Ce. Fear et Pk. Robertson, ESTIMATING THE UNDRAINED STRENGTH OF SAND - A THEORETICAL FRAMEWORK, Canadian geotechnical journal, 32(5), 1995, pp. 859-870
A framework for estimating the ultimate undrained steady state shear s
trength of sand (S-u) from in situ tests, which combines the theory of
critical state soil mechanics with shear wave velocity measurements,
is presented. For a particular direction of undrained loading, samples
of a given sand at a constant void ratio will reach the same S-u, des
pite the magnitude of the initial effective confining stresses. Unique
S-u/p' or S-u/sigma'(v) ratios for a given direction of loading exist
for a particular sand only if state parameter is constant throughout
the deposit. Normalized shear wave velocity, V-s1, can be correlated w
ith void ratio and is therefore used to estimate S-u for a given initi
al state and direction of loading. Strengths in triaxial compression a
re examined in this paper; however, the same framework can be used to
estimate strengths under other directions of loading. The S-u-V-s1 rel
ationship is shown to be relatively sensitive and should be used more
as a screening tool rather than an accurate means of predicting S-u. V
-s1 is converted to equivalent values of SPT (N-1)(60) and CPT q(c1),
and the results are compared with the current methods of estimating S-
u.