CN114624081B - Test method and device for testing influence of ferric oxide on yield stress of cohesive soil - Google Patents

Test method and device for testing influence of ferric oxide on yield stress of cohesive soil Download PDF

Info

Publication number
CN114624081B
CN114624081B CN202210245168.3A CN202210245168A CN114624081B CN 114624081 B CN114624081 B CN 114624081B CN 202210245168 A CN202210245168 A CN 202210245168A CN 114624081 B CN114624081 B CN 114624081B
Authority
CN
China
Prior art keywords
sample
test
yield stress
supporting rod
soil
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.)
Active
Application number
CN202210245168.3A
Other languages
Chinese (zh)
Other versions
CN114624081A (en
Inventor
张先伟
徐倚晴
刘新宇
王港
安然
陈成
马超
黎澄生
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wuhan Institute of Rock and Soil Mechanics of CAS
Original Assignee
Wuhan Institute of Rock and Soil Mechanics of CAS
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Wuhan Institute of Rock and Soil Mechanics of CAS filed Critical Wuhan Institute of Rock and Soil Mechanics of CAS
Priority to CN202210245168.3A priority Critical patent/CN114624081B/en
Publication of CN114624081A publication Critical patent/CN114624081A/en
Application granted granted Critical
Publication of CN114624081B publication Critical patent/CN114624081B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/34—Purifying; Cleaning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/06—Special adaptations of indicating or recording means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/14—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by dead weight, e.g. pendulum; generated by springs tension

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Molecular Biology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
  • Sampling And Sample Adjustment (AREA)

Abstract

The invention discloses a test method and a device for testing the influence of ferric oxide on cohesive soil yield stress, which comprises the following steps: (1) Preparing sodium dithionite-sodium citrate-sodium bicarbonate solution; (2) determining an initial pore ratio of the soil sample; (3) sample preparation and sample loading; 4) Leaching to remove ferric oxide; (5) compression test; (6) analyzing and calculating results; the chassis and the upper disc are respectively connected through a supporting rod, and the supporting rod and the chassis are fixed by bolts; test paper is respectively attached to the upper part and the lower part of the sample. And respectively placing water permeable stones on the upper part and the lower part of the ring cutter sample and the test paper. The water permeable stone is arranged on the upper part of the chassis, a cutting ring sample, test paper and the water permeable stone are arranged in the supporting rod, and the water permeable stone upper part is respectively connected with the porous water permeable plate and the fixed plate. The method has the advantages of simple operation, high reliability, no toxicity or harm and high data accuracy, and effectively solves the problems that the prior method can not remove ferric oxide aiming at an independent sample and simultaneously carry out compression test.

Description

Test method and device for testing influence of ferric oxide on yield stress of cohesive soil
Technical Field
The invention relates to the field of geotechnical tests, in particular to a test method for testing the influence of ferric oxide on yield stress of cohesive soil, and also relates to a test device for testing the influence of ferric oxide on the yield stress of cohesive soil.
Background
Iron oxide is the iron-containing oxide in the soil and its hydrate [ FeO (OH). NH 2 O ], which is one of the most common cementing materials in the soil. Due to the special nature of iron oxide, in an acidic environment, the edges of iron oxide carry positive charges, which attract negative charges on the surfaces of clay particles, which causes the cementation effect of the clay. Many researches show that a certain content of ferric oxide exists in a lot of laterite, sea clay, basalt and mudstone residual soil, the ferric oxide can enhance the agglomeration of the soil, improve the surface roughness of soil particles, improve the soil strength, reduce the compressibility of the soil and also improve the rigidity of the soil. Therefore, research on the influence of iron oxide in soil on the mechanical properties is an important point in current research on soil texture and soil mechanics.
The yield stress of the soil means that when the soil bears the action of external force and reaches the yield stress P p, the cementation in the soil starts to be broken, the ferric oxide cementation starts to be gradually lost, the strength of the soil is softened, and the deformation resistance is reduced, so that the accurate determination of the yield stress of the soil is important for understanding the strength and deformation mechanism of the soil. Although, current research has demonstrated that iron oxide content has a close effect on the magnitude of yield stress, the higher the iron oxide content, the more pronounced the cementation effect. However, no related studies have been made to provide a test method for quantitatively determining the effect of iron oxide on cohesive soil yield stress. Some studies (Luo Hongxi. Influence of free iron oxide on red clay engineering properties. Geotechnical mechanics, 1987,8 (2), 29-36; zhang Xianwei, kong Lingwei. Interaction of iron oxide colloid with clay mineral and influence on clay properties. Geotechnical engineering theory, 2014,36 (1), 65-74), although the influence of iron oxide on viscous clay physical and mechanical properties was proposed according to the comparison of physical and mechanical properties of samples before and after iron oxide removal, these methods have a certain error in the results of samples due to the fact that a soaking method is used in the sample preparation process and mechanical tests are performed again. In addition, some inventions propose methods for removing iron oxide from soil (such as a percolation device and method for removing free iron oxide from soil, application No. 202111239907. X), but these methods are only for removing iron oxide from soil, and there is no further disclosure of how to perform mechanical test on the iron oxide removed sample, and in particular, how to test the effect of iron oxide on yield stress.
To sum up: it can be found that the iron oxide has a significant effect on the physical and mechanical properties of the cohesive soil. The yield stress is an important parameter for representing the cementation effect of the cohesive soil ferric oxide, and how to quantitatively test the influence of the ferric oxide on the cohesive soil yield stress has important significance for knowing the strength and deformation mechanism of the soil and providing the cohesive soil improvement technology. A solution to this problem has been disclosed or patented by searching for a test device and method for testing the effect of iron oxide on cohesive soil yield stress that has not been discovered so far.
Disclosure of Invention
Based on the defects existing in the test method, the invention aims to provide the test method for testing the influence of the ferric oxide on the yield stress of the cohesive soil, which has the advantages of simple operation, high reliability, no toxicity and harm and high data accuracy, and effectively solves the problems that the prior method can not remove the ferric oxide aiming at an independent sample and simultaneously carry out the compression test. The principle of the technical scheme is that a sodium dithionite-sodium citrate-sodium bicarbonate solution (DCB solution for short) is adopted, a leaching action principle is utilized to remove ferric oxide in soil, a one-dimensional compression test is carried out after the ferric oxide is removed, a yield stress determination method is provided for a compression curve, the yield stress of the soil before and after the ferric oxide is removed is quantitatively calculated, the influence of the ferric oxide on the yield stress of cohesive soil is evaluated, and further the contribution of the ferric oxide to the soil mechanical property is determined.
Another object of the present invention is to provide a test device for testing the effect of iron oxide on the yield stress of cohesive soil, which has the advantages of easy assembly, easy use and maintenance, low cost, wide application, etc.
In order to achieve the above object, the present invention adopts the following technical measures:
A test method for testing influence of ferric oxide on yield stress of cohesive soil comprises the following steps:
(1) Sodium dithionite-sodium citrate-sodium bicarbonate solution (DCB solution) was prepared: fully mixing a sodium citrate solution with the concentration of 0.3mol/L, a saturated sodium chloride solution, a sodium bicarbonate solution with the concentration of 1mol/L and a sodium dithionite solution with the concentration of 0.1mol/L according to the ratio of 1:1:1 to prepare a DCB solution with the concentration of 1L.
(2) Determining the initial pore ratio of the soil sample: taking an undisturbed viscous soil block-shaped soil sample, and testing the density rho, the specific gravity G s and the water content w according to the geotechnical test method standard (GB/T50123-2019). According to the density ρ, specific gravity G s and water content w, the formula is adoptedThe initial porosity e 0 of the soil sample is calculated and determined.
Wherein: e 0 is the initial void ratio, ρ is the density, G s is the specific gravity, and w is the water content;
(3) Sample preparation and sample loading: cutting a ring cutter sample along the deposition direction of a block-shaped soil sample by using a ring cutter with the inner diameter of 61.8mm and the height of 20mm, respectively attaching a first test paper and a second test paper (purchased in the market) to the upper part and the lower part of the sample with the ring cutter, placing the sample on a second permeable stone, placing the sample into the first support rod and the second support rod and the upper part of a chassis, placing the first permeable stone on the upper part, and then placing the porous permeable plate. Wherein the porous water permeable plate is hollow, the upper end is closed, and the lower end is fully distributed with water permeable holes with the diameter of 1mm and the interval of 1 mm. Connecting a second pipeline with a porous water permeable plate, placing a fixed plate above the porous water permeable plate, aligning a displacement guide rod with the center of the fixed plate, erecting the bottom of a dial indicator on the fixed plate, placing an upper disc on the upper parts of the first support rod and the first support rod, screwing and fixing the upper disc by using a first bolt and a third bolt, screwing and fixing a chassis by using a second bolt and a fourth bolt d, horizontally placing an L-shaped support rod above the displacement guide rod, adjusting the positions of the support and the fixed base, enabling the L-shaped support rod to be horizontal in an empty state, and connecting the chassis with a filtrate receiving barrel by using the first pipeline.
(4) Leaching to remove ferric oxide: pouring the prepared sodium dithionite-sodium citrate-sodium bicarbonate solution (DCB solution) into a water storage barrel, sequentially opening a first valve, a second valve and a third valve, opening an air compressor to enable the air compressor to inject air into the water storage barrel, observing a pressure gauge to adjust the air compressor to enable the air compressor to provide the pressure to be about 100kPa, injecting the DCB solution into a sample through sequentially passing through a second pipeline and a porous water permeable plate, enabling filtrate after chemical reaction between the DCB solution and the sample to flow into a filtrate receiving barrel through the first pipeline, taking out filtrate in the filtrate receiving barrel every day, testing the content of ferric oxide in the filtrate according to the method in the geotechnical test method standard (GB/T50123-2019), and closing the air compressor, the first valve, the second valve and the third valve when the content of ferric oxide is lower than 0.01%, and stopping leaching test.
(5) Compression test: the dial indicator is cleared, weights are added on the tray, and the test is sequentially and gradually carried out until the test is finished according to the pressurizing conditions that the loading pressures of the first level to the ninth level are 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa and 3200kPa respectively. Repeating the step (3) for one time, and carrying out compression test on the non-removed ferric oxide sample under the same loading condition without opening the air compressor, the first valve, the second valve and the third valve.
(6) Result analysis and calculation: the void ratio e i of the sample under each stage of pressure is calculated, and the calculation formula is e i＝e0-(1+e0)×Si/(S1i-S0i), wherein e 0 is the initial void ratio of the soil sample, S i is the accumulated deformation of the sample under the loading pressures of the first stage to the ninth stage, S 1i is the final reading of the dial indicator under the loading pressures of the first stage to the ninth stage, and S 0i is the initial reading of the dial indicator under the loading pressures of the first stage to the ninth stage. Drawing a relation curve of the void ratio e i and the LogP according to the calculated void ratio e i of the sample under each level of pressure and the corresponding loading pressure P, finding out the curvature maximum point of the relation curve of e i and the LogP, and drawing a vertical line downwards, wherein the intersection point of the vertical line and the abscissa is the yield stress P P. And processing and analyzing compression test results of the iron oxide-removed sample and the non-iron oxide-removed sample to obtain corresponding yield stresses P P( Front part ) and P P( Rear part (S) ) respectively. The ratio of P P( Front part ) of the sample before removing the ferric oxide to P P( Rear part (S) ) of the sample after removing the ferric oxide is defined as a yield stress ratio f (f=P P( Front part )/PP( Rear part (S) )), the effect of the ferric oxide of the cohesive soil on the yield stress is compared by using the yield stress ratio f, and the larger the yield stress ratio f, the more obvious the effect of the ferric oxide in the soil on the mechanical property is shown. The yield stress ratio f=1 represents that the iron oxide has no effect on the yield stress of the cohesive soil, the yield stress ratio f is between 1 and 5 represents that the iron oxide has an effect on the yield stress of the cohesive soil, and the yield stress ratio f >5 represents that the iron oxide has a significant effect on the yield stress of the cohesive soil.
In the above method for testing the effect of iron oxide on cohesive soil yield stress, preferably, the pressure provided by the air compressor in step (4) should be 100kPa.
In the above method for testing the effect of iron oxide on cohesive soil yield stress, preferably, the frequency of performing iron oxide test on the filtrate in the filtrate receiving tank in the step (4) should be 1/7 days.
In the above method for testing the effect of iron oxide on cohesive soil yield stress, preferably, the loading stress level in step (5) should be 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa, 3200kPa.
The most critical step of the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil is the step (4). Unlike the soaking method (Luo Hongxi. Influence of free iron oxide on engineering properties of red clay. Geotechnical mechanics, 1987,8 (2), 29-36) and filtration methods (Zhang Xianwei, kong Lingwei. Interaction of iron oxide colloid with clay mineral and influence on clay properties. Geotechnical engineering journal, 2014,36 (1), 65-74), step (4) uses leaching with DCB solution to remove iron oxide from the sample. The soaking method has no restriction of a cutting ring, so that the cementing effect of the ferric oxide is lost, the soaked sample cannot be prepared into a standard cutting ring sample, the influence of the ferric oxide on the yield stress of the cohesive soil cannot be further evaluated, and the method takes a long time; although the filtering method can remove ferric oxide under the limit of a cutting ring, the prepared sample needs to be loaded on a compression instrument again, the sample disturbance caused by manual operation cannot be avoided in the sample loading process, the reliability of the test is reduced, and the data error is large. The invention can finish the sample preparation and sample loading processes on the compression device at one time, and the DCB solution is injected into the soil sample through the pressure (namely, hydraulic gradient) provided by the air compressor, so that compared with the prior art, the invention saves test time, reduces the soil sample quality consumption, and more importantly, the iron oxide-removed sample does not need to be reloaded, reduces the interference of artificial influence, improves the accuracy of test results, and can ensure that the influence of the iron oxide on the yield stress of the cohesive soil is accurately measured.
The method for testing the influence of iron oxide on the yield stress of cohesive soil is utilized to respectively test and verify red clay formed by weathering and cohesive soil formed by deposition, and the test scheme adopts two samples to test and compare the results by using the method and the prior method, wherein the prior method is a soaking method (Luo Hongxi. Influence of free iron oxide on engineering properties of red clay. Geotechnical mechanics, 1987,8 (2) and 29-36), and the prior method is a filtering method (Zhang Xianwei, kong Lingwei. Interaction of iron oxide colloid and clay mineral and influence of the interaction on clay mineral. Geotechnical engineering theory, 2014,36 (1) and 65-74). The result shows that in the sample adopting the previous method I (soaking method), the soil sample after soaking is loose, the cementing effect of the ferric oxide is improved artificially in the compression test, the yield stress ratio f is higher, and compared with the result obtained by the method, the error of the soaking method reaches 19.06% -20.39%; in the prior art, the second method (filtering method) needs to reload the sample, the cementing effect of the ferric oxide is reduced artificially in the compression test, and the yield stress ratio f is lower, so that compared with the result obtained by the method, the error of the filtering method reaches 5.88-14.92%. Therefore, the test result shows that the technical effect of the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil is verified, and the influence of the ferric oxide on the yield stress of the cohesive soil can be accurately tested by one-time sample preparation and sample loading on the premise of effectively removing the ferric oxide without being interfered by human factors.
A test apparatus for testing the effect of iron oxide on cohesive soil yield stress comprising: chassis, upper disc, first branch, second branch, porous water-permeable plate, first water-permeable stone, second water-permeable stone, cutting ring, sample, first bolt, second bolt, third bolt, fourth bolt, fixed plate, displacement guide arm, L branch, tray, weight, first pipeline, second pipeline, third pipeline, first valve, second valve, third valve, water storage bucket, manometer, air compressor, filtrate receiving bucket, percentage table, support, unable adjustment base, first test paper, second test paper. The method is characterized in that: the chassis and the upper disc are respectively connected through a first supporting rod and a second supporting rod, wherein the first supporting rod and the upper disc are fixed by a first bolt; the first support rod and the chassis are fixed by a second bolt; the second supporting rod and the upper disc are fixed by a third bolt; the second support rod and the chassis are fixed by a fourth bolt. The first test paper and the second test paper are respectively attached to the upper part and the lower part of the sample in the ring cutter. And respectively placing a first water-permeable stone and a second water-permeable stone on the upper part and the lower part of the ring cutter, the sample, the first test paper and the second test paper. The second permeable stone is placed on the upper portion of the chassis, a cutting ring, a sample, first test paper, second test paper, first permeable stone and second permeable stone are placed in the first support rod and the second support rod, and the upper portions of the first permeable stone are respectively connected with the porous permeable plates and the fixed plates. The dial indicator is vertically arranged on the fixed plate, meanwhile, the upper part of the center of the fixed plate is connected with the displacement guide rod, the displacement guide rod penetrates through the center of the upper disc, the displacement guide rod is vertically connected with the L-shaped supporting rod, the right end of the L-shaped supporting rod is connected with the tray, weights are placed on the upper part of the tray when a compression test is carried out, and the left end of the L-shaped supporting rod is connected with the fixed base through the bracket. Wherein the porous water permeable plate is hollow, the upper end is closed, and the lower end is covered with water permeable holes with 1mm spacing and 1mm diameter. The dial indicator is vertically erected on the fixed plate, meanwhile, the upper center portion of the fixed plate is connected with the displacement guide rod, the displacement guide rod penetrates through the center of the upper disc and is vertically connected with the L-shaped supporting rod, the right end of the L-shaped supporting rod is connected with the tray, weights are placed on the upper portion of the tray when a compression test is carried out, and the left end of the L-shaped supporting rod is connected with the fixed base through the bracket. One end of a first pipeline with a first valve is connected with the center position of the lower part of the chassis, and the other end of the first pipeline is connected with a filtrate receiving barrel. One end of a second pipeline with a second valve is connected with the porous water permeable plate, and the other end of the second pipeline is connected with a water storage barrel containing solution. The upper part of the water storage barrel is connected with a pressure gauge and a third pipeline with a third valve, and the other end of the third pipeline is connected with an air compressor.
In the test device for testing the influence of the ferric oxide on the yield stress of the cohesive soil, preferably, the porous water permeable plate is hollow, the upper end is closed, and the lower end is provided with water permeable holes with the interval of 1mm and the diameter of 1mm.
In the test device for testing the influence of the ferric oxide on the yield stress of the cohesive soil, the precision of the dial indicator is preferably 0.01mm, and the measuring range is more than 15mm.
In the test apparatus for testing the effect of iron oxide on cohesive soil yield stress described above, the filtrate receiving tank should preferably be glass making.
In a test device for testing the influence of ferric oxide on the yield stress of cohesive soil, a porous water permeable plate and a filtrate receiving barrel are key components. The upper end of the porous water permeable plate is closed, the lower end of the porous water permeable plate is provided with a small hole which can enable DCB filtrate to ooze out, and DCB solution can be stably pressed into a soil sample under the pressure provided by an air compressor, so that the purpose of removing ferric oxide by utilizing the leaching effect is realized. The filtrate receiving barrel can safely receive filtrate, and the filtrate can be used for testing the content of ferric oxide, so that the effect of removing the ferric oxide from the DCB solution is determined, and accurate information is provided for determining when to perform a compression test.
Compared with the prior art, the invention has the following advantages and effects:
1. The principle is simple and easy to understand, and the operator can conveniently get on hand. Compared with the traditional soaking method and filtering method, the method utilizes the leaching effect to remove the ferric oxide in the soil, has clear principle and does not need special training in the test operation process.
2. The test time is obviously shortened. Compared with the traditional soaking method and filtering method, the hydraulic gradient of leaching the DCB solution is adopted, so that the removal rate of ferric oxide is improved, the test time is shortened, and the working efficiency is improved.
3. The accuracy of the data is improved. Because the disposable sample preparation and sample filling are adopted, the interference of human factors is reduced, the error of the result is reduced, and the accuracy of the data is improved.
4. The test cost is low. The prepared DCB solution adopts a common commercial reagent, the price is low, the related test device can be repeatedly used, and the cost of the test is saved.
5. No environmental pollution and high safety. The filtrate recovery device is adopted, so that the environment is not polluted, and the used chemical reagent is non-corrosive, non-toxic and harmless, and ensures the safety of test personnel.
Drawings
FIG. 1 is a flow chart of a method for testing the effect of iron oxide on cohesive soil yield stress.
FIG. 2 is a schematic structural diagram of a test apparatus for testing the effect of iron oxide on cohesive soil yield stress.
FIG. 3 is a schematic view of the lower portion of a porous water permeable plate in a test apparatus for testing the effect of iron oxide on cohesive soil yield stress.
FIG. 4 is a graphical representation of the results of the test of example 2 and the results of the yield stress obtained by a method for testing the effect of iron oxide on cohesive soil yield stress.
FIG. 5 is a graphical representation of the results of the test of example 3 and the results of the yield stress obtained by a method for testing the effect of iron oxide on cohesive soil yield stress.
FIG. 6 is a graph showing a comparison of the yield stress ratio of the red clay of example 2 obtained by a method for testing the effect of iron oxide on the yield stress of cohesive soil and a method for the prior art (soaking method) and a method for the prior art (filtering method).
FIG. 7 is a graph showing a comparison of the effect of iron oxide on cohesive soil yield stress and the ratio of cohesive soil yield stress obtained in example 3 obtained in the first prior art method (soaking) and in the second prior art method (filtration).
FIG. 8 is a graph showing a comparison of the time duration required for testing the laterite clay of example 2, using one method of testing the effect of iron oxide on the yield stress of the clay, and using one conventional method (soaking) and two conventional methods (filtration).
FIG. 9 is a schematic diagram showing a comparison of the time period required for testing the cohesive soil of example 3, by a method of testing the effect of iron oxide on cohesive soil yield stress and by a first conventional method (soaking method) and a second conventional method (filtration method).
FIG. 10 is a graph showing a comparison of the quality of the consumed soil samples from the test of the red clay of example 2 using a method for testing the effect of iron oxide on cohesive soil yield stress and a first conventional method (soaking method) and a second conventional method (filtration method).
FIG. 11 is a schematic diagram showing a comparison of the effect of iron oxide on cohesive soil yield stress and the quality of the soil sample consumed in the test of cohesive soil of example 3 by the first conventional method (soaking) and the second conventional method (filtration).
Wherein: 1-chassis, 2-upper plate, 3 a-first support rod, 3 b-second support rod, 4-porous water permeable plate, 5 a-first water permeable stone, 5 b-second water permeable stone, 6-ring knife, 7-sample, 8 a-first bolt, 8 b-second bolt, 8c third bolt, 8 d-fourth bolt, 9-fixed plate, 10-displacement guide rod, 11-L-shaped support rod, 12-tray, 13 a-first weight, 13 b-second weight, 13 c-third weight, 14 a-first pipeline, 14 b-second pipeline, 14 c-third pipeline, 15 a-first valve, 15 b-second valve, 15 c-third valve, 16-water storage bucket, 17-pressure gauge, 18-air compressor, 19-filtrate receiving bucket, 20-dial gauge, 21-bracket, 22-fixed base, 23 a-first, 23 b-second test paper, 24-water permeable hole test paper.
Detailed Description
The following describes in detail a test apparatus and a method for testing the effect of iron oxide on cohesive soil yield stress in one of three embodiments and two comparative tests according to the present invention with reference to the accompanying drawings.
Example 1:
According to the figures 1 and 2, a test device for testing the effect of ferric oxide on the yield stress of cohesive soil comprises: the device comprises a chassis 1, an upper disc 2, a first supporting rod 3a, a second supporting rod 3b, a porous water permeable plate 4, a first water permeable stone 5a, a second water permeable stone 5b, a cutting ring 6, a sample 7, a first bolt 8a, a second bolt 8b, a third bolt 8c, a fourth bolt 8d, a fixed plate 9, a displacement guide rod 10, an L-shaped supporting rod 11, a tray 12, weights 13, a first pipeline 14a, a second pipeline 14b, a third pipeline 14c, a first valve 15a, a second valve 15b, a third valve 15c, a water storage bucket 16, a pressure gauge 17, an air compressor 18, a filtrate receiving bucket 19, a dial indicator 20, a bracket 21, a fixed base 22, a first test paper 23a and a second test paper 23b. The novel multifunctional electric bicycle is characterized in that the chassis 1 and the upper disc 2 are respectively connected through a first supporting rod 3a and a second supporting rod 3b, wherein the first supporting rod 3a and the upper disc 2 are fixed by a first bolt 8 a; the first support rod 3a and the chassis 1 are fixed by a second bolt 8 b; the second strut 3b and the upper disc 2 are fixed by a third bolt 8 c; the second strut 3b and the chassis 1 are secured by a fourth bolt 8 d. The first test paper 23a and the second test paper 23b are respectively attached to the upper and lower portions of the sample 7 in the ring cutter 6. A first water permeable stone 5a and a second water permeable stone 5b are respectively placed on the upper part and the lower part of the ring cutter 6, the sample 7, the first test paper 23a and the second test paper 23b. The second permeable stone 5b is placed on the upper portion of the chassis 1, and the cutting ring 6, the sample 7, the first test paper 23a, the second test paper 23b, the first permeable stone 5a and the second permeable stone 5b are placed inside the first supporting rod 3a and the second supporting rod 3b. The upper part of the first permeable stone 5a is respectively connected with the porous permeable plate 4 and the fixed plate 9. The dial indicator 20 is vertically arranged on the fixed plate 9, meanwhile, the upper part of the center of the fixed plate 9 is connected with the displacement guide rod 10, the displacement guide rod 10 passes through the center of the upper disc 2, the displacement guide rod 10 is vertically connected with the L-shaped supporting rod 11, the right end of the L-shaped supporting rod 11 is connected with the tray 12, the weight 13 is placed on the upper part of the tray 12 when a compression test is carried out, and the left end of the L-shaped supporting rod 11 is connected with the fixed base 22 through the bracket 21. The first valve 15a is connected to the chassis 1 (lower center position) and the first pipe 14a, and the first pipe 14a is connected to the receiving tub 19. The third pipeline 14c is respectively connected with a third valve 15c and an air compressor 18, the second valve 15b is respectively connected with the porous water permeable plate 4 and the second pipeline 14b, the second pipeline 14b is connected with the water storage barrel 16, and the inside of the water storage barrel 16 contains DCB solution. The upper part of the water storage barrel 16 is provided with a pressure gauge 17, the third valve 15c is respectively connected with the water storage barrel 16 and the third pipeline 14c, and the third pipeline 14c is connected with an air compressor 18.
The porous water permeable plate 4 is hollow, the upper end is closed, and the lower end is provided with water permeable holes 24 with the diameter of 1mm and the distance of 1 mm.
The precision of the dial indicator 20 should be 0.01mm and the measuring range exceeds 15mm.
The filtrate receiving drum 19 should be glass made.
When the test device for testing the influence of ferric oxide on the yield stress of cohesive soil works, based on the characteristics that the upper end of the porous water permeable plate 4 is closed, and the lower end of the porous water permeable plate is provided with water permeable holes 24 which can enable DCB filtrate to exude, a DCB solution can be stably pressed into the sample 7 under the pressure provided by the air compressor 18, and the ferric oxide in the sample 7 is removed by utilizing the principle of leaching. After the DCB filtrate is used, the DCB filtrate is received by the filtrate receiving barrel 19, so that the safety of the test is ensured. The iron oxide content was tested by using the filtrate after use, and thus the effect of DCB solution to remove iron oxide was determined. The sample 7 after iron oxide removal is not required to be taken out, a weight 13 is placed on the tray 12, the pressure is directly loaded on the sample 7 through the L-shaped supporting rod 11 and the displacement guide rod 10, the compression test result of the sample 7 is obtained by utilizing the reading of the dial indicator 20, the disturbance generated by resampling and sample loading is successfully avoided, the test is greatly simplified, and compared with the prior method, the test time which is not equal by 35.7-56.25% is saved; the mass consumption of the soil sample is reduced by 52.0-62.5%; and ensuring that the iron oxide content in the test sample is extremely low (less than 0.01%); in addition, the error of 19.06% -20.39% higher than the soaking method and 5.88% -14.92% lower than the filtering method is eliminated, so that the accuracy of the compression test result of the iron oxide removal sample is ensured.
Example 2:
Example 2 was performed with Guangxi red clay, which contained 4.5% -7.8% iron oxide. The test device and the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil are adopted to remove the ferric oxide from Guangxi red clay and perform compression test to determine the influence of the yield stress of the ferric oxide.
According to FIG. 1, a test method for testing the effect of iron oxide on cohesive soil yield stress is shown as follows:
(1) Sodium dithionite-sodium citrate-sodium bicarbonate solution (DCB solution) was prepared: fully mixing a sodium citrate solution with the concentration of 0.3mol/L, a saturated sodium chloride solution, a sodium bicarbonate solution with the concentration of 1mol/L and a sodium dithionite solution with the concentration of 0.1mol/L according to the ratio of 1:1:1 to prepare a DCB solution with the concentration of 1L.
(2) Determining the initial pore ratio of the soil sample: and taking an undisturbed red clay block sample, and testing the density rho, the specific gravity G s and the water content w according to the geotechnical test method standard (GB/T50123-2019). According to the density ρ, specific gravity G s and water content w, the formula is adoptedThe initial porosity e 0 of the soil sample is calculated and determined.
Wherein: e 0 is the initial void ratio, ρ is the density, G s is the specific gravity, and w is the water content;
(3) Sample preparation and sample loading: cutting a ring cutter 7 along the deposition direction of a block-shaped soil sample by using a ring cutter 6 with the inner diameter of 61.8mm and the height of 20mm, respectively attaching a first test paper 23a and a second test paper 23b to the upper part and the lower part of the sample 7 with the ring cutter 6, placing the first test paper and the second test paper on a second permeable stone 5b, placing the first permeable stone 5a and the second permeable stone 3b in the first support rod and the second support rod, and placing the porous permeable plate 4 in the upper part of the chassis 1. Wherein the porous water permeable plate 4 is hollow, the upper end is closed, and the lower end is covered with water permeable holes 24 with the diameter of 1mm and the interval of 1 mm. The second pipeline 14b is connected with the porous water permeable plate 4, the fixed plate 9 is placed above the porous water permeable plate 4, the displacement guide rod 10 is aligned with the center of the fixed plate 9, the bottom of the dial indicator 20 is erected on the fixed plate 9, the upper disc 2 is placed on the upper parts of the first supporting rod 3a and the first supporting rod 3b and screwed and fixed by the first bolt 8a and the third bolt 8c, the chassis 1 is screwed and fixed by the second bolt 8b and the fourth bolt 8d, the L-shaped supporting rod 11 is horizontally placed above the displacement guide rod 10, the positions of the bracket 25 and the fixed base 26 are adjusted, the L-shaped supporting rod 11 is positioned horizontally in an empty state of the tray 12, and the chassis 1 is connected with the filtrate receiving barrel 19 by the first pipeline 14 a.
(4) Leaching to remove ferric oxide: pouring the prepared DCB solution into a water storage barrel 16, sequentially opening a first valve 15a, a second valve 15b and a third valve 15c, opening an air compressor 18 to enable the air compressor 18 to inject air into the water storage barrel 16, observing a pressure gauge 17 to adjust the air compressor 18 to enable the air compressor 18 to provide the pressure to be 100kPa, sequentially injecting the DCB solution into a sample 7 through a second pipeline 14b and a porous water permeable plate 4, enabling filtrate after chemical reaction between the DCB solution and the sample 7 to flow into a filtrate receiving barrel 19 through the first pipeline 14a, taking out filtrate in the filtrate receiving barrel 19 every 7 days, testing the content of ferric oxide in the filtrate according to the method in the geotechnical test method standard (GB/T50123-2019), closing the air compressor 18, closing the first valve 15a, the second valve 15b and the third valve 15c when the content of ferric oxide is lower than 0.1%, and stopping leaching test.
(5) Compression test: the dial indicator 20 was cleared, weights 13 were added to the tray 12, and the test was successively carried out stepwise until the test was completed under the pressurizing conditions that the loading pressures of the first to ninth stages were 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa, 3200kPa, respectively. And (3) repeating the step (3) once, and not opening the air compressor 18, the first valve 15a, the second valve 15b and the third valve 15c, and performing a compression test on the non-removed ferric oxide sample under the same loading condition.
(6) Result analysis and calculation: the void ratio e i of the sample under each stage of pressure is calculated, and the calculation formula is e i＝e0-(1+e0)×Si/(S1i-S0i), wherein e 0 is the initial void ratio of the soil sample, S i is the accumulated deformation of the sample under the loading pressures of the first stage to the ninth stage, S 1i is the final reading of the dial indicator 20 under the loading pressures of the first stage to the ninth stage, and S 0i is the initial reading of the dial indicator 20 under the loading pressures of the first stage to the ninth stage. Drawing a relation curve of the void ratio e i and the LogP according to the calculated void ratio e i of the sample under each level of pressure and the corresponding loading pressure P, finding out the curvature maximum point of the relation curve of e i and the LogP, and drawing a vertical line downwards, wherein the intersection point of the vertical line and the abscissa is the yield stress P P. And processing and analyzing compression test results of the iron oxide-removed sample and the non-iron oxide-removed sample to obtain corresponding yield stresses P P( Front part ) and P P( Rear part (S) ) respectively. The ratio of P P( Front part ) of the sample before removing the ferric oxide to P P( Rear part (S) ) of the sample after removing the ferric oxide is defined as a yield stress ratio f (f=P P( Front part )/PP( Rear part (S) )), the effect of the ferric oxide of the cohesive soil on the yield stress is compared by using the yield stress ratio f, and the larger the yield stress ratio f, the more obvious the effect of the ferric oxide in the soil on the mechanical property is shown. The yield stress ratio f=1 represents that the iron oxide has no effect on the yield stress of the cohesive soil, the yield stress ratio f is between 1 and 5 represents that the iron oxide has an effect on the yield stress of the cohesive soil, and the yield stress ratio f >5 represents that the iron oxide has a significant effect on the yield stress of the cohesive soil.
The test results of example 2 are shown in fig. 4, and fig. 4 depicts compression curves of natural red clay and red clay after removal of iron oxide, and by the step (6), P P( Front part ) of the sample before removal of iron oxide and P P( Rear part (S) ) of the sample after removal of iron oxide are 425kPa and 200kPa respectively, and the yield stress ratio f is 2.125, which represents that iron oxide in guangxi red clay has an effect on the yield stress. According to the previous study (Zhang Xianwei, kong Lingwei, wang Jing. SEM-EDS test study on cohesive soil colloid binding characteristics. Geotechnical mechanics, 2013,34 (journal 2): 195-203), this value can reasonably describe the strength of the sample after removal of iron oxide, accurately reflect the effect of iron oxide on the yield stress of red clay. Taking out the red clay sample after the test in the example 2, and determining the content of ferric oxide according to the guidance of the standard of geotechnical test method (GB/T50123-2019), wherein the content of residual ferric oxide is less than 0.01%. Therefore, the test device and the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil, provided by the invention, have good technical effect on removing the ferric oxide, accurate compression test result and can reasonably evaluate the influence of the ferric oxide on the yield stress of the cohesive soil. As shown in fig. 8 and 9, the test accumulation period required in example 2 was 45 days, and the mass of the soil sample consumed was 120g.
Example 3:
Example 3 was performed with a clay soil from Guangdong, which contained 3.6% -5.9% iron oxide. The test device and the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil are adopted to remove the ferric oxide from the cohesive soil in Guangdong and perform compression test to determine the influence of the yield stress of the ferric oxide, and the test method for testing the influence of the ferric oxide on the yield stress of the cohesive soil comprises the following steps:
(1) Sodium dithionite-sodium citrate-sodium bicarbonate solution (DCB solution) was prepared: fully mixing a sodium citrate solution with the concentration of 0.3mol/L, a saturated sodium chloride solution, a sodium bicarbonate solution with the concentration of 1mol/L and a sodium dithionite solution with the concentration of 0.1mol/L according to the ratio of 1:1:1 to prepare a DCB solution with the concentration of 1L.
(2) Determining the initial pore ratio of the soil sample: and taking an undisturbed cohesive soil block sample, and testing the density rho, the specific gravity G s and the water content w according to the geotechnical test method standard (GB/T50123-2019). According to the density ρ, specific gravity G s and water content w, the formula is adoptedThe initial porosity e 0 of the soil sample is calculated and determined.
Wherein: e 0 is the initial void ratio, ρ is the density, G s is the specific gravity, and w is the water content
(3) Sample preparation and sample loading: cutting a ring cutter 7 along the deposition direction of a block-shaped soil sample by using a ring cutter 6 with the inner diameter of 61.8mm and the height of 20mm, respectively attaching a first test paper 23a and a second test paper 23b to the upper part and the lower part of the sample 7 with the ring cutter 6, placing the first test paper and the second test paper on a second permeable stone 5b, placing the first permeable stone 5a and the second permeable stone 3b in the first support rod and the second support rod, and placing the porous permeable plate 4 in the upper part of the chassis 1. Wherein the porous water permeable plate 4 is hollow, the upper end is closed, and the lower end is covered with water permeable holes 24 with the diameter of 1mm and the interval of 1 mm. The second pipeline 14b is connected with the porous water permeable plate 4, the fixed plate 9 is placed above the porous water permeable plate 4, the displacement guide rod 10 is aligned with the center of the fixed plate 9, the bottom of the dial indicator 20 is erected on the fixed plate 9, the upper disc 2 is placed on the upper parts of the first supporting rod 3a and the first supporting rod 3b and screwed and fixed by the first bolt 8a and the third bolt 8c, the chassis 1 is screwed and fixed by the second bolt 8b and the fourth bolt 8d, the L-shaped supporting rod 11 is horizontally placed above the displacement guide rod 10, the positions of the bracket 25 and the fixed base 26 are adjusted, the L-shaped supporting rod 11 is positioned horizontally in an empty state of the tray 12, and the chassis 1 is connected with the filtrate receiving barrel 19 by the first pipeline 14 a.
(4) Leaching to remove ferric oxide: pouring the prepared DCB solution into a water storage barrel 16, sequentially opening a first valve 15a, a second valve 15b and a third valve 15c, opening an air compressor 18 to enable the air compressor 18 to inject air into the water storage barrel 16, observing a pressure gauge 17 to adjust the air compressor 18 to enable the air compressor 18 to provide the pressure to be 100kPa, sequentially injecting the DCB solution into a sample 7 through a second pipeline 14b and a porous water permeable plate 4, enabling filtrate after chemical reaction between the DCB solution and the sample 7 to flow into a filtrate receiving barrel 19 through the first pipeline 14a, taking out filtrate in the filtrate receiving barrel 19 every 7 days, testing the content of ferric oxide in the filtrate according to the method in the geotechnical test method standard (GB/T50123-2019), closing the air compressor 18, closing the first valve 15a, the second valve 15b and the third valve 15c when the content of ferric oxide is lower than 0.1%, and stopping leaching test.
(5) Compression test: the dial indicator 20 was cleared, weights 13 were added to the tray 12, and the test was successively carried out stepwise until the test was completed under the pressurizing conditions that the loading pressures of the first to ninth stages were 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa, 3200kPa, respectively. And (3) repeating the step (3) once, and not opening the air compressor 18, the first valve 15a, the second valve 15b and the third valve 15c, and performing a compression test on the non-removed ferric oxide sample under the same loading condition.
(6) Result analysis and calculation: the void ratio e i of the sample under each stage of pressure is calculated, and the calculation formula is e i＝e0-(1+e0)×Si/(S1i-S0i), wherein e 0 is the initial void ratio of the soil sample, S i is the accumulated deformation of the sample under the loading pressures of the first stage to the ninth stage, S 1i is the final reading of the dial indicator 20 under the loading pressures of the first stage to the ninth stage, and S 0i is the initial reading of the dial indicator 20 under the loading pressures of the first stage to the ninth stage. Drawing a relation curve of the void ratio e i and the LogP according to the calculated void ratio e i of the sample under each level of pressure and the corresponding loading pressure P, finding out the curvature maximum point of the relation curve of e i and the LogP, and drawing a vertical line downwards, wherein the intersection point of the vertical line and the abscissa is the yield stress P P. And processing and analyzing compression test results of the iron oxide-removed sample and the non-iron oxide-removed sample to obtain corresponding yield stresses P P( Front part ) and P P( Rear part (S) ) respectively. The ratio of P P( Front part ) of the sample before removing the ferric oxide to P P( Rear part (S) ) of the sample after removing the ferric oxide is defined as a yield stress ratio f (f=P P( Front part )/PP( Rear part (S) )), the effect of the ferric oxide of the cohesive soil on the yield stress is compared by using the yield stress ratio f, and the larger the yield stress ratio f, the more obvious the effect of the ferric oxide in the soil on the mechanical property is shown. The yield stress ratio f=1 represents that the iron oxide has no effect on the yield stress of the cohesive soil, the yield stress ratio f is between 1 and 5 represents that the iron oxide has an effect on the yield stress of the cohesive soil, and the yield stress ratio f >5 represents that the iron oxide has a significant effect on the yield stress of the cohesive soil.
The test results of example 3 are shown in fig. 5, and the compression curves of the natural cohesive soil and the cohesive soil after removal of the ferric oxide are shown in fig. 5, and by the step (6), the P P( Front part ) of the sample before removal of the ferric oxide and the P P( Rear part (S) ) of the sample after removal of the ferric oxide are obtained to be 335kPa and 190kPa respectively, and the yield stress ratio f is 1.763, which represents that the ferric oxide in the cohesive soil in Guangdong has an effect on the yield stress. The value can reasonably describe the strength of the sample after the iron oxide is removed, and the influence of the iron oxide on the yield stress of the red clay is obtained. Taking out the cohesive soil sample after the test of the example 3, and measuring the content of ferric oxide according to the guidance of the standard geotechnical test method standard (GB/T50123-2019), wherein the content of residual ferric oxide is measured to be less than 0.01 percent. Therefore, the test device and the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil, provided by the invention, have good technical effect on removing the ferric oxide, accurate compression test result and can reasonably evaluate the influence of the ferric oxide on the yield stress of the cohesive soil. As shown in fig. 10 and 11, the test duration required for the present example 3 was 35 days, and the mass of the soil sample consumed was 120g.
Comparative test 1:
in order to compare the test device and method for testing the influence of ferric oxide on the yield stress of cohesive soil, the content degree of ferric oxide removed by the prior method and the measured influence of the yield stress of cohesive soil, the test device and method for testing the influence of ferric oxide on cohesive soil, which is provided by the invention, are adopted in the comparative test 1, the Guangxi red clay in the example 2 is tested by adopting the prior method I (soaking method) and the prior method II (filtering method), and the content of ferric oxide in the soil sample is 4.5% -7.8%. Wherein the steps of the prior method I (soaking method) and the prior method II (filtering method) are as follows:
(1) The prior method one (soaking method) comprises the following steps: cutting the ring cutter sample along the deposition direction of the red clay sample by using a ring cutter with the inner diameter of 61.8mm and the height of 20mm, immersing the ring cutter sample by using 0.05mol/L sodium dithionite solution, and carrying out long-term permeation on the sample. Taking out a sample, and measuring the content of ferric oxide according to the guidance of a standard geotechnical test method standard (GB/T50123-2019), wherein the content of residual ferric oxide is measured to be 0.05%; since the soil sample after soaking was loose and not molded by the soaking method, the soil sample was put into a constant temperature oven at 105℃for 24 hours and dried, and then a ring-cut remolded sample having an inner diameter of 61.8mm and a height of 20mm was prepared, and compression test was performed under nine-stage loading conditions (12.5 kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa, 3200 kPa) in accordance with the instructions of the Specification of the geotechnical test method Standard (GB/T50123-2019), respectively.
(2) Step two (filtration method) of the prior method: cutting a ring cutter sample along the deposition direction of the red clay sample by using a ring cutter with the inner diameter of 61.8mm and the height of 20mm, selecting an iron oxide colloid removal solution as a penetrating fluid, and removing iron oxide by using a flexible wall penetration test system (PN 3230M type). The flexible wall permeation test system had a permeation confining pressure of 100kPa, a back pressure of 75kPa, and after the back pressure was saturated for 3 days, the permeation time was 30 days by increasing the bottom pressure of the sample to 90kPa and conducting the dissolution permeation of the iron oxide colloid by permeating the liquid through the sample from below under a permeation pressure of 15 kPa. After the infiltration is finished, the content of residual ferric oxide in the soil sample is measured to be 0.03%; the sample after iron oxide removal obtained by filtration was placed in a standard consolidation apparatus, and compression test was performed under nine-stage loading conditions (12.5 kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa, 3200 kPa) in accordance with the instructions of the standard geotechnical test method standard (GB/T50123-2019), which was the same as that of example 2.
Fig. 6 shows the results of a test apparatus and method for testing the effect of iron oxide on cohesive soil yield stress using the present invention, as well as the results of a previous method one (soaking method) and a previous method two (filtration method) in terms of yield stress ratio. The Guangxi red clay in the embodiment 2 is tested by adopting the first conventional method (soaking method), the yield stress ratio f of the obtained result is 2.530, and compared with the result of the invention, the yield stress ratio f of the obtained result is 2.125, the obtained result shows higher, and the soaked soil sample is loose, the cementing effect of the ferric oxide is improved by the equivalent of man-made during the compression test, so the yield stress ratio f is higher; the yield stress ratio f of the result obtained by the prior method II (filtering method) is 2.000, and is lower than the yield stress ratio f of the result of the invention which is 2.125, and the sample obtained by the filtering method needs to be reloaded, so that the cementing effect of the ferric oxide is reduced artificially in the compression test, and the yield stress ratio f is lower. The test device and the method for testing the influence of the ferric oxide on the yield stress of the cohesive soil can overcome the defects of two previous methods, avoid the disturbance of the soil sample by one-time sample preparation and sample loading, improve the accuracy of the compression test for removing the ferric oxide sample, and provide guidance for researching the influence of the ferric oxide on the yield stress of the cohesive soil. Further, as shown in fig. 8 and 9, the red clay sample used in example 2 was tested by the conventional method one (soaking method), and the cumulative time required for the test was 70 days, and the mass of the consumed soil sample was 300g; the accumulated time of the test required by the conventional method II (filtering method) is 90 days, and the mass of the consumed soil sample is 250g. Compared with the two previous methods, the method in the embodiment 2 reduces the test time by 35.7% and 50.0% respectively, and reduces the soil sample mass consumption by 60.0% and 52.0% respectively, and the repeated test shows that the technical scheme of the invention has certain superiority.
Comparative test 2:
To further compare the extent of iron oxide content removed by the method of the present invention with the prior art methods and the effect of the measured cohesive soil yield stress, this comparative test 2 was conducted using a Guangdong cohesive soil consistent with example 3, which contained 3.6% -5.9% iron oxide. The test method, conditions and steps in this comparative test 2 were identical to those of comparative test 1. Fig. 7 shows the results of a test apparatus and method for testing the effect of iron oxide on cohesive soil yield stress using the present invention, as a yield stress ratio, and the results of a test of the prior art method one (soaking method) and the prior art method two (filtering method). The Guangdong cohesive soil of the embodiment 3 is tested by adopting the first method (soaking method), the content of residual ferric oxide in a sample after ferric oxide is removed is measured to be 0.03%, the obtained yield stress ratio f is 2.120, and compared with the result of the invention, the yield stress ratio f is 1.763, the yield stress ratio f shows higher; the content of residual ferric oxide in the sample after ferric oxide removal is 0.02% measured by the prior method II (filtering method), the yield stress ratio f of the obtained result is 1.500, and compared with the result of the invention, the yield stress ratio f is 1.763, the yield stress ratio f is lower. Consistent with the conclusion obtained in the comparative test 1, the comparative test 2 also shows that the test device and the test method for testing the influence of the ferric oxide on the yield stress of the cohesive soil optimize the defects of the prior method I (soaking method) and the prior method II (filtering method). Further, as shown in fig. 10 and 11, the cohesive soil sample used in example 3 was tested by the conventional method one (soaking method), the cumulative time required for the test was 60 days, and the mass of the consumed soil sample was 320g; the accumulated time of the test required by the conventional method II (filtering method) is 80 days, and the mass of the consumed soil sample is 260g. Compared with the two previous methods, the method in the embodiment 3 reduces the test time by 46.2% and 56.25% respectively, and reduces the soil sample mass consumption by 62.5% and 53.8% respectively, and the repeated test shows that the technical scheme of the invention has certain superiority.
According to the test device and the test method for testing the influence of the ferric oxide on the yield stress of the cohesive soil, provided by the invention, in the embodiment 2, the embodiment 3, the comparative test 1 and the comparative test 2, the DCB solution is injected into the soil sample through the pressure provided by the air compressor, and the sample preparation and sample loading processes are completed on the compression device at one time, so that the test time is saved, the working efficiency is improved, the sample after the ferric oxide is removed can be compressed at one time, the sample is not required to be reloaded for the test, the disturbance is reduced, and the accuracy of the test result is improved. Proved by verification, the method provided by the invention can remove the ferric oxide contained in the cohesive soil, and accurately measure and evaluate the influence of the ferric oxide on the yield stress of the cohesive soil.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the invention, and any simple modification, variation and equivalent structural changes of the above embodiments according to the principles of the present invention still fall within the scope of the technical solution of the present invention.

Claims (5)

1. A test method for testing influence of ferric oxide on yield stress of cohesive soil comprises the following steps:
(1) Preparing sodium dithionite-sodium citrate-sodium bicarbonate solution: fully mixing a sodium citrate solution with the concentration of 0.3mol/L, a saturated sodium chloride solution, a sodium bicarbonate solution with the concentration of 1mol/L and a sodium dithionite solution with the concentration of 0.1mol/L according to the ratio of 1:1:1 to prepare a DCB solution 1L;
(2) Determining the initial pore ratio of the soil sample: taking an undisturbed cohesive soil block-shaped soil sample, testing the density rho, the specific gravity G s and the water content w according to the standard of a geotechnical test method, and according to the measured density rho, the specific gravity G s and the water content w, passing through a formula Calculating and determining an initial pore ratio e 0 of the soil sample;
Wherein: e 0 is the initial void ratio, ρ is the density, G s is the specific gravity, and w is the water content;
(3) Sample preparation and sample loading: cutting a ring cutter sample along the deposition direction of a block-shaped soil sample by using a ring cutter with the inner diameter of 61.8mm and the height of 20mm, respectively attaching a first test paper and a second test paper to the upper part and the lower part of the sample with the ring cutter, placing the test paper and the second test paper on a second permeable stone, placing the first permeable stone in the inner part of the first support rod and the second support rod and the upper part of a chassis, placing a porous permeable plate in the porous permeable plate, wherein the porous permeable plate is hollow, the upper end is closed, the lower end is fully distributed with 1 mm-diameter permeable holes with the interval of 1mm, connecting a second pipeline with the porous permeable plate, placing a fixed plate above the porous permeable plate, aligning a displacement guide rod with the center of the fixed plate, erecting the bottom of a dial gauge on the fixed plate, placing the upper plate on the upper part of the first support rod and the first support rod, screwing and fixing the first support rod by using a first bolt and a third bolt, screwing the fixed chassis, horizontally placing an L-shaped support rod above the displacement guide rod and the support rod, and horizontally placing the support rod and the support rod in the L-shaped empty state under the condition;
(4) Leaching to remove ferric oxide: pouring the prepared sodium dithionite-sodium citrate-sodium bicarbonate solution into a water storage barrel, sequentially opening a first valve, a second valve and a third valve, opening an air compressor to enable the air compressor to inject air into the water storage barrel, observing a pressure gauge to adjust the air compressor, providing 100kPa, injecting DCB solution into a sample through a second pipeline and a porous water permeable plate in sequence, enabling filtrate after chemical reaction of the DCB solution and the sample to flow into a filtrate receiving barrel through the first pipeline, taking out filtrate in the filtrate receiving barrel every other day, closing the air compressor when the iron oxide content is lower than 0.01%, and stopping leaching test;
(5) Compression test: resetting the dial indicator, adding weights on a tray, sequentially pressurizing step by step until the test is finished according to the pressurizing conditions that the loading pressures of the first level to the ninth level are 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa, 1600kPa and 3200kPa respectively, repeating the step (3) once, and carrying out a compression test on the non-removed ferric oxide soil sample under the same loading conditions without opening the air compressor, the first valve, the second valve and the third valve;
(6) Result analysis and calculation: calculating the void ratio e i of the sample under each level of pressure, wherein the calculation formula is e i＝e0-(1+e0)×Si/(S1i-S0i), wherein e 0 is the initial void ratio of the soil sample, S i is the accumulated deformation of the sample under the loading pressure of the first level to the ninth level, S 1i is the final reading of the dial indicator under the loading pressure of the first level to the ninth level, S 0i is the initial reading of the dial indicator under the loading pressure of the first level to the ninth level, the void ratio e i of the sample under each level of pressure and the corresponding loading pressure P are calculated, the relationship between the void ratio e i and the LogP is drawn, the curvature maximum point of the relationship between e i and the LogP is found, and the perpendicular is drawn downwards, the intersection point between the perpendicular and the abscissa is the yield stress P P, the compression test results of the sample after iron oxide removal and the sample without iron oxide removal are processed and analyzed, the corresponding yield stress P P( Front part ) and P P( Rear part (S) ) are respectively obtained, and the ratio of P P( Front part ) of the sample before iron oxide removal to P P( Rear part (S) ) after iron oxide removal is defined as the stress ratio P=f= P( Front part )/PP( Rear part (S) ).
2. The method for testing the effect of iron oxide on cohesive soil yield stress according to claim 1, wherein: the pressure provided by the air compressor in the step (4) is 100kPa, and the frequency of performing iron oxide test on the filtrate in the filtrate receiving barrel is 1/7 days.
3. A test apparatus for carrying out a test method for testing the effect of iron oxide on cohesive soil yield stress as claimed in claim 1, comprising: chassis (1), upper disc (2), first branch (3 a), porous water-permeable plate (4), first permeable stone (5 a), first bolt (8 a), fixed plate (9), displacement guide arm (10), L branch (11), tray (12), first pipeline (14 a), first valve (15 a), air compressor (18), support (21), first test paper (23 a), its characterized in that: the chassis (1) and the upper disc (2) are respectively connected through a first supporting rod (3 a) and a second supporting rod (3 b), wherein the first supporting rod (3 a) and the upper disc (2) are fixed by a first bolt (8 a); the first supporting rod (3 a) and the chassis (1) are fixed by a second bolt (8 b); the second supporting rod (3 b) and the upper disc (2) are fixed by a third bolt (8 c); the second supporting rod (3 b) and the chassis (1) are fixed by a fourth bolt (8 d), the first supporting rod (23 a) and the second supporting rod (23 b) are respectively attached to the upper part and the lower part of the sample (7) in the annular cutter (6), the sample (7), the upper part and the lower part of the first supporting rod (23 a) and the second supporting rod (23 b) are respectively provided with a first permeable stone (5 a) and a second permeable stone (5 b), the second permeable stone (5 b) is placed on the upper part of the chassis (1), the annular cutter (6), the sample (7), the first supporting rod (3 a) and the second supporting rod (3 b) are respectively placed inside the annular cutter (7), the first supporting rod (23 a), the second supporting rod (23 b), the first permeable stone (5 a) and the second permeable stone (5 b), the upper part of the first permeable stone (5 a) is respectively connected with the porous plate (4) and the fixed plate (9), the fixed plate (9) is vertically provided with a dial indicator (20), the fixed plate (9) is connected with the guide rod (10) and the guide rod (10) is connected with the support (11) through a vertical displacement type support (12, and the support (11) is connected with the support (11) of the support (12) and the support (12) is respectively connected with the support (11) through the support (12) The first pipeline (14 a) is connected, the first pipeline (14 a) is connected with the receiving barrel (19), the third pipeline (14 c) is respectively connected with the third valve (15 c) and the air compressor (18), and the second valve (15 b) is respectively connected with the porous water permeable plate (4) and the second pipeline (14 b).
4. The test device according to claim 3, wherein the second pipeline (14 b) is connected with the water storage barrel (16), a pressure gauge (17) is arranged at the upper part of the water storage barrel (16), the third valve (15 c) is respectively connected with the water storage barrel (16) and the third pipeline (14 c), and the third pipeline (14 c) is connected with the air compressor (18).
5. The test device according to claim 3, wherein the porous water permeable plate (4) is hollow, the upper end is closed, and the lower end is provided with 1mm diameter water permeable holes (24) with a distance of 1 mm.
CN202210245168.3A 2022-03-11 2022-03-11 Test method and device for testing influence of ferric oxide on yield stress of cohesive soil Active CN114624081B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210245168.3A CN114624081B (en) 2022-03-11 2022-03-11 Test method and device for testing influence of ferric oxide on yield stress of cohesive soil

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210245168.3A CN114624081B (en) 2022-03-11 2022-03-11 Test method and device for testing influence of ferric oxide on yield stress of cohesive soil

Publications (2)

Publication Number Publication Date
CN114624081A CN114624081A (en) 2022-06-14
CN114624081B true CN114624081B (en) 2024-05-10

Family

ID=81901366

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210245168.3A Active CN114624081B (en) 2022-03-11 2022-03-11 Test method and device for testing influence of ferric oxide on yield stress of cohesive soil

Country Status (1)

Country Link
CN (1) CN114624081B (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017066644A (en) * 2015-09-29 2017-04-06 基礎地盤コンサルタンツ株式会社 Examination method of consolidation yield stress
CN112781945A (en) * 2019-11-04 2021-05-11 榆林学院 Penetration consolidation experimental method capable of controlling conditions through multiple experiments
CN113820194A (en) * 2021-10-25 2021-12-21 福建工程学院 Infiltration device and method for removing free iron oxide in soil

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017066644A (en) * 2015-09-29 2017-04-06 基礎地盤コンサルタンツ株式会社 Examination method of consolidation yield stress
CN112781945A (en) * 2019-11-04 2021-05-11 榆林学院 Penetration consolidation experimental method capable of controlling conditions through multiple experiments
CN113820194A (en) * 2021-10-25 2021-12-21 福建工程学院 Infiltration device and method for removing free iron oxide in soil

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Role of free iron oxides in the physicochemical and mechanical properties of natural clay;张先伟等;《Engineering Geology》;20220620;全文 *
强酸对柳州红黏土物理力学特性的影响;吕海波;季春生;谢超;曾召田;王勇;徐云山;;广西大学学报(自然科学版);20170825(04);全文 *
氧化铁胶体与黏土矿物的交互作用及其对黏土土性影响;张先伟等;《岩土工程学报》;20140131;全文 *

Also Published As

Publication number Publication date
CN114624081A (en) 2022-06-14

Similar Documents

Publication Publication Date Title
CN107727679B (en) A kind of characterization Deep Carbonate Rocks petrophysics characterization method
Baldi et al. A reevaluation of conventional triaxial test methods
CN111650108B (en) Method and device for measuring effective porosity of shale rock
CN108827853B (en) Nuclear magnetic resonance-based tight reservoir rock electric measurement device and measurement method
US20240027379A1 (en) Method for quantitative evaluation on sensitivity of shale oil and gas reservoir to injected fluids
CN102980842A (en) System and method for testing anisotropy permeability coefficient of layered coarse-grained soil body
CN108458951B (en) Method for rapidly determining coal seam gas content through desorption rate
CN107655771A (en) A kind of experimental rig and its test method for simulating the disintegration of side slope Test in Situ
CN109580454A (en) A method of compact reservoir Fluid Sensitivity is tested with pressure oscillation method
CN114624081B (en) Test method and device for testing influence of ferric oxide on yield stress of cohesive soil
CN112964562A (en) Triaxial test equipment for measuring eroded soil particles under action of seepage force
CN106323837A (en) Novel testing method for anti-permeability and durability of cement concrete
RU2542998C1 (en) Gas permeability anisotropy laboratory measurement on whole cores
CN209821099U (en) Multifunctional compact gas reservoir dynamic parameter joint measurement device based on nuclear magnetic resonance
CN207689304U (en) A kind of device measuring soil sample water suction quality and rate of water absorption
CN207457018U (en) Geotextile is compressed axially method clogging test device
CN113916748B (en) Device and method for measuring shale matrix permeability and recovery ratio by light oil
CN115146483A (en) Novel movable fluid use lower limit calculation method
CN214427145U (en) Geotechnical CBR automatic test device
CN114486977A (en) Quantitative evaluation method and device for pore space characteristics with different causes
CN112665983A (en) Geotechnical CBR automatic test device
CN107870227B (en) Method and device for detecting apparent porosity of artificial sand
CN208547635U (en) A kind of full-automatic Seep- Solidifying combined test device
CN116660306B (en) Experimental method for measuring shale gas content based on plunger samples and crushed samples
CN117347410A (en) Shale porosity testing method under simulated formation pressure condition

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