Expansion of Compacted Gravelly Clay

The primary factors governing the expansion of a compacted clayey soil are the amount and activity of the clay particles. In many cases, the compacted soil may contain gravel-sized particles that, by themselves, will not expand in the presence of water. For swell tests on gravelly clay at a constant matrix dry density, normalized swell data are plotted near the volume relationship. This indicated that the swell behavior of the compacted gravelly clay was based solely on a reduction in volume caused by the presence of gravel. For swell tests on gravelly clay at a constant compactive effort, the normalized swell data approached the weight relationship. The gravel particles interfered with compaction, which caused a lower dry density of the soil matrix as the gravel content increased. When predicting the percentage of swell of a gravelly clay, the results of this study indicate that swell depends on whether the soil is compacted to a constant matrix dry density, or whether it is compacted by a constant compactive effort.