纤维加筋钙质砂力学特性与细观机理研究

Carbonate sand is the main filling material in the construction of the South China Sea. The outstanding particle crushing of carbonate sand results in an adverse influence on the engineering mechanical properties. This project aims to investigate the mechanical properties and meso-mechanical mechanism of fiber reinforced carbonate sand, and provide a scientific basis for the promotion and application of this efficient and easy reinforcement technology. In this project, based on the single-particle crushing test of carbonate sand, the single-particle crushing mode and the maximum crushing strength of carbonate sand will be obtained. Through the stretching test and corrosion resistance test of reinforced fiber, the tensile strength and durability of the reinforced fiber will be determined. Conducting pull-out test of reinforced carbonate sand, the interface friction mechanism of reinforced carbonate sand will be revealed, and the optimal combination of carbonate sand and fiber will be proposed. Through the oedometer, creep and triaxial tests of fiber reinforced and unreinforced carbonate sand, the compressibility, creep, shear strength and stiffness of carbonate sands with different types, lengths and contents fibers will be summarized, and the constitutive model of the fiber reinforced carbonate sand will be established. A lightweight triaxial test supported by X-ray CT scanning platform will be developed, combining with discrete element simulation of triaxial shearing process of fiber-reinforced carbonate sand, the mechanism of interaction between fiber deformation behavior and particle motion and particle breakage behavior of carbonate sand, evolution of force chain structure evolution and formation and development of shearing band will be studied, revealing the meso-mechanical mechanism of fiber-reinforced carbonate sand.

钙质砂是南海工程建设的主要填筑材料，其颗粒破碎明显，工程力学性质差，本项目旨在研究纤维加筋钙质砂的力学特性和细观机理，为这种新型简便的钙质砂加固技术的推广应用提供科学依据。本项目基于钙质砂单颗粒压碎试验，了解钙质砂颗粒的破碎强度和破碎模式；通过不同纤维的单向拉伸和耐腐蚀试验，明确加筋纤维的力学特性和环境适应性；开展纤维与钙质砂的拉拔试验，分析加筋纤维与钙质砂的界面摩擦性能，并提出纤维与钙质砂的优化组合；通过纯钙质砂和加筋钙质砂的侧限压缩、蠕变和常规三轴试验，掌握不同类型、长度和含量的纤维对钙质砂的压缩性、蠕变性、破碎性、变形和剪切性能的影响规律，并建立纤维加筋钙质砂的本构模型；开展纤维加筋钙质砂CT扫描支持下的轻型三轴试验，并结合其三维离散元模拟，研究纤维变形行为与钙质砂的颗粒运动和破碎行为、力链结构演化以及剪切带形成和发展过程之间的相互作用机制，揭示纤维加固钙质砂性能的细观力学机理。

研究纤维加筋钙质砂的力学特性和细观机理能为推广该新型简便的钙质砂加固技术应用提供理论基础。选取我国南海地区钙质砂为研究对象，基于钙质砂单颗粒压碎试验，根据颗粒受力曲线得到了钙质砂颗粒的破碎强度，确定了钙质砂颗粒的破碎过程可归纳为三种破碎模式。通过标准试验方法，研究了聚丙烯纤维加筋水泥基钙质砂试样的收缩性和抗渗性，以及在干湿循环条件下试样的抗压与抗折强度变化规律。基于直剪试验，探讨了不同长度、含量和种类的纤维对加筋钙质砂剪切特性的影响规律。基于数值模拟，在纤维加筋钙质砂剪切过程中，从剪切带内颗粒的运动行为、接触组构、力链结构和能量耗散等方面深入揭示加筋钙质砂局部剪切破坏和剪胀行为的微观力学机理。期待对纤维加筋钙质砂力学特性的把握、本构模型的建立和实际工程的应用提供强有力的科学理论依据。