| Abstract: | 岩坡工程行為受到不連續面方位及坡面開挖方位之影響相當顯著，在相同的不連續面方位下，不同的坡面開挖方位，將形成所謂的順向坡、斜交坡及逆向坡，其穩定性、崩塌規模、破壞模式等均呈現截然不同的特性，本文稱之為岩坡工程行為之異向性。岩坡工程行為之異向性，包括順向坡、斜交坡及逆向坡之工程特性，已為大地工程師及工程地質師確認、重視且熟悉議題。以經驗法為基礎的技術規範，也行之有年，然而卻欠缺全面、統一的分析模式，以探究岩坡工程行為之異向性。
本文利用FracMan生成離散裂隙網絡(DFN)，引入PFC3D建構一個以合成岩體(SRM)為基礎的統一分析模式，以模擬從順向坡至斜交坡，再至逆向坡的岩坡崩塌行為。本文針對具有一組不連續面傾角之岩坡(坡角75°、坡高250m、坡長580m)進行一系列的數值模擬，分析變因包括：不連續面傾角(30°、45°、60°、70°)及坡面與不連續面傾向夾角(0°~180°，每隔10°)，探討從順向坡、斜交坡到逆向坡之崩塌行為之變化，嘗試透過崩塌能量、崩塌體積、崩塌位移方向及波及區域等量化指標描述崩塌行為。研究結果顯示：(1) 基於合成岩體所建構之統一分析模式，不需預設破壞模態，可模擬順向坡、斜交坡到逆向坡之崩塌行為，且分析結果合理，符合一般工程經驗。(2) 崩塌能量包含崩塌量體及重直落距，可作為崩塌事件規模之量化指標。崩塌能量也較一般習用極限平衡分析所得之安全係數更能呈現崩塌事件所引致的風險及損失。(3) 本文以崩塌能量為指標，嘗試建立岩坡之RMR不連續面方位評分調整。(4) 本文根據崩塌前、後之數值地形模型（DTM）之變動，可求得波及區域。波及區域分為陷落區及堆積區，其高程可作為描述地形變動的嚴重程度，較一般常用之安全係數、運移距離、退縮距離、抵達角有更豐富、更全面的資訊內涵，可精進岩坡穩定及風險分析工作。
;The behavior of rock slope engineering is significantly affected by the orientation of discontinuity and excavation orientation of slope face. Under same orientation of discontinuity, the different excavation orientation of slope face will comprises of dip slope, oblique slope and anti-dip slope. What′s more, the rock slope engineering will show completely different characteristics such as stability, landslides scale and failure mode, which is called the anisotropic engineering behavior of rock slope in this paper. The anisotropic engineering behavior of rock slope including the different engineering properties of dip slope, oblique slope and anti-dip slope, has been recognized, valued, by geotechnical engineers and engineering geologists. Technical specifications based on empirical methods have also been used for many years, but they are sort comprehensive and unified analysis model to explore the anisotropic engineering behavior of rock slope.
In this paper, I use the FracMan to generate discrete fracture network(DFN), and imports into PFC3D to construct a unified analysis model base on synthetic rock mass (SRM). That is simulated for the landslide behavior of rock slopes from dip slope to oblique slopes and then to anti-dip slope. This paper carries out a series of numerical simulations for a rock slope with a set of discontinuity (slope angle 75°, slope height 250m, slope length 580m). The analysis variables include: the dip of the discontinuity (30°, 45°, 60°, 70°) and the angle between dip direction of slope face and discontinuity (0°~180°, step 10°). The change of the landslide behavior from the dip slope to anti-dip slope is attempted to describe with the quantitative indicators such as energy release of landslides, landslides volume, displacement magnitude, movement direction and impact area.
Based on the research results: (1) The unified analysis mode is constructed based on the synthetic rock mass which does not need to preset the failure mode, and it can simulate the landslide behavior of the dip slope to oblique slopes and anti-dip slope. The analysis results are reasonable with the general engineering experience. (2) The energy realese of landslides includes the mass of landslides and the fall distance, which is a good indicator to quantify the scale of the landslide events. The energy release of landslides is better than the safety factor which is obtained by the conventional limit equilibrium analysis to represent the risks and losses caused by the landslide events. (3) In this paper, the energy realese of landslides is used as the index that is attempted to establish the discontinuity orentation adjustment of rock slope engineering in the classification of RMR. (4) The impact area is based on digital terrain model which elevation can be used to describe the severity of the terrain change, and the terrain change can be divided into depletion area and deposition area. The impact area has richer and more comprehensive information content than the commonly used safety factor, traval distance, setback, and reach angle, that can improve rock slope stability and risk analysis tasks. |
