Blasting is a relatively economical and efficient excavation method compared to other methods such as mechanical excavation. However, when tunnel sites are located near residential areas, the charge weight is often reduced to limit the impacts of vibration and noise. This makes it difficult to maintain the scheduled excavation advance rate. In recent years, however, advanced blasting technologies such as computerized jumbos and high-accuracy electronic detonators have allowed better control over tunnel blasting vibrations. Additionally, new vibration measurement systems have been introduced that enable the simultaneous monitoring and analysis of blast vibration results. Here, we applied these advanced technologies in a restricted blasting zone to reduce the environmental impact and enable the excavation advance rate to be maintained.

1 Introduction

Blasting is rapid and economical, making it advantageous compared to other tunnel excavation methods. However, it can sometimes cause environmental problems such as vibrations, especially when excavation sites are close to residential areas. To mitigate vibrations in such areas, the amount of charge is commonly reduced by shortening the drill length (advance distance) or by suspending blasting at night. However, these precautions can reduce the advance rate, thus delaying the construction schedule.

2 Study Site

This paper discusses a case study in which attempts were made to control vibrations in a residential area. Newly developed advanced techniques, such as computer jumbo, advanced electronic detonators, and real-time vibration measurement systems (Takaaki Inuzuka, 2018), could be used to modify the blasting conditions such that an appropriate advance rate could be maintained despite vibration mitigation in blasting-restricted areas. In this case study, the blasting-restricted area covers ~300 m of tunnel, as shown in Figure 1. In this area, several residential houses are located along the tunnel alignment. Figure 2 shows the relation between the tunnel distance (TD) and the overburden. At TD = ~1450 m, several residential houses are located above the tunnel route with a small overburden of ~45 m.

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