Correlation between Undrained Shear Strength Parameters and Index properties of Clay Soils in Botor Toley, Wayu Town.

Abstract

Geotechnical investigations are made to determine geologic, seismologic, and soils conditions that affect the safety, cost effectiveness, design, and execution of a proposed engineering project. The laboratory testing of soil strength is not easily found to get the design parameters, Determining of undrained shear strength (cu) parameters of soil is difficult, time consuming and costly compared to index properties of soils. Therefore, it is necessary for the soil engineer to furnish himself with the necessary soil parameters which he must employ in some empirical or analytical formulae in order to get the desired solution. The objective of this thesis is to correlate undrained shear strength parameters and index properties of clay soils in Botor Toley, Wayu Town. The methodology used for this thesis was include visual identification, sampling, laboratory tests, and analysis of results. In this study, thirty representative undisturbed and disturbed soil samples were collected from fifteen test pits at 1.5m and 3m depth. For all test procedures, American Society for Testing & Material (ASTM) standard was used. The laboratory test results of natural moisture content(NMC) ranges between 27.1%-32.2%, specific gravity(Gs) between 2.61-2.81, liquid limits(LL) ranges between 66.07-84.02%, plastic limits(PL) ranges between 27.95-36.76%, plasticity index(PI) ranges between 36.5-48.2%, bulk and dry density ranges between 1.77 1.89g/cm3 and 1.36-1.47g/cm3 respectively and the amount of undrained shear(CU) strength ranges between 55.24Kpa to 96.97Kpa. Microsoft excel, Origin pro and Statistical package for the social science (SPSS) software were used for the scatter plot, correlation, and regression analysis. To know linear relationships between each parameter statistical relationships of all the parameters (undrained shear strength, natural moisture content, liquid limit, plastic limit, plasticity index, specific gravity, bulk density and dry density) were analyzed. Using the results obtained from laboratory tests, it shows that undrained shear strength were significantly correlated with natural moisture content, liquid limit, plastic limit, Plasticity index and dry density, and not significantly correlated with bulk density and specific gravity. From the study, based on linear regression analysis, the best model was obtained and the equation is CU = 2.753*NMC + 1.488PL + 1.95PI – 135.27 with 0.872 of coefficient of determination (R2 ). Using the developed model, undrained shear strength parameter(cu) can be figured and expected to have wide applicable in different civil Engineering sectors, and construction to minimize the cost, effort, and time for laboratory tests of undrained shear strength of the study area.