Table 6.

Constrained modulus factor ${\alpha }_M$, as defined by Robertson.

Conditions		Relationship for ${\mathit{\alpha }}_{\mathit{M}}$	Notes
$I_c>2.2$	$Q_{tn}<14$	${\alpha }_M=Q_{tn}$	fine-grained soil (soft clay)
$I_c>2.2$	$Q_{tn}>14$	$Q_{tn}=14$	stiff fine-grained soil
$I_c<2.2$		${\alpha }_M=0.03·{10}^{\left(0.55I_c+1.68\right)}$	coarse-grained soils