基于劈裂-压密模式的含黏性土砂层注浆机理研究

Fracture- compaction mode is the main grouting mode in grouting engineering projects for clayey sand. However, current sand grouting design method is based on permeation mode, which is hard to guide grouting design in clayey sand. In this project, many research methods, such as theoretical analysis, laboratory test and physical simulation test, will be adopted to study fracture- compaction grouting mode in clayey sand. Based on laboratory tests of sand injectability and fracturing critical condition, occurrence conditions of fracture- compaction grouting mode will be acquired. To study interfacial stress coupling effect between grout flow and sand compaction deformation, new algorithm for calculating grouting process will be developed. Spatial shape characteristics of grouted body will be analyzed which is composed of grout vein, compacted sand and original sand. Fracture-compaction grouting diffusion law will be revealed. Growth of clayey sand performance originated from compaction effect will be tested. Equivalent calculation method for performance parameters of fracture- compaction grouted body will be studied and put forward. Based on analysis of anisotropy and spatial attenuation characteristics of performance of grouted body, synergistic reinforcement mechanism of grout vein and compacted sand will be revealed. Research results are helpful to complement sand grouting theory, and provide the theoretical basis for fracture- compaction grouting design in clayey sand.

在含黏性土砂层注浆工程中，劈裂-压密模式是其主要注浆模式，而目前的砂层注浆设计理论大多基于渗透模式，难以适用于含黏性土砂层的注浆设计。本项目拟采用理论分析、室内试验和物理模拟试验相结合的方法，针对含黏性土砂层劈裂-压密注浆模式开展研究。基于多因素全面注浆试验，研究砂层渗透可注性条件与注浆起劈条件，建立劈裂-压密注浆模式的发生判据；研究浆液流动与砂层压密变形之间的界面应力耦合效应，开发注浆扩散过程迭代算法，分析单一序次与多序次浆脉的空间形态特征，揭示含黏性土砂层劈裂-压密注浆扩散规律；研究压密效应对含黏性土砂层性能的强化作用，提出劈裂-压密注浆加固体宏观性能指标的等效计算方法，分析注浆加固体性能的各向异性与空间衰减特征，揭示浆脉骨架与压密砂层的协同加固机制。研究成果有助于补充和完善砂层注浆控制理论，为含黏性土砂层劈裂-压密注浆设计提供理论依据。

在含黏性土砂层注浆工程中，劈裂-压密模式是其主要注浆模式，而目前的砂层注浆设计理论大多基于渗透模式，难以适用于含黏性土砂层的注浆设计。本项目拟采用理论分析、室内试验和物理模拟试验相结合的方法，针对含黏性土砂层劈裂-压密注浆模式开展研究。基于多因素全面注浆试验，获得了砂层渗透可注性条件与注浆起劈条件，建立了劈裂-压密注浆模式的发生判据；研究了浆液流动与砂层压密变形之间的界面应力耦合效应，开发了注浆扩散过程迭代算法，分析了单一序次与多序次浆脉的空间形态特征，揭示了含黏性土砂层劈裂-压密注浆扩散规律；研究了压密效应对含黏性土砂层性能的强化作用，提出了劈裂-压密注浆加固体宏观性能指标的等效计算方法，分析了注浆加固体性能的各向异性与空间衰减特征，揭示了浆脉骨架与压密砂层的协同加固机制。研究结果表明：黏性土含量是影响砂层压密特性的主控因素，当黏性土含量低于25%左右时，砂层压缩过程中会形成砂骨架，砂层整体可压缩性较差；砂层注浆起裂方向与劈裂通道扩展方向均与大主应力方向一致，浆脉厚度在浆脉扩展方向上存在明显衰减；劈裂-压密注浆对劈裂通道两侧砂层的影响范围非常有限（20~40cm）。劈裂-压密注浆加固体性能各向异性显著，平行浆脉方向的抗变形能力要优于垂直浆脉方向，但抗剪性能及抗渗性能均弱于垂直浆脉方向，平行浆脉方向的粘聚力与渗透系数是劈裂-压密注浆效果的两个短板；注浆压密作用可显著提升砂层的各项性能指标，在2MPa注浆压力的压密作用下，砂层压缩模量增长了6~10倍，粘聚力增长了40~110kPa，内摩擦角提高了12~15°，渗透系数降低了2~5个数量级；砂层黏性土含量的增加可有效弥补砂层劈裂-压密注浆加固体性能的两个短板，当砂层黏性土含量小于临界黏性土含量时，砂层无法通过劈裂-压密注浆方式进行有效加固。研究成果有助于补充和完善砂层注浆控制理论，为含黏性土砂层劈裂-压密注浆设计提供理论依据。