What is Explosive Contamination?
Earthquakes, air shock waves, noise, flying rocks, and weapons smoke caused by explosions have harmful effects on the surrounding environment of the explosion area. In recent years, various countries have been studying controlled blasting technology and safety protection measures to reduce the harmful effects of blasting, and have formulated laws and stipulated various safety standards.
Earthquakeexplosive – When explosives explode in a rock mass, some of the energy is converted into elastic waves, and the vibration is caused by propagation in the crust. The destructive effects of blasting earthquakes on buildings and structures around the blasting area are called seismic blasting effects.
At present, the vibrational velocity of particles is mainly used as a criterion for determining the damaging effect of an explosive earthquake on buildings and structures, and is usually calculated by the empirical formula V = K (Q n / R).
Where V is the vibration speed of the particles (cm/s); K is the coefficient related to site conditions and blasting methods; Q is the maximum load of the segmented blast or the total load of the simultaneous blast (kg); R is the distance from the load center to the protected target point (m); n is the coefficient, n is from 1/3 to 1/2; is the attenuation index of the seismic wave. The variation range of K y is very large, which can be selected according to similar conditions or determined by experiments in a certain ratio.
The criterion for damage to buildings and structures caused by seismic explosions is primarily non-structural damage. For ordinary earthen buildings, it is generally stipulated that the blasting vibration speed should not be more than 5 cm/s. The use of millisecond blasting, pre-split blasting, buffer blasting, and changing the initiation sequence are effective measures to reduce blasting earthquakes.
The explosive air shock wave is formed by a strong compression of the surrounding air by the high temperature and high pressure gas produced by the explosion of explosives.
It can damage buildings and underground supports, pipes and other installations close to the ground explosion zone and even cause casualties. Generally, the maximum surge pressure peak or the maximum impulse per unit area is used as the basis for assessing the degree of damage. Many countries use experimental and engineering data to determine the allowable overpressure value for buildings and use empirical formula calculations to determine the safe distance or maximum allowable blast load.
Blast noise: the sound wave that forms when the blast air shock wave overpressure is attenuated below 180 dB. Sound pressure is related to the amount of medicine, depth of burial, distance, topography, and weather conditions. The noise from explosions harms people’s health and can damage buildings. The control standard varies from country to country, for example, the US published standard is no more than 128dB.
The flying stone refers to the individual rock that flew very far during the blasting. It threatens the safety of people, buildings and equipment near the explosion zone. The use of controlled blasting technology is an effective measure to prevent rocks from being thrown. In general blasting, the blocking load and length should be reasonably determined, the weak surface of the rock mass structure should be avoided, and the blasthole measurement and acceptance system should be strictly implemented.