CN111220792B - Method for calculating infiltration depth of unsaturated loess water - Google Patents
Method for calculating infiltration depth of unsaturated loess water Download PDFInfo
- Publication number
- CN111220792B CN111220792B CN202010073036.8A CN202010073036A CN111220792B CN 111220792 B CN111220792 B CN 111220792B CN 202010073036 A CN202010073036 A CN 202010073036A CN 111220792 B CN111220792 B CN 111220792B
- Authority
- CN
- China
- Prior art keywords
- soil sample
- water
- undisturbed soil
- undisturbed
- saturation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 118
- 238000001764 infiltration Methods 0.000 title claims abstract description 39
- 230000008595 infiltration Effects 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 34
- 239000002689 soil Substances 0.000 claims abstract description 209
- 239000011148 porous material Substances 0.000 claims abstract description 42
- 239000002352 surface water Substances 0.000 claims abstract description 13
- 238000007654 immersion Methods 0.000 claims abstract description 10
- 238000012360 testing method Methods 0.000 claims description 20
- 230000008569 process Effects 0.000 claims description 10
- 238000013421 nuclear magnetic resonance imaging Methods 0.000 claims description 9
- 230000011218 segmentation Effects 0.000 claims description 4
- 230000001419 dependent effect Effects 0.000 claims description 3
- 238000013461 design Methods 0.000 claims description 3
- 238000013507 mapping Methods 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 4
- 230000005484 gravity Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 230000003068 static effect Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 230000035515 penetration Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 208000005156 Dehydration Diseases 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D1/00—Investigation of foundation soil in situ
- E02D1/02—Investigation of foundation soil in situ before construction work
- E02D1/027—Investigation of foundation soil in situ before construction work by investigating properties relating to fluids in the soil, e.g. pore-water pressure, permeability
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
- G01N24/081—Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
-
- 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
- G01N2015/0813—Measuring intrusion, e.g. of mercury
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- High Energy & Nuclear Physics (AREA)
- Geology (AREA)
- Environmental & Geological Engineering (AREA)
- Geochemistry & Mineralogy (AREA)
- Medicinal Chemistry (AREA)
- Remote Sensing (AREA)
- Food Science & Technology (AREA)
- Dispersion Chemistry (AREA)
- Hydrology & Water Resources (AREA)
- Soil Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a method for calculating the infiltration depth of unsaturated loess water, which comprises the following steps: firstly, collecting an undisturbed soil sample; secondly, measuring the contact angle of the soil sample in the undisturbed soil sample; thirdly, measuring the aperture size of the soil sample without disturbing the soil sample; fourthly, capillary resistance of capillary pores of the soil sample in the undisturbed soil sample is measured; fifthly, measuring the surface water head pressure of the water immersion area; sixthly, calculating the infiltration depth of the unsaturated loess water. The invention provides a new infiltration formula suitable for unsaturated soil by correcting a standard Jurin criterion, acquiring capillary resistance F in capillary pores of a soil sample in an undisturbed soil sample and considering the influence of surface water head pressure of a water-soaked area on the downward movement of unsaturated soil moisture in a loess area, so that a measurement result is ideal.
Description
Technical Field
The invention belongs to the technical field of calculation of the infiltration depth of unsaturated loess water, and particularly relates to a calculation method of the infiltration depth of unsaturated loess water.
Background
Loess is widely distributed around the world, and in the loess region, a large amount of loess has self-weight collapsibility (significant additional settlement due to being soaked in water under an overburden pressure), while the loess layer tends to be thick, which greatly affects local construction works. According to the national building Standard for collapsible loess areas GB50025-2018, most of total self-weight collapsible loess or self-weight collapsible loess needs to be treated for important buildings. However, in areas where the loess is thick, the foundation treatment cost is high, and the construction period is long. In large-scale projects such as subways and high-speed trains, a large number of test field immersion tests are performed on dead-weight collapsible loess sites in order to save investment. Experiments show that the water penetration speed gradually decreases with the increase of the depth, the water content and the saturation of the loess are not obviously increased compared with the original state at a certain depth, and the loess is not saturated far away, namely, the penetration stops, and the depth is called the critical infiltration surface depth. Below this depth, the loess is not soaked in water, the water content and saturation of the loess are not increased, and no collapsible occurs. That is, the critical infiltration surface depth caused by infiltration of the ground surface in the loess region is very limited, and is far less than the lower limit depth of self-weight collapse (MDP) of loess determined by an indoor test. Therefore, the critical infiltration surface depth can be used as the maximum foundation treatment depth of important engineering, a large amount of capital is reduced, considerable economic benefit is brought, and the pit immersion test in the field test has high cost, long time consumption and large occupied area. However, no method for calculating the depth of the loess critical infiltration surface exists at present.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for calculating the infiltration depth of unsaturated loess water, which can be used for calculating the depth of a critical infiltration surface in the loess infiltration process, collect capillary resistance F in capillary pores of an undisturbed soil sample by correcting the standard Jurin standard, and consider the influence of the surface head pressure of an infiltration area on the downward movement of unsaturated soil water in a loess area, so that the measurement result is ideal, and the undisturbed soil sample is placed indoors to measure the contact angle of the undisturbed soil sample, the aperture size of the soil sample, the capillary resistance in the capillary pores of the soil sample and the surface head pressure of the infiltration area by collecting the undisturbed soil sample in the infiltration area, so that the method has the advantages of less time consumption, low cost, small deviation of the obtained result from the actual situation, suitability for unsaturated loess and other unsaturated soils, is convenient for popularization and use.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for calculating the infiltration depth of unsaturated loess water is characterized by comprising the following steps:
step one, collecting an undisturbed soil sample: collecting an undisturbed soil sample in a water-immersed area according to the quality design requirement of the undisturbed soil sample;
step two, measuring the contact angle of the soil sample in the undisturbed soil sample;
step three, measuring the aperture size of the soil sample without disturbing the soil sample;
step four, measuring capillary resistance of capillary pores of the soil sample in the undisturbed soil sample;
measuring the surface water head pressure of the water immersion area;
step six, according to the formula
Calculating the infiltration depth h of unsaturated loess watercWherein F is capillary resistance of capillary pores of the soil sample in the undisturbed soil sample, w is surface water head pressure of the water immersion area, r is the pore size of the soil sample in the undisturbed soil sample, T is the surface tension of the undisturbed soil sample, alpha is the contact angle of the soil sample in the undisturbed soil sample, and gamma is the pore size of the capillary pores in the undisturbed soil samplewIs the heaviness of the water.
The method for calculating the infiltration depth of unsaturated loess water is characterized by comprising the following steps of: in the second step, a contact angle measuring instrument is used for measuring the contact angle alpha of the soil sample in the undisturbed soil sample; and in the third step, the nuclear magnetic resonance imaging analyzer is used for measuring the aperture size r of the soil sample in the undisturbed soil sample.
The method for calculating the infiltration depth of unsaturated loess water is characterized by comprising the following steps of: in the fourth step, the process of measuring the capillary resistance of the capillary pores of the soil sample without disturbing the soil sample comprises the following steps:
step 401, obtaining the saturation of the irretentive water in the undisturbed soil sample to be tested: determining the saturation of the irretentive water in the undisturbed soil sample to be detected by using a nuclear magnetic resonance imaging analyzer;
step 402, placing an undisturbed soil sample to be tested: placing filter paper at the bottom of the centrifugal sleeve, taking the undisturbed soil sample to be detected out of the nuclear magnetic resonance imaging analyzer, wrapping gauze or a thermal shrinkage film outside the undisturbed soil sample, and placing the undisturbed soil sample in the centrifugal sleeve with the filter paper;
step 403, centrifugal test of the undisturbed soil sample to be tested: putting the centrifugal sleeve filled with the undisturbed soil sample to be tested into a centrifugal machine; respectively loading three samples with the same mass and the same shape as the undisturbed soil sample to be tested into the centrifugal sleeves and putting the samples into a centrifugal machine, so that four centrifugal sleeves in the centrifugal machine are arranged in a centrosymmetric manner; covering a centrifuge cover, setting the rotation speed of the centrifuge, and carrying out a centrifugal test on the undisturbed soil sample to be tested;
step 404, obtaining a current centrifugal force: according to the formula
Calculating the current centrifugal force P, wherein delta rho is the difference between water density and air density, L is the length of the undisturbed soil sample to be measured, and ReThe external rotation radius of the undisturbed soil sample to be detected is n, and the rotation speed of the centrifugal machine is n;
step 405, dewatering the undisturbed soil sample to be detected: after the centrifugal test of the undisturbed soil sample to be tested is finished, taking the undisturbed soil sample to be tested out of the centrifugal sleeve, absorbing water stains on the surface of the undisturbed soil sample to be tested, changing the undisturbed soil sample to be tested into a tested soil sample, and weighing the quality of the tested soil sample;
step 406, taking the tested soil sample as an undisturbed soil sample to be tested, and circulating the step 401 to the step 405 until the saturation of the bound water in the undisturbed soil sample to be tested is less than 20 percent;
step 407, obtaining a micro-segment interpolation function of the current centrifugal force on the irreducible water saturation: establishing a nonlinear relation between the irreducible water saturation and the corresponding current centrifugal force by utilizing origin software, calling a nonlinear curve fitting module in the origin software, and fitting a curve between the irreducible water saturation and the corresponding current centrifugal force; introducing a curve between the saturation of the bound water fitted in origin software and the corresponding current centrifugal force into MATLAB numerical analysis software, segmenting the curve into micro segments, and performing micro-segment segmentation on each micro segmentIn the section curve, an interpolation method is adopted to obtain a micro-section interpolation function P of each micro-section curvei＝fi(x) Wherein the variable x represents irreducible water saturation, PiIs the current dependent centrifugal force variable, f, in the ith curve for variable xi(. h) is a functional mapping relation of the current centrifugal force in the ith micro-segment curve with respect to the irreducible water saturation, I is a micro-segment curve number, and I is 1,2, … I, wherein I is the total segmentation number of the micro-segment curve in the curve between the fitted irreducible water saturation and the corresponding current centrifugal force;
step 408, determining capillary resistance of capillary pores of the soil sample in the undisturbed soil sample: according to the formula
Calculating the micro-segment interpolation function P of the ith micro-segment curvei＝fi(x) Radius of curvature R ofiWherein P isiIs' PiFirst derivative of, PiIs "PiThe second derivative of (a);
sorting the I curvature radius values from big to small to obtain the minimum curvature radius Rmin；
Then passing through the minimum curvature radius RminObtaining irreducible water saturation x at corresponding position0；
Saturation x of irreducible water0Substituting the saturation x of the irreducible water into a corresponding micro-segment interpolation function to calculate the saturation x of the irreducible water at the moment0The corresponding centrifugal force firstly destroys the soil body structure before capillary water in the capillary pores of the soil completely flows out, and the minimum curvature radius RminThe soil body structure is destroyed, and the centrifugal force when the soil body structure of the undisturbed soil sample to be detected is the capillary resistance of the capillary pores of the soil sample in the undisturbed soil sample, namely the saturation x of the bound water0The corresponding centrifugal force is capillary resistance F which does not disturb capillary pores of the soil sample in the soil sample.
The method for calculating the infiltration depth of unsaturated loess water is characterized by comprising the following steps of: in step 407, when the curves are segmented into micro-segments, the absolute value of the difference between the saturation of the irreducible water corresponding to the two endpoints in each micro-segment curve is 10-5～5×10-5。
Compared with the prior art, the invention has the following advantages:
1. according to the method, the standard Jurin criterion is corrected, capillary resistance F in capillary pores of the soil sample in the undisturbed soil sample is collected, and the influence of the surface water head pressure of the water-soaked area on the downward movement of unsaturated soil moisture in the loess area is considered, so that the measuring result is ideal, reliable and stable, the using effect is good, and the method is convenient to popularize and use.
2. The method has simple steps, and the undisturbed soil sample is placed indoors to measure the contact angle of the undisturbed soil sample, the aperture size of the soil sample, the capillary resistance in capillary pores of the soil sample and the surface water head pressure of the immersed area through the undisturbed soil sample in the immersed area, so that the time consumption is low, the cost is low, and the deviation of the obtained result from the actual situation is small.
In conclusion, the method can be used for calculating the depth of the critical infiltration surface in the loess infiltration process, collecting capillary resistance F in capillary pores of the soil sample in the undisturbed soil sample by correcting the standard Jurin criterion, and considering the influence of the surface water head pressure of the infiltration area on the downward movement of the unsaturated soil moisture in the loess area, so that the measurement result is ideal.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a block diagram of the process flow of the present invention.
Fig. 2 is a grey scale plot of water column in a simulated capillary.
FIG. 3 is a graph of the force analysis of the simulated capillary of FIG. 2 under the standard Jurin criteria.
Fig. 4 is a force model diagram of a capillary water in a static state.
Fig. 5 is an inverse capillary water force analysis plot.
FIG. 6 is a diagram of the analysis of the water permeability under capillary.
Detailed Description
As shown in fig. 1 to 6, a method for calculating the infiltration depth of unsaturated loess water according to the present invention includes the steps of:
step one, collecting an undisturbed soil sample: collecting an undisturbed soil sample in a water-immersed area according to the quality design requirement of the undisturbed soil sample;
step two, measuring the contact angle of the soil sample in the undisturbed soil sample;
step three, measuring the aperture size of the soil sample without disturbing the soil sample;
step four, measuring capillary resistance of capillary pores of the soil sample in the undisturbed soil sample;
measuring the surface water head pressure of the water immersion area;
step six, according to the formula
Calculating the infiltration depth h of unsaturated loess watercWherein F is capillary resistance of capillary pores of the soil sample in the undisturbed soil sample, w is surface water head pressure of the water immersion area, r is the pore size of the soil sample in the undisturbed soil sample, T is the surface tension of the undisturbed soil sample, alpha is the contact angle of the soil sample in the undisturbed soil sample, and gamma is the pore size of the capillary pores in the undisturbed soil samplewIs the heaviness of the water.
In the second step, a contact angle measuring instrument is used for measuring the contact angle alpha of the soil sample in the undisturbed soil sample; and in the third step, the nuclear magnetic resonance imaging analyzer is used for measuring the aperture size r of the soil sample in the undisturbed soil sample.
In this embodiment, in the fourth step, the process of measuring the capillary resistance of the capillary pores of the soil sample without disturbing the soil sample is as follows:
step 401, obtaining the saturation of the irretentive water in the undisturbed soil sample to be tested: determining the saturation of the irretentive water in the undisturbed soil sample to be detected by using a nuclear magnetic resonance imaging analyzer;
in step 401, the T2 spectrum distribution diagram output by the mri analyzer is used to determine the irreducible water saturation in the soil sample to be tested.
Step 402, placing an undisturbed soil sample to be tested: placing filter paper at the bottom of the centrifugal sleeve, taking the undisturbed soil sample to be detected out of the nuclear magnetic resonance imaging analyzer, wrapping gauze or a thermal shrinkage film outside the undisturbed soil sample, and placing the undisturbed soil sample in the centrifugal sleeve with the filter paper;
step 403, centrifugal test of the undisturbed soil sample to be tested: putting the centrifugal sleeve filled with the undisturbed soil sample to be tested into a centrifugal machine; respectively loading three samples with the same mass and the same shape as the undisturbed soil sample to be tested into the centrifugal sleeves and putting the samples into a centrifugal machine, so that four centrifugal sleeves in the centrifugal machine are arranged in a centrosymmetric manner; covering a centrifuge cover, setting the rotation speed of the centrifuge, and carrying out a centrifugal test on the undisturbed soil sample to be tested;
step 404, obtaining a current centrifugal force: according to the formula
Calculating the current centrifugal force P, wherein delta rho is the difference between water density and air density, L is the length of the undisturbed soil sample to be measured, and ReThe external rotation radius of the undisturbed soil sample to be detected is n, and the rotation speed of the centrifugal machine is n;
step 405, dewatering the undisturbed soil sample to be detected: after the centrifugal test of the undisturbed soil sample to be tested is finished, taking the undisturbed soil sample to be tested out of the centrifugal sleeve, absorbing water stains on the surface of the undisturbed soil sample to be tested, changing the undisturbed soil sample to be tested into a tested soil sample, and weighing the quality of the tested soil sample;
step 406, taking the tested soil sample as an undisturbed soil sample to be tested, and circulating the step 401 to the step 405 until the saturation of the bound water in the undisturbed soil sample to be tested is less than 20 percent;
step 407, obtaining a micro-segment interpolation function of the current centrifugal force on the irreducible water saturation: establishing a nonlinear relation between the irreducible water saturation and the corresponding current centrifugal force by utilizing origin software, calling a nonlinear curve fitting module in the origin software, and fitting a curve between the irreducible water saturation and the corresponding current centrifugal force; fitting irreducible water saturation and corresponding current centrifugal force in origin softwareThe curve between the two is led into MATLAB numerical analysis software, the curve is divided into micro-segments, and in each micro-segment curve, an interpolation method is adopted to obtain a micro-segment interpolation function P of each micro-segment curvei＝fi(x) Wherein the variable x represents irreducible water saturation, PiIs the current dependent centrifugal force variable, f, in the ith curve for variable xi(. h) is a functional mapping relation of the current centrifugal force in the ith micro-segment curve with respect to the irreducible water saturation, I is a micro-segment curve number, and I is 1,2, … I, wherein I is the total segmentation number of the micro-segment curve in the curve between the fitted irreducible water saturation and the corresponding current centrifugal force;
step 408, determining capillary resistance of capillary pores of the soil sample in the undisturbed soil sample: according to the formula
Calculating the micro-segment interpolation function P of the ith micro-segment curvei＝fi(x) Radius of curvature R ofiWherein P isiIs' PiFirst derivative of, PiIs "PiThe second derivative of (a);
sorting the I curvature radius values from big to small to obtain the minimum curvature radius Rmin；
Then passing through the minimum curvature radius RminObtaining irreducible water saturation x at corresponding position0；
Saturation x of irreducible water0Substituting the saturation x of the irreducible water into a corresponding micro-segment interpolation function to calculate the saturation x of the irreducible water at the moment0The corresponding centrifugal force firstly destroys the soil body structure before capillary water in the capillary pores of the soil completely flows out, and the minimum curvature radius RminThe soil body structure is destroyed, and the centrifugal force when the soil body structure of the undisturbed soil sample to be detected is the capillary resistance of the capillary pores of the soil sample in the undisturbed soil sample, namely the saturation x of the bound water0The corresponding centrifugal force is capillary resistance F which does not disturb capillary pores of the soil sample in the soil sample.
In this embodiment, in step 407, when the curves are segmented into micro-segments, the absolute value of the difference between the saturation of the irreducible water corresponding to the two endpoints in each micro-segment curve is 10-5～5×10-5。
Note that the Jurin criterion for the standard
The obtained result is often deviated from the actual situation, wherein rho is the density of water, g is the gravity acceleration, and h is the rising height of the water in the capillary; especially when the soil body is dense and the pore diameter of the pore is small. As shown in FIG. 2, a capillary tube having a diameter (inner diameter of the quartz tube) of 0.5mm was simulated using a quartz tube. A small drop of water was placed in the capillary and a small amount of pigment was added dropwise to the small drop for easy observation. The capillary is erected, and it is found that the water column in the capillary is kept static and can not move upwards or downwards, according to the Jurin standard, the force applied to the water column is gravity G and surface tension T, and the upper surface and the lower surface (i.e. meniscus) of the water column are both applied with surface tension, the fluctuation of the upper surface and the lower surface of the water column of the capillary is not different, i.e. the upper surface tension and the lower surface tension of the water column are equal, the small water column is kept balanced under the action of the upward tension, the downward tension and the gravity G, as shown in figure 3, T' is the component force of the tension in the vertical direction, obviously, the situation is impossible, because the upward tension and the downward tension are equal. The above phenomenon fully explains that when the water is in a static state in the capillary, the water is acted by surface tension and gravity, and also acted by another force, namely viscous frictional resistance generated by adhesion force between the capillary liquid and the pipe wall in a direction perpendicular to the pipe wall.
Through the analysis, the stress model of the capillary water in the static state is shown in FIG. 4, and the form of Jurin criterion should be modified to pi r2γwhc+F＝2πrTcosα。
During the pit soaking test, the essence of the seepage is the process of water seepage along the capillary holes, namely the capillary water moves downwards, the cross section of the capillary water shown in FIG. 4 is rotated by 180 degrees, and the inverse capillary water force diagram shown in FIG. 5 is obtained. The movement of water in fig. 5 is very similar to the test pit submersion test. Thus, we can view the pit submergence test as inverting the capillary water rise process, in FIG. 5, capillary waterMoving downwards, the surface tension tends to move downwards in the same direction as the gravity, however, the capillary resistance moves upwards along with the opposite direction of the gravity and the surface tension, in this case, the gravity and the surface tension are driving forces of seepage, the capillary resistance is actually resistance of seepage, meanwhile, as specified in Chinese collapsible loess area building Standard GB50025-2018, water with the depth of 50cm exists in a test pit, the water head pressure also exists in the seepage process, which is also considered as the driving force of seepage, the water stress of the capillary is shown in figure 6, the resistance F is continuously increased along with the increase of the depth, and under a certain depth, the resistance F is balanced with the water head pressure, the gravity and the surface tension, then, the seepage is stopped, and the seepage stop depth is a key seepage surface. Thus, the modified Jurin criterion may be employed to calculate the critical penetration surface depth for a loess pit immersion test. As the direction of the force changes, the modified and optimized Jurin criterion is as follows: pi r2γwhc+2 π rTcos α + w ═ F, at which time the modified and optimized Jurin criterion is transformed
Calculating the infiltration depth h of unsaturated loess waterc。
When the method is used, the depth of a critical infiltration surface in the loess infiltration process can be calculated, the capillary resistance F in capillary pores of the soil sample in the undisturbed soil sample is acquired by correcting the standard Jurin standard, the influence of the surface water head pressure of the infiltration area on the downward movement of the unsaturated soil moisture in the loess area is considered, so that the measurement result is ideal, the undisturbed soil sample is placed indoors to measure the contact angle of the undisturbed soil sample, the pore size of the soil sample, the capillary resistance in the capillary pores of the soil sample and the surface water head pressure of the infiltration area by acquiring the undisturbed soil sample in the infiltration area, the time consumption is low, the cost is low, the deviation of the obtained result from the actual condition is small, and the method is suitable for unsaturated loess and other unsaturated soils.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (4)
1. A method for calculating the infiltration depth of unsaturated loess water is characterized by comprising the following steps:
step one, collecting an undisturbed soil sample: collecting an undisturbed soil sample in a water-immersed area according to the quality design requirement of the undisturbed soil sample;
step two, measuring the contact angle of the soil sample in the undisturbed soil sample;
step three, measuring the aperture size of the soil sample without disturbing the soil sample;
step four, measuring capillary resistance of capillary pores of the soil sample in the undisturbed soil sample;
measuring the surface water head pressure of the water immersion area;
step six, according to the formula
Calculating the infiltration depth h of unsaturated loess watercWherein F is capillary resistance of capillary pores of the soil sample in the undisturbed soil sample, w is surface water head pressure of the water immersion area, r is the pore size of the soil sample in the undisturbed soil sample, T is the surface tension of the undisturbed soil sample, alpha is the contact angle of the soil sample in the undisturbed soil sample, and gamma is the pore size of the capillary pores in the undisturbed soil samplewIs the heaviness of the water.
2. The method for calculating the infiltration depth of unsaturated loess water according to claim 1, wherein: in the second step, a contact angle measuring instrument is used for measuring the contact angle alpha of the soil sample in the undisturbed soil sample; and in the third step, the nuclear magnetic resonance imaging analyzer is used for measuring the aperture size r of the soil sample in the undisturbed soil sample.
3. The method for calculating the infiltration depth of unsaturated loess water according to claim 1, wherein: in the fourth step, the process of measuring the capillary resistance of the capillary pores of the soil sample without disturbing the soil sample comprises the following steps:
step 401, obtaining the saturation of the irretentive water in the undisturbed soil sample to be tested: determining the saturation of the irretentive water in the undisturbed soil sample to be detected by using a nuclear magnetic resonance imaging analyzer;
step 402, placing an undisturbed soil sample to be tested: placing filter paper at the bottom of the centrifugal sleeve, taking the undisturbed soil sample to be detected out of the nuclear magnetic resonance imaging analyzer, wrapping gauze or a thermal shrinkage film outside the undisturbed soil sample, and placing the undisturbed soil sample in the centrifugal sleeve with the filter paper;
step 403, centrifugal test of the undisturbed soil sample to be tested: putting the centrifugal sleeve filled with the undisturbed soil sample to be tested into a centrifugal machine; respectively loading three samples with the same mass and the same shape as the undisturbed soil sample to be tested into the centrifugal sleeves and putting the samples into a centrifugal machine, so that four centrifugal sleeves in the centrifugal machine are arranged in a centrosymmetric manner; covering a centrifuge cover, setting the rotation speed of the centrifuge, and carrying out a centrifugal test on the undisturbed soil sample to be tested;
step 404, obtaining a current centrifugal force: according to the formula
Calculating the current centrifugal force P, wherein delta rho is the difference between water density and air density, L is the length of the undisturbed soil sample to be measured, and ReThe external rotation radius of the undisturbed soil sample to be detected is n, and the rotation speed of the centrifugal machine is n;
step 405, dewatering the undisturbed soil sample to be detected: after the centrifugal test of the undisturbed soil sample to be tested is finished, taking the undisturbed soil sample to be tested out of the centrifugal sleeve, absorbing water stains on the surface of the undisturbed soil sample to be tested, changing the undisturbed soil sample to be tested into a tested soil sample, and weighing the quality of the tested soil sample;
step 406, taking the tested soil sample as an undisturbed soil sample to be tested, and circulating the step 401 to the step 405 until the saturation of the bound water in the undisturbed soil sample to be tested is less than 20 percent;
step 407, obtaining a micro-segment interpolation function of the current centrifugal force on the irreducible water saturation: establishing a nonlinear relation between the saturation of the bound water and the corresponding current centrifugal force by utilizing origin software, calling a nonlinear curve fitting module in the origin software, and fitting the bound waterA curve between saturation and corresponding current centrifugal force; introducing a curve between the saturation of the bound water fitted in origin software and the corresponding current centrifugal force into MATLAB numerical analysis software, segmenting the curve into micro-segments, and calculating a micro-segment interpolation function P of each micro-segment curve in each micro-segment curve by adopting an interpolation methodi＝fi(x) Wherein the variable x represents irreducible water saturation, PiIs the current dependent centrifugal force variable, f, in the ith curve for variable xi(. h) is a functional mapping relation of the current centrifugal force in the ith micro-segment curve with respect to the irreducible water saturation, I is a micro-segment curve number, and I is 1,2, … I, wherein I is the total segmentation number of the micro-segment curve in the curve between the fitted irreducible water saturation and the corresponding current centrifugal force;
step 408, determining capillary resistance of capillary pores of the soil sample in the undisturbed soil sample: according to the formula
Calculating the micro-segment interpolation function P of the ith micro-segment curvei＝fi(x) Radius of curvature R ofiWherein P isiIs' PiFirst derivative of, PiIs "PiThe second derivative of (a);
sorting the I curvature radius values from big to small to obtain the minimum curvature radius Rmin；
Then passing through the minimum curvature radius RminObtaining irreducible water saturation x at corresponding position0；
Saturation x of irreducible water0Substituting the saturation x of the irreducible water into a corresponding micro-segment interpolation function to calculate the saturation x of the irreducible water at the moment0The corresponding centrifugal force firstly destroys the soil body structure before capillary water in the capillary pores of the soil completely flows out, and the minimum curvature radius RminThe soil body structure is destroyed, and the centrifugal force when the soil body structure of the undisturbed soil sample to be detected is the capillary resistance of the capillary pores of the soil sample in the undisturbed soil sample, namely the saturation x of the bound water0The corresponding centrifugal force is capillary resistance F which does not disturb capillary pores of the soil sample in the soil sample.
4. The method for calculating the infiltration depth of unsaturated loess water according to claim 3, wherein: in step 407, when the curves are segmented into micro-segments, the absolute value of the difference between the saturation of the irreducible water corresponding to the two endpoints in each micro-segment curve is 10-5～5×10-5。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010073036.8A CN111220792B (en) | 2020-01-22 | 2020-01-22 | Method for calculating infiltration depth of unsaturated loess water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010073036.8A CN111220792B (en) | 2020-01-22 | 2020-01-22 | Method for calculating infiltration depth of unsaturated loess water |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111220792A CN111220792A (en) | 2020-06-02 |
| CN111220792B true CN111220792B (en) | 2020-12-29 |
Family
ID=70829617
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010073036.8A Expired - Fee Related CN111220792B (en) | 2020-01-22 | 2020-01-22 | Method for calculating infiltration depth of unsaturated loess water |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111220792B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117779722A (en) * | 2024-02-26 | 2024-03-29 | 中国科学院武汉岩土力学研究所 | Soil layer in-situ testing device and method combining nuclear magnetic resonance with static sounding |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103971002A (en) * | 2014-05-12 | 2014-08-06 | 北京交通大学 | Method for calculating relative permeability coefficient of unsaturated soil |
| CN204694592U (en) * | 2015-06-17 | 2015-10-07 | 成都理工大学 | A kind of measurement repellency soil contact angle test unit |
| CN105136644B (en) * | 2015-09-07 | 2019-04-12 | 华东交通大学 | The derivation method of hole effective aperture between clay particle |
| CN110499751A (en) * | 2019-08-02 | 2019-11-26 | 长安大学 | A kind of measuring method of loess self-collapsibility minimum air velocity |
| CN110514807A (en) * | 2019-08-02 | 2019-11-29 | 长安大学 | A kind of loess self-collapsibility quantity measuring method |
| CN110516322B (en) * | 2019-08-06 | 2023-02-28 | 湖北工业大学 | Method for predicting clay saturation nonlinear permeability coefficient under different hydraulic gradients |
-
2020
- 2020-01-22 CN CN202010073036.8A patent/CN111220792B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CN111220792A (en) | 2020-06-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Klute | Laboratory measurement of hydraulic conductivity of unsaturated soil | |
| CN206756653U (en) | Determine head and varying head soil permeability coefficient measure combination unit | |
| McCartney et al. | Centrifuge permeameter for unsaturated soils. II: Measurement of the hydraulic characteristics of an unsaturated clay | |
| CN107782640A (en) | The method that the aqueous uniformity detection of rock sample and diffusion coefficient calculating are carried out based on digital picture | |
| CN105297785B (en) | A kind of foundation detection means and its detection method | |
| CN111220792B (en) | Method for calculating infiltration depth of unsaturated loess water | |
| CN106501151A (en) | A kind of shale aperture measurement device and method based on imbibition and ion diffusion property | |
| CN109682850A (en) | A kind of online imbibition experiment nuclear magnetic resonance test device and experimental method | |
| CN203758882U (en) | Coarse particle soil penetration test device eliminating boundary effect | |
| CN204694602U (en) | A kind of measurement capillary soil water climbing height test unit | |
| Martins Reis et al. | Determination of the soil-water retention curve and the hydraulic conductivity function using a small centrifuge | |
| Rezzoug et al. | Scaling laws for centrifuge modeling of capillary rise in sandy soils | |
| Leong et al. | Volume change measurement of soil specimen in triaxial test | |
| Al-Madhhachi et al. | Measuring erodibility of cohesive soils using laboratory jet erosion tests | |
| CN107422142A (en) | Pressure method stirs current Simple speed measuring device and speed-measuring method | |
| CN110487701A (en) | Contaminants Transport determination method for parameter in a kind of soil body | |
| CN114324101B (en) | Infiltration consolidation device for measuring soil saturation and application method thereof | |
| CN206740493U (en) | A kind of adjustable thickness water-repellent paint sample preparation sampler | |
| CN115219371A (en) | Uniform flow scouring device for slope | |
| CN212082773U (en) | Soil body disintegration test equipment under simulated dynamic water condition | |
| CN112014288B (en) | Gas drive water permeability evaluation method, device and system | |
| Nakajima et al. | Centrifuge modeling of one-step outflow tests for unsaturated parameter estimations | |
| Padilla et al. | An automated triaxial testing device for unsaturated soils | |
| Su et al. | Estimation of the apparent permeability in the dynamic centrifuge tests | |
| CN115308110B (en) | Variable water head permeability coefficient determination method and device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20201229 Termination date: 20220122 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |