Cut & fill mining method
- 1. Group Members Mst. Rajia Khatun(150819) Md. Jarjis Rahman(150828) Md. Sohanur Rahman(140820) Tanvir Ahmed Tanin(******)
- 2. Underground Mining Method Cut and Fill Method
- 3. Introduction As the name suggests, in this method the ore body is cut in slices and a fill of some kind replaces the void so created. During this operation the unit operations are carried out in a cyclic order i.e. drilling, blasting, mucking, transporting and filling. Cut and fill stoping can be applied for not only the thin and steep ore bodies with weaker walls but also for the wider and even weaker ore bodies than those suitable for the stull stoping. In fact, this method can be applied where the deposit cannot be mined by any of the open stoping methods, or in simple words, where open stoping fails, the substitute is the cut and fills stoping.
- 4. Types Of Cut & Fill Mining There are two types of cut and fill mining methods based on ore excavation directions; overhand method and underhand method. Overhand cut and fill mining Underhand cut and fill mining
- 5. Cut And Fill Mining Underhand Method Underhand method is the method to extract the ore deposit from the top downwards. The ore is drilled from the shallow level and continue by mining the deep deposits along the stope. This method enables us to obtain the ore product from the earlier stage. Overhand Method Overhand is a method to extract the ore from bottom upwards. Intact vein is hanging over the stope and the lower void is filled with waste materials. The advantage of this method is location of backfill under the working area enable the use of backfill material with relatively low strength to reduce mining costs.
- 6. Ore Strength: Moderate to Weak. Rock Strength: Weak Deposit Shape: Any, regular to irregular Deposit Dip: Usually steep but can be applied for flat dips also than it will be similar to longwall mining. Size and Thickness: fairly large extent, thin to thick (2-30 m). Ore grade: High but uniformity can be variable. Depth: Practiced up to 2.5 km. Conditions
- 7. Stope Preparation Access from the main level to the stope by a drive or crosscut (at both the levels) Connecting the two levels by service raises at a proper interval for mine services including ventilation and conveyance of the filling material. Development for the extraction layout includes driving the extraction drive, and construction of chutes for the ore passes. If the stope is mined overhand, development commences at the sill and progress upward with mining the ore slices. The ore and man passes are built simultaneously using timber or tubing as the stope advances upward. To have an access to mobile equipment such as drill jumbos, LHDs etc., a ramp sometimes becomes necessary; otherwise, maintenance of such sets of equipment sometimes may prove a bottleneck. If underhand stoping is used, mining begins just after the crown pillar in the downward direction in slices.
- 8. Cycle of Operation Unit Operation Auxiliary Operation In this method mostly using diesel operated equipment. Production cycle of this method mostly equal to stope and pillar operations.
- 9. Unit Operation Drilling Blasting Mucking Haulage (A)Drilling Use a) Pneumatic percussion b) Hydraulic percussion c) Rotary percussion Diameter of drilling holes -45 to 76 mm Length of drill holes -3 or more Holes drilled -inclined or horizontal
- 10. (B) Blasting Using a) ANFO (Ammonium Nitrate and Fuel Oil) b) Slurries c) NG based Explosives
- 11. (C)Mucking For horizontal work(up to ore pass) LHD CAVO Rocker shovel or scraper From ore pass to chute Car Trucks
- 13. Auxiliary operation Back filling Supporting work Ground control Back filling At work out area At require area At drainage area Supporting work Cable bolting Timbering Packs walling Ground control
- 14. Merits Productivity: Moderate 10-20 tons/man/shift. Max. up to 30-40 ton/man/shift. Production Rate: Moderate. Applicable for irregular bodies. Scope of Mechanization: Moderate. Ground Condition: Suitable for worst ground condition. Recovery: Maximum if pillar mined, up to 95% or more. Depth: Proved vital for deep mining at high rock pressure.
- 15. Demerits Cost of backfilling: Up to 50% of total mining cost. Operational skill: Requires skilled labor. Working atmosphere: At depth wet filling create humidity problems Low grade: Not suitable for low grade ore due to high mining cost.
- 16. Variants Cut and fill with flat back: (a) Conventional (b) Mechanized Cut and fill with inclined slicing Longwall cut and fill stoping Post and pillar- Cut and fill stoping Stope-drive cut and fill stoping: (a) starting from upper level (b) starting form lower level
- 17. Filling Material The fill material used in this method varies, depending on the support required and the material that may be available to the mine operator. Crandall (1992) list the major types of fill as follows: Waste fill. Pneumatic fill. Hydraulic fill with dilute slurry. High density hydraulic fill.