Investigation of Geotechnical Properties of Collapsible Soils Within Maiduguri Metropolis

Abstract

This work presents the experimental study to investigate the geotechnical properties of the collapsible soils within Maiduguri Metropolis, Borno state, Nigeria. Ten Soil sampling points (test pits) were considered from five different locations within the town and labelled as A1-A5 (Dikwa, Damboa, Baga, Jos and Bama roads). The samples were obtained with the aid of a hand auger, shovel, 100mm Polyvinyl chloride (PVC) pipes, scrapper and preserved in Polyethene bags and prepared wooden boxes to avoid moisture loss. Particle size distribution revealed that the soils were predominantly sand with traces of gravel and classified as A-3(0) according to the American Association of State Highway and Transportation Officials (AASHTO) and SP in accordance with the Unified Soil Classification System (USCS). The compaction characteristics showed that optimum moisture content (OMC) ranged between 9.0-15.1% and maximum dry densities (MDD) ranging between 1.57-1.92g/cm3 while colours ranged from brown to rich brown. The oedometer test affirmed the existence of collapsible soils in the studied locations while collapse potential (CP) ranged between 1.50-12.20%. The shear strength test revealed low values of cohesion (c) which ranged between 0-1 kPa with an angle of internal friction (ᶲ) ranging between 5-9º. The ultimate bearing capacity result revealed a range between 14.40-86.80 kN/m2 and safe bearing capacity ranging between 20.20-86.80 kN/m2 with a mean safe bearing capacity of 46.26 kN/m2. Hence the soils were classified as cohesionless.