Effects of compaction moisture content on the shear strength of an unsaturated clay

This paper deals with the results of an experimental study carried out on compacted clay (PL=23%) to investigate the influence of compaction water content on the shear strength of the clay. For the measurement of shear strength parameters, direct shear tests were done on samples compacted at optimum moisture content (i.e. w=24%), at the dry side of optimum (i.e. w=18%, 20% and 22%) and at the wet side of optimum (i.e. w=26% and 28%). Thermocouple psychrometers were used for suction measurements and the suction-moisture content relationship of the soil sample was obtained. The trends for suction, angle of friction and cohesion, which change below and above optimum moisture content, were analyzed. The compacted clay behaves like a granular soil on the dry side of optimum water content; and a reduction in angle of friction and an increase in cohesion are observed as the compaction water contents approach the optimum value. The angle of friction is not affected by soaking, but after soaking cohesion of the sample reduces.

[1]  E. Selig,et al.  Laboratory Evaluation of Soil Suction Components , 1984 .

[2]  I. Rosenqvist.  Closure of "Physico-Chemical Properties of Soils: Soil-Water Systems" , 1960 .

[3]  Donald R. Snethen,et al.  Characterization of Expansive Soils Using Soil Suction Data , 1980 .

[4]  H. B. Seed,et al.  The Strength of Compacted Cohesive Soils , 1960 .

[5]  S. Ahmed,et al.  PORE SIZES AND STRENGTH OF COMPACTED CLAY , 1974 .

[6]  Y. Cui,et al.  Microstructure of a compacted silt , 1996 .

[7]  V. Escario,et al.  The shear strength of partly saturated soils , 1986 .

[8]  Sidney Diamond,et al.  Pore Size Distributions in Clays , 1970 .

[9]  James K. Mitchell,et al.  Fundamentals of soil behavior , 1976 .

[10]  I J A Brackley,et al.  Swell pressure and free swell in a compacted clay , 1973 .

[11]  D. Fredlund,et al.  Soil Mechanics for Unsaturated Soils , 1993 .

[12]  D. Toll.  The Influence of Fabric on the Shear Behaviour of Unsaturated Compacted Soils , 2000 .

[13]  S. Leroueil,et al.  Combined effect of fabric, bonding and partial saturation on yielding of soils , 2000 .

[14]  L.-W. Kong,et al.  Study on shear strength and swelling-shrinkage characteristic of compacted expansive soil , 2000 .

[15]  Serge Leroueil,et al.  YIELDING AND CRITICAL STATE OF A COLLAPSIBLE UNSATURATED SILTY SOIL , 1995 .

[16]  P. R. Vaughan,et al.  The general and congruent effects of structure in natural soils and weak rocks , 1990 .

[17]  Simon J. Wheeler,et al.  An elasto-plastic critical state framework for unsaturated soil , 1995 .

[18]  Antonio Gens,et al.  A constitutive model for partially saturated soils , 1990 .

[19]  D Croney,et al.  MOVEMENT AND DISTRIBUTION OF WATER IN SOIL IN RELATION TO HIGHWAY DESIGN AND PERFORMANCE , 1958 .