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Abstract Based on the in-situ monitoring of acoustic velocity in Damaoshan Tunnel with large section，accumulative damage range of surrounding rock is studied in tunnel with large section excavating with two side-wall pilot tunnel method of the advancing to-and-fro blasting operations. Monitoring results of acoustic velocity show that surrounding rock will cause damage at a certain degree and range in advancing to-and-fro blasting load operations. The accumulative damage range of surrounding rock is mainly determined by the blasting of excavating face of pilot tunnel I which is parallel to it. The range increases with the approaching of excavating face of pilot tunnel I，and reaches the maximum value when the two are flushed. However，when the excavating face of pilot tunnel I gradually moves away and the blasting of pilot tunnel III starts to get through，it only leads to the increase of damage degree；the damage range of surrounding rock does not expand. Therefore，when simulating the damage range of surrounding rock in advancing to-and-fro blasting load operations，single blasting parallel to monitoring section can be simulated as repeated to-and-fro blasting vibrations approximately. The vibration velocity which determines the damage range of surrounding rock can be transformed into explosion pressure through software DYNA；and then the pressure can be transferred to anisotropic damage model of rock realized by UDEC software. Compared with monitoring results，this method can better simulate the accumulative damage range of surrounding rock in advancing to-and-fro blasting load operations so as to provide for reference in similar engineering projects.
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Received: 23 April 2009
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