Equivalent Stress Equation for Unsaturated Soils. I: Equivalent Stress

In 1959 Bishop stated his effective stress equation for unsaturated soils. However, the difficulties in estimating the value of its main parameter χ , made this equation useless and it was abandoned for some time. Only recently, it has been recognized that the use of Bishop’s stress equation can lead to simpler and more realistic constitutive models for unsaturated soils. However, up to now the most successful equations to quantify the value of parameter χ are empirical and not satisfactory for most soils. Based on the analysis of the equilibrium of the solid particles of a soil showing a bimodal structure and subject to certain suction, it was possible to establish an analytical expression for Bishop’s parameter χ . The resulting stress has been called equivalent stress (in contrast with effective stress) and can be used to predict the shear strength of unsaturated soils. The equivalent stress is written as a function of the net stress and suction and requires two parameters: the saturated fraction and t...

[1]  Delwyn G. Fredlund,et al.  Shear strength characteristics of two saprolitic soils , 1996 .

[2]  E. L. Matyas,et al.  Volume Change Characteristics of Partially Saturated Soils , 1968 .

[3]  D. Fredlund,et al.  Influence of stress history on the strength parameters of an unsaturated statically compacted soil , 1999 .

[4]  E. Murray.  An equation of state for unsaturated soils , 2002 .

[5]  A. Bishop,et al.  Experimental study of partly saturated soil in the triaxial apparatus , 1961 .

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

[7]  R. Tamagnini,et al.  An extended Cam-clay model for unsaturated soils with hydraulic hysteresis , 2004 .

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

[9]  Poul V. Lade,et al.  THE CONCEPT OF EFFECTIVE STRESS FOR SOIL, CONCRETE AND ROCK , 1997 .

[10]  John Burland,et al.  Limitations to the Use of Effective Stresses in Partly Saturated Soils , 1962 .

[11]  D. E. Pufahl,et al.  Model for the prediction of shear strength with respect to soil suction , 1996 .

[12]  Simon J. Wheeler,et al.  Coupling of hydraulic hysteresis and stress–strain behaviour in unsaturated soils , 2003 .

[13]  A. Bishop,et al.  Some Aspects of Effective Stress in Saturated and Partly Saturated Soils , 1963 .

[14]  M. M. Allam,et al.  EFFECT OF WETTING AND DRYING ON SHEAR STRENGTH , 1981 .

[15]  Chandra S. Desai,et al.  Disturbed State Model for Porous Saturated Materials , 2003 .

[16]  Sai K. Vanapalli,et al.  Evaluation of Empirical Procedures for Predicting the Shear Strength of Unsaturated Soils , 2006 .

[17]  A. Gens,et al.  An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour , 2003 .

[18]  A. W. Bishop,et al.  The Principle of Effective Stress , 1959 .

[19]  William B. Haines,et al.  Studies in the physical properties of soils: II. A note on the cohesion developed by capillary forces in an ideal soil , 1925, The Journal of Agricultural Science.

[20]  N. Khalili,et al.  A unique relationship for χ for the determination of the shear strength of unsaturated soils , 1998 .

[21]  A L Oberg,et al.  A RATIONAL APPROACH TO THE DETERMINATION OF THE SHEAR STRENGTH PARAMETERS OF UNSATURATED SOILS , 1995 .

[22]  M. Biot.  THEORY OF ELASTICITY AND CONSOLIDATION FOR A POROUS ANISOTROPIC SOLID , 1955 .

[23]  Harianto Rahardjo,et al.  DETERMINATION OF THE SHEAR STRENGTH PARAMETERS OF AN UNSATURATED SOIL USING THE DIRECT SHEAR TEST , 1988 .

[24]  Simon J. Wheeler,et al.  Influence of compaction procedure on the mechanical behaviour of an unsaturated compacted clay, Part 1: Wetting and Isotropic Compression , 2000 .

[25]  A. Gens,et al.  A constitutive model for unsaturated soils: thermomechanical and computational aspects , 2004 .