Abstract

This paper presents some issues of geotechnical investigation for roads built on expansive soils. The aim of the study is to provide road ‎engineers with guidance on site investigation; field and laboratory identification of expansive soils. A clear understanding of the ‎expansive subgrade soils behavior and their geotechnical characteristics has been of more interest to the study in order to assess properly ‎the source of the swelling problem. Two case study sites, representative known problem-areas in Khartoum were carefully selected for ‎geotechnical site investigation. The field exploration consisted of excavating trial pits and collecting soil samples from the subgrade. These ‎soils were subjected to laboratory testing for measuring the particle size analysis, consistency, strength and swelling characteristics. The ‎soils were found to have over 50% clay particles, high plasticity index more than 30% and high free swell index of 160% to 250%. The ‎compacted samples were found to have swell potential of 7% to 15% coupled with high swelling pressure in excess of 90 kPa and low ‎strength, CBR values less than 4%. General conclusions have been drawn from the study findings.‎

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