What is Subsidence and What Causes It?

Subsidence is something that anybody in the piling or construction industry needs to know about! Subsidence is the process of the earth sinking at ground level due to a number of factors in the soil underneath. Subsidence can occur due to a wide variety of reasons, ranging from extraction of natural resources to the reduction of groundwater. Subsidence can cause foundations to become uneven, which in turn causes the buildings atop those foundations to slant, warp, or even crack. Let’s take a closer look at some of these causes of subsidence.

Loss of ground water

Subsidence occurs due to the movement of soil or earth underneath a building. During droughts or prolonged dry spells, soil shrinkage occurs, leaving the building with less support and the piles with less reinforcement. Soils with a high clay content are particularly vulnerable to subsidence from soil shrinkage as clay is porous and absorbs lots of water when wet, so when it dries out it shrinks significantly! Loss of ground water can also be caused by tree roots nearby soaking up moisture from the earth, these are most often oak, elm, or ash trees.

Washing away of earth

Ironically, subsidence can be caused by too much moisture as much as it can be caused by not enough. If flooding occurs due to a heavy wet season or an event like a river bursting its banks, the subsequent oversaturation of soil combined with the heavy flow of water can wash away soil from underneath and around your foundations, weakening them and increasing the risk of subsidence. This can even occur due to leaky pipes or drains directing water underneath the property!

Extraction of natural resources

The industrial extraction of natural resources underneath buildings can cause subsidence through a number of ways. High-pressure extractions like hydraulic fracking involve blasting sand, water, and chemicals into the earth to release shale gas. In doing so, the high pressures can cause the earth to shift and weaken. Traditional mining can also make an area more vulnerable to subsidence as the progressive hollowing of the earth reduces its ability to bear the weight above.

Here at Rhino Piling, we have over 100 years’ collective experience, so we have all the expertise you need to deal with any piling project or subsidence repair! Get in touch today for a full evaluation carried out on-site!