CN112051203A - Soil porosity measuring device and soil porosity measuring method - Google Patents
Soil porosity measuring device and soil porosity measuring method Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 107
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000001514 detection method Methods 0.000 claims abstract description 38
- 238000005259 measurement Methods 0.000 claims abstract description 34
- 239000007789 gas Substances 0.000 claims description 44
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 20
- 239000001301 oxygen Substances 0.000 claims description 20
- 229910052760 oxygen Inorganic materials 0.000 claims description 20
- 239000007787 solid Substances 0.000 claims description 12
- 238000007789 sealing Methods 0.000 claims description 10
- 238000000691 measurement method Methods 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims 1
- 238000012360 testing method Methods 0.000 abstract description 7
- 238000005520 cutting process Methods 0.000 description 41
- 239000011148 porous material Substances 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 239000011435 rock Substances 0.000 description 5
- 230000035945 sensitivity Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000011549 displacement method Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000010802 sludge Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
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Abstract
The embodiment of the invention provides a soil porosity measuring device and a soil porosity measuring method, and relates to the technical field of porosity measurement. The soil porosity measuring device comprises a detection bin, a vacuum pump and a gas concentration detector. The detection bin comprises a sample bin and a vacuum bin; and a control valve is arranged between the sample bin and the vacuum bin and is used for communicating or separating the sample bin and the vacuum bin. The sample storehouse is used for placing the sample, and the vacuum pump is connected with the vacuum storehouse, and gas concentration detector sets up in the vacuum storehouse, has seted up the bleed valve on the vacuum storehouse. The porosity measuring device obtains the porosity of a sample by measuring the change of the gas concentration, and the measuring method is simple and convenient to operate, suitable for outdoor measurement, high in testing efficiency and capable of being repeatedly used.
Description
Technical Field
The invention relates to the technical field of soil porosity measurement, in particular to a soil porosity measurement device and a soil porosity measurement method.
Background
At present, the traditional methods for measuring the porosity of soil mainly comprise a gas expansion displacement method, a water-holding volume method, a computer graphics method and the like.
The gas expansion displacement method comprises the steps of firstly recording the diameters and the lengths of the steel discs and the rock sample, then adjusting the atmospheric pressure of a rock chamber, putting the sample into the rock chamber, rotating the T-shaped rotating handle, adjusting the pressure to 560kPa, recording the pressure P1 of a standard chamber, then expanding gas to the rock chamber, recording the equilibrium pressure P2, and finally calculating the volume of each steel disc and the external volume of the rock mass according to a formula. The measuring method has the advantages of low precision, pressurization, high safety requirement in the operation process and limited use place.
The method for accommodating the water volume is that firstly, a soil sample is collected on a flat section by using a cutting ring, the soil sample is quickly weighed (natural soil weight and cutting ring weight), then the cutting ring sample is taken back to a laboratory and is placed in a water container, the paper is wetted after about 2 hours, the cutting ring is taken out and is immediately weighed, finally the cutting ring is placed back to the original position, the cutting ring is taken out and repeatedly weighed every 1 hour until the weight is constant, and the porosity of a soil capillary is obtained by calculation according to a formula; and (3) continuously placing the circular cutter back to the water container, standing for 6 hours, then controlling the excess water flow to weigh, finally placing the circular cutter back to the original position, standing for 4-5 hours, taking out the circular cutter, repeatedly weighing until the weight is constant, and calculating according to a formula to obtain the total porosity of the soil. The method has the advantages that pollution instruments such as sludge and muddy water are easily formed in the measuring process, meanwhile, the measuring period is long, the precision is poor, the repeated measurement is inconvenient, and the measuring work cannot be carried out in the field.
The computer graphics method comprises the steps of firstly converting an image into a gray image, then selecting a threshold value to convert the image into a binary image, wherein the area above the threshold value is a pore, and finally calculating the ratio of the pore area in the binary image to the total area to obtain the porosity. The biggest limitation of this method is that there is no accepted standard for selecting the threshold, different threshold selections will yield different porosity results, it is highly dependent on the experience of the researcher, and it is not suitable for outdoor measurement.
Disclosure of Invention
The object of the present invention includes, for example, providing a soil porosity measuring apparatus and method which can rapidly measure the porosity of soil, is simple in measuring manner, does not depend on a professional, can repeatedly perform the measurement, and is suitable for outdoor measurement work.
Embodiments of the invention may be implemented as follows:
in a first aspect, an embodiment of the present invention provides a soil porosity measurement apparatus, including a detection bin, a vacuum pump, and a gas concentration detector;
the detection bin comprises a sample bin and a vacuum bin; a control valve is arranged between the sample bin and the vacuum bin and is used for communicating or isolating the sample bin and the vacuum bin;
the sample bin is used for placing samples, the vacuum pump is connected with the vacuum bin, the gas concentration detector is arranged in the vacuum bin, and the vacuum bin is provided with a deflation valve.
In an alternative embodiment, the gas concentration detector is an oxygen concentration detector.
In an alternative embodiment, the vacuum chamber is fitted with a pressure detector for detecting the pressure of the vacuum chamber.
In an alternative embodiment, the volume of the vacuum chamber and the volume of the sample chamber are equal.
In an alternative embodiment, the vacuum chamber and the sample chamber are cylinders with equal diameters, and the vacuum chamber and the sample chamber are integrally formed.
In an optional embodiment, the vacuum pump is communicated with the vacuum chamber through a conduit, and a stop valve is arranged on the conduit.
In an alternative embodiment, a rack is arranged in the sample bin and used for placing samples.
In a second aspect, an embodiment of the present invention provides a soil porosity measuring method, which uses the soil porosity measuring apparatus according to the foregoing embodiment, including:
putting the solid standard product into a sample bin;
sealing the detection bin and isolating the vacuum bin from the sample bin;
starting the vacuum pump, and maintaining the pressure of the vacuum bin to be a preset pressure;
closing a stop valve between the vacuum pump and the vacuum chamber, and opening the control valve to communicate the vacuum chamber with the sample chamber; the gas concentration detector records a first concentration of gas O1;
placing a soil sample into the sample bin; sealing the detection bin, separating the vacuum bin from the sample bin, starting the vacuum pump, and maintaining the pressure of the vacuum bin to be the preset pressure;
closing a stop valve between the vacuum pump and the vacuum chamber, and opening the control valve to communicate the vacuum chamber with the sample chamber; the gas concentration detector records a second concentration O2 of the gas;
and calculating the soil porosity A according to the first concentration and the second concentration.
In an alternative embodiment, the step of calculating the soil porosity a from the first concentration and the second concentration comprises:
a ═ O2-O1 × (V true + V-like)/0.217/V ring cutter × 100;
wherein, a is soil porosity in Vol.%; vure represents the vacuum bin volume, in L; v sample is the volume of the sample bin and is in unit L; the V-ring cutter is the volume of the ring cutter, and the unit is L.
In an alternative embodiment, before the step of placing the sample into the sample chamber, the method further comprises:
checking the tightness of the detection bin;
and (5) checking the tightness of the vacuum bin.
The beneficial effects of the embodiment of the invention include, for example:
according to the soil porosity measuring device provided by the embodiment of the invention, the vacuum bin and the sample bin which can be selectively communicated or separated are arranged, the vacuum bin is connected with the vacuum pump, the gas concentration detector is arranged in the vacuum bin, the porosity of the soil is calculated by measuring the change of the gas concentration, the operation is convenient, no professional is required, the measuring result is reliable, the carrying is convenient, the measuring work can be carried out outdoors, the measurement can be repeated, the measuring efficiency is greatly improved, the measuring cost is reduced, and the soil porosity measuring device has great popularization and application values.
According to the soil porosity measuring method provided by the embodiment of the invention, a solid standard sample is placed in a sample bin, so that a detection bin is in a closed state, a vacuum bin is firstly separated from the sample bin, a vacuum pump is started, the pressure of the vacuum bin is maintained to be a preset pressure, then a control valve is started to enable the vacuum bin to be communicated with the sample bin, and a gas concentration detector records a first concentration of gas; and then placing the soil sample in a sample bin, repeating the steps, measuring the second concentration of the gas by the gas concentration detector, and calculating the porosity of the soil by calculating the change of the gas concentration. The measuring method is simple, convenient to operate, capable of repeatedly measuring for multiple times, and convenient for outdoor field measurement, greatly improves the measuring efficiency and reduces the measuring cost.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic structural diagram of a soil measuring device according to an embodiment of the present invention;
fig. 2 is a block diagram illustrating steps of a soil measurement method according to an embodiment of the present invention.
Icon: 100-a soil porosity measuring device; 110-a detection bin; 111-vacuum chamber; 113-sample compartment; 120-a gas concentration detector; 130-a vacuum pump; 131-a conduit; 133-a shut-off valve; 135-air release valve; 140-a pressure detector; 150-a control valve; 160-shelf; 170-door of bin.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. indicate an orientation or a positional relationship based on that shown in the drawings or that the product of the present invention is used as it is, this is only for convenience of description and simplification of the description, and it does not indicate or imply that the device or the element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention.
Furthermore, the appearances of the terms "first," "second," and the like, if any, are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
It should be noted that the features of the embodiments of the present invention may be combined with each other without conflict.
Soil porosity is the percentage of soil pore volume to soil volume. Coarse and fine soil grains in various shapes in soil are gathered and arranged into a solid phase skeleton. The skeleton has pores with different widths and shapes to constitute complicated pore system, and the percentage of the total pore volume to the soil volume is called soil porosity, also called soil porosity.
Water and air coexist and fill the soil pore system. Soil porosity is a place for water movement and storage, and is a key element influencing soil permeability and determining surface runoff and runoff time. Soil porosity is generally divided into 3 grades: macropores, mesopores and microvoids. The porosity reflects the soil porosity condition and degree of tightness: the porosity of the coarse sand is about 33-35% and the large pore space is large. The porosity of the clay is about 45-60%, and the clay has a plurality of small pores. The porosity of loam is about 55-65%, and the proportion of large and small pores is basically equivalent. The porosity of soil is described in terms of the porosity of the soil, which is the ratio of the pore volume in the soil to the total volume of the soil.
The existing soil porosity measuring methods mainly include a gas expansion displacement method, a water-holding volume method, a computer graphic calculation method and the like. The gas expansion displacement method has the advantages of low precision, pressurization, high safety requirement in the operation process, limited use place and inconvenience in carrying; the device can accommodate polluted instruments such as sludge, muddy water and the like easily formed in the measurement process of the moisture volume method, and meanwhile, the measurement period is long, the precision is poor, the repeatability is not easy, and the outdoor measurement work cannot be carried out; the method for calculating the porosity of the soil through computer graphics has the biggest limitation that the selection of the threshold has no recognized standard, different threshold selections can obtain different porosity results, and the experience dependence on researchers is strong.
In order to overcome the defects of the prior art, the embodiment of the invention provides the soil porosity measuring device 100, the porosity of the soil is calculated by measuring the change of the gas concentration, the operation is convenient, no professional is required, the measuring result is reliable, the carrying is convenient, the measuring device can be used for measuring outdoors and can be used for repeated measurement, the measuring efficiency is greatly improved, and the measuring cost is reduced.
First embodiment
Referring to fig. 1, the present embodiment provides a soil porosity measuring apparatus 100, which includes a detection chamber 110, a vacuum pump 130, and a gas concentration detector 120. Wherein, the detection chamber 110 comprises a sample chamber 113 and a vacuum chamber 111. A control valve 150 is arranged between the sample bin 113 and the vacuum bin 111, and the control valve 150 is used for communicating or isolating the sample bin 113 and the vacuum bin 111. The sample bin 113 is used for placing samples, the vacuum pump 130 is connected with the vacuum bin 111, the gas concentration detector 120 is arranged in the vacuum bin 111, and the vacuum bin 111 is provided with a gas release valve 135. The gas concentration detector 120 detects a first concentration of the gas in the sample chamber 113 filled with the solid standard and a second concentration of the gas in the sample chamber 113 filled with the soil sample, respectively, so as to calculate the porosity of the sample according to the concentration change of the gas. The soil porosity measuring device 100 is simple and compact in structure, small in size, convenient to carry, capable of conveniently performing measurement work outdoors, reusable and high in flexibility.
Optionally, in this embodiment, the gas concentration detector 120 is an oxygen concentration detector, and is used to detect the oxygen concentration of the detection chamber 110 under different working conditions. In the measuring process, a solid standard sample can be placed in the sample cabin 113, the first concentration of oxygen in the detection cabin 110 is detected under a preset condition, then a soil sample is placed in the sample cabin, the second concentration of oxygen in the whole detection cabin 110 is detected under the same preset condition, and the porosity of the sample is calculated through the change of the first concentration and the second concentration of oxygen. In this embodiment, the oxygen concentration detector requires a resolution of 0.1ppm and 0.1% LEL to improve the accuracy of the measurement result. Of course, the gas concentration detector 120 may also be a nitrogen concentration detector for detecting the change in the concentration of nitrogen to calculate the porosity of the sample; alternatively, the porosity of the sample may be calculated by measuring the change in the concentration of other gases, and is not particularly limited herein.
It can be understood that the vacuum chamber 111 and the sample chamber 113 are cylinders with equal diameters, respectively, the vacuum chamber 111 and the sample chamber 113 are integrally formed, that is, the detection chamber 110 is a whole, and the control valve 150 is disposed in the detection chamber 110, so that the whole detection chamber 110 is divided into two parts, namely the sample chamber 113 and the vacuum chamber 111. Further, the control valve 150 is disposed in the middle of the detection chamber 110, so that the volume of the vacuum chamber 111 is equal to the volume of the sample chamber 113, which can reduce the system measurement error, facilitate calculation, and facilitate to improve the accuracy and reliability of the measurement result and improve the measurement efficiency.
Alternatively, the vacuum chamber 111 and the sample chamber 113 are respectively cylindrical and have a volume of 100cm3To 300cm3The wall body of the detection chamber 110 can be made of hard materials such as but not limited to organic glass or metal, wherein if the detection chamber 110 is made of organic glass, the wall thickness requirement is greater than or equal to 1cm so as to meet the strength requirement; if the detection bin 110 is made of stainless steel, the wall thickness is required to be greater than or equal to 2mm so as to meet the strength requirement. Of course, the detection chamber 110 can have other shapes, and is not limited in this respect.
Further, a pressure detector 140 is installed in the vacuum chamber 111 for detecting the pressure of the vacuum chamber 111. The pressure detector 140 includes, but is not limited to, a vacuum gauge that can be used to record the sealing performance of the test chamber 110 and can be used to adjust the pressure balance within the test chamber 110. The vacuum pump 130 is communicated with the vacuum chamber 111 through a conduit 131, the conduit 131 is provided with a stop valve 133, and the stop valve 133 is arranged to facilitate control of the pressure in the vacuum chamber 111. The vacuum chamber 111 is further provided with a vent valve 135, optionally, the vent valve 135 is provided at an end of the vacuum chamber 111 far from the sample chamber 113, however, the vent valve 135 may be provided at any other position in the vacuum chamber 111, and is not limited herein. The air release valve 135 may be used to equalize the air pressure inside and outside the vacuum chamber 111. After the air release valve 135 is closed, a closed space can be created in the vacuum chamber 111, and the vacuum pump 130 is opened to adjust the pressure in the vacuum chamber 111; when the air release valve 135 is opened, the vacuum chamber 111 is communicated with the outside, and the air in the vacuum chamber 111 is released, so that the internal and external air pressures of the vacuum chamber 111 are balanced, and the sensitivity of the pressure detector 140 and the sensitivity of the gas concentration detector 120 are prevented from being damaged due to the fact that the vacuum chamber 111 is in a vacuum state for a long time.
Optionally, a rack 160 is disposed in the sample chamber 113, and the rack 160 is used for placing samples. The sample chamber 113 is further provided with a chamber door 170 which can be opened or closed, the sample can be placed on the shelf 160 by opening the chamber door 170, and a closed space of the sample chamber 113 can be created by closing the chamber door 170. For example, when the door 170 and the control valve 150 are closed at the same time, the sample chamber 113 is in a sealed state.
The soil porosity measuring device 100 provided by the embodiment of the invention has the advantages of simple and compact structure, small volume, convenience in carrying and flexibility in operation, can repeatedly measure the porosity of a sample, is suitable for measuring outdoors, does not need professional operation in the using process, has higher flexibility and accurate and reliable test result, greatly improves the measuring efficiency and reduces the measuring cost. The measuring device can be used for measuring the porosity of soil and measuring the porosity of other objects, has similar measuring principle and method, and has wide application range.
Second embodiment
Referring to fig. 2, an embodiment of the present invention provides a soil porosity measuring method, which is used for the soil porosity measuring apparatus 100, and mainly includes the following steps:
s10: collecting a sample;
s20: checking the sealing performance;
s30: placing the solid standard into the sample chamber 113, and measuring a first concentration of the gas in the detection chamber 110 under a preset condition;
s40: placing the soil sample into the sample bin 113, and measuring a second concentration of the gas in the detection bin 110 under a preset condition;
s50: and calculating the porosity of the soil according to the first concentration and the second concentration.
Specifically, the soil sample collection will be described as an example.
The step of collecting the sample comprises:
(1) and (4) selecting a standard land, planing the soil surface by using a shovel at a measuring place, making a platform, and digging a soil section.
(2) The cutting ring support is sleeved at the end, without the cutting edge, of the cutting ring, the cutting ring support handle is pressed firmly and balanced, the cutting ring is driven into the soil vertically and cannot shake, if the soil is hard, the cutting ring cannot be easily inserted into the soil, the cutting ring support handle can be slightly knocked by a soil hammer, and when the whole cutting ring is completely pressed into the soil and the soil surface is about to touch the top of the cutting ring support, the cutting ring can be peeped through a small hole in the cutting ring support cover, and the pressing is stopped.
(3) Digging soil around the cutting ring by using a shovel, cutting off the soil below the cutting ring, and leaving some redundant soil below the cutting ring; taking out the cutting ring, turning over the cutting ring with the cutting edge facing upwards, scraping off the soil adhered to the outer wall of the cutting ring with a soil cutting knife, and cutting the soil from the edge to the middle part with the soil cutting knife to make the soil level with the cutting edge. And when the soil is leveled to the lower edge of the cutting ring, a layer of filter paper is padded on the cutting ring, and the lower cover is covered.
(4) And covering the top cover of the cutting ring, turning the cutting ring again to enable one end of the cutting edge covered with the top cover to face downwards, taking down the cutting ring support, flattening the soil surface without the cutting edge end, and covering the bottom cover.
Before measurement, the tightness of the test chamber 110 and the tightness of the vacuum chamber 111 need to be checked.
Optionally, the step of verifying the tightness of the vacuum chamber 111 comprises: the control valve 150 and the air release valve 135 are closed, the vacuum chamber 111 is isolated from the sample chamber 113, and the vacuum chamber 111 is in a sealed state. The stop valve 133 and the vacuum pump 130 are opened, the vacuum pump 130 vacuumizes the vacuum chamber 111, the reading of the vacuum pressure gauge is checked, and when the reading of the vacuum pressure gauge is P1, the vacuum pump 130 and the stop valve 133 are closed.
After standing for half an hour, the reading of the vacuum pressure gauge is checked again to determine whether the vacuum chamber 111 has changed. If the reading is unchanged, the sealing performance of the vacuum chamber 111 is good, and after the reading is checked, the air release valve 135 is opened to level the atmospheric pressure inside and outside the vacuum chamber 111 so as to prevent the sensitivity of the pressure detector 140 and the gas concentration detector 120 from being damaged due to long-term vacuum state. If the reading changes, the tightness of the vacuum chamber 111 is not good, and the vacuum chamber needs to be replaced or maintained until the sealing performance meets the requirement, and then the measurement is carried out.
The step of verifying the hermeticity of the entire test chamber 110 includes: the chamber door 170 which opens the control valve 150 and closes the sample chamber 113 by the air release valve 135 is closed, the vacuum chamber 111 is communicated with the sample chamber 113, and the whole detection chamber 110 formed by the vacuum chamber 111 and the sample chamber 113 is in a closed state. The stop valve 133 and the vacuum pump 130 are opened, the vacuum pump 130 vacuumizes the detection bin 110, the reading of the vacuum pressure gauge is checked, and when the reading of the vacuum pressure gauge is P2, the vacuum pump 130 and the stop valve 133 are closed. After standing for half an hour, the vacuum gauge reading is checked again for changes to verify the sealing performance of the test chamber 110 (i.e., the sample chamber 113 and the vacuum chamber 111). If the reading is unchanged, the tightness of the detection bin 110 is good, and after the detection, the air release valve 135 is opened to level the atmospheric pressure inside and outside the detection bin 110, so as to prevent the sensitivity of the pressure detector 140 and the gas concentration detector 120 from being damaged due to long-term vacuum state. If the reading changes, the tightness of the detection bin 110 is not good, and the detection bin needs to be replaced or maintained until the sealing performance meets the requirement, and then the measurement is carried out.
During measurement, the door 170 is opened and the solid standard is placed on the rack 160 in the sample chamber 113. The solid standard product refers to a cutting ring and a solid body filled in the cutting ring, the solid body can be stainless steel, and the like, and no gap exists in the whole solid standard product. Closing the bin gate 170, closing the control valve 150 and the air release valve 135 to separate the sample bin 113 from the vacuum bin 111, and respectively keeping the sample bin and the vacuum bin in a closed state; starting the vacuum pump 130 and the stop valve 133, vacuumizing the vacuum bin 111 by the vacuum pump 130, and stabilizing the reading of the vacuum pressure gauge at a preset pressure P3, wherein the numerical value cannot be changed; it should be noted that, after the vacuum pump 130 is turned on for a certain period of time, the vacuum-pumping limit state is reached, and then even if the vacuum pump 130 is not stopped, the pressure in the vacuum chamber 111 will not change, and will be kept stable at the preset pressure P3. After the reading of the oxygen concentration detector has stabilized, the stop valve 133 is closed, the vacuum pump 130 can be closed, the control valve 150 is opened to communicate the sample chamber 113 with the vacuum chamber 111, and after the reading of the oxygen concentration detector has stabilized, the first concentration O1 of oxygen is recorded.
The solid standard is taken out, the air release valve 135 is opened, the pressure inside and outside the detection chamber 110 is balanced, and the next measurement is carried out. The bin door 170 is opened and soil samples, which include the cutting ring and soil together, are placed on the rack 160 in the sample bin 113. Closing the bin gate 170, closing the control valve 150 and the air release valve 135 to separate the sample bin 113 from the vacuum bin 111, and respectively keeping the sample bin and the vacuum bin in a closed state; the vacuum pump 130 and the stop valve 133 are opened, the vacuum pump 130 vacuumizes the vacuum chamber 111, and the reading of the vacuum pressure gauge is stabilized at the preset pressure P3, and the value cannot be changed. After the reading of the oxygen concentration detector has stabilized, the stop valve 133 is closed, and the vacuum pump 130 may be closed. The control valve 150 is opened to communicate the sample chamber 113 with the vacuum chamber 111 and a second concentration O2 of oxygen is recorded after the reading of the oxygen concentration detector has stabilized. The pressures P1, P2, and P3 may be equal to or different from each other, and are not particularly limited herein.
And calculating the concentration change according to the first concentration and the second concentration, and then calculating the soil porosity A according to the concentration change.
A ═ O2-O1 × (V true + V true)/0.217/V ring cutter × 100.
Wherein a represents the porosity, i.e. the volume percentage (Vol.%), of the soil; vure represents the volume of the vacuum chamber 111 in L; sample V represents the volume of the sample compartment 113 in units L; v, the cutting ring represents the volume of the cutting ring, and the unit is L; 0.217 represents 0.217L of oxygen in 1L of atmosphere under standard conditions, namely the volume percent of oxygen is 21.7%; o1 is a first concentration of oxygen, i.e., the volume percent of oxygen (Vol.%); o2 is the second concentration of oxygen, i.e., the volume percent of oxygen (Vol.%).
After the measurement, the air release valve 135 is opened to balance the internal and external pressures of the detection chamber 110, so as not to destroy the sensitivity of the pressure detector 140 and the gas concentration detector 120 due to long-term vacuum. And opening the bin gate 170, taking out the sample to be measured, putting other samples in the bin again, and repeatedly measuring the porosity of other soil samples according to the steps.
The contents of other structures not mentioned in this embodiment are similar to those described in the first embodiment, and are not described again here.
In summary, the soil porosity measuring apparatus 100 and the method provided by the embodiments of the present invention have the following beneficial effects:
the soil porosity measuring device 100 is simple in structure, small in size, light in weight, convenient to carry, wide in application range and suitable for outdoor field measurement. Meanwhile, the measurement can be repeated, the measurement cost is reduced, the measurement efficiency is improved, and the service life is long.
The soil porosity measuring method is simple to operate, does not need to depend on professionals, reduces the operation difficulty and the use threshold, is reliable in measuring principle and accurate in measuring result, greatly improves the measuring efficiency and the measuring precision, reduces the cost, and has great popularization and application values.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. The soil porosity measuring device is characterized by comprising a detection bin, a vacuum pump and a gas concentration detector;
the detection bin comprises a sample bin and a vacuum bin; a control valve is arranged between the sample bin and the vacuum bin and is used for communicating or isolating the sample bin and the vacuum bin;
the sample bin is used for placing samples, the vacuum pump is connected with the vacuum bin, the gas concentration detector is arranged in the vacuum bin, and the vacuum bin is provided with a deflation valve.
2. The soil porosity measurement device of claim 1, wherein the gas concentration detector is an oxygen concentration detector.
3. A soil porosity measuring device according to claim 1, wherein the vacuum chamber is fitted with a pressure detector for detecting the pressure of the vacuum chamber.
4. A soil porosity measurement device according to claim 1, wherein the volume of the vacuum chamber and the volume of the sample chamber are equal.
5. The soil porosity measurement device of claim 4, wherein the vacuum chamber and the sample chamber are each cylinders of equal diameter, the vacuum chamber and the sample chamber being integrally formed.
6. The soil porosity measuring device of claim 1, wherein the vacuum pump is in communication with the vacuum chamber via a conduit, the conduit having a shut-off valve.
7. The soil porosity measurement device of claim 1, wherein a rack is provided in the sample chamber for placing samples.
8. A soil porosity measuring method using the soil porosity measuring apparatus according to claim 1, comprising:
putting the solid standard product into a sample bin;
sealing the detection bin and isolating the vacuum bin from the sample bin;
starting the vacuum pump, and maintaining the pressure of the vacuum bin to be a preset pressure;
closing a stop valve between the vacuum pump and the vacuum chamber, and opening the control valve to communicate the vacuum chamber with the sample chamber; the gas concentration detector records a first concentration of gas O1;
placing a soil sample into the sample bin; sealing the detection bin, separating the vacuum bin from the sample bin, starting the vacuum pump, and maintaining the pressure of the vacuum bin to be the preset pressure;
closing a stop valve between the vacuum pump and the vacuum chamber, and opening the control valve to communicate the vacuum chamber with the sample chamber; the gas concentration detector records a second concentration O2 of the gas;
and calculating the soil porosity A according to the first concentration and the second concentration.
9. The soil porosity measurement method of claim 8, wherein the step of calculating soil porosity A from the first concentration and the second concentration comprises:
a ═ O2-O1 × (V true + V-like)/0.217/V ring cutter × 100;
wherein, a is soil porosity in Vol.%; vure represents the vacuum bin volume, in L; v sample is the volume of the sample bin and is in unit L; the V-ring cutter is the volume of the ring cutter, and the unit is L.
10. The soil porosity measurement method of claim 8, wherein the step of placing the sample into the sample chamber is preceded by:
checking the tightness of the detection bin;
and (5) checking the tightness of the vacuum bin.
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