Developing Correlation Between Dynamic Cone Penetration Index And Undrained Shear Strength of Soils that are Found In Debre Markos Town

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Addis Ababa University


Determination of the in-situ engineering properties of foundation materials has always been a challenge for practicing engineers in developing countries. Especially in a country like Ethiopia, where construction of small scale buildings like residential, warehouses, health centres, which are thought to solve the problem of the society in general, is growing in a fast rate. Debre- Markos is one of the fastest developing towns in Ethiopia, which is exposed to rapid civil engineering works like high-rise buildings, and large residential buildings, banks, etc. Since the municipality (sub-city) does not force the designers to conduct soil investigation for buildings less than G+4, designers depend on simple visual inspection and then use the minimum recommended presumptive bearing capacity by EBCS.Even some designers or companies do not conduct soil investigation for building greater than G+4. Some of these predictions may lead to unexpected failures of structure or uneconomical design. 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. In this thesis, field tests were conducted by locally manufactured dynamic cone penetration equipment from available materials. Laboratory tests needed to classify the soil and study the parameters that affect the dynamic cone penetration index and undrained shear strength of soil were also conducted. The data has been categorised in to two categories, correlation between undrained shear strength and dynamic cone penetration index has been developed. In addition correlation between parameters that affect the DCPI and undrained shear strength of soil has also been developed. It has been found out that parameters like unconfined compression strength& liquidity index have influence on the Dynamic Cone Penetration Index (DCPI). These research work revealed that Undrained shear strength can be estimated by UCS= -209.5*ln (DCPI) +800.5 for red clay soils of Debre Markos and UCS= -7.1661*(DCPI) +416.82 for black clay (expansive) soils of Debre Markos in general. These correlations were used to develop bearing capacity equation based on the bearing capacity theory. The equation found were qult= - 538.625ln (DCPI) +12058.086+h for red clay soils of Debre Markos, qult= -18.423*(DCPI) +1071.64+h for black clayey (expansive) soils of Debre Markos. The results are expected to have wide application in the construction sector