To construct the coffer dam, guide piles are first erected using a pile driving hammer machine, followed by the driving of sheet piles with interlocking connections into the ocean bed until they reach the bedrock. Once the water is pumped out, a geotechnical study is conducted, and the sheet piles are driven to the bedrock. However, when the water is completely removed, the coffer dam collapses due to water pressure, and this phenomenon is prevented by erecting a bracing frame structure by the side of the sheet piles. To prevent water seepage, a concrete seal course technique is employed, which involves removing soil above the hard strata and adding a seal course on the hard strata using the try method. The bridge pier, designed to support the bridge while remaining underwater, is then assembled using high-quality reinforced bars and poured concrete. The entire process takes time, and the coffer dam is removed once the bridge pier is complete. Different underwater construction technologies, including pile foundations, will be discussed in a future video
00:00:00 In this section of the "Underwater Constructions | How do Engineers Make Them?" YouTube video, the construction of an underwater bridge pier is underway, but the challenge of building a coffer dam underwater arises. To construct the coffer dam, engineers first erect guide piles using a pile driving hammer machine, followed by the driving of sheet piles with interlocking connections. The sheet piles are driven under the ocean bed till they reach the bedrock, and the pile driving hammer machine uses vibrations instead of just pushing the sheet piles down. Once the water is pumped out of the coffer dam, engineers conduct a geotechnical study of the soil to determine the load carrying capacity and drive the sheet piles to the bedrock. However, when the water is completely removed, the coffer dam collapses due to the inward force of the water pressure, and this phenomenon can be prevented by erecting a bracing frame structure by the side of the sheet piles
- 00:05:00 In this section of the video titled "Underwater Constructions | How do Engineers Make Them?", the engineer explains the process of creating an underwater project using a Coffer Dam as an example. When the water is removed from the dam, a U-shaped pattern forms due to the water paral squadential. To prevent water seepage, the concrete seal course technique is employed, which involves removing soil above the hard strata and adding a seal course on the hard strata. The soil is removed using clamshell buckets, and hollow steel piles are then added to the Bedrock. Reinforcement bars and concrete are placed in the cavity, and the concrete seal course is created using the try method to ensure a strong bond with the Bedrock. The water seepage is efficiently blocked once the concrete seal course is ready, and the remaining construction work, including the bridge pier, begins. Due to the importance of the Coffer dam in the construction process, engineers cannot remove it once the concrete seal course is in place, but they can cut the sheet piles at the appropriate level to avoid affecting the structure's strength. The bridge pier, which is designed to support the bridge while remaining underwater, is then assembled using high-quality reinforced bars and poured concrete. The entire process takes time for the structure to gain strength, and the Coffer dam is removed once the bridge pier is complete. The engineer also mentions that in a future video, they will discuss different underwater construction technologies, including pile Foundations
