Several ground fissures have developed in the east and southeast of Semnan city, posing a serious threat to vital infrastructure, such as roads, railways, and pipelines. This study was undertaken to assess the mechanism of earth fissuring and to prepare hazard and risk maps as guidelines for decision-makers in environmental management. The research involved various stages, including a desk study, site investigation, laboratory tests, and engineering assessment of the results from the previous stages, leading to the preparation of maps. Laboratory test results indicated that most parts of the area are covered with silty soils, and their collapse potential (Ic) values varied from 15.4 to 27.4%, indicating a severe collapse potential. Results from Crumb, pinhole, and double hydrometer tests revealed that much of the collapsible loess also has a moderate dispersion potential. In conclusion, the presence of problematic soils with high erosion potential, coupled with the accumulation of surface water due to the construction of roads and railways with limited culverts, leads to tunnel erosion. This phenomenon is proposed as the main reason for earth fissuring in the area. The hazard map, based on the proposed model, identifies a heart-shaped area in the southeast of Semnan city with very high susceptibility to earth fissuring. The risk map categorizes four areas, including the region between the railway and gas pipeline to the east of Semnan city, the southern part of Semnan airport, Ala village, and the garrison to the south of the plain, as falling into the high-risk category, necessitating monitoring.
