滨海相软土场地形成的水泥土桩竖向工作荷载条件下承载性状演化过程研究

The cement-soil pile is widely used in the treatment of marine soft soil or marine fill soil foundation, but the surface strength could degrade in the corrosive soil, which will affect the service life of cement-soil pile. By researching the cement-soil pile formed in marine soft soil sites, the evolution process of its bearing characteristic under vertical working load is revealed and the long-term bearing capacity can be forecasted. The research methods include laboratory model test, chemical analysis, numerical simulation and theoretical analysis. The evolution process of bearing characteristics of Cement-soil pile formed in marine soft soil site could be changed caused by the erosion of erosive ion, which is the main feature of this application project. In this paper，the main contents include: the establishment of the indoor accelerated degradation test method (the equivalent relationship between the erosive ion concentration and the time when the same degree of deterioration is achieved), the strength characteristics of deteriorated cement-soil pile and the prediction and verification of the long-term strength based on the theory of the composite material strength, the evolution law of cement-soil pile bearing characteristic in the process of deterioration. the prediction and verification of pile-soil interaction mechanism and support force of the soil against the pile under vertical working load condition. The assessment method on durability of the cement-soil pile in site of marine soft soil is proposed. The results of research can provide not only the basis for engineering design, but also certain theoretical significance. The ideas and methods in the research can be used as references in the study of the deterioration of the solidified body formed in the corrosive sites such as saline soil.

水泥土桩在我国滨海相软土或海洋吹填土地基处理中应用广泛，但其在腐蚀地基土中会发生表层强度降低的劣化现象，劣化的发生将影响水泥土桩的使用寿命。拟以滨海相软土场地形成的水泥土桩为研究对象，揭示其在竖向工作荷载条件下承载性状演化过程并预测其长期承载力。研究手段有室内模型试验、化学成分分析、数值模拟和理论分析。研究场地形成的水泥土桩，在竖向工作荷载条件下，由于场地中侵蚀离子导致水泥土桩劣化而引起的承载性状变化问题是申请项目的主要特色。主要研究内容包括，确立室内加速劣化试验方法（建立达到相同劣化程度时侵蚀离子浓度与侵蚀时间的等效关系）；劣化水泥土桩桩身强度特性及基于复合材料强度理论的长期强度预测与验证；劣化水泥土桩承载性状演化规律及机理、长期承载力的预测与验证。研究成果可为工程设计提供依据，并具有一定的理论意义。申请项目采用的研究思路和方法可为盐渍土等腐蚀场地形成的加固体的劣化问题的研究提供参考。

本项目以滨海相软土场地形成的水泥土桩为研究对象，研究场地形成的水泥土桩，在竖向工作荷载条件下，由于场地中侵蚀离子导致水泥土桩劣化而引起的承载性状变化问题。主要研究内容有确立室内加速劣化试验方法，并利用该方法分析水泥土劣化特性及机理，明确劣化水泥土桩桩身强度特性及长期强度预测，结合模型试验分析竖向工作荷载条件下劣化桩承载性状演化过程及桩土相互作用机理，对劣化水泥土桩承载特性及长期承载力进行预测及验证。主要研究成果包括：建立达到相同劣化程度时侵蚀离子浓度与侵蚀时间的等效关系，确立室内加速劣化试验方法，并使用该方法研究劣化水泥土桩，明确劣化水泥土桩桩身强度特性，建立长期强度预测方法；依据水泥土劣化特性，设计模型试验研究，阐明竖向工作荷载条件下劣化桩承载性状演化过程及桩土相互作用机理；提出劣化水泥土桩桩土相互作用承载力计算方法，并结合竖向工作荷载条件下劣化桩承载性状演化过程研究成果，建立劣化水泥土桩长期承载力预测式，设计相关计算软件，提出化水泥土桩长期承载力计算方法。研究成果可便于设计人员根据现场环境参数快速判定地基承载力，方便设计地基加固方法，另一方面，施工人员也可使用该程序判定地基状态，保证施工安全。此外，本项目采用的研究思路和方法还可为盐渍土等腐蚀场地形成的加固体劣化问题的研究提供参考。