Hydrostatic Pressure: What is it and Why is it Important for Retaining Walls?

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Hydrostatic Pressure: What is it and Why is it Important for Retaining Walls?

Hydrostatic Pressure:  What is it and Why is it Important for Retaining Walls?

The industrial revolution sparked the creation and construction of countless powerful machines, all of which display the brute force and capabilities of man-made technology. A crane can quickly lift cumbersome building materials hundreds of feet into the air, while a bulldozer can shift heavy rocks and rubble effortlessly.

We often forget that the most momentous forces that surround us are in fact not man made, but are actually produced from the natural elements of the earth. 2017 has brought the worst wildfire season that British Columbia has ever recorded, reminding us of the true power of Mother Nature.

As a contractor or a homeowner who is considering installing a retaining wall, these natural forces of nature must be taken into consideration. One of the most common reasons that a retaining wall will fail is due to poor drainage, which will cause a destructive force to build up known as hydrostatic pressure.

What is Hydrostatic Pressure?

When water sits and collects in one area, it will exert a force on the surrounding objects, which will build in intensity as the amount of water increases. One of the best examples of this force is the pressure felt in your ears when you swim to the bottom of a pool. If you have ever been scuba diving, this will be even more relevant to you. As the human body travels deeper under the water, the amount of hydrostatic pressure will increase, which is generally felt first against the eardrum.

For every 10 metres traveled deeper into an ocean or lake, an additional 6.47kg (14.27lbs) of hydrostatic pressure will be applied on each square inch of the body. A remote operated vehicle that travels to 2,000 metres below the surface in the ocean will be exposed to an astonishing 1,270kg (2,800lbs) of pure force on every inch of its hull.

What Does This Have to do With Retaining Walls?

To understand how hydrostatic pressure can effect a retaining wall, one must fully understand the function of such a wall. Typically, a retaining wall is a structure created from pre-cast or formed cement blocks that supports a mass of earth on one side in order to maintain two levels of elevation in one area.

The slope or vertical nature of a retaining wall can be used to generate more useful space in a backyard or to enhance the landscaping appeal of a property. Larger retaining walls are extremely useful when creating highway overpasses or when farming in mountainous areas.

The Natural Force of Water Cannot be Stopped

The near-vertical form of a retaining wall does not usually occur in a natural environment due to the amount of force or pressure that is created from such a slope. A retaining wall is designed and built to hold up all the rocks and dirt behind it, along with a small amount of natural moisture. When a large amount of water is added to the equation, perhaps from a considerable rainstorm or snowmelt, the force of the added water and dirt can topple a retaining wall over with ease.

The power of the collected water can also create massive cracks in pre-cast blocks due to the porous nature of concrete. Pre-cast blocks are filled with tiny capillary networks that form when the concrete is drying. These small pathways remain open once the block is dried, and if the hydrostatic pressure is high enough, water can push its way into a block through these tiny passages and weaken the entire structure.

How To Avoid Hydrostatic Pressure Damage

All the problems associated with hydrostatic pressure can be solved with one simple, magic word…Drainage. Without proper drainage built into a retaining wall system, it is only a matter of time before the wall starts to shift, or fails completely.

Achieving Drainage

A retaining wall is typically designed to hold the weight of the dry earth that is behind it, and not a large mass of saturated soil. This will never be an issue if the builder or contractor installs a simple drainage system that leads water away from the site of the wall, minimizing the hydrostatic pressure that is applied to the structure.

Effective drainage can be achieved with a system that includes a perforated pipe behind the wall (directs the flow of water away from the area), coupled with gravel (creates porosity near the wall) and fabric to separate the gravel from the soil.

Another useful tactic that will help keep the area around a retaining wall dry is the use of pre-cast blocks that are built with drainage in mind. At Can Ridge Industries
we offer the Verti-Block line of products that are designed with hollow cavities that allow for increased drainage, while also offering the benefit of being lighter and cost effective.

Pre-cast Blocks for Every Need

Whether you are building a retaining wall, or you are setting up a safety barrier on the highway, Can Ridge Industries has your pre-cast block needs covered. Aside from the Verti-Block lineup, we also have a large selection of Octa-Blocks that will fit any project you and your company come across.

For more information, give our sales and dispatch team a call today at (604) 341-2240 or email at info@canridge.com.