2.2.2. Gwangyang Region

The soil in the Gwangyang region, which was analyzed using nine samples, had the specific gravity, plastic limit, liquid limit, and plastic index of 2.702–2.745 (average 2.718), 14.78–36.37% (avg. 24.13%), 33.77–82.71% (avg. 55.77%), and 18.99–50.50% (avg. 31.63%), respectively, as shown in Figure 4. It had an activity of 0.94–3.79 (avg. 2.60) and was classified into CL and CH as per the unified soil classification system (USCS). The plastic and liquid limits of the Gwangyang region soil were slightly less than those of the Busan region soil. According to the sieve and particle size analysis tests, the sand particle content, silt particle content, and clay particle content were 0.47–10.30%, 67.41–87.14%, and 6.9–22.81%, respectively. The Busan region soil contained slightly finer particles than the Gwangyang region soil as

per the result of the plasticity, sieve, and particle size analysis tests. However, clay minerals might be different due to the higher activity of the Gwangyang region soil than the Busan region soil.

**Figure 4.** Physical properties of Gwangyang region soil: (**a**) Plasticity chart; (**b**) Activity chart.

The clay showed a C<sup>c</sup> of 0.231–0.939 and C<sup>k</sup> of 0.478–0.840 during the IL test, and C<sup>c</sup> of 0.242–1.273 and C<sup>k</sup> of 0.518–1.371 during the CRS test, as shwon in Figure 5. Hence, the Gwangyang region soil showed small ranges of C<sup>c</sup> and Ck. This might be the reason why the Busan clay included more fine clay than the Gwangyang clay.

**Figure 5.** Consolidation properties of Gwangyang region soil: (**a**) liquid limit (LL)-compression index (Cc); (**b**) liquid limit (LL)-permeability change index (Ck).

In the Gwangyang region soil, specimens such as gy-a to gy-e with LL > 60% showed high clay particle content, high plastic index, high compression, and low permeability than the specimens with LL < 60%. Therefore, the Gwangyang region dredged soil can be separated reasonably using the criteria of liquid limit (LL = 60%) in the same way as the Busan region dredged soil. The clay with LL < 60% was named the Gwangyang-L marine clay and the clay with LL ≥ 60% was named the Gwangyang-H marine clay.
