Numerical Simulation of Blasting at Tunnel Contour Hole in Jointed Rock Mass

摘要

The orientation and the spacing of discontinuity affect a failure mechanism of blasting, and they willrncause a severe over-break. Such an over-break causes increasing the construction time and cost. So, itrnis necessary the study to clarify failure mechanism of blasting by orientation and the spacing ofrndiscontinuity. In this study, using PFC2D(Particle Flow Code 2Dimension), which was developed byrnItasca Ltd., blasting at tunnel contour holes is simulated. To find out affection by the joint orientationrnit is set an analysis model having the angle of discontinuity the 0, 10, 20, 30, 45, 60, 90 degree. Whenrnthe angle of discontinuity is under the 45 degree, the rock mass does not break out along new cracksrnbut break out along the joint. When the angle is over 45 degree, the affection of discontinuity onrnblasting is decreased but failure surface is very rough. In order to find out the affection of joint spacingrnthe analysis model is set joint spacing having 100, 200, 300 mm. As joint spacing is decreased thernfailure surface is very rough. When the rock mass have 3 joint set, the analysis model is set that thernspace of blast hole is 500, 600, 700 mm. From the result, the best blast hole spacing is 600 mm.