COLLEGE OF ENGINEERING

DEPARTMENT OF GEOLOGICAL ENGINEERING

ASSIGNMENT ON FAILURE MODES ON A SLOPE FACE USING DIPS APPLICATION

AND

STANDARD FORMATTING PROCEDURES ON SOME GIVEN QUESTIONS

NAME: DZAKLO COURAGE KWASI

INDEX NUMBER 7739312

COURSE

COURSE CODE

COMPUTER APPLICATION (INCLUDING ENG. GEOLOGY)

G E D 359

ASSIGNMENT TYPE MIDSEMESTER EXAMS

DATE 26/11/2014

1 | C O M P U T E R A P P L I C A T I O N S

Table of Contents

1 CHAPTER ONE: DETERMINATION OF TYPE FAILURE THAT WILL OCCUR IN

A GIVEN SLOPE. ..................................................................................................................... 4

1.1 DATA FOR THE ANALYSIS: .................................................................................. 4

1.2 STEREONETS PLOTTED: ........................................................................................ 4

1.2.1 TOPPLING failure analysis: ................................................................................ 5

1.2.2 PLANAR SLIDING failure analysis: .................................................................. 6

1.2.3 WEDGE SLIDING failure analysis: .................................................................... 7

1.3 CONCLUSION: .......................................................................................................... 7

2 CHAPTER TWO: THE CONTRIBUTION OF AN ENGINEERING GEOLOGIST IN

NATIONAL DEVELOPMENT ................................................................................................ 8

2.1 Engineering: ................................................................................................................ 8

2.2 Geologist: .................................................................................................................... 8

2.3 Engineering geologist:................................................................................................. 8

2.4 Contributions of engineering geologist in national development: .............................. 8

2.5 Conclusion:.................................................................................................................. 9

3 CHAPTER THREE: STAGES OF INVESTIGATION IN ENGINEERING GEOLOGY.

9

3.1 Introduction: ................................................................................................................ 9

3.2 Project conception stage: ............................................................................................. 9

3.3 Preliminary investigation stage: ................................................................................ 10

3.4 Main investigation stage: .......................................................................................... 10

3.5 Construction investigation stage: .............................................................................. 10

3.6 Post construction stage investigation: ....................................................................... 11

3.7 CONCLUSION: ........................................................................................................ 11

4 CHAPTER FOUR: TROPICAL WEATHERING, LATERITIZATION PROCESS AND

LATERITES. ........................................................................................................................... 11

4.1 Weathering of rocks: ................................................................................................. 11

4.2 Tropical weathering: ................................................................................................. 12

4.3 Lateritization process: ............................................................................................... 12

4.4 Laterites: .................................................................................................................... 14

4.5 CONCLUSION: ........................................................................................................ 14

5 CHAPTER FIVE: EFFECTS OF WATER ON THE ENGINEERING PERFORMANCE

OF ROCKS AND SOIL MASSES. ......................................................................................... 15

5.1 Water, soils and engineering: .................................................................................... 15

5.2 Water, Rocks and engineering: ................................................................................. 15

2 | C O M P U T E R A P P L I C A T I O N S

5.3 Effects of water on the engineering performance of rocks and soil masses: ............ 15

5.4 CONCLUSION: ........................................................................................................ 16

6 CHAPTER SIX: ENGINEERING SIGNIFICANCE OF FOLDS AND FAULTS: ....... 17

6.1 Folds: ......................................................................................................................... 17

6.2 Faults: ........................................................................................................................ 18

6.3 Engineering significance of folds and faults: ............................................................ 18

6.4 CONCLUSION: ........................................................................................................ 18

7 CHAPTER SEVEN: FOUR FACTORS THAT AFFECT THE STRENGTH OF ROCK

MATERIALS. .......................................................................................................................... 19

7.1 Strength of rock materials: ........................................................................................ 19

7.1.1 TEMPERATURE: ............................................................................................. 19

7.1.2 CONFINING PRESSURE: ................................................................................ 19

7.1.3 ROCK TYPES: .................................................................................................. 19

7.1.4 TIME: ................................................................................................................. 19

7.2 CONCLUSION: ........................................................................................................ 19

8 CHAPTER EIGHT: ENGINEERING PROBLEMS ENCOUNTERED ON SOME SOIL

DEPOSITS DURING CONTRUCTION:................................................................................ 20

8.1 GLACIAL DEPOSITS:............................................................................................. 20

8.2 ALLUVIAL DEPOSITS: .......................................................................................... 20

8.3 SWAMPY/PEATY DEPOSITS: .............................................................................. 21

8.4 CONCLUSION: ........................................................................................................ 21

REFERENCES: …………………………………………………………………………….

3 | C O M P U T E R A P P L I C A T I O N S

LIST OF STEREONETS

STEREONET 1-1: TOPPLING FAILURE DIAGRAM. .......................................................... 5

STEREONET 1-2: PLANAR SLIDING FAILURE DIAGRAM. ............................................ 6

STEREONET 1-3: WEDGE SLIDING DIAGRAM. ................................................................ 7

LIST OF TABLES

Table 1-1: data for the analysis including the types of structures.............................................. 4

LIST OF FIGURES

Figure 1-1: cross-section of the pit slope and various benches ................................................. 5

Figure 4-1: A represent SOIL; B represent laterite; C represent saprolite, a less-weathered

regolith; D represent bedrock................................................................................................... 13

Figure 4-2: laterite-saprolite cross-section............................................................................... 13

Figure 4-3: a man cutting laterites into bricks. ........................................................................ 14

Figure 5-2: illustration of pore water pressure on porous rocks. ............................................. 16

Figure 6-1: A TYPICAL DIAGRAM OF A FOLD. ............................................................... 17

Figure 6-2:A DIAGRAM OF A FAULTING RESULTS. ...................................................... 18

Figure 8-1:ALLUVIAL DEPOSIT. ......................................................................................... 20

4 | C O M P U T E R A P P L I C A T I O N S

1 CHAPTER ONE: DETERMINATION OF TYPE FAILURE THAT WILL

OCCUR IN A GIVEN SLOPE.

1.1 DATA FOR THE ANALYSIS: N0. ORIENT 1 ORIENT 2 QUANTITY TRAVERSE TYPE

1 219 84 1 1 joint

2 350 77 1 1 joint

3 247 84 1 1 joint

4 353 66 1 1 joint

5 241 84 1 1 joint

6 355 62 1 1 joint

7 104 77 1 1 joint

8 338 64 1 1 joint

9 359 68 1 1 bedding

10 211 76 1 1 joint

11 182 66 2 1 joint

12 348 34 1 1 joint

13 213 69 1 1 bedding

14 353 61 1 1 joint

15 216 76 1 1 joint

16 206 59 1 1 joint

17 123 84 1 1 joint

18 87 74 1 1 joint

19 356 63 1 1 bedding

20 213 76 1 1 joint

21 215 77 2 1 joint

22 92 61 1 1 joint

23 97 69 1 1 joint

24 209 5 1 1 bedding

25 3 65 1 1 joint

26 359 67 1 1 shear

27 146 56 1 1 joint

28 346 78 1 1 shear

29 343 76 1 1 joint

30 350 68 1 1 joint

31 350 68 1 1 bedding Table 1-1: data for the analysis including the types of structures.

1.2 STEREONETS PLOTTED: Three stereonets were plotted to identify which type of failure is a risk to the failing of the pit

slope. The overall pit slope angle is 45 degrees. The only traverse in this analysis is the plane

of pit slope which have a dip of 45 degrees and dip direction of 135 degrees. Below is a diagram

of the cross- section of the pit slope with the various benches.

5 | C O M P U T E R A P P L I C A T I O N S

Figure 1-1: cross-section of the pit slope and various benches

1.2.1 TOPPLING failure analysis:

The stereonet diagram from the dips application is display below:

STEREONET 1-1: TOPPLING FAILURE DIAGRAM.

The deepened part of the diagram is the pole toppling region which has no joint pole occurring

there, this means that the pit slope is not at the risk of failing by toppling.

6 | C O M P U T E R A P P L I C A T I O N S

1.2.2 PLANAR SLIDING failure analysis:

The diagram below shows the stereonet for the planar sliding from the dips application;

STEREONET 1-2: PLANAR SLIDING FAILURE DIAGRAM.

From the stereonet above, since there no pole of joint falling in the planar sliding zone, the pit

slope is not at the risk of failing by planar sliding.

7 | C O M P U T E R A P P L I C A T I O N S

1.2.3 WEDGE SLIDING failure analysis:

The diagram below shows the stereonet for the wedge sliding from the dips application;

STEREONET 1-3: WEDGE SLIDING DIAGRAM.

Wedge sliding zone is represented by crescent shaped region. Since no plane intersections

(black dots) fall within this region, wedge sliding failure should not be a concern.

1.3 CONCLUSION: From the data given, and the given traverse, the pit slope will not be at risk of failing from any

of the failing modes.

8 | C O M P U T E R A P P L I C A T I O N S

2 CHAPTER TWO: THE CONTRIBUTION OF AN ENGINEERING

GEOLOGIST IN NATIONAL DEVELOPMENT

2.1 ENGINEERING: Engineering is a discipline that deals in designing of structures, machines and

electronics through the application of scientific knowledge and ingenuity.

2.2 Geologist: The scientist who has knowledge about rocks and soils which made up the Earth and

how they have changed since the Earth was formed.

2.3 ENGINEERING GEOLOGIST: A scientist who is charged to plan, design and construct geological engineering projects.

Engineering geologists commonly work with civil engineers, architects and planners, to ensure

that the geologic factors affecting the location, design, construction, operation and maintenance

of engineering works are recognized and adequately provided for. In other words, is concerned

with the study of geological materials and processes that may affect the construction, for

instance, dams, tunnels, mines, roads and buildings to ensure the safe development of

infrastructure.

2.4 CONTRIBUTIONS OF ENGINEERING GEOLOGIST IN NATIONAL

DEVELOPMENT: This caliber of engineers were given birth to, purposely, to combine knowledge from two

essential fields of studies which are geology and engineering. The main reason for this initiative

was as a result of the challenges geologist and engineers went through in the quest to administer

their skills at the job market and notwithstanding the quality of finished products they

produced. At the job market, say a building firm, geologist are solely interested in the make-

up of the Earth materials and putting names on them whilst the engineers on site are waiting

patiently for these geological names so as to apply their “so-called” mechanics on these Earth

materials. Little do they know that, they are linking two different aspects of science without

knowing the after effects of their actions. This is to affirm that, the composition of Earth

materials is not static at all locations on the Earth, so as their reactions to applied loads. The

strength and stability of some minerals are more desired than others. For the above reason,

“engineering geology” is included in the academic curriculum at higher institutions purposely

to trained scientist that are adequately equipped to collect data, interprets these data and design

an engineering solution to geological engineering projects.

The establishment of engineering geology as a sub-discipline of both geology and engineering

has seen so much achievements and desired more in the near future. Some failures that

surfaced before the existence of engineering geology are subsidence of structures, collapse of

buildings and failing of earth retaining walls, just to mention a few. These abysmal failures

accounted for loss of human lives, properties and money. An engineering geologist knows the

information to seek at the site, at any location and to interpret it accurately and advise the

engineer or design a model to solve the problem. With the help of engineering geologists,

9 | C O M P U T E R A P P L I C A T I O N S

projects such as construction of railroads, dams, highways, buildings and bridges have seen

great improvements relative to the past. This was achieved because of the inner understanding

of geology of the grounds and their specific geologic environments to engineering projects.

For instance, if a geologist says “granite”, an engineer taught of it as a very strong rock which

withstands adverse weather conditions and use it as such. But this same granite can contain

minerals that weathers easily with time, negatively affecting the strength of the rock, hence

the project. Currently, remote sensing, modelling of ground profile into three dimensional

shapes, among others are the technologies used by engineering geologists to improve their

working conditions. Overseeing the progress of specific contracts, planning detailed field

investigations by drilling and analyzing samples of deposits or bedrock and supervising site

and ground investigations are some contributions of engineering geologist.

2.5 CONCLUSION: Engineering geologists serve as a bridge between engineers and geologists. They contributed a

lot in diverse ways such as hydrogeology, civil engineering projects and environmental

protections projects as well. The achievements of engineering geologist in our society leaves

no doubt that they have really contributed to national development.

3 CHAPTER THREE: STAGES OF INVESTIGATION IN

ENGINEERING GEOLOGY.

3.1 INTRODUCTION: For any engineering geology project, investigation is one of the most important part which

reveals the real problems on the site. The data collected from these investigations either prior

to or after the project are put into model which will be studied to determine data viability. The

various stages of investigation in engineering geology are;

a. Project conception stage

b. Preliminary investigation stage

c. Main investigation stage

d. Construction investigation stage

e. Post construction stage investigation

Details of these investigations stages are given below;

3.2 PROJECT CONCEPTION STAGE: After the decision to initiate a project has been taken, a desk study is undertaken of all available

geotechnical, geological and topographical data. The proposed site and its environs should be

examined by an experienced engineering geologist. Collection of relevant information on

salient features of the project and layout map on regional scale on 1:50,000 and 1:250,000

10 | C O M P U T E R A P P L I C A T I O N S

depending on the size of the project. Collection of relevant drawings such as topographical

sheet, contour map prepared by the project if any showing reference points and bench marks

verifying the same on the ground, collection of observed cross sections, longitudinal sections.

Other information necessary for this stage:

1. All available geological and hydrogeological maps, memoirs and published articles in

the scientific journals aerial photographs at all scales.

2. Records of natural hazards such as earthquakes, hurricanes and avalanches.

3. Site investigation and construction reports for adjacent engineering projects.

4. Published articles on the geotechnical properties of the geological units to be found on

the site, hydrogeological and hydrological data, records of any past, present and future

human activities.

3.3 PRELIMINARY INVESTIGATION STAGE: The evaluation of a project at its conception stage may reveal significant gaps in basic

knowledge of the site, so that no recognition of likely problems is possible. In such a case some

preliminary investigation may be required to establish that basic knowledge. This would be

undertaken using relatively simple and inexpensive techniques, such as existing records (maps,

photographs, etc.), geological and engineering geological mapping, geophysics and perhaps

some boreholes. The boreholes could be undertaken partly as an experiment to determine the

best method for the boring, sampling and in situ testing to be undertaken in the main stage of

investigation. At the end of this stage there should be sufficient knowledge of the site to allow

design of the main ground investigation. The first two stages of investigation are sometimes

described as the reconnaissance investigation or feasibility investigation. If a number of sites

are being investigated prior to choosing one for development the feasibility investigation may

give sufficient information to allow the choice to be made.

3.4 MAIN INVESTIGATION STAGE: In the main investigation stage the work done should recover the information required to design

the engineering project. This information is obtained by whatever means are appropriate to the

ground conditions and the nature of the engineering work. It is possible that some of the

investigation work may be difficult and expensive to undertake because of problems of access

to the locations of boreholes or in situ tests. Often these problems are easier to overcome during

the construction of the project when earthmoving equipment is readily available and there is a

great temptation to postpone necessary investigation until construction begins. This temptation

should be resisted for it is possible that postponed items of the main investigation could reveal

ground conditions which would invalidate project design. The client always pays for a ground

investigation; the cheapest way is to commission one and the most expensive.

3.5 CONSTRUCTION INVESTIGATION STAGE: One of the unfortunate facts of site investigation is that the prognoses made in the investigation

reports resulting from the main investigation are seldom absolutely and totally correct. The

construction of the project quite often reveals discrepancies between the ground conditions

forecast and the ground conditions encountered. However, if the investigation is well done the

client will have been warned that some variations in particular aspects of the ground (e.g. depth

to bedrock) must be allowed for and in this way these variations need not cause significant

11 | C O M P U T E R A P P L I C A T I O N S

project re-design and can be accommodated in the contract. The ground conditions encountered

must be monitored, recorded and assessed. If no satisfactory assessment can be made on the

basis of the information recorded then additional investigations must be undertaken to obtain

further data and thence resolve any anomalies. Preparation of large scale 1:100/200 geological

map showing all geological discontinuities, elevation of foundation level as per block size of

the dam and dimension of other appurtenances, recommendation of treatment measures of

shear zones, fault zones in consultation with design engineers based on orientation, severity

and criticality of the features recording the same pictorially and in the text for future reference

and behaviour of structure. Suggestion of additional measures for enhancing safety and

competency of the structure, rock/structure inter relationship. Thorough evaluation of grouting

data and suggestion of additional holes and the sequence of grouting. Correlation of core

recovery, permeability and grout intake, analysis and recording of conclusion. In case of

tunnels, logging on 1:100/200 scale, suggestion of additional/reduction in support measures

concurrent with excavation and in case of large underground excavation verifying of projected

discontinuities in various components and to record their deviation/ change if any and re-

interpretation of the same. Checking up with stress data and to record distresses if

any and recommendation of remedial measures. Identification of appropriate locales for

instrumentation and to gather data on background information. Checking up prognostications

made regarding adverse features/conditions and their actual place of occurrence and suggestion

of final remedial measures. Constantly interacting with design/construction engineers for

suggestion of appropriate measures timely on a day-to-day basis.

3.6 POST CONSTRUCTION STAGE INVESTIGATION:

Adhering to codes on filling and emptying schedule while the structure is put into operation

for the first time. Observation of distress, analysis and suggestion of remedial measures.

Gathering instrumental data for analysis and assurance. In case of alarm signals, attempting

rectification in consultation with design/ construction engineers.

3.7 CONCLUSION: In conclusion, all the various stages of investigations have their peculiar significance to the

total investigation process. Also it can be deduced that without a serious detailed investigation

on a particular project, the project in question stand a great chance of failing. The investigation

process includes the parameters affecting the atmospheric conditions on the project, the

underground parameters are also thoroughly considered and the purpose of the entire project is

also considered. All this make the investigation process an important tool in all projects.

4 CHAPTER FOUR: TROPICAL WEATHERING, LATERITIZATION

PROCESS AND LATERITES.

4.1 WEATHERING OF ROCKS: Weathering of rocks is brought about by physical disintegration, chemical decomposition and

biological activity. The type of weathering which predominates in a region is largely dependent

upon climate, which also affects the rate at which weathering proceeds. The latter is also

influenced by the stability of the rock mass concerned, which in turn depends upon its mineral

12 | C O M P U T E R A P P L I C A T I O N S

composition, texture and porosity, and the incidence of discontinuities within it. Many rocks

were originally formed at high temperatures and pressures and a large part of the weathering

process consists of an attempt to reach a new stability under atmospheric conditions. High

temperature minerals occur in the ultrabasic and basic igneous rocks. Hence such rocks tend to

offer less resistance to weathering than the acid igneous rocks which are largely composed of

soda and potash feldspar, quartz and, to a lesser extent, mica. The latter two minerals are

particularly stable. Generally coarse grained rocks weather more rapidly than do fine grained

types of similar mineral composition.

4.2 TROPICAL WEATHERING: It is a prolonged process of chemical weathering which produces a wide variety in the

thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land

area containing laterites is between the tropics of Cancer and Capricorn.

4.3 LATERITIZATION PROCESS: Laterites are the products of intensive and long lasting tropical rock weathering which is

intensified by high rainfall and elevated temperatures. For a proper understanding of laterite

formation we must focus on the chemical reactions between the rocks exposed at the surface

and the infiltrated rain water. These reactions are above all controlled by the mineral

composition of the rocks and their physical properties (cleavage, porosity) which favour the

access of water. The second relevant factor for the formation of laterites are the properties of

the reacting water (dissolved constituents, temperature, acidity (pH), redox potential (Eh)

which are themselves controlled by the climate, vegetation and the morphology of the

landscape. Tropical and subtropical areas show generally a rather high annual precipitation but

its temporal distribution varies strongly from countries with pronounced and long lasting dry

seasons to equatorial areas with a more continuous precipitation. Chemical weathering slows

down in dry seasons at least above the fluctuating water table. Aqueous dissolution of minerals

proceeds when a chemical equilibrium is not arrived i.e. when the dissolved constituents are

removed in the water.

The chemical reactions are further controlled by the activity of water which is equal to one in

freely moving water but lowered within small pores in the soil. Stability and reaction rate vary

from mineral to mineral; e.g. quartz is more stable than feldspar. Minerals of the same species

e.g. kaolinite can show different crystallinity which equally controls their stability.

Strongest alteration proceeds at the surface of the parent rock whereas it is lower in the

regolith above the rock. The principal effects of the various factors on laterite formation are

well known but it is difficult to determine them in space and time in the field. In the practise

of laterite research most valuable information are obtained by detailed studies of complete

weathering sections (laterite profiles) reaching from the unweathered parent rock to the

strongly altered surface layer. Sections showing physical disturbances as erosion or importation

of transported material should be omitted to exclude effects other than weathering. An adequate

number of laterite profiles on different parent rocks has been analysed which enable a clear

understanding of the basic processes of lateritization.

A modern laterite definition should comprise all products of intensive tropical weathering

independent of their parent rocks, which strongly control the composition and the property of

the weathering product. Redbrown laterites on granites, granitic gneisses, clays and shale are

13 | C O M P U T E R A P P L I C A T I O N S

generally hard or harden after drying, whereas laterites and basalts are commonly friable and

show an intensive reddish colour. Lateritization on alkaline rocks (nepheline syenites,

phonolites) often results in formation of highly aluminous laterites (bauxites) with light colour.

On ultramafic rocks (serpentines etc.) forms very soft, yellow-brown Ni-bearing goethite

(nickel limonite ore). The described weathering products are formed by the same fundamental

weathering process and can therefore be interpreted as different members of a laterite family. A

scientific definition proposed in former papers of the author includes all laterite varieties but

excludes weaker weathering products (saprolites). Laterites are here defined as

advanced tropical weathering products with Si: (Al + Fe) ratios below definite limits which on

their part depend on the parent rock composition. This definition is criticized by Australian

geoscientists who prefer a definition allowing a clear identification in the field possibly by a

hand specimen. This request can indeed not be fulfilled considering the broad variety of the

lateritic weathering products. Even the most widespread laterites on acidic rocks cannot be

distinguished from many bog iron ores only by their appearance without additional information

allowing genetic conclusions. The figures below illustrate the formation processes of laterites:

Figure 4-1: A represent SOIL; B represent laterite; C represent saprolite, a less-weathered regolith; D represent bedrock.

Figure 4-2: laterite-saprolite cross-section.

14 | C O M P U T E R A P P L I C A T I O N S

4.4 LATERITES:

Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly

all laterites are rusty-red because of iron oxides. Historically, laterite was cut into brick-like

shapes and used in monument-building. After 1000 CE, construction at Angkor Wat and other

Southeast Asian sites changed to rectangular temple enclosures made of laterite, brick and

stone. Since the mid-1970s, some trial sections of bituminous-surfaced, low-volume roads have

used laterite in place of stone as a base course. Thick laterite layers are porous and slightly

permeable, so the layers can function as aquifers in rural areas. Locally available laterites have

been used in an acid solution, followed by precipitation to remove phosphorus and heavy

metals at sewage-treatment facilities. Laterites are a source of aluminium ore; the ore exists

largely in clay minerals and the hydroxides, gibbsite, boehmite, and diaspore, which resembles

the composition of bauxite. In Northern Ireland they once provided a major source of iron and

aluminium ores. Laterite ores also were the early major source of nickel. The picture below

shows a typical use of laterites:

Figure 4-3: a man cutting laterites into bricks.

4.5 CONCLUSION: Tropical weathering mostly occurs in the tropics, where there is much rainfall and sunshine to

speed up the process. Given the right conditions, the reactions between the rocks and the agents

of weathering can prolong to form laterites. The formation is a complex chemical reactions

where all types of chemical weathering can take place. Laterites on the other hand are useful

in building in the ancient times and even now in some communities.

15 | C O M P U T E R A P P L I C A T I O N S

5 CHAPTER FIVE: EFFECTS OF WATER ON THE ENGINEERING

PERFORMANCE OF ROCKS AND SOIL MASSES.

5.1 WATER, SOILS AND ENGINEERING: Soils consist of grains (mineral grains, rock fragments, etc.) with water and air in the voids

between grains. The water and air contents are readily changed by changes in conditions and

location: soils can be perfectly dry (have no water content) or be fully saturated (have no air

content) or be partly saturated (with both air and water present). Although the size and shape

of the solid (granular) content rarely changes at a given point, they can vary considerably from

point to point. First of all, consider soil as an engineering material - it is not a coherent solid

material like steel and concrete, but is a particulate material. It is important to understand the

significance of particle size, shape and composition, and of a soil's internal structure or fabric.

The term "soil" means different things to different people: To a geologist it represents the

products of past surface processes. To a pedologist it represents currently occurring physical

and chemical processes. To an engineer it is a material that can be:

Built on :( foundations to buildings and bridges).

Built in: (tunnels, culverts, basements).

Built with :( roads, runways, embankments, dams).

Supported: (retaining walls, quays).

Soils may be described in different ways by different people for their different purposes.

Engineers' descriptions give engineering terms that will convey some sense of a soil's current

state and probable susceptibility to future changes (e.g. in loading, drainage, structure, surface

level). Engineers are primarily interested in a soil's mechanical properties such

as: strength, stiffness, permeability. These depend primarily on the nature of the soil grains, the

current stress, the water content and unit weight.

5.2 WATER, ROCKS AND ENGINEERING: Rocks are considered to be hard and durable materials. By an excavation point of view, Rocks

are the earth materials that cannot be excavated without blasting. This definition clearly

excludes other kinds of earth materials such as soils, and glacial tills, etc. Here is another

engineering definition of rocks: The earth materials that do not slake when soaked into water.

For example, a thick loess deposit is regarded as rock geologically and regarded as soil in

engineering. Water finds its ways into rocks as a results some geological structures (fractures,

seams, fissures) serving as channels. They somewhat exert pressure on the rock. Rocks are

widely used in projects such as dams, buildings and roads.

5.3 EFFECTS OF WATER ON THE ENGINEERING PERFORMANCE OF ROCKS AND

SOIL MASSES: The strength of soils and rocks are affected when these engineering materials are saturated with

water. Consider a fully saturated clayey soil under a weight of a building, the building will be

subjected to subsidence since the soil will undergo consolidation (i.e. the removal of water

from the soil which results in a decrease in volume).

16 | C O M P U T E R A P P L I C A T I O N S

The influence of pore-water pressure on the behaviour of porous rock in the triaxial

compression tests is illustrated by Figure 5-1. A series of triaxial compression tests was carried

out on a limestone with a constant confining pressure of 69 MPa, but with various level of pore

pressure (0-69 MPa). There is a transition from ductile to brittle behaviour as pore pressure is

increased from 0 to 69 MPa. In this case, mechanical response is controlled by the effective

confining stress (σ3' = σ3 – u).

Figure 5-2: illustration of pore water pressure on porous rocks.

Water content in rocks and soil also turn to dissolve minerals in the materials and reduces the

strength and durability of them. For instance when a limestone is exposed to water, the calcium

carbonate in it dissolves into solution thereby rendering the limestone insufficient for

engineering projects. Most minerals that form the integral part of the rocks are dissolved. The

results of dissolving of minerals results in chemical weathering of the rocks into soils which

will eventually be eroded away.

Sub-soils of civil engineering projects which contain clay-size particles should be well noted

since saturated clayey materials will turn to have fit engineering properties at the beginning but

will eventually reduce in strength due to the removal of water from the pores. In dry seasons,

the ground water table reduces and the amount of water in the soil also reduced which implies

that the when investigations are done, they can be modelled and eventually used.

5.4 CONCLUSION: Water in rocks and soils can be of advantage or disadvantage on the engineering

properties/performance of the rocks and the soil masses.

17 | C O M P U T E R A P P L I C A T I O N S

6 CHAPTER SIX: ENGINEERING SIGNIFICANCE OF FOLDS AND

FAULTS:

6.1 FOLDS: A fold is a structure produced when an originally planar structure becomes bent or curved as a

result of deformation. Folds are an expression of a more ductile type of deformation that

produces gradual and more continuous changes in a rock layer, both in its attitude and

internally, as the rock accommodates to changes in shape. Below is typical diagram of a fold;

Figure 6-1: A TYPICAL DIAGRAM OF A FOLD.

18 | C O M P U T E R A P P L I C A T I O N S

6.2 FAULTS: A fault is a structure along which displacement has taken place. A fault plane can be vertical,

horizontal or at some angle in between whose orientation can be described by a strike and dip

measurement. If a fault plane (surface along which movement has taken place) is inclined to

the horizontal, the rock mass above it is the hanging wall and below it is the footwall. Below

is a typical diagram of a fault:

Figure 6-2:A DIAGRAM OF A FAULTING RESULTS.

6.3 ENGINEERING SIGNIFICANCE OF FOLDS AND FAULTS: They contribute to the permeability of rocks, which influences groundwater flow,

petroleum migration and accumulation.

They also allow the passage of hydrothermal fluids, some of which may carry valuable

metals and they serve as traps for mineral deposits.

Faults in particular can cause problems during constructions of deep-seated foundations

of sensitive infrastructures (plants of mines, tarmac) as they turn to weaken and creates

geological uncertainty in the design.

They also affect the total design of a project when encountered during excavations at

the site.

6.4 CONCLUSION: Folds are very important in petroleum engineering whilst geologist and mining engineers also

are very happy when they come across faults. But in civil engineering projects, faults poses

danger when they have come across them during excavation to foundations.

19 | C O M P U T E R A P P L I C A T I O N S

7 CHAPTER SEVEN: FOUR FACTORS THAT AFFECT THE

STRENGTH OF ROCK MATERIALS.

7.1 STRENGTH OF ROCK MATERIALS: The maximum stress a rock material can withstand at failure is its strength. The strength of a

particular rock type depends on some factors such as temperature, rock type, confining pressure

and time. These factors are briefly discussed in the following:

7.1.1 TEMPERATURE:

When temperature is high (deep in Earth's crust), rocks tend to deform ductilely and flow.

When this is low (at or near the surface) rocks tend to behave like brittle solids and

fractures. Temperatures also causes differential expansion and contractions in rocks, hence

causing ex-foliations. In tropical regions, where there is much sunshine and rainfall, it

speeds up weathering of the rocks. For instance, given the climate, basalt in the temperate

zones can be very strong due to the low sunshine whilst basalt in the tropics will weather

quickly as a results of the difference in climatic factors.

7.1.2 CONFINING PRESSURE:

Buried rocks are subjected to forces are applied equally in all directions. This "squeezes"

the materials in Earth's crust. Therefore, rocks that are deeply buried are "held together" by

the immense pressure and tend to flow rather than fracture. The strength of the rock is then

reduced.

7.1.3 ROCK TYPES:

Weak rocks that are most likely to behave in a ductile manner when subjected to different

stress, include rock salt, shale, schist, and limestone. Some rocks contain stable minerals

(quartz, feldspar) which are resistant to rock weathering whilst others contain unstable

minerals (pyroxene, olivine) which are less resistant to weathering. The strength of rocks

also depends on the arrangement of discontinuities in the rock.

7.1.4 TIME:

When forces are applied slowly over rocks for a longer span, rocks tend to display ductile

behavior and deform by flowing and folding.

7.2 CONCLUSION: All the factors that the strength of rocks are interrelated in the real situations. For instance,

when the rock type is made of weak/less resistant rock forming minerals, and is not subjected

to adverse weather conditions, the rock seems to be a stable one. On the contrary, this rock will

break down in no time, e.g. BASALT.

20 | C O M P U T E R A P P L I C A T I O N S

8 CHAPTER EIGHT: ENGINEERING PROBLEMS ENCOUNTERED

ON SOME SOIL DEPOSITS DURING CONTRUCTION:

8.1 GLACIAL DEPOSITS: A glacier, during its expansion, erodes the bottom and the sides of a valley, and when it retreats,

it leaves deposits of sediments called glacial drifts. Today glaciers cover about ten percent of

the Earth’s surface, but they were more extensive during the Pleistocene Epoch (which started

two million years ago). Their extension fluctuated several times and the last extensive one

occurred 20,000 to 15,000 years ago.

Melting of glaciers results in deposition of debris and creates a variety of landforms: bottom

moraines result from materials dropped directly from ice melting; lateral moraines originate

from debris eroded from valley sides, debris avalanches and rockfalls; medial moraines

originate when a tributary glacier merges with the main glacier; the arc-like ridge at the end of

glacier is called terminal moraine.

A common feature of moraine deposits is the spreaded grain size distribution curve. Since the

included materials range from cobbles to clays, these deposits are difficult to characterize in

terms of geotechnical properties.

Glacial lake deposits are usually composed of fine-grained materials and a relevant example is

represented by varved clays, alternating layers of grey inorganic silts and darker silty clays (of

a thickness less than 10 mm), transported I fresh water lakes by melt water. Usually the varve

consists of a lower part of coarsest particles deposited in summer and a finer-grained upper part

that sedimented in winter.

8.2 ALLUVIAL DEPOSITS: The Latin term alluvium was being used in antiquity to indicate the material left in place by a

river a flood event. For this reason alluvial deposits include detrital materials (gravel, sand, silt,

clay and mixtures of these) deposited permanently or in transit by flowing water. This

definition applies to deposits of streams in their channel as well as in the floodplain.

The alternating regime and the pattern of flow dictate the main features of these deposits: lateral

discontinuity and heterogeneity, presence of lenticular beds, of cross-bedded or evenly bedded

sands, silts and gravels and the spread of fine silts and clays across the floodplain.

Figure 8-1:ALLUVIAL DEPOSIT.

21 | C O M P U T E R A P P L I C A T I O N S

8.3 SWAMPY/PEATY DEPOSITS: Peat is an accumulation of partially decayed vegetation or organic matter that is unique to

natural areas called peatlands or mires. The peatland ecosystem is the most efficient carbon

sink on the planet because peatland plants capture the CO2 which is naturally released from

the peat maintaining an equilibrium. In natural peatlands the "annual rate of biomass production

is greater than the rate of decomposition" but it takes "thousands of years for peatlands to

develop the deposits of 1.5 to 2.3 m, although many other plants can contribute. Soils that

contain mostly peat are known as a histosol. Peat forms in wetland conditions, where flooding

obstructs flows of oxygen from the atmosphere, slowing rates of decomposition.

Landscapes covered in peat also have specific kinds of plants. Since organic matter

accumulates over thousands of years, peat deposits also provide records of past vegetation and

climates stored in plant remains, particularly pollen. Hence they allow humans to reconstruct

past environments and changes in human land use.

During constructions, swampy deposits have to be remove before foundations can be laid.

There is a lot of carbon dioxide gas inside peats which can react with the building materials to

reduce its efficiency. They increased the cost of the project through their removal from the site.

The design have to be change to suit the ground conditions.

8.4 CONCLUSION: In every construction, the location and climate determines the type of deposits that should be

expected and their problems to the project. Building in the temperate zones say Antarctica, the

type of deposit underlying the project should be glacier deposits. Building also in areas

susceptible to flooding, the deposit should be alluvial and a particular engineering design

should be use to suit the underlying soil.

22 | C O M P U T E R A P P L I C A T I O N S

REFERENCES:

1. Muckel, GB (editor) . Understanding Soil Risks and Hazards: Using Soil Survey to

Identify Areas With Risks and Hazards to Human Life and Property A report by the

United States Department of Agriculture, Natural Resources Conservation Service

and National Soil Survey Center, Lincoln, Nebraska (2004). Available online at:

ftp://ftp‐fc.sc.egov.usda.gov/NSSC/Soil_Risks/risk_low_res.pdf

2. Lawton EC, Fragaszy RJ, and Hetherington MD. "Review of Wetting-Induced

Collapse in Compacted Soil," Journal of Geotechnical Engineering, ASCE, 118-9

(1992) 1376-94.

3. Coduto, DP (2005) Foundation Design: Principles and Practices 2nd Ed. Prentice‐Hall (1999).