Quantization method of saturated clay consolidation water release process

Abstract

The invention discloses a method for quantifying the consolidation and water release process of saturated clay, which comprises the following steps of: carrying out a one-dimensional saturated consolidation experiment on clay, and testing a sample which is consolidated stably under each stage of stress by combining a nuclear magnetic resonance technology, so as to obtain relaxation spectrograms under different stresses. And according to a relaxation spectrogram result, distinguishing free water, weakly bound water and strongly bound water in the clay, and quantitatively calculating the mass of different types of pore water under each stress. And counting the mass of the strong binding water into the mass of the soil particles, correcting the void ratio under each stage of stress, and further calculating the corrected moisture content of the soil sample. A verification result shows that a calculation result and test data have a good fitting degree. According to the method, the clay consolidation and water release process is revealed and quantified from the microscopic perspective, and a theoretical basis is provided for accurate prediction of clay consolidation settlement and engineering stability evaluation. The method is simple in test process and high in test accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnical engineering, and particularly relates to a quantitative method for a saturated clay consolidation water release process. BACKGROUND

[0002] The pore water release mechanism of clay in the consolidation process is an important problem in geotechnical engineering settlement prediction. The traditional Terzaghi consolidation theory simplifies the pore water as a free fluid, ignoring the physical and chemical action between the bound water and clay particles, especially lacking the study on the microphenomenon of the bound water changing into free water and releasing. In actual engineering, the saturated clay contains free water, weakly bound water and strongly bound water, part of the weakly bound water will change into free water and release under high stress, and the strongly bound water is difficult to release due to the strong adsorption of soil particles, resulting in the phenomenon that the theoretical prediction value deviates from the measured data in the low permeability clay in the classic model.

[0003] In the past research, most of the analysis and quantification are carried out on the macro mechanical parameters. Although some scholars consider the bound water when studying the clay consolidation problem, due to the limitation of dynamic monitoring technology, the research on the dynamic evolution and mutual transformation rule of different types of pore water in the consolidation process from the micro perspective is lacking. SUMMARY

[0004] The application aims at the prediction deviation of the water release amount caused by the simplification of pore water in the traditional consolidation theory, and the limitation of the identification of the dynamic evolution of pore water in the consolidation process in the prior art, and provides a quantitative method for the saturated clay consolidation water release process.

[0005] Technical scheme: In order to achieve the above-mentioned purpose, the application provides a quantitative method for the saturated clay consolidation water release process, which comprises the following steps:

[0006] Step (1): five cutter-shaped soil samples with the same dry density are prepared, and are simultaneously subjected to saturation treatment;

[0007] Step (2): the five saturated soil samples are placed into a nuclear magnetic resonance instrument for testing, a CPMG sequence is set, the relaxation signals of the five saturated soil samples in the initial state are collected, the SIRT model in the nuclear magnetic resonance instrument is used to inverse the obtained relaxation signals, the relaxation spectrum with the horizontal relaxation time T2 as the horizontal coordinate and the nuclear magnetic signal intensity M(T2) as the vertical coordinate is obtained as the initial state relaxation spectrum. Further, the pore water types are divided, and the T2 cutoff value for dividing the free water, weakly bound water and strongly bound water is obtained;

[0008] Step (3): the five cutter-shaped soil samples in step (2) are respectively placed in a consolidation instrument for one-dimensional saturated consolidation test, each soil sample is subjected to graded loading to a specified stress value, and the pore ratio of the soil sample after consolidation stabilization under each stress level is obtained;

[0009] Step (4): Put the solidified soil sample in step (3) into the nuclear magnetic resonance instrument for testing. Under the same CPMG sequence as step (2), the relaxation signals of 5 saturated soil samples under different stresses are collected. The SIRT model in the nuclear magnetic resonance instrument is used to invert the obtained relaxation signals to obtain the relaxation spectrum with the horizontal coordinate being the transverse relaxation time T2 and the vertical coordinate being the nuclear magnetic signal intensity M(T2), as the relaxation spectrum under each stress level;

[0010] Step (5): Put the T2 cutoff value obtained in step (2) into the initial state relaxation spectrum of step (2) and the relaxation spectrum under each stress level of step (4) to obtain the water content and mass of free water, weakly bound water and strongly bound water under the initial state and each stress level.

[0011] Step (6): Convert the mass of strongly bound water obtained in step (5) to volume and add it to the volume of soil particles to obtain the modified porosity considering the solid phase of strongly bound water. On this basis, the modified water content considering the strongly bound water in the soil sample consolidation process is calculated.

[0012] Further, the diameter of the ring knife-shaped sample in step (1) is 40 mm, and the height is 20 mm.

[0013] Further, in step (1), the saturation method is vacuum saturation, and the saturation pressure is -0.8 MPa.

[0014] Further, in steps (2) and (4), the parameters of the CPMG sequence used are: center frequency SF=13 MHz, frequency offset O1=43817.57 Hz, 90-degree pulse time P1=25 μs, 180-degree pulse time P2=48 μs, receiver bandwidth SW=250 kHz, RF delay RFD=0.002 ms, repetition sampling interval time TW=8000 ms, analog gain RG1=20 db, digital gain DRG1=2, preamplifier gain PRG=1, number of accumulated samples NS=16, number of echoes NECH=1000, and echo time TE=0.2 ms.

[0015] Further, in steps (2) and (4), the SIRT model is used to invert the relaxation signals for 100,000 times of iteration to obtain the relaxation spectrum.

[0016] Further, in step (3), the order of applying stress is: 59.68 kPa, 238.73 kPa, 716.20 kPa, 954.93 kPa, and 1909.86 kPa.

[0017] Further, in step (3), the porosity under each stress level is represented as:

[0018]

[0019] wherein e i represents the pore ratio of the soil sample under each stress level; e0 represents the initial pore ratio of the soil sample; h0 represents the initial height of the soil sample; and Δh represents the total deformation of the soil sample under each stress level.

[0020] Further, in the step (5), the water content of the free water under each stress level is represented as:

[0021] ω fw,i = ω i × α fw,i (2)

[0022] The water content of the weakly bound water under each stress level is represented as:

[0023] ω wbw,i = ω i × α wbw,i (3)

[0024] The water content of the strongly bound water under each stress level is represented as:

[0025] ω sbw,i = ω i × α sbw,i (4)

[0026] wherein ω i represents the water content of the soil sample under each stress level; ω fw,i represents the water content of the free water under each stress level; ω wbw,i represents the water content of the weakly bound water under each stress level; ω sbw,i represents the water content of the strongly bound water under each stress level; α fw,i represents the proportion of the nuclear magnetic signal of the free water; α wbw,i represents the proportion of the nuclear magnetic signal of the weakly bound water; and α sbw,i represents the proportion of the nuclear magnetic signal of the strongly bound water.

[0027] Further, in the step (5), the mass of the free water under each stress level is represented as:

[0028] m fw,i = m s × ω fw,i (5)

[0029] The mass of the weakly bound water under each stress level is represented as:

[0030] m wbw,i = m s × ω wbw,i (6)

[0031] The quality of the strong bound water under various stress levels is represented as:

[0032] m sbw,i = m s × ω sbw,i (7)

[0033] Wherein, m s is the mass of soil particles; m fw,i is the mass of free water under various stress levels; m wbw,i is the mass of weak bound water under various stress levels; and m sbw,i is the mass of strong bound water under various stress levels.

[0034] Further, in the step (6), the corrected void ratio of the soil sample is represented as:

[0035]

[0036] The change amount of the corrected void ratio of the soil sample is represented as:

[0037] Δe i ′ = e0 ′ - e i ′ (9)

[0038] Wherein, e i ′ represents the corrected void ratio of the soil sample; V s represents the volume of soil particles; ρ sbw represents the density of strong bound water, and is 1.3 g / cm 3 ; Δe i ′ represents the change amount of the corrected void ratio of the soil sample; and e0 ′ represents the corrected initial void ratio.

[0039] The corrected water content of the soil sample is represented as:

[0040]

[0041] Wherein, G s represents the specific gravity of the soil sample; ω t,i ′ represents the corrected water content of the soil sample under various stress levels; ω t,0 represents the water content of the soil sample in a saturated state; and ρ w represents the density of water, and is 1.0 g / cm 3 .

[0042] Beneficial effects, compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0043] The method quantitatively analyzes the mass of different pore water under various stress levels by correlating the pore water evolution distribution with the macroscopic mechanical behavior. The mass of the strongly bound water is included in the mass of the soil particles to correct the void ratio of the soil sample. The water content of the soil sample under various stress levels is calculated according to the corrected void ratio. The method can obtain more accurate water content of the soil sample, and thus improve the accuracy of the calculation of the consolidation settlement deformation of clay in practical engineering, and provide theoretical guidance for the settlement prediction of geotechnical engineering. The test process of the method is simple, and the test accuracy is high. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The present application implements a flowchart.

[0045] Figure 2 The present application is an example of the relaxation spectrum of the soil sample under various stress levels, wherein (a) is the relaxation spectrum of the soil sample S1 under various stress levels; (b) is the relaxation spectrum of the soil sample S2 under various stress levels.

[0046] Figure 3 The present application is an example of the mass change of different types of pore water of the soil sample under various stress levels, wherein (a) is the mass change of different types of pore water of the soil sample S1 under various stress levels; (b) is the mass change of different types of pore water of the soil sample S2 under various stress levels.

[0047] Figure 4 The present application is an example of the test data and the predicted ω t,i ′ -Δe i ′ The present application is an example of the test data and the predicted ω t,i ′ -Δe i ′ The present application is an example of the test data and the predicted ω t,i ′ -Δe i ′ The present application is an example of the test data and the predicted ω

[0048] DETAILED EMBODIMENT

[0049] The present application provides a quantitative method for the consolidation and water release process of saturated clay, which makes up for the lack of micro-mechanism research of the existing clay consolidation process, and thus improves the accuracy of the calculation of the consolidation settlement deformation of clay.

[0050] The application will be described in detail below with reference to the drawings and specific embodiments: In order to make the technical means, creative features, purposes and effects of the application easy to understand, the application will be further described below in conjunction with specific embodiments. It should be pointed out that the following detailed description is exemplary and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0051] As shown in Figure 1 The application provides a quantitative method for saturated clay consolidation and water release process, which comprises the following steps:

[0052] Step (1): Prepare 5 ring-knife-shaped soil samples with the same dry density, and simultaneously perform saturation treatment;

[0053] Step (2): Place the 5 saturated soil samples into a nuclear magnetic resonance instrument for testing, set a CPMG sequence, collect the relaxation signals of the 5 saturated soil samples in the initial state, use the SIRT model in the nuclear magnetic resonance instrument to invert the obtained relaxation signals, obtain a relaxation spectrum with the horizontal coordinate being the transverse relaxation time T2 and the vertical coordinate being the nuclear magnetic signal intensity M(T2), as the initial state relaxation spectrum. Further, the pore water types are divided to obtain the T2 cutoff value for dividing free water, weakly bound water and strongly bound water;

[0054] Step (3): Place the 5 ring-knife-shaped soil samples in step (2) into a consolidation instrument for one-dimensional saturated consolidation test, apply loads to each soil sample at different levels until the specified stress value is reached, and obtain the pore ratio of the soil sample after consolidation under each stress level;

[0055] Step (4): Place the consolidated soil samples in step (3) into a nuclear magnetic resonance instrument for testing, collect the relaxation signals of the 5 saturated soil samples under different stresses under the same CPMG sequence as in step (2), use the SIRT model in the nuclear magnetic resonance instrument to invert the obtained relaxation signals, and obtain a relaxation spectrum with the horizontal coordinate being the transverse relaxation time T2 and the vertical coordinate being the nuclear magnetic signal intensity M(T2), as the relaxation spectrum under each stress level;

[0056] Step (5): Substitute the T2 cutoff value obtained in step (2) into the initial state relaxation spectrum of step (2) and the relaxation spectrum under each stress level of step (4) to obtain the water content and mass of free water, weakly bound water and strongly bound water under the initial state and each stress level;

[0057] Step (6): Convert the mass of strongly bound water obtained in step (5) to volume and add it to the volume of soil particles to obtain the modified pore ratio considering the solid phase of strongly bound water, and calculate the modified water content considering the strongly bound water in the soil sample consolidation process.

[0058] Further, the ring cutter sample in step (1) has a diameter of 40 mm and a height of 20 mm.

[0059] Further, in step (1), the saturation method is vacuum saturation, and the saturation pressure is -0.8 MPa.

[0060] Further, in steps (2) and (4), the parameters of the CPMG sequence are as follows: center frequency SF=13 MHz, frequency offset O1=43817.57 Hz, 90-degree pulse time P1=25 μs, 180-degree pulse time P2=48 μs, receiver bandwidth SW=250 kHz, radio frequency delay RFD=0.002 ms, repeated sampling interval time TW=8000 ms, analog gain RG1=20 db, digital gain DRG1=2, preamplifier gain PRG=1, number of accumulated samples NS=16, number of echoes NECH=1000, and echo time TE=0.2 ms.

[0061] Further, in steps (2) and (4), the relaxation signal is inverted by using the SIRT model for 100,000 times of iteration to obtain a relaxation spectrum.

[0062] Further, in step (3), the stress is applied in the following order: 59.68 kPa, 238.73 kPa, 716.20 kPa, 954.93 kPa, and 1909.86 kPa.

[0063] Further, in step (3), the void ratio under each level of stress is represented as follows:

[0064]

[0065] wherein e i represents the consolidated stable void ratio of the soil sample under each level of stress; e0 represents the initial void ratio of the soil sample; h0 represents the initial height of the soil sample; and Δh represents the total deformation of the soil sample under each level of stress.

[0066] Further, in step (5), the water content of free water under each level of stress is represented as follows:

[0067] ω fw,i = ω i × α fw,i (2)

[0068] The water content of weakly bound water under each level of stress is represented as follows:

[0069] ω wbw,i = ω i × α wbw,i (3)

[0070] The water content of strongly bound water under various stress levels is expressed as:

[0071] ω sbw,i =ω i ×α sbw,i (4)

[0072] Where, ω i Indicates the moisture content of soil samples under various stress levels; ω fw,i ω represents the water content of free water under various stress levels; wbw,i ω represents the water content of weakly bound water under various stress levels; sbw,i Indicates the water content of strongly bound water under various stress levels; α fw,i Indicates the proportion of NMR signal in free water; α wbw,i Indicates the proportion of NMR signal in weakly bound water; α sbw,i This indicates the proportion of NMR signal in strongly bound water.

[0073] Furthermore, in step (5), the mass of free water under each stress level is expressed as:

[0074] m fw,i =m s ×ω fw,i (5)

[0075] The mass of weakly bound water under various stress levels is expressed as:

[0076] m wbw,i =m s ×ω wbw,i (6)

[0077] The mass of strongly bound water under various stress levels is expressed as:

[0078] m sbw,i =m s ×ω sbw,i (7)

[0079] Where, m s m represents the mass of soil particles. fw,i Let m be the mass of free water under various stress levels; wbw,i The mass of weakly bound water under various stress levels; m sbw,i The quality of strongly bound water under various stress levels.

[0080] Furthermore, in step (6), the corrected void ratio of the soil sample is expressed as:

[0081]

[0082] The change in the corrected void ratio of the soil sample is expressed as:

[0083] Δe i ′ =e0′ -e i ′ (9)

[0084] wherein, e i ′ represents the modified void ratio of soil sample; V s represents the volume of soil particles; p sbw represents the density of strong bound water, taking the value of 1.3 g / cm 3 ; Ae i ′ represents the change amount of modified void ratio of soil sample; e0 ′ represents the modified initial void ratio.

[0085] The modified water content of soil sample is represented as:

[0086]

[0087] wherein, G s represents the specific gravity of soil sample; w t,i ′ represents the modified water content of soil sample under each stress level; w t,0 represents the water content of soil sample in saturated state; p w represents the density of water, taking the value of 1.0 g / cm 3 .

[0088] The technical solution of the present application will be described in detail below.

[0089] The soil samples used in the present embodiment are all taken from the Milin section of the Yarlung Zangbo River Basin in the Qinghai-Tibet Plateau, and are silty clay (S1) and clayey silt (S2) respectively. The vacuum pump device used is a JOANLAB VP-15L; the consolidation apparatus used is a WG type single lever consolidation apparatus; and the nuclear magnetic resonance analyzer with online real-time temperature control function used is a large-size nuclear magnetic resonance analyzer with the model of MacroMR12-150H-I.

[0090] The retrieved soil sample is placed in an oven and dried at a temperature of 105℃ for 24 hours to remove the internal moisture of the soil. After the temperature of the soil sample drops to room temperature, it is fully crushed with a test mallet. A certain mass of the dried soil sample is weighed and placed in a container, a certain amount of deionized water is added to wet the soil sample, and then the soil sample is placed in a specially designed mold and compacted layer by layer to prepare a ring-shaped soil sample. The dry density of the soil sample is set to 1.53 g / cm 3 , and after the compaction of the soil sample is completed, it is saturated in a vacuum saturation device under a pressure of-0.8 MPa for 12 hours.

[0091] The ring knife-shaped soil sample with a diameter of 40 mm and a height of 20 mm is placed in the nuclear magnetic resonance instrument for testing to obtain the relaxation spectrum of the initial saturated state of the soil sample. The CPMG sequence test parameters are as follows: center frequency SF = 13 MHz, frequency offset O1 = 43817.57 Hz, 90-degree pulse time P1 = 25 μs, 180-degree pulse time P2 = 48 μs, receiver bandwidth SW = 250 kHz, radio frequency delay RFD = 0.002 ms, repeated sampling interval time TW = 8000 ms, analog gain RG1 = 20 db, digital gain DRG1 = 2, preamplifier gain PRG = 1, number of accumulated samples NS = 16, number of echoes NECH = 1000, and echo time TE = 0.2 ms. The T2 cutoff values for dividing free water, weakly bound water and strongly bound water are determined according to the spectrum: T 21 and T 22 . Wherein, T 21 is the cutoff value for distinguishing free water and weakly bound water; T 22 is the cutoff value for distinguishing weakly bound water and strongly bound water. The T 21 of the S1 sample is 1.65 ms, and the T 22 is 0.59 ms; the T 21 of the S2 sample is 2.95 ms, and the T 22 is 0.79 ms.

[0092] The ring knife-shaped soil sample after the nuclear magnetic resonance test is placed in a consolidation instrument, and one-dimensional saturated consolidation tests are carried out under stresses of 59.68 kPa, 238.73 kPa, 716.20 kPa, 954.93 kPa and 1909.86 kPa. The deformation of the soil sample is tested by using a dial gauge, and the soil sample is considered to be consolidated and stable when the rate of change of the deformation of the soil sample is less than 0.001 mm / h. The void ratio of the soil sample after consolidation under each stress level is calculated, and the expression is as follows:

[0093]

[0094] Wherein, e i represents the void ratio of the soil sample after consolidation under each stress level; e0 represents the initial void ratio of the soil sample; h0 represents the initial height of the soil sample; and Δh represents the total deformation of the soil sample under each stress level.

[0095] The soil sample after consolidation stabilization is placed in a nuclear magnetic resonance instrument for testing. Among them, the CPMG sequence test parameters are as follows: center frequency SF=13MHz, frequency offset O1=43817.57Hz, 90 degree pulse time P1=25μs, 180 degree pulse time P2=48μs, receiver bandwidth SW=250kHz, radio frequency delay RFD=0.002ms, repeated sampling interval time TW=8000ms, analog gain RG1=20db, digital gain DRG1=2, preamplifier gain PRG=1, number of accumulated samples NS=16, number of echoes NECH=1000, echo time TE=0.2ms.

[0096] The relaxation spectrum is obtained by using the SIRT model in the nuclear magnetic resonance instrument to perform 100,000 iteration times inversion on the obtained relaxation signal, as shown in the following figure. Figure 2 Figure 2 The relaxation spectrum of the soil samples S1 and S2 under different stresses is shown in the following figure, wherein Figure 2 (a) is the relaxation spectrum of the soil sample S1 under different stresses; Figure 2 (b) is the relaxation spectrum of the soil sample S2 under different stresses. From Figure 3 (a)-(b), it can be found that as the stress increases, the relaxation spectrum gradually moves to the left, the nuclear magnetic signal intensity gradually decreases, and the peak value of the relaxation spectrum gradually moves to the left. The types of pore water in the soil sample are divided in combination with the T2 cutoff value, and the nuclear magnetic signal intensity of each type of pore water under different stresses is obtained.

[0097] The proportion of the nuclear magnetic signal intensity of free water (fw) is represented as:

[0098]

[0099] The nuclear magnetic signal intensity of weakly bound water (wbw) is represented as:

[0100]

[0101] The nuclear magnetic signal intensity of strongly bound water (sbw) is represented as:

[0102]

[0103] Wherein, α fw,i represents the proportion of the nuclear magnetic signal of free water; α wbw,i represents the proportion of the nuclear magnetic signal of weakly bound water; α wbw,i represents the proportion of the nuclear magnetic signal of strongly bound water; M fw,i represents the nuclear magnetic signal intensity of free water; M wbw,i represents the nuclear magnetic signal intensity of weakly bound water; M sbw,i represents the nuclear magnetic signal intensity of strongly bound water; M iotal,i represents the total nuclear magnetic signal intensity;​

[0104] The mass water content of free water under various stress levels is expressed as:

[0105] ω fw,i =ω i ×α fw,i (5)

[0106] The mass water content of weakly bound water under various stress levels is expressed as:

[0107] ω wbw,i =ω i ×α wbw,i (6)

[0108] The mass water content of strongly bound water under various stress levels is expressed as:

[0109] ω sbw,i =ω i ×α sbw,i (7)

[0110] Where, ω i Indicates the mass moisture content of soil samples under various stress levels; ω fw,i ω represents the mass water content of free water under various stress levels; wbw,i ω represents the mass water content of weakly bound water under various stress levels; sbw,i This indicates the mass water content of strongly bound water under various stress levels.

[0111] The mass of free water under various stress levels is expressed as:

[0112] m fw,i =m s ×ω fw,i (8)

[0113] The mass of weakly bound water under various stress levels is expressed as:

[0114] m wbw,i =m s ×ω wbw,i (9)

[0115] The mass of strongly bound water under various stress levels is expressed as:

[0116] m sbw,i =m s ×ω sbw,i (10)

[0117] Where, m s m represents the mass of soil particles. fw,i Let m be the mass of free water under various stress levels; wbw,i The mass of weakly bound water under various stress levels; m sbw,i The quality of strongly bound water under various stress levels.

[0118] Schematic diagram of mass change of different types of pore water under various stress levels is shown below. Figure 3 As shown. Among them Figure 3 (a) is a schematic diagram of the mass change of different types of pore water in soil sample S1 under various stress levels; Figure 3 (b) is a schematic diagram showing the mass change of different types of pore water in soil sample S2 under various stress levels. From Figure 4 As can be seen in (a)-(b), the soil sample continuously compresses and releases water under stress. Specifically, the mass of free water gradually decreases with increasing stress. The mass of weakly bound water remains almost unchanged in the early stage of stress and does not participate in water release; however, in the later stage of stress, the mass of weakly bound water gradually decreases and participates in water release. Due to the strong adsorption of soil particles, the mass of strongly bound water remains almost unchanged and does not participate in water release at all.

[0119] The mass of strongly bound water is converted to volume and included in the volume of soil particles to obtain the corrected void ratio of the soil sample. Its expression is:

[0120]

[0121] The change in the corrected void ratio of the soil sample is expressed as:

[0122] Δe i ′ =e0 ′ -e i ′ (12)

[0123] Among them, e i ′ Indicates the corrected void ratio of the soil sample; V s ρ represents the volume of soil particles; sbw This represents the density of strongly bound water, with a value of 1.3 g / cm³. 3 ;Δe i ′ Indicates the amount of change in porosity; e0 ′ This indicates a correction to the initial void ratio.

[0124] The water content of the soil sample after correction is calculated based on the corrected void ratio, and the expression is as follows:

[0125]

[0126] Where, ω t,i ′ Indicates the corrected moisture content of soil samples under various stress levels; ω t,0 G represents the water content of a soil sample under saturated conditions. s ρ represents the specific gravity of the soil sample. w This represents the density of water, with a value of 1.0 g / cm³. 3 .

[0127] The corrected moisture content was compared with the test results, and the results are as follows: Figure 4 As shown. Figure 4 (a) and (b) show the relationship between water content and void ratio variables in soil samples S1 and S2 under various stress levels, respectively. It can be seen that... ​ In the experiment, the soil moisture content gradually decreased with the increase of the void ratio variable. The experimental data appeared more near the correction curve, and the slope of the curve obtained by fitting the experimental data was also significantly smaller than the slope of the curve before correction. This also shows that the traditional method of simplifying pore water will underestimate the water release quality of saturated clay, thus resulting in poor prediction of soil settlement in actual engineering.

[0128] This application combines consolidation apparatus and nuclear magnetic resonance technology to obtain data on the changes in pore water quality under different stresses, and quantifies the water release mechanism of the consolidation process of saturated clay from a microscopic perspective, thereby improving the accuracy of calculating the settlement of soil and rock masses under stress.

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of quantifying the process of water release from saturated clays consolidation, characterized in that, The method comprises the following steps: Step (1) five ring knife-shaped soil samples with the same dry density are prepared, and saturation treatment is simultaneously performed; Step (2) the five saturated soil samples are placed into a nuclear magnetic resonance instrument for testing, a CPMG sequence is set, relaxation signals of the five saturated soil samples in an initial state are collected, the SIRT model in the nuclear magnetic resonance instrument is used to perform inversion on the obtained relaxation signals, a relaxation spectrum with the horizontal coordinate being the transverse relaxation time T2 and the vertical coordinate being the nuclear magnetic signal intensity M(T2) is obtained, and the relaxation spectrum is taken as an initial state relaxation spectrum. Further, pore water types are divided, and T2 cutoff values for dividing free water, weakly bound water and strongly bound water are obtained; Step (3) the five ring knife-shaped soil samples in step (2) are respectively placed into a consolidation instrument for one-dimensional saturated consolidation testing, a load is applied to each soil sample in stages to a specified stress value, and the pore ratio of the soil sample after consolidation stabilization under each stage stress is obtained; Step (4) the soil sample consolidated and stabilized in step (3) is placed into the nuclear magnetic resonance instrument for testing, relaxation signals of the five saturated soil samples under different stresses are collected under the same CPMG sequence as that in step (2), the SIRT model in the nuclear magnetic resonance instrument is used to perform inversion on the obtained relaxation signals, a relaxation spectrum with the horizontal coordinate being the transverse relaxation time T2 and the vertical coordinate being the nuclear magnetic signal intensity M(T2) is obtained, and the relaxation spectrum is taken as a relaxation spectrum under each stage stress; Step (5) the T2 cutoff values obtained in step (2) are substituted into the initial state relaxation spectrum in step (2) and the relaxation spectra under each stage stress in step (4), and the water content and mass of the free water, weakly bound water and strongly bound water in the initial state and under each stage stress are obtained; Step (6) the mass of the strongly bound water obtained in step (5) is converted into a volume and added to the volume of the soil particles, a modified pore ratio considering the solid phase of the strongly bound water is obtained, and the modified water content of the soil sample in the consolidation process considering the strongly bound water is calculated.

2. The method of claim 1, wherein, In step (1), the diameter of the ring knife-shaped sample is 40 mm, and the height is 20 mm.

3. The method of claim 1, wherein the saturated clay consolidation process is a process of water release from a saturated clay. In step (1), the saturation method is vacuum saturation, and the saturation pressure is -0.8 MPa.

4. The method of claim 2 and claim 4, wherein, In steps (2) and (4), the parameters of the CPMG sequence used are as follows: center frequency SF=13 MHz, frequency offset O1=43817.57 Hz, 90-degree pulse time P1=25 μs, 180-degree pulse time P2=48 μs, receiver bandwidth SW=250 kHz, radio frequency delay RFD=0.002 ms, repetition sampling interval time TW=8000 ms, analog gain RG1=20 db, digital gain DRG1=2, preamplifier gain PRG=1, number of accumulated samples NS=16, number of echoes NECH=1000, and echo time TE=0.2 ms.

5. The method of claim 2 and claim 4, wherein, In steps (2) and (4), the SIRT model is used to perform inversion on the relaxation signals for 100,000 times of iteration to obtain the relaxation spectrum.

6. The method of claim 3, wherein the saturated clay consolidation process is a process of water release. In step (3), the order of the applied stress is as follows: 59.68 kPa, 238.73 kPa, 716.20 kPa, 954.93 kPa, and 1909.86 kPa.

7. The method of claim 3, wherein the saturated clay consolidation process is a process of water release. In the step (3), the void ratio under each stress level is expressed as: where e i represents the pore ratio of the soil sample under the consolidation stability of each stress level; e0 represents the initial pore ratio of the soil sample; h0 represents the initial height of the soil sample; and Δh represents the total deformation of the soil sample under each stress level.

8. The method of claim 5, wherein the saturated clay consolidation process is a process of water release. In the step (5), the water content of free water under each stress level is expressed as: ω fw,i = ω i x α fw,i (2) The water content of weakly bound water under each stress level is expressed as: ω wbw,i = ω i x α wbw,i (3) The water content of strongly bound water under each stress level is expressed as: ω sbw,i = ω i × α sbw,i (4) wherein ω i represents the water content of the soil sample under each stress level; ω fw,i represents the water content of free water under each stress level; ω wbw,i represents the water content of weakly bound water under each stress level; ω sbw,i represents the water content of strongly bound water under each stress level; α fw,i represents the proportion of the nuclear magnetic signal of free water; α wbw,i represents the proportion of the nuclear magnetic signal of weakly bound water; α sbw,i represents the proportion of the nuclear magnetic signal of strongly bound water.

9. The method of claim 8, wherein the saturated clay consolidation process is a process of water release from a saturated clay. In the step (5), the mass of free water under each stress level is expressed as: m fw,i = m s x ω fw,i (5) The mass of weakly bound water under each stress level is expressed as: m wbw,i = m s x ω wbw,i (6) The mass of strongly bound water under each stress level is expressed as: m sbw,i = m s x ω sb,i (7) where m s is the mass of soil particles; m fw,i is the mass of free water under each stress level; m wbw,i is the mass of weakly bound water under each stress level; m sbw,i is the mass of strongly bound water under each stress level.

10. The method of claim 9, wherein the saturated clay consolidation process is a process of water release from a saturated clay. In the step (6), the corrected void ratio of the soil sample is expressed as: The change amount of the corrected void ratio of the soil sample is expressed as: Δe i ′ = e0' - e i ′ (9) where e i ′ represents the modified void ratio of the soil sample; V s represents the volume of the soil particles; p sbw represents the density of the strongly bound water, and has a value of 1.3 g / cm 3 ; Δe i ′ represents the change in the modified void ratio of the soil sample; e0′ represents the modified initial void ratio; The corrected water content of the soil sample is expressed as: where G s represents the soil sample specific gravity; ω t,i ′ represents the soil sample modified moisture content under each stress level; ω t,0 represents the soil sample moisture content under saturated conditions; ρ w represents the water density, which is taken as 1.0 g / cm 3 .

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