CN106680304B - Three axis sample water content method for real-timely testing of unsaturated soil - Google Patents
Three axis sample water content method for real-timely testing of unsaturated soil Download PDFInfo
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Abstract
The invention discloses a kind of three axis sample water content method for real-timely testing of unsaturated soil for being based on Time Domain Reflectometry (TDR) technology, can be used for the test of sample part water content in geotechnical engineering unsaturated soil triaxial test.This method is mounted on three axis samples (10) by special flexible probe horizontal wrap, between three axis samples (10) and rubber membrane (4), it is connected by conducting wire (8) with the TDR Test instrument (9) of triaxial cell (7) outside, the water content that installation position can be tested at any time during triaxial test solves the problems, such as that local location water content can not be obtained during geotechnical engineering unsaturation triaxial test.
Description
Technical field
The present invention relates to a kind of soil moisture content real-time test device and methods, are based particularly on Time Domain Reflectometry (TDR) skill
Three axis sample water content real-time testing of unsaturated soil probe, test device and the test method of art.
Background technique
In geotechnical engineering test, triaxial test is to obtain the important tests means of Rock And Soil shearing strength.And Rock And Soil
Shearing strength and the degrees of consolidation of three axis samples have a very close relationship, therefore the water content of sample obtains has important work
Cheng Yiyi, for current research technique, the water content of three axis samples can only obtain before being put into pedestal or after finishing test,
And test the water content in pilot process and directly determined there is presently no method, especially in the triaxial test of unsaturated soil, have
The top and the bottom water content of possible three axis samples is not consistent, therefore during the test if the aqueous of a part can be monitored at any time
Amount will have very big help to the Research on Mechanical Properties of Rock And Soil, also very necessary.
1975, the measurement of Davis and Chudobiak by time domain reflection technology (TDR) applied to soil dielectric constant.
1980, Topp et al. was when using the dielectric constant of TDR measurement soil, it was demonstrated that dielectric constant and soil moisture content have well
Correlation, and establish the empirical equation of soil moisture content and apparent dielectric constant.U.S. scene water content testing standard
ASTM6780 is first to need first to measure the dielectric constant of the soil body using TDR Test water content of soil, then passes through indoor standardization side
Journey obtains the water content of the soil body.Compared with other methods, TDR has many good qualities on soil moisture measurement, such as without destructive, fast
Speed, accuracy height, measurement result are influenced smaller and can measure soil moisture content and soil conductivity simultaneously by soil types.
Commercial TDR instrument is more at present, and most of which can be used for measurement soil moisture content.It needs in test by TDR
In the probe insertion soil body of probe, TDR equipment is controlled by software end and emits electromagnetic wave, while recording reflected electromagnetism
Wave obtains the dielectric constant of the soil body by analysis, then passes through the relationship of the dielectric constant of soil body established in advance and water content
Obtain the water content of the soil body.Currently, most of TDR probe is all probe geometries, need to be inserted into inside soil body, this shape
The probe of formula clearly cannot be used for the water content real-time testing of sample in triaxial test, because the probe of probe-type can try three axis
Sample damages, and directly affects the acquisition of its test parameters.Therefore, TDR technology is applied in triaxial test, is needed separately
Design and develop out the TDR probe and test device suitable for three axis sample water content real-time testings.
Summary of the invention
The purpose of the present invention is to provide a kind of water content real-time testings based on time domain reflection technology (TDR) to pop one's head in, surveys
Trial assembly is set and test method, can be used in the reality of a part water content during three axis specimen test of unsaturated soil in geotechnical engineering
When test.
In order to solve the above technical problems, technical solution proposed by the present invention are as follows:
A kind of three axis sample water content real-time testing of unsaturated soil probe, including flexible bendable base, are set to base one
Face paste invests more fexible conductors of sample, and is set to the connector of base's another side；The fexible conductor and connector
It is electrically connected.
Further, the base is the insulating materials with certain thickness and intensity, and material is polyimide resin.
Further, the fexible conductor is strip conductor made of metallic film, is distributed in base in parallel and concordantly
On, spacing between any two is equal, and the combination with base is gluing or one is made using turmeric technique.
Further, the connector be radio frequency connector, characteristic impedance be 50 Ω or 75 Ω, form be BNC or
SMA。
Correspondingly, the present invention also provides a kind of three axis sample water content real-time test device of unsaturated soil, including three axis
Pressure chamber, TDR Test instrument, in addition, further including above-mentioned test probe, the probe is set to measurement sample needed for rubber membrane and contains
The position of water, the rubber membrane, which is externally provided with, holds film cylinder；The film cylinder that holds is set in triaxial pressure room, and the probe is by leading
Line and TDR Test instrument are electrically connected.
Further, the rubber membrane upper and lower ends are set in from inside to outside holds at film cylinder upper and lower side.
Further, the conducting wire is coaxial cable.
Further, it is equipped with rubber membrane opening at the rubber membrane and probe incorporated, the connector of probe is opened from rubber membrane
The position of mouth is pierced by rubber membrane, and the length direction of probe is arranged along rubber membrane cross circular section circumferential direction.
Further, the rubber membrane opening is filled with sealant.
Based on the above test device, the present invention also provides a kind of test methods, comprising the following steps:
S1: it will be used to attach three axis samples and more fexible conductors at regular intervals is kept to paste in flexible bendable base
On one side, the same end of the fexible conductor passes through base, is electrical connected with the connector for being set to flexbile base another side, and then
To bent flexible probe；
S2: the fexible conductor of flexible probe and base are suitably bent, and are allowed to form arc, and the radius of arc is bigger
In the radius of three axis samples, the side of flexible conductor has the side of connector outside arc in arc shaped inside；
S3: the position that water content is measured needed for three axis samples is positioned on the cylindric rubber membrane of triaxial test
And aperture, rubber membrane opening is formed, openings of sizes is equal to or slightly less than the pedestal cross-sectional sizes of flexible probe upper binding head；
Flexible probe: being placed into the inside of cylindric rubber membrane by S4, opens the connector on flexible probe from rubber membrane
The position of mouth is pierced by rubber membrane, and the length direction of flexible probe is along rubber membrane cross circular section circumferential direction；
S5: the connector bottom for being located at rubber membrane opening and rubber membrane are sealed with sealant；Sealant should have
Have and enough tensile strength and break elongation percentage, during guaranteeing entire triaxial test, radio frequency jointing and rubber membrane it
Between good seal, it is waterproof, it is airtight.
S6: at the top of triaxial cell or bottom punches, and the one end in hole is in triaxial pressure room, and one end is in triaxial cell
Outside, the conducting wire of both ends belt lacing is passed through from hole, is sealed between conducting wire and the hole opened；
S7: by 4 sets of rubber membrane on holding film cylinder, after more solito installs three axis samples, connecting wire is in triaxial pressure
Indoor connector and the connector on flexible probe are simultaneously sealed, and install triaxial cell；
S8: connector of the conducting wire outside triaxial pressure room is connected with TDR Test instrument；
S9: debugging TDR Test instrument, after reacting normal by TDR Test instrument carry out the transmitting of electromagnetic wave, reception,
Processing, obtains the reflective graphics at three axis sample testing positions；
S10: being varied multiple times the water content of three axis samples, repeats above step, establish three axis sample different moisture contents with not
With the corresponding relationship between reflective graphics, the real-time moisture content value at three axis sample testing positions can be obtained.
By apparatus above and method, it can be achieved that a part is aqueous during three axis specimen test of geotechnical engineering unsaturated soil
The real-time testing of amount solves the problems, such as to be unable to real-time testing during testing at present, fills up the blank in the field, facilitates non-full
With the research in native field.
Detailed description of the invention
Fig. 1 is flexible test of the present invention probe bottom schematic view；
Fig. 2 is flexible test of the present invention probe side schematic view；
Fig. 3 is flexible test of the present invention probe schematical top view；
Fig. 4 is the positional relationship cross-sectional view of flexible test of the present invention probe and rubber membrane；
Fig. 5 be flexible test of the present invention probe during installation with the positional diagram of rubber membrane；
Fig. 6 is to be packed into the schematic diagram for holding film cylinder after flexible test of the present invention probe connects rubber membrane；
Fig. 7 is overall structure of the present invention.
In figure: 1- base, 2- fexible conductor, 3- connector, 4- rubber membrane, 5- rubber membrane opening, 6- hold film cylinder, tri- axis of 7-
Pressure chamber, 8- conducting wire, 9-TDR tester, tri- axis sample of 10-.
Specific embodiment
Below in conjunction with Figure of description, the invention will be further described, but protection model not thereby limiting the invention
It encloses.
As shown in Figures 1 to 3, TDR probe is made of flexbile base 1, fexible conductor 2 and 3 three parts of connector, wherein flexible
Base 1 is Kapton insulating layer, and fexible conductor 2 is red copper, strip made of stainless steel or other metal material films
Shape conductor.Connector 3 is radio frequency jointing.
Flexbile base 1 and fexible conductor 2 are directly prepared into one, strip conductor thickness range by gluing or turmeric technique
For 0.1~0.5mm, width range is 1~5mm, and length range is 10~500mm.Fexible conductor 2 has 3, in flexbile base 1
On distribution mode be both ends alignment, parallelly distribute on, spacing is equal two-by-two, and in the same face of flexbile base 1, spacing range is
3~10mm.The size and spacing of fexible conductor 2 can carry out preferred according to factors such as type, the sizes of three axis samples.3 flexibilities
The same end of conductor 2 passes through flexbile base 1 and reaches the another side of flexbile base 1, and passes through welding manner with radio frequency jointing 3
It is connected, wherein conductor in an intermediate position is connected with the middle conductor of radio frequency jointing 3, and other two fexible conductors 2
It is connected with the outer conductor of radio frequency jointing 3, radio frequency jointing 3 is BNC or SMA form, can pass through coaxial cable and standard
Time Domain Reflectometry test equipment be connected, as Compbell Scientific company, the U.S. produce TDR100.
The operating process of triaxial test can be found in People's Republic of China's national regulation " Standard for test methods of earthworks " (GB
T50123-1999).By taking three axis samples of 101mm diameter as an example, flexbile base 1 can be set in 135mm × 21mm rectangle, it is soft
Property conductor 2 be 125mm × 3mm rectangle, three fexible conductors 2 are centrally disposed on flexbile base 1, are parallel to each other, two-by-two spacing
For 3mm.The water content for such as needing to test position among three axis samples, then need to reach following requirement:
1. the present invention is wound in the middle part of sample along sample central cross-section circumference aspect；
2. the one side of the flexible conductor 2 of flexbile base 1 is contacted with specimen surface, and the another side and rubber of flexbile base 1
Film 4 contacts；
3. radio frequency jointing 3 is also needed across rubber membrane 4, sample installation in order to which the present invention can be connected with test equipment
After, radio frequency jointing 3 is in 4 outside of rubber membrane.
As also shown in e.g. figs. 4-7, it in order to which the present invention to be installed in place, can be operated as follows:
(1) in advance the position for measuring water content needed for three axis samples position on rubber membrane 4 and aperture forms rubber
Epithelium opening 5, aperture size is equal to or slightly less than the pedestal cross-sectional sizes of radio frequency jointing 3；
(2) apparatus of the present invention are suitably bent, forms arc, the radius of arc is slightly larger than radius of specimen, flexible
The side of conductor 2 has the side of radio frequency jointing 3 outside arc in arc shaped inside；
(3) present invention is placed into the inside of cylinder-shaped rubber membrane 4, radio frequency jointing 3 is from the position of rubber membrane opening 5
It is pierced by rubber membrane 4, length direction of the invention is along 4 cross circular section circumferential direction of rubber membrane；
(4) 3 bottom of radio frequency jointing and rubber membrane 4 are sealed with sealant, sealant should have enough anti-
Tensile strength and elongation percentage is broken, during guaranteeing entire triaxial test, is sealed between radio frequency jointing 3 and rubber membrane 4 good
It is good, waterproof, airtight, the Kraft spy's K-5904B sealant produced such as Guangdong Hengda New Materials Technology Co., Ltd.
(5) by 4 sets of rubber membrane on holding film cylinder 6, the structure of film cylinder 6 is held referring to People's Republic of China (PRC) national regulation GB
T50123-1999 Figure 16 .2.1-5, because radio frequency jointing 3 has certain height, the diameter for holding film cylinder 6 should be than three
Axis specimen finish adds the radio frequency jointing bigger 2~5mm of height, holds in film cylinder 6 so that three axis samples can be smoothly inserted in.
(6) three axis samples are conventionally installed, specific operation process can refer to People's Republic of China's national regulation
" Standard for test methods of earthworks " (GB T50123-1999).
(7) three axis samples after the installation is completed, by the conducting wire 8 of both ends belt lacing by radio frequency jointing 3 of the invention with
TDR Test instrument 9 outside pressure chamber is connected.Conducting wire 8 is coaxial cable, is punched extractions at pressure chamber base position, coaxial cable and
It is sealed between the hole opened, sealing means can be the combination etc. for adding capstan nut with sealant or sealing ring.Coaxial electrical
Cable should seal after connecting with radio frequency jointing 3 of the invention, and seal form can be laced belt waterproof plug itself, can also be with
It being sealed with sealant, coaxial cable+connector crust itself should be that waterproof is air-locked, in order to avoid water is caused during the test
Or gas enters change characteristic impedance in coaxial cable, influences water content test result, while also avoiding that triaxial cell is caused to enclose
Pressure decaying.
(8) TDR Test instrument is debugged, after reacting normal by TDR Test instrument carry out the transmitting of electromagnetic wave, reception,
Processing obtains the reflective graphics at three axis sample testing positions, while obtaining three axis sample quilts by conventional method (such as oven drying method)
Survey the water content at position.
(9) be varied multiple times the water content of three axis samples, repeat above step, establish three axis sample different moisture contents from it is different
Corresponding relationship between reflective graphics.
(10) triaxial test is carried out according to a conventional method, carries out the hair of electromagnetic wave during test by TDR Test instrument at any time
It penetrates, receive, handle, obtain the reflective graphics at three axis sample testing positions, between the reflective graphics established by step (9)
The real-time moisture content value at three axis sample testing positions can be obtained in corresponding relationship.
The principle of TDR water content test can refer to the article that Cheng Xianjun is published in " water conservancy and hydropower technology " nineteen ninety-five o. 11th
" soil moisture content is measured according to TDR principle ".As long as demarcating in advance to apparatus of the present invention, pass through the data progress to acquisition
Analysis, obtains dielectric constant values, further establishes the relationship between dielectric constant and three axis sample water content, that is, can determine aqueous
Amount, to realize the real time measure of water content.
If you need to carry out the water content real-time testing at three other positions of axis sample, it can refer to the above method and pacify apparatus of the present invention
Mounted in corresponding position.
As described above, embodiment of the invention is described in detail, but as long as essentially without this hair is detached from
Bright feature and effect, can there is many variations, this will be readily apparent to persons skilled in the art, therefore,
The example of these deformations is also integrally incorporated within protection scope of the present invention.
Claims (6)
1. a kind of three axis sample water content method for real-timely testing of unsaturated soil, which comprises the following steps:
S1: it will be used to attach three axis samples (10) and more fexible conductors (2) at regular intervals is kept to paste at flexible bendable
The same end of base (1) one side, the fexible conductor (2) passes through base (1), with the connection for being set to flexbile base (1) another side
Head (3) is electrical connected, and then obtains bent flexible probe；
S2: the fexible conductor (2) of flexible probe and base (1) are suitably bent, and are allowed to form arc, and the radius of arc omits
Greater than the radius of three axis samples (10), the side of flexible conductor (2) has the side of connector (3) in arc in arc shaped inside
It is external；
S3: the position that water content is measured needed for three axis samples is positioned on the cylindric rubber membrane (4) of triaxial test
And aperture, rubber membrane opening (5) is formed, the pedestal section that openings of sizes is equal to or slightly less than flexible probe upper binding head (3) is big
It is small；
Flexible probe: being placed into the inside of cylindric rubber membrane (4) by S4, makes connector (3) on flexible probe from rubber membrane
The position of opening (5) is pierced by rubber membrane (4), and the length direction of flexible probe is along rubber membrane (4) cross circular section circumferential direction；
S5: with sealant by be located at rubber membrane opening (5) at connector (3) bottom and rubber membrane (4) be sealed；
S6: at the top of triaxial cell (7) or bottom punches, and the one end in hole is in triaxial cell (7), and one end is in triaxial pressure
Room (7) outside, the conducting wire (8) of both ends belt lacing is passed through from hole, is sealed between conducting wire (8) and the hole opened；
S7: rubber membrane (4) is covered on holding film cylinder (6), and after more solito installs three axis samples (10), connecting wire (8) exists
Connector (3) on connector and flexible probe in triaxial cell (7) is simultaneously sealed, and installs triaxial cell (7)；
S8: conducting wire (8) is connected in the connector of triaxial cell (7) outside with TDR Test instrument (9)；
S9: debugging TDR Test instrument (9), carries out the transmitting of electromagnetic wave by TDR Test instrument (9) after reacting normal, connects
It receives, processing, obtains the reflective graphics of three axis sample (10) test positions；
S10: being varied multiple times the water content of three axis samples (10), repeats above step, establishes three axis sample (10) different moisture contents
With the corresponding relationship between different reflection graphic shape；Triaxial test is carried out according to a conventional method, passes through TDR Test during test at any time
Instrument carries out transmitting, reception, the processing of electromagnetic wave, obtains the reflective graphics at three axis sample testing positions, is established by step S9
Reflective graphics between corresponding relationship, the real-time moisture content value at three axis sample testing positions can be obtained.
2. three axis sample water content method for real-timely testing of a kind of unsaturated soil according to claim 1, which is characterized in that institute
Stating base (1) is the insulating materials with certain thickness and intensity, and material is polyimide resin.
3. three axis sample water content method for real-timely testing of a kind of unsaturated soil according to claim 1, which is characterized in that institute
Stating fexible conductor (2) is strip conductor made of metallic film, is distributed on base (1) in parallel and concordantly, between any two
Spacing is equal, and the combination with base (1) is gluing or one is made using turmeric technique.
4. three axis sample water content method for real-timely testing of a kind of unsaturated soil according to claim 1, which is characterized in that institute
Stating connector (3) is radio frequency connector, and characteristic impedance is 50 Ω or 75 Ω, and form is BNC or SMA.
5. three axis sample water content method for real-timely testing of a kind of unsaturated soil according to claim 1, which is characterized in that institute
It states rubber membrane (4) upper and lower ends and is set in from inside to outside and hold at film cylinder (6) upper and lower side.
6. three axis sample water content method for real-timely testing of a kind of unsaturated soil according to claim 1, which is characterized in that institute
Stating conducting wire (8) is coaxial cable.
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| CN111189702A (en) * | 2020-01-10 | 2020-05-22 | 甘肃省地震局（中国地震局兰州地震研究所） | Device for researching clay characteristics by using static triaxial electrical method |
| CN111999211A (en) * | 2020-08-07 | 2020-11-27 | 湖南大学 | Method for acquiring soil pore water density |
| CN116660328B (en) * | 2023-07-26 | 2023-10-20 | 中国地质大学（北京） | Method and device for obtaining rock volume water content through rock dielectric constant |
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| US6956381B2 (en) * | 2001-10-12 | 2005-10-18 | The Board Of Regents Of University And Community College System Of Nevada On Behalf Of The Desert Research Institute | Flexible probe for measuring moisture content in soil |
| US9696292B2 (en) * | 2011-10-28 | 2017-07-04 | Purdue Research Foundation | Time domain reflectometry for characterizing soils |
| CN103018085A (en) * | 2012-12-11 | 2013-04-03 | 中南大学 | Method and device for preparing silty soil triaxial-test test sample |
| CN103743787B (en) * | 2013-12-23 | 2016-06-08 | 石家庄铁道大学 | A kind of triaxial test soil sample water content distribution test device |
| CN203965256U (en) * | 2014-07-30 | 2014-11-26 | 中国科学院、水利部成都山地灾害与环境研究所 | A kind of portable triaxial apparatus |
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