CEOR CH 3

earthbound

Most civil engineering structures are ______. They sit on soil and rock ground directly or on constructed foundations that transfer the load to the soil or rock below.

Geotechnical Engineering

is the technical specialty that deals with soil and rock as supporting materials for structures.

Geotechnical Engineering

It deals with the various foundation types that work between the structure and the ground.

Geotechnical Engineering

In addition, it deals with the stability of soil or rock slopes whose failure may cause loss of human lives or damage to property.

Geology

is a basic science that is concerned with the study of the history of the Earth, the rocks of which it is composed and the changes that it has undergone or is undergoing.

Geology

is the science of rocks and earth processes.

Engineering geology

deals with the application of geologic fundamentals to engineering. One obvious example is the mapping of active seismic faults that are to be avoided when making plans for human habitat development, roadway construction, or power plant construction. At a more fundamental level, understanding various geological formation and rock types provides geotechnical engineers the knowledge necessary in assessing the suitability of a site for human activities

Soils

are formed from rock as it is acted upon by physical, chemical, and biological forces.

soil

The extent to which a parent rock changes to a ____ is a function of the rate and overall time of the prevailing reactions and processes.

from an engineering viewpoint

, soil is any earthy material that can be removed with a spade, shovel or bulldozer and is the product of natural weathering. This soil includes gravel and sand deposits;

from a geological viewpoint

soil may be considered as the superficial unconsolidated mantle of disintegrated and decomposed rock material

from a pedological (soil science) viewpoint

soil is the weathered transformation product of the outermost layer of the solid crust, differentiated into horizons varying in type and amounts of mineral and organic constituents, usually unconsolidated and of various depths

Rocks

serve as parent material for natural soil formation

Rocks

They are also used as ground foundation support and the crushed rock fragments are used as major construction materials

Strong

for heavy structures. granite, basalt

Moderate

sanctstone Limestone

Weak

sanctstone Limestone. Weak for stabilization -shale, chalk

Igneous rocks

solidified from a molten or partly molten siliceous solution.

extrusive igneous rocks

When magma cools and solidifies in direct contact with the atmosphere it is referred to as

intrusive igneous rocks

while cooling in the subsurface leads to an

Sedimentary rocks

naturally consolidated or unconsolidated transported materials.

Metamorphic rocks

result of subjecting igneous or sedimentary rocks to elevated temperatures and pressures

80%, 15%, 5%, igneous, metamorphic, sedimentary

Igneous rocks comprise about ___ and metamorphic rocks about ___ of the terrestrial and sub-oceanic earth crust, leaving about ___ for the sedimentary rocks. Common rock examples include granite and basalt ___, sandstone and limestone, and schist and gneiss.

Structural Geology

study of the ways in which rocks or sediments are arranged and deformed on the earth. It involves all three rock types: igneous, sedimentary, and metamorphic

sedimentary rocks

We will focus on ______. _______ are deposited in horizontal layers

formation

Any rock unit that is recognizable and mappable in the field is called

Formations

can include different rock types (so long as the entire package can be distinguished from adjacent formations).

members

Sometimes formations are further subdivided into

contacts

The boundaries between formations are called

contacts

These boundaries can be depositional, erosional, or structural

Map view

Generally, geologists can only see the rocks that are at the earth's surface. This two-dimensional view of rock distribution is called the

geologic cross-section

view of a vertical slice of the earth, like you might see at a road cut or a stream cut.

block diagram

combination of those two representations and gives a 3-D view of formations and contacts. It looks like a block, and shows a map view on top, and a cross-sectional view on each of its visible sides

cross-sectional view

can reveal details of a structure not visible in map view, such as cross bedding.

folds, faults, joints and unconformities

Geological structures, such as ___, ____, ____ encountered in geology are regularly encountered in civil engineering work.

Folds

are defined as wavy undulations developed in the rocks of the Earth's crust due to horizontal compression resulting from gradual cooling of the Earth's crust, lateral deflection and intrusion -tunneling cand of magma in the upper strata.

fold axis

Note that the rocks are bent around an imaginary line called a

fracture

where the continuity of the rock mass breaks

Faults

fractures in crustal strata along which appreciable shear displacement of the adjacent rock blocks have occurred relative to each other, probably due to tectonic activities

fault plane

fracture along which the shear displacement has taken place is called a

joint

fracture where little or no movement has taken place. This is the most common form of discontinuity encountered.

active faults

no build Zone for critical infrastructures

discontinuities

occur in several sets and are approximately parallel within a specific set. The natural breaks in rock masses

Anisotropic

a series of discontinuities that have the same geologic origin, orientation, spacing and mechanical characteristics. The discontinuities make the rock mass

Anisotropic

is a material whose physical, mechanical property, etc., are not all the same in each direction.

unconformity

is the surface/ plane of separation between two series of rock beds/geological formations that belong to two different geologic ages and they are, in most cases, different in their geologic structure

unconformity

occurs when there is erosion of a layer or layers of deposited rock followed by the deposition of new sedimentary rock on top. It is called an _______ because the ages of the layers of rock that are abutting each other are discontinuous at the ____

Disconformity

Sedimentary layer deposited over eroded horizontal sedimentary layer

Angular unconformity

Sedimentary layer deposited over eroded angular (tilted or foided) rock

Nonconformity

Sedimentary layer deposited over eroded igneous or metamorphic rock

Soil mechanics

branch of mechanics that studies the mechanical properties of various types of soil and its strength at different moisture-content levels. It provides the scientific base upon which design formulas and codes are developed for everyday engineering design practice.

Karl von Terzaghi

Father of Modern Soil Mechanics

Foundations

“can appropriately be described as a necessary evil”

Foundations

merely serve as a remedy for the deficiencies of whatever whimsical nature has provided for the support of the structure at the site which has been selected.

Foundations

have always been treated as step children; and their acts of revenge for the lack of attention can be very embarrassing.

solid particles, liquid and gas

Soil is not a coherent solid material like steel and concrete but is a particulate material. Soil mass is generally a three-phase system. It consists of

relationships

The inter ____ of the different phases are important since they help to define the condition or the physical make-up of the soil

Voids

the spaces in between the materials

Soil Permeability

ability of the soil to let water flow through it

permeable

material is ___ if it contains continuous voids.

Soil Permeability

has a decisive effect on the stability of foundations, seepage loss through embankments of reservoirs, drainage of subgrades, excavation of open cuts in water bearing sand, rate of flow of water into wells and many others.

Seepage

Movement of water through soil due to differences in water pressure

Piping

is a phenomenon by which the soll on the downstream sides of some hydraulic structures get lifted up due to excess pressure of water

seepage force or pressure

The pressure that is exerted on the soil due to the seepage of water is called the

Seepage

As water seeps through the soil it pushes on the soil grains

Pore Water Pressure

pressure carried by water inside the soil voids

intergranular or effective pressure

pressure transmitted through grain to grain at the contact points through a soil mass is termed as

effective pressure

this pressure is responsible for the decrease in the void ratio or increase in the frictional resistance of a soil mass

pore water pressure or neutral stress

If the pores of a soil mass are filled with water and if a pressure induced into the pore water, tries to separate the grains, this pressure is termed as

pore water pressure

The effect of this pressure is to increase the volume or decrease the frictional resistance of the soil mass.

vertical stresses

Estimation of ____ at any point in a soil-mass due to external vertical loadings are of great significance in the prediction of settlements of buildings, bridges, embankments and many other structures.

elastic theory

constant ratios exist between stresses and strains. For the theory to be applicable, the real requirement is not that the material necessarily be elastic, but there must be constant ratios between stresses and the corresponding strains.

elastic theory

may be assumed to hold so long as the stresses induced in the soil mass are relatively small

Boussinesq Solution

Assumes soil is elastic, homogenous and isotropic. It is good for general use

Westergaard Solution

Assumes soil has a stratified Westerguard Solution structure with reinforcement-like behavior

point loads

The formulas that are most widely used are the Boussinesq and Westergaard formulas. These formulas were first developed for _____ acting at the surface. These formulas have been integrated to give stresses below uniform strip loads and rectangular loads

Infinite soil mass

extends infinitely in all directions

Finite depth with rigid base

soil layer above rock or very stiff Stratum

two, three

Structures are built on soils. They transfer loads to the subsoil through the foundations. The effect of the loads is felt by the soil normally up to a depth of about ___ to __ times the width of the foundation

compression

of the soil mass leads to the decrease in the volume of the mass which results in the settlement of the structure.

Compressibility

tendency of soil to decrease in volume when subjected to load

consolidation

A portion of the applied stress is transferred to the soil skeleton, which in tum causes a reduction in the excess pore pressure. This process, involving a gradual compression occurring simultaneously with a flow of water out of the mass and with a gradual transfer of the applied pressure from the pore water to the mineral skeleton is called

swelling

which involves an increase in the water content due to an increase in the volume of the voids

Shear Strength in Soil

One of the most important and the most controversial engineering properties of soil, ability to resist sliding along internal surfaces within a mass

Soil Exploration

field and laboratory investigations required to obtain the essential information on the subsoil is called

Natural slopes

those that exist in nature and are formed by natural causes

manmade slopes.

The sides of cuttings, the slopes of embankments constructed for roads, railway lines, canals elc. and the slopes of earth dams constructed for storing water are examples of

infinite slope

used to designate a constant slope of infinite extent. The long slope of the face of a mountain is an example of this type,

finite slopes

limited in extent, The slopes of embankments and earth dams are examples

Slope stability

extremely important consideration in the design and construction of earth dams.

Lateral Earth Pressure

horizontal pressure theit soil or material exerts on structures

retaining walls

Structures that are built to retain vertical or nearly vertical earth banks or any other material are called

Rock Mechanics

subject concerned with the study of the response of rock to an applied disturbance caused by natural or engineering processes.

minerals

The earth materials that constitute relatively the thin outer shell, called crust, of the Earth are arbitrarily categorized by civil engineers as soils and rocks. These materials are made up of small crystalline units known as

mineral

basically a naturally occurring inorganic substance composed of one or more elements with a unique chemical composition, unique arrangement of elements (crystalline structure) and distinctive physical properties.

rock

hard, compact and naturally occurring earth material composed of one or more minerals and is permanent and durable for engineering applications

Rock Engineering

deals with the engineering applications of the basic principles and the information available in the subjects of engineering geology and rock mechanics in an economic way

rock mass

applies to a large extent of rock, from several metres to few kilometres, which can include many discontinuities of different forms

Dip

also known as the true dip, is the steepest inclination of the plane to horizontal.

true dip

maximum angle of slope of the plane