南沙群岛永暑礁西南部珊瑚礁动力稳定性分析评价

Analysis and evaluation of dynamic stability of coral reef in the southwest of Yongshu Reef in Nansha Islands

鉴于珊瑚岛礁海洋工程地质体及钙质砂动力力学特性的特殊性,其在复杂海域环境下的抗震安全评价问题不容忽视。文中以永暑礁西南部珊瑚礁为研究对象,基于GEO-Studio分析平台建立了珊瑚岛礁抗震分析计算模型,细致模拟了礁体的几何分布形态,并引入等价线性法考虑岛礁钙质砂的非线性动力特征,开展了强震及波浪等静动力荷载作用下的联合分析,对岛礁的稳定性、动力响应以及液化特性进行了综合评价。计算结果表明:内外礁坡的地层构造对岛礁整体稳定性有显著影响,可能会发生滑坡等失稳现象;岛礁的地形有可能导致加速度响应的放大效应存在显著的差异;局部中粗砂和粉细砂层液化带液化程度较明显,但相对岛礁整体液化程度小。同时也验证了所建立抗震分析模型的合理可靠性。

In view of the particularity of the dynamic mechanical characteristics of coral island and reef marine engineering geological bodies and calcareous sand,the seismic safety evaluation of coral islands and reefs in complex sea environment can not be ignored.In this paper,taking the coral reef in the southwest of Yongshu Reef as the research object,the seismic analysis and calculation model of the coral reef is established based on the GEO-Studio analysis platform,and the geometric distribution of the reef is simulated in detail.The equivalent linear method is introduced to consider the nonlinear dynamic characteristics of calcareous sand in the reef,and the joint analysis under static and dynamic loads such as strong earthquake and wave is carried out,and the stability,dynamic response and liquefaction characteristics of the island and reef are comprehensively evaluated.The calculation results show that the stratigraphic structure of the inner and outer reef slope has a significant influence on the overall stability of the island and reef,and the instability phenomena such as landslides may occur,and the topography of the island and reef may lead to a significant difference in the amplification effect of acceleration response.The liquefaction degree of local medium coarse sand and silty fine sand layer is obvious,but the liquefaction degree of island reef is smaller than that of island reef as a whole.At the same time,the reasonable reliability of the seismic analysis model is verified.