国家天文台500米口径球面射电望远镜台址球冠型边坡稳定性分析

An analysis of the stability of the spherical-cap shaped slope at the Five-hundred-meter Aperture Spherical radio Telescope(FAST),China

中国科学院国家天文台500米口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST)台址位于岩溶洼地内,开挖完成后的洼地边坡外形接近球冠型边坡,属于轴对称圆形凹坡,坡体由胶结的土石混合体和石灰岩组成,局部稳定性良好,整体稳定性有待评价。目前边坡整体稳定性评价通常采用基于平面应变假定的极限平衡法,由于未考虑边坡外形,该方法用于轴对称圆形凹坡稳定性的评价结果有偏差。为消除上述偏差,将轴对称圆形凹坡滑体划分为多个环形条块,考虑环形条块轴力的抗滑作用,提出了针对轴对称圆形凹坡的极限平衡法改进方法;并采用数值分析方法对改进后的简化Bishop法进行验证,结果表明改进后的简化Bishop法安全系数计算结果较未改进方法略有提高,与数值分析法结果基本一致。同时给出轴对称圆形凸坡的安全系数计算公式,计算结果表明圆形凸坡稳定性与直线形边坡较为接近。上述两种计算方法为类似外形的边坡稳定性评价提供了新的途径。

The site of Five-hundred-meter Aperture Spherical radio Telescope is located in karst depression,and the depression slope shape after excavation is like a spherical cap shape slope which belongs to an axisymmetric circular concave slope.The slope is composed of cemented soil-rock mixture and limestone.The slope is locally stable,but the stability of slope in a whole is still unknown.At present,evaluation of the slope stability in a whole is usually using the limit equilibrium method which is based on plane strain,and error arises in the evaluation results of the axisymmetric circular concave slope because of ignoring the slope shape.To eliminate the error,the slide body of the axisymmetric circular concave slope is divided into many annulus slices in the study,the antislide capacity of annulus slices axial force is considered and the improved limit equilibrium method which is suitable to the axisymmetric circular concave slope is proposed.The improved simplified Bishop method is verified with the numerical analysis method.The results show that the safety factor of the improved simplified Bishop method is a little larger than that with the traditional calculation method,and the safety factor of the improved simplified Bishop method is close to the numerical method result.The safety factor equation of the axisymmetric circular convex slope is given,and the results show that the stability of the axisymmetric circular convex slope is close to that of the ordinary slope.The above two calculation methods may provide new ways to evaluate the stability of slope with similar slope shape.