Evaluation of Mechanical Behavior in Ralation to Index Properties of Different Soils in Pakistan

Abstract

The variations in mechanical behavior of a soil over time play a key role in the design of all civil infrastructure projects, including highways, runways, canal linings, landslides, earthen dams, retaining walls and foundations, and for a particular structure, it is pre-requisite to precisely simulate mechanical behavior of used soils with respect to project specific conditions. It is well known that a particular soil behaves in a different fashion than others, under similar loading conditions due to differences in their index properties, such as specific gravity, particle size distribution, consistency limits and dry unit weight. Though research studies are available in literature in this regard, reporting the mechanical behavior in relation to index properties of different soils, but the scope of these studies is quite limited as they are mainly focused on few soil types or only consider few parameters of practical interest, and furthermore, no research of this type has been conducted in the context of Pakistan so far, specifically. The objective of this study is to investigate the mechanical behavior in relation to index properties for several different soils, got from various zones of Pakistan, and regarding this, several triaxial, California Bearing Ratio (CBR), Oedometer and index properties tests were performed to estimate the compressibility parameters, strength parameters and other geotechnical properties to develop some useful empirical relationships for these soils. The test data shows that the shear strength, compressibility and CBR change with %age changes in clay contents. The highly plastic soil (Nandipur soil) provides maximum dry density at lower peak, and at higher water contents than other soils. The sandy soils, such as ML, SC and SP need less water to reach at maximum dry density. The maximum dry density decreases and optimum moisture content increases with an increase in plasticity index, providing strong relationships. The compression and swelling indices show strong relationships with Atterberg limits, %age clay contents, and optimum moisture contents. The triaxial tests show that cohesion and angle of internal friction provide strong inverse relationship with %age clay contents, and furthermore, CBR shows strong inverse relationship with specific gravity, Atterberg limit, optimum moisture content, and cohesion and strong direct relationships with maximum dry density and angle of internal friction.