Method for predicting soil-water characteristic curve VG (Van Genuchten) model on the basis of NMR (Nuclear Magnetic Resonance) curve

A water characteristic curve and curve technology, applied in the field of predicting soil-water characteristic curve VG model based on NMR curve, can solve problems such as long investment time and inability to eliminate dry density, and achieve the effect of overcoming limitations and saving manpower and material resources

Inactive Publication Date: 2019-01-18
HUBEI UNIV OF TECH
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Problems solved by technology

However, there are certain limitations in indoor experiments, mainly because the investment time is too long
There are also predictions based on fractal theory and nuclear magnetic resonance technology, but it cannot eliminate the lack of high accuracy caused by the inconspicuous fractal behavior when the dry density is small

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  • Method for predicting soil-water characteristic curve VG (Van Genuchten) model on the basis of NMR (Nuclear Magnetic Resonance) curve
  • Method for predicting soil-water characteristic curve VG (Van Genuchten) model on the basis of NMR (Nuclear Magnetic Resonance) curve
  • Method for predicting soil-water characteristic curve VG (Van Genuchten) model on the basis of NMR (Nuclear Magnetic Resonance) curve

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Embodiment Construction

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0041] In NMR experiments, the transverse relaxation time T 2 It is not only related to the pore water in the saturated soil sample, but also affected by the pore structure of the soil sample. For completely liquid water, if the pore shape is approximated as a sphere, the transverse relaxation time T 2 The relationship with the radius is:

[0042]

[0043] According to the Young-Laplace equation, the matrix suction ψ is inversely proportional to the effective pore size r:

[0044]

[0045] In the formula: T s Indicates the surface tension; α indicates the contact angle, when the temperature is constant, 2T s cosα can be regarded as a fixed value.

[0046] According to formulas (5) and (6), the following formulas can be deduced:

[0047]

[0048] In the formula: A is equal to 2T s cos α / 3ρ.

[0049] It can be seen fro...

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Abstract

The invention discloses a method for predicting a soil-water characteristic curve VG (Van Genuchten) model on the basis of an NMR (Nuclear Magnetic Resonance) curve. Under known dry density, accordingto experiment data, a relationship curve, i.e., a magnetic resonance imaging curve of the soil mass relaxation time T2-semaphore S of the soil-water characteristic curve is obtained under the same dry density, a part which is smaller than an actual measurement residual mass moisture content is detected, and the obtained processed magnetic resonance imaging curve carries out fitting on the basis of the VG model of a classical soil-water characteristic curve model to obtain a fit parameter to obtain N groups of fitting parameters under N different dry densities to establish a prediction model of the soil-water characteristic curve parameter. Therefore, the boundedness of an indoor experiment is overcome, a great quantity of manpower and material resources can be saved, a new direction is provided for researching the soil-water characteristic curve of unsaturated soil, and the method has important scientific significance for developing the relevant mechanics and penetration theory of theunsaturated soil.

Description

technical field [0001] The invention belongs to the field of soil-water characteristic curve research and nuclear magnetic resonance technology of unsaturated soil in geotechnical engineering, and specifically relates to a method for predicting a soil-water characteristic curve VG model based on NMR curves. Background technique [0002] Nuclear Magnetic Resonance technology appeared in the 20th century. The detection of pore structure has the advantages of non-destructive, fast and intuitive display, and is favored by geotechnical scholars. At present, in the known theory, the NMR curve (T 2 Spectrum) can well reflect the pore size distribution of the internal pore structure of the object. Therefore, the NMR curve of the soil sample can be used to know the distribution characteristics of the internal pore volume-pore diameter of the soil sample. [0003] Soil-water characteristic curve (SWCC for short) reflects the relationship between matric suction and water content in u...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N24/08
CPCG01N24/081G01N24/082
Inventor 陶高梁彭弯肖衡林马强李丽华朱志政付佩罗晨晨陈阳阳张琎炜
Owner HUBEI UNIV OF TECH
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