| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 106 === In this study, the PFC2D code was used to explore the circular tunnel and horseshoe tunnel with four different overburden depths (H=300, 400, 500, 600 m).The tunnel was excavated in a hard rock (granite), and the whole section was excavated without support. The stress redistribution, displacement distribution and microcrack development during tunneling were analyzed under three different initial stresses (K=0.5, 1, 2).
The results show that the horseshoe main tunnel excavation, change of the micro bonding stress and particle displacement during tunneling are highly related different initial stresses and geometric linear shapes of Excavation face . The most need to pay attention to the roof of tunnel under K=2, the microcrack development in the three-stage tunnel excavation, has the maximum destruction area.
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