2.2.1. Busan Region

The characteristics of dredged soil in the Busan region were analyzed using 10 samples, and are shown as plasticity and activity charts in Figure 2a,b, respectively. The specific gravity, plastic limit, liquid limit, plastic index, and activity of the samples were 2.706–2.731 (average 2.718), 20.88–39.31 (avg. 28.97%), 40.10–94.26% (avg. 60.74%), 15.56–54.96% (avg. 31.77%), and 0.8–2.29 (avg. 1.63), respectively. The specimens bs-g, bs-i, bs-j, and bs-k followed the A-line on the plasticity chart, and other specimens showed liquid limits (LL) in the range of 40–55% (LL < 60%). The specimens in the Busan region can be separated into bs-a to bs-f (LL < 60%) and bs-g to bs-k (LL ≥ 60%), according to the liquid limit. It can be observed from Figure 2b that specimens with LL less than 60% represent a contented clay mineral with a PI (plasticity index) range of 10–20%, and the specimens with LL greater than 60% represent activated clay with a PI range of 33–55%. According to the sieve and particle size analysis tests, the sand particle content (less than the No. 200 sieve, 0.074 mm), silt particle content, and clay particle content were 0.62–5.07%, 72.90–82.93%, and 16.05–24.53%.

**Figure 2.** Physical properties of Busan region soil: (**a**) Plasticity chart; (**b**) Activity chart.

The specimens showed the compression index (Cc) of 0.316–0.883 and permeability change index (Ck) of 0.209–1.328 during the oedometer [incremental loading (IL)] test, and C<sup>c</sup> of 0.530–1.011 and C<sup>k</sup> of 0.731–1.799 during the CRS consolidation test where the compression index (Cc) and the permeability change index are defined as <sup>∆</sup><sup>e</sup> log *p*/*p*<sup>0</sup> and <sup>∆</sup><sup>e</sup> log *k*/*k*<sup>0</sup> . The consolidation properties of the Busan region soils as per the liquid limit are shown in Figure 3. Specimens (bs-a, b, d) with LL < 60% showed small compression and high permeability than the specimens with LL ≥ 60%. Therefore, the separation of the Busan region soil using the criteria of liquid limit (LL = 60%) can be considered reasonable because the physical and consolidation properties are different. The clay with LL < 60% was named the Busan-L marine clay and the clay with LL ≥ 60% was named the Busan-H marine clay.

**Figure 3.** Consolidation properties of Busan region soil: (**a**) liquid limit (LL)-compression index (Cc); (**b**) liquid limit (LL)-permeability change index (Ck).
