عنوان مقاله [English]
نویسنده [English]چکیده [English]
Soil erosion and land subsidence in Iran have become famous and important issues. But recently, the vital arteries of urban and interurban areas across the nation's power line with secondary effects present various intense danger. In this research, the place of power line from Eshtehard to Bouin-Zahra area is studied from a sedimentology and erodibility point of view. Three types of soils are exposed in the area: 1-Aridisol soils 2-Antisol soils with rock outcrops 3-Playa saline soils. The types of erosion observed in the study area include surface, furrow, stream, and trench erosion on the Upper Red Formation deposits and Quaternary sediments of the plain. In this study, after a field visit to the Eshtehard area, surveying the route of power towers and observing the effect of marls on erosion, it was decided that in addition to the soils adjacent to the power towers, beside three different samples of marls in the area were sampled and tested. In the laboratory, granulation was determined by two methods of sieving and hydrometry, calcimetry, electrical conductivity, etherberg limits, and the amount and type of different elements and clay minerals of each sample. In Geoelectric studies, to understand how the deposition of sedimentary layers and subsurface cavities in the vicinity of towers, based on field visits and sedimentological studies due to limited financial resources, two lines or profiles for Geoelectric field operation in parallel and perpendicular to the transmission line selected in one of the critical areas. After the impressions, the data were processed and interpreted with IPI2WIN software, and after individual and point sampling, group processing was performed and Geoelectric quasi-sections and sections, deep electrical resistance gradient, a section of electrical conductivity changes, and statistical distribution of resistivity values were plotted and examined. The results show that the area is covered by highly erodible marl and contains abundant non-stick silt particles, alkali cations, and soluble anions belonging to the lower red and upper red formations. A silty layer about one meter thick is located on the surface substrate consisting of dense clay and on the clayey sand layer and due to high erosion, they cause large tunnels and gullies that go towards the electric towels. The clay mineral of this layer is Montmorillonite with highly sensitive to soil erosion factors. Geoelectric studies show this layer as well as sandy layers in 45m and more depths. In the Eshtehard area, the samples are in the range of CL, ML, and OL and (one case) OH and MH, from fine-grained soils which are a combination of silt and clay. Clay minerals in different marl units of Upper Red Formation, M1, and M2 are prone to erosion and disintegration of aggregates due to their expandable and swelling-sensitive Montmorillonite clay minerals. Also, the M3 unit has less erodibility than those two units due to its quartz and calcite, which are more resistant minerals. Sedimentological and Geoelectric studies in this study showed that they can help diagnose and separate phenomena and their causes in the two risks of erosion and land subsidence. The main reason for the general subsidence of this region can be considered as water extraction for the steel industry in the Eshtehard region, which has been used as a driving force to create cracks and erosive cracks in the soil. Geoelectric studies, in addition to showing the grain size of the soil and the location of subsurface cavities, have been able to prove the existence of a wet medium grained layer in the region.