以3DEC模擬降雨入滲引致岩坡破壞與孔隙水壓變化之初步研究－以數值模型為例

A Preliminary Study on Rainfall Infiltration Leading to Rock Slope Failure and Pore Pressure Variation through Physical Models Simulated using 3DEC

10.29417/JCSWC.202303_54(1).0001

姚智瀛(Chih-Ying Yao)；賴宇森(Yu-Sen Lai)；羅佳明(Chia-Ming Lo)

降雨入滲 ； 岩石邊坡 ； 數值模型 ； 孔隙水壓 ； 岩體滑動 ； infiltration ； rock slope ； numerical model ； pore pressure ； rock slide

中華水土保持學報

54卷1期（2023 / 03 / 01）

1 - 15

繁體中文;英文

本研究主要應用離散元素法數值軟體3DEC 5.2模擬並探討降雨入滲影響岩石邊坡破壞過程與其破壞過程中之弱面內孔隙水壓變化特性。其數值模型係透過3DEC建構兩組岩石邊坡，第一組數值幾何模型為長寬約10 m且層面為15°之簡化順向坡，另假設坡頂一處張裂縫提供降雨入滲起點；第二組數值模型則在第一組模型增加傾角為75°之弱面（節理），並使降雨均勻於坡面入滲致岩坡內。模型初步將岩體假設為彈性介質，基質與弱面均初步選擇庫倫摩擦準則，並於岩坡冠部或坡面設置水壓表示降雨入滲起點，分別採用單向耦合（One-way Coupled）與雙向耦合（Two-way Coupled）方式模擬。模擬顯示雙向耦合之結果更為理想，過程中地表水自頂部弱面入滲並累積孔隙水壓於岩坡內部，其在水壓力達一定值時岩坡將產生破壞，破壞後擴大之弱面將使得水壓消散，而岩體持續變形至滑動過程中水壓亦隨之變化，最終可能引至更大規模之岩體滑動。

In this study, the discrete element method numerical software program 3DEC 5.2 was applied to simulate and analyze the effects of rainfall infiltration on the failure process of rock slopes and the pore pressure variation in the plane of weakness during the failure process. This study constructed two sets of rock-slope numerical models using 3DEC. The first numerical model had a simplified dip slope of approximately 10 m in length and width and 15° in dip angle. The tension crack at the top of the slope was assumed to provide a starting point for rainfall infiltration. In the second numerical model, a plane of weakness with a dip angle of 75° was added to the first model, allowing the rainfall to evenly infiltrate into the slope. In the model, rocks were assumed to be elastic, and the Mohr-Coulomb joint constitutive model was used. This study set water pressure at the crown of the slope or slope surface as the starting point of rainfall infiltration and then used a two-way coupling method for simulation. The simulation results indicate that surface water infiltrates from the top, and that pore pressure accumulates inside the rock slope and the rock slope fails when the water pressure reaches a certain value. The expanded plane of weakness after failure allows the pore pressure to dissipate, and the pore pressure changes during the continual deformation of the rock and sliding, which may eventually cause a large-scale rock slide.

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