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Abstract Based on blasting excavation in anchorage tunnel of Aizhai suspension bridge，the development laws of damage degree and loose ring of surrounding rock under different blasting loads are obtained by acoustic wave testing method. The corresponding relation between the damage degree of surrounding rock and the peak particle velocity(PPV) of vibration is discussed. Moreover，the threshold which leads to accumulative damage to rock mass is discussed；and a comparatively complete description of the development of damage degree and loose ring of surrounding rock is given. On the basis of above-mentioned researches，a reasonable control index of blasting vibration velocity is obtained. It is shown that not only the disturbance of single blasting on the surrounding rock should be controlled during blasting construction of anchorage tunnel，but the emphasis should be put on the accumulative vibration effect of surrounding rock induced by frequent short-distance blasting；and the corresponding control measures should be taken. When the PPV of the surrounding rock is controlled in the range of 3–6 cm/s；the maximum thickness of the loose ring of the surrounding rock is about 2.3 m；and the average damage degree of the surrounding rock is 0.15. When the PPV of the surrounding rock is less than 2 cm/s，the accumulated damage degree of the surrounding rock is not obvious，which can be regarded as the threshold of blasting vibration accumulated damage in this project.
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Received: 15 December 2008
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