本研究首先探討如何利用PFC2D模擬雙軸及巴西試驗，求出岩盤六個巨觀參數(包含qu、E、ν、C、ϕ、σt)對應之八個微觀參數，接著利用微觀參數分析岩覆深度300公尺之隧道開挖數值模式。探討於無節理及一條節理岩盤中之圓形及馬蹄形隧道開挖引致之應力位移微觀之發展。
研究探討中，圓形開挖下之鍵結壓應力會隨著隧道切向分布，鍵結拉應力則是徑向傳遞，圓形隧道開挖後距離5倍隧道半徑(5r)之範圍內皆會受到影響，其中在2r之範圍內之鍵結應力調整最為明顯。馬蹄形隧道開挖下，左右兩角隅處會同時被垂直向與水平顆粒束制住，較其他顆粒更不容易移動，此時之壓應力會相對增加而呈現應力集中之現象。

The numerical software PFC2D is used to investigate the microscopic behaviors of tunneling such as crack and bonding stress development after excavation. Firstly, this study investigate a series of sensitivity of micro parameters and conducting the biaxial and Brazilian test in order to produce an acceptable macroscopic parameters (qu、E、ν、C、ϕ、σt) of selected granite between PFC2D numerical results and lab rock testing results. Secondly, the shape of circular and horse-shoe tunnel are built with overburden depth of 300 meters. The surrounding rock masses of tunnel include no jointed and single-jointed rock situations.
The analytical results show that micro bonding stress after excavation of circular tunnel has been gradually influenced from excavation surface to distance of 5 times the tunnel radius (5R) and the produced micro stress is annular. During horse-shoe excavation, the around particles near tunnel corner are restrained by side wall and floor. This lack of displacing ability for particles cause an ascending compressive bonding stress, so-called stress concentration.

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