CN108375505B - High-precision linear stress path test method for frozen soil - Google Patents

High-precision linear stress path test method for frozen soil Download PDF

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CN108375505B
CN108375505B CN201810169833.9A CN201810169833A CN108375505B CN 108375505 B CN108375505 B CN 108375505B CN 201810169833 A CN201810169833 A CN 201810169833A CN 108375505 B CN108375505 B CN 108375505B
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frozen soil
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徐湘田
白瑞强
王永涛
曹阳
杨宗维
何扬
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Inner Mongolia University
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    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants
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    • G01—MEASURING; TESTING
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    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract

The invention discloses a high-precision linear stress path test method for frozen soil, which comprises the following steps: (1) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out; (2) and (3) calculating the actual volume strain in the test process according to the test result of the step (1), and correcting the cross section area of the sample to obtain the actual stress path slope k'. The method can realize a linear stress path with any slope, and fills the gap that a complex stress path test is difficult to develop in frozen soil; the cross-sectional area of the sample is corrected by calculating the axial stress, the volume strain is taken into account, and the axial strain epsilon of the previous test is adopted when the cross-sectional area of the sample is corrected1The relation with the cross-sectional area A is corrected, so that the problem that the volume strain cannot be considered in the current loading process is solved; the invention develops a new stress path test method on the existing frozen soil triaxial apparatus, does not add additional equipment, and greatly improves the service efficiency of the existing test device.

Description

High-precision linear stress path test method for frozen soil
The technical field is as follows:
the invention relates to a frozen soil mechanical test method, in particular to a high-precision linear stress path test method for frozen soil.
Background art:
the linear stress path test is a test for keeping dq/dp-k as a constant in a triaxial test of a rock-soil material, can be used for investigating mechanical characteristics of the frozen soil material under different k values, can be used for determining a yield surface and a hardening law of the frozen soil material, and can also be used for verifying a constitutive model of the frozen soil. Frozen soil is a special soil body composed of ice, unfrozen water, soil particles and gas, the structure of the frozen soil is complex, and the mechanical behavior is influenced by various factors such as temperature, loading rate, stress condition and the like. At present, in the research of mechanical properties of frozen earth, a uniaxial compression test and a conventional triaxial compression test are mainly applied, and the two tests are actually only a linear stress path with the slope k being 3. The uniaxial and conventional triaxial tests can be realized through a strain control mode, namely, the axial pressurizing plunger is loaded at a constant speed, the volume strain does not need to be calculated in the test process, and the correction area does not need to be calculated, so that the deformation and damage rules of the frozen soil under other linear stress paths cannot be investigated through the uniaxial compression test and the conventional triaxial compression test. In actual engineering, frozen soil serving as a structural foundation or a structure undergoes various complicated stress paths, and deviation from actual working conditions occurs only by guiding engineering design through frozen soil mechanical properties obtained through a linear stress path test with a slope k of 3.
The uniaxial compression test and the conventional triaxial compression test can only reflect the mechanical deformation behavior of the frozen soil under the condition that k is 3, and the arbitrary linear stress path test can reflect the mechanical deformation behavior of the frozen soil under the arbitrary linear stress path, so that the mechanical properties of the frozen soil under more stress paths can be obtained, and the determined frozen soil constitutive model can predict the mechanical deformation behavior of the frozen soil more accurately. To investigate the mechanical response of the frozen soil under different stress paths and perform engineering design based on the mechanical response, a stress path test method for more frozen soil needs to be developed to comprehensively investigate the mechanical properties of the frozen soil and establish a reasonable constitutive model of the frozen soil.
Any linear stress path can not be realized through a strain control mode, and needs to be realized through the strain control mode, and the loading area needs to be corrected by using the volume strain in the test process, so that the required loading real axial force is solved. At present, when a stress path test of frozen soil is carried out by using a low-temperature triaxial apparatus, the confining pressure increment delta sigma in actual operation3The confining pressure can be directly applied by a confining pressure loading system, but the axial force increment delta F and the axial stress increment delta sigma delta can only be controlled by the existing frozen soil triaxial apparatus axial loading system at home and abroad1The Δ F/a is calculated (a is the cross-sectional area of the sample), and the frozen soil sample is compressed in the axial direction during the test, and the cross-sectional area a is continuously increased and accurately calculatedThe cross-sectional area a of the sample at each loading step must be estimated beforehand in order to calculate the Δ F applied at each step, and the cross-sectional area a is determined from a ═ a0(1-εv)/(1-εa) Calculation (A)0Is the original area of the sample), the volume strain epsilon cannot be calculated when the test is not completedvAlso, Α and Δ F at each step loading could not be obtained. Therefore, no method for carrying out any linear stress path test on frozen soil by using a low-temperature triaxial apparatus exists at present.
The invention content is as follows:
the invention provides a high-precision linear stress path test method for frozen soil by utilizing the existing low-temperature triaxial apparatus in order to change the current situation that a complex stress path test is lacked in a frozen soil mechanical test method.
The invention is implemented by the following technical scheme: a high-precision linear stress path test method for frozen soil comprises the following steps: (1) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out; (2) according to the test result of the step (1), calculating the actual volume strain in the test process, and correcting the cross section area of the sample to obtain the slope k' of the actual stress path;
(1) and (3) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out:
step one, manufacturing a frozen soil sample;
placing the frozen soil sample into a pressure chamber of a frozen soil triaxial apparatus, and keeping the temperature of the pressure chamber at a target test temperature;
step three, applying confining pressure to the starting point of the stress path;
step four, setting a target stress path slope k and setting the confining pressure increment delta sigma of each step3；
Step five, according to the axial strain epsilon1Generally much larger than the volume strain epsilonvThe fact that the increase of axial strain per step is set to not more than 0.1%, the cross-sectional area of the sample is first disregarded for the correction of the volume strain, with a' ═ a0/(1-ε1) Substituted by A ═ A0(1-εv)/(1-ε1) Calculating an approximate cross-sectional area A' of the frozen soil sample; in No. atWhen the cross-sectional area of the sample is corrected by the volumetric strain, a proper axial strain increment in each step can be set according to the properties of different frozen soils, so that the iterative test times are reduced.
Wherein: a. the0Is the original cross-sectional area of the frozen soil sample, epsilonvIs volume strain,. epsilon1Is the axial strain;
step six, according to the step four and the step five in the step (1), using
Figure GDA0002372639780000031
Calculating and setting axial force increment of each step
Figure GDA0002372639780000032
Then, carrying out a linear stress path test of an approximate k slope;
(2) according to the test result in the step (1), calculating the actual volume strain in the test process, correcting the cross section area of the sample to obtain the actual stress path slope k':
step one, after the test of the step (1) is finished, measuring Z in the test process of the step (1)dAnd CdCalculating the volume strain epsilon in the test process by using the formula (1-1)v，
Figure GDA0002372639780000041
Wherein Z isdAnd Z0Respectively the current position and the initial position of an axial pressurizing plunger of the frozen soil triaxial apparatus; v0Is the original volume of the frozen soil sample at the beginning of the test, ShFor confining pressure loading the cross-sectional area of the system piston, CdLoading the current position of the piston for confining pressure in the test, C0Loading the initial position of the piston for confining pressure at the beginning of the test;
step two, the calculated volume strain epsilon of each stepvAnd ε in the step (1) test1Substituting a ═ a0(1-εv)/(1-ε1) Calculating to obtain the real cross-sectional area A of the sample in each step;
step three, obtaining the product according to the step two in the step (2)The real cross section area A of the sample at each step and the actual axial force increment at each step in the test at the step (1) are calculated to obtain the real axial stress increment delta sigma at each step1＝ΔF/Α；
Step four, utilizing the true axial stress increment delta sigma of each step obtained by the calculation of the step three in the step 21And a preset increase delta sigma of confining pressure per step3Calculating the actual stress path slope k' according to the formula (1-2),
Figure GDA0002372639780000042
if the calculated relative error between the actual stress path slope k' value and the set target stress path slope k value is within the allowable precision range of the test, and the recommended relative error is 5%, the test in the step (1) can be used as a linear stress path test meeting the precision k slope.
Further, in the step (2), if the relative error between the actual stress path slope k' value and the set target stress path slope k value exceeds the allowable accuracy of the test, according to the test result of the step (1), fitting the real cross-sectional area a of the sample obtained in each step calculated in the step two in the step (2) with a high-accuracy function to the axial strain epsilon in the step (1)1The relation between the sample and the real cross-sectional area A is recorded as A ═ f (epsilon)1)；
A. Setting a target stress path slope k, and setting a confining pressure increment delta sigma at each step3；
B. Setting the axial strain increment of each step to be not more than 0.1 percent, and utilizing the function A ═ f (epsilon)1) Calculating the approximate cross-sectional area A' of the frozen soil sample;
C. according to the results of step A and step B, using
Figure GDA0002372639780000051
Calculating and setting axial force increment of each step
Figure GDA0002372639780000052
Then, carrying out a linear stress path test of an approximate k slope;
after the test is finished, repeating the step (2), calculating the real cross section area A and the actual stress path slope k 'of the sample, and if the relative error between the actual stress path slope k' value obtained by the test and the set target stress path slope k value is within the test allowable precision range, the test can be used as a linear stress path test meeting the precision k slope;
if the relative error between the actual stress path slope k' value obtained by the test and the set target stress path slope k value exceeds the allowable precision of the test, according to the new epsilon1Function a-f (e)1) And repeating the step A, the step B and the step C, then carrying out the approximate k slope path test, and repeating iteration until the relative error between the actual stress path slope k' value and the set target stress path slope k value is within the test allowable precision range, wherein the last test can be used as the k slope stress path test with sufficient precision. The volume strain of the previous test is counted in the cross-sectional area correction of the sample of the next test through the step, and the slope k' value of the actual stress path continuously approaches the slope k value of the set target stress path.
Specifically, the frozen soil triaxial apparatus is a low-temperature triaxial apparatus generally having stress control, strain control and multi-channel control modes at present.
In particular, the stress path origin σ3When the slope k is 0, an arbitrary straight line stress path test in the range of (0, infinity) can be realized; stress path starting point σ3Above 0, an arbitrary linear stress path test with a slope k in the range (-infinity, + ∞) can be realized.
The principle and the test steps of the method can be applied to the test of the linear stress path of the fused soil with high precision requirement.
The linear stress path test method is based on the following calculation formula in the test setting:
Figure GDA0002372639780000061
(1-k/3)Δσ1＝(1+2k/3)Δσ3(1-4)
where p is the mean stress, q is the bias stress, σ1For axial stress, σ3Is confining pressure; Δ p, Δ q, Δ σ1And Δ σ3Mean stress increment, bias stress increment, axial stress increment and confining pressure increment respectively, and k is the slope of a stress path.
According to the formula (1-4), after the slope k is given and the confining pressure increment is set, the axial stress increment which is required to be arranged on the frozen soil low-temperature triaxial apparatus can be calculated according to the formula (1-5) to realize various linear stress path tests.
Figure GDA0002372639780000062
Increase of confining pressure Δ σ in actual operation3Can be directly applied and controlled by a confining pressure loading system. However, the existing frozen soil triaxial apparatus axial loading system at home and abroad can not directly apply and control the axial stress increment, only the axial stress increment delta F can be controlled, and the axial stress increment needs to pass through delta sigma1The cross section area A of the sample at each step of loading must be measured in advance to accurately calculate the axial force increment delta F applied at each step, and the cross section area A of the sample at each step of loading cannot be calculated when the test is not finished.
The invention has the advantages that:
(1) the invention provides a high-precision linear stress path test method for frozen soil, which can realize a linear stress path with any slope for the frozen soil and provides a test means for investigating the deformation and damage behaviors of the frozen soil under a complex stress path;
(2) according to the invention, axial strain and volume strain are simultaneously counted in the final stress path test result of the frozen soil, so that the mechanical property of the frozen soil under a real stress path can be obtained;
(3) the invention applies the corrected cross-sectional area of the sample when calculating the axial stress, and takes the volume strain into account,using the axial strain epsilon of the last test1The relation with the cross-sectional area A is corrected, so that the problem that the volume strain cannot be considered in the current loading process is solved;
(4) the method controls the precision of the frozen soil test of the linear stress path with any slope by a method similar to iteration, the area correction of each iteration contains the volume strain factor of the previous test, the result is continuously accurate, and the linear stress path test result with any precision can be obtained through a plurality of iterations;
(5) in the first test process, the axial strain step length delta epsilon of each step is taken1The approximate cross-sectional area A' of each step is not more than 0.1 percent, so that the change is small, the k value error obtained when the volume strain is not counted is small, the iterative test times are reduced, and the test efficiency is improved;
(6) the invention develops a new linear stress path test method on the traditional frozen soil triaxial apparatus, does not increase additional equipment, and improves the use efficiency of the existing test device.
Description of the drawings:
FIG. 1 is a flow chart of a high-precision linear stress path test method for frozen earth;
FIG. 2 is a schematic diagram of calculation of slope k of a linear stress path test;
FIG. 3 is a graph of the experimental values of the linear stress path with slope k equal to 3 in example 1;
FIG. 4 is a graph comparing the experimental value and the preset value of the linear stress path with the slope k of 2 in example 2;
FIG. 5 is a graph comparing 2 test values and preset values of a linear stress path with a slope k of 5 in example 3;
the specific implementation mode is as follows:
examples 1 to 3 all used a water content of 16% and a dry density of 1.5g/cm3The root river clay is used for preparing a frozen soil sample to perform a linear stress path test of the frozen soil, and the preparation method of the frozen soil sample comprises the following specific steps:
firstly, preparing soil into a loose soil body with target water content, keeping for about 6 hours under the condition of limiting evaporation to ensure that the water content is uniform in the soil body, then filling the soil body into a mold in a layering manner, tamping and compacting the soil according to the dry volume weight required by the test, and preparing a cylindrical sample with the height of 100mm and the diameter of 50 mm. And putting the sample together with the mould into a refrigeration box, quickly freezing at-30 ℃, demoulding the sample after freezing for about 48 hours, and then keeping the temperature of the sample at the test temperature for more than 24 hours to prepare the frozen root river clay sample.
Example 1: and (3) putting the prepared frozen soil sample into a pressure chamber of a low-temperature triaxial apparatus with a set test temperature, applying confining pressure to a stress path starting point of 2MPa after the temperature is stable, keeping for 5 minutes, and performing a frozen soil conventional triaxial compression test, wherein as shown in fig. 3, a frozen soil linear stress path test result with a slope k equal to 3 can be accurately obtained by a conventional triaxial compression test path.
Example 2: a high-precision linear stress path test method for frozen soil comprises the following steps: (1) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out; (2) according to the test result of the step (1), calculating the actual volume strain in the test process, and correcting the cross section area of the sample to obtain the slope k' of the actual stress path; wherein,
(1) and (3) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out:
step one, preparing a frozen soil sample, and keeping the temperature of the frozen soil sample at a target test temperature of-10 ℃ for 24 hours;
placing the frozen soil sample into a pressure chamber of a frozen soil triaxial apparatus, and keeping the temperature of the pressure chamber at a target test temperature of-10 ℃;
step three, applying confining pressure of 3MPa to the starting point of the stress path, and keeping for 5 minutes;
step four, setting the gradient k of the target stress path to be 2, and setting the confining pressure increment delta sigma of each step3＝0.02MPa/min；
Step five, according to the axial strain epsilon1Generally much larger than the volume strain epsilonvThe axial strain increment per step was set to 0.1%, and the cross-sectional area of the sample was first corrected without counting the volume strain, using a' ═ a0/(1-ε1) Substituted by A ═ A0(1-εv)/(1-ε1) Calculating an approximate cross-sectional area A' of the frozen soil sample;
wherein: a. the0Is the original cross-sectional area of the frozen soil sample, epsilonvIs volume strain,. epsilon1Is the axial strain;
step six, according to the step four and the step five in the step (1), using
Figure GDA0002372639780000101
Calculating and setting axial force increment of each step
Figure GDA0002372639780000102
Then, carrying out a linear stress path test of an approximate k slope;
(2) according to the test result in the step (1), calculating the actual volume strain in the test process, correcting the cross section area of the sample to obtain the actual stress path slope k':
step one, after the test of the step (1) is finished, measuring Z in the test process of the step (1)dAnd CdCalculating the volume strain epsilon in the test process by using the formula (1-1)v，
Figure GDA0002372639780000103
Wherein Z isdAnd Z0Respectively the current position and the initial position of an axial pressurizing plunger of the frozen soil triaxial apparatus; v0Is the original volume of the frozen soil sample at the beginning of the test, ShFor confining pressure loading the cross-sectional area of the system piston, CdLoading the current position of the piston for confining pressure in the test, C0Loading the initial position of the piston for confining pressure at the beginning of the test;
step two, the calculated volume strain epsilon of each stepvAnd ε in the step (1) test1Substituting a ═ a0(1-εv)/(1-ε1) Calculating to obtain the real cross-sectional area A of the sample in each step;
step three, calculating the true axial stress increment delta sigma of each step according to the true cross-sectional area A of the sample obtained in the step two in the step (2) and the actual axial force increment of each step in the test in the step (1)1＝ΔF/Α；
Step four, utilizing the true axial stress increment delta sigma of each step obtained by the calculation of the step three in the step 21And a preset increase delta sigma of confining pressure per step3Calculating the actual stress path slope k' according to the formula (1-2),
Figure GDA0002372639780000111
as shown in fig. 3, the test result is that the actual stress path slope k 'is calculated to be 2.07, the relative error between the actual stress path slope k' and the set target stress path slope k is 3.5%, and the set relative error is not exceeded by 5%, so the test in step (1) can be used as the k-slope stress path test with sufficient accuracy.
Example 3: a high-precision linear stress path test method for frozen soil comprises the following steps: (1) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out; (2) according to the test result of the step (1), calculating the actual volume strain in the test process, and correcting the cross section area of the sample to obtain the slope k' of the actual stress path; wherein,
(1) and (3) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out:
step one, preparing a frozen soil sample, and keeping the temperature of the frozen soil sample at a target test temperature of-10 ℃ for 24 hours;
placing the frozen soil sample into a pressure chamber of a frozen soil triaxial apparatus, and keeping the temperature of the pressure chamber at a target test temperature of-10 ℃;
step three, applying confining pressure of 1MPa to the starting point of the stress path, and keeping for 5 minutes;
step four, setting the gradient k of the target stress path to be 5, and setting the confining pressure increment delta sigma of each step3＝0.002MPa/min；
Step five, according to the axial strain epsilon1Generally much larger than the volume strain epsilonvThe axial strain increment per step was set to 0.1%, and the cross-sectional area of the sample was first corrected without counting the volume strain, using a' ═ a0/(1-ε1) Substituted by A ═ A0(1-εv)/(1-ε1) Calculating an approximate cross-sectional area A' of the frozen soil sample;
wherein: a. the0Is the original cross-sectional area of the frozen soil sample, epsilonvIs volume strain,. epsilon1Is the axial strain;
step six, according to the step four and the step five in the step (1), using
Figure GDA0002372639780000121
Calculating and setting axial force increment of each step
Figure GDA0002372639780000122
Then, carrying out a linear stress path test of an approximate k slope;
(2) according to the test result in the step (1), calculating the actual volume strain in the test process, correcting the cross section area of the sample to obtain the actual stress path slope k':
step one, after the test of the step (1) is finished, measuring Z in the test process of the step (1)dAnd CdCalculating the volume strain epsilon in the test process by using the formula (1-1)v，
Figure GDA0002372639780000123
Wherein Z isdAnd Z0Respectively the current position and the initial position of an axial pressurizing plunger of the frozen soil triaxial apparatus; v0Is the original volume of the frozen soil sample at the beginning of the test, ShFor confining pressure loading the cross-sectional area of the system piston, CdLoading the current position of the piston for confining pressure in the test, C0Loading the initial position of the piston for confining pressure at the beginning of the test;
step two, the calculated volume strain epsilon of each stepvAnd ε in the step (1) test1Substituting a ═ a0(1-εv)/(1-ε1) Calculating to obtain the real cross-sectional area A of the sample in each step;
step three, according to the real cross-sectional area A of the sample obtained in the step two in the step (2) and the actual axial force of each step in the test in the step (1)Incremental calculation of true axial stress increment delta sigma in each step1＝ΔF/Α；
Step four, utilizing the true axial stress increment delta sigma of each step obtained by the calculation of the step three in the step 21And a preset increase delta sigma of confining pressure per step3Calculating the actual stress path slope k' according to the formula (1-2),
Figure GDA0002372639780000131
calculating to obtain an actual stress path slope k '═ 4.5785, wherein the relative error between the actual stress path slope k' value and the set target stress path slope k value is 8.43%, and exceeds the set relative error by 5%, therefore, according to the test result of the step (1), the real cross-sectional area A of the sample obtained by the step two in the step (2) is fitted with a high-precision function to the axial strain epsilon in the step (1)1The relation between the sample and the real cross-sectional area A is recorded as A ═ f (epsilon)1)；
A. Setting the target stress path slope k to 5, and setting the confining pressure increment delta sigma at each step3＝0.002MPa/min；
B. The axial strain increment is set to 0.1% per step, using the function a ═ f (epsilon)1) Calculating the approximate cross-sectional area A' of the frozen soil sample;
C. according to the results of step A and step B, using
Figure GDA0002372639780000132
Calculating and setting axial force increment of each step
Figure GDA0002372639780000133
Then, carrying out a linear stress path test of an approximate k slope;
after the test is finished, repeating the step (2), calculating the real cross-sectional area A of the sample and the actual stress path slope k 'to 4.7815, and after one iteration, the relative error between the actual stress path slope k' value obtained by the test and the set target stress path slope k value is 4.37%, and the relative error does not exceed the set relative error by 5%, which indicates that the test can be used as the k slope stress path test with sufficient precision.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (4)

1. A high-precision linear stress path test method for frozen soil is characterized by comprising the following steps: which comprises the following steps:
(1) and (3) when the cross section area of the sample is corrected, the volume strain is not counted, and an approximate linear stress path test is carried out:
step one, manufacturing a frozen soil sample;
placing the frozen soil sample into a pressure chamber of a frozen soil triaxial apparatus, and keeping the temperature of the pressure chamber at a target test temperature;
step three, applying confining pressure to the starting point of the stress path;
step four, setting a target stress path slope k and setting the confining pressure increment delta sigma of each step3；
Step five, according to the axial strain epsilon1Generally much larger than the volume strain epsilonvThe fact that the increase of axial strain per step is set to not more than 0.1%, the cross-sectional area of the sample is first disregarded for the correction of the volume strain, with a' ═ a0/(1-ε1) Substituted by A ═ A0(1-εv)/(1-ε1) Calculating an approximate cross-sectional area A' of the frozen soil sample;
wherein: a. the0Is the original cross-sectional area of the frozen soil sample, epsilonvIs volume strain,. epsilon1Is the axial strain;
step six, according to the step four and the step five in the step (1), using
Figure FDA0002372639770000011
Calculating and setting axial force increment of each step
Figure FDA0002372639770000012
Then, a linear stress approximating a k-slope is performedPath testing;
(2) according to the test result in the step (1), calculating the actual volume strain in the test process, correcting the cross section area of the sample to obtain the actual stress path slope k':
step one, after the test of the step (1) is finished, measuring Z in the test process of the step (1)dAnd CdCalculating the volume strain epsilon in the test process by using the formula (1-1)v，
Figure FDA0002372639770000021
Wherein Z isdAnd Z0Respectively the current position and the initial position of an axial pressurizing plunger of the frozen soil triaxial apparatus; v0Is the original volume of the frozen soil sample at the beginning of the test, ShFor confining pressure loading the cross-sectional area of the system piston, CdLoading the current position of the piston for confining pressure in the test, C0Loading the initial position of the piston for confining pressure at the beginning of the test;
step two, the calculated volume strain epsilon of each stepvAnd ε in the step (1) test1Substituting a ═ a0(1-εv)/(1-ε1) Calculating to obtain the real cross-sectional area A of the sample in each step;
step three, calculating the true axial stress increment delta sigma of each step according to the true cross-sectional area A of the sample obtained in the step two in the step (2) and the actual axial force increment of each step in the test in the step (1)1＝ΔF/Α；
Step four, utilizing the true axial stress increment delta sigma of each step obtained by the calculation of the step three in the step 21And a preset increase delta sigma of confining pressure per step3Calculating the actual stress path slope k' according to the formula (1-2),
Figure FDA0002372639770000022
if the calculated relative error between the actual stress path slope k' value and the set target stress path slope k value is within the allowable accuracy range of the test, the test in the step (1) can be used as a linear stress path test meeting the accuracy k slope.
2. The method for testing the high-precision linear stress path of the frozen soil according to claim 1, wherein the method comprises the following steps: in the step (2), if the relative error between the actual stress path slope k' value and the set target stress path slope k value exceeds the allowable test precision, according to the test result of the step (1), fitting the actual cross-sectional area A of the sample obtained in each step in the step two in the step (2) by using a high-precision function to the axial strain epsilon in the step (1)1The relation between the sample and the real cross-sectional area A is recorded as A ═ f (epsilon)1)；
A. Setting a target stress path slope k, and setting a confining pressure increment delta sigma at each step3；
B. Setting the axial strain increment of each step to be not more than 0.1 percent, and utilizing the function A ═ f (epsilon)1) Calculating the approximate cross-sectional area A' of the frozen soil sample;
C. according to the results of step A and step B, using
Figure FDA0002372639770000031
Calculating and setting axial force increment of each step
Figure FDA0002372639770000032
Then, carrying out a linear stress path test of an approximate k slope;
after the test is finished, repeating the step (2), calculating the real cross section area A and the actual stress path slope k 'of the sample, and if the relative error between the actual stress path slope k' value obtained by the test and the set target stress path slope k value is within the test allowable precision range, the test can be used as a linear stress path test meeting the precision k slope;
if the relative error between the actual stress path slope k' value obtained by the test and the set target stress path slope k value exceeds the allowable precision of the test, according to the new epsilon1Function a-f (e)1) Repeating the step A, the step B and the step C, then carrying out the approximate k slope path test, and repeating the iterationAnd until the relative error between the actual stress path slope k' value and the set target stress path slope k value is within the allowable test precision range, the last test can be used as a k slope stress path test with sufficient precision.
3. The method for testing the high-precision linear stress path of the frozen soil according to claim 1 or 2, wherein the method comprises the following steps: the frozen soil triaxial apparatus is a low-temperature triaxial apparatus generally provided with stress control, strain control and multi-channel control modes at present.
4. The method for testing the high-precision linear stress path of the frozen soil according to claim 1 or 2, wherein the method comprises the following steps: stress path starting point σ3When the slope k is 0, an arbitrary straight line stress path test in the range of (0, infinity) can be realized; stress path starting point σ3Above 0, an arbitrary linear stress path test with a slope k in the range (-infinity, + ∞) can be realized.
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Title
不同温度梯度两种应力路径冻结中砂应力-应变特性试验研究;周国庆 等;《岩土工程学报》;20100331;第32卷(第3期);338-343 *
冻土中几类力学试验方法的探讨;徐湘田 等;《冰川冻土》;20111031;第33卷(第5期);1132-1138 *

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