Excavation in rocky ground is often essential for laying foundations of various structures. Unlike excavation in ordinary soils, rock excavation requires a distinct set of procedures, specialized tools, and skilled manpower due to the hardness and density of rocks. Understanding the right methods and safety precautions is crucial for successful and efficient excavation in such challenging conditions.
General Procedure for Excavation in Rocks
Excavating rocks generally involves drilling and blasting techniques, which must be carried out under the supervision of competent and responsible personnel. It is important to secure all necessary permissions before undertaking any drilling or blasting operations, especially when these activities are near existing structures or in sensitive areas.
Methods of Rock Excavation
Rock Excavation by Blasting
Blasting is a common and effective method for breaking hard rock, particularly when large areas need excavation. The choice of blasting technique and equipment depends on factors such as the depth of rock excavation and the proximity to nearby structures or hazardous zones. The blasting sequence and methods should be submitted for review and approval by the contractor or customer to ensure safety and compliance.
Jack Hammer for Rock Breaking
For smaller rock excavation projects, compressed air-powered jack hammers are frequently used. These tools are efficient for controlled breaking of rocks and are suitable when blasting is either not feasible or not permitted.
Chemical Fissures Method for Rock Breaking
In locations where blasting and vibrations are prohibited, such as running plants or refineries, chemical rock fissuring is the preferred method. This technique involves using chemicals to create fractures in the rock, allowing it to be broken apart with minimal disturbance to the surroundings.
Excavator Mounted Hydraulic Hammer
For larger excavation sites where blasting may not be suitable or allowed, excavator-mounted hydraulic hammers are an effective alternative. These machines can break large rock masses efficiently without the noise and vibration caused by blasting.
Blasting for Large Areas
When blasting is permitted, especially for extensive rock excavation, it must be carefully planned and executed. Shallow holes are drilled using jack drillers, while wagon-mounted drills are used for deeper holes. Explosives are charged based on precise calculations to achieve the desired breakage. Blasting operations are conducted at predetermined times to ensure safety and coordination across the project. All necessary safety precautions must be strictly followed.
Post-Blasting Activities
After blasting, the loosened rock debris is removed using excavators and transported to designated storage areas. It is important to verify the extent of blasting to avoid both over-blasting, which may cause excessive excavation, and under-blasting, which might require re-blasting. The design team should be consulted if there are discrepancies in the excavation levels. Any irregularities or over-excavation in the foundation bottom should be rectified using lean concrete to maintain structural integrity.
Safety and Regulatory Compliance
Handling explosives and conducting blasting operations must be done by licensed blasters in compliance with guidelines set by the Mining Department and relevant authorities. This ensures the safety of workers and nearby structures and minimizes environmental impacts.