What are the most effective ways to manage settlement during foundation design projects?

2 Foundation selection

Based on the soil investigation results and the structural requirements, you need to choose the best foundation type for your project. There are two main types of foundations: shallow and deep. Shallow foundations are placed near the ground surface and transfer the load to the soil by bearing. Deep foundations are embedded deeper into the ground and transfer the load to the soil by friction or end bearing. Generally, shallow foundations are more prone to settlement than deep foundations, but they are also cheaper and easier to construct. You need to weigh the advantages and disadvantages of each foundation type and consider factors such as load magnitude, soil conditions, groundwater level, and site constraints.

3 Settlement analysis

Once you have selected the foundation type, you need to perform a settlement analysis to calculate the expected settlement of the foundation under the applied load. You can use various methods of settlement analysis, such as empirical formulas, elastic theory, consolidation theory, and numerical methods, depending on the complexity and accuracy of the problem. You need to consider both immediate and long-term settlement, as well as differential settlement, which is the uneven settlement of different parts of the structure. You also need to check the settlement criteria, which are the maximum allowable settlement values for different types of structures and serviceability conditions.

4 Settlement mitigation

If the settlement analysis reveals that the expected settlement surpasses the settlement criteria, you must take steps to reduce its impact on the structure. This can be achieved by improving the soil properties through compaction, grouting, or reinforcement. Alternatively, you can increase the foundation size, depth, or stiffness with piles, rafts, or mats. Additionally, you can reduce the applied load by utilizing lightweight materials or structural optimization. Lastly, providing flexibility or tolerance in the structure through joints, hinges, or sliding bearings is another option.

5 Settlement monitoring

Once the foundation design and construction is complete, you need to monitor the actual settlement of the foundation and compare it with the predicted settlement. You can use settlement plates, which are metal plates attached to the foundation and measured by surveying, or inclinometers, which are devices inserted into boreholes and measure the deviation of the soil from the vertical. Additionally, extensometers, which are devices installed in the soil and measure the change in length or strain, and piezometers, which are devices installed in the soil and measure the pore water pressure, can be used for monitoring settlement. This allows you to detect any unexpected or excessive settlement, identify its causes and effects, and take corrective actions if necessary.

6 Settlement communication

Finally, you need to communicate the settlement information and results to the relevant stakeholders, such as the client, the contractor, the architect, and the authorities. You need to explain the settlement assumptions, methods, and outcomes clearly and concisely, and provide evidence and documentation to support your design decisions and recommendations. You also need to address any questions, concerns, or feedback from the stakeholders, and resolve any disputes or conflicts that may arise due to settlement issues.