Underwater Constructions | How do Engineers Make Them?

Many workers are fighting hard against violent ocean currents to complete the construction of an

underwater

bridge. Can you spot a mistake made by the chief construction engineer? This mistake will result in a catastrophe. Welcome to the most challenging task in civil engineering, even

underwater

construction. Although we call it underwater construction today,

engineers

avoid water completely when building an underwater structure to remove water from their construction area, they must first build a temporary dam called a casket dam, working directly underwater is far from be a practical method, the next question is What arises is how to construct the cofferdam underwater.

The first step is to erect these guide piles with the help of a pile driving hammer machine. The guide piles provide guidance for the construction of the cofferdam. Then workers will drive many sheet piles into the ground with the help of the same machine, these sheet piles have interlocking connections at both ends of the section. Such a clever interconnection mechanism means that water leakage will be minimal. Sheet piles are driven beneath the ocean floor until they reach bedrock. The stacking order is from the corner to the center, the alignment can be maintained in this way. Have you noticed anything special about the pile driving hammer machine?

It's not just about pushing the sheet piles down. You can easily imagine what would happen if the sheet piles were pushed inward. ground to penetrate the ground the machine uses vibration If you look carefully you will see these small but fast vibrations the specialty of this machine lies in the fact that it consists of two eccentric weights that rotate in opposite directions, the purpose of these weights is to induce vibration in a Machine, this flat-surfaced vessel called a barge, is used to transport machinery and components required on the construction site. Now we are ready for the big phase of the construction project, pumping the water out of the Coffer Dam, though, before we do all of this. work the

engineers

had an important task to do let's see what this was before moving on to the water pumping phase the project engineers had to do a detailed geotechnical study of the soil on which the cofferdam was going to be built they selected the land so that can withstand the load of the permanent structure, the most commonly used test to measure soil strength is an in situ test called the cone penetration test.

You can see how the cone penetration testing device stays on the ocean floor. The conical tip. of the device penetrates the soil and the sensors send back the friction and resistance values ​​of the soil and will continue the penetration until the point where they reach the bedrock. You can see the sudden jump in resistance value once bedrock is reached with the help of this handy Prove that engineers know how deep Sheet Piles should be driven. The sheet piles must reach the bedrock. Now let's go back to the project and start pumping water. As the water level drops, you will notice water leaking between the Sheet Piles.

This is because the water differential pressure single layer sheet piles are failing, so we need to double

them

. The space between these sheet pile walls is usually filled with granular material such as sand, gravel or broken rock. This double layer cofferdam will effectively resist water leakage between the sheets now let's remove all the water from the cofferdam fortunately there is no visible water leakage oh no what happened? the entire cofferdam collapsed inwards before when water was present on both sides, the force acting on the cofferdam due to the pressure of the water was cancelled, you can easily understand the reason for this;

However, when water of this volume disappears, there will be an enormous inward force that will destroy the Coffer Dam. Inward collapse of the sheet piles can be avoided by erecting a reinforcing frame structure next to the sheet piles. The reinforcing frame system comprises components such as whale struts and stays. The connection between these whales and the struts is bolted as illustrated here. These horizontal members called struts provide lateral support that can resist inward movement towards the walls of the Coffer Dam. The Coffer Dam is super strong now and has reached bedrock. Let's dry up the water now.

Can you predict what will happen? Here I have made a Dum chest, a small but cute Dum chest, isn't it? Now let's see what happens if I remove the water from the Coffer Dam. When you remove the water, did you see that there is a beautiful U shape? The water particles travel like a U shape under the chest downwards. This is due to the parallel differential of the water. The same thing will happen inside the cofam also when you remove the water from that similar to The water seepage experiment happens in our cofferdam and the technique to prevent water seepage is difficult to achieve so let's pump this seepage water continuously if it is removed the soil on the hard strata and concreting is carried out on the hard strata.

Our submarine project is halfway done. Once this is done, it is called concrete seal coat technique. The concrete sealing layer will also act as a strong base preventing any water leakage. Let's see how this is done. Removal of cofferdam soil is usually done using clam buckets. These buckets are operated by an excavator you don't see the operation of the clamshell bucket very well you know, the next stage is the concrete sealing layer to

make

sure that the concrete sealing layer is strongly bonded to the bedrock, we need some piles penetrating into the bedrock, the vibrating hammer machine comes to help again, it pushes some hollow steel tubes into the bedrock, the hard rock inside this cylinder is removed with the help of augur machine.

Now it's time to place rebar in the cavity and pour concrete. Once the piles are ready, we can build the Concrete Sealing Layer above as there is seepage water present in this foundation. Always concreting the sealing layer is carried out using the test method. This includes a hopper bucket and a long segmented tube. Specialized cement with high workability is used to concrete the floor. A thick plug is installed. at the bottom of the test pipe to prevent water from entering inside the pipe after some time, this pipe is lifted with a pull, which causes the concrete to spill out and the bottom plug is removed during this process, the The discharge end of the test pipe is kept continuously submerged in the concrete so that the net being poured is less likely to mix with the surrounding seepage water.

Now that the concrete seal coat is ready, it's time to tackle the remaining construction work. This structure efficiently blocks water seepage. the skeleton of high quality reinforced bars to build the base shaft of the bridge pier because the structure of the bridge pier will remain in the water Engineers ensure that the materials to be used in the construction are of the best quality must achieve successfully withstand the water pressure and load of the bridge as the bridge skeleton. The dock continues to move forward. Arrangements are made to pour concrete into the structure. Once the concrete has been completely poured into the skeleton, this structure is kept undisturbed to gain strength.

Usually a bridge. The pier takes 14 to 28 days to gain full strength. Once the bridge pier gains enough strength, the cofferdam is useless and hurts the eyes, so engineers remove it; However, removing the cofferdam below the level of the concrete sealing layer may affect the strength of the As a result, the entire structure was cut by engineers at this level. Here is this strong bridge. The pier is ready to support a heavy bridge. I hope you enjoyed the video on underwater construction technology using cofferdams, but this is a different type of underwater construction technology. known as Ken and that is again different called Pile Foundation.

We will cover these technologies in a different video, but before you leave this video, consider supporting us on Patreon, that will

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a difference. Thank you, take care, goodbye.