Definition:It is the ratio of the volume or weight of overburden (OB) removed to the volume or weight of ore or coal extracted in a surface mine. SR=OB Removed (M³)/Ore or Coal Extracted (Tonnes) • A lower SR means more economical mining; a higher SR increases cost. 🔸Types of the SR: 1.Overall Stripping Ratio(OSR): It is the total quantity of OB removed divided by the total quantity of Ore/Coal mined during entire life of mine,Used for long-term planning. OSR=Total OB removed÷Total ore/coal mined during the mine’s life 2.Instantaneous or Bench SR (ISR or BSR): It is the ratio for a specific portion or bench of the mine,not the entire life,Used for short-term planning & assessing local variations in mine geometry. 3.Break-Even Stripping Ratio (BESR): It represents the max SR at which mining remains economically viable.Beyond this ratio,the cost of removing OB equals or exceeds the value of the ore (No Profit=No Loss). BESR=Value of Ore-Cost of Ore Mining/Cost of OB Removal 🔸Factors Affecting the SR: 1.Depth of Ore Body: Deeper deposits→ higher SR. 2.Thickness of Seam: Thicker seams→lower SR. 3.Dip of Seam: Steeper dips→higher SR. 4.Nature of OB: Hard/compact OB→increases SR cost. 5.Ore Body Shape & Continuity: Irregular or faulted ore→higher SR. 6.Mining Method & Equipment: Efficient,high-capacity machines→lower SR. 7.Haulage Distance: Longer haul→increases SR cost. 8. Market Price of Ore/Coal: Higher price allows higher SR to remain economic. 9.Cost of OB Removal: Higher removal cost→lower acceptable SR. 10.Groundwater & Drainage: Poor drainage→more OB handling→higher SR. 11.Mine Planning & Scheduling: Proper planning reduces SR;early stages often have higher SR. 🔸Need for Determining SR: Determining the SR is essential because it helps in: 1.Economic Feasibility: To know if mining is profitable or not. 2.Mine Planning & Design:Helps determine the Ultimate Pit Limit (UPL),pit depth & layout,selecting the most suitable mining method and equipment capacity. 3.Production Scheduling: Guides annual stripping and ore production targets.Helps maintain a balance between OB removal and ore extraction. 4.Cost Estimation and Budgeting: SR provides the basis for estimating OB handling costs,unit cost of production and preparing project budgets. 5.Environmental and Safety Compliance: Determines the volume of waste to be handled,dumbed & backfilled.Affects slope design,reclamation planning & stability analysis. 6.Decision on Cut-off Grade and Pit Limit: Helps establish the BESR & Final boundaries of the pit (i.e.UPL). 7. Equipment & Resource Planning: Used to select suitable machine & manpower requirements based on waste-to-ore ratio. •1.5:1 – Manual quarrying •2:1 – Semi-mechanized quarrying •3 to 4:1 – Bucket Wheel excavator •4 to 5:1 – Shovel-Dumper combination •8 to 10:1 – Dragline method The SR is a key economic indicator that determines the feasibility, profitability, mine design, pit depth & life of a mining project.