Abstract:
Construction of infrastructure projects are booming in developing countries in recent
years. For these conditions, geotechnical engineering properties of soils, especially
strength properties, are vital for design purposes. The laboratory equipment's and field
instruments are not available in all areas to get these engineering properties of soil as well
as they require more effort, time, and money. Thus, Geotechnical engineers usually
endeavor to develop statistical models that best fit a specific area and soil type, which is
used especially for analysis and design purposes.
In this study, Statistical Modeling for the Prediction of Undrained Shear Strength from
Index Properties of Cohesive Soils found in Agaro Town is studied. Index properties and
undrained shear strength behavior of these soils were performed in the laboratory of
Jimma Institute of Technology (JiT) and Jimma University college of Agriculture and
Veterinary Medicine(JUCAVM) soil department.
In the present work,undisturbed and disturbed soil samples from fifteen test pits at 1.5 m
and 3.0 m depth are collected. Thirty representative samples were taken from test pits. For
all test procedures, American Society for Testing & Material (ASTM) standard was used.
Combining selected variables, single linear regression (SLR) and multiple linear
regression (MLR) models were developed for the prediction of undrained shear strength
parameter.
To develop the intended statistical models for a study, SAS JMP Pro 13, Statistical Package
for Social Science Software (SPSS v22) and Microsoft Excel-2013 soft wares are used.
The study shows that undrained shear strength parameter (Cu) was significantly correlated
with liquid limit, plastic limit (PL),bulk density, dry density,natural moisture content and
plasticity index (PI) whereas it was not significantly correlated with specific gravity and
liquidity index of study area soil.
From the study, the best Model is obtained from multiple linear regression (MLR) analysis
and given by:Cu=224.032-2.272*PL-2.485*PI; coefficient of determination (R
2
)=0.806,p value=0.00,Tolerance=0.923 and Variance inflation factors (VIF)=1.084,Durbin Watson=2.791.
Using the developed model, undrained shear strength parameter can be figured as well as
it is expected to have wide application in the construction to minimize the cost, effort, and
time for laboratory tests of undrained shear strength of the study area.
