Foundation Settlement Due to Consolidation of Compacted Fill

In many practical purposes foundation engineer uses fill to raise the plinth level and for many other reasons. This fill is compacted to desired percent compaction to have better bearing stratum for founding building structures. Now in this post we will discuss about settlement generated by consolidation of compacted fill.

We all know that compacted fill usually undergo some degree of subsidence. This is due to readjustment of grains due to self-weight. There have two forms of settlement. One is settlement of underlying soil on which the compacted fill rests. Another settlement is due to settlement of compacted fill itself. The settlement of underlying soil will not discuss in this post.

We will now learn about the factors that controls the settlement process:

a. Type of soil particles and particle packing; in one word soil fabric. The soil fabrics in relation to compaction effort.

b. The amount of water used during compaction process and future changes from provided moisture content.

c. The height of fill (i.e. self weight from thickness of fill) and superimposed load from foundations or from any other surcharges.

Depending of depth of fill and above factors the fill may settle from 60 mm to 500mm and even more.

The settlement of compacted fill due to consolidation involves future mass saturation and can take a time of the order of several years. Geotechnical engineers may predict such types of consolidation in laboratory. Soil sample to filled is compacted to required moisture content and field density and put under consolidation testing device to test primary compression and secondary compression and swelling properties as well.