<![CDATA[The coastal areas along the northern coast of Java, particularly the Semarang–Demak region, are characterized by thick soft clay deposits with high compressibility and low shear strength. Compounding these challenges, progressive land subsidence increases flood risk, necessitating the construction of retention ponds as hydraulic control infrastructure. This study presents a numerical investigation of the performance of Prefabricated Vertical Drains (PVD) combined with preloading and geotextile reinforcement to stabilize retention pond embankments constructed over coastal soft soil. Finite element analyses were performed using PLAXIS 2D under plane strain conditions. Two scenarios were evaluated: (1) a baseline condition without reinforcement and (2) a fully improved condition incorporating PVD, a sand drainage layer, and geotextile reinforcement. Results indicate that the unreinforced embankment failed to achieve stability under the combined hydrostatic, traffic, and seismic loading. The integrated improvement system effectively dissipated excess pore water pressure, reduced total deformation to 34 cm, and achieved a safety factor of 1.55, satisfying the minimum requirement of 1.5 stipulated by SNI 8460:2017. These findings provide practical guidance for the geotechnical design of retention pond infrastructure in subsidence-affected coastal areas.]]>
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