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SAFE CONSTRUCTION PRACTICES
Transformation of soil from a solid state to a liquid state as a consequence of increased pressure and differential settlement of footings is known as soil liquefaction.
The features to be considered at the stage of architectural planning and structural design of buildings for protection against earthquakes are:
. a) Building configuration
c) Control on openings in walls
d) Reinforced concrete bands in masonry buildings.
e) Vertical reinforcement.
Protection measures against floods are:
i) Residing on river banks and slopes on river banks should be avoided.
ii) Buildings should be built at 250 metres away from the sea coast/river banks.
iii) To build proper drainage system in all flood prone areas.
iv) To construct the whole village or settlement on a raised platform higher than the high flood level.
v) To construct the building with a plinth level higher than the known high flood level.
The measures adopted to control land degradation in different areas of our country are:
i) Soil erosion in hilly areas can be checked by construction of terraces for farming.
ii) Plugging of gullies by construction of check dams.
iii) A forestation can control soil erosion on slopes.
iv) In arid areas preparation of shelter belts of plants control over - grazing by animals and growing thorny bushes to stabilize the sand dunes.
v) In semi-arid areas, moistures conservation, weed control and proper management of waste land.
vi) Control of mining activities are some of the methods to curb land degradation.
. Industries cause water pollution by:
i) The industrial effluents that are discharged into rivers. They are both organic and inorganic.
ii) The principal industries which create water pollution are paper pulp, textiles, chemical, petroleum, tannery, etc.
The damaging effects of earthquakes on the ground are
i) Soil failures such as liquefaction and landslides caused by shaking.
ii) Tidal waves (Tsunami) i.e. large waves on the surface of water bodies, that can cause major damage to shoreline areas.
Two facts which should be borne in mind while selecting a site for a building in coastal areas are:
i) To build at least 250 metres away from the sea coast.
ii) Where houses can be built with a plinth level higher than the known high flood level.
Ground movements caused by earthquakes can have several types of damaging effect such as:
a) Soil failures such as liquefaction and landslides caused by shaking.
b) Tidal waves ( Tsunamis ) i.e. large waves on the surface of water bodies that can cause major damage to shoreline areas.
c) Surface fault ruptures such as cracks, vertical shifts, general settlement f an area, etc.
d) Ground shaking i.e., back and forth motion of the ground, caused by the passing vibratory waves through the ground.
The primary objective of earthquake resistant design is to prevent buildings from collapsing during earthquakes thus minimizing the risk of death or injury to people in or around those buildings. There are certain features, which if taken into consideration at the stage of architectural planning and structural improve their performance during earthquake.
The natural factors responsible for landslides are:
a) If slopes are steep.
b) If there is high intensity of rainfall.
c) If slopes have stiffness.
d) Soil layers formed under gravity.
e) Rock layers are highly weathered.
f) Poor drainage.
The man made factors responsible for landslides are:
a) Soil erosion caused due to deforestation.
b) Mining and quarrying.
c) Excavation which is non-engineered.
d) Construction which is non-engineered.
e) Land use pattern.
If buildings cannot withstand the forces of high winds and storm surge, than these buildings are considered vulnerable. Generally those most vulnerable to cyclones are lightweight structures with wooden frames, especially older buildings where wood has deteriorated and weakened the walls. Houses made of poorly constructed concrete blocks are also vulnerable.
Urban and rural communities on low inlands or in unprotected low-laying coastal areas or river floodplains are considered vulnerable to cyclones.
Man made factors responsible for causing landslides:
i) Soil erosion caused due to deforestation.
ii) Mining and quarrying
iii) Excavation which is non-engineered
iv) Construction which is non-engineered.
v) Land use pattern.
. The configuration of an earthquake – resistant building are:
a) Building should have a simple rectangular plan.
b) Long walls should be supported by Reinforced Concrete Columns.
Foundation of an earthquake-resistant building:
a) Assess the potential for soil liquefaction to avoid tilting cracking and failure of structure.
b) Adequate foundation design should be planned so that building can withstand earthquakes.
Vulnerable homes for landslides are those which are situated on:
a) Below hills with outcrops of fractured rock.
b) Steep natural slopes, particularly on weak geologic materials.
c) Developed hillsides where septic – tank, soil absorption systems are used and land-scapes are irrigated.
d) Steep construction-related cut or fill slopes.
e) Areas in or at the mouths of drainages such as canyons.
f) Existing landslides area.
Most vulnerable homes for floods are:
a) If biomas materials like bamboo, leaves, thatch are used to construct huts then they are easily destroyed in floods and washed away.
b) Buildings which are constructed with earth-based material or using stone and brick in mud mortar.
c) Flood plains attract poor urban dwellers because of inexpensive land values.
d) Occupation of areas within the flood plains of rivers especially in areas of high population has increased the vulnerability.
The Effect on buildings due to floods are:
a) Water under high stream velocity washes away the houses.
b) Rising waters may cause in flotation of houses from their foundations.
c) Even though houses remain intact on their foundation, floods may cause severe damage to materials.
d) Velocity of water may erode th foundation of the house which may result in the collapse of the house.
e) Massive floating objects like trees, electric poles, etc., may effect the standing houses and cause significant damage.
f) Other forms of damage are wall erosion, cracks and bulging damage to water supply, sanitation and electrical systems.
Protection measures against floods are:
a) Residing on river banks and slopes on river banks should be avoided.
b) Buildings should be built at 250 meters away from the sea coast/river banks.
c) To build proper drainage systems in all flood prone area.
d) To construct the whole village or settlement on a raised platform higher than the high flood level.
e) To construct the building with a plinth level higher than the known high flood level.
The effects of cyclones on buildings are:
i) Punching and blowing off of corrugated iron roofing sheets attached to steel trusses.
ii) Brittle failure of asbestos – cement sheeting of the roofs of industrial sheds; failure of these sheets is generally ridges and gable ends.
iii) Failure of large industrial buildings with light weight roof coverings and long/tall walls due to combination of internal and external pressures.
iv) Failure of roofing elements and walls along the gable ends particularly due to high internal pressures.
v) Overturning failures of compound walls of various types.
vi) Failures of improperly attached or constructed parapets.
vii) Damage to roof/lintel projections.
viii) Damage to improperly attached windows or window frames.
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