吹填珊瑚砂快速固结特性与地基稳定性研究

Generally, due to the characteristics of low bearing capacity and high compressibility, terrigenous dredger soil can’t be used directly for engineering foundation and it should be treated. The consolidation process takes a long time following with large settlement after construction. However, calcareous dredging soils have the advantages of high bearing capacity, low compressibility, good permeability and quick consolidation after dredging as a result of the closely spaced particles caused by the hydraulic sorting, washing and seepage effects. Therefore, there are significant differences between the self-compacting effect of calcareous dredging soils and the characteristics of terrigenous dredger soil. . This study focuses the great coral reef project in the South China Sea, aiming to solve the engineering problems in the dredging and foundation treatment projects. The characteristics of particle size, shape and density of dredging calcareous soil will be analyzed through integrated research methods consisting of field geological investigations, sampling, in situ testing, laboratory experiments, statistical analysis and theoretical analysis; The effects on mechanical properties will be discussed. Consolidation efficiency will be studied under the seepage and self-compacting effects. The compacting effect of hydraulic dredging will be simulated through simulation test. The longtime stability of calcareous dredging soils will be studied and settlement calculation method should be proposed. This study is theoretically innovative and the results will provide scientific guidance for ground treatment and engineering design on coral reefs.

陆源吹填土因含水量高、排水时间长、压缩性高而不能直接用作建筑物地基，必须进行加固处理，且工后沉降时间长、沉降量较大；而吹填珊瑚砂地基在水力吹填时因水流冲击、水力分选和渗流作用使土颗粒紧密排列，同时因透水性好、排水快而具有承载力高、压缩性低和固结快的优点。事实上，珊瑚砂的快速固结效应与陆源吹填土有显著差别。. 本项目瞄准国家珊瑚礁重大工程，紧密结合当前珊瑚礁吹填施工和地基处理工程的实施，通过现场调查、取样、原位测试、室内实验、现场大量测试数据的统计分析和理论研究相结合的方法，分析吹填珊瑚砂的颗粒形状、级配、密实度对地基承载力和沉降的影响规律，研究吹填珊瑚砂地基在渗流密实和自重作用下的排水固结效率；通过室内模拟试验验证珊瑚砂的水力密实特性，以理论分析研究吹填珊瑚砂地基的长期稳定性，确定地基沉降计算方法和计算参数。本项目的研究结果将为珊瑚礁地基处理和工程设计提供科学指导。

近年来，我国在南海岛礁进行大规模吹填造岛工程。吹填造岛是将礁坪或泻湖中的珊瑚砂和礁石吹填到礁坪上，从而形成人工岛。由于缺乏相关的工程经验，专家们根据陆地吹填土地基的工程经验，提出各种地基处理方法来提高吹填珊瑚砂地基的强度。本项目通过揭示吹填珊瑚砂地基快速固结与地基稳定性这一关键科学问题，首先通过超景深三维显示系统和高精度光学干涉仪，分析珊瑚砂颗粒形状及表面微观形态；结合室内单元试验，通过不同制样方法模拟珊瑚砂在不同地基处理方法中形成的初始结构，研究试样初始结构的各向异性对珊瑚砂应力应变关系、峰值强度、临界状态强度和压缩特性的影响；利用现场监测和原位测试，揭示不同地基处理方法对吹填珊瑚砂地基承载力及变形特性的影响；结合数值模拟，计算吹填珊瑚砂地基沉降稳定性。研究成果可以为吹填珊瑚砂地基的处理方法、检测方法和检测指标提出合理化建议。