Manual of Geotechnical Laboratory Soil Testing

Bashir Ahmed Mir

• Editorial: CRC Press
• Año: 2021
• ISBN:
  9781000456950
• Edición: 1
• Categoría: Tecnología e ingeniería
• Categoría: Ingeniería civil

Manual of Geotechnical Laboratory Soil Testing covers the physical, index, and engineering properties of soils, including compaction characteristics (optimum moisture content), permeability (coefficient of hydraulic conductivity), compressibility characteristics, and shear strength (cohesion intercept and angle of internal friction). Further, this manual covers data collection, analysis, computations, additional considerations, sources of error, precautionary measures, and the presentation results along with well-defined illustrations for each of the listed tests. Each test is based on relevant standards with pertinent references, broadly aimed at geotechnical design applications.

FEATURES

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• Provides fundamental coverage of elementary-level laboratory characterization of soils

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• Describes objectives, basic concepts, general understanding, and appreciation of the geotechnical principles for determination of physical, index, and engineering properties of soil materials

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• Presents the step-by-step procedures for various tests based on relevant standards

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• Interprets soil analytical data and illustrates empirical relationship between various soil properties

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• Includes observation data sheet and analysis, results and discussions, and applications of test results

This manual is aimed at undergraduates, senior undergraduates, and researchers in geotechnical and civil engineering.

Prof. (Dr.) Bashir Ahmed Mir is among the senior faculty of the Civil Engineering Department of the National Institute of Technology Srinagar and has more than two decades of teaching experience. Prof. Mir has published more than 100 research papers in international journals and conferences; chaired technical sessions in international conferences in India and throughout the world; and provided consultancy services to more than 150 projects of national importance to various government and private agencies.

1 Natural Water Content of a Soil Sample

DOI: 10.1201/9781003200260-1

1.1 Objectives

Natural water content (w_n) is a parameter which has direct bearing on the shear strength of fine grained soils in soil engineering practice. Therefore, the main objective of determination of natural moisture content is to evaluate and understand the engineering behaviour of fine grained soils. This parameter has been very helpful in the development of correlations among various properties of soils so as to assess the consistency classes of fine grained soils in the field.

Since the soil is a user-friendly material abundantly available throughout the universe, it is only the water that makes it a problematic material for sustainable development. Therefore, it is mandatory to quantify the water content in the soil mass to assess the compressibility and stability problems in a soil mass due to presence of natural water content.

1.2 Introduction

Water on, above, and below the ground surface may exist in different forms such as liquid, gaseous, (e.g. vapors) or solid (e.g. frozen ice) states. Water below or underneath ground surface is termed as subsurface water. At varying depths under the ground surface, there is a zone of saturation in which water fills all the pores in the soils and the openings in the underlying rock. The water in the zone of saturation is commonly termed as “ground water,” its upper surface being the “ground water table or water table” of phreatic surface, which has the atmospheric pressure.

The term “water” and “moisture” may be interchangeably used to describe all kinds of subsurface water, except gravitational water (ground water is free or gravitational and moves by obeying the law of gravity in contrast to the “attached or sorbed” water), to which the term “moisture” is not applied. The interstices between soil particles beyond ground water table contain some water which is termed “vadose” (e.g. water between the ground surface and the water table) by geologists. In engineering terms, it is known as moisture or simply “water” or moisture content. Thus, the water present in the soil voids or any other material is generally termed as the natural moisture content. Natural water content (w_n) is used to access the state of compactness of in situ soils. The natural moisture content can be determined either on volume basis (known as volumetric moisture content) or mass/weight basis (known as gravimetric moisture content). The water content is always expressed as percentage (%) defined as below:

$\begin{array}{c}w=\frac{W_w}{W_s}\ast 100(\%)\mathrm{.}.basedonWt.ofsoilsampleknownasgravimetricwatercontent\\ w=\frac{V_w}{V_s}\ast 100(\%)\dots basedonVol.ofsoilmassknownasvolumetricwatercontent\end{array}\}0\le \mathrm{w}\le \infty$[1.1]

Where: V_W = volume of water (cm³) in a soil sample

V_S = volume of solids in a soil sample

W_W = weight of water in a soil sample, and

W_S = weight of soil solids or dry weight of soil sample

e.g. Range of water con...