If the concentration of harmful salts in the root zone of a plant increases to such an extent that plant growth is effected, this situation is called Salinity.

Salinity is the measure of all the salts dissolved in water. Salinity is usually measured in parts per thousand (ppt or % ). The average ocean salinity is 35ppt and the average river water salinity is 0.5ppt or less.

Salinity is the saltiness or dissolved salt content of a body of water (see also soil salinity).
Salinity is the concentration of dissolved salts found in water. It is measured as the total amount of dissolved salts in parts per thousand (sometimes called PSU or Practical Salinity Units by scientists).  Ten parts per thousand is equal to one percent.   Salinity in seawater averages 34 parts per thousand or 3.4% but bay waters may vary widely from 0 to 34 PSU.

Causes of Salinity

The factors contributing towards the problem of salinity are almost same as that of water logging.
Every agricultural soil has certain mineral salt is also called alkali salts in it like NaCl, Na2CO3,  Na2 SO4 etc.

 When these soluble alkali salts are excess in soil and further ground water table is very near to ground, these salts get mixed with ground water  and with upward movement of   water not only accumulated in first 3~4ft of soil layer below ground surface but also form a tin 2”~3” crust on surface.

Treatment of Salinity

Salinity is treated by following methods :-

  • Treatment by Leaching Process
  • Chemical Treatment
  • Treatment by Mulching

Treatment by leaching process

Step 01.
Providing adequate sub surface artificial drainage.
Step 02.
Leaching salts from the top 3~4ft of soil to ground water table by flooding the land.
Step 03.
Growing salt resistant crops (e.g. rice in summer and Bar seem in winter) for one or two seasons.

Treatment by Mulching

It involves covering the effected land with a covering of soil (Mulch) to reduce evaporation losses.

If water table rise to such a level through capillary action to the surface & root zone, that it cannot conveniently permit an anticipated activity this situation is called Water Lodging.  

Water Lodging, What it is? and How to prevent and Control it?
Water Lodging, What it is? and How to prevent and Control it?

Water lodging means the saturation of soil with water. Soil may be regarded as waterlodged when the underground water table goes too high to conveniently permit agriculture and other similar activities.

Water lodging or Water logging is a process that prevent growing of plants in soil. The soil is saturated with water and air cannot get in or in simple words excess water in the root zone. 

Causes of Water Lodging

The numerous reasons and causes for water lodging is enlisted below :- 

  • Inadequate surface Drainage
  • Seepage from canal system
  • Over irrigation of fields
  • Obstruction of natural drainage
  • Impermeable clay layer below the soil
  •  Obliteration of natural drainage
  • Inadequate capacity for arterial drainage
  • Construction of a water reservoir
  • Natural obstruction to the flow of ground water

Preventive Measures to Avoid Water Lodging

  • Providing efficient surface Drainage.
Surface drainage is done by grading an area so that water collects and flows to a lower elevation away from the required area. Along with surface characteristics, when it comes to surface drainage, slope is the most important factor to consider. For efficient drainage, paved surfaces should have a minimum 1-percent slope. Turf or landscaped areas should have a minimum slope of 2 percent.
  •  Reducing percolation from canals.
Technological measures to reduce seepage, leakage and percolation losses in irrigation include the lining of canals and watercourses, and promoting modern irrigation technologies such as pipe, sprinkler and drip systems.

Re-modeling of Surface Drains
Re-modeling of Surface Drains

  •  Restriction of irrigation. 
  •  Adoption of sprinkler method for irrigation
Sprinkler irrigation sprays water over the fields. A sprinkler system consists of a pumping unit, a pressurized pipe conveyance network, and a set of nozzles. Its favorable features are: high level of field WUE; uniform water distribution over the field, which increases yields; and minor dependence on the condition of the soil surface. When sprinkler irrigation is practiced during the night, water losses can be further reduced due to lower evaporation losses. However, sprinkler systems have high initial capital costs and require good maintenance. Running costs are high due to energy consumption during operation. Moreover, sprinkler irrigation is not equally effective for all crops.

Canal Lining
Canal Lining

  •  Removing obstructions in natural drainage.
All embankments, grades, dikes or obstructions of whatever kind constructed or maintained within the city that is causing obstruction to the natural surface drainage of water must be avoided 
  •  Changes in crop pattern.

The Executive Committee of the National Economic Council (ECNEC) approved a project worth Rs. 12 billion to construct a six-lane highway from Kala Shah Kaku to Lahore Ring Road.

Finance Minister Ishaq Dar chaired the meeting of the Executive Committee of the National Economic Council (ECNEC) at the Prime Minister’s Office in Islamabad.

“Construction of 6-Lane Highway from Kala Shah Kaku to Lahore Ring road (18.30 Km) including Bridge over River Ravi (Lahore Eastern Bypass) was approved by ECNEC at the total cost of Rs.12, 848.047 million,” states a press release issued by the government.

The scope of work also includes construction of 6-lane bridge over River Ravi spanning 800m, 2 bridges over railway crossings, 4 bridges on nullahs, 5 underpasses, 3 interchanges, 17 cattle creeps, 12 culverts, drainage, erosion and flood protection works.

The executing agency for the project will be the National Highway Authority. The project will be completed in a period of 24 months .

There are a number of excellent books on construction claims; and many other construction books that devote sections and chapters to construction claims. However, the majority of these works give very little guidance on the preparation of time-related delay claims, and even less guidance on the preparation of extension of time submissions.

Throughout this book the term “delay analsysis” is used, being a generalization to cover both extension of time submission and the time-related aspects of delay claims. Although there are various sophisticated delay analysis techniques around today, in its essence delay analysis is a fact based process.

The aim here is to provide this guidance, particularly in relation to extension of time submission. The contents of this volume are intended to outline the information and practical details to be considered when formulating extension of time submissions and time-related delay claims.

One of the recurring themes is good record keeping on projects. While a lack of progress-related records may not be fatal to a claim, it does make reaching a reasonable settlement an uphill battle.

Readers will observe my continuing advice on good record keeping.
This book will provide useful guidance for those responsible for preparing extension of time submissions and time-related delay claims as well as for those dealing with them, the aim being that they can be resolved amicably, professionally and without either party being seriously disadvantaged.

Title of the Book

Construction Delays Extensions of Time and Prolongation Claims

Author of the Book

Roger Gibson

Contents of the Book

Part 1 – Introduction
Part 2 – Programmes and Record Keeping
Part 3 – Contracts and Case Law
Part 4 – The ‘Throny issues’
Part 5 -  Extension of Time
Part 6 – Prolongation claims (and time-related costs)

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Civil Engineering Conventional and Objective type by R.S. Khurmi and J.K. Gupta needs no introduction in the field of Civil Engineering as it is well known, popular and famous. The Book is best for the students of U.P.S.C. (Engg. Services); I.A.S. (Engg. Group); B.Sc. Engg.; Diploma and other competitive courses.

After the first edition in 1984 the book is a must to go through for any competitive exams related to civil engineering and construction. The book has 16 wide range of sections in which all the details are given at the start of each chapter with MCQs at the end.

Title of the Book

Civil Engineering Conventional and Objective Type

Author of the Book

R.S. Khurmi
J.K. Gupta

Contents of the Book

1. Engineering Mechanics
2. Strength of Materials
3. Hydraulics and Fluid Mechanics
4. Hydraulic Machines
5. Surveying
6. Building Materials
7. Irrigation Engineering
8. Public Health Engineering
9. Highway Engineering
10. Railway Engineering
11. Soil Mechanics and Foundations
12. Building Construction
13. Concrete Technology
14. Reinforced Cement Concrete Structures
15. Steel Structures Design
16. Construction Management

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Reinforced cement concrete is the widest used construction material in civil engineering whether it is that of dam, highway bridges, buildings or infrastructures. Reinforcement used along with concrete proves to be the best available material in terms of economy, strength and sustainability. Choice of reinforcement within a structural member is due to countless advantages and benefits. 

The question asked in the title is among those common confusions that exists between professional practicing engineers and site managers. Thus, here we are providing you the article to remove such confusion. 

In order to subject the steel reinforcement to ultimate stress especially in tension, we need to make sure that it is firmly fixed at both ends and doesn’t slip out. Absence of such an arrangement would result in stress concentration in steel, cracks in concrete and even failure of the member. 

Development length anchorage and lap length serve the same purpose but in different situations. Their main function is to provide sufficient bond strength between the reinforcement and concrete. 

Lap Length, Splice Length or Overlap Length

Lap Length addresses the length of the bar needed to transfer the stresses to the other bar whereas development length addresses the length of the bar needed to transfer the stresses to the concrete. 

Lap length is different in case of tension and compression zones and mainly depends on grade of concrete and steel. 

If two different dia bars are to be lapped, lap length is based on smaller dia.

The values of the development length and that of splice length is that for uncoated reinforcement and of normal weight concrete. 

If the rebars are bundled than the following multipliers shall be applied to the values in above given table. 

a) 3-Bar bundles in Tension or Compression   = 1.20 x Table values
b) 4 – Bar Bundles in Tension or Compression = 1.33 x Table values 
c) Lap splices for each bar in a bundle shall be staggered. Entire bundles shall not be lap spliced. 

Similarly in the table there are words used “Top bars” and “other Bars” so here is a definition for these terms :- 

Top bars are horizontal bars in the top face / layers (s) of beams and slabs, so placed that more than 300 mm of fresh concrete is cast below the bar being developed or spliced. 

All other horizontal and vertical bars in beams, slabs and walls shall be classified as other bars, unless otherwise noted on the drawings. 

Laps or Lap splices are usually needed in following two situations :- 

1) A long rebar more than 12 m is to be provided in such a case two bars of required length are lap spliced. 

2) The rebar is changing its shape or direction in a way that there is no possibility for a single rebar to complete the shape as required by the structure. 

In Ideal situations these lap splices and laps are to be avoided and must be single rebar as these zones are vulnerable for having less strength as that of the single rebar. Therefore, Lap splices shall not be used in locations of maximum moments unless otherwise permitted on the construction drawings. 

Classes of Splices 

The values as given in the table are considered as class ‘B’ splice for class ‘A’ splice 

Splice length = 0.77 x Table value but not less than 300 mm. 

When rebars of different diameters are lap splices, splice length shall be larger of :- 

Development length of larger bar and splice length of smaller bar. 

Development Length

As per the standard; “the calculated tension or compression in any bar at any section shall be developed on each side of the section by an appropriate development length or by end anchorage or by a combination thereof. 

Anchorage Length

Anchorage length is provided if sufficient development length cannot be able to be provided inside the support/fixed end. L value is generally considered as 8 times dia for a 90 degree bend while 6 times dia for a 135 degree bend and 4 times dia of bar for a 180 degree bend. In most all cases, we use 90 degree bend. 

We need to check for the development length in cases for tension reinforcement at supports of continuous beams and cantilever supports. 

For various reasons, including but not limited to climate change, water shortages caused by droughts are becoming an issue – particularly in large cities in places like California. There are a number of ways to cope with this problem, but they boil down to two main categories: reducing the demand, and increasing the supply.

New conservation technology, repairing crumbling infrastructure, legislation to lower the amount of water used for high demand activities like irrigation, are all being pushed to reduce demand. While regional imports, better treatment of wastewater, and coastal desalination are being employed to increase supply. All these have their advantages and disadvantages, but all have a possible part to play in ensuring that world water needs continue to be met.

Conservation Efforts

The most obvious way to save water is to use less of it, but it’s not always that simple. A huge amount of water is wasted in the US every year. For example, the city of Daytona Beach, FL, estimates that a tap leaking ten drips per minute wastes an incredible 526 gallons of water per year – and that’s just one tap. Toilet design in the US compared with Europe is also an issue; in Europe, low-flush toilets use an average of 0.8 gallons per flush, while in the US, a low-flush toilet might use 1.3 gallons. These differences obviously mount up over time, and there is little incentive for everyone in the US to go out and buy a low-flush European toilet.

Bans on watering lawns are also an option, although people are resentful of being told to ration their water. In California, governor Jerry Brown signed a $687 million relief package during the recent drought to promote storm water recapturing, expanding the use of recycled water, and better management of groundwater storage.

Fixing Leaks

Water conservation efforts also have to focus on infrastructure if they are going to be successful. There are many products on the market that are able to assist governments and businesses with monitoring their water supply infrastructure. In fact, these techniques have been used for a variety of projects including in municipal works, military bases, private water suppliers, power generation, manufacturing, food and beverages, commercial airports, chemical refineries, construction, and educational and corporate campuses. Not only can these technologies help their users save water, they will often make significant cost savings as well.

So what kinds of technologies are we talking about? These days, there are many products available that can help users to deal with problematic water systems. For example, pipeline condition assessment uses acoustic signals to allow engineers to quickly determine the current condition of a segment of pipe, assigning it a grade based on its state of degradation. And with water main leak detection, systems can use acoustic leak-detection technology and wireless connectivity to allow users to monitor their pipelines in real time in large or small diameter water mains of all types, from PVC to cast iron to copper. Replacing pipes before they wear out and catching leaks as soon as they happen can go a long way toward avoiding the wastage of water.

Increasing Supply

One way to increase the water supply comes with a bit of a ‘yuck’ factor: recycling wastewater into drinking water. Wastewater treatment plants are nothing new of course, but recent innovations have made it possible to treat raw sewage much more quickly and inexpensively. For example, billionaire philanthropist and former Microsoft CEO Bill Gates has sponsored a project that does just that, and uses temperatures at 1000 °C to turn waste into drinking water, producing electricity and a small amount of ash in the process. There was even a video of Gates drinking the resulting water; reportedly, it was delicious.

Such systems are meant for third world countries where the biggest obstacle to getting clean water is a lack of expensive infrastructure. That is less of an issue for North America (although the decay of infrastructure is, as noted above, a problem in itself), but it might still be worth considering how an inexpensive piece of equipment might be modified to be of use to Westerners. With the buzz around micro-power generation using solar panels or small wind turbines, having an in-house treatment plant might be the next big thing in water conservation. Of course, as ever, time will tell.

Provision of reinforcement in concrete, we all know, is due to its tension carrying capability which can be utilized completely provided the bond between the steel reinforcement and concrete is up-to-the-mark and does not lack any required friction and anchorage. However this bond may fail in certain situations which is disastrous and fatal, thus in order to avoid we must find some alternatives and with safety factor we can minimize and may completely eliminate chances of failure.  

It is usually observed in Reinforced concrete structures that if the reinforcement has sufficient quantity of concrete surrounding along with large concrete cover and bar spacing the failure of bond usually occurs by direct pullout of reinforcing bar. On the other hand, in contrast, insufficient cover and confinement leads to bond failure by splitting of concrete. 

The anchorage and holding power of concrete for reinforcement can be enhanced by providing development length and end hooks if required. In this post we will look forward only towards development, What development length is? How it can be calculated and How it reduces the risks of bond and anchorage failure. 

Before going into the details lets discuss some important points and literature review about the bond strength between reinforcement and the concrete; 

Discussion about Development Length

In the modern reinforced concrete works, the rebars used are usually of deformed shape with ribs in perpendicular or inclined directions depending on the brand and factory standards, purpose of these ribs is to provide mechanical interlock with the concrete which, now a days is more important than the adhesion and frictional resistance. 

The reinforcement provided in a structural element of a building like a beam; is subjected to bond forces acting on reinforcing bars. These forces are caused due to flexural and shear stresses within the member. These bond forces and stresses might result in the sliding of the steel relative to the concrete provided the pullout resistance has overcome and splitting has spread all the way to the end of the rebar which would lead to immediate collapse of the structure. 

The bond failure immediately adjacent to the cracks will often occur at loads considerably below the failure load of the beam. These local failures result in small local slips and some widening of cracks and increase of deflections, but will be harmless as long as failure does not propagate all along the bar, with resultant total slip. 

If the end anchorage of the rebar is reliable such failures can be avoided; these end anchorage can be provided by hooks or by extending the straight rebar a sufficient distance from the point of maximum stress. 

Definition of Development Length

Based on above discussion we are now able to define what is development and why the rebar needs to be developed along certain sufficient length. 

Development length is defined as the embedment length necessary to develop the full tensile strength of the bar, controlled by either pullout or splitting and thus avoiding any bond failure within the member. 

Example of Development Length

Now let us consider an example to better understand the meaning of development length ;- 
In the above figure a simple beam is shown of a certain length with two vertical forces / loads at locations as shown; it is obvious from the diagram that while neglecting the self weight of the beam, the stressed would be maximum at point a on the rebar as shown. 

If the stress on rebar at a is taken as fs, than the total tension force would be Ab fs where Ab is the area of beam and fs is the stress in steel. This total tensile force must be transferred from the bar to the concrete in the distance l by bond forces. This length l must be equal to or greater than the development length of the rebar as per its diameter in order to avoid premature bond failure. 

Factors Affecting Development Length

There are both simplified and comprehensive equations out there in the literature to calculate and find out the development for a certain situation. Based on this here is a summary of the factors as given in ACI code for the development length. 

1. Compressive Strength of the Concrete : - the development length required for a rebar is inversely related to the compressive strength of the concrete which means if more is the compressive strength than less would be the required development length. 
2. Density of the concrete (Light weight or normal weight) : For light weight concretes, the tensile strength is usually less than for normal density concrete having same compressive strength; accordingly, if lightweight concrete is used, development lengths must be increased. 
3. Rebar Clear Cover : Clearly, if the vertical or horizontal cover is increased, more concrete is available to resist the tension resulting from the wedging effect of the deformed bars, resisting to splitting is improved, and development length is less. 
4. Rebar Center to Center Spacing: if the rebar spacing is increased than more concrete will be available per rebar to resist horizontal splitting. In Beams, bars are typically spaced about one or two bar diameters apart. On the other hand, for slabs, footings, and certain other types of member, bar spacings are typically higher and thus required development length is less. 
5. Transverse Reinforcement : Transverse reinforcement like that of shear stirrups improves the resistance of tensile bars to both vertical and horizontal failures because the tensile force in the transverse steel tends to prevent the opening of the crack Thus if the transverse reinforcement is present the development length required would be much less. 
6. Vertical location of the horizontal rebar : It has been observed that if excess fresh concrete is casted below a rebar of more than 12 inches than there is a tendency for excess water, often used in the mix for workability, and for entrapped air to rise to the top of the concrete during consolidation and resultantly reduced bond strength. Thus more development length is required in such cases. 
7. Coating of rebar : Sometimes in some projects where the structure is subjected to corrosive environmental conditions or deicing chemicals epoxy coated rebars are used instead of normal rebar. Studies have shown that in such cases the bond strength is reduced and thus more development length is required. 
8. Rebar Diameter : most important and common factor that would influence the development length is the diameter of the reinforcement used. It has been observed that smaller diameter bars require lower development length than that of the larger diameter rebar. 
I hope after reading this article you are now able to fully understand the definition of development length, the requirement of development length and the factors of the development length. In some future articles we would be discussing on how to calculate the development length with ACI Equations, so stay tuned and Happy Civil Engineering. 

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Pakistan is facing serious challenges on both the ends of power sector and water shortage. The desperation and need of both requires strong footsteps and commitment with the national cause. Recently on Tuesday Institute of policy Reforms of Pakistan issued an alarming situation proving water shortage as even a bigger and worse problem than power scarcity. 

Although there are many Projects in power sector which are underway but none of those Dams are not enough to suffice the needs of water in the region. Diamer-Bhasha dam, a 272 meter high dam with power generation capacity of 4500 MW, has an important advantage to store 85 million acre feet of water that can be used for irrigation as well as drinking.  

Diamer-Bhasha Dam after facing series of setbacks since the laying of foundation stone on 18-Oct-2011 is now again under construction. On Monday 05-Oct-2016 PM Nawaz Sharif approved the principal financing plan by ordering the secretary of water and power to start physical work on the dam before the end of 2017. 

Although the design and the detailed drawings of the Diamer-Bhasha Dam was completed way back before 2009 by due to financial implications the project was unable to start and progress until 27-Aug-2013 when Finance Minister, Ishaq Dar have convinced the World Bank and Aga Khan Development Network to finance the Diamer-Bhasha Project.  Agha Khan Foundation has agreed to become lead finance manager for the project. 

Until 2013 17 thousand acres of land had already been received by WAPDA from Government of Gilgit Baltistan for the construction of the project.  It is to be noted here that as per the estimate of 2013 the construction cost of the project is approx. $14 billion and it would require 10-12 years for its completion. 

The design of the project is Gravity Dam made of Roller Compacted Concrete (Usual Mass concrete that is mechanically compacted with Vibratory Rollers) impounding Indus River having a spillway of 272 m high. 

After completion of the project it would be the highest RCC dam in the world. It is located in District of Bahsha in area called Diamer which is aprox. 315 km upstream of Terbela Dam in Gilgit. 

For easiness of the construction two diversion tunnels and 1 diversion canal is proposed with upstream and downstream cofferdam as obvious. The initial design includes 09 spillway sluices of approx. 16 x 15 m. 

The reservoir having capacity of apro. 1000 million cubic meters at elevation of 1060 m. Due to which it will not only reduce the destruction caused by flooding in Indus River but will also increase the life of Terbela Dam by approx. 35 years. 

There are two power houses proposed with total capacity of 4500 Mega Watts located on right and left side of the dam. 

Yesterday I was watching documentary on a Bridge having piers founded in the water and was wondering how engineers and constructors are able to lay pile foundation in such a high-speed flowing water of river.

 After research of few hours I have got a handful of knowledge about the technique we would be dealing with in this article. 
The technique is called a Coffer Dam. After finding from the dictionary It says the word Coffer means a casket, chest or trunk. Which , in words means a safe place to work within. Thus the definition would be :- 

A coffer dam is a temporary structure built to enclose and encase an area that is meant to be excavated for the construction of foundation. 

Cofferdams are used when the size of excavations is very large and sheeting and bracing system becomes difficult, inconvenient or uneconomical. Coffer dams are generally required for foundations of structures, such as bridge piers, docks, locks, and dams, which are built in open water. These are also used for laying foundations on open land where there is a high ground water table. A cofferdam generally consists of a relatively impervious wall built around the periphery of the proposed excavation to prevent the flow of water into the excavation so that the foundation may be laid in dry condition. 

Although the coffer dams are of many types which depends on the needs of the jobsite and also on the output you needed from the coffer dam. However, there are some common types which we will discuss here :- 

1 ) Earth Coffer Dams 

These are the simplest type of coffer dams well-adapted to depths of water upto 3 m. Earth embankments are constructed around the area to be dewatered. The earth coffer dams are built of local soils, preferably fine sand. 

These usually have a clay core or a vertically driven sheet piling in the middle. The upstream slope of the bank is covered with a rip rap. A successful coffer dam need not be completely water tight. For reasons of economy it is not possible to make it watertight and hence some seepage of water into the excavation is usually tolerated. The water collected is pumped out of the excavation. The embankment should be provided with a minimum free board of 1 m to prevent overtopping by waves. 
Sand-bag coffer dams are used in an emergency. 

2) Rockfill Coffer Dams 

Rockfill coffer dams made of rockfill are sometimes used to enclose the site to be dewatered. These are permeable and are usually provided with an impervious membrane of soil to reduce seepage. The crest and the  upper part of the impervious membrane are provided with rip rap to provide protection against wave action. Overtopping does not cause serious damage in case of rockfill coffer dams. The slopes of rockfill coffer dam can be made as steep as 1 horizontal to 1.5 vertical. 

3) Single-Sheet Pile Coffer Dams

Single-sheet piling coffer dams are generally used to enclose small foundation sites in water for bridges at a relatively shallow depth. In this type of coffer dams, there is a single row of cantilever sheet piles. The piles are sometimes heavily braced. Joints in the sheet piles are properly sealed. This type of coffer dams are suitable for moderate-flow velocities of water and for depth upto 4 m. The depth of penetration below ground surface is about 0.25 h for coarse sand and gravels, 0.50 h for fine sand and 0.85 h for silts, where h is the depth of water. 
Sometimes, Single-sheet pile coffer dams are provided with earth fills on one or both sides to increase the internal stability. 

4) Double-wall sheet piling coffer dams

A double wall sheet piling coffer dam consists of two straight, parallel vertical walls of sheet piling, tied to each other and the space between walls filled with soil. The width between the parallel piles is empirically set as (h/2 1.50 m), where h is height of water. Double-wall sheet piling coffer dams higher than 2.5 m should be strutted. Sometimes, an inside berm is provided to keep the phreatic line within the bottom. The fill material should have a high coefficient of friction and unit weight so that it performs as a massive body to give the coffer dam stability against sliding and overturning. Suitable measures should be adopted to reduce the uplift on the coffer dam. This is generally done by driving the sheet piling on the upstream as deep as possible. The double-wall sheet piling coffer dam has the advantage of having less leakage than that in a single-wall coffer dam. These coffer dams are suitable upto a heightof 10 m. 

5) Braced Coffer Dams 

A braced coffer dam is formed by driving two rows of vertical sheeting and bracing with wales and struts. The braced coffer dams are susceptible to flood damage. 
Land Coffer Dams. Braced Coffer dams are sometimes used as land coffer dams to prevent ground water from entering the foundation pit on land and to support the soil so as to prevent cave in. After the pit is dewatered, the structure is concreted. When concreting has been completed above the water level, the coffer dam is removed. 

6) cellular Coffer dams 

A cellular coffer dam is constructed by driving sheet piles of special shapes to form a series of cells. The cells are interconnected to form a watertight wall. These cells are filled with soil to provide stabilsing force against lateral pressure. Basically, there are two types of cellular coffer dams that are commonly used. 

i) Diaphragm type 

This type of cellular cofferdam consists of circular arcs on the inner and outer sides which are connected by straight diaphragm walls. The connection between the curved parts and the diaphragms are made by means of specially fabricated Y-element. The coffer dam is thus made from inter-connected steel sheet piles the cells are filled with coarse-grained soils which increase the weight of the coffer dam and its stability. The leakage through the coffer dam is also reduced. 

To avoid rupture of diaphragms due to unequal pressure on the two sides, it is essential to fill all the cells at approximately the same rate. One advantage of the diaphragm type is that the effective length of the coffer dam may be increased easily by lengthening the diaphragm. 

ii) Circular Type 

It consists of a set of large diameter main circular cells interconnected by arcs of smaller cells. The walls of the connecting cells are perpendicular to the walls of the main circular cells of large diameter. The segmental arcs are joined by special T-piles to the main cells. The circular-type cellular coffer dams are self-sustaining, and therefore independent of the adjacent circular cells. Each cell can be filled independently. The stability of such cells is much greater as compared with that of the diaphragm type. However, the circular cells are more expensive than the diaphragm type, as these require more sheet piles and greater skill in setting and driving the piles. Because the diameter of circular cells is limited by interlock tension, their ability to resist large lateral pressure due to high heads is limited. 

Pakistan, a large-growing populated area with countless opportunities of investments and progress has recently been involved in a close bilateral relations with China. Recently, both the parties are reaching the heights of their friendship and partnership under the flag of CPEC acronym for China Pakistan Economic Corridor. 

This Economic Corridor accompanies countless notable projects worth billions of US Dollars that are attracting overseas investors from different regions. One of the core focus of CPEC is the energy crises in Pakistan where the people are facing some serious damage in the name of water shortage as well as load-shedding in the form of electricity cut-off for several hours intermittently. 

In the past, despite of loads of opportunities for a small scale dam or hydropower projects, owing to natural potential of the country having 2nd highest mountain K-2 in Karakoram with lots of glaciers and melting waters with energy and force that can be utilized, this sector was overlooked resulting in water and energy shortage in the country. 
Keeping this is view, the private sector has shown its interest in this industry fully recognized by a body called Private Power and Infrastructure Board of Pakistan. In 2005, PPIB has announced seven most economical and feasible spots for hydropower projects in the country.

One such location was of beautiful and adorable landscape i.e. Kunhar River near peaceful Kaghan Valley of Mansehra Disctrict, Khyberpakhtunkhua (KPK), Pakistan. 

After the prequalification of a consortium named Suki-Kinari Hydro Pvt. Ltd, it was directed to conduct feasibility study of the project which after complete study and under the lights of results and documents has agreed the project to be lent by Industrial and Commercial Bank of China around August, 24, 2016. 

As per the policy laid by the Government of Pakistan regarding such Power Projects in 2002, the project will be Build-Own-Operate-Transfer (BOT). The DAM will be built by SK-Hydro group and CGGC (China Gezhouba Group Consortium) which is the same company that is working on Neelum Jehlum Hydropower Project in Azad Jammu and Kashmir, Pakistan. 

The project is a run-of-river type in which a little or no water storage is ensured at the upstream of the weir structure. This type of project is usually constructed on a river which maintain some required minimum flow which is the case here in Kunhar River. 

One of a very big advantage for a run-of-river is that there is minimum environmental disruption and minimum relocation of the inhabitants is required. 

In Suki Kinari Hydropower project the location is very ideal in this case as there is no large amount of population living and this makes the site economical and feasible. 

The project is expected to generate a power between 840 MW by Pelton Type 4 Nos of Turbine each of 210 MW and can generate an annual power of 2958 GWh which ranks it amongst helpful projects in the energy sector of the country. 

The total project cost is approx. 1.9 Billion USD and is expected to be completed by 2021. The Dam will be constructed as 54.5 meter high and 336 meter wide concrete gravity dam with 2 gated spillways. 

Construction of the dam will result in the formation of a 3.1 Kilometer long reservoir with a capacity of 9 million cubic meters of water. 

Saad Iqbal

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