How do you evaluate foundation settlement and consolidation?

1 What is foundation settlement?

Foundation settlement is the downward movement of a foundation relative to its original position. It can be caused by various factors, such as applied loads, soil properties, groundwater fluctuations, or adjacent construction activities. Settlement can be uniform, differential, or angular, depending on the distribution and magnitude of the soil displacement. Foundation settlement can result in structural damage, such as cracks, tilts, or distortions, if it exceeds the allowable limits.

2 What is consolidation?

Consolidation is a type of settlement that occurs when a saturated soil undergoes compression due to an increase in effective stress. Effective stress is the difference between the total stress and the pore water pressure in the soil. As the soil compresses, the pore water is squeezed out and the soil particles rearrange themselves into a denser configuration. Consolidation can take a long time to complete, depending on the permeability and compressibility of the soil.

5 How to prevent or mitigate settlement and consolidation?

To prevent or mitigate settlement and consolidation, you need to design and construct the foundation and the structure with adequate safety factors and tolerances. You can also employ various techniques to improve the soil conditions and reduce the settlement and consolidation potential, such as preloading, drainage, grouting, and piling. Preloading involves applying a temporary load on the soil before the construction of the structure to induce consolidation and reduce the future settlement. Drainage requires installing vertical or horizontal drains in the soil to accelerate the consolidation process and reduce the pore water pressure. Grouting entails injecting cement or other materials into the soil to fill the voids and increase the strength and stiffness of the soil. Lastly, piling involves driving piles into the soil to transfer the load to a deeper and more stable layer of soil or rock.

6 How to monitor and maintain settlement and consolidation?

To monitor and maintain settlement and consolidation, you need to perform regular inspections and measurements of the foundation and the structure. You can use the data from the settlement gauges, plates, inclinometers, or tiltmeters to compare the actual settlement and consolidation with the predicted values and check for any signs of distress or failure. You can also use visual observations, crack meters, or level surveys to detect any structural defects or deformations. If you find any problems, you need to take corrective actions, such as repairing, reinforcing, or replacing the affected elements of the foundation or the structure.