CZ24682U1 - Infiltrometer for measuring soil coefficient of conductivity - Google Patents

Description

Infiltrometer for hydraulic soil conductivity measurement

Technical field

The infiltrometer is used to determine the infiltration capacity of soils, in particular to determine the individual points of the function of unsaturated hydraulic conductivity in the vicinity of soil saturation with water and to follow the course of unsaturated hydraulic conductivity in relation to (suction) pressure altitude, which expresses the soil water potential. The course of hydraulic conductivity refers to the rate of water flow through the soil at a unit gradient of the total potential to a certain humidity, and at the same time, through the retention curve, to the pressure head. Hydraulic conductivity has units of speed [L / T]. The course of hydraulic conductivity serves as one of the input parameters of models of water flow in unsaturated soil environment, ie, above groundwater level.

BACKGROUND OF THE INVENTION

In general, the use of infiltrometers directly measures the level or volume drop over time in the instrument storage vessel at a constant set pressure value (ho). The pressure head is normally given in units of length [L] and is always set to negative to determine the values of unsaturated hydraulic conductivity. The development of cumulative infiltration, in length units [L], into the soil over time is then calculated from the level decrease. This recalculation is performed after the end of the infiltration test during its evaluation or is directly part of the measurement, if the instrument is automated and the conversion of the level drop to the cumulative infiltration is introduced into the control program. Thus, one infiltration test results in a cumulative infiltration over time, which serves as a basis for determining one unsaturated hydraulic conductivity at a given pressure altitude. In order to obtain an additional value of unsaturated hydraulic conductivity, a new infiltration test with a different pressure head value is required.

At present, there are more designs of infiltrometers. However, many of them do not comply with the measurement productivity due to the absence of measurement automation. On the other hand, existing designs of automatic infiltrometers are generally structurally complex and prone to damage. It is also necessary to differentiate between overpressure devices (eg CZ 300463 B6) and vacuum methods, where the first method determines the value of saturated hydraulic conductivity, while the second method determines the individual points of unsaturated hydraulic conductivity.

As a basic instrument of the vacuum infiltration meter family, the disc vacuum infiltration meter designed by Perroux, K.M. and White, I. 1988. Design for disc permeameters. Soil Sci. Soc. Am. J., 52: 1205 - 1215. In its basic version, this instrument is not automated, it is bulky and uneconomical in terms of water consumption, and due to the larger size of the disc, the preparation of the surface of the soil before measurement is lengthy. The disadvantage of the absence of an automatic mode is eliminated, for example, by the US patent US4884436 or by the solution described in Špongrová, K., Kechavarzi, C., Dresser, M., Matula, S., Godwin, R.J. Vadose Jumal Zone. 8: 810-817, where both structures use pressure sensors to automate measurements. Such an automation method often suffers from pressure oscillation when bubbles are released from the aeration line, leading to measurement inaccuracies and, in addition, water consumption and equipment size problems remain in both embodiments. In the case of U.S. Pat. No. 4,884,436, the use of a blade at the bottom of the apparatus may also be problematic, which can be very difficult to push into the depth necessary to make contact between the soil surface and the porous plate in skeletal soils or in areas with rich plant or tree root systems. The same problem with the installation of the device can also occur with the German patent DE 102009045029 A1 of Umwelt Gerate Technik, GmbH. However, it does not use any porous medium for contact with the surface of the soil and water thus comes into direct contact with its surface. developed macropores limits its applicability. Furthermore, the solution according to DE 102009045029 A1 is characterized by a high degree of articulation, weight of the apparatus and high water consumption.

- 1 CZ 24682 Ul

In order to achieve good mobility of the vacuum infiltrometer, to ensure low water consumption, as well as to save time in preparing the soil surface before infiltration, it is advisable to use a solution with a small size of the infiltrating porous disk. Such devices are referred to as mini-disc vacuum infiltrometers. A simple instrument in this group is that of Decagon Devices, Inc., Washington, USA, which does not allow automatic measurement. A method of automating a mini-disk infiltrometer is described in Madsen, M. D. and D. G. Chandler. 2007. Automation and use of mini disk infiltrometers. Soil Sci. Soc. Am. J. 71: 1469 - 1472. This involves the automation of the release of bubbles from the aeration pipe and the aeration of the pressure sensors themselves.

Current methods of level measurement using a float are described, for example, in Czech Patent No. 99322, US 5585786 or US 7860671 B1. However, all these devices and others use a movable float to measure the level in conjunction with various types of sensors. Movable float solutions are much more complex in design and thus prone to failure and are often energy intensive and therefore unsuitable for field use due to the sensors used.

The essence of the technical solution

These disadvantages are eliminated by an automatic vacuum mini-disc infiltrometer, hereinafter referred to as an infiltrometer, used to measure the unsaturated hydraulic conductivity near saturation, consisting of an infiltration module, an external Mariott cylinder (to set a constant vacuum value at the infiltration module and data logger outlet). for automatic data collection, which according to the invention consists in that the infiltration module consists of a storage tube on which an infiltration extension with a sintered plate is inserted in the lower part and the head of the infiltration module in which the weighing module is located a sensor on which a fixed float is fixed, and parallel to the fixed float, but not below its lower edge, is guided an aeration tube fixed to the aeration tube grommet at the head of the infiltration module, in addition, a cable gland is provided in the infiltration module head for pulling the signal cable out of the infiltration module head space; and a push-in fitting that connects the vent tube located inside the infiltration module head to the vent hose that is connected to the hand pump located outside the infiltration module.

O-rings are inserted into the grooves between the storage tube and the infiltration module head, and O-rings are inserted into the grooves between the storage tube and the infiltration extension. The stationary float is terminated by a conical surface preventing the trapping of bubbles.

All three parts of the infiltrometer, namely the infiltration module, the recording unit and the Mariott bottle, are separable from each other.

Water from the storage tube penetrates the soil through a stainless steel sinter plate at the bottom of the infiltration module, below a constant vacuum value set in the Mariott bottle and maintained at the end of the aeration tube within the infiltration module. The amount of infiltrated water is recorded as a cumulative drop in the level in the storage tube. This level drop is monitored by changing the buoyancy transmitted by the stationary float to the weighing sensor built into the head of the infiltration module. The level change is recorded by a data logger with which the weighing sensor is connected by a signal cable passing through a tight cable gland screwed into the ceiling of the infiltration module head.

The length of the stationary float and its diameter are chosen with respect to the storage tube size so that the ratio of the buoyancy force acting on the weighing sensor at the maximum level in the infiltration module to the storage tube volume is as large as possible. tube. The geometrical arrangement of the stationary float, the aeration tube and the vent tube in the space of the supply tube shall be chosen so that they

-2684682 The UL does not touch and the water level measurement in the supply tube is not affected. The lower portion of the stationary float is terminated by a conical surface that effectively prevents the possibility of trapping bubbles below the stationary float body, which would contribute to an increase in buoyancy on the stationary float and cause errors in the level measurement in the supply tube.

A small sintered plate diameter was chosen for easy preparation of the measurement and with respect to the overall dimensions of the device, which was trying to minimize and at the same time maintain a high measuring efficiency. A high quality stainless steel was chosen as the material for its production.

Filling the instrument storage tube is done by immersing the infiltration attachment in any water container and extracting air by hand pump from the storage tube through the vent tube and vent hose mounted in the push-in connector in the infiltration module head, causing water to be sucked through the sinter plate.

This solution also reduces wear on the O-rings of the infiltration module and its contact surfaces, since there is no need to disassemble the infiltration module to fill it. The breather tube extends into the supply tube only a few centimeters below the level of attachment of the weighing sensor so that it does not flood and significantly exceed the maximum capacity of the storage tube.

Another part of the infiltration module is the aforementioned aeration tube, which is fixed in the infiltration module head into the ventilation tube grommet, to the end of which extends above the infiltration module head is an aeration tube connecting the infiltration module to the external Mariott bottle. it is possible to adjust the value of the vacuum applied to the end of the aeration tube. The level of the end of the aeration tube is chosen to open above the lower edge of the stationary float. The opening of the aeration tube is tapered so that the bubbles are easily released from the end of the aeration tube towards the wall of the storage tube, so that their effect on the level measurement on release is minimized.

The complete infiltrometer consists of an infiltration module, an external Mariott bottle used to set a constant vacuum value at the infiltration module outlet and a data logger for automatic data acquisition. The recording unit ensures the recording of measurement data by a weighing sensor, which is connected by a signal cable, which is led through a cable gland through the ceiling of the infiltration module head. In the same way, the vent tube is connected, which is fastened in the bushing for the vent tube. The infiltration module is connected to the Mariott bottle by an air hose connected at one end to the aeration tube and to the other by an angled push-in fitting screwed into the lid of the Mariott bottle, centered with a sliding tube allowing the vacuum to be adjusted. sealed with a pair of O-rings.

The infiltration module consists of the infiltration module head, with a fixed weighing sensor, on which a fixed float is screwed and terminated at its end by a conical surface. From the supply tube to which the head of the infiltration module is slid in its upper part, in the same way as the infiltration attachment with a sintered plate inserted in its lower part, the sealing of the interface is in each case ensured by three O-rings. From the venting tube inserted in the inner part of the infiltration module head into a push-on coupling, into which the venting hose with a hand pump is connected on the outside of the infiltration module head. It is further comprised of a vacuum tube for application of a vacuum that is mounted in a bushing for the ventilation tube screwed into the head of the infiltration module and which connects the infiltration module to the Mariott bottle via the ventilation tube. In the same way as the vent hose, the signal cable for connecting the weighing sensor to the data logger is routed through a cable gland screwed into the head of the infiltration module.

After filling the supply tube and adjusting the required pressure head on the Mariott bottle and then applying it to the soil surface and establishing a hydraulic connection between the soil surface and

The sinter plate measures the drop in the storage tube. The measurement of the water level drop in the storage tube or the cumulative infiltration carried out by the proposed technical solution is mediated by a change in buoyancy acting on a fixed float mounted on the weighing sensor, which causes the weighing sensor to respond in the form of output voltage. This response is converted into a level decrease or cumulative infiltration by a calibration relationship. The advantage of this embodiment of automation over other solutions is less sensitivity to pressure surges caused by the release of bubbles from the aeration tube during infiltration. Unlike pressure sensor solutions, the measuring instrument cannot be ventilated and the measured data cannot be degraded. By using a stationary float, you can adjust the length and diameter of the float to any measurement sensitivity and size of the storage space.

Particular attention must be paid to the perfect sealing of the entire system, and therefore sealed joints such as tubing connections and O-rings in the area of the infiltration module head and infiltration attachment can be additionally supplemented with a thin film of vacuum grease.

None of these devices combines the advantages of a mini-disk inline meter, ie high mobility, low water consumption and easy measurement preparation with automated level measurement in the infiltrometer using a fixed float whose buoyancy is measured by a weighing sensor. The main advantages of the infiltration module can be summarized as follows:

- compact module design

- easy handling (transport, low water consumption)

- due to the small diameter of the disc (sinter plate), easy preparation of the soil surface for measurement

- simple principle of level measurement with good resolution and measurement reliability

- possibility to connect several infiltration modules to one datalogger

- The assembly is therefore easy to dismantle and can be transported to locations with limited accessibility by means of transportation without great difficulty.

Overview of pictures

Giant. 1 shows a front view of the infiltration module.

Giant. 2 shows a complete infiltrometer, i.e., a vacuum infiltration module connected to an extractor Mariott bottle and connected to a data logger.

Exemplary embodiment

The infiltration module consists of a head 1 of the infiltration module, with a fixed weighing sensor 4, on which a fixed float 5 is screwed, which is terminated at its end by a conical surface 5a. From the supply tube 2 to which the head I of the infiltration module is slid in its upper part, in the same way as the infiltration extension 3 with the sintered plate 3b inserted in its lower part, the sealing of the contact surfaces is ensured in each case by three sealing rings fa, 3a. From the breather tube 7 inserted in the inner part of the infiltration module head 1 into a push-in coupling 7a, to which the venting hose 7b is connected to the outside of the infiltration module head 1b with the hand pump 7c. It further comprises a recording unit 8 which provides measurement data from the weighing sensor 4, which is connected by a signal cable 4a, which is led through the cable gland 4b through the ceiling of the infiltration module head 1, from a vacuum depression tube 6 mounted in the gland 6a. for the aeration tube 6 in the upper part of the infiltration module, which is connected to the Mariott bottle 9 via the angular push-in fitting 9e to the Mariott bottle 9. In the center of the lid 9a of the Mariott bottle 9 there is a sliding tube 9c 9a of the Mariott bottle 9, sealed by a pair of O-rings 9b and 9d.

-4GB 24682 Ul

The infiltration module and its main parts, as well as the Mariott bottle 9, are mainly made of plastics. Specifically, the infiltration module head 1 and infiltration attachment 3 are made of polypropylene 3D printing technology, a 160 ml usable storage tube 2, a stationary float 5 covering the entire usable storage tube 2 volume, and a clear Plexiglas Mariott bottle 9. The storage tube 2 and the Mariott bottle 9 have a wall thickness of 4 mm ensuring sufficient durability of both parts of the proposed apparatus. Other parts of the infiltration module are metal. Specifically, the sintered plate 3b having a diameter of 44.5 mm and a thickness of 3 mm, a venting tube 6 having a diameter of 4 mm, a venting tube 7 having a diameter of 2 mm and a sliding tube 9c having a diameter of 5 mm are made of stainless steel. these parts are in direct contact with water and therefore long term corrosion resistance is required. In addition, the sintered plate 3b is in contact with the soil surface throughout its entire infiltration period and is stressed, in addition to corrosion resistance, to mechanical damage resistance. Cable entry 4b. breather tube 6a and socket 7a as well as angular socket 9e are made of brass or stainless steel in combination with plastic or rubber elements and are particularly stressed for their perfect tightness to guarantee constant conditions throughout the duration infiltration. Perfect tightness must also be ensured in the space between the storage tube 2 and the head 1 of the infiltration module, the storage tube 2 and the infiltration extension 3, as well as between the lid 9a of the Mariott bottle 9 and its wall and lastly between the sliding tube 9c and a lid 9a of the Mariott bottle 9 through which the sliding tube 9c permeates. The tightness of the connection of the infiltration module head 1 and the infiltration attachment 3 to the supply tube 2 is guaranteed by three rubber O-rings 1a, 3a inserted into grooves on the inner circumference (see Figures 1 and 2) of the infiltration module head and infiltration attachment 3. the lid 9a of the Mariott bottle 9 with the Mariott bottle 9 is secured by a pair of O-rings 9b inserted into the grooves on the outer periphery of the lid 9a of the Mariott bottle 9 and the tightness of the sliding tube 9c is guaranteed bottles 9 through which the sliding tube 9c passes. Finally, the vent hose 6b, the vent hose 7b and the signal cable protective sleeve 4a for connecting the recording unit 8 are made of different kinds of plastics.

The disassembled infiltration module is assembled by sliding the head and infiltration module with a built-in weighing sensor 4 with a fixed float 5, and including other components such as a breather tube 7 with push-in fitting 7a, a bore 6a for the ventilation tube 6 and a cable gland 4b of the storage tube 2 and by sliding the infiltration extension 3 with the sinter plate 3b onto the bottom of the storage tube 2 of the infiltration module.

Before starting the measurement, it is necessary to remove the vegetation cover and level the place of infiltration into the plane (check with a spirit level) and smooth out any unevenness with a thin contact layer of fine sand. Thereafter, the infiltration module is connected to the recording unit 8 and connected to the aeration tube 6b with an external Mariott bottle 9, to which a suction pressure (vacuum) value in the range of - 0.5 to - 5.0 cm is preset by sliding support. tubes 9c. The next step is to fill the infiltration module with water by sucking through the sinter plate 3b from the prepared container. Prior to infiltration at the selected site, it is advisable to place the infiltration module on the soil surface at another site and briefly allow infiltration to ensure that the sinter plate 3b is fully saturated with water and does not distort the measurements. After this step, infiltration can be initiated on the pre-treated area by applying an infiltration module to the sand contact layer, if applied. The moment of application of the infiltration module on the soil surface is considered to be the start of infiltration. The level drop, measured over time, in the storage tube 2 causes a change in buoyancy on the stationary float 5 and is transmitted to the weighing sensor 4. For data collection, the infiltration module is connected to a recording unit 8 to which a laptop or other compatible reader can be connected. for checking or evaluating in situ data.

The test measurement of the cumulative infiltration by the designed equipment was carried out in the laboratory on prepared samples and on the experimental area of the Research Institute of Land Amelioration and Soil Protection Prague, specifically on the Kopaninský brook basin. The device can only be used over the entire range of suction pressure heights in very low to medium permeability soils and in well-permeable soils. The measured data are used to describe the infiltration capacity of soils and as input data for numerical modeling. For example, to determine the unsaturated hydraulic conductivity value for a given suction pressure head

Zhang method (Zhang, R. 1997. Determination of soil sorptivity and hydraulic conductivity from the disk infiltrometer. Soil Sci. Soc. Am. J. 61: 1024-1030.) Or a modified form thereof (Dohnal, M., Dušek, J ., Vogel, T., 2010. Improving Hydraulic Conductivity Estimates from Minidisk Infrometer Measurements for Soil with Wide Pore-Size Distributions, Soil Sci. Soc. Am. J. 74, 804-811).

Industrial applicability i The device provides basic information about soil infiltration ability and measured data using this device serves as one of the inputs for numerical modeling usable in the field of hydrological, agricultural, forestry, water management and soil physics research.

Claims (4)

PROTECTION REQUIREMENTS An infiltrometer for measuring the points of hydraulic conductivity in the vicinity of soil saturation, consisting of a Mariott bottle (9), a recording unit (8) and an infiltration module, characterized in that the infiltration module consists of a storage tube (2) on which an infiltration attachment (3) with a sintered plate (3b) is inserted in the lower part and a head (1) of the infiltration module is placed on the upper part of the supply tube (2), in which the weighing sensor (4) is fixed a stationary float (5), parallel to the stationary float (5), 20, but not below its lower edge, there is a vent tube (6) mounted in the vent tube (6a) for the vent tube (6) in the infiltration module head (1), and a cable gland (4b) is further incorporated in the infiltration module head (1). for pulling the signal cable (4a) out of the infiltration module head (1) and a push-in fitting (7a) connecting the vent tube (7) located inside the infiltration module head (1) to the vent hose (7b), 25 which is connected to a hand pump (7c) located outside the infiltration module. Infiltrometer according to claim 1, characterized in that there are sealing O-rings (1a) between the supply tube (2) and the head (1) of the infiltration module and that there are sealing seals between the supply tube (2) and the infiltration extension (3). O-rings (3a), Infiltrometer according to claims 1 and 2, characterized in that the stationary float (5) 30 is terminated by a conical surface (5a) preventing the trapping of bubbles. Infiltrometer according to claims 1 to 3, characterized in that all three parts are separable from each other.