Magnetic Properties Influence of Various Parameters Methods of - - PowerPoint PPT Presentation

2.11.2018 Lecture No. 25 Lecture Name: Geomaterial Characterization

Sub-topics

• Magnetic Characterization
• Importance
• Magnetic Properties
• Influence of Various Parameters
• Methods of Measurement
• Generalized Relationships
• Dielectric constant
• Topp’s Equation

IIT Bombay

• Thermo gravimetric
• Calcium carbide
• Infrared moisture balance
• Neutron Scattering
• Gamma attenuation
• Heat pulse sensors
• Micro-Electro-Mechanical
• Optical
• Time Domain Reflectometric
• Capacitance technique

Classical Techniques Modern Techniques

Determination of Soil Moisture Content

Critical Appraisal

• Dielectric techniques have been found to be the most contemporary

techniques

• Multi-phase mineralogical composition of the soil
• Magnetic effect of the soil
• The applicability to soils of entirely different characteristics
• No holistic approach for obtaining soil moisture content

3

Susha Lekshmi S.U., D. N., Singh and Maryam S Baghini. (2014). "A Critical Review

• f Soil Moisture Measurement", Measurement, Vol. 54, pp: 92-105

Basic ic Philo ilosophy

Soil Moisture content= f(dielectric constant) Influence of soil magnetism Comparison of TDR and CT techniques

Influence of soil magnetic characteristics

• Vibrating Sample Magnetometer
• -3 Tesla to 3 Tesla @ ambient temperature
• 8000 -6000 -4000 -2000

2000 4000 6000 8000

• 0.2
• 0.1

0.0 0.1 0.2

Irregularities

Trial 1 Trial 2 M (emu/g)

H (Oe)

Reproducible results

AH Magnetic moment, M (emu/g) Saturation Magnetization (SM) Magnetic field, H (Oe) Remnant Magnetization (+RM) Coercivity (-CR)

• RM

+CR AH

6

• 30000
• 15000

15000 30000

• 0.8
• 0.4

0.0 0.4 0.8

M (emu/g)

H (Oe) Standard Oxide

Fe2O3 Al2O3 SiO2

Magnetic response of pure metal oxides Fe2O3 exhibits magnetic hysteresis

7

Susha Lekshmi S. U., Singh, D.N., Tarantino, A. and Baghini, M.S., “Investigations on Magnetic Characteristics of the Soil and their Influence on its Dielectric Response”, Applied Clay Science, 2018, 158, pp. 113-122.

10

• 3

10

• 2

10

• 1

10 10

1

10

2

10

3

4 8 12 16 20

Ka-mineral

AH

Ka-mineral=10AH

0.05

0.3<AH <5 AH >5 AH <0.3

Relationship between AH, Ka-mineral, Ka-Expt and θ

Comparis ison of dif ifferent die iele lectric techniq iques

8 TDR probe TDR waveform Compacted soil mass

Step pulse generator, Oscilloscope and timing device

TDR: Campbell scientific TDR CS 640 Capacitance Technique: Decagon Device 5TE

• TDR and Capacitance techniques

Comparison of (a) θCT with θTDR and (b) σa-CT with σa-TDR

1000 2000 3000 4000 5000 1000 2000 3000 4000 5000

CT (S/cm)

R2=0.91  CT =1.25 TDR

TDR (S/cm)

SOIL

S1 d=1.2g/cc S2 d=1.2g/cc S3 d=1.3g/cc S4 d=1.3g/cc S5 d=1.1g/cc

(b)

20 40 60 80 100 20 40 60 80 100 R2= 0.98

 CT = 0.58 TDR

TDR CT

(a) (%) (%)

10

Variation of (a) Ka-TDR, (b) Ka-CT with θc

Soil, d (in g/cc) S1, 1.2

S2, 1.2 S3, 1.3 S4, 1.3 S5, 1.1

20 40 60 80 100 20 40 60 80

R2= 0.92 Ka-TDR = 5.1 e0.04c

Ka-TDR (a)

20 40 60 80 100 20 40 60 80 R2= 0.87 Ka-CT = 4.09 e0.03c

Ka-CT (b)

θc

𝐿a−TP = 1 − ƞ · 𝑁1 · 𝐿𝑁1 + 𝑁2 · 𝐿𝑁2 + ƞ · 𝑇𝑠 · 𝐿𝑄𝐺1 + 1 − 𝑇𝑠 · 𝐿𝑄𝐺2

Comparison of the dielectric constants obtained from different methods

20 40 60 80 20 40 60 80

R

2=0.98

Ka-Topp=0.82Ka-TDR Ka-TDR Ka-Topp (a) 45 line

20 40 60 80 20 40 60 80 R

2=0.96

Ka-Topp= 1.64Ka-CT

Ka-CT Ka-Topp (b) 45 line

20 40 60 80 20 40 60 80

Ka-Topp = 0.75 Ka-TP

Ka-Topp Ka-TP (c) 45 line

20 40 60 80 20 40 60 80

R2=0.98 Ka-CT=0.45Ka-TP

Ka-CT Ka-TP (d) 45 line

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Comparison of the dielectric constants obtained from different methods

20 40 60 80 20 40 60 80 R2=0.95 Ka-TDR=0.89Ka-TP

Ka-TDR

Ka-TP

(e) 45 line