FAST大型岩溶洼地场地岩土治理关键技术研究

Key techniques in geotechnical treatment of a large karst depression for FAST

FAST(500m口径球面射电望远镜)选址于大型岩溶洼地,洼地的工程地质和水文地质条件极为复杂,台址开挖制约因素多并相互交叉影响,技术难度大,岩土治理具有独特性和开创性,该课题取得如下创新性成果:①建立大型岩溶洼地开挖中心多目标多属性优化决策的分析确定方法,求解出性能最佳、造价最低、地质危害最小的开挖中心空间坐标;②针对含有较大粒径的岩堆,基于离散元计算结果,提出岩堆主动土压力的计算方法,并提出适用于山区的岩堆整体补强加固结构;③针对大型岩溶洼地边坡外形特点,分析凸坡、凹坡的稳定性及影响因素,并分析望远镜下拉索拉力作用对球冠形边坡稳定性的影响;④针对两处裂隙发育强烈的超高岩质边坡的静动力稳定性进行离散元模拟,根据所揭示出的破坏模式提出相应的加固措施;⑤根据FAST洼地的地貌特征,采用人工泄水隧道与天然岩溶管道流相结合的排泄系统,建立起大型岩溶洼地综合防洪、排水系统,有效地降低地表水、地下水对FAST工程的影响。课题成果在FAST工程中得到全面的成功应用,为射电望远镜国家科研重大基础设施建设的顺利实施提供重要支撑。

FAST(five-hundred-meter aperture spherical telescope) is constructed in a large karst depression with very complex geological and hydraulical conditions. Despite immense difficulties in geotechnical engineering,great success has been achieved with a number of novelties:(1) a method is proposed to identify the optimal coordination of the excavation center, which leads to a minimum construction cost as well as minimum impact on environment;(2) a new retaining structure supporting rock blocks is adopted, with a method being proposed to calculate the active earth pressure of rock blocks based on DEM simulation;(3) the influence of slope shape on its stability is analyzed using FEM strength reduction method, and the influence of cable tension on the slope stability is also investigated;(4) the static and dynamic stability of two super-high rock slopes is analyzed using UDEC, based on which proper remediation work is taken;(5) based on the geological and hydraulical conditions of the karst depression, a drainage tunnel is constructed to prevent flooding along with the natural karst pipeline flow. These achievements have been used successfully in FAST, which can provide reference for the construction of Chinese telescope infrastructure.