節理岩體滲透係數先天異向性及 應力引致異向性對岩坡穩定性之影響

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题名:	節理岩體滲透係數先天異向性及應力引致異向性對岩坡穩定性之影響
作者:	劉佳怡;Liu, Chia-Yi
贡献者:	應用地質研究所
关键词:	岩石邊坡穩定分析;擬連續體模式;FLAC 3D;滲透係數異向性;Rock slope stability;Continuum approach;FLAC3D;Anisotropic permeability
日期:	2023-07-24
上传时间:	2024-09-19 17:26:37 (UTC+8)
出版者:	國立中央大學
摘要:	針對屬於裂隙介質之節理岩體所形成的岩石邊坡，其節理所形成之複雜網路往往是地下水流的重要通道，因此其特性對岩石邊坡地下水滲流系統之影響需被進一步探討。根據前人研究發現節理位態分佈會使岩體滲透係數產生先天異向性，同時應力亦會影響不同位態節理之內寬變化，因而導致滲透係數產生應力引致異向性。於是本研究使用 FLAC3D 軟體建立岩石邊坡模型，透過擬連續體模式計算受到節理先天及應力引致異向性影響之節理岩體滲透係數張量，將計算結果代回岩石邊坡模型後，經滲流分析得到穩態孔隙水壓於岩石邊坡模型之分佈情形，最後利用剪力強度折減法進行邊坡穩定分析探討受節理特性影響之滲流異向性對岩石邊坡穩定性之影響。結果顯示在分析條件為均向應力下，當平行坡面之節理數量明顯多於垂直坡面之節理數量時，相較節理均向分佈情況，節理先天異向性會影響地下水流方向使孔隙水壓值有相對差異 28%，進而影響後續邊坡之安全係數；另外，在分析條件為節理均向分佈情況下，當最大主應力平行於坡面且明顯大於垂直於坡面之最小主應力時，會對平行於坡面之節理產生影響，因此與均向應力分佈情形相比孔隙水壓值有相對差異-6%，顯示應力引致滲流異向性會影響到邊坡孔隙水壓的分佈情形；綜合各分析條件結果，同時考慮節理先天異向性與應力引致之滲透係數異向性，與具有均質均向滲透係數之案例比較節點孔隙水壓值有相對差異-38%因此有較大安全係數。本研究探討不同分析條件下，節理特性對節理岩體滲透係數張量的影響，進而影響岩石邊坡之滲流系統，導致岩石邊坡穩定性受到影響，因此未來於岩石邊坡穩定性分析時，建議考慮節理特性對地下水滲流系統之影響。;In the case of rock slopes formed by jointed rock masses in fractured media, the complex network of joints often serves as a crucial pathway for subsurface water flow. As a result, understanding the characteristics of the joints and their impact on the groundwater seepage system in rock slopes requires further investigation. Previous studies have indicated that the orientations of joints induced inherent anisotropic permeability in the rock mass. Additionally, stress affects the variation in aperture of joints with different orientations, resulting in stress-induced permeability anisotropy. Hence, this study utilizes the FLAC3D software to construct a rock slope model, via continuum approach to calculate the equivalent permeability tensor of the jointed rock mass, accounting for both inherent anisotropy and stress-induced anisotropy. The computed results are then incorporated into the model, enabling the determination of the distribution of steady-state pore water pressure in the rock slope through seepage analysis. Ultimately, slope stability analysis was conducted to examine the impact of permeability anisotropy induced by joint characteristics on the stability of rock slopes. The results show that under isotropic stress conditions,when the number of bedding parallel joints was significantly more than the bedding perpendicular joints, inherent anisotropy of joints affected the direction of groundwater flow, resulting in a relative difference of -28% in pore water pressure distribution within the slope compared to the scenario of joint isotropy. This, in turn, affected the safety factor in subsequent slope stability analyses. Additionally, under the conditions of joint isotropy, when the maximum principal stress was parallel to the slope surface and notably greater than the minimum principal stress perpendicular to the slope surface, it influenced the joints parallel to the slope surface. Compared to the scenario of isotropic stress distribution, this led to a relative difference of -6% in pore water pressure distribution. These findings demonstrate that stress-induced affects the distribution of pore water pressure in slopes.Overall, this study explores the impact of joint characteristics on the permeability coefficient tensor of jointed rock masses, subsequently influencing the seepage system in rock slopes and the stability of rock slopes. Therefore, future analyses of rock slope stability should consider the influence of joint characteristics on the groundwater seepage system.
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