Geotechnical Investigation of Aggregate Base Course being used in the Construction of Koral Chowk Interchange, Islamabad, Pakistan (P-0973) (MFN 5850)

Abstract

The purpose of the research study is to investigate the geotechnical characteristics of the Aggregate Base Course material being used for the construction of Koral Interchange with the help of different field and lab tests. The tests include Gradation (Sieve analysis), Liquid Limit, CBR (California Bearing Ratio), Sand Equivalent, Specific Gravity and Absorption, Proctor Test and LA (Los Angles). The Liquid Limit was conducted to know the maximum value of moisture content that can be achieved in field. Liquid Limit according to Atterberg Limit was 18.32 and the material was non plastic in nature which according to AASHTO soil classification corresponds to granular material of group A-3. The proctor test was conducted to determine the (MDD) Maximum Dry Density and (OMC) Optimum Moisture Content. The MDD was 2.32 and OMC was 5.6. According to Los angles test result (20.6%), the clayey content is low. The low clayey content reduces the swelling effect. The dry density from Field Density Test and Optimum Moisture Content from proctor was used to determine the degree of compaction. The degree of compaction was 100% for Aggregate Base Course which correspond AASHTO Classification. The Sand Equivalent test result for sand was 75% and the Los Angeles Abrasion was 20.6% which is also according to the specifications of the project. The source of the material is Margallah Hills limestone that is widely used in construction projects. According to AASHTO international standards, the material belongs to Grade A, which is considered best suitable for the Aggregate Base Course.