Assessing the physical and geotechnical properties of subsoils within an active municipal solid waste dumpsite for secured future urban growth

Abstract

This study attempts to investigate the geotechnical properties of subsoils in an active Dumpsite (DS) within the basement complex area of Abeokuta, Nigeria with a view to assess its suitability as a foundation/filling material. Sixteen (16) composite soil samples were collected from four different parts of the DS at varied depths of 0.0 - 0.5, 0.5 - 1.0, 1.0 - 1.5, and 1.5 - 2.0 m. The soil properties considered are particle size distribution, Specific Gravity (SG), permeability, Shear Strength (SS), Maximum Dry Density (MDD), Optimum Moisture Content (OMC), Natural Moisture Content (NMC) and Atterberg limit (AL) indices. Results show that the assessed soil samples are sandy soils with less than 30% clay content. The ALs test revealed that analysed samples had low Plasticity index (PI) (0.20 - 11.96%), low values of Plastic Limit (PL) and Liquid Limit (LL) of (14.19 - 18.83% and 17.52 - 26.15%, respectively). The MDD values ranged from 1.07 to 1.76 g/cm3 while the NMC and OMC were <25% and <18%, respectively. The permeability coefficients ranged from 1.53 x 10⁻⁴ to 8.49 x 10⁻³ cm/s, indicating moderately permeable soil while the SS results (ranging from 3.4 to 12.5 KPa) indicate low cohesive capacity soils. The tested soils are mildly suitable for foundation/filling materials. Further study is needed to study the trend of alteration of soil properties with depth on dumpsite soil located on other geological formations.