Transparent soils are 2-phase media made by RI matching of solids representing the soil skeleton and the saturating fluids.
Transparent materials can be produced ,which exhibits macroscopic properties which is in consistent with natural soils.
Useful tool for : physical modelling,3-D deformation patterns, flow characteristics and soil structural interaction problem.
2. WHAT,WHY,HOW,….?
• Transparent soils are 2-phase media made by RI matching of solids
representing the soil skeleton and the saturating fluids.
• Transparent materials can be produced ,which exhibits macroscopic
properties which is in consistent with natural soils.
• Useful tool for : physical modelling,3-D deformation patterns, flow
characteristics and soil structural interaction problem.
3. • Materials mainly used for making transparent “soils” are:
Amorphous silica (clay)
Silica gel(sand)
Hydrogel(marine deposits)
Fused quartz(saturated and unsaturated sands)
• Uses non intrusive visual techniques to view the spatial deformation
which involves interaction between LASER LIGHT and transparent
soils
4. PREPARATION OF TRANSPARENT SOIL
• Amorphous silica powder material made up of tiny particles with
diameter of .02µm produce by the commercial company of PPG
industries 1996
• The physical properties of four different silica ranging from 1.4 to175
µm as show in the table below
6. • Amorphous silica powders, Flo-Gard SP and Hi-Sil T600, were used
for the preparation of transparent media.
• The silica had a bulk density of 65 to 100 kg/m3and a moisture content
of 6 to 7%.
• The reported specific gravity was 2.1, and the median aggregate size
was 25µm for Flo-Gard SP and 1.6 µm for Hi-Sil T 600 (PPG 1990).
• An oil blend or a brine mixture was mixed with amorphous silica to
form a transparent suspension
• The oil was blended from a white mineral oil and a normal-paraffinic
solvent
• The viscosity and density of the oil blend at room temperature 23°C
were 0.005 Pa.s and 804 kg/m3, respectively
7. • The brine mixture was blended from calcium bromide and water
• The viscosity and density of the brine mixture at room temperature
were 0.0036 Pa.s and 1572 kg/m3 respectively.
• Suspensions of either 25 or 1.6µm silica aggregates were made by
dispersing the silica in either the oil or brine mixtures using a low-
speed mixer.
• After mixing, the suspension was transferred into a one-
dimensional consolidometer.
• One-dimensional consolidation pressures ranging between 70 and
700 kPa were applied
8. • The consolidated samples were approximately 6.4 cm in diameter and 9
cm long.
LABORATORY TEST PROGRAM
• Consolidation and triaxial compression tests were performed on
specimens trimmed from the consolidated samples
• A computer based data acquisition system was used to record all
measurements.
• The initial and final total void ratios of the tested specimens are
summarized in Table given below.
9. Test No: Average
Silica
Size (µ)
Pore
Fluid
Consolidat
ion
Pressure
(kPa)
Initial Unit
Weight
(kN/m3)
Initial
Total
Void Ratio
Final
Total
Void Ratio
CU1 25 Oil 420 9.6 ….. 6.5
CU2 25 Oil 140 9.4 7.2 5.8
CU3 25 Oil 280 9.4 5.6 4.8
CU4* 25 Oil 105 9.6 8.1 …
CD1 25 Oil 280 9.4 5.7 4.4
CD2 25 Oil 140 9.4 7.0 4.8
CD3 1.6 Oil 135 9.4 7.9 6.2
CD4 1.6 Oil 140 9.4 7.4 5.1
CD5 25 Brine 140 16 7.0 5.3
Consoli 25 Oil 140 9.4 6.4 3.4
Table 2.2 Properties of specimens (Magued G. Iskander,1994)
10. • The interaggregate void ratio is more representative than the total
void ratio for geotechnical purposes.
• The interaggregate void ratio was estimated using the measured
hydraulic conductivity and the average estimated aggregate size in the
Blake-Kozeny equation as follows
3
11. • The interaggregate void ratios ranged between 0.1 and 0.4, which is 10
to 50 times smaller than the corresponding total void ratios.
• The computed interaggregate void ratios are somewhat smaller than
the void ratios of most natural soils.
Target (under glass dish) viewed through a thick transparent soil
sample. Sample [6.25 cm (2.5 in.) in diameter and 8.25 cm
thick].(Adopted from iskander et al 1994)
12. • The third family of transparent soils was developed using a water
based transparent polymeric hydrogel called aquabeds.
• Aquabeds are helpful in studying flow of water in soil and very weak
marine deposits.
• New transparent families introduced are fused quartz (2010) best
suited for saturated and unsaturated sands (2015) suitable for marine
clays.
13. CONSOLIDATION TESTS
• Specimen was trimmed from a sample consolidated to 140kPa from a
slurry of 25µm amorphous silica and oil
• The test was performed according to ASTM test method for
1-D consolidation properties of soil
• Comparison between theoretical time settlement curves and measured
time settlement curve indicate that large secondary consolidation
occurs
• Two consolidation process take place when a load is applied-first
consolidation process involve pores between the silica aggregate,
second pores inside the silica aggregate
14. Fig 2.2 One dimensional consolidation of a specimen made from 25
amorphous silica and blended mineral oil ( iskander et al 1994).
15. • The compression and recompression indices (Cc and Cr) are 1.6–3.0
and 0.15–0.3, respectively both indices are within the range typically
reported for clay Montmorillonite minerals.
• The coefficients of consolidation of the specimen ranged between
0.001 and 0.002 cm2/s which is comparable with reported values of
natural clay
16. Fig 2.1 One-dimensional consolidation of a specimen made from 25μm amorphous silica
and blended mineral oil ( iskander et al 1994).
17. Permeability tests:
• Constant head permeability test where performed before extracting the
soil sample from consolidometer
• The sample where permeated with the same oil used to manufacture
the sample
• Hydraulic conductivities ranging between 2.3 × 10-7 to 2.5 × 10 -5
cm/s were measured which are in range typically reported for clays
and silt.
18. FIG 2.3 Effect of consolidation pressure and particle size on
permeability to blended mineral oil ( iskander et al 1994).
19. TRIAXIAL TEST
• Both CD and CU where performed
• Specimen 3.8 cm in diameter and 7.5 cm long were trimmed from the
consolidated sample
• Specimen were consolidated to a confining pressure equal to the one
dimensional consolidation pressure
• CONSOLIDATED-UNDRAINED TRIAXIAL TEST
• Test were performed according to ASTM test method for CU triaxial
compression test on cohesive soil
• The specimen was sheared at deformation rate of 0.46 cm/hr.
20. FIG 2.4 Consolidated Undrained Triaxial Test – stress strain diagram
(iskander et al 1994)
21. • No strain softening was observed
• The stress-strain curves are typical of normally consolidated clays
and very loose sand
• Maximum excess pore pressure 45 to 65% of confining pressure
• Maximum excess pore pressure and the strain at which it occurred
increased with confining pressure which is similar to soft clay
22. FIG 2.5 Consolidated Undrain Triaxial Test –Excess pore fluid pressure
generated during shear (iskander et al 1994)
23. CONSOLIDATED DRAINED TRIAXIAL TEST
• Specimen was sheared at a deformation rate of 0.071cm/hr.
• No strain softening was observed at strain as high as 20%
• The shape of the volumetric strain curve during shear typical of soft
clay and very loose sand
• silica aggregate are more deformable than solid particle in actual soil
when subjected to shear stress
• Transparent soil aggregate resemble to flocculated clay soil which can
deform into tightly packed arrangement under loading
24. FIG 2.6 Consolidated Drain Triaxial Test – Stress – strain diagram
(iskander et al 1994)
25. Fig 2.7 Consolidated Drain Triaxial Test – Volumetric strain
during shearing (iskander et al 1994)
26. Geotechnical Characteristics of Transparent
soil
TOTAL STRESS EFFECTIVE STESS
C (KPa) Φ º C!( kPa) Φ! º
Coarse silica 17 21º 20 36º
Fine silica ………. …………. 23 32º
Table 2.3 Shear strength of transparent synthetic soil (iskander et al 1994)
27. • The stress strain behavior and volumetric strain during shear strength
tests are characteristic of soft normally consolidated clays
• The shear strength parameters obtained in the tests are C=17KPa and
Φ=21º(total stress), 𝑐 ̅= 20KPa and Φ=36º(effective stress) which are
comparable with reported values of clays.
29. pioneering studies were conducted:
• Flow properties around PVD’s (1999)
• Deformations due to pile penetration(2004)
• Centrifuge tests to model offshore foundations(2009).
• The second family of transparent soils developed was silica gel,
suitable to model the static and dynamic behavior of sand.(2003)
• Silica gel used for modelling of pile penetration, shallow foundations
and studies on tunneling.
30. AREAS OF MODELLING USING
TRANSPARENT SOIL
• Soil structure interaction
• Tunneling induced movements
• 3-D flow and geo-environmental contaminant problems.
• Centrifuge models
• Unsaturated soil
• Vibrated stone columns.
31. CONCLUSION
• Application of transparent soil have an effectively contributions on
soil investigations for many geotechnical problem
• This come due to the easy visibility inside the soil body.
• The development of transparent soil with mechanical and hydraulic
properties of natural soil is a first step toward the use of optical
techniques to study spatial deformation patterns and the flow
characteristics
• First techniques to manufacture large transparent soil specimens which
can represent 3D soil properties must be developed.
32. • Second addition research is required to characterize the geotechnical
properties of the transparent soil under over consolidated condition.
• Third research is required to improve the visibility of transparent soil
sample as they are subjected to standard soil test such as the triaxial
test
• Finally measuring spatial deformation pattern within transparent soil
under load.
33. REFERENCE
• Iskander, M. G., Lai, J., Oswald, C. J., and Mann-heimer, R. J., "Development of a Transparent
Material to Model the Geotechnical Properties of Soils," Geotechnical Testing Journal,GTJODJ,
Vol. 17, No. 4, December 1994, pp. 425-433.
• Qi, C.-G., Zheng, J.-H., Zuo, D.-J., and Liu, G.-B., “Experimental Investigation on Soil
Deformation Caused by Pile Buckling in Transparent Media,” Geotechnical Testing Journal.
• Iskander, M., Bathurst, R. J., and Omidvar, M., “Past, Present, and Future of Transparent
Soils,” Geotechnical Testing Journal, Vol. 38, No. 5, 2015, pp. 557–573,
• Jinyuan Liu, Visualization of 3-D deformations using transparent “soil” models,PhD thesis
