土工合成材料加筋土复合体判别准则及其力学特性的分析理论研究

Geosynthetic reinforced soil (GRS), consisting of alternating layers of reinforcement and compacted soil mass, tend to behave as a composite material when the geosynthetic reinforcement was closely spaced. GRS structures have gained increasing popularity both in China and abroad. However, there is still lack of scientific criterion regarding the GRS composite. The current analytical methods could not fully elucidate the interactive behavior between the soil and geosynthetic reinforcement and the GRS composite behavior. One of the major concerns in the current project is to establish the criteria for GRS composite based on the influencing extent and spatial distribution of the reinforcement through a series of plane strain tests as well as particle flow simulation. In addition, large-scale triaxial tests will be conducted to investigate the mechanical characteristics of GRS composite and the relationship with the material properties, spacing and soil-reinforcement interfacial properties. And on this basis, the improved equivalent additional stress method for evaluating the composite behavior of GRS would be proposed. Thirdly, loading tests of GRS retaining walls will be carried out using centrifuge modelling techniques referring to the prototype of GRS abutment. Influencing factors including reinforcement spacing, reinforcement stiffness and backfill compactness will be taken into consideration regarding to the load-deformation characteristics and failure mode of GRS composite. Analytical model for predicting the behavior of a GRS mass would also be provided. Findings of this research project will lead to deep understanding of the GRS composite and lay a theoretical foundation for the further development of its structural design and numerical simulation method.

土工合成材料加筋土是由加筋材料与压实填土交替铺设而成的组合体，当加筋层间距较小时，表现出明显的复合力学特性，工程应用非常广泛。目前缺少加筋土复合体的科学判别依据，现有分析评价理论也与实际情况存在差距。针对这些问题，本项目拟通过加筋土平面应变试验和颗粒流仿真等手段，揭示加筋作用的影响范围、空间分布规律及主要影响因素，建立加筋土复合体判别准则；通过加筋土复合体的大型三轴试验研究，获得加筋土复合体的力学性能与材料特性、层间距和筋土界面性质之间的关系，完善加筋土的等效附加应力分析方法；以加筋土桥台为背景，利用离心模拟技术进行加筋土体载荷试验和数值模拟，分析层间距、筋材刚度、填土密实度等对加筋土体的承载-变形特征、破坏模式的影响及其规律，建立加筋土体承载力和变形量的分析评价模型。本项目的研究将极大地深化人们对土工合成材料加筋土体复合性能的认识，为加筋土复合体结构设计和加筋土体数值分析奠定理论基础。

土工合成材料加筋土技术已在交通、水利和建工等工程领域得到了广泛应用。在研究和实践中人们发现，当加筋层间距较小时，加筋土体表现出明显的复合体特征，具有极高的承载能力，可以用于桥台或地基等承重工况，服务于我国高质量基础设施建设。但目前仍缺少加筋土复合体的科学判别依据，分析理论和方法仍沿用传统加筋土挡墙的做法，存在明显缺陷。本项目针对这些科学问题，通过土工合成材料加筋土平面应变试验和颗粒流仿真等手段，研究了加筋作用的影响范围、空间分布规律及其主要影响因素，用以建立加筋土复合体的判别准则；采用叠环剪切仪开展了筋土相互作用试验，并通过加筋土复合体的平面应变试验，研究加筋土复合体的力学性能与材料特性、层间距和筋土界面性质之间的关系，用以完善加筋土的等效附加应力分析方法；以加筋土桥台为背景，正在利用离心模拟技术进行加筋土体载荷试验和数值模拟，用以分析加筋层间距、筋材刚度、填土密实度等对加筋土体的承载-变形特征、破坏模式和极限承载力的影响及其规律，建立加筋土体承载力和变形特性的评价模型。通过本项目的开展，在深刻认识加筋作用对土体约束作用的基础上，建立了新的土工合成材料加筋土复合体强度计算理论和方法；考虑筋-土界面相对位移及其剪胀特性，建立了适用于不同边界条件下的筋材轴力分布计算模型，明确了土工合成材料加筋作用的影响范围，建立了用于模拟加筋土复合体的等效附加应力计算模型，并开发了加筋土复合体数值分析模块。由于离心机试验平台需排队等待，加筋土桥台离心模型试验正在进行，后续将基于试验结果进一步完善加筋土桥台极限承载力的评价理论和方法。本项目的研究深化了人们对土工合成材料加筋土体复合性能的认识，为加筋土复合体结构设计和加筋土体数值分析奠定了理论基础。