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Many times excavation in rocks are required for foundation of structure. The procedure for excavation in rocks is different than excavation in ordinary soils. It requires skilled manpower and specialized tools and equipments for excavating the rocky ground.Procedure for Excavation in Rocks
Excavation in rock requiring drilling and blasting shall be done under coordination of competent and responsible supervision. Prior permission shall be taken wherever necessary for employing such operations.
Fig: Rock Excavation by Blasting
The selection of technique or equipment depends on the depth of rock excavation & proximity to structures or hazardous areas. For smaller rock breaking Compressed air based jack hammer shall be employed.
Fig: Jack Hammer for Rock Breaking
For hazardous areas where blasting & vibrations are not allowed such as in Running plant , Refineries etc. chemical rock fissuring shall be employed.
Fig: Chemical Fissures Method for Rock Breaking
For larger areas excavator mounted Hydraulic hammer shall be employed for braking the rock. Where there is no objection for blasting & larger areas blasting shall be employed after prior approval of the Customer.
Fig: Excavator Mounted Hydraulic Hammer
The blasting sequence & methods employed rock excavation should be submitted for review & approval of contractor / Customer. For shallow rock cutting drilling of holes shall be carried by jack driller , for deeper blasting wagon mounted drill shall be used. The explosives shall be charged as per the calculations & blasting carried. The blasting operations shall be carried at a pre fixed time ( shall not be changed till all blasting operations are completed in the project ) with all safety precautions. The loosened rock shall be removed using excavator & stored at designated areas. Over blasting or under blasting shall be verified for acceptance of level change instead of re-blasting. Designers concern shall be taken before deciding. Any over excavation or irregular foundation bottom shall be filled with lean concrete only. All blasting and handling of explosives shall be carried out by a licensed blaster as per the guidelines of Mining department.
Fig: Wagon Drill for Deep Drilling into Rocks
