Fig. 9 demonstrates that the ratio, eot /Aw, has fairly combined together the effects of total clay water content, cement content and curing time on the unconfined compression strength of cement-admixed clay. The values of eot of each sample shown in Figs. 5(a–c) were calculated using Eq. (2) with measured values of vt, Gst, and gt. Also plotted in Fig. 9 are data from field coring samples obtained in the core of full-scale deep mixing method
(DMM) soil-cement piles installed in Ladkrabang-Bang Phli in the east of Bangkok metropolis, Thailand (Fig. 1) for the construction of Highway No. 3256 (AIT 1998). Although the sites of the field coring samples are different from that of the base clay utilized in laboratory tests, the clay deposit at these sites is basically the same, i.e., the soft Bangkok clay. Though the parameter eot is deemed to reflect not only the total clay water content sCwd and curing time but also the cement content sAwd, the inclusion of Aw in the ratio eot /Aw is due to the following events. First, the specimens with different cement contents can have the same void ratios after curing depending on the total clay water content present during mixing, but may possess different levels of strength. Second, even though the samples have the same cement contents but different total clay water contents, they may still possess different levels of strength. The effectiveness of the eot /Aw ratio is further proven in Fig. 9 where the unconfined compression strengths of both field and laboratory samples reasonably follow a unique relationship with the eot /Aw ratio. Therefore even though the experimental and field data are limited and based only on a single clay deposit (soft Bangkok clay), the following relationship has been derived to describe the unconfined compression strength of any cement-admixed clay: qu = ApaeBseot/Awd s3d where A and B5dimensionless constants; and pa5atmospheric
pressure. Based on the results presented, for soft Bangkok clay mixed with Type I Portland cement, the constants are A=10.33 and B=−0.046. Since the void ratio of soil cannot be zero, the only possibility that the eot /Aw ratio will be zero is only when Aw is infinity, which can only happen if the clay-cement paste is comprised of cement grout only. Hence the constant A is affected by the type of admixture (or type of cement), while the constant
B, which is basically the slope of the mean function in Fig. 9, will
be affected by the type and mineralogy of the base clay. Therefore
constant A is dependent on the type of admixture, while constant
B is dependent on the type of base clay.