On the basis of the problem stated previously, the newly developed
parameter must assess the engineering properties of cement-clay
admixtures in saturated and unsaturated conditions. Therefore,
the influencing factors for both conditions are first reviewed to
understand the similarities and differences. Previous studies of deep
mixing clay-cement mixture indicate that its engineering behavior
is primarily affected by the physicochemical properties of clay, the
amount of cement, the water content, and the curing time (Uddin
et al. 1997; Miura et al. 2001; Lorenzo and Bergado 2004;
Horpibulsuk et al. 2005; Chew et al. 2004; Lee et al. 2005).
The factors controlling air-cement-treated clay behavior are the
amount of cement, the curing time, and the void ratio (Hayashi
and Suzuki 1999; Tsuchida et al. 2001; Hayashi et al. 2002; Watabe
et al. 2004). The physicochemical properties of clay depend on the
clay mineralogy and composition. It is difficult to include clay type
in the construction of a parameter. This study therefore aims to develop
the parameter from cement content, water content, curing
time, and void ratio. This new parameter must capture and combine
mechanical properties, such as strength and yield stress of both saturated
and unsaturated cement-clay mixtures having the same clay
type. Because a number of studies with comprehensive test data on
deep mixing wet cement-treated clay are available (Lorenzo and
Bergado 2004; Jongpradist et al. 2007, 2010, 2011), this study performs
only complementary tests on unsaturated cement-clay admixtures
for the purpose of clarification. By principle, the void
ratio at the initial state before testing is one of the basic parameters
that influence the mechanical properties of soil. The use of the voidto-cement
ratio is proven to be appropriate to assess the unconfined
compressive strength of sandy soils stabilized by cement or lime
(Consoli et al. 2007, 2009). Therefore, the after-curing void-tocement
ratio eot=Aw proposed by Lorenzo and Bergado (2004),
which combines the effects of curing time, clay-water content,
and cement content on the unconfined compressive strength of
cement-treated clay, is adopted for further development. The eot
can be directly calculated from the equation