Determination of Optimized Blasting Pressure through Critical Volumetric Strain Monitoring

The more increase of construction of railways and roads, the more increase of tunneling in Korea. NATM(New Austrian Tunneling Method) is used for most tunneling construction, and excavations by blasting are usually adopted. The most important consideration in blasting excavation is how to minimize damages and overbreaks in the rock, which is brought up interests from many researchers. The damages and overbreaks in the rock directly influence on the stability of the tunnel during construction as well as on maintenance after construction. The dynamic properties of the rock are measured by strain gauges during trial blasting from two different sites. A procedure to evaluate the critical volumetric strain of the rock using measured values during blasting is proposed. Rock damage zone analyses are performed using a FEM analysis program called ABAQUS/Explicit by adopting the evaluated critical volumetric strain. The technique to determine optimum blasting pressure is also proposed using numerical analysis results.