Designing Buildings - User contributions [en]

Polders

2012-12-12T19:24:36Z

Ajmal: Protected "Benefits of Polders and Consolidation - Geotechnology" ([edit=author] (indefinite) [move=author] (indefinite))

<div align="center">
{| width="100%" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%; height: 192px;" |
Teesside university

|}

Assignment 1 – Polders and Consolidation

Geotechnology

Ajmal Hussain

K0080508
</div>
{| width="100%" align="left" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%;" |
In this report I will discuss what polders are, why they are used extensively in the Netherlands, how they can be constructed and maintained. The effects that they may have on structures and an outline of the geotechnical conditions which makes them popular in the Netherlands and their related consolidation.

|
|}

<br/>

'''Contents '''

Introduction........................................................................................................... (2)

What are polders………………………………………………………....................... (2)

Consolidation ………………………………..………………………......................... (3)

Why the technique is used……………………………………………...................... (3)

Geotechnical Conditions……………………………………………………………… (4)

How polders are maintained……………………………………………………… (5)

Construction of polders…………………………………………………………… (5)

References…………………………………………………………………………… (6)

'''Introduction '''

Polders are considered to be low lying land which consists of physical barriers, these are known as dikes.

Polders are commonly used in the Netherlands as floods are of high risk to the land; this is due to land being beneath the mean sea level. To prevent this, dikes and protective embankments (barriers) had been built to stop water from flooding the Netherlands. The benefit of using a polder system is that it can aid in flood reduction.

'''What are polders?'''

A polder is basically an area which is surrounded by dikes where groundwater level is artificially controlled; usually this is done by a berm or a dike, in other words groundwater levels are maintained by a drainage system. This involves drainage systems such as ditches and canals which deliver water to the perimeter of the polder. Polders can be laid near a river or sea for easier drainage. It consists of artificial land barriers called dikes. Dikes are walls whose main function is to protect polders and to stop water from flowing to them. The dikes are used as a barrier between the reclaimed land and the sea. Marshes and canals can be formed using dikes. This is due to water seepage under the wall of the dike.

When dikes are constructed next to rivers, the land is below the sea level. In this case there are two boundary dikes which are used to protect polders from varying sea level changes throughout the year. The front dike is called a summer dike and the back dike is called the winter dike. In the winter the summer dike is below sea level, during summer the summer dike spreads to the surrounding land.

The diagram shows the areas with traditional polders (red dotted circle) and the area with modern highlighted in yellow.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Dutch Polder systems 2010, page 2)''
</div>
|}

<br/>

'''Consolidation '''

Consolidation in soil mechanics is the compression of soils. By compressing the soils it reduces the water content making the soil denser. This is consolidation of soils. Consolidation occurs when the ground weakens due to an increased stress load on the soil. As a result the soil reduces in volume.

When a soil reduces in volume and consolidates this can affect the structures that are built on top. When a soil consolidates forces in the soil are reduced. As soils are loaded with greater forces, the structure will break down depending on the type of soil. The increasing effect of stress and water can change the ground conditions and lead to consolidation. Peat and clay tend to consolidate, this results in land subsidence and cracking.

Due to the high water content in the soils, consolidation is likely to occur when building upon the land. This can lead to the ground sinking through the applied loads of the structures. The main reasons for consoildation occuring is shrinkage and soil consolidation. As groundwater is reduced the buoyancy forces in the soil decrease therefore an increase in the total effective stress of the soil takes place. To minimise consolidation settlement, you would need to consider the amount the ground will settle and the rate at which settlement will occur with a specific applied load placed upon it.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
Figure 1
</div>
|}

Figure 1 shows the different water level content in fine grained soils. The level of permeability in fine grained soils is low meaning the consolidation process can take a long time. When building on top of fine grained soils, a higher water content is not desired as consolidation settlement can occur over time. The rate of consolidation will depend on soil nature, degree of saturation and load applied.

''(''[http://kshitija.wordpress.com/ http://kshitija.wordpress.com]'')''

'''Why the technique is used? '''

The technique of empoldering is well known in the Netherlands. Polders are reclaimed from land that has been submerged by the sea, they are used to prevent rising water pressures and floods. The technique is important particularly in the Netherlands as land is susceptible to high risk of floods. The sea levels in and around the area are much higher than the land meaning that most of the Netherlands is submerged below sea level.

Dikes can be used to build a barrier to stop the flow of water reaching land. This helps to make sure that water does not affect the ground. Water can seep into soil and affect the characteristics of the soils. Such characteristics may be the colour, shape, strength and cohesion.

Properties such as soil porosity, effective stress, pore water pressure; density of soils needs to be considered.

'''Geotechnical conditions'''

Ground conditions can have an effect on what types of structures are built. Soil types must first be identified to determine the ground structure. The geotechnical conditions in the Netherlands are comprised of clays. This is more common near river deposits. Other types of soils commonly present in areas of the Netherlands are sandy clays, peaty layers and mineral soils. In coastal areas, groundwater is saline this is because of sea water intrusion. (Struyfuz and Stuurman, 1994).

Case studies on water balances on polders were carried out. The studies had found that the seepage occurred through clay and peat with low permeability. Studies later found that groundwater seepage could occur through pathways. (Becker et al., 2004, Kalbus et al., 2009). Below is a diagram outlining the location of deep polders (reclaimed lake areas) in the Netherlands showing monitoring points and main ditches.

'''(Fig 3) '''

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Designed for dry fleet: Land reclamation in the Netherlands, page 7)''
</div>
|}

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Journal of Hydrology, page 495)''
</div>
|}

<br/>

'''(Fig 2) '''

Fig 3 shows the soils of the Netherlands. The lower elevations near the north and west shows soils such as peat, marine clay and river clay. Groundwater flow called boils has been taken into account in polders. These boils act like vents which develop when the pressure of water is high.

Water which comes into contact with land can subside over a period of time; as a result water can enter the polder through increasing water pressures.

'''How polders were maintained'''

The polders were maintained by usage of windmills, the benefits of this were to pump out excess water. These were used in the Netherlands as a means to drain the land. Pumping stations can be also used to drain water.

The wind mills help to maintain water levels. The water is controlled through drainage schemes which are usually canals. Furthermore, water is released from the polder by using a pump. The pump is needed in case water levels are higher than the water inside the polder.

These pumps can be powered by electricity or through the use of windmills for drainage of excess water.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
(''Designed for dry fleet:''

''Land reclamation in Netherlands) page 2''
</div>
|}

<br/>

'''Construction of Polders'''

Polders are generally constructed to reclaim land and protect against water. The construction of polders is done by forming dikes around the surrounding land area. The process for constructing a polder is to first remove soils which are unstable. A layer of sand fill is positioned. Two strips of boulder clay are laid; this creates the abutments of the dike. A larger strip is positioned on the side facing the sea and a smaller strip is placed upon the polder side. Spaces between the foundations are filled with asphalt; riprap and sand basalt revetments are placed.

On the whole, polders have aided the population of the Netherlands by giving more land to the public. The land can be used for agricultural purposes such as maintaining crops. I believe that the use of polders has had a positive effect for the future, especially as sea levels continue to rise in the current climate.

'''References'''

= Works Cited =

Upward Groundwater Flow and salinization in Deep Polders. (2009). ''Journal of Hydrology'', 494-507.

''A Brief History of Dutch Dikes and Polders ''. (2011, October thursday). Retrieved from [http://www.metropolismag.com/pov/20100216/a-brief-history-of-dutch-dikes-and-polders http://www.metropolismag.com/pov/20100216/a-brief-history-of-dutch-dikes-and-polders]

''Dutch Polder System 2010.'' (2011, October Tuesday). Retrieved from [http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf]

''The Polders in Netherlands ''. (2011, November Saturday). Retrieved from [http://www.docstoc.com/docs/622752/The-polders-in-the-Netherlands http://www.docstoc.com/docs/622752/The-polders-in-the-Netherlands]

''Chapter 2 Soil and Water''. (n.d.). Retrieved November Tuesday, 2011, from [http://www.fao.org/docrep/R4082E/r4082e03.htm http://www.fao.org/docrep/R4082E/r4082e03.htm]

''eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf.'' (n.d.). Retrieved October Tuesday, 2011, from Soil Remedation in the Netherlands : eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf

''Geotechnology 101''. (n.d.). Retrieved November Tuesday, 2011, from [http://kshitija.wordpress.com/ http://kshitija.wordpress.com/]

Hoeksema, R. (05/2006). Designed for dry fleet: Flood Protection and Land Reclamation in the Netherlands . 1-4.

''Impact of Water Management ''. (n.d.). Retrieved November Monday, 2011, from Levees And Polders : [http://www.cbd.int/programmes/areas/water/toolkit/html/1.13.4_%20levees%20_%20polders.html http://www.cbd.int/programmes/areas/water/toolkit/html/1.13.4_%20levees%20_%20polders.html]

Smith, I. (2006). ''Smith's Elements of Soil Mechanics .'' Blackwell Publishing .

''Soil Testing .'' (n.d.). Retrieved November Monday, 2011, from [http://www.geotechnique.info/SI/SI%20Book%20Chapter%208.pdf http://www.geotechnique.info/SI/SI%20Book%20Chapter%208.pdf]

''The remarkable history of polder systems in the netherlands .'' (n.d.). Retrieved Ocotober Tuesday, 2011, from [http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf]

[[Category:Student_engineer_essay_competition]]

Polders

2012-12-12T19:24:19Z

Ajmal:

User:Ajmal

2012-12-12T19:22:43Z

Ajmal: Created page with " your page about me’ must include your full name, email address, place of study and course (or details of the qualification you received in 2012). Log in. As long as you’re l..."

your page about me’ must include your full name, email address, place of study and course (or details of the qualification you received in 2012).
Log in. As long as you’re logged in, your user name will be recorded in your article history so we will know who wrote it.

Name: Ajmal Hussain
Email Address: ajmal-hussain2000@live.co.uk
Place of Study: Teesside University
Course: Beng Civil Engineering

Polders

2012-12-12T18:30:23Z

Ajmal:

<div align="center">
{| width="100%" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%; height: 192px;" |
Teesside university

|}

Assignment 1 – Polders and Consolidation

Geotechnology
</div>
{| width="100%" align="left" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%;" |
In this report I will discuss what polders are, why they are used extensively in the Netherlands, how they can be constructed and maintained. The effects that they may have on structures and an outline of the geotechnical conditions which makes them popular in the Netherlands and their related consolidation.

|
|}

<br/>

'''Contents '''

Introduction........................................................................................................... (2)

What are polders………………………………………………………....................... (2)

Consolidation ………………………………..………………………......................... (3)

Why the technique is used……………………………………………...................... (3)

Geotechnical Conditions……………………………………………………………… (4)

How polders are maintained……………………………………………………… (5)

Construction of polders…………………………………………………………… (5)

References…………………………………………………………………………… (6)

'''Introduction '''

Polders are considered to be low lying land which consists of physical barriers, these are known as dikes.

Polders are commonly used in the Netherlands as floods are of high risk to the land; this is due to land being beneath the mean sea level. To prevent this, dikes and protective embankments (barriers) had been built to stop water from flooding the Netherlands. The benefit of using a polder system is that it can aid in flood reduction.

'''What are polders?'''

A polder is basically an area which is surrounded by dikes where groundwater level is artificially controlled; usually this is done by a berm or a dike, in other words groundwater levels are maintained by a drainage system. This involves drainage systems such as ditches and canals which deliver water to the perimeter of the polder. Polders can be laid near a river or sea for easier drainage. It consists of artificial land barriers called dikes. Dikes are walls whose main function is to protect polders and to stop water from flowing to them. The dikes are used as a barrier between the reclaimed land and the sea. Marshes and canals can be formed using dikes. This is due to water seepage under the wall of the dike.

When dikes are constructed next to rivers, the land is below the sea level. In this case there are two boundary dikes which are used to protect polders from varying sea level changes throughout the year. The front dike is called a summer dike and the back dike is called the winter dike. In the winter the summer dike is below sea level, during summer the summer dike spreads to the surrounding land.

The diagram shows the areas with traditional polders (red dotted circle) and the area with modern highlighted in yellow.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Dutch Polder systems 2010, page 2)''
</div>
|}

<br/>

'''Consolidation '''

Consolidation in soil mechanics is the compression of soils. By compressing the soils it reduces the water content making the soil denser. This is consolidation of soils. Consolidation occurs when the ground weakens due to an increased stress load on the soil. As a result the soil reduces in volume.

When a soil reduces in volume and consolidates this can affect the structures that are built on top. When a soil consolidates forces in the soil are reduced. As soils are loaded with greater forces, the structure will break down depending on the type of soil. The increasing effect of stress and water can change the ground conditions and lead to consolidation. Peat and clay tend to consolidate, this results in land subsidence and cracking.

Due to the high water content in the soils, consolidation is likely to occur when building upon the land. This can lead to the ground sinking through the applied loads of the structures. The main reasons for consoildation occuring is shrinkage and soil consolidation. As groundwater is reduced the buoyancy forces in the soil decrease therefore an increase in the total effective stress of the soil takes place. To minimise consolidation settlement, you would need to consider the amount the ground will settle and the rate at which settlement will occur with a specific applied load placed upon it.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
Figure 1
</div>
|}

Figure 1 shows the different water level content in fine grained soils. The level of permeability in fine grained soils is low meaning the consolidation process can take a long time. When building on top of fine grained soils, a higher water content is not desired as consolidation settlement can occur over time. The rate of consolidation will depend on soil nature, degree of saturation and load applied.

''(''[http://kshitija.wordpress.com/ http://kshitija.wordpress.com]'')''

'''Why the technique is used? '''

The technique of empoldering is well known in the Netherlands. Polders are reclaimed from land that has been submerged by the sea, they are used to prevent rising water pressures and floods. The technique is important particularly in the Netherlands as land is susceptible to high risk of floods. The sea levels in and around the area are much higher than the land meaning that most of the Netherlands is submerged below sea level.

Dikes can be used to build a barrier to stop the flow of water reaching land. This helps to make sure that water does not affect the ground. Water can seep into soil and affect the characteristics of the soils. Such characteristics may be the colour, shape, strength and cohesion.

Properties such as soil porosity, effective stress, pore water pressure; density of soils needs to be considered.

'''Geotechnical conditions'''

Ground conditions can have an effect on what types of structures are built. Soil types must first be identified to determine the ground structure. The geotechnical conditions in the Netherlands are comprised of clays. This is more common near river deposits. Other types of soils commonly present in areas of the Netherlands are sandy clays, peaty layers and mineral soils. In coastal areas, groundwater is saline this is because of sea water intrusion. (Struyfuz and Stuurman, 1994).

Case studies on water balances on polders were carried out. The studies had found that the seepage occurred through clay and peat with low permeability. Studies later found that groundwater seepage could occur through pathways. (Becker et al., 2004, Kalbus et al., 2009). Below is a diagram outlining the location of deep polders (reclaimed lake areas) in the Netherlands showing monitoring points and main ditches.

'''(Fig 3) '''

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Designed for dry fleet: Land reclamation in the Netherlands, page 7)''
</div>
|}

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Journal of Hydrology, page 495)''
</div>
|}

<br/>

'''(Fig 2) '''

Fig 3 shows the soils of the Netherlands. The lower elevations near the north and west shows soils such as peat, marine clay and river clay. Groundwater flow called boils has been taken into account in polders. These boils act like vents which develop when the pressure of water is high.

Water which comes into contact with land can subside over a period of time; as a result water can enter the polder through increasing water pressures.

'''How polders were maintained'''

The polders were maintained by usage of windmills, the benefits of this were to pump out excess water. These were used in the Netherlands as a means to drain the land. Pumping stations can be also used to drain water.

The wind mills help to maintain water levels. The water is controlled through drainage schemes which are usually canals. Furthermore, water is released from the polder by using a pump. The pump is needed in case water levels are higher than the water inside the polder.

These pumps can be powered by electricity or through the use of windmills for drainage of excess water.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
(''Designed for dry fleet:''

''Land reclamation in Netherlands) page 2''
</div>
|}

<br/>

'''Construction of Polders'''

Polders are generally constructed to reclaim land and protect against water. The construction of polders is done by forming dikes around the surrounding land area. The process for constructing a polder is to first remove soils which are unstable. A layer of sand fill is positioned. Two strips of boulder clay are laid; this creates the abutments of the dike. A larger strip is positioned on the side facing the sea and a smaller strip is placed upon the polder side. Spaces between the foundations are filled with asphalt; riprap and sand basalt revetments are placed.

On the whole, polders have aided the population of the Netherlands by giving more land to the public. The land can be used for agricultural purposes such as maintaining crops. I believe that the use of polders has had a positive effect for the future, especially as sea levels continue to rise in the current climate.

'''References'''

= Works Cited =

Upward Groundwater Flow and salinization in Deep Polders. (2009). ''Journal of Hydrology'', 494-507.

''A Brief History of Dutch Dikes and Polders ''. (2011, October thursday). Retrieved from [http://www.metropolismag.com/pov/20100216/a-brief-history-of-dutch-dikes-and-polders http://www.metropolismag.com/pov/20100216/a-brief-history-of-dutch-dikes-and-polders]

''Dutch Polder System 2010.'' (2011, October Tuesday). Retrieved from [http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf]

''The Polders in Netherlands ''. (2011, November Saturday). Retrieved from [http://www.docstoc.com/docs/622752/The-polders-in-the-Netherlands http://www.docstoc.com/docs/622752/The-polders-in-the-Netherlands]

''Chapter 2 Soil and Water''. (n.d.). Retrieved November Tuesday, 2011, from [http://www.fao.org/docrep/R4082E/r4082e03.htm http://www.fao.org/docrep/R4082E/r4082e03.htm]

''eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf.'' (n.d.). Retrieved October Tuesday, 2011, from Soil Remedation in the Netherlands : eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf

''Geotechnology 101''. (n.d.). Retrieved November Tuesday, 2011, from [http://kshitija.wordpress.com/ http://kshitija.wordpress.com/]

Hoeksema, R. (05/2006). Designed for dry fleet: Flood Protection and Land Reclamation in the Netherlands . 1-4.

''Impact of Water Management ''. (n.d.). Retrieved November Monday, 2011, from Levees And Polders : [http://www.cbd.int/programmes/areas/water/toolkit/html/1.13.4_%20levees%20_%20polders.html http://www.cbd.int/programmes/areas/water/toolkit/html/1.13.4_%20levees%20_%20polders.html]

Smith, I. (2006). ''Smith's Elements of Soil Mechanics .'' Blackwell Publishing .

''Soil Testing .'' (n.d.). Retrieved November Monday, 2011, from [http://www.geotechnique.info/SI/SI%20Book%20Chapter%208.pdf http://www.geotechnique.info/SI/SI%20Book%20Chapter%208.pdf]

''The remarkable history of polder systems in the netherlands .'' (n.d.). Retrieved Ocotober Tuesday, 2011, from [http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf]

[[Category:Student_engineer_essay_competition]]

Polders

2012-12-12T18:20:40Z

Ajmal: Created page with "<div align="center"> {| width="100%" style="width: 100%;" border="0" cellspacing="0" cellpadding="0" |- | style="width: 100%; height: 192px;" | Teesside university |} Assignme..."

<div align="center">
{| width="100%" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%; height: 192px;" |
Teesside university

|}

Assignment 1 – Polders and Consolidation

Geotechnology

'''Ajmal Hussain'''

'''12/1/2011'''
</div>

{| width="100%" align="left" style="width: 100%;" border="0" cellspacing="0" cellpadding="0"
|-
| style="width: 100%;" |
In this assignment I will discuss what polders are, why they are used extensively in the Netherlands, how they can be constructed and maintained. The effects that they may have on structures and an outline of the geotechnical conditions which makes them popular in the Netherlands and their related consolidation.

|
|}

<br/>

'''Contents '''

Introduction........................................................................................................... (2)

What are polders………………………………………………………....................... (2)

Consolidation ………………………………..………………………......................... (3)

Why the technique is used……………………………………………...................... (3)

Geotechnical Conditions……………………………………………………………… (4)

How polders are maintained……………………………………………………… (5)

Construction of polders…………………………………………………………… (5)

References…………………………………………………………………………… (6)

'''Introduction '''

Polders are considered to be low lying land which consists of physical barriers, these are known as dikes.

Polders are commonly used in the Netherlands as floods are of high risk to the land; this is due to land being beneath the mean sea level. To prevent this, dikes and protective embankments (barriers) had been built to stop water from flooding the Netherlands. The benefit of using a polder system is that it can aid in flood reduction.

'''What are polders?'''

A polder is basically an area which is surrounded by dikes where groundwater level is artificially controlled; usually this is done by a berm or a dike, in other words groundwater levels are maintained by a drainage system. This involves drainage systems such as ditches and canals which deliver water to the perimeter of the polder. Polders can be laid near a river or sea for easier drainage. It consists of artificial land barriers called dikes. Dikes are walls whose main function is to protect polders and to stop water from flowing to them. The dikes are used as a barrier between the reclaimed land and the sea. Marshes and canals can be formed using dikes. This is due to water seepage under the wall of the dike.

When dikes are constructed next to rivers, the land is below the sea level. In this case there are two boundary dikes which are used to protect polders from varying sea level changes throughout the year. The front dike is called a summer dike and the back dike is called the winter dike. In the winter the summer dike is below sea level, during summer the summer dike spreads to the surrounding land.

The diagram shows the areas with traditional polders (red dotted circle) and the area with modern highlighted in yellow.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Dutch Polder systems 2010, page 2)
</div>
|}

<br/>

'''Consolidation '''

Consolidation in soil mechanics is the compression of soils. By compressing the soils it reduces the water content making the soil denser. This is consolidation of soils. Consolidation occurs when the ground weakens due to an increased stress load on the soil. As a result the soil reduces in volume.

When a soil reduces in volume and consolidates this can affect the structures that are built on top. When a soil consolidates forces in the soil are reduced. As soils are loaded with greater forces, the structure will break down depending on the type of soil. The increasing effect of stress and water can change the ground conditions and lead to consolidation. Peat and clay tend to consolidate, this results in land subsidence and cracking.

Due to the high water content in the soils, consolidation is likely to occur when building upon the land. This can lead to the ground sinking through the applied loads of the structures. The main reasons for consoildation occuring is shrinkage and soil consolidation. As groundwater is reduced the buoyancy forces in the soil decrease therefore an increase in the total effective stress of the soil takes place. To minimise consolidation settlement, you would need to consider the amount the ground will settle and the rate at which settlement will occur with a specific applied load placed upon it.

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
Figure 1
</div>
|}

Figure 1 shows the different water level content in fine grained soils. The level of permeability in fine grained soils is low meaning the consolidation process can take a long time. When building on top of fine grained soils, a higher water content is not desired as consolidation settlement can occur over time. The rate of consolidation will depend on soil nature, degree of saturation and load applied.

'' (''[http://kshitija.wordpress.com/ http://kshitija.wordpress.com]'')''

'''Why the technique is used?

The technique of empoldering is well known in the Netherlands. Polders are reclaimed from land that has been submerged by the sea, they are used to prevent rising water pressures and floods. The technique is important particularly in the Netherlands as land is susceptible to high risk of floods. The sea levels in and around the area are much higher than the land meaning that most of the Netherlands is submerged below sea level.

Dikes can be used to build a barrier to stop the flow of water reaching land. This helps to make sure that water does not affect the ground. Water can seep into soil and affect the characteristics of the soils. Such characteristics may be the colour, shape, strength and cohesion.

Properties such as soil porosity, effective stress, pore water pressure; density of soils needs to be considered.

'''Geotechnical conditions'''

Ground conditions can have an effect on what types of structures are built. Soil types must first be identified to determine the ground structure. The geotechnical conditions in the Netherlands are comprised of clays. This is more common near river deposits. Other types of soils commonly present in areas of the Netherlands are sandy clays, peaty layers and mineral soils. In coastal areas, groundwater is saline this is because of sea water intrusion. (Struyfuz and Stuurman, 1994).

Case studies on water balances on polders were carried out. The studies had found that the seepage occurred through clay and peat with low permeability. Studies later found that groundwater seepage could occur through pathways. (Becker et al., 2004, Kalbus et al., 2009). Below is a diagram outlining the location of deep polders (reclaimed lake areas) in the Netherlands showing monitoring points and main ditches.

'''(Fig 3) '''

{| width="100%" cellspacing="0" cellpadding="0"
|-
| <div>
''(Designed for dry fleet: Land reclamation in the Netherlands, page 7)
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''(Journal of Hydrology, page 495)''
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'''(Fig 2) '''

Fig 3 shows the soils of the Netherlands. The lower elevations near the north and west shows soils such as peat, marine clay and river clay. Groundwater flow called boils has been taken into account in polders. These boils act like vents which develop when the pressure of water is high.

Water which comes into contact with land can subside over a period of time; as a result water can enter the polder through increasing water pressures.

'''How polders were maintained'''

The polders were maintained by usage of windmills, the benefits of this were to pump out excess water. These were used in the Netherlands as a means to drain the land. Pumping stations can be also used to drain water.

The wind mills help to maintain water levels. The water is controlled through drainage schemes which are usually canals. Furthermore, water is released from the polder by using a pump. The pump is needed in case water levels are higher than the water inside the polder.

These pumps can be powered by electricity or through the use of windmills for drainage of excess water.

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'''Construction of Polders'''

Polders are generally constructed to reclaim land and protect against water. The construction of polders is done by forming dikes around the surrounding land area. The process for constructing a polder is to first remove soils which are unstable. A layer of sand fill is positioned. Two strips of boulder clay are laid; this creates the abutments of the dike. A larger strip is positioned on the side facing the sea and a smaller strip is placed upon the polder side. Spaces between the foundations are filled with asphalt; riprap and sand basalt revetments are placed.

On the whole, polders have aided the population of the Netherlands by giving more land to the public. The land can be used for agricultural purposes such as maintaining crops. I believe that the use of polders has had a positive effect for the future, especially as sea levels continue to rise in the current climate.

'''References'''

= Works Cited =

Upward Groundwater Flow and salinization in Deep Polders. (2009). ''Journal of Hydrology'', 494-507.

''A Brief History of Dutch Dikes and Polders ''. (2011, October thursday). Retrieved from http://www.metropolismag.com/pov/20100216/a-brief-history-of-dutch-dikes-and-polders

''Dutch Polder System 2010.'' (2011, October Tuesday). Retrieved from http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf

''The Polders in Netherlands ''. (2011, November Saturday). Retrieved from http://www.docstoc.com/docs/622752/The-polders-in-the-Netherlands

''Chapter 2 Soil and Water''. (n.d.). Retrieved November Tuesday, 2011, from http://www.fao.org/docrep/R4082E/r4082e03.htm

''eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf.'' (n.d.). Retrieved October Tuesday, 2011, from Soil Remedation in the Netherlands : eusoils.jrc.ec.europa.eu/library/data/eionet/.../Netherlands.pdf

''Geotechnology 101''. (n.d.). Retrieved November Tuesday, 2011, from http://kshitija.wordpress.com/

Hoeksema, R. (05/2006). Designed for dry fleet: Flood Protection and Land Reclamation in the Netherlands . 1-4.

''Impact of Water Management ''. (n.d.). Retrieved November Monday, 2011, from Levees And Polders : http://www.cbd.int/programmes/areas/water/toolkit/html/1.13.4_%20levees%20_%20polders.html

Smith, I. (2006). ''Smith's Elements of Soil Mechanics .'' Blackwell Publishing .

''Soil Testing .'' (n.d.). Retrieved November Monday, 2011, from http://www.geotechnique.info/SI/SI%20Book%20Chapter%208.pdf

''The remarkable history of polder systems in the netherlands .'' (n.d.). Retrieved Ocotober Tuesday, 2011, from http://www.fao.org/fileadmin/templates/giahs/PDF/Dutch-Polder-System_2010.pdf

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