Clay is used in the domain of construction material since a long time. Several problems are related to clay behaviour in some temperature and relative humidity variations. For this reason, researchers are looking for improving the clay behaviour by stabilization using high temperature or by adding synthetic or natural fibers. In this work, two tests are conducted to notice the effect of rock gravel addition into a clayey soil. For each specimen crack pattern is observed and characterized using an image analysis technique. Also, some hydraulic parameters are quantified: water content, evaporation rate, saturation degree and porosity versus time. The main objective of the paper is to present a study on active clay strains generated by shrinkage and their consequences on building and civil structure. In the first part of the paper, the testing devices are described. Strains induced by desiccation conditions without external mechanical stress, are observed in two cases: soil specimen and reinforced specimen (with rock inclusion). The results showed that, under these conditions, vertical strain depends on the percentage of rock inclusion. As a conclusion, it could be stated that the settlement depends on the rock inclusion percentage during a desiccation process.
The phenomena, soil shrinkage-swelling cycles is characterized by small incremental land movements, caused by volume changes of some clay soils versus their moisture content changes. This hazard concerns only certain clay soils especially in the presence of swelling minerals (active material). Silts also exhibit shrinkage and swelling cycles as their water content fluctuates, but at a much smaller amplitude (lower activity of material). This phenomenon causes significant damage to buildings during periods of prolonged drought (Trabelsi 2014). In a temperate climate, clays are often close to their saturation state. Therefore, their swelling potential is relatively limited, so they are far from their withdrawal limit, which explains why the most important movements are observed in the dry period. The drought is reflected in a drop in the level of the aquifers. The most superficial slice of soil, 1 to 2 m deep, is then subjected to evaporation. The result is a shrinkage of the clays, which is manifested vertically by a settlement and horizontally by the opening of cracks, classically observed in the bottom of pools that dry up.