Browsing by Author "Sissay, Dessalegn"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Computation of Soil Compressibility Using Tangent Modulus Approach
    (Addis Ababa University, 2003-07) Sissay, Dessalegn; Tadesse, Samuel(PhD)
    Keywords: tangent modulus, resistance, modulus number and strain There are several mechanisms causing settlement of a structure. Different structures have varying potential to withstand the settlement that takes place Thus, its determination has to be given due consideration by engineers as it affects these structures from functioning properly if not limited to a permissible value. Soils consist of solid particles and void space. Gas or water or combination of both occupies the void space. When loaded the water and air gets squeezed out resulting in settlement. Determination of settlement and the rate at which the expulsion takes place is determined from the theory of consolidation. The classical approach, which is widely used in our country and other parts of the world, has limitations. These limitations have contributed for the development of the tangent modulus approach. The tangent modulus approach provides better way of determining settlement for various types of soil ranging from hard to very soft soil. In the method the soil property, which is determined from laboratory soil deformation tests, are used. In the approach a compression modulus also called the constrained modulus, the tangent to a linear plot of stress versus strain curves determined from laboratory tests play a significant role. It is emphasized on this property of the soil, as it is a measure of resistance of the soil against deformation due to change in loading condition The compression modulus, measures of the resistance of a media or an isolated part of it against a forced change of equilibrium condition. It is based on the resistance concept, which is very well developed in other field of engineering, except that its application for settlement analysis in soil mechanics is new. 1 1. Introduction 1.1 General Construction scheme is advancing day to day. This has made possible construction of high rising buildings, heavy structures and highways. Due to this heavy loads are induced on to the soil underneath. Besides the use of undesirable construction site is increasing. The above factors results in compressive strains causing settlement of a structure. The resulting settlement has to be limited to a minimum to allow the structure function properly and maintain the required aesthetic value. Further cost of maintenance has to be limited to a minimum. For estimating the settlement that occurs in cohesive sols the classical approach is widely used in most parts of the world including Ethiopia. This approach assumes the compressibility of the soil remains constant. Further it was believed that the initial pore water pressure describes the consolidation characteristics of thick clay. These and other assumptions limit the validity of the approach. Thus, another method of settlement evaluation which amends at least the above mentioned drawbacks have to be adopted. This paper introduces another method as compared to classical method for the determination of settlement, which is known as the tangent modulus approach. 1.2 Background The probable settlement any structure undergoes on different types of soils is predicted by compressibility study. Thus, based on the compressibility characteristics the method which relies on the stress- strain analysis of soil for determining this property is dealt with. 1.3 Objective of the Present Work The objective of the research work is to: i) Introduce a recent and more practical way of determining settlement and compare the applicability with the existing and more popular classical approach. ii) To