Soil–Water Characteristic Curves for Soils Stabilized with Class C Fly Ash

Abstract

Low-volume roads are often constructed with untreated or lightly treated gravels as the surface or base, and these materials are sensitive to moisture variation. The proper design of low-volume roads requires determining the effects of moisture variation on soil behaviors. A soil–water characteristic curve (SWCC) that characterizes the relationship between the degree of saturation and suction is an important tool for quantifying the mechanical properties of unsaturated soils. The increased use of additives to improve the engineering properties of marginal soils in pavement design has necessitated the need for rapid methods to quantify the SWCC of stabilized soils. This study used the dewpoint method for quick measurement of suction values at various water contents for silt and clay soils stabilized with Class C fly ash. The results indicate that significant suction could exist in soils stabilized with fly ash and that the suction values are greatly affected by the degree of saturation. The suction and degree of saturation in stabilized soils play a significant role in the strength of the stabilized material. The material stabilized with fly ash exhibited hysteresis on the SWCC. The data were also used to compare the suitability and efficiency of five predictive models. It was found that the Fredlund and Xing and van Genuchten models fit the curves for stabilized soils very well as compared with the simplified van Genuchten, Campbell, and Brutsaert models. It is recommended that the Fredlund and Xing and van Genuchten models be included in the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures.

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References

Sirivitmaitrie

, Puppala

A. J.

, Saride

, and Hoyos

. Combined Lime–Cement Stabilization for Longer Life of Low-Volume Roads. In Transportation Research Record: Journal of the Transportation Research Board, No. 2204, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp. 140–147.

Campbell

A. E.

, and Jones

. Soil Stabilization in Low-Volume Roads: Obstacles to Product Implementation from Additive Supplier's Standpoint. In Transportation Research Record: Journal of the Transportation Research Board, No. 2204, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp. 172–178.

Thornton

S. I.

Soil Cement Low Volume Roads in Arkansas. Final Report. Arkansas State Highway Department, Little Rock, 1978.

Bagui

S. K.

Pavement Design for Rural Low Volume Roads Using Cement and Lime Treatment Base. Jordan Journal of Civil Engineering, Vol. 6, No. 3, 2012, pp. 293–303.

Magafu

F. F.

, and Li

Utilization of Local Available Materials to Stabilize Native Soil (Earth Roads) in Tanzania—Case Study Ngara. Engineering, Vol. 2, 2010, pp. 516–519.

AASHTO Guide for Design of Pavement Structures. AASHTO, Washington, D.C., 1993.

ARA, Inc., ERES Consultants Division. Guide for Mechanistic– Empirical Design of New and Rehabilitated Pavement Structures. Final Report, NCHRP Project 1-37A. Transportation Research Board of the National Academies, Washington, D.C., 2004.

Lecerda

, and Marinho

F. A. M.

. Engineering Applications and Case Histories (The State of the Art Reports). Proc., 2nd International Conference on Unsaturated Soils, Vol. 2, Beijing, 1998, pp. 156–159.

Fredlund

D. G.

, Morgenstern

N. R.

, and Widger

R. A.

. Shear Strength of Unsaturated Soils. Canadian Geotechnical Journal, Vol. 15, 1978, pp. 313–321.

10.

Kuttah

D. K.

Improving Low-Volume Road Construction and Performance: Validity of Using the Heavy Vehicle Simulator in Evaluating the Reinforcement of Low-Volume Roads. VTI Notat, No. 9A-2013, 2013.

11.

Mualem

Hydraulic Conductivity of Unsaturated Soils: Prediction and Formulas. In Methods of Soil Analysis, No. 9, Part 1 ( Klute

, ed.), American Society of Agronomy, Madison, Wis., 1986, pp. 799–823.

12.

Porter

L. K.

, Kemper

W. D.

, Jackson

R. D.

, and Stewart

B. A.

. Chloride Diffusion in Soils as Influenced by Moisture Content. Soil Science Society of America Proceedings, Vol. 24, 1960, pp. 460–463.

13.

Kemper

W. D.

, and van Schaik

J. C.

. Diffusion of Salts in Clay–Water Systems. In Soil Science of Society of America Proceedings, Vol. 30, 1966, pp. 534–540.

14.

Lim

P. C.

, Barbour

S. L.

, and Fredlund

D. G.

. The Influence of the Degree of Saturation on the Coefficient of Aqueous Diffusion. Canadian Geo-technical Journal, Vol. 35, 1998, pp. 811–827.

15.

Brown

D. A.

Cation Exchange in Soils through the Moisture Range; Saturation to the Wilting Percentage. Soil Science Society of America, Vol. 17, 1953, pp. 92–96.

16.

Puppala

A. J.

, Punthutaecha

, and Vanapalli

S. K.

. Soil–Water Characteristic Curves of Stabilized Expansive Soils. Journal of Geotechnical and Geoenvironmental Engineering, Vol. 132, No. 6, 2006, pp. 736–751.

17.

Russo

Water Retention Curves of Lime-Stabilised Soil. In Advanced Experimental Unsaturated Soil Mechanics ( Tarantino

, Romero

, and Cui

Y. J.

, eds.), Taylor & Francis Group, London, 2005, pp. 391–396.

18.

Hall

, and Allinson

. Influence of Cementitious Binder Content on Moisture Transport in Stabilized Earth Materials Analysed Using 1-Dimensional Sharp Wet Front Theory. Building and Environment, Vol. 44, No. 4, 2009, pp. 688–693.

19.

Likos

W. J.

, and Lu

Hysteresis of Capillary Stress in Unsaturated Granular Soil. Journal of Engineering Mechanics, Vol. 130, No. 6, 2004, pp. 646–655.

20.

Nam

, Gutierrez

, Diplas

, Petrie

, Wayllace

, Lu

, and Muñoz

J. J.

. Comparison of Testing Techniques and Models for Establishing the SWCC of Riverbank Soils. Engineering Geology, Vol. 110, 2009, pp. 1–10.

21.

Vikas

K. S.

, Thakur

S. S.

, and Singh

D. N.

. Laboratory Investigations on Extremely High Suction Measurements for Fine-Grained Soils. Geo-technical and Geological Engineering, Vol. 24, 2006, pp. 565–578.

22.

Decagon Devices Inc. WP4 Dewpoint Potential Meter Operator's Manual Version 1.3. Pullman, Wash., 2000.

23.

Fredlund

D. G.

, and Xing

. Equations for the Soil–Water Characteristic Curve. Canadian Geotechnical Journal, Vol. 31, No. 4, 1994, pp. 521–532.

24.

van Genuchten

M. T.

A Closed-Form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Science Society of America Journal, Vol. 44, 1980, pp. 892–898.

25.

Campbell

G. S.

A Simple Method for Determining Unsaturated Conductivity from Moisture Retention Data. Soil Science, Vol. 117, No. 6, 1974, pp. 311–314.

26.

Brutsaert

Probability Laws for Pore Size Distributions. Soil Science, Vol. 101, 1966, pp. 85–92.

27.

Sillers

W. S.

, and Fredlund

D. G.

. Statistical Assessment of Soil–Water Characteristic Curve Models for Geotechnical Engineering. Canadian Geotechnical Journal, Vol. 38, 2001, pp. 1297–1313.