Suitability of cohesionless soil as a highway construction material

Abstract

Major parts of the Eastern and Northern provinces of Sri Lankti are covered with cohesionless soil. Utilization of locally available soil for the construction of the subbase of these roads will optimize the cost and reduce the environmental impact. Recently cracks, settlement and outward movement have been observed in the pavement constructed using the locally available sandy soil. It is suspected that the usage of locally available soil would have caused this failure. Objective of this study is to assess the quality of the cohesionless soil as a highway construction material. Further, the applicability and validity of the currently used specifications for use of cohesionless soil as a highway construction material are also evaluated. To accomplish the above tasks, the experience of the construction industry in this regard WOJ gathered through site visits, case studies, interviews with relevant personals. Based on the collected information a comprehensive laboratory test program was formulated to investigate the interrelationships between the soil properties such as grading, maximum dry density, California Bearing Ratio(CBR) value, plasticity index(PI), and liquid limit by mixing different type of clays with pure coarse sand. Laboratory test results and field data collected from road construction projects were analyzed. Final results were reviewed by the senior consultants at Road Development Authority(RDA) and National Building and Research OrganizationfNBRO).