How can you predict foundation settlement?

1 Soil investigation

Before designing and constructing a foundation, you need to conduct a soil investigation to determine the type, layering, strength, and compressibility of the soil. You can use various techniques, such as boreholes, cone penetration tests, standard penetration tests, and laboratory tests, to collect and analyze soil samples. The soil investigation will help you estimate the initial and final settlement of the foundation, as well as the differential settlement between different parts of the structure.

2 Foundation design

Based on the soil investigation results, you can choose the most suitable type and size of foundation for your structure. There are different types of foundations, such as shallow foundations, deep foundations, pile foundations, raft foundations, and mat foundations, each with its own advantages and disadvantages. You need to consider factors such as the load-bearing capacity, the depth of the water table, the presence of expansive or collapsible soils, and the potential for liquefaction or erosion. You also need to design the foundation to minimize the differential settlement and ensure an adequate factor of safety.

3 Settlement analysis

Once you have designed the foundation, you need to perform a settlement analysis to predict how much and how fast the foundation will settle under the applied loads. You can use various methods, such as empirical formulas, elastic theory, consolidation theory, and numerical models, to calculate the settlement. You need to account for the immediate settlement, which occurs due to the elastic deformation of the soil, and the consolidation settlement, which occurs due to the expulsion of water from the soil. You also need to consider the effects of creep, swelling, shrinkage, and time-dependent factors on the settlement.

4 Settlement monitoring

After constructing the foundation, you need to monitor the actual settlement of the structure and compare it with the predicted settlement. You can use various instruments, such as settlement plates, settlement gauges, inclinometers, extensometers, and optical leveling, to measure the settlement. You need to monitor the settlement regularly and record the data. You also need to check for any signs of distress or damage in the structure, such as cracks, tilts, or misalignments. If the settlement exceeds the allowable limit or causes structural instability, you need to take corrective actions, such as underpinning, grouting, or soil improvement.

5 Settlement prevention

The best way to predict foundation settlement is to prevent it from happening in the first place. You can do this by improving the soil conditions, reducing the applied loads, or increasing the stiffness of the structure. You can use various techniques, such as compaction, drainage, stabilization, reinforcement, or preloading, to improve the soil conditions. You can also reduce the applied loads by using lightweight materials, removing excess soil or water, or redistributing the loads. You can also increase the stiffness of the structure by using rigid frames, beams, or slabs, or by adding braces or ties.

6 Settlement prediction

Predicting foundation settlement is not an exact science, but a complex and uncertain process that involves many variables and assumptions. You need to use your engineering judgment, experience, and knowledge to estimate the settlement and evaluate the risks. You also need to update your predictions as you collect more data and observe the behavior of the structure. By following these tips and methods, you can predict foundation settlement more accurately and confidently, and ensure the safety and performance of your structure.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?