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Lime Stabilization of Expansive Soils

• 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.

Project Objectives

Joseph Desire Muhirwa Richard Benda Robert Sargent Aravind Pedarla Dr Anand Puppala

California Baptist University New Mexico Tech California Baptist University University Of Texas at Arlington University of Texas at Arlington

Civil Engineering Civil Engineering Civil Engineering PhD Student Faculty, Geotechnical Engineering

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.

Introduction

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.

Methods and Procedure

• The

Unconfined

Compressive

Strength

increases

with the

increase of

lime

percentage

(figure 5).

Results and Discussion

Conclusion

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.

References

•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.

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.

Background

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).

TxDOT Flow chart for Subgrade Soil Stabilization

Austin’s soil was classified as a high plasticity

clay (Table 1).

Table 1. Properties of Austin’s soil

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).

Soil Property Results

Plasticity Index (PI) 30.84%

Liquid Limit (LL) 51.04%

Plastic Limit (PL) 19.76%

Sulfate Content 261 ppm

% Passing #200 Sieve 95%

USCS Classification CH0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

0.065

0.07

0.075

0.08

0.001 0.01 0.1 1 10 100

dis

pla

cem

en

t (i

n)

Time (hr)

Time vs. Displacement

0 percent

2 percent

4 percent

6 percent

Fig. 1: Expansive Soil Damage

Fig. 5: Strength estimate of treated and non-treated soils

Fig. 4: Atterberg Limits and UCS Test

Fig. 6: Test Specimens & Sulfate Content Test

Fig. 2: Swell Potential of Treated and Non-Treated Soils

(b) (a)

(a) (b)

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% 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

qu =4952 lb/ft2

qu =3433 lb/ft2