<![CDATA[The construction of the Sigli - Banda Aceh Section of the Trans Sumatra Toll Road faces significant geotechnical challenges due to the dominance of soft alluvial soils along the project area. Soil conditions characterized by low cone penetration resistance (qc) values result in limited bearing capacity and potentially large consolidation settlements on the box underpass structure. This study aims to analyze subsoil characteristics, evaluate bearing capacity and settlement behavior, and determine an effective ground improvement method for the box underpass construction at STA 0+112.95. Field investigations were conducted using Cone Penetration Tests (CPT) at three testing locations to obtain geotechnical parameters, including cone resistance (qc), sleeve friction (fs), and friction ratio (Rf). Bearing capacity analysis was performed using the Meyerhof method, while settlement analysis was carried out based on Terzaghi’s consolidation theory. Numerical modeling was conducted using Plaxis 2D with the Soft Soil Model and Mohr–Coulomb Model to simulate staged construction sequences. The results indicate that the subsoil is dominated by very soft to soft clay layers with qc values ranging from 0.3 to 1.1 MPa sampai kedalaman 3,4m. Granular replacement method was able to improve soil bearing capacity; however, it did not satisfy the allowable settlement criteria. The combination of granular replacement and 25×25 cm concrete mini piles with a length of 6 m proved effective in reducing first-year settlement to 1.4 cm with a consolidation degree of 91%. This study demonstrates that an integrated approach combining field investigation and numerical modeling can provide an optimal geotechnical solution for infrastructure construction on soft soil deposits.]]>
