COFFERDAM Group II Acmad, Aiza Corazon Banglos, Jay Bienes Christian Joy Dagondon, Cyrille Espejo, Lenra Rose Juab, Jestonie Rillera, Romulo Salcedo, Jackylyn Mae Salvejo, Mark Lester Tagupa, Kristine Neña Introduction: Among other obstacles faced in the construction process, water can be one of the most challenging and costly barriers during construction. With 71% of the earth’s surface covered in water, and new construction beginning every day, cofferdams are proving to be just as significant today as they were before the birth of Christ. By definition, a cofferdam is a work area constructed and dewatered to temporarily provide dry land for construction of various types of structures. What is cofferdam? A cofferdam is defined as a “watertight enclosure from which water is pumped to expose the bed of a body of water in order to permit the construction for a pier or other hydraulic work.” In other words, it’s a structure that is able to retain water and pump it out into a different area. Whether it stores water or pumps it in a different location, a cofferdam ensures a dry area for construction sites. COFFERDAM HISTORY OF COFFERDAM Cofferdams have been around for centuries, but they haven’t all looked or worked the same. The history of cofferdams is interesting and takes us back to the Persian empire. Here is the timeline of cofferdams used throughout history and how they have advanced through the years. 1. Earthen Cofferdam 2. Roman Cofferdam 3. Sandbags 4. Steel Sheet Pile Cofferdam 5. Aqua-Barrier® Inflatable Cofferdam Earthen Cofferdam The first cofferdams were said to be used by King Cyrus of Persia in 539 B.C. to temporarily divert water from the Euphrates river, allowing the capture of Babylon. This capture of Babylon ended their rule, allowing the Medo-Persian empire to begin. Roman Cofferdam The Romans had their own cofferdam, as well, and it was made from wood pilings that they temporarily used in order to build bridges across the Danube river in 102 A. D. in what is now Romania. Sandbags In the 1880’s, during the Napoleonic wars, people used sandbags to control water. Initially, these bags of sand were used for the protection of the troops during battle, but eventually, they were used as temporary dams and water control. Steel Sheet Pile Cofferdam After a hundred years of using sandbags, a milestone in cofferdams was introduced through the steel sheet pile cofferdam. In the early 1900’s, a German engineer came up with an interlocking design of ‘U’ shaped steel to help control water. This interlocking steel cofferdam design is still being used today in some countries. Aqua-Barrier® Inflatable Cofferdam Fast forward to 1996 and the invention of the Aqua-Barrier® cofferdam. This inflatable cofferdam features a patented internal baffle system that not only provides stability but the ability to use on any terrain, too. The Aqua-Barrier® is vastly more effective and efficient than outdate sandbags, and is also more environmentally friendly, too. Where does the word cofferdam come from? Which points are kept in mind for cofferdam constructions? 1. Depth and Flow These conditions change from season to season. Water World suggests reviewing the timing of the project and consulting the U.S. Geological Survey (USGS) to gauge fluctuations in water levels at the site to determine the best timetable for the project. 2. Permits “Turbidity requirements, contamination concerns, right-ofway restrictions, and time constraints for working in the water” are all items that may need permits or permission to conduct construction. Even though it is usually the responsibility of the project engineer to understand and obtain these permits, it is important for the contractor to know these as well. 3. Navigating the Subsurface Water world suggests that knowing, “the silt levels, slopes, vegetation and composition of the subsurface” to determine the best cofferdam technology and specifications to meet the projects needs. 4. Contractor Experience Because of the complexity of dewatering projects, it is important to hire contractors who have experience working in and around water. Experience affords the contractor the ability to understand and respond to changing conditions of the work site. They may have come across overlapping aspects in previous jobs to determine the best solutions for the current project. 5. Engineering and Design Criteria The last aspect a contractor needs to know before beginning the dewatering project is the right cofferdam technology for the project and if the cofferdam’s construction cost meets specifications. “Further, he or she should conclude if the project calls for Professional Engineer Stamped Calculations. The contractor should be well-versed in dam safety protocol and standard operating procedures and also able to provide engineering support in an emergency.” Different Types of Cofferdam It is the simplest types of cofferdam. It is used when the water depth is shallow, 1.2 m to 1.5 m and the velocity of water flow is slow. Earth Cofferdam In this type of cofferdam, an earth embankment is built around the area to be surrounded. The top width of the embankment should not be less than 1m. Its waterside slope 3/2:1 and the inner side slope is kept at 2:1. Earth embankment is made from a mixture of clay and sand or clay and gravel. Pitching is done by arranging boulder (large stone) on the slope of the waterside to prevent water damage to the embankment. Often in the middle of the embankment, Steel sheet piles are inserted to an impervious level of soil below the embankment, to prevent water from entering through the permeable layer of soil. The height of the embankment is kept 0.6 m above the water level for safety. In the workplace, a drain is kept near the embankment from which water is pumped out. Different Types of Cofferdam This types of cofferdam is useful when the water depth is up to 3.0 in and the water flow is turbulent. In this type of cofferdam, stones are used instead of clay in the bed. Such cofferdams are cheaper where stones can be easily found. Rockfill Cofferdam The disadvantage of Rockfill cofferdam is that it is not impervious. Where the water depth is low, an impermeable layer of soil is spread over the waterside of the embankment. Clay particles fill the cavities between the stones and gradually form waterlogged structures. The slope of its sides can be kept as wide as 1:1 Often the core wall or steel sheet pile inserted between the cofferdam and the bottom of the cofferdam to an impervious level of the soil to prevent water from entering the embankment. Core walls are made of clayey soil or cement concrete. Different Types of Cofferdam This types of cofferdam is made of a wooden cube. The crib is a framework made of wooden horizontal and cross beam alignment. The film is filled with stones, gravel, or clay to increase the stability of the crib against overturning or sliding. Crib or Braced Cofferdam The following conditions are favorable for this types of cofferdam: Less workspace. The river bed is hard. If the water depth is high. The water flow is an eddy type. Wood is readily available. Different Types of Cofferdam This types of cofferdam is used when the area to be surrounded is small and the water depth is high. Such cofferdams can additionally be used up to a depth of 25 m water. Single wall cofferdam Guide piles are inserted on the periphery of the area to be enclosed. The spacing of such guide piles is kept at 3m. Guide piles are usually made of wood. Steel piles can also be used if the water depth is high. The guide piles are then bolted horizontally at appropriate distances by means of wooden bolts (Wales) bolts. Then sheet piles are applied with a strut and bracing. Wood sheet piles are used for water depth up to 10 m, steel sheet piles for water depth more than 10 m. On the inside and outside of the sheet, half-filled bags of sand are rocked to increase the durability of the cofferdam. Water is pumped out of the enclosed area and foundation work is started. Different Types of Cofferdam A single wall cofferdam is costly when the enclosure area is large and the water depth is high. As the double wall cofferdam, the thickness of the components like sheet piles Strut, Wales, etc. is much more required to withstand water pressure. In such a situation a double-wall cofferdam is useful. Double wall cofferdam There are two types of double wall cofferdams: 1. Ohio type cofferdam 2. Wood or steel sheeting cofferdam with Wales and tie rods Ohio type cofferdam This type of cofferdam is called Ohio river type wood sheeting cofferdam. As it was first used for construction over the Ohio River in the United States. It can be built very cheaply and quickly. Wood or steel sheeting cofferdam with Wales and tie rods It is used in hard layers where erosion is unlikely. Such cofferdams are suitable for deep water or fast water flow. Different Types of Cofferdam This type of cofferdam is useful when the enclosure area is large and the water depth is high. Cofferdams are used in the construction of water structures such as boilers, pushes, etc. Cellular cofferdam There are two main types of cellular cofferdam: 1. Circular type cellular cofferdam 2. Diaphragm cellular cofferdam Different Types of Cellular cofferdam In Circular Cofferdam, circular cells are inserted into the ground to a certain depth above the boundary area. Such a cell is connected by an arc of a circle. The radius of such an arc is 2.5 m. The arc forms an angle of 30° to 45° instead of contact with the circular cell. The cell is filled with clay, sand, or gravel. Circular type cellular cofferdam The advantages of Circular type cofferdam are as follows: Each cell can be filled to the head independently before the construction of the second cell and in this way, the construction of the second cell is not distorted so the construction of the cell can be started from a different point. Each cell behaves as a self-supporting independent unit. Less steel per unit length is used in the construction of a circular cell compared to a diaphragm type cell. Cellular cofferdam is suitable for heights of 10 to 15 m. The diameter of the cell is kept from 10 to 15 m and the distance from the center to the center is kept from 12 to 18 m. The bottom of the river is hard rocky and the top layer of clay or silt is more suitable for such cofferdam. Different Types of Cellular cofferdam Diaphragm type cellular cofferdam In this type of cofferdam, steel sheet piles are attached to each other to form a series of arcs. Straight walls are attached to each other with the arc of sheet piles on both sides. Usually, the radius of the arch is kept equal to the distance between the two diaphragm walls. In order to create uniform tension between the diaphragm and the arch, building materials like sand, gravel etc. are filled in it after immersing the cell in water to the required depth. In all cells the filing of material should be done at the same rate up to the same height so as not to wrap the diaphragm. How cofferdam installed? On Cofferdam installation , On-site water is pumped into the two inner fill tubes causing the dam’s chambers to slowly and evenly inflate, forming a strong, stable cylindrical tube. As the inner tubes continue to fill and the water pressure builds, the dam unrolls in a controlled manner to create the strong and dependable Cofferdam. Cofferdam Video Cofferdam Requirements There are several basic requirements of any cofferdam. It must be watertight. A cofferdam must remain standing against the pressure of existing or added water (such as a flood). Existing water includes water at, above, or below the groundwater table. Cofferdam Materials Cofferdams can be made from several different materials, such as earth, rocks, timber, steel, and concrete. If possible, the selected material should be relatively easy to dismantle and recycle to reduce construction costs. Cofferdam Construction Process Most cofferdams are constructed using the following 12 general steps: 1. Pre-dredge and level the area for the cofferdam. 2. Drive temporary support piles. 3. Temporarily install a bracing frame on the support piles. 4. Install steel sheet piles. 5. Drive sheet piles to grade. 6. Block between bracing frame and sheets. Cofferdam Construction Process Most cofferdams are constructed using the following 12 general steps: 7. Tie sheet piles at the top. 8. Excavate, leaving the water inside the cofferdam. 9. Install internal bracing as the water is removed progressively from the cofferdam. 10. Drive piles as required. 11. Install rock fill. 12. Place tremie concrete seal. Cofferdam Construction Process Video Cofferdam Pressures An engineer determines the best type of cofferdam to use. It needs to be of a sufficient size to meet the project requirements in the most economical way possible. The engineer uses standard calculations based on known and anticipated forces including hydrostatic pressure, soil loads, water currents, waves, ice, as well as seismic and accidental loads. Emergency Response With workers and equipment inside of what is essentially a deep, dry, well, you need to have an emergency response plan in place. There are several potential risks when working inside a cofferdam. Obviously, a flood event causes the cofferdam to fill up with water. But rock fissures and shifting soil conditions – even vessel traffic – can create unsafe conditions within the cofferdam. Any emergency response plan should include dewatering backups that are regularly inspected. Cofferdam Removal The cofferdam is meant to be a temporary structure. But you can’t just pull it out, chuck it out, and be done with it. Removal of the cofferdam must be planned in advance. A critical consideration is the impact of cofferdam removal on the structure that was built. In some cases, the sheet piles are sheared off and the bottoms are left in place. This is to avoid damaging foundation soils that could in turn damage the new structure. What is the main purpose of cofferdam? Cofferdam is commonly used to facilitate the construction or repair of dams, piers and bridges. The aim of a cofferdam is to be as watertight as possible to create a dry area in which to complete the required building works, or at least to limit water ingress to a safe level that can be pumped away. A cofferdam is a temporary structure that provides a dedicated barrier against water intrusion. Many construction sites use cofferdams to create a temporary dam so they can get on with their project without having to work in water, or to make the construction project possible in the first place. Factors affecting selection of cofferdams construction Cofferdams can be of different types. But what kind of cofferdam to build in which place depends on the following things: The area to be protected by a cofferdam The depth of water to be dealt The state of water The overtopping possibility by floods tides etc. The characteristics of a bed on which the cofferdam is constructed. Is i.e. a pervious layer or an impervious layer. The velocity of flowing water. Factors affecting selection of cofferdams construction The availability of construction materials in the vicinity of the site of work. Transportation facilities are available. Increase inflow velocity due to obstruction of water flow from the construction of Cofferdam and the possibility of erosion of bottom Necessity of cofferdams The need of cofferdams construction arises in the following situations: Necessity of cofferdams When construction is to be done on the banks of a dry or watery river or between rivers Necessity of cofferdams When construction is to be done on the beach Necessity of cofferdams When construction is to be done on the middle of the lake or on the shore Necessity of cofferdams When deep excavation is to be done at a place of deep granular soil Necessity of cofferdams When deep excavation is to be done on clay soil Necessity of cofferdams When excavation is to be done below ground level Necessity of cofferdams When there is a possibility of landslides due to deep excavation Necessity of cofferdams When water is likely to seep into the excavation from the surrounding area Uses of cofferdams A cofferdam is used for the main purpose that provides a dry working area for workers. Cofferdams have lots of applications, it can be used either temporary of permanent. The following are the uses of cofferdam: To facilitate pile driving operations. To place grillage and raft foundations To construct foundations of piers and abutments of bridges, darns, locks, etc. To enclose a space for the removal of sunken vessels. To provide a working platform for the foundations of buildings when water is met with. To provide space for carrying out the foundation work without disturbing or damaging the adjoining structures such as buildings, sewers, pipelines, etc. What is the difference between cofferdam and caisson? A temporary structure which is removed after completion of the work. The aim of a cofferdam is to be as watertight as possible to create a dry area in which to carry out the required works, or at least to limit water ingress to a safe level that can be pumped away. built to remain in place as part of the completed structure. Typically, a box like structure made of materials such as timber, steel, masonry and r einforced concrete. It maybe constructed on shore then floated to the required location, where it is sunk into place, enabling access to the bed to undertake works. Projects that are using Cofferdam technology. La Mesa Dam Project: Status: Unknown/ no Document Available Scope: Pressure Relief Wells, Piezometer drilling and Curtain Grouting Location: Quezon City, Philippines Summary: The drilling of Pressure Relief and Piezometer holes inside and outside of a Cofferdam which was being constructed as the exit portal for a TBM (Tunnel Boring Machine) in La Mesa Dam. La Mesa Dam Project Video Projects that are using Cofferdam technology. Panguil Bay Bridge Project: Status: still on going Scope: Installs First Pre-Cast Substructure Foundation of Panguil Bay Bridge Location: 3.17-km inter-island bridge that will connect Tangub City and Tubod across Panguil Bay in Northern Mindanao. Summary: Undersecretary Sadain, explained that the prefabricated PC house will be the foundation for the two (2) pylons each with six (6) piles and piers 17 and 18 with four (4) piles each which are the substructure of the project’s main bridge or the highest segment where marine vessel such as ship could pass underneath. Waterproof sealing are ongoing to ensure the watertightness between pile and boxlike PC house as this will then filled inside with cast concrete to act as cofferdam or strong foundation to make them stable against various forces which are likely to act on the structure, Undersecretary Sadain reported. Panguil Bay Bridge Project The End and Thank You for Listening!! References https://www.designingbuildings.co.uk/wiki/Difference_between_cofferdams_and_caissons#:~:text= The%20main%20difference%20between%20the,part%20of%20the%20completed%20structure https://pilebuck.com/marine/cofferdams-101-history-applications-materials-types/ https://journal.com.ph/dpwh-installs-first-pre-cast-substructure-foundation-of-panguil-bay-bridge/ https://www.civilengineeringweb.com/2020/08/types-of-cofferdam.html https://damitdams.com/cofferdaminstallation/#:~:text=A%20Dam%2Dit%20Dams%20cofferdam,a%20strong%2C%20stable%20cylindrical% 20tube https://www.jfbrennan.com/blog/cofferdams-101-different-types-and-construction-methods-onwaterways#:~:text=Constructing%20a%20cellular%20cofferdam%20is,that%20prevents%20water%20fr om%20entering https://bundokdrilling.com/projects/la-mesa-dam
