Laboratory Testing of Soils

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Laboratory Testing of Soils

Introduction

Ground conditions will affect a number of civil engineering practices when building structures. For example, ground conditions affect the sort of foundation you use. We need to assess the stability of the ground and its likelihood to slide and collapse. The water content of the grounds, affected by the amount of rainfall penetrating into the ground and the rate of groundwater flowing away from the site also needs to be considered. How quickly the groundwater and the pollutants it carries and enters a reservoir or river will affect the susceptibility of such bodies of water to flood and also the quality of the local water.

A geotechnical engineer needs to be able to identify the site ground conditions, the properties of the soil present and how the ground will behave under load and varying water conditions. When civil engineering projects are carried out, it is important to determine what materials are present in the ground being developed and measure their characteristics. Laboratory testing needs to be carried out before the design and construction by the engineer in order to characterise the raw materials and allow prediction of their performance during and after construction. These tests are also required to ensure proper control of ongoing construction projects.

In this unit we will be using the following laboratory tests to characterise granular and cohesive soils:

  • Sieve Analysis for the characterisation of granular soils
  • Characterisation of cohesive soils using :-
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  1. Atterberg Limits (Liquid Limit Test and Plastic Limit Test
  2. Compaction test using a Standard Proctor test

  • Identification of rocks by their key characteristics


Characterisation of granular soils

Granular materials can be characterised based on particle size using a sieve analysis. Below are the results obtained from the experiment.

  • Table 1 shows the sieve analysis for sand
  • Table 2 shows the sieve analysis for gravel

Sieve Analysis Results

Table 1 – Sand Sieve Analysis Results

Table 2 – Gravel Sieve Analysis Results 

 

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