The effect of blasting pattern, rock strength and different explosives on the blast-induced ground vibration was studied to determine the maximum charge weight per delay within a given vibration level. The blasting vibrations were measured at 10 sites along the subway line in Seoul and the empirical particle velocity equation from over 100 test data was obtained. V= K(D/W1/3)-n, where the values for n and K are estimated to be 1.7 to 1.5 and 48 to 138 respectively.
L'effet, du type de tir, de la resistance des roches et de divers explosifs, sur la vibration de terrain provoquee par le tir à explosif, a ete etudie à fin de determiner le poids de charge maximum par delai dans une limite de vibration donnee. Les vibrations de tir à explosif ont ete mesurees sur les dix sites le long des deux lignes de metro seoulite et l'equation empirique de la vitesse de particules à partir des cent resultats d'essais à ete obtenue. V = K(D/w1/3)-n, où les valeurs de n et K sont supposees respectivement de 1.7 à 1.5 et de 48 à 138.
Der Einfluss von Sprengbild, Gesteinsfestigkeit und sprengstoffsorten auf die Boden-erschuetterung ist untersucht, um die maximale sprengstoffmenge per Abschlag unterhalb der gegebenen Erschuetterungsniveau zu bemessen. Die Erschuetterungsmessungen waren in 10 verschiedenen Orten entlang der U-Bahn Linie in Seoul durchgefuehrt. Eine empirische Gleichung ueber die Durchlaufgeschwindigkeit der Partikel ist aus 100 Untersuchungsdaten so gewonnen, dass V = K(D/w1/3)-n, wo die Werte von n und K als 1.7–1.5 und 48–138 entsprechend bestimmt worden sind.
The blasting works for quarries and underground construction near urban areas has recently increased complaints of ground vibrations. The 3rd and 4th subway line in Seoul pass through the metropolitan area having tall buildings, large shopping centers and national cultural treasures. The distance from blasting sites to structures was generally within 40 meter and down to 14 m from cultural treasure site. In order to prevent the damage to structures, it was necessary to minimize the blasting vibrations. Many investigators, Duvall et al(1961), Nicholls et al(1971), Siskind(1973), Langefors et al(1978) and Gusstafsson(1981) have studied on the effects of air and ground vibrations from blasting on residences and other types of structure. Some reports by Woo et al (1967), Ryu et al(1979), Huh(1984) and others in Korea described the relationships between damage and ground vibrations from nearby blasting. The excavating work for the construction of 3rd and 4th subway line includes open cuts of 33.7 Km and tunnel blasting of 15.0 Km. The geology of the Sites is mainly composed of Precambrian gneiss which is intruded by Juriassic granite and overlain by alluvium with unconformity. So the rocks were granite and gneiss along the subway lines, the blasting method was adjusted corresponding to the rock type. The objectives of this study are;
to formulate the empirical vibration equation appropriate to each location around subway line,
to evaluate the effects of blasting pattern, rock strength and explosives on the blasting vibrations,
to determine the maximum charge weight per delay within allowable vibration values.
The characteristics of blasting vibration have been Well described and are summarized briefly here. Particle velocity is more closely associated with damage to structure than either displacements or acceleration (Nicholls 1971). It should be observed in three mutually perpendicular directions: a vertical component, a horizontal component radial and a horizontal component transverse to the source. Because the distance from shot to structures is too short, the maximum vibration level among three components was adopted. The effect of distance and charge weight on the vibration level is basic to all blasting vibration studies. Many types of propagation equations have been proposed. The peak particle velocity of each component of ground motion (V, cm/sec) can be expressed by a equation as a function of distance (D,m) from the blast and maximum charge weight (W, kg) per delay, V = K (D/wb)-n: (1) where K, b, and n are constants associated with a given site. Empirical methods have been used to estimate values of band n. Specially b may be about (square root scaled distance) or (cube root scaled distance). The measured data showed that cube root scaled distance was most applicable to this study.
The shots were measured with three types of seismoraph. Sprengnether (VS-1200), VME (nitro-consult co) and Rion (VM-12B). The former was mainly used and the latter two was auxiliary used. The natural frequency of sprengnether is 5 to 200 Hz within the range of the observed frequencies(Nicholls 1971). Three portable seismographs were calibrated in accordance with the objectives of this research.
A total of 109 blasts were recorded at 10 sites.
