What is the typical feature of a mat/raft slab in relation to soil stress?

A mat or raft slab is designed to distribute the load of a structure over a large area of soil, which helps to mitigate the stress that is transmitted to the underlying soil layers. This feature is particularly important in situations where the soil has low bearing capacity, as it allows for a more even distribution of the weight of the building across the foundation.

By spreading the load over a wider area, the mat slab reduces the pressure on any one point in the soil, which can help to minimize settlements and provide a more stable foundation for the structure. This is essential in achieving structural integrity and preventing differential settlement, which can lead to issues like cracking or uneven settling of the building.

The other options touch on different aspects of structural design and foundation considerations but do not accurately describe the primary characteristic of a mat/raft slab. Instead, the goal of such slabs is fundamentally about load distribution rather than increasing stress, minimizing weight, or focusing loads. Thus, the ability of a mat/raft slab to distribute soil stress is key to its functionality in foundation engineering.