Abstract
It is essential to control the damage to the surrounding rock and engineering structures in the process of cut blasting with a single free surface in underground mining. To reduce vibration induced by cut blasting, this paper proposes short‐delay cut blasting, in which blast holes that are near each other are sequentially initiated with short‐delay times. Experimental tests of cut blasting were conducted in a roadway in the Shaxi copper mine to compare the peak particle velocity (PPV) and frequency characteristics of simultaneous blasting and short‐delay blasting. Numerical modelling was then developed to study the influence of short‐delay times on blast vibration. The accuracy of the numerical simulation was verified by the comparison of the test and simulated data of single‐hole blasting. The results show that the amplitude reduction ratio (ARR) value increases gradually with the increase in delay intervals, and the vibration reduction for delay intervals smaller than 6 ms is very limited, particularly in the near field. The principal frequencies (PFs) for short‐delay blasting are similar to those for simultaneous blasting, which implies that the frequencies do not increase directly with the decrease of the delay intervals. The experimental tests also show that the mean frequencies (MFs) for the 8 ms delay are slightly higher than those for the 0 ms delay blast. In the case of ensuring the rock breaking of cut blasting, longer delay intervals of 8∼10 ms are beneficial to further reduce PPV in practical blasting.
Highlights
Hard rock fragmentation by blasting is the most widely used and cost-effective means in mining and construction operations
Reducing the harmful vibration induced by cut blasting with large charge weight per delay is a critical challenge in underground mines [17]
To compare the vibrations induced by the simultaneous blasting and short-delay blasting and to obtain the characteristics of vibrations induced by blasting with different delay intervals, we conducted some experimental tests in Shaxi underground copper mine using four-hole schemes with a single free surface
Summary
Hard rock fragmentation by blasting is the most widely used and cost-effective means in mining and construction operations. Reducing the harmful vibration induced by cut blasting with large charge weight per delay is a critical challenge in underground mines [17]. Is paper studied the vibration induced by short-delay cut blasting through both experimental tests and numerical simulation. Cut blasting tests carried out in an underground mine are used to compare the vibration of simultaneous blasting and short-delay blasting. To compare the vibrations induced by the simultaneous blasting and short-delay blasting and to obtain the characteristics of vibrations induced by blasting with different delay intervals, we conducted some experimental tests in Shaxi underground copper mine using four-hole schemes with a single free surface. Blasting tests with four holes were carried out to study the vibrations induced by simultaneous blasting and short-delay blasting. Where M, N, and P are the vertical, radial, and transverse components of particle velocity, respectively
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