Introduction:
A raft foundation is a type of foundation that is typically used when the soil is highly compressible or when there is a high settlement under individual footings. In this response, we will discuss why raft foundations are a better solution for these types of soil conditions.

Highly Compressible Soil:
When the soil is highly compressible, it means that it can easily be compressed or compacted under the weight of the structure. This can cause the foundation to sink or settle unevenly, which can lead to structural damage. A raft foundation is a better solution for highly compressible soil because it spreads the load of the structure over a larger area, reducing the pressure on the soil. This results in less settlement and a more stable foundation.

High Settlement under Individual Footing:
When there is high settlement under individual footings, it means that the soil is not able to support the weight of the structure evenly. This can cause the foundation to sink or settle unevenly, which can also lead to structural damage. A raft foundation is a better solution for high settlement under individual footings because it spreads the load of the structure over a larger area. This reduces the pressure on the soil and ensures that the weight of the structure is evenly distributed, resulting in less settlement and a more stable foundation.

Conclusion:
In conclusion, a raft foundation is a better solution for both highly compressible soil and high settlement under individual footings. By spreading the load of the structure over a larger area, a raft foundation reduces the pressure on the soil and ensures that the weight of the structure is evenly distributed. This results in less settlement and a more stable foundation.