Correlation of Dynamic cone penetration with undraind shear strength of clay soils: A case study of Jimma town.

Abstract

Determination of the in-situ engineering properties of foundation materials has always been a challenge for practicing engineers in developing countries due to limited resources available for investing on sophisticated field equipment which usually leads to usage of unreliable design data. To avoid such problems, this research introduces the use of Dynamic Cone Penetration (DCP) which is a simple test device that is inexpensive, portable, and easy to operate and understand. The objective of the study to correlate Dynamic Cone Penetration (DCP) with undrained shear strength (Su) and bearing capacity of typical Jimma clay soil. In this thesis, field tests were conducted by dynamic cone penetration equipment. Laboratory tests needed to classify the soil and study the parameters that affect the dynamic cone penetration were conducted and the test results are analyzed by spss statistical software and Microsoft excel to find their correlation functions. After analyzing the data, it has been found that parameters like unconfined compression strength, dry density, and bulk density have influence on the DCP. From field investigations and laboratory test results correlation has been developed between Unconfined Compression Strength (qu) and DCP as qu=0.3224DCP2 -20.975DCP+457.0 with coefficient of determination (R2 ) of 63%, for typical clay soils in Jimma town. From this undraind shear strength is C = 0.1612DCP2 -10.4875DCP+228.52. These correlations were further used to develop bearing capacity equation based on bearing capacity theory as qult = 0.829DCP2 -53.927DCP+ γh +1175.049. These correlations can be used as a starting point in characterizing geotechnical properties of typical soils in Jimma town for the development of infrastructure and related applications.