Environmetal Soil Properties and Behaviour

ardous solid waste) containment and isolation. He is currently engaged in 
research on issues in geoenvironmental sustainability.
Dr. Masashi Nakano is emeritus professor of soil physics and soil hydroge-
ology at the University of Tokyo and director of the RISST (Research Institute 
of Soil Science and Technology), Japan. He has worked and educated many 
students as a professor of the University of Tokyo and has published many 
significant papers on mass transport in soils in the fields of soil physics and 
soil hydrology. He has served as a leader of land reclamation engineering for 
food production, a promoter of global environment research such as IGBP 
(The International Geosphere\u2013Biosphere Programme) in Japan, and a coun-
sellor for the research by JAEA (Japan Atomic Energy Agency) and its pre-
decessors on clay barrier systems for radioactive wastes disposal since the 
inception of plans in Japan. He was recently a member of the Science Council 
of Japan and is now working on such issues in soil/clay science as adsorption/
transport of chemicals on soils and mineral corrosion by microorganisms.
Dr. Roland Pusch is emeritus professor at Lund University, Sweden, and is 
presently guest professor at Luleå Technical University, Sweden, and honor-
ary professor at East China Technological Institute. He has made significant 
contributions in research on the microstructure of clays and their impact 
on the properties and performance. He has been very active, nationally and 
internationally, in pioneering work on clay buffers and underground reposi-
tory systems for HLW containment in association with Swedish Nuclear Fuel 
and Waste Management Company (SKB) and the European Commission. He 
has long been active in EU projects relating to HLW and HSW containment 
and isolation. He is currently the scientific head and managing director of 
Drawrite AB, Sweden, and is working on issues of long-term stability of clay 
buffers in HLW repositories and on design and performance of hazardous 
landfills.
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1
1
Origin and Function of Soils
1.1 Introduction
We begin by establishing what is a soil. In the most general sense, a soil is 
a collection or accumulation of disintegrated rock fragments whose particle 
sizes can range from boulders measuring up to a few metres in dimension to 
much lesser sizes generally called soil, with particle sizes ranging somewhere 
close to 100 mm to sizes that cannot be seen by the naked eye\u2014less than 
0.0001 mm (in the micrometre range). Disintegration of rock produces frag-
ments commonly referred to by the public as boulders, stones, gravel, sand, 
and clay\u2014most often distinguished or characterized by particle (fragment) 
sizes, with the largest ones being stones and the smallest ones being clay. 
The forces and agents responsible for rock disintegration include mechani-
cal, chemical, biologically mediated, and hydraulic.
Practical experience and reports in the popular literature have often 
shown differences in one\u2019s perception of what constitutes a soil, the reasons 
for which most generally lie in one\u2019s use and understanding of the soil mate-
rial. Strictly speaking, soil materials could also include decomposed organic 
matter and other constituents such as evaporates. We use the term soil mate-
rial in recognition of the fact that soil is a material consisting of various soil 
fractions identified as sand, silt, clay, organic matter, carbonates, oxides, and 
so forth. The term soil is now commonly used in place of soil material to mean 
the same thing. The nature and characteristics of the soil fractions constitut-
ing a soil will be discussed in greater detail in the next chapter.
1.1.1 Why Are We Concerned with Environmental Issues?
The very same forces and agents, which we will call environmental forces/
agents, responsible for rock disintegration will persist after rock fragmenta-
tion. They will continue to act on the fragmented material (i.e., soil material), 
and in many instances, they will act in combination with forces result-
ing from actions associated with anthropogenic activities. One can expect 
that the nature of the various soil fractions constituting a soil material will 
change over time.
2 Environmental Soil Properties and Behaviour
Changes in the nature of soil will be reflected in associated changes in the 
properties and characteristics of the affected soil. Because of this, it becomes 
important to recognize that if, for example, one designs and constructs an 
engineering facility that relies on various predetermined soil properties such 
as soil strength and hydraulic conductivity for its long-term survivability, 
any deterioration or degradation of these properties would threaten its sur-
vival. This means that unless changes in the measured soil properties used 
for design of an engineering facility are anticipated and factored into design 
considerations, the survival of the constructed facility could be jeopardized 
if negative changes in these properties occur. A very pertinent example of 
this is the engineered clay barrier used in containment of waste products. 
For secure long-term containment, one relies on the hydraulic transmission 
and chemical buffering properties to maintain their design capabilities. It 
goes without saying that deterioration of any of these properties will allow 
transport contaminants into the surrounding regions, thereby impacting the 
health of the various vegetative species and biotic receptors.
One needs therefore to (a) focus attention on the kinds of changes that will 
occur in soil due to the impact of environmental forces/agents and actions 
associated with anthropogenic activities, (b) provide an appreciation of what 
the environmental agents and anthropogenic activities are, and what kinds 
of forces/stresses are associated with these agents and activities, (c) discuss 
the impacts and various processes involved with these forces/stresses, and 
(d) establish the likely changes in the various soil properties and show how 
these impact on performance of the affected soils.
1.2 Soil Origin and Formation
There are several factors that control or influence the processes that are 
involved in producing the type of soil from parent rocks. Most obviously, the 
type of rock (composition and texture) leads the group of factors in terms of 
importance. This is closely followed by site conditions such as availability 
of water, climate, topography, and so forth. These factors have considerable 
influence on the kind of processes involved in breaking down rock to its vari-
ous fragments, and also in the production of soil types from the broken rock 
fragments.
1.2.1 Parent Material
Rocks that when fragmented will eventually form soils are called parent 
material. They can also be referred to source rocks. These kinds of rocks fall 
into three general classes: igneous, sedimentary, and metamorphic. Igneous 
rocks are the product of magma. When they are the result of extruded 
3Origin and Function of Soils
lava, they are known as extrusive rocks. When the rocks are the result of 
unextruded magma, they are known as intrusive or plutonic rocks depend-
ing on the depth of the magma. The rate of cooling of the magma has a great 
influence on the size of mineral grains formed in the rocks. These minerals 
are important participants in the development of soil properties and char-
acteristics. With higher rates of cooling in the extrusive rocks, one would 
expect the mineral grains to be fine, that is, very small. Slower rates of cool-
ing will produce larger mineral grains. Since plutonic rocks are found at a 
greater depth than intrusive rocks, the mineral grains of the plutonic rocks 
will be larger than those found in intrusive rocks. Of the various kinds of 
igneous rocks such as andesite,