考虑颗粒破碎效应的强夯有效加固范围研究

Particle breakage can be obviously observed during strengthen the coarse filling foundation by dynamic compaction. However, studies seldom consider the effect caused by particle breakage and then result in difficulties to determine the improvement area and reveal the reinforcement mechanism of dynamic compaction. This project aims at establishing a calculation method to determine the area of improvement by dynamic compaction, with which the particle breakage is considered. Firstly, a laboratory testing system will be established during which the dynamic compaction process can be observed. Detection techniques including CT scanning and DIC image analysis will be adopted to clarify the micro-dynamic response of soil under dynamic compaction. The reinforcement behavior and mechanism from hammer weight and drop distance will be studied and a new assessment index of improvement area will be proposed. Secondly, based on the real data of particle breakage, a discrete element program to simulate the particle breakage process will be developed and numerical study of dynamic compaction will be carried out subsequently to clarify the relationship between degree of breakage, dynamic response of soil, and reinforcement effect. The result will be used to reveal the affecting mechanism of particle breakage on the efficiency of dynamic compaction, determine the relationship between the degree of breakage and the new assessment index. Finally, the mathematic relationship between the area of improvement and the new assessment index can be defined by particle traversal technique and measurement element method. The outcomes of this project will not only provide a scientific basis for the further theoretical research and reinforcement mechanism of dynamic compaction but also benefit for the application and technology upgrade for dynamic compaction practice.

在对粗粒土填方地基强夯过程中，填料往往会发生明显的颗粒破碎。已有研究对颗粒破碎的影响考虑不足，给强夯有效加固范围的确定和全面认识强夯物理力学过程带来困难。本项目以建立考虑颗粒破碎效应的强夯加固范围计算方法为研究目标，首先构建可再现强夯过程的室内模拟和测试系统，利用CT扫描、DIC图像分析等技术明确强夯作用下土体微细观动力响应规律，揭示锤重和落距对加固土体作用机理，提出评价强夯加固范围的新指标。然后，基于真实颗粒破碎数据，开发模拟颗粒破碎现象的离散元程序并开展强夯过程数值计算，明确破碎程度-土体动应力响应规律-加固效果内在联系，揭示颗粒破碎对强夯加固效果影响机制，确定破碎程度与评价指标内在联系。最后，利用颗粒遍历技术和测量元方法，明确强夯加固范围-新指标数学关系。研究成果不仅可以为进一步开展强夯理论研究和全面揭示强夯加固机理提供科学依据，也可以为强夯工程实践和技术升级提供参考。

在利用强夯法处治碎石填料过程中，碎石填料往往会发生颗粒破碎现象。而已有研究对颗粒破碎的影响考虑不足，给强冲击作用下土体力学性能分析及强夯施工设计带来挑战。项目从更全面认识强夯物理力学过程出发，综合运用室内试验、数值模拟和理论分析，旨在建立考虑颗粒破碎效应的强夯加固效果预估方法。项目首先研发了室内强夯冲击加载测试系统，实现了多种方式冲击加载，集合DIC数字图像处理和多维传感系统，可实时获取冲击应力、土内应力波、土体宏细观响应等数据，结合开展的系列室内强夯试验，全面获取了不同夯击方式作用下土体多尺度响应规律。结合离散元数值方法和阿波罗填充理论，开发了颗粒破碎仿真模型，模型满足质量受荷并克服了局部应力集中问题；将颗粒破碎模型嵌入强夯过程，探究了冲击作用-颗粒破碎特征-土体多尺度响应规律内在关联，探明了锤重和落距对加固土体贡献差异和表征方法，并提出了计算强夯有效加固深度的新方法。最后，将冲击过程简化为弹簧-阻尼模型，建立了夯锤冲击加载过程时域模型，提出了夯沉比的修正方法，可为确定最佳夯击次数提供有益参考。所得成果可为进一步研究冲击作用下粗粒土破碎密实机理及强夯工艺优化提供科学支撑。