Abstract

This paper presents a series of field test results conducted at a site in the north western part of Singapore to investigate blast-induced ground vibration propagation through mixed geological media which comprised of residual soils and granitic rock. In total, six blast tests were carried out. Tri-axial accelerometers were placed at different standoff distances from the blasting, and the acceleration time histories were recorded at the ground surface, at various depths in the soil mass, as well as in rock mass to monitor the vibrations. Empirical formulae for predicting the peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data. The ground vibration attenuation across the soil-rock interface was carefully examined and the study shows that the soil-rock interface plays a significant role in changing the ground vibration intensity. Results from this field test have provided valuable data for calibration of numerical models developed to study the ground shock propagation.

1.
Introduction

Singapore's rapid development requires extra space for residential, commercial and industrial use. Drilling and blasting is the widely accepted method for large-scale rock breaking activities in civil engineering constructions due to its cost effectiveness, higher efficiency and ability to break hard rock.

However, ground vibrations from blasting are undesirable and it can cause damage to nearby structures. In practice, the damage to nearby structures due to ground vibrations has been controlled by various rules and regulations available. The existing vibration limits are not always applicable, as they depend on the geological conditions of the site and dynamic characteristics of the structure.

Over the years, structural responses and damage to ground vibrations from blasting have been extensively studied and those studies concentrated on establishing allowable ground vibration levels in terms of peak particle velocity (PPV) together with the frequency of the ground vibration to limit the structural damage (DSTA, 2009). However, safe vibration limits given by different researchers differ because those limits were usually obtained based on field observations of low-rise residential buildings. A number of researchers have investigated the problem of ground vibration prediction and have proposed various formulae (Langefors and Kihlstorm, 1978; Wiss, 1982; Dowding, 1985; Zhou et al., 1998). These formulae were obtained based on field observations from various sites. According to Siskind et al. (1980) amplitude, frequencies and durations of the ground vibrations change during the wave propagation due to various factors such as geometric absorption and interaction with various geological media and structural interfaces. Zhou et al. (1998) experimentally studied the ground shock wave propagation through mixed geological media due to detonation of explosive in an underground storage chamber. Kahriman (2004) carried out field tests at a limestone quarry to establish a reliable formula to predict the peak particle velocity.

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