Compression Index for cohesive soils from Quasi-static Cone Tests

Abstract

Compression indexiisiani important soili parameter in the design of foundations of structures yeti the Oedometer test used for its determination is time consuming, cumbersome and very costly. This prompted a number of studies to be done toi address the above limitations by relating Atterberg limits to compression index. However, determination of Atterberg limits has limitations which include stress-strain effects during penetration for the fall cone human reliability errors for the Casagrande method of liquid limits determination and Health & safety issues in handling contaminated soili material for Plastic limits. The aim of this research was toi develop ai simple, fast and accurate method of determining the compression index of cohesive soils using the Quasi-static cone test which addresses all the above limitations. 51i soili samples were collected from three districts of Uganda (Area = 1230km2) and tested for the compression index using Oedometer test, liquid limit using fall cone and Plastic limit using thread rolling. The Atterbergi limits were correlated toi compression index using regression analysis. The same soili samples were tested using the quasiistatic method and forces close toi 1020gfi and 60gfi were obtained for plastic and liquid limit respectively at 20mmi penetration depth. The empirical relationships relating the force from the quasiistatic method and compression index was found toi be 98%i accurate compared toi the compression index from Oedometer test.