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The geology of Ulleung-Do is dominated by volcanic rocks with low strength and trachytic rocks with high strength but containing vertical joints that yield easily. Consequently, rockfalls along roadcuts are a major geological hazard, with the potential to affect the ring road of Ulleung-Do. In this study, we performed three types of rockfall hazard-risk assessment on the 3-km-long section of the ring road expected to have the highest possibility of rockfall. We used a rockfall ranking sheet in a roadside landslide hazard map, the Slope Stability Inspection Manual for National Highways (Japan), and a rockfall hazard rating system for inspection from the Japan Highway Public Corporation. We also employed the evaluation criteria of 'RHRS' developed by the Federal Highway Administration (FHA). An analysis of roadcuts at 27 sites with regard to geographic and geological conditions resulted in the identification of three classes of rockfall hazard (high, medium, and low). Of note, over 74% of slopes were assessed as high-and medium-class. Finally, a rockfall hazard map of the northeast region of UlleungDo was produced based on the evaluation results.

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Explosive blasting is a very useful tool for mining and civil engineering applications. It, however, may cause severe environmental hazards on adjacent structures due to blasting impact. Blast engineers try to make optimum blast design to provide efficient performance and to minimize the environmental impact as well. It requires a pre-assessment of the impacts resulting from the blasting operation in design stage. One of the common procedures is to evaluate the proposed blast pattern through a series of test blasting in the field. Another approach is to evaluate the possible environmental effects using the numerical methods. There are a number of input parameters to be prepared for the numerical analysis. Some of them are well understood, while some are not. This paper presents some results of sensitivity analysis of the basic input parameters in numerical modelling of blasting problems so as to provide sound understanding of the parameters and some guidelines for input preparation.

Blast-induced ground vibrations may cause an environmental impact such as damage on adjacent structures and facilities. Ground vibrations occurred in explosive demolition of structures are induced by ground impact of disintegrated mass concrete, as well as by explosive blasting. The waveform record from explosive demolition is divided distinctly into early part of blast-induced vibration and later part of impact-induced one. The two wave patterns show very different characteristics in frequency contents and duration of ground vibration, which may have different effects on adjacent structure. In this paper, several examples are investigated numerically to provide sound understandings of structural responses to the demolition-induced ground motions. Two reinforced concrete frames are analyzed by using step-by-step procedure. Their responses are summarized in terms of floor velocity envelopes. The response characteristics between high-rise and low-rise building were also investigated. It is shown that the responses are quite different depending on the structure type and on the frequencies of the ground vibration.