Tunnel millisecond-delay controlled blasting based on the delay time calculation method and digital electronic...

Area of Science:

• Civil Engineering
• Mining Engineering
• Geotechnical Engineering

Background:

• Tunnel blasting generates significant vibrations, impacting surrounding structures and the environment.
• Traditional blasting methods often lack precise control over delay timing, leading to suboptimal rock fragmentation and increased seismic effects.
• Digital electronic detonators offer enhanced precision for millisecond-level delay timing in blasting operations.

Purpose of the Study:

• To develop a method for calculating optimal delay times for cut, easer, and periphery holes in tunnel blasting.
• To analyze the effects of delay timing on rock breakage, wave superposition, and vibration reduction.
• To validate the proposed method through field tests and application in a tunnel project.

Main Methods:

• Formulating delay time calculation based on rock breakage and wave superposition theory.
• Developing specific delay time formulas for different hole types (cut, easer, periphery).
• Conducting field tests to analyze vibration velocities, rock breaking, and wave cancellation with varying delay times.
• Comparing vibration characteristics between digital electronic detonators and non-electronic detonators.

Main Results:

• Optimal delay time of 5 ms for cut holes achieved effective rock breakage and wave cancellation, reducing vibration velocity to 0.46-0.51 cm/s.
• Delay times of 6 ms or longer for cut holes compromised rock breakage effectiveness.
• Optimal delay times for easer and periphery holes were also determined to be 5 ms.
• Vertical peak particle velocity decreased by 69.70% (from 2.974 cm/s to 0.901 cm/s) using digital electronic detonators with optimized delay times.

Conclusions:

• Prioritizing rock breakage and free surface formation, followed by wave superposition cancellation, is crucial for optimizing delay times.
• The proposed delay time calculation method is accurate and effective for reducing tunnel blasting vibrations.
• Digital electronic detonators, coupled with optimized millisecond delay timing, offer a significant advantage in vibration mitigation for tunnel construction.