Heave is a term used in civil engineering to describe the upward movement of soil or other materials beneath a structure. It is the opposite of settlement, which refers to the downward movement of soil. Heave can be caused by a variety of factors and can cause significant damage to structures if not properly addressed.
One of the primary causes of heave is changes in moisture content. When the soil beneath a structure becomes saturated with water, it can expand and push the structure upward. This is particularly common in areas with high groundwater levels or in places where the soil contains expansive clay minerals. In such cases, the soil can heave significantly during periods of heavy rain or when the soil is irrigated.
Another cause of heave is the freezing and thawing of the soil. When water in the soil freezes, it expands, causing the soil to heave. When the ice melts, the soil settles back down. This process can repeat itself multiple times, causing damage to foundations, walls, and other structural components.
Human activity can also cause heave. For example, if a structure is built on top of loose fill or other poorly compacted soil, the weight of the structure can cause the soil to compact and settle, creating voids beneath the foundation. If the voids become filled with water, they can cause the soil to heave, damaging the structure.
Heave can cause several problems for structures. It can create cracks in foundations, walls, and floors, causing the structure to become unstable and unsafe for occupancy. It can also cause doors and windows to become difficult to open and close.
Preventing heave requires proper site preparation and construction techniques. For example, a vapour barrier can be installed beneath the foundation to prevent moisture from entering the soil. Drainage systems can also be installed to direct water away from the structure. Proper compaction of the soil beneath the foundation can also help prevent heave.
If heave occurs, remedial measures can be taken to repair the damage and prevent further movement of the soil. For example, the foundation can be jacked up and the voids beneath it filled with a stable material such as gravel. In extreme cases, the entire structure may need to be lifted and the soil beneath it excavated and replaced.
Heave is an important consideration in civil engineering. Understanding the causes of heave and taking steps to prevent it during construction can help protect structures from damage. If heave does occur, remedial measures can be taken to repair the damage and prevent further movement of the soil.