IMPACT OF GRANITE QUARRY ON THE ENVIRONMENT: A CASESTUDY OF IYUKU COMMUNITY, EDO STATE, NIGERIA

BY

Bldr. M. O. OBOIRIENoboirienmomoh@yahoo.com08064326749, 08052273676

DEPARTMENT OF BUILDING TECHNOLOGYAUCHI POLYTECHNIC, AUCHI

EDO STATE

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ABSTRACT

Quarrying in reasonable volumes for construction canhardly be achieved by manual labour hence the use ofexplosives. In the operations, the entire environmentis subjected to vibrations, employment is created,and royalties paid to the community. The consequencesof granite quarrying to IYUKU community located atthe outskirts of Auchi, Edo state were investigatedby physical inspection of property in the area,interviews with the community leaders, managers ofthe quarry sites and some members of the communitypicked randomly. The investigation showed thatvibrations and impact sounds from the quarryoperation are major causes of building failures.Moreover the intermittent inter family clashes thathad always resulted to loss of lives and propertieswere consequences of dissatisfactions from in thesharing of royalties paid by the quarry firms. Someof the recommendations made include the reduction offoundation soil system vibration frequency to newbuildings by the installation of damping mounts andaltering one or more of the factors, which reduce thenatural frequency of foundation soils. Others areexcavating trenches along the perimeter a minimumdistance of 1000mm away from foundation of exitingbuildings. Assessment of environmental impact ofdevelopment projects or the material extractionoperations on communities is also advocated forconsideration in Nigeria.

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INTRODUCTION

Coarse aggregate a major constituent of concrete

used in the construction of structural elements of

building has become difficult if not totally

unavailable in natural deposits as gravel. This

informed breaking of rocks into smaller sizes to

obtain aggregates.

Modern and complex buildings require concrete as

common material in the construction of structural

members. The concrete is composed mainly of three

materials – cement, water and aggregates.

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Coarse and fine aggregates constitute between 60

– 75 percent of hardened concrete, Jackson (1977).

Aggregate is much cheaper than cement and maximum

economy is obtain by its use in concrete. It

improves considerably the volume stability and

durability of the resulting concrete. The properties

of aggregates known to have a significant effect on

concrete behaviour are its strength, deformation,

durability, toughness, hardness, volume change,

porosity, specific gravity and chemical reactivity.

In the past, natural aggregates were mainly

obtained by extraction from deposits formed by

alluvial or glacial action. Current demands for

aggregate make such natural deposits insufficient and

expensive leading to the crushing of blasted rocks to

the required particle sizes.

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QUARRY OPERATIONS

Iyuku is naturally endowed with rock deposits

attracting granite quarry investors. About five of

such investors have their sites in Iyuku, a

community, at the outskirt of Auchi Township. The

firms do surface and underground quarrying due to

depth of the rock. Mechanical excavator, handpicking

and cranes remove the overburden, which varies from a

few feet to 15m thick. Blasting loosens the top and

skill caps.

Blasting is sometimes needed in sand stone

quarries because of the hardness. A series of deep

holes about 25mm in diameter are formed with drilling

machines at the required distance from and parallel

to the face of the quarry. A small charge of

gunpowder and a fuse are placed or tamped with sand.

The fuses are connected to a battery and the charges

fired. The explosion shakes the rock mass especially

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with subsequent charge and firings. The bulky and

large stone, which are only slightly shattered

because of few numbers of blasts, are transported to

the grinding mills for reduction into smaller

diameter aggregates. Vibrations of the underlying

rock mass spread through the whole community from the

companies’ weekly operations. According to Mickay

(1975) such explosions create damaging vibration

waves to buildings. Buildings are shaken from

foundation to roofs, domestic animals run from hills

to valleys, job opportunities are created for young

men and women in the grinding mills. Royalties and

compensations paid by the quarry firms to community

leaders who are accused by younger generations for

selling cheaply the entire community’s property to

crafty business concerns.

In UNICED (1992), Momoh and Agbanure (2005) noted

that effects of development projects like roads,

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housing and other infrastructure on our physical

environment and human well being, is attracting

serious attention throughout the world. The impact of

granite quarrying on Iyuku’s physical and socio-

economic environment is yet to be addressed. This

paper therefore aims at investigating the extent to

which granite quarrying has influenced the socio-

economic, as well as cultural life of the people with

a view to proffering solutions to the negative

consequences of granite mining on Iyuku and its

environs.

METHODOLOGY

The work was pursued through inspection of

properties in the community with a view to

ascertaining the nature and extent of building

damages. Interviews with some members of the

community leaders and employees of the quarry firms.

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Pictures of failing buildings were taken for

examinations, management of the quarry firms was not

left out in interviews. Conclusions were drawn on the

basis of the analysis data gathered from the field

followed with appropriate recommendations.

THEORETICAL OVERVIEW

Behaviour of Incident Sound

Vibrations set up in air cause a transfer of

mechanical energy away from the source. The energy

travels in the air gradually being dissipated in a

way similar to that of heat energy and finally the

vibrations die away completely.

When sound waves are incident on a surface, which

is large, compared with the wavelength of the sound,

the energy is reflected, absorbed or transmitted. It

may be absorbed into air spaces within the building

element causing them to vibrate, (Edwin and Selwyn

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1976). Generally the three occur but the proportion

of occurrence depends on the nature both of the sound

and of the medium, which in this case is block wall,

brick wall or concrete wall and floor. The sound

incident on a plane surface is reflected with an

angle of reflection equal to the angle of incidence.

Whereas a convex surface focuses the sound, a concave

surface cause divergence. Sound is diffused by small

surface irregularities. Reflection is greatest when

the surface is hard and the partition has a high

superficial weight.

FOUNDATIONS SUBJECT TO VIBRATION

Vibrations from blasting explosion are one of the

external stresses on foundation of buildings.

Continuous vibration usually has a constant frequency

determined by the source but complicated by harmonics

generated by the structure. Transient vibrations from

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shocks may have a variable frequency depending on

both the source and it’s supporting system.

Sound waves are transmitted in different

directions (see Figure la) vertical, longitudinal and

transverse linear motion (equivalent to an orthogonal

co-ordinate system).

Figure 1a: Modes of Vibration of Machine Foundation

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Figure 1b: Simple Elastic System in Linear (Vertical)

Vibration

Figure 1c: Simplified representation of the

vibrating components of a soil-structure system. And

in three directions of rotation, rocking, pitching

and slewing depending on the source of the vibration

and freedom to move.

MECHANISM OF VIBRATIONS

If an impulse of short duration is applied to a

body that is supported elastically it vibrates at its

natural frequency, which depends on its mass and

elastic properties. For a perfectly elastic body (see

Figure 1b) whose weight is W and whose resistance to

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deflection in force per unit deflection (KN/m) is K,

the natural frequency fn as given by Sewers (1979) is:

When energy is lost in the process the vibration

is said to be damped and the natural frequency is

somewhat less. The damping is described in terms of

damping ratio c, which is an indication of the amount

of vibration energy lost in each cycle c = 0 denotes

no loss, c = 1 indicates all the impulse energy is

dissipated in one cycle of vibration.

The complex natural frequency of a foundation

soil system is shown in Figure 1c. the resistance per

unit of deflection K can be estimated from the

distorted settlement e. this depends on both the

modulus of elasticity of the soil and size of the

foundation. The weight of the vibrating body W, is

the sum of the weight of the foundation. Wf and the

portion of the soil mass below the foundation, which

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is vibrating Ws. Therefore the natural frequency of

the soil depends on the weight and size of the

foundation and the load it carries.

The intensity of the vibration is also a factor

because the modulus of elasticity of most soils

changes with confining pressure and with the strain.

Sewers (1979) puts it that tests of soil masses with

vibrators having masses from 10 to 30KN and with

square bases from 0.6 to 1.0m wide indicate natural

frequencies of from 12Hz to 30Hz for very dense sand.

For heavier and wider foundations the natural

frequency is less.

EFFECTS OF VIBRATION ON FOUNDATION SOIL SYSTEM

Sewers (1979) stated the effect of soil vibrations

as:

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i. Transmission of the vibrations from one

foundation to another and to other structures

at some distance from the source.

ii. Reduction in the void ratio (e = Vv/Vs) of

cohesion less soils and result in severe

settlement. Ordinarily the settlement will be

small if the relative density is greater than

60 percent but if the vibration is severe,

settlements occur until the relative density is

nearly 80 percent.

iii.Vibration in loose saturated cohesionless soil,

brings about liquefaction and failure. Soils

with cohesion are resistant to vibration

settlement and are not weakened appreciably.

The transmitted vibrations can be annoying and

even damaging. If a foundation soil system

should be in resonance and amplification,

severe damage could result.

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FOUNDATION SETTLEMENTS RESULTING FROM MINERALEXTRACTION

Ground subsidence often results from the

extraction of minerals. A combination of horizontal

movements at the surface coupled with vertical

movements can cause serious damages to buildings.

Seeley (1985) opined that an extracted coal seam

1.30m thick could cause subsidence at the surface of

up to 1m deep immediately above the seam and reducing

on both sides.

A subsidence wave may first cause tension in

building at the crest, followed by compression in the

trough. The worst effects are with thick seams in

shallow workings. Tensile stresses cause lengthening

of structures with fractures in walling at butt

joints and at corners of window and door openings,

followed by the fracture of pipe joints and

displacement of beams. Comprehensive stresses may

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result in buckling of walls and the arching of pipe

and paving materials.

DAMAGES TO SUPERSTRUCTURES DUE TO VIBRATION

Seeley (1985) observed that machinery and

transport developments are increasing vibration and

noise to an extent that they become objectionable to

people and interfere with normal home activities. He

further expressed fears that buildings may be damaged

by vibration, although investigations by Building

Research Establishment show that risk of damage to

normal buildings was small not withstanding the level

of vibration. Many factors need to be taken into

consideration when assessing the possibility of

damage to buildings –additional stresses set up by

the vibration, the size and type of building, the

fatigue properties of the construction materials and

the possibility of resonance. Cracks in plastered

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brickwork and glass may not be attributed to the

effects of vibration until other possible causes have

been eliminated. For instance most cracks in

plastered ceilings result from movement of the

plaster itself or the supports due to changes in

moisture content, and this frequency occurs in areas

known to be free from external sources of vibration.

METHOD OF COMBATING VIBRATION EFFECTS ON BUILDINGS

Vibrations or impacts unlike airborne noise are

communicated directly to the structure. The only

defense is to prevent the transmission of the impact

to the structure. Harrison (1978) recommended the use

of soft hard floor insulation finish, placed in one

of the following three ways.

Soft: Thick carpet of sheet floor coverings on under

layer of sponge rubber, hair felt or fiberboard, cork

tiles not less than 8mm thick.

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Medium: A moderate insulation; consisting of thin

carpet or matting, thick linoleum or rubber on solid

floor

Hard: Granolithic and jointless floors: of clay,

concrete or thermoplastic tiles, stone, asphalt and

thin linoleum.

The above insulation methods are classified; as

good, moderate and poor; for the first, second and

third respectively. Harrison further stressed that

each could alternatively be accomplished with a

resilient layer. This layer not highly compressed

within the floor construction is called floating

layer illustrated in the following Figure 2.

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FIGURE 2: FLOATING FLOORS ON CONCRETE

The insulating materials are made in special

forms for this purpose with compressed thickness of

the layer less than 15mm. Apart from not readily

available in Nigeria, their construction and use

require high technical expertise, success depends

upon ensuring that no rigid connection exist between

the floating screed or raft to the structure. These

are difficult to achieve at floor edges as a result

of concrete from a screed leaking through the

resilient layer or from the foundation of bridges or

by pipes conduits or other services. Difficulties

caused by drying shrinkage may occur when floating

concrete screeds are laid in rooms larger than about

18m2. Moreover partitions are built off the structural

slab confining the floating floors within individual

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rooms. The achievement of this consumes more time in

planning and consideration.

THE BUILT ENVIRONMENT SUSTAINABILITY

Sustainable development projects are required to

satisfy technical, economic, social and environmental

concerns and considerations now and in future,

(Mahgoub 1997). Invariably sustainable built

environment is about the raw materials acquisition

for development, building, engineering construction

and maintenance, that continuously meet the needs of

every person in the community (immediate and remote)

now and for future generations without negative

technical economic, social and environmental effects.

If granite quarry at Iyuku for sale to

construction firms in Benin, Warri, Sapele, Agbor and

Port-Harcourt results in the disturbance of life and

damages to surrounding buildings, definitely some

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question of sustainability would be raised. This will

be, not only for keeping the construction business

but for building property, which are supposed to live

a reasonable span of life.

FIELD SURVEY AND RESULTS

Iyuku is located North of Auchi town and

administration by Etsako Central Local Government

Council with Headquarters at Fugar. Iyuku is close to

Jattu (a market town in Etsako Local Government Area)

in terms of population and landmass. It has a rocky

terrain, the people’s main occupation is agriculture;

corn, yam, cassava and leguminous crops being the

major products.

A number of construction companies are attracted

to the community due to the abundance of rocks in the

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area. One of the firms have been in operation for the

past twenty five (25) years, three have operated for

an average of four (4) years while many new ones are

still at the verge of commencing operations, see

Table 1.0.

Table 1.0: Age of Quarry Firms in the Community

Firm Years of operation as

at 2005

Ownership

1 25 Foreign

2 5 Foreign

3 4 Foreign

4 3 Foreign

5 2 Foreign

6 3 Foreign

7 3 Foreign

Table 2.0: Nearness of Quarry Site to Houses and Blasting

Frequencies

Firm Distance from homes Blessing22

(km) Numbers/week

1 3 7 – 10

2 3 Information not

available

3 5 10

4 2 Information not

available

5 5 Ditto

6 4 Ditto

7 2 6 – 10

BUILDING TYPES AND FAILURES

Like in any other traditional settlements,

buildings in Iyuku are mainly of mud constructions in

one to two storeys. A number of modern constructions

in cement and sand blocks with reinforced concrete

beams, columns and slabs are now being built in the

community. Apart from a few buildings that have23

isolated pad foundations, most were constructed of

mass concrete strip foundations because of good

bearing capacity of the natural foundation.

The community is divided into four major quarters

– Iyouwu, Iyakhala, Ubenor and Olele. Many of the

buildings show signs of failure in the form of cracks

tilting and collapsed walls. Failure modes and

distances of buildings to any of the quarry sites

group in traditional and modern constructions are

tabulated in Table 3.0. Over eighty (80) percent of

indigenes interviewed agreed that vibrations from

rock blasting explosives causes the enormous cracks

and other damages to the buildings in the community.

Table 3.0: Failure Symptoms in Buildings

FAILURES

SYMPTOMS

TRADITIONAL MUD BUILDINGS MODERN CONSTRUCTION IN

CEMENT AND SAND BLOCKS

EXPERTS’ OPINION ON POSSIBLE

CAUSE OF FAILURE

No of

Buildin

g

Approximate

distance (6m)

from houses

No of

Buildin

g

Approximate

distance (6m) from

house

Due to

vibration

from rock

blasting

Normal modes

of

Deterioration

Vertical

Cracks

50 2 40 2 60% 40

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Tilting

Buildings

Fallen Walls

Sinking

Foundations

10

10

20

3

2

2

13

15

30

3

2

2

90%

80%

100

10

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SOCIO-CULTURAL EFFECTS OF BLASTING

The quarry firms had, part from paying royalty to

the community and other statutory charges to the

Local Government Council, donated a few projects to

the community.

Project donations although classified as

developmental assistance, they more or less serve as

reparations for damages caused the community,

especially to building structures. These are self –

charged penalties for payments due to damages

suffered by the community in their buildings.

Children of school age, male and female who are

exposed to money earning as a result of employment in

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the quarries abandon schools and colleges for money

making. Teenage girls eventually go into early

marriages, worst still are births by single parents

whose immoral partners refuse ownership of

pregnancies. These are direct consequences of upsurge

in population brought about by quarry activities.

Moreover, seventy (70) percent of the respondents

claimed that major causes of the age-long inter

family conflicts in the community are not unconnected

to differences and arguments in sharing the royalties

paid by quarry firms. Unquantifiable lives and

property had been lost in the conflicts. However

quarry business apart from attracting developmental

assistance, create employment first and foremost to

the indigenes. The number of Iyuku indigenes employed

in the currently operating firms is shown in Table

4.0. Quarry activities have not only created

employment for labourers, technicians and managers

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but also for self employed entrepreneurs like food

vendors, who are Iyuku indigenes, as well as

suppliers of consumables to the firms. Demand for

rental accommodations have also risen in the past few

years.

Table 4.0: Employment Creation by Granite Quarry

Operations

CategoryofEmployment

Company

(1) (2

)

(3) (4) (5) (6) (7)

Security

men

10 20 Informati

on not

available

7 6 9 8

27

Labourers 35 38 Ditto 30 Informat

ion no

availabl

e

28 10

Technician

s

15 14 Ditto 5 Ditto 10 3

Managers 4 Ditto 3 Ditto 2

CONCLUSIONS

Granite quarry has affected the lives of Iyuku

indigenes, employment has been created for young men

and women (see Table 4.0). The companies had

participated in community development by donating

infrastructures like transformers, roads and drainage

system. Moreover the royalties paid to the community

has complimented the Federal Government programme of

POVERTY ALLEVIATION in rural communities.

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Not withstanding the contributions to positive

development a second thought needs to be given to the

environmental impact of quarry activities especially

to the built environment. Other dimensions of the

impact such as health which do not form part of the

focus of the study cannot however be ignored.

As cities grow in size annually, houses would in

the near future be very close to these sites making

the effect unbearable. Negative socio-cultural

effects should also not be undermined, they could

outweigh the economic benefits from these activities.

As the construction industry is being sustained, the

demand for materials like granite is on the increase.

The extraction from quarry is creating negative

social, technical, economic and environmental impacts

on IYUKU, especially on the buildings.

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RECOMMENDATIONS

(a) Design Precautions

i.Reducing the resonance frequency by altering one

or more of the factors in the equation: fn =

. Increasing the size and weight of the

foundation reduces the resonant frequency of the

system.

ii. Cumulative effects of impact sounds should be

reduced by ensuring at design stage, that out-

buildings (canopies, sheds, shop front etc) are

ideally independent of the main structures and

projecting bay porches and the likes are best

avoided. Also breaks in longitudinal; buildings

should extend through the foundations.

iii. Paved surfaces should be of flexible

materials such as tarmacadam and asphalt to

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absorb the impact sounds and vibrations without

resulting to crack in walls.

iv. Door openings, which constitute points of

weakness, should be located in short walls,

avoiding; front and back doors opposite one

another, and doors in adjoining dwellings from

being placed side by side.

v.Isolation system; Vibration can be reduced by

installing damped spring mounts thereby

cushioning the buildings on vibration – absorbing

materials.

The floor rests on resilient mountings

supported on the main building structure. It

carries the walls and ceilings which do not have

any sort of rigid connection with the main

structure (see Figure 2.0) while pipes and ducts

are led in through flexible connections.

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Figure 2.0: An Isolated Unit Providing Resilience for

the Building

(b) Construction Guides for Reducing Damages Due to

Vibration

i. Provision for movements using flexible pipes

and flexible joints. Where pipes pass through

structures, pin-joints should be used

especially in steel frameworks. All cladding

units should be free to slide against

adjoining units.

ii. Excavating trenches along the perimeter of

the building prevents vibration frequencies

from reaching the building. The trenches

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should be at least 1000mm away from the

foundation, they are particularly effective

with small buildings.

(c) Environmental Impact Tax Fund

Apart from enforcing the law on environmental

impact assessment for project in line with the

1992 decree, corporate firms with manufacturing

and mining concerns should be made to pay

environmental impact tax. Such monies tagged

“Environmental Tax Fund” are to be used in

assisting communities that may suffer degradation

from industrial operations.

Similar organs in the state should compliment

the responsibilities of the Federal Ministry of

Environment. There is therefore a need for the

creation of State Ministries of Environment in

Nigeria.

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REFERENCES

Edwin, W and Selwyn, M (1976): Construction Science.Hutchinson & Co. Ltd. London, Pp 228-297

Harrizon, D. (1978): Edited, SPECIFICATION Building Methodsand Products. The Architectural Press, Vol I,London, Pp 131-132

Jackson, N (1977): edited Civil Engineering Materials, ELBSedition, The Macmillan Press Ltd. Pp 110-126

Mahgonb, Y. (1997): “Sustainable Architecture in theUnited Arab Emirates: Past and Present”. Inproceedings of the CAA-IIA InternationalConference on Urbanization and Housing 2nd – 5th

October, 1997, GOA, India

Mckay, W. B. (1975): Building Construction Volume One,Metric 5th Edition, The English Language Book Societyand Longman, London, Pp 35-36.

Momoh, L. R. & Agbanure, F. E (2005): “The impact ofAsphalt Production on the Environment. The casestudy of Agbaraotor, Delta State, Nigeria” TheBuilt Environment Journal, Faculty ofEnvironmental Studies, Ambrose Alli University,Ekpoma Vol. 1 No. 1 Pp. 69-77

Seeley, I. H. (1985): Building Maintenance, MacmillanPublishers Ltd, London Pp 27-30 & 39

Sewers G. F. (1979): Introductory Soil Mechanics andFoundations: Geotechnical Engineering, 4th Edition,Macmillan Publisher Co. Inc. New York, Pp. 492-495.

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