The town of Pabna covers the northern floodplain of the river Padma, characterized by abundance of low-lying depressions and remarkably variable subsurface lithology, which in turn influences the geotechnical condition. The northern and eastern parts are characterized by low SPT strength, which is not suitable for heavy construction. Based on the study of geological and geomorphological maps, engineering properties of soil, such as lithology, atterberg limit, consistency, bearing capacity, plasticity, compaction, consolidation and compressibility, SPT etc., a geotechnical map is prepared.
The study area is divided into four major unit areas. Unit I is not suitable at all whereas, unit II is less suitable for heavy construction. But normal foundation up to the depth of 10 to 18 m below the surface is needed for the construction of high-rise buildings. Sediments of unit II are weakly compacted and have medium plasticity and compressibility.
Plasticity of sandy silt and silty clay is low to medium with high activity. Unit III is the most suitable for heavy construction with normal foundation depth up to 3 to 10 m below the surface. It constitutes mainly sand with low plasticity and low to very low compressibility. The SPT values vary from 10 to 40. The geotechnical assessment of the subsurface sediments of the area is essential before constructing civil engineering structures. |
