Geomechanics in Soil, Rock, and Environmental Engineering

John Small

• Publisher: CRC Press
• Year: 2018
• eBook ISBN:
  9781498739320
• Topic: Tecnología e ingeniería
• Subtopic: Ingeniería civil

Utilizes both Computer- and Hand-Based Calculations…

Modern practice in geomechanics is becoming increasingly reliant on computer-based software, much of which can be obtained through the Internet. In Geomechanics in Soil, Rock, and Environmental Engineering the application of these numerical techniques is examined not only for soil mechanics, but also for rock mechanics and environmental applications.

… For Use in Complex Analysis

It deals with the modern analysis of shallow foundations, deep foundations, retaining structures, and excavation and tunneling. In recent years, the environment has become more and more important, and so it also deals with municipal and mining waste and solutions for the disposal and containment of the waste. Many fresh solutions to problems are presented to enable more accurate and advanced designs to be carried out.

A Practical Reference for Industry Professionals, This Illuminating Book:

• Offers a broad range of coverage in soil mechanics, rock mechanics, and environmental engineering
• Incorporates the author's more than 40 years of academic and practical design experience
• Describes the latest applications that have emerged in the last ten years
• Supplies references readily available online for futher research

Geomechanics in Soil, Rock, and Environmental Engineering

should appeal to students in their final undergraduate course in geomechanics or master's students, and should also serve as a useful reference to practitioners in the field of geomechanics, reflecting the author's background in both industry and academia.

Chapter 1

Basic concepts

1.1 INTRODUCTION

In later chapters of this book, various terminologies are used and standard soil mechanics tests are referred to, therefore, this chapter provides some background on these basic tests and concepts. More details on testing of soil and rock are provided in the National and International Standards that are referred to in this and later chapters.

1.2 BASIC DEFINITIONS

Soil is considered to consist of the soil grains and the voids that exist between them. The voids can contain air and water, and so may be considered fully saturated if the voids are full of water or partially saturated if air and water fill the voids. Sedimentary rocks also consist of soil grains, but cementing that is present makes the rock stronger and less deformable than a soil.

Generally, soils subjected to moderate stress levels deform through changes in the void space in the soil, although calcareous soils will undergo volume change through particle crushing. At high pressures, soil grains will eventually crush, but in most soil mechanics applications, the particles are considered non-deforming.

The concept of a soil for engineering purposes is therefore as shown in Figure 1.1.

The void ratio e of a soil is defined as the volume of the voids to the volume of the solid soil particles and is defined as

$e=\frac{V_v}{V_s}=\frac{V_a+V_w}{V_s}$

(1.1)

where V_a is the volume of air in the voids, V_w is the volume of water in the voids, V_s is the volume of solids, and V_v is the volume of voids in a given total volume V_Tot of soil. Sometimes it is more convenient to work with the porosity n of a soil where the porosity is defined as

$n=\frac{V_v}{V_{\text{Tot}}}=\frac{V_a+V_w}{V_a+V_w+V_s}$

(1.2)

A very useful property of a soil is its water or moisture content that is usually given the symbol w or m and is usually expressed as a percentage. If the weight of water is w_w and the weight of solids is w_s, then we can write

$m=\frac{w_w}{w_s}\times 100\%$

(1.3)

Figure 1.1 Three-phase soil model.

The degree of saturation S is a measure of how much of the voids of the soil are filled with water

$S=\frac{V_w}{V_v}\times 100\%$

(1.4)

Another important measure of a soil’s properties is its unit weight. The saturated unit weight γ_sat is calculated for a soil with voids fully saturated with water, that is, S = 100%.

${\text{γ}}_{\text{sat}}=\frac{w_s+w_w}{V_{\text{Tot}}}$

(1.5)

The dry unit weight γ_dry of a soil is calculated for no water in the voids

${\text{γ}}_{\text{dry}}=\frac{w_s}{V_{\text{Tot}}}$

(1.6)

The soil may be in a state of saturation between the dry and totally saturated case (0 ≤ S ≤ 100%), where the voids contain some air and some water. In this case, the bulk unit weight γ_bulk is calculated from

${\text{γ}}_{\text{bulk}}=\frac{w_s+w_w}{V_{\text{Tot}}}$

(1.7)

Unit weights are expressed in kN/m³ or lbf/ft³ as they are expressed in terms of the weight as a force. A typical unit weight for a soil may be 19 kN/m³ or 120 lbf/ft³. The unit weight of water is 9.81 kN/m³ as the acceleration due to gravity is 9.81 m/sec².

The density of a soil ρ is sometimes used in calculation and the density is defined as the mass of a soil per unit volume. For example, the bulk density may be calculated from

${\text{ρ}}_{\text{bulk}}=\frac{m_s+m_w}{V_{\text{Tot}}}$

(1.8)

The density of a soil is expressed as the mass of soil per unit volume and has units of kg/m³ or lb/ft³. A typical value might be 2000 kg/m³ or 125 lb/ft³. The density of fresh water is approximately 1000 kg/m³ or 62.4 lb/ft³ (as it depends on temperature).

With sands and gravels, o...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Acknowledgments
• 1 Basic concepts
• 2 Finite layer methods
• 3 Finite element methods
• 5 Shallow foundations
• 6 Deep foundations
• 7 Slope stability
• 8 Excavation
• 9 Retaining structures
• 10 Soil improvement
• 11 Environmental geomechanics
• 12 Basic rock mechanics
• References
• Index