Abstract: As an important storage facility for hazardous chemicals, the welded regions of liquefied hydrocarbon mounded storage tanks are prone to crack initiation under complex loads, threatening structural safety. Based on finite element simulation, this study established a crack‑containing model using a prototype of a 3500 m³ horizontal mounded storage tank from an actual project. Typical design loads were considered, including overburden soil pressure, head pressure, internal medium pressure, tank self‑weight, medium weight, and sand bed support. First, the similarities and differences between the elastic foundation model and the soil spring model in handling the sand bed support load were compared. Then, the stress distribution of the tank under a crack‑free condition was analyzed, identifying the circumferential welds of the shell and the fillet welds connecting the stiffening ring to the shell as the most critical regions. The effect of crack location on the stress intensity factor (SIF) at the crack tip was further investigated, and a safety assessment was conducted using the failure assessment diagram (FAD) technique. The results show that, for the same crack size, the weld toe of the stiffening ring fillet weld exhibits a higher failure risk. An increase in operating pressure raises the driving force for crack propagation and reduces the propagation resistance; therefore, overpressure operation should be avoided. The use of high‑strength materials significantly enhances the structural safety margin. This study provides a theoretical basis and a numerical tool for the safety assessment of defective mounded storage tanks.