Investigating the Development of Kerman’s Soil Structure and its Effect on the Collapsibility index

Kerman and its surrounding towns consist of a flat alluvial plain of fine silt and clay materials. In morphological aspects, these sediments have a very gentle slope with the main infrastructure of the city build on them. Generally, the structure of undisturbed soils is developed over time due to the influence of environmental factors. Geological factors in Kerman fine-grained alluviums have caused the formation of some structures after their deposition. In this research, in order to investigate soil structure and determine the collapsibility index, 40 samples were collected from different parts of the city. Next, the engineering properties of Kerman’s soil (e.g., mineralogy and collapsibility), development of soil structure, and the sensitivity of soil structure were studied. To determine sensitivity and structural coefficient of these soils, Schmertmann’s criteria (1969) and Liu and Carter’s model (2000) were applied, respectively. Moreover, scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) method were used to study Kerman deposits. Mineralogy results of Kerman plain soils reveal that there are minerals such as illite, chlorite, smectite, and calcite in these deposits. The SEM images confirmed the consolidated and compressed structure of soil grains in most of the samples. Furthermore, other results show that soils of Kerman are often compressed and over-consolidated. Collapsibility index shows a quite direct relationship with structure development, as collapsibility is low in the samples with low destructuring coefficient while it is high in the samples that have a structure.