基于极限平衡法的金川泄洪洞稳定性分析

以金川水电站泄洪洞进口边坡稳定性分析为目标,基于三维极限平衡法,考虑金川水电站泄洪洞进口边坡附近的四组优势结构面之间不同组合形式和不同排列次序,利用赤平投影原理对优势结构面进行定性分析并利用极限平衡法进行定量分析;基于二维极限平衡理论和方法,对泄洪洞进口边坡在开挖、蓄水、蓄水+暴雨+设计地震、蓄水+暴雨+校核地震4种工况下的稳定性进行分析。计算结果表明,三维稳定性分析中楔形体按倾向和倾角分别为336°∠60°、75°∠33°和237°∠65°的结构产状组合时,所产生的楔形体在开挖、饱水、设计地震、校核地震四种工况下的安全系数最低达到1.90,但仍符合设计规范要求。二维稳定性分析中,在蓄水+暴雨+校核地震工况下,边坡安全系数最低达到1.368,开挖扰动后变形体的强度能满足工程要求。对比两种分析方法,三维稳定性分析得出的安全系数均大于二维稳定性分析得出的安全系数,说明二维极限平衡法计算的结果更加偏于安全,但是同时也会增大工程的造价。

Limit equilibrium method-based stability analysis on spillway tunnel of Jinchuan Hydropower Station

Targeting at the analysis on the stability of the slope at the inlet of the spillway tunnel for Jinchuan Hydropower Station，the dominant structural planes therein are qualitatively analyzed with the principle of stereographicprojection and quantitatively analyzed with the limit equilibrium method under the consideration of various combination types and various rankingorders among four sets of the dominant structural planes near the slope at the inlet of the spillway tunnel，while the stabilities of the slope under the four working conditions，i. e. excavation，water impoundment，water impoundment + rainstorm + design earth quake and water impoundment + rainstorm + maximum credible earthquake ( MCE) ，are analyzed as well. The calculation result shows that when the wedge-shaped bodies in the 3 － D stability analysis are the structural occurrence combinations of 336°∠60°， 75°∠33° and 237°∠65° respectively in accordance with their dip directions and dip angles，the safety coefficients of the wedgeshaped bodies created therein are lowered to the minimum of 1. 90 under the working conditions of excavation，saturation，design earthquake and maximum credible earthquake ( MCE) ，but they are still accorded with the relevant design criteria. In the 2 － D stability analysis，the slope safety coefficient is lowered to the minimum of 1. 368 under the working condition of water impoundment + rainstorm + maximum credible earthquake ( MCE) ，while the strength of the deformed body after excavation disturbance can meet the engineering requirement concerned. Comparing both the analysis methods，all the safety coefficients got from the 3 － D stability analysis are larger than those got from the 2 － D stability analysis，which indicates that the result from the calculation made by 2 － D limit equilibrium method is not only apt to be more safe，but is also to increase the construction cost simultaneously.