Evaluation of Rock Vibration Generated in Blasting Excavation of Deep-buried Tunnels

다국어 초록 (Multilingual Abstract)

The experimental tunnels of the China Jinping Underground Laboratory are constructed in a maximum overburden depth of 2375 mand subjected to extremely high in situ stress more than 50 MPa. When these deep-buried tunnels are excavated with the method ofdrill and blast, the surfaces created by blasting are generated almost instantaneously, and thus the initial stress on these surfaces is alsosuddenly released. This transient release of in situ stress causes elastic waves to propagate in rock masses and may have an importanteffect on the subsequent rock vibration. In this study, a three-dimensional FEM modeling in combination with site investigation isconducted to research the Peak Particle Velocity (PPV) attenuation and frequency characteristics for the rock vibration induced bytransient stress release and its combined actions with blast loading. The results indicate that the transient release of the high stressgenerates considerable vibration velocity that is comparable to that of blast loading. It is not a negligible excitation for the rockvibration generated in blasting excavation of deep-buried tunnels. Furthermore, the vibration induced by transient stress release hasmuch lower frequency than that caused by blast loading. This causes the unloading vibration to decay more slowly and become themajor vibration component at far distances. Also, the effect of transient stress release is found to enhance intensity of the totalvibration and furthermore cause an increase in its low-frequency content. On the basis of this, the allowable charge amount per delayand the minimum safety distance are finally discussed with a special emphasis on the contributions of the transient stress release tothe total vibration.

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