Weak Zone Determination Inside The Tunnel Using H/V Ratio Method

Tunnel is a vital structure in transportation as it shortens the distance between places through underground. Nevertheless, since it goes via underground, there are several risks might occur, such as tunnel collapse. This occasion will result in plenty of casualties. Therefore, as the preventive attempt, there should be a particular method to determine that the tunnel is strong enough. One of the methods that may work for this case is microtremor and one of the most common method in microtremor is H/V ratio. H/V ratio is able to describe a natural frequency of a place or a structure. By using the natural frequency, the stability of the tunnel can be determined. To test out the method, a measurement is conducted in a tunnel at Institut Teknologi Bandung. This tunnel connects the main campus and the campus sports ground. It also lies under the main road which has a lot of traffics at all time. The measurement is done on the wall side of the tunnel, while the space between measurement station is 6 meters and the station cover the whole tunnel wall side. After measuring the tremor in every station, the tremor data will be processed with Geopsy software and the natural frequency of the tunnel will be acquired. Subsequently, the natural frequency of the entire tunnel will be plotted and the result from this plotting can be used to determine the weak zone of the tunnel.