RESEARCH POSTER PRESENTATION DESIGN © 2011 www. ... To study,
analyze, and classify expansive soils. • To understand the problematic nature of
expansive soils and ... The stabilization of Austin's expansive soil involved
several ...
Lime Stabilization of Expansive Soils Joseph Desire Muhirwa
Richard Benda
Robert Sargent
Aravind Pedarla
Dr Anand Puppala
California Baptist University Civil Engineering
New Mexico Tech Civil Engineering
California Baptist University Civil Engineering
University Of Texas at Arlington PhD Student
University of Texas at Arlington Faculty, Geotechnical Engineering
Methods and Procedure
• To study, analyze, and classify expansive soils. • To understand the problematic nature of expansive soils and the damages resulting from it. • To learn about the different methods used in lime stabilization of expansive soils and how they work. • To determine the most effective amount of lime to stabilize an expansive soil.
TxDOT Flow chart for Subgrade Soil Stabilization
Introduction Soils with high amounts of clay particles tend to hold a lot of moisture, which causes them to swell when water is absorbed and shrink when they are dried. This swelling and shrinkage causes damage to road and building foundations, costing billions of dollars to repair every year. One indicator of how a soil will behave when moisture is added or removed is the plasticity index (PI). A soil sample from Austin, Texas, with a high plasticity index was used to study the effects of lime stabilization on expansive soils. The main goal was to increase the bearing capacity of the soil and reduce volumetric fluctuations of it.
Background
The stabilization of Austin’s expansive soil involved several tests and took approximately four and a half weeks to finish. The following steps were followed to stabilize Austin’s clayey soil: 1. Obtain the soil sample from the field. 2. Determine Atterberg limits in accordance with ASTM D4318 (Figure 4a) and Classify the soil using USCS method. 3. Determine the soluble sulfate content using the modified UTA method (Figure 6b). 4. Select lime percentages, mixing water, and sample soils to be tested. 5. Prepare the sample and compact them after a 24-hour mellowing time. 6. Conduct the Unconfined Compressive Strength test on compacted specimens (Figure 4b). 7. Conduct One-Dimensional Swell Test on control soil and lime-treated soils. 8. Evaluate the results and indicate the most effective percentage of lime to be used on the soil of interest.
7000
(a)
qu =4952 lb/ft2
5000 4000
qu =3433 lb/ft2
3000
1000 0 0
0.5
1
1.5
2
2.5
3
3.5
4
• The Unconfined Compressive Strength increases with the increase of lime percentage (figure 5).
Axial Strain, ԑ (%)
Fig. 5: Strength estimate of treated and non-treated soils
(b)
(b)
Fig. 6: Test Specimens & Sulfate Content Test
Conclusion •We gained an understanding of the concepts behind lime stabilization. •6% lime provided the best results. However, 4% provided nearly similar results and could be more economical. •4% was determined to be the most effective additive for stabilization of Austin’s expansive soil. •For future research, lime could be combined with other additives (such as cement) for improved performance.
Fig. 4: Atterberg Limits and UCS Test
Austin’s soil was classified as a high plasticity clay (Table 1). Table 1. Properties of Austin’s soil
displacement (in)
Time vs. Displacement 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 0.001
0 percent
Soil Property Plasticity Index (PI) Liquid Limit (LL) Plastic Limit (PL) Sulfate Content % Passing #200 Sieve USCS Classification
2 percent 4 percent 6 percent
0.01
0.1
1
10
Time (hr)
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6000
2000
Results and Discussion
RESEARCH POSTER PRESENTATION DESIGN © 2011
Austin's soil with 0% lime Austin's soil with 2% lime Austin's soil with 4% lime Austin's soil with 6% Lime
qu =8061lb/ft2 qu = 7368lb/ft2
8000
(a)
General information •Expansive soils are generally found in arid and semi arid areas. •According to US Department of Housing and Urban Development, the repair of damage on infrastructures caused by expansive soils costs about 9 billion dollars per year (figure 1). •Lime is the most effective and widely used chemical additive for expansive soils (Nelson and Miller, 1992). •The state of Texas has both swelling and shrinking problems because of moisture fluctuations throughout the year (Nelson and Miller, 1992).
Fig. 1: Expansive Soil Damage
Stress vs. Axial Strain
9000
Stress, σ (lb/ft2)
Project Objectives
Fig. 2: Swell Potential of Treated and Non-Treated Soils
Results 30.84% 51.04% 19.76% 261 ppm 95% CH
100
Lime-treated specimens exhibited a very low vertical strain or swelling ability whereas the control specimen swelled considerably (Figure 2). •The more lime used to stabilize an expansive soil is, the lower the swell potential becomes (Figure 2).
References Chen, F. H. (1988). Foundations of Expansive Soils. American Elsevier Science Publ., New York. Das, Braja M. (2002). Soil Mechanics Laboratory Manual, 7th ed., Oxford University Press, New York, N.Y.. Little, D., and Scullion, T. (2005). Guidelines for Modification and Stabilization of Soils and Base for Use in Pavement Structures. Texas Department of Transportation, Texas state. Miller, D. J., Nelson, J. D. (1992). Expansive Soils: Problems and Practice in Foundation and Pavement Engineering, John Wiley & Sons, Inc., Toronto, Canada.
Acknowledgements We are very grateful to all the people who made this research possible, especially Dr. Anand Puppala, Dr. Nur Yazdani, Mr. Aravind Pedarla, Mr. Justin Thomey, Mr. Minh Lee and Mr. Naga Talluritinnu.
