtain a required length. The length of each outer casing 5 is 1m to 4m, and as a preferred mode, the length of each outer casing 5 is 2m.

A method for using an on-site soil water potential measuring instrument 10, comprising the steps of:

Step 1: Unscrew the bolt 31 of the drainage hole, place the base 11 of the tensiometer body and the pressure sensor 15 in a closed vacuum saturation cylinder; add anerated water to the vacuum saturation cylinder to make the anaerobic water in the vacuum saturation cylinder Submerge the existing base 11 and the pressure sensor 15; cover the lid of the vacuum saturation cylinder, seal the vacuum saturation cylinder, and vacuumize the cylinder for 2 to 3 hours, so as to saturate after separation and make the saturation effect better;

Step 2: Install the pressure sensor 15 above the cavity 111 of the base 11 in air-free water;

Step 3: Slowly screw the drain hole bolt 31 into the drain hole 1151 of the base 11 in air-free water to seal the drain hole 1151;

Step 4: Take out the base 11 equipped with the pressure sensor 15, and install the outer sleeve 17 on its top;

Step 5: Install the above-mentioned on-site tensiometer to the designed position by using a static or dynamic device. When the measured depth is greater than the length of one section of the outer casing, multiple sections of the outer casing can be spliced during the installation process until the design depth is reached.

Step 6: Connect the cable 21 of the pressure sensor 15 to the data acquisition device 23, and record the data;

The using method also includes the following steps: installing the O-ring 33 in anaerobic water.

The on-site soil water potential measuring instrument 10 of the present invention is assembled in air-free water to ensure that the internal cavity 111 has no air bubbles, and the saturation step is simple, the saturation effect is good, and it is not easy to vaporize, which is suitable for complex conditions on site; the drainage hole 1151 is set to avoid the installation process The positive pressure generated in the medium will damage the sensing parts; the base 11 is equipped with a cone bottom 115, which is more conducive to the installation of on-site instruments, and can ensure good contact with the soil; the design of the force transmission step 173 avoids the impact during the installation process The force damages the sensing parts; the volume of the internal cavity 111 is reduced, the reaction time is shortened, and it is suitable for water potential measurement at different depths; when there is lateral pressure outside, the pressure sensor 15 is not stressed due to the protection of the outer sleeve, which avoids lateral pressure. The influence of pressure; when the external temperature changes, due to the protection of the outer sleeve, the temperature will not quickly affect the pressure sensor 15 .

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. an on-site soil flow of water measuring instrument, it is characterized in that: comprise base, induction sleeve, outer sleeve, pressure transducer, described base is provided with cavity and the cone end, at the bottom of the cone of described base, offer osculum, described osculum is communicated in cavity, one end of described pressure transducer is stretched in the cavity of described base and is closely connected with described base, described outer sleeve is socketed on described pressure transducer and chassis outer side, described base outside offers groove around described cavity, on described base, also offer prefabricated permeable hole, described prefabricated permeable hole is communicated with described groove and cavity, described induction jacket casing is connected to described base and is covered in this groove outside.

2. on-site soil flow of water measuring instrument according to claim 1, is characterized in that: described base comprises and enclose the base cavity wall and the cone end that form described cavity, and described groove is opened in described base cavity wall.

3. on-site soil flow of water measuring instrument according to claim 1, is characterized in that: described prefabricated permeable hole diameter is 2mm to 10mm.

4. on-site soil flow of water measuring instrument according to claim 3, is characterized in that: described prefabricated permeable hole diameter is 2mm.

5. on-site soil flow of water measuring instrument according to claim 1, is characterized in that: the corresponding osculum of described on-site soil flow of water measuring instrument is also provided with osculum bolt and O RunddichtringO, and described osculum bolt and O RunddichtringO are used for sealing osculum sealing.

6. on-site soil flow of water measuring instrument according to claim 1, is characterized in that: the gap that is provided with 0.5mm to 2mm between described pressure transducer and outer tube.

7. on-site soil flow of water measuring instrument on-site soil flow of water measuring instrument according to claim 6, is characterized in that: the gap between described pressure transducer and outer tube is 1.5mm.

8. a using method for on-site soil flow of water measuring instrument, described on-site soil flow of water measuring instrument comprises base, induction sleeve, outer sleeve, pressure transducer and osculum bolt, it is characterized in that: described using method comprises the following steps:

Step 1: turn on osculum bolt, base and pressure transducer are placed in to the saturated cylinder of vacuum of sealing; Add air free water to the saturated cylinder of vacuum, make air free water submergence base and pressure transducer in the saturated cylinder of vacuum; The saturated cylinder of sealed vacuum, and vacuumize 2 to 3 hours;

Step 2: in air free water, pressure transducer is mounted to above the cavity of described base;

Step 3: osculum bolt is slowly screwed into the osculum of base in air free water, sealing osculum;

Step 4: take out the base that pressure transducer is housed, outer sleeve is installed at an upper portion thereof;

Step 5: described on-the-spot tensiometer is mounted to desired location.

9. the using method of on-site soil flow of water measuring instrument according to claim 8, it is characterized in that: described on-site soil flow of water measuring instrument is also provided with cable and data collector is seen, described using method is further comprising the steps of: step 6: by cable, pressure transducer is connected to data collector and carries out data recording.

10. the using method of on-site soil flow of water measuring instrument according to claim 8, is characterized in that: described using method is further comprising the steps of: mounting O-shaped O-ring seal in air free water.

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