Oedometer Laboratory Testing Report
Division of Civil Engineering
University of Dundee
School of Engineering, Physics and Mathematics
University of Dundee
Table of Contents
5.1Voids ratio, consolidation parameters and pre-consolidation pressure6
5.2Constrained modulus, coefficient of consolidation and permeability7
Long term settlement in clayey soils has posed a challenge to engineers for literally thousands of years. Predicting this settlement is not an easy task, but by analysing the soil on the proposed build site, engineers can get a better understanding of how the soil will react under compression, what needs to be done to make the soil suitable and whether it is worth building on the site at all. Knowing how soil on a potential building site will react under compression is essential for obvious reasons. Apart from possibly damaging the structural integrity of a building in extreme cases, settlement can also cause unsightly cracks and other faults that affect the serviceability of the construct. Consolidation is the gradual reduction in volume of a fully saturated soil of low permeability. Consolidation occurs due to the generation of an excess pore water pressure. Totally consolidation is achieved when the excess pore pressure in the soil is completely dissipated.  (Craig’s soil Mechanics, 7th edition). In simpler terms, consolidation is the compression of a soil due to an increase in the effective stress and the removal of water from the soil. This increase in effective stress of the soil can be caused by a building foundation or other loads on the soil. Consolidation causes settlement of the soil (Consolidation settlement) due to deformation or relocation of soil particles. . Two types of consolidation settlements can be identified; •Primary consolidation settlement: This involves the reduction of volume of a saturated soil due to excess pore pressure being generated. Primary consolidation takes place very rapidly. (As soon as the soil is loaded) •Secondary consolidation settlement: This type of settlement involves the reduction of volume due to the adjustment of soil particles. Secondary consolidation settlement occurs much slower providing an ideal period for predicting the rate of settlement. Other factors influence the consolidation of a soil. These factors include; the stress history (Pre-consolidated pressures), void ratio (Permeability), degree of saturation, and the structure (Nature/Homogeneity) of the soil. The Oedometer test investigates the 1-D consolidation behaviour of fine grained soils. In this experiment, a soil sample of clay will be subjected to a compressive stress by applying a constant vertical load for a duration of 24 hours whilst recording at time intervals. The compression is recorded using a highly sensitive dial gauge.
The aim of this experiment was to investigate the consolidation and swelling process of a sample of clay by using a simple odometer test to gather settlement data and then using it to calculate parameters such as voids ratio, consolidation parameters, constrained modulus, permeability and the consolidation coefficient of the soil. 3.0 METHODOLOGY
The following equipment was used during the consolidation test; * An undisturbed soil sample (Clay)
* A consolidation ring: Used to hold the soil in place
* Two porous plates : These allow the flow of water out of the soil in two directions (2-way drainage) * A water jacket : This provides a...