Why are so many retaining walls failing this year?





10/19/2019



.This extremely wet year was disaster for many properties in the area. Along with general drainage issues, this year we took numerous calls about failing retaining walls. Retaining walls have the job of holding back soil on a slope that might otherwise erode during rainfalls. This is especially important on shoreline properties.


Signs of a retaining wall failing include leaning, cracking or bulging, all of which signal instability and possible future collapse. A failing wall will have to be rebuilt, but the first step is identifying the cause of failure. Below are some of the common causes of retaining wall failure.





Poor drainage

The number one cause of retaining wall issues is heavy saturated soils that put a strain on the wall if it is not designed to handle that increased weight. If a wall is installed without proper drainage and backfill to get the water out and away, it is doomed to fail, especially after heavy rain events.


Unanticipated changes

A retaining wall that is built properly should stand for fifty or a hundred years or more without showing signs of failure. However, changes to the land around it that affect pitch, drainage, or weight load can alter the pressure load on the wall. Retaining walls are designed for different weight loads depending on use. If you are changing the use of an area, like adding a parking pad, new structure, or regrading, an older retaining wall will most likely need to be rebuilt and strengthened.


Foundation issues

Just like any other vertical structure, retaining walls need a solid foundation to avoid shifting and eventual crack or collapse. Properly compaction and base material is crucial. Retaining wall base footing needs to be deep enough to resist the weight of saturated soils and also deeper than the frost line.


Poor design

There are different types of retaining wall, and there is a time and place for them all.


Gravity walls – Dry stacked boulder walls or segmented block walls hold back soil by the weight of the wall material. They gradually step back into the earth to provide more strength and longevity. They are easy to install and are have design flexibility. A compacted gravel base is laid down, and the base blocks are secured. The gravel base is stabilized with a geogrid soil reinforcement to be built to any height. They can fail easily if installed wrong or too small of material is used.


Anchored walls – The taller the wall, the more engineering is required for success. Arms, pilings, or anchors are installed deep back and under the hill to stabilize pressure on the wall. s before issues became apparent, but with the new normal of extreme weather coupled with the sloping landscapes of the southern lakes, walls are showing signs of failing within a year of install.


If you have a retaining wall that is not doing its job, give us a call, and we can build a bigger, better wall that is installed properly to stand the test of weather and time.