CN101266237B - Circular disc type nonsaturated soil moisture diffusion instrument - Google Patents

Circular disc type nonsaturated soil moisture diffusion instrument Download PDF

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Publication number
CN101266237B
CN101266237B CN2008100180259A CN200810018025A CN101266237B CN 101266237 B CN101266237 B CN 101266237B CN 2008100180259 A CN2008100180259 A CN 2008100180259A CN 200810018025 A CN200810018025 A CN 200810018025A CN 101266237 B CN101266237 B CN 101266237B
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soil
moisture
soil moisture
disk
water
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CN2008100180259A
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CN101266237A (en
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黄明斌
赵爱辉
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Northwest A&F University
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Northwest A&F University
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Abstract

The invention discloses a disk type unsaturated soil moisture diffusing device, comprising moisture supplying device and soil moisture diffusing disk, wherein the moisture supplying device supplies moisture for the soil in the disk and is a lucite tube provided with a water intake on the top of the lucite tube and a water outlet at the inferior end of the side wall of the lucite tube and the water outlet is provided with a rotary valve. The moisture supplying device provides water supply with constant head based on Mariotte bottle principle and is connected with the soil moisture diffusing disk by a rubber hose. The soil moisture diffusing disk comprises three concentric circles and is divided into water chamber, filtering layer and sample laying area from the inside to the outside, wherein the circular side wall between each parts is overspreaded with cribriform pores to make the moisture freely pass through, The disk type unsaturated soil moisture diffusing device can measure a plurality of samples at the same time and the measurement result has consistency with the traditional method (horizontal earth column diffusion method).

Description

A kind of circular disc type nonsaturated soil moisture diffusion instrument
Technical field
The invention belongs to pedology, soil mechanics and soil and water conservation research field, relate to the assay method and the device of soil unsaturation moisture diffusivity, the particularly a kind of circular disc type nonsaturated soil moisture diffusion instrument that can measure a plurality of soil simultaneously.
Background technology
40% of world land area all is in the arid and semi-arid area, and shortage of water resources is restricting these regional industrial and agricultural developments, and causes many ecological problems.Soil moisture not only provides the plant required moisture of growing, also taking on the carrier that transports various nutrients, it plays key effect for structure, the succession of vegetation ecological system, and therefore disclosing the soil water movement feature and rationally regulating and control soil water regime is the basis of agricultural production, improvement of the ecological environment.
Soil water movement has two kinds of saturated motion and unsaturation campaigns, and all obeys Darcy's law, but unsaturated soil moisture has own unique migration rule, and has more Research Significance for the arid and semi-arid area.So Chinese scholars has been carried out a large amount of research with regard to the unsaturated soil moisture movement, and progressively develop into and utilize mathematical model to come simulation and forecast by simple experimental study.And the accuracy of mathematical simulation directly depends on the reliability and the degree of accuracy of related hydraulic parameters.The related hydraulic parameters of unsaturated soil moisture movement mainly is characteristic curve of soil moisture, unsaturated hydraulic conductivity and diffusivity.The acquisition of the diffusivity of soil unsaturation in recent years parameter is subjected to extensive concern, and the level method of infiltrating wherein commonly used is that bruce and klute (1956) calculate with the change profile tabulation of earth pillar by measuring soil moisture content on Boltzmann conversion basis.Nineteen sixty-eight Cassel etc. proposed a kind of according to moisture in the certain hour again in the distributed process distribution situation of soil moisture content ask the rate of water diffusion of soil, this method need be measured soil moisture content distribution in time, requires the data computation and the experimental period of powerful amount simultaneously.Clothier etc. (1983) utilize the Philip analytical method to propose one and describe the fitting function that soil moisture distributes, and do not need like this to obtain the rate of water diffusion that the moisture distribution rate of curve just can calculate soil, make methods simplification.Yet fitting functions such as Clothier are not that every kind of soil all is suitable for.Shao and Horton (1996) utilize the theoretical Boltzmann of replacement of Generalized Similarity conversion to estimate that the level of moisture goes into to blend distributed process again, and then inquire into and soil unsaturation diffusivity.Shortcomings such as that above method all exists in practical operation and computation process is time-consuming, effort, reckoning process complexity.
Summary of the invention
Defective or deficiency at above-mentioned prior art existence, the objective of the invention is to, provide a kind of circular disc type nonsaturated soil moisture diffusivity analyzer that can measure a plurality of pedotheques simultaneously according to soil water movement fundamental equation in the cylindrical coordinate, this analyzer can be measured the unsaturation diffusivity of 6 pedotheques simultaneously, can either improve test efficiency and simplify a large amount of mathematical computations processes again.
In order to realize above-mentioned task, the present invention takes following technical solution:
A kind of circular disc type nonsaturated soil moisture diffusion instrument is characterized in that, this instrument is made up of moisture feeder and soil moisture diffusion disk, wherein:
The moisture feeder is used for providing moisture to the disk soil sample, and this moisture feeder is a plexi-glass tubular, water inlet and water delivering orifice are arranged on the plexi-glass tubular, water inlet is positioned at the plexi-glass tubular top, and water delivering orifice is positioned at the side wall lower ends of plexi-glass tubular, and the water delivering orifice place is furnished with changeover valve;
Soil moisture diffusion disk, be used to place tested pedotheque, this soil moisture diffusion disk is made up of 3 donuts, the donut at center links to each other with the moisture feeder, for the test soil sample provides the water source with constant head, outer field two donuts of the donut at center are divided into six districts, and wherein Zhong Jian donut is used to install filter medium, and outermost donut is placed the test soil sample.
Circular disc type nonsaturated soil moisture diffusion instrument of the present invention possesses following function:
1) measure the diffusivity of a plurality of pedotheques simultaneously, more traditional horizontal soil column diffusion instrument is increased work efficiency 6 times;
2) pedotheque can be provided with repetition, improves and measures precision;
3) the water inlet end area is little, and the unit interval inflow is few, is convenient to soil fully diffusion under operate under unsaturated conditions.
Description of drawings
Fig. 1 is a device cross-sectional view of the present invention;
Fig. 2 is a soil moisture diffusion disk schematic perspective view;
Three kinds of soil sample soil moisture contents distribution plan diametrically when Fig. 3 is the experiment end;
Fig. 4 is the graph of a relation of three kinds of soil sample θ and λ;
The present invention is described in further detail below in conjunction with the principle of work of accompanying drawing and device and process.
Embodiment
Referring to Fig. 1, circular disc type nonsaturated soil moisture diffusion instrument of the present invention is made up of moisture feeder and soil moisture diffusion disk two parts, wherein:
The moisture feeder, adopt plexi-glass tubular, utilize Ma Shi bottle principle to be used for providing water source with constant head to the soil disk, be used for providing moisture to the disk soil sample, this feeder is for adorning the plexi-glass tubular 1 of water, and a water inlet is arranged at the top of plexi-glass tubular 1, the side wall lower ends of plexi-glass tubular 1 has a water delivering orifice, the water delivering orifice place is furnished with changeover valve, is used for controlling water flowing and cuts off the water, and uses Ma Shi bottle principle and keeps constant head;
The height of soil diffusion disk 2 is 12cm, is made up of 3 concentric circless, and three concentrically ringed radiuses are respectively 5cm, 10cm, 60cm.The circle centre position of centres annulus 3 bottom center has a water inlet to be connected by the water delivering orifice of rubber tube with the moisture feeder, for soil moisture diffusion disk provides the water source with constant head; Two donuts beyond the centres circle are divided into six districts, and the outer ring donut is used for dress test soil sample; Middle donut is used to adorn filter mediums such as sand, play the effect of filtering layer, distributing permeable on the wall 4 of middle donut and middle donut and the sieve shape aperture of saturating sand grains not, the moisture of constant head is flowed through test soil sample that filtering layer enters the outer ring donut.Outer wall and six subregion dividing plates of soil moisture diffusion disk are marked with scale, are convenient to calculate the observation of soil loading amount and the moistening peak shift of experimental session and determining of sample position.
During experiment, the water inlet sealing with moisture feeder 1 only is communicated with atmosphere by middle tubule, and outlet valve is opened and supplied water, and connects with rubber tube between water delivering orifice and the soil moisture diffusion disk bottom water inlet.
The test soil sample that soil diffusion disk outer ring annulus is placed requires that unit weight is certain, density homogeneous, thickness≤10cm, when repetition is set, loads with the soil diagonal angle of quality; The effect of (being tapered) filter medium filtering layers such as middle annulus dress sand from the water source to test soil sample particle.Outer wall and six subregion dividing plates of soil diffusion disk are marked with scale, are convenient to evenly observation of dress soil, moistening peak shift and determining of sample position.
The principle of circular disc type nonsaturated soil moisture diffusion instrument is:
In cylindrical coordinate, the fundamental equation of unsaturated soil moisture movement is:
∂ θ ∂ t = 1 r ∂ ∂ r [ rD ( θ ∂ θ ∂ r ) ] - - - ( 1 )
Deciding under the head condition, the initial and boundary condition of moisture movement is in the cylindrical coordinate:
θ = θ i r > 0 t = 0 ( 2 a ) θ = θ s r = 0 t > 0 ( 2 b )
In the formula, θ iBe initial soil moisture content, θ sIt is saturated soil water content.
Equation (1) is rewritten into that (θ t) for the fundamental equation of dependent variable is with radius coordinate r
- ∂ r ∂ t = 1 r ∂ ∂ θ [ rD ( θ ) / ∂ r ∂ θ ]
By Boltzmann conversion r (θ, t)=λ (θ) t 1/2, arrangement obtains finding the solution the ordinary differential equation of soil water movement:
λ ( θ ) = - 2 1 r d dθ [ rD ( θ ) dθ dλ ( θ ) ] - - - ( 3 )
Under boundary condition (2a), (2b) condition, to formula (3) from θ iGet to the θ integration
D ( θ ) = - 1 2 λ dλ dθ ∫ θ i θ λ 2 dθ
The form that is rewritten into difference is
D ( θ ) = - 1 2 λ Δλ Δθ Σ θ i θ λ 2 Δθ - - - ( 4 )
During off-test, measure the distribution of soil moisture content, calculate the λ value of different θ correspondences, on coordinate axis, draw the relation curve of θ and λ, just can obtain the soil water diffusivity under the different moisture content by tabulating with soil diffusion disc radius.
Process of the test is: at first circular disc type nonsaturated soil moisture diffusion instrument is connected, soil diffusion disc level puts surely; fill out filter medium (filter medium of sand grains or other this area routine); the air-dry soil sample that to cross the 2mm sieve subsequently is by the isopycnic soil sample disk of packing into of certain unit weight; the soil layer filling thickness is 10cm, loads etc. quality soil sample diagonal angle.After dress water finishes in the moisture feeder, the water inlet sealing.Regulate delivery head, open the water delivering orifice changeover valve and supply water, begin timing when moistening in soil sample.Experiment finishes the back and begins to fetch earth rapidly from wetting front, measures the water percentage distribution situation in each district, uses λ = rt - 1 2 (Boltzmann conversion) calculates the corresponding λ value of different θ (water cut), and it is plotted on the coordinate paper, and curve is carried out smooth treatment, uses the cylindrical coordinates difference equation of diffusivity then ( D ( θ ) = - 1 2 λ Δλ Δθ Σ θ a θ λ 2 Δθ ) , Calculate soil moisture diffusivity under the different moisture content condition by tabulation.
Verification experimental verification:
Use this present invention's circular disc type nonsaturated soil moisture diffusion instrument that the unsaturation diffusivity of three kinds of differing texture pedotheques is measured.For the accuracy of assay, measurement result and classical horizontal soil column are infiltrated the measurement result of method compare.Table 1 is that the particle of three kinds of quality soil samples is formed and basic physical property, Fig. 3 is three kinds of soil sample soil moisture content distributions diametrically measuring, Fig. 4 is three kinds of soil sample θ measuring and the relation curve of λ, three kinds of soil sample unsaturated soil rate of water diffusion data that table 2 records respectively for horizontal soil column method and disk diffusion method.And measurement result carried out significance analysis, between the t value data that two kinds of methods record as can be seen, there is not significant difference, proves that circular disc type nonsaturated soil moisture diffusion instrument of the present invention can replace the mensuration that classic method is used for the soil unsaturated hydraulic conductivity.
The basic physical property of three kinds of differing texture soil of table 1
Table 2a. disk diffusion instrument and traditional horizontal diffusion instrument are measured the comparison of soil unsaturation diffusivity
(heavy loam, Shaanxi Yang Ling)
Table 2b. disk diffusion instrument and traditional horizontal diffusion instrument are measured the comparison of soil unsaturation diffusivity
(light loam, Ansai, Shaanxi)
0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.210389 0.260463 0.357111 0.663318 1.766959 5.010821 8.491164 8.541864 0.147607 0.359091 0.802461 1.80372 3.396152 9.362585 15.00437 18.08721 ? ?
Table 2c. disk diffusion instrument and traditional horizontal diffusion instrument are measured the comparison of soil unsaturation diffusivity
(sandy soil, Shenmu County, Shaanxi)
The more traditional horizontal soil column of circular disc type nonsaturated soil moisture diffusion instrument of the present invention is surveyed the method for diffusivity and is compared, and has following advantage:
(1) can measure 6 pedotheques in the same time, minute greatly saves time;
(2) pedotheque can be provided with 2-3 repetition, can improve the mensuration precision greatly;
(3) the water inlet end area is little, and the unit interval inflow is few, is convenient to soil fully diffusion under operate under unsaturated conditions.

Claims (4)

1. a circular disc type nonsaturated soil moisture diffusion instrument is characterized in that, this instrument is made up of moisture feeder and soil moisture diffusion disk, wherein:
The moisture feeder is used for providing moisture to the disk soil sample, and this moisture feeder is a plexi-glass tubular, water inlet and water delivering orifice are arranged on the plexi-glass tubular, water inlet is positioned at the plexi-glass tubular top, and water delivering orifice is positioned at the side wall lower ends of plexi-glass tubular, and the water delivering orifice place is furnished with changeover valve;
Soil moisture diffusion disk, be used to place tested pedotheque, this soil moisture diffusion disk is made up of 3 donuts, the donut at center links to each other with the moisture feeder, for the test soil sample provides the water source with constant head, outer field two donuts of the donut at center are divided into six districts, and wherein Zhong Jian donut is used to install filter medium, and outermost donut is placed the test soil sample.
2. circular disc type nonsaturated soil moisture diffusion instrument as claimed in claim 1 is characterized in that, described filter medium is a sand.
3. circular disc type nonsaturated soil moisture diffusion instrument as claimed in claim 1 is characterized in that, is distributing permeable on the wall of described centres annulus and middle donut and the sieve shape aperture of saturating sand grains not.
4. circular disc type nonsaturated soil moisture diffusion instrument as claimed in claim 1 is characterized in that, outer wall and six subregion dividing plates of described soil moisture diffusion disk are marked with scale.
CN2008100180259A 2008-04-23 2008-04-23 Circular disc type nonsaturated soil moisture diffusion instrument Expired - Fee Related CN101266237B (en)

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Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101865811B (en) * 2009-03-25 2011-08-03 中国科学院地质与地球物理研究所 Method for measuring three-dimensional stress loaded soil permeability parameter
CN101865810B (en) * 2009-03-25 2011-06-15 中国科学院地质与地球物理研究所 Test method for determining unsaturated soil water characteristic parameters
CN102507888A (en) * 2011-11-07 2012-06-20 中国科学院地理科学与资源研究所 Unsaturated water supply device for simulating underground water
CN104359801A (en) * 2014-11-20 2015-02-18 中国地质大学(武汉) Multi-stage aeration zone soil moisture diffusion tester based on one-dimensional horizontal flow
CN105277470B (en) * 2015-11-17 2018-01-30 赵海超 For simulating the experimental provision of soil moisture migration process
CN106525661B (en) * 2016-10-28 2018-08-24 中南大学 Unsaturated soil vapour complex characteristic test device and its test method

Citations (4)

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Publication number Priority date Publication date Assignee Title
US6076395A (en) * 1998-02-05 2000-06-20 The United States Army Corps Of Engineers As Represented By The Secretary Of The Army Constant stress diffusion cell with controllable moisture content
CN1341850A (en) * 2001-01-04 2002-03-27 中国科学院南京土壤研究所 Large-range soil water suction force measurement technique and production process of its suction force plate
CN2491835Y (en) * 2001-07-23 2002-05-15 涂六艳 Soil moisture monitoring/controlling instrument
CN1536362A (en) * 2003-04-11 2004-10-13 中国科学院地理科学与资源研究所 Crop moisture stress index determination device and its determination method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6076395A (en) * 1998-02-05 2000-06-20 The United States Army Corps Of Engineers As Represented By The Secretary Of The Army Constant stress diffusion cell with controllable moisture content
CN1341850A (en) * 2001-01-04 2002-03-27 中国科学院南京土壤研究所 Large-range soil water suction force measurement technique and production process of its suction force plate
CN2491835Y (en) * 2001-07-23 2002-05-15 涂六艳 Soil moisture monitoring/controlling instrument
CN1536362A (en) * 2003-04-11 2004-10-13 中国科学院地理科学与资源研究所 Crop moisture stress index determination device and its determination method

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