# Forces acting on pipe submerged in drying cement

• robkm
In summary, the discussion is about the analysis of a hexagon pipe that is submerged in drying cement. The pipe is hollow with a thickness and is pointing upwards with a top point of about 100mm from the surface. Factors such as buoyancy forces and hydrostatic pressure are considered, as well as the potential for expansion and contraction due to temperature changes. It is noted that plastic pipes would not usually be affected, but precautions such as tying the pipe down to steel reinforcement may be necessary during the pouring process.
robkm
I need to analyse what's going on when a hexagon pipe is submerged in drying cement.

The pipe is hollow with a thickness and is hexagon shape, where the hexagon is pointing up. It is submerged in standard cement, where the top point of the hexagon is about 100mm from the suface.

I understand when the cement is poured in, buoyancy forces act on the pipe pushing it up. Hydrostatic pressure is also acting on the pipe, imncreasing with depth. is there anything else needed to be considered and how would you calculate the forces.

thanks for any feedback

Pretty sure there is negligible contratction during the curing process. Also with temperature change, the expansion and contraction coefficients of concrete are very similar to steel, and would not usually present a problem to plastic pipes. I have observed that copper pipes are usually wrapped in foam or fabric - but I think that is due to them often being used to convey hot liquids. If the pipe is tied down to say the steel reinforcment, it will not float upwards during the vibration process when the concrete is being poured.

There are a few other forces that should be considered when analyzing the situation of a hexagon pipe submerged in drying cement.

Firstly, there will be a shear force acting on the pipe due to the viscosity of the cement. As the cement dries and becomes more solid, it will create a resistance against the movement of the pipe, resulting in a shear force. This force will also increase with depth as the cement becomes denser.

Secondly, there may be a lateral force acting on the pipe due to the expansion of the cement as it dries. This expansion can cause the cement to push against the sides of the pipe, creating a lateral force.

To calculate these forces, you will need to consider the dimensions and properties of the pipe and the cement, as well as the depth of the pipe in the cement. This will involve using equations for buoyancy, hydrostatic pressure, shear force, and lateral force. It may also be helpful to consult with a structural engineer for a more thorough analysis.

Overall, it is important to consider all of these forces when analyzing the situation of a submerged pipe in drying cement to ensure the structural integrity of the pipe and the stability of the surrounding cement.

## 1. What types of forces act on a pipe submerged in drying cement?

There are primarily two types of forces that act on a pipe submerged in drying cement: buoyancy force and gravitational force. The buoyancy force is the upward force exerted by the surrounding cement on the pipe due to the displacement of the cement by the pipe. The gravitational force is the downward force exerted by the weight of the pipe and the cement above it.

## 2. How does the density of the cement affect the forces acting on the pipe?

The density of the cement plays a crucial role in determining the magnitude of the forces acting on the pipe. A higher density of cement would result in a greater buoyancy force and a stronger gravitational force. This can put more stress on the pipe and could potentially cause it to fail.

## 3. What other factors can influence the forces acting on the pipe in drying cement?

Apart from the density of the cement, other factors that can influence the forces acting on the pipe include the size and shape of the pipe, the depth of the cement, and the rate at which the cement is drying. A larger or irregularly shaped pipe would experience greater forces, and a deeper layer of cement would result in a higher buoyancy force.

## 4. How can these forces be managed to prevent damage to the pipe?

To prevent damage to the pipe, it is important to control the rate at which the cement is drying. This can be achieved by using additives in the cement or controlling the environment, such as temperature and humidity. Additionally, reinforcing the pipe with materials such as steel can help withstand the forces acting on it.

## 5. Are there any safety precautions that should be taken when working with pipes submerged in drying cement?

Yes, there are several safety precautions that should be taken when working with pipes submerged in drying cement. It is important to wear appropriate protective gear, such as gloves and goggles, to prevent any contact with the cement. The area should also be well-ventilated to avoid inhaling any harmful fumes. Additionally, it is crucial to follow proper handling and mixing instructions to ensure the integrity of the cement and prevent any accidents.

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