How to Reinforce a Shipping Container for Underground Use

JANUARY 25, 2021 BY RYAN STOLTZ

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Thanks to their modular structure, high-strength corrugated steel body, and ease-of-portability, shipping containers can be used immediately upon delivery and without modifications.

That said, there are certain situations that do require changes to container structures, particularly when it comes to underground use. If you plan on burying a shipping container to create an underground bunker, you'll need to make several design modifications to preserve its structural integrity.

Keep reading to learn how to reinforce a shipping container for underground use.

 

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What Are the Challenges of Using Shipping Containers Underground?

Shipping containers have corner frames that carry most of their weight. When you bury them underground, the container will face tremendous pressure from all sides. Though the corners might stay intact, the walls may buckle under intense ground pressure.  

To prevent this collapse from taking place, we must add extra supports to the container’s metal walls. 

 
Ways of Reinforcing Your Container

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Reinforcement is not only essential for containers buried underground, but may be necessary when applying other modifications that can weaken the container.

The way in which you approach this process will vary depending on your application. For instance, the reinforcement for a storm shelter and a container home will differ considerably.

Let’s first take a look at traditional reinforcement methods for aboveground structures.


Reinforcing Shipping Container Homes

Cutting out openings for windows or ventilation can reduce the structural strength of the entire container. Therefore, you must follow certain steps to ensure the living space maintains adequate support after making modifications. 

Note: You'll need strong steel bars, steel plates, welding equipment, and cutters.

  • Cut steel bars in size slightly more than the width and height of the window
  • Use the steel plates to make 'posts.'(Posts are where you'll weld the steel beams)
  • Weld two posts at the top and bottom end of the window opening.
  • Pin the steel bar to these posts and solder the connection.
  • Repeat the process for the left and right ends. Your support will look like the (+) sign.
  • Add more support beams, if necessary.

 
Reinforcing Shipping Container Bunkers

Building a bunker is a laborious process. There are four steps you must follow for a properly reinforced bunker. To begin, you'll need strong steel bars, welding equipment, copper braising, copper/stainless steel mesh.


Step 1: Bury the Shipping Container Upside Down

The base of standard shipping containers is thicker than the roof. Remember, you want the floor to bear the maximum weight. Burying the container in a reverse direction will ensure it has adequate strength at the top to take the weight of the soil layer.

Step 2: Reinforce the Roof

With your roof now the base of your underground bunker, it is vulnerable to ground pressure. Weld steel bars across the roof surface. Cover the base with a wooden floor or concrete if necessary.

Step 3: Reinforce the Side Walls

We know now that corrugated steel walls are the weakest members of the container. You'll need horizontal and vertical beams for structural support in the middle of the wall. Weld steel beams at either end of your container walls for additional strength.

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You now have a reinforced shipping container that won't cave in due to surrounding ground pressure.

Step 4: Make Your Container EMP Proof

Reinforcing your container provides sufficient protection against ground pressure, but there are remaining factors that can damage your container.

For instance, most people build underground shelters and bunkers to protect themselves from destructive weapons and electromagnetic pulses (EMP) blasts in the event of a nuclear attack. While the ground layer can absorb the pulses to a certain extent, you’ll need to protect your electronic goods, such as remote power generators. 

The best way to protect your container from an EMP attack is by building a “Faraday Cage” or an enclosed space with adequate shielding.

Use microwaves, metal trash cans with sealed lids, or ammunition boxes to store the electronics you want to protect.

Use a stainless steel/copper mesh wall to seal your door. You can also use copper braiding to plug your door or solder the door permanently. Ensure that the cage you've built is away from the container walls.

Insulate the floor of the container with thick carpets and rugs. Use grounding to ensure that pulses flow from the shipping container with the least resistance.

When you bury a shipping container, there's also the risk of faster corrosion due to the salts and chemicals present in the soil. Therefore, you must invest in proper corrosion prevention techniques like Cathodic Protection to increase the lifespan of your shipping container.


Things to Remember

While the corner posts have sufficient strength to stack two containers on the ground surface, the situation below the ground level is entirely different. Burying a shipping container is generally not recommended as corrugated steel walls of the container can cave in easily.

Before you reinforce your buried shipping container, these are some of the things you should consider:

  • Consult a structural engineer to check if your design provides adequate structural support.
  • Build an emergency escape hatch in case your containers fail underground.
  • Do not place electronics close to the walls of the container.
  • Ensure adequate ventilation and air supply in your container
  • Use a remote power source such as a diesel generator to electrify your container
     

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With so many considerations to keep in mind, some may question whether it's worth burying a container in the first place.

The answer is simple. If you don't have a choice, you can use containers for underground use, provided your bunker has sufficient structural support. Alternatively, you can build a permanent bunker for higher strength and long life.


Conclusion

Building an underground shelter using shipping containers can be complicated. You need to consider the container's structural integrity and modify the design to ensure that your container does not buckle due to intense ground pressure. Steel reinforcements are the best option when using shipping containers underground.

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FAQs

Can You Bury a Shipping Container Underground?

Although you can bury shipping containers underground, you need to ensure adequate structural support to the container. If you do not reinforce your container, the walls may cave in due to intense ground pressure from all sides.


How Deep Can You Bury a Shipping Container?

A steel storage container can buckle with as little as 18 inches of soil over the top surface. Therefore, you cannot directly bury a container below 18 inches without reinforcements. Modifying the container walls can help you increase the depth in which you can bury your structure. 


How Do You Strengthen a Shipping Container?

Shipping containers are robust at the corners, with little strength at the walls. Therefore, to strengthen your containers, you must add strong steel beams along the periphery for imparting more strength.


Can a Shipping Container Withstand Being Buried? 

As containers have weak walls, they may fail when buried underground due to intense ground pressure.  Therefore, you must consider the complications, challenges, and risks before burying a container.

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