What Is a Reconsolidation Curve in Soil?

Soil Consolidation

• During the building planning stages, a building’s land location will act as the foundation needed to support its weight and hold its structural form intact. When first erected, a building’s weight causes the soil to consolidate, or compact. Depending on the type of soil, a building’s weight may continue to consolidate, or reconsolidate, the soil over time. Also known as primary and secondary consolidation, these two processes become factors when planning a building construction project. Consolidation and reconsolidation can factor into any building construction project in terms of new home constructions or home additions.

Reconsolidation Curve

• A reconsolidation curve measures the amount and rate of consolidation that takes place after an area of soil takes on additional weight. The curve combines two variables -- amount of consolidation and length of time -- to determine the effects a building will have on a soil environment. To do this, geotechnical engineers perform soil consolidation tests that measure a soil’s ability to withstand different degrees of pressure. In effect, reconsolidation effects become a time-dependent process that’s plotted as a curve on a graph. The information gathered allows builders to determine how long a building will settle and how far down the final building structure will sink.

Soil Processes

• Reconsolidation effects result from the removal of water from the soil. As a soil environment takes on additional weight, any existing water is squeezed out of the soil. When this happens, the overall volume of soil decreases as soil particles settle or compact. Soil particle size has a bearing on how much water exists and how water exits the soil. In effect, samples taken from coarse-grained or sandy soils will show a steep reconsolidation curve, since large sandy soil particles compress more quickly than smaller, fine-grained soils. Smaller, fine-grained soil particles such as clay have a slow reconsolidation rate, meaning water exits the soil more slowly.

Soil Compaction

• Soil compaction involves the actual tamping down of soil layers to remove air pockets in the soil. Houses or buildings constructed on uneven land areas, such as hillsides, may have large amounts of air within the soil environment. Soil compaction works to consolidate soil layers and create a stable foundation for a building’s weight. Soil compaction activities occur before reconsolidation measurements are done, since compaction may require moving whole layers of soil to level out an area. As with soil-water consolidation, the amount of air present in a soil environment varies with the size and texture of its soil particles.