本研究利用UDEC軟體探討馬蹄形隧道於無節理、單一節理與兩條正交節理岩體中開挖之應力與變形影響，岩體是否發生塑性破壞並計算安全係數以評估岩體之安全性。首先分析馬蹄形隧道開挖於無節理岩體於四種不同覆岩深度(K=1)與四種不同初始應力(K=0.5、1、2、3)之情況。接著討論傾角變化對於單一節理通過右角隅岩盤之情況(K=1)，以及兩條正交節理岩體於四種不同初始應力(K=0.5、1、2)之情況，最後將無節理、單一節理、兩條正交節理岩體進行綜合對比。
本研究結果顯示當單一節理通過角隅，節理角度於β=15~75˚之間，軸差應力較大且有塑性區產生。兩條正交節理岩體在應力、位移、塑性區分佈情況，大致為單一節理β=45˚與135˚趨勢的疊加。在本研究的分析範圍內，產生最多塑性破壞為兩條節理分佈且K=3的情況。

In this study, UDEC software is used to investigate the effects of stress and deformation of horseshoe shape tunnel on unjointed, single joints and two orthogonal jointed rock masses. Whether the rock mass is plastically damaged and the safety factor is calculated to evaluate the safety of the rock mass. First, the horseshoe shape tunnel excavation was carried out on four different overburden depths (K=1) and four different initial stresses (K=0.5, 1, 2, 3). Next, discussing the case where the variation of joint dip angle is for a single joint through the right angle shale disk (K=1), and the two orthogonal jointed rock mass are at four different initial stresses. Finally, compare with orthogonal jointed rock mass with no joints and a single section.
The results of this study show that when a single joint passes through the corner, the joint angle between β=15~75˚ the axial stress is large and the plastic zone is produced. The distribution of stress, displacement and plastic zone of two orthogonal jointed rock masses is roughly the superposition of the single joint β=45 ̊ and 135 ̊ trends. Within the scope of the analysis of this study, the most plastic failure was caused by two joint distributions and K=3.

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