隧道是所有土木工程中與地質關係最密切者，只要岩體中存有節理（或弱面），整體岩盤工程行為就常由節理來主控。理論公式常將岩盤假設為均質、等向，開挖之隧道斷面形狀亦多侷限為圓形（如Kirsch公式），致與岩盤工程間之設計分析都不易相互套用，故需要另外之工具與方法來進行仿真模擬。本研究以UDEC二維數值分析程式，對圓形隧道進行開挖模擬，並引入岩體力學行為中方向性最強的單一節理，就其位於不同空間方位對隧道之影響進行探討，並與無節理情況進行比較，研究結果希望能提供一條節理對隧道開挖影響之預判能力，及更多節理分佈影響之推理。

Tunneling is the work in civil engineering that surrounding geological condition plays a very important role. Plane of weakness or joints dominate the construction behavior in rock mass. It is always assumed that tunneling rock is homogeneous and isotropic for most theoretic formulas such as Kirsch formula, and tunnel cross-section shape is circle. The ideal assumption can’t fit most practical conditions in construction design and analysis. Therefore, it has to stimulate in other ways. This study use two-dimensional numerical software UDEC to stimulate the excavation of circular tunnel. Single joint cutting circular tunnel with different orientations is simulated based on single joint has the strongest anisotropy. The tunneling mechanical behavior both single joint condition and no joint condition are analyzed and compared. Some conclusions and suggestion are presented for the practical design, constructions, and monitoring.

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