Mitigation of Expansive Soils Damages
Joseph Muhirwa Richard Benda Robert Sargent
REU Program University of Texas at Arlington
This presentation will focus on four main sections
Introduction and Background
Experimental Program
Results and Conclusion
Additional Work
Introduction and Background
Experimental Program
Results and Conclusion
Additional Work
Clay is the most common particle that makes soils expansive because of its ability to retain large amounts of water.
Very fine particles (less than 2 microns) Large surface area (plates with negative charge)
Kaolinite Montmorillonite Illite
How expansive clay is depends on the minerals in the clay
Montmorillonite is the most expansive mineral. One pound of it can have a surface area of 800 acres.
Expansive soil behaves like a sponge. It expands when it soaks up water and then shrinks back down when it loses water
Water being attracted to the negatively charged clay plates
The damage to infrastructure by expansive soils costs close to 9 billion dollars per year
structural damage
Pavement uplift and cracking
Slope failure
Austin, Texas is located in an area of highly expansive soil
Austin
USGS (1989)
The main objective of our research was to understand the concepts behind soil stabilization and determine the best percentage of lime to stabilize our soil
UCS
Introduction and Background
Experimental Program
Results and Conclusion
Additional Work
1. Atterberg Limits Test
The Swelling Potential of Expansive soils Can be determined indirectly from Atterberg Limits
Liquid Limit(LL) Plastic Limit (PL)
Plastic index (PI)
PI=LL-PL
(ASTM 4318)
2. Determination of Sulfate Content
Ettringite formation, Heave-inducing crystal, can be avoided by checking the sulfate content
of Soil before lime stabilization
Day 1: Sample Preparation
Day 2: Filtration and Precipitation
Day: Precipitate Filtration
Day 4: Final Weight of Soluble Sulfate
Modified UTA method (2000)
On the first day, Pulverization and Dilution of the soil are performed
1:10 Dilution
Modified UTA method (2000)
On the second day, Stirring, centrifigution and Filtration of the soil solution are the major tasks
Modified UTA method (2000)
On the Third day, The filtration of the precipitate solution is performed
Start/End
Modified UTA method (2000)
On the Fourth Day, The final Weight of the dry precipitate is determined.
Removal Of Weighing Tin and precipitate from the oven
Modified UTA method (2000)
3. Additive Selection/ Mix Design
Samples with different % of lime are tested to determine the most effective amount of lime
Common % of Lime: 3%-8%
Required mellowing time: at least 24 hrs
OMC of control soil is the starting point
Nelson and Miller (1992)
4. One-Dimensional Swell Test
A Direct Indication of Swell Potential can be obtained through 1-D Swell Test
(ASTM 4546)
5. Unconfined Compressive Strength Test
The UCS Test helps to estimate the strength of Treated and Non-Treated Soils
Extrusion
Unconfined Compression
Introduction and Background
Experimental Program
Results and Conclusion
Additional Work
1.Results and Discussion
Austin’s soil was found to be a high-plasticity clay
51.00
51.50
52.00
52.50
53.00
53.50
0 5 10 15 20 25 30
Moi
stur
e co
nten
t (%
)
Number of blows
Moisture content vs. Number of blows
Soil Property Results Liquid Limit (LL) 51.04% Plastic Limit (PL) 19.76% Plasticity Index (PI=LL-PL)
30.84%
USCS Classification CH
Sample 1 Sample 2 Sample 3
*W1 (grams) 1.2116 1.2198 1.2156
*W2 (grams) 1.2182 1.2263 1.2216
Sulfate content (ppm) 271.63 267.514 246.936
Avg. Sulfate content
(ppm)
261
The Sulfate content was within the Acceptable range
W1 = Mass of weighing tin and filter paper W2 = Mass of weighing tin, filter paper, and precipitate
1Puppala et al. (1999) and Viyanat (2000)
Acceptable Range = 1000 to 2000 ppm1
00.005
0.010.015
0.020.025
0.030.035
0.040.045
0.050.055
0.060.065
0.070.075
0.08
0.001 0.01 0.1 1 10 100
disp
lace
men
t (in
)
Time (hr)
Time vs. Displacement
0 percent2 percent4 percent6 percent
All of the specimens with lime performed better than the control sample
In the time-displacement curve, 6% was observed to have reduced swell the most
The 6% lime sample had the overall highest strength
In general, all lime treated samples had a higher shear strength than the control
Stiffer and softer specimens 0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 0.5 1 1.5 2 2.5 3 3.5 4
Stre
ss, σ
(lb/
ft2)
Axial Strain, ԑ (%)
Stress vs. Axial Strain Austin's soil with 0%limeAustin's soil with 2%limeAustin's soil with 4%lime Austin's soil with 6%Lime
qu =8061 lb/ft2
qu = 7368 lb/ft2
qu =4952 lb/ft2
qu =3433 lb/ft2
2. Conclusions
Performance benefits from lime stabilization reduce maintenance costs
6% lime and 4% lime were found to be suitable to reduce swelling and increase bearing capacity
• 4% lime could be used in situations requiring reduced cost • 6% lime could be used in situations requiring additional
strength
For future research, additional additives could be tried in combination with lime (such as cement)
+ =
Introduction and Background
Experimental Program
Results and Conclusion
Additional Work
1.Field Stabilization
Reduction of Slope and Embankment Failure at Grape Vine and Joe Pool Lakes
Slope Testing Area
Monitoring of Horizontal Movement by Inclinometer
Monitoring of vertical Movement by surveying
2. Three-Dimensional Swell Test
The 3-D Swell Test can be Conducted Using Double Inundation
Lime Stabilization reduces the swelling potential considerably
3. Hydrometer Test
The size Distribution of Silt and Clay can be Obtained through Hydrometer Test
References • Anand J. Puppala et al. (1999). Evaluation of a Sulfate Induced Heave by
Mineralogical and Swell Tests. XI Pan-American Conference on Soil Mechanics and Geotechnical Engineering, Foz do Igacu, Brazil.
• Anand J. Puppala et al. (2002). Evaluation of a Modified Soluble Sulfate Determination Method for Fine-Grained Cohesive Soils. ASTM International, West Conshohocken, PA.
• ASTM. (n.d.). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, ASTM D4318, West Conshohocken, PA.
• ASTM. (n.d.). Standard Test Methods for One-Dimensional Swell or Settlement Potential of Cohesive Soils, ASTM D4546-96, West Conshohocken, PA.
• Miller, D. J., Nelson, J. D. (1992). Expansive Soils: Problems and Practice in Foundation and Pavement Engineering, John Wiley & Sons, Inc., Toronto, Canada.
• Viyanant, C., (2000). Laboratory Evaluation of Sulfate Heaving Mechanisms Using Artificial Kaolinite Soil. Masters thesis, The University of Texas at Arlington, TX.
Acknowledgements
We are very grateful to all the people who made this research possible, especially Dr. Anand Puppala, Dr. Nur Yazdani, Dr. Yvette Weatherton, Dr. Stephanie Daza,Mr. Aravind Pedarla, Mr. Justin Thomey, Mr. Minh Lee and Mr. Naga Talluritinnu.
Questions???????
