基于颗粒破碎的珊瑚礁钙质砂土液化机理研究

Coral reef which contains abundant marine ecological resources has great significance on human living environment, resource development and national defense strategy. Calcareous soils, the sediment of coral reef, shows special dynamic liquefaction characteristics in the process of particle breakage, which has significant influence on project construction. This propsed research takes coral reef calcareous soils of the atoll of Nansha Islands and the fringing reef around the Northern South China Sea as research objects. The following objectives of this proposed research project include:1) It centers around that particle breakage leads to particle grade restructring and then adjusts liquefaction potential of coral reef calcareous soils, and makes use of in-situ test, laboratory soil test, physical model test and theoretical analysis and so on. In this way, it reveals the liquefaction characteristics,law of strength and deformation of coral reef calcareous soils, as well as the mechenism of interaction between pile and calcareous soils under the action of the static and dynamic loading or water-level-fluctuation; 2) Also it researches the microcscopic mechanism of how particle breakage of calcareous soils causes changes of particle grade restructuring, and therefore explains the dynamic changing mechanism of liquefaction strength; 3) The liquefaction mechanism and engineering mechanics effects of coral reef calcareous soils which takes particle breakage and anisotropic into consideration will be presented. The research findings will further improve the country cognitive level about such a special geotechnical medium. The defensive strategies in the Sourth China Sea, the scientific understanding of coral reef engingeering geology aspects, and ocean engineering construction, all can greatly benefit from the implementation of the proposed research results.

蕴藏着丰富海洋生态资源的珊瑚礁对于人类生存环境、资源开发利用、领土主权维护等意义重大，其沉积物钙质砂土在颗粒破碎过程中表现出特殊的动态液化特点，给工程建设带来了极大影响。本项目以南海珊瑚环礁及其北部岸礁所赋存的钙质砂土作为比对研究对象，以"颗粒破碎导致级配重组进而调控珊瑚礁钙质砂土的动力响应特性"作为研究主线。综合运用现场原位测试、室内土工试验、物理模型试验、理论分析等技术手段，揭示动静荷载及水位波动下珊瑚礁钙质砂土的液化特性、强度变形规律及桩基-钙质砂土相互作用机理；探究钙质砂土颗粒结构破碎引发级配重组的微观定量描述方法，进而诠释其宏观动力学特性表现下的微观机制，最终提出基于颗粒破碎引发级配重组的珊瑚礁钙质砂土液化机理及其工程力学效应。项目着力解决如何改善工程建设过程中由于颗粒破碎导致钙质砂土动态液化的关键科学问题，对完善海洋工程地质学科及推动海洋工程建设有着重要的科学意义和实用价值。

紧紧抓住我国南海吹填岛礁工程建设契机，深度开展军民融合，紧密围绕南海吹填岛礁工程建设面临的关键技术难题，通过开展现场平板载荷试验、标贯试验、动探试验、旁压试验和扁铲侧胀等现场原位测试，分析了不同含水条件和颗粒级配下钙质砂土的承载特性与液化潜势；针对动、静荷载方式，对比研究了钙质砂土动力特性循环扭剪三轴、共振柱试验结果，辅以声发射手段定量揭示了剪切破坏过程中钙质砂土颗粒破碎及级配重组规律；基于钙质砂土颗粒破碎的桩—土相互作用物理模型试验，揭示了钙质砂土微观破碎演化和液化发展规律，提出了适合于钙质砂土颗粒破碎的液化破坏标准；并对颗粒易破碎和各向异性的钙质砂土抗液化势微观机理进行分析，提出了钙质砂土液化机理及其工程力学效应。. 在南海岛礁工程建设中，钙质砂土抗液化动力特性、原位测试的力学参数指标等方面的研究成果，对岛礁工程建设中地基处理方法优化和处理效果评价起到了关键科技支撑作用。比如基于珊瑚礁砂一定条件下可液化和具有抗液化特性，创造性提出珊瑚砂地基的饱和冲击碾压工艺，有效指导现场施工；通过现场和室内平板载荷试验和动力触探试验，建立了承载力与动探击数关系，提出简易的地基处理效果评价方法和指标，解决了岛礁建设现场施工过程中的参数确定难题等。针对吹填岛礁现场施工关键技术问题开展专题研究，解决了现场施工过程中面临的技术难题，在珊瑚礁砂填筑性能、吹填地基处理效果评价等方面取得了一系列创新性成果，获得中国人民解放军HJ工程技术管理办公室、工程建设单位的高度认可和积极评价，为我国南海吹填岛礁决策、珊瑚礁砂地基处理方法优化和效果评价等提供了技术支撑。. 下一步项目组将对作为珊瑚礁主体的礁灰岩岩体特性开展研究，为岛礁地下工程开发和海洋强国战略实施、以及引领带动一带一路沿线珊瑚礁国家基础设施建设提供更好的科技支撑。