What Is Ground Heave In Civil Engineering?
What Is Ground Heave In Civil Engineering?
Ground heave is the upward movement of the ground usually associated with the expansion of clay soils which swell when wet. It is caused by a variety of factors, such as stress relief due to removal of soil or other above-ground structure, change in water table elevation, and trees that have died or been removed.
Common signs of ground heave include cracks in walls and floors, doors and windows sticking, and uneven floors.
Ground heave can be prevented by installing cellular structures beneath foundations and floor slabs to reduce the upward force of heave from transmitting to the structure above. Remedying damage due to ground heave can be a lengthy and expensive process.
Soil heaving is different from ground heave in that it is caused by borehole pressure, excavated depth, flow of drilling fluid, rate of back reaming, moisture content of soil and grout pressure. Negligible soil heave is acceptable but should not exceed 0.5 inches.
What Are The Signs Of Ground Heave?
Ground heave is often signalled by vertical cracks in walls and brickwork, sticking doors and windows, and the lifting of patios, driveways and paths surrounding the property.
If you think your building is affected by ground heave then a chartered surveyor or ground engineer should be contacted to carry out a survey to ascertain the cause.
In comparison to subsidence, which usually causes diagonal cracks, those caused by heave are generally vertical.
Ground Heave Causes
Ground heave is the upward movement of the ground usually associated with the expansion of clay soils which swell when wet.
Common causes of ground heave include trees which have died or been removed, changes in soil moisture due to weather fluctuations, and construction work or problems with buildings.
Signs of ground heave may include cracking to brickwork and windows that is more likely to be vertical than diagonal.
Prevention and remedying of ground heave can involve installing cellular structures beneath foundations and floor slabs, repairing leaking drains or removing trees, and addressing environmental conditions such as frost heave and chemical reactions.
The remedial costs associated with heave can be substantial, so it’s important to contact your local authority building control department to discuss how they can help.
The surveyor you appoint will carry out investigations such as visual inspections, historic research, drilling boreholes and trial holes to assess the soil plasticity and determine if ground heave is causing cracks or other structural damage.
Your local authority building control department should be able to provide advice on how best to tackle the issue and help alleviate any fears over the potential cost of repairs.
Ground Heave Prevention
Prevention of ground heave can be achieved by addressing the three conditions that lead to it: reducing frost penetration, keeping water away from the affected area and providing sufficient insulation. Keeping a watchful eye on vulnerable plants and filling low spots during preparation and clean up can help prevent frost heave.
Well-drained soil is also necessary to prevent pooling of water. Adding a layer of insulation underneath the concrete or asphalt can slow down the penetration of cold into the earth and help prevent frost heave.
Additionally, identifying and remedying the root cause of ground heave is essential for stopping it.
