Geotechnical Assessment of the Dhaka–Sylhet Corridor (DS-05): Soil Classification, Bearing Capacity, and Foundation Implications

This study presents the results of a geotechnical investigation carried out for the SASEC Dhaka–Sylhet Corridor Road Investment Project (Contract Package DS-05) under the Roads and Highways Department (RHD) of Bangladesh. The investigation was conducted with the objective of determining subsurface soil conditions and providing reliable geotechnical data for the design and construction of major road infrastructure. Field investigations were performed from 9th to 13th September 2023, employing percussion drilling and Standard Penetration Tests (SPT) in accordance with ASTM D1586 and ASTM D1587[2,3,4]. Both disturbed and undisturbed soil samples were collected and tested in the laboratory to determine their physical and engineering properties, following ASTM D2488 classification methods. The site classification was performed as per the Bangladesh National Building Code [8]. Results of the investigation revealed that soil strata within the project area are composed mainly of silty clay and fine to medium sand layers with variable consistency. The measured SPT-N values suggest moderate bearing capacity suitable for shallow and pile foundation types, depending on localized conditions. These findings are essential for the safe and economical design of embankments, bridge abutments, and pavement structures along the Dhaka–Sylhet corridor. The outcomes also provide a valuable reference for future infrastructure development projects in similar geotechnical settings across Bangladesh [10,14].