非饱和固化淤泥的力学特性及其本构关系研究

Focusing on the hot topic of sludge disposal problem in geoenvironmental engineering, the strength and deformation of the unsaturated solidified sludge are chosen as the research objects. A series of laboratory tests and theoretical investigations are performed to reveal the mechanical behaviors of unsaturated solidified sludge. The mechanism associated with the mechanical behavior of the solidified sludge resulting from cementation and matric suction is examined. A constitutive model for unsaturated solidified sludge is proposed. The consolidation tests, unconfined compressive strength tests and triaxial tests for unsaturated solidified sludge with different material mixing ratios and matric suctions are conducted. The effects of cementation and matric suction on the compressibility behaviors, yield stress, shear strength are studied. The strength and deformation behaviors of the unsaturated solidified sludge under cementation coupled with matric suction are investigated in a systematic level. On the basis of experimental data, an elasto-plastic constitutive model coupling the effect of cementation and matric suction is proposed within the framework of Barcelona Basic Model for unsaturated soils by introducing the subloading concept. The evolution of an apparent over-consolidation ratio is employed to capture the destructuring during loading. The research conducted herein has an obvious significance at the aspects of science and practice for design of new geotechnical structures and prevention of natural disasters.

本项目立足岩土工程和环境工程交叉领域热点关注的淤泥处置问题，以非饱和固化淤泥的强度和变形为研究对象，通过系统的试验研究和理论分析，揭示固化淤泥在胶结和基质吸力共同作用下的基本力学特性及其协同作用机制，并建立相应的本构模型。通过开展不同水泥掺量和基质吸力条件下非饱和固化淤泥的固结试验、无侧限抗压强度试验和三轴剪切试验，研究固化淤泥的压缩特性、屈服应力、抗剪强度与水泥掺量和基质吸力之间的关系，全面掌握固化淤泥在胶结和基质吸力共同作用下的力学特性和变形特性；以试验资料为基础，在非饱和土Barcelona基本模型基础之上，引入下负荷面的概念，以拟似超固结比状态参量的发展描述加载过程中胶结结构特性的衰减，建立考虑胶结和基质吸力共同作用的非饱和固化淤泥弹塑性本构模型，为固化淤泥土工构筑物的设计以及自然灾害的防治提供科学依据和技术支持。

淤泥无害化处理与资源化利用已成为国内外研究者重点关注的问题。采用固化淤泥修建土工构筑物进行资源化利用时减小湿陷变形并定量描述强度衰减量和变形量是关键。本项目从固化淤泥的非饱和力学特性出发，通过固结试验、三轴剪切试验、无侧限抗压强度试验、湿化变形试验，分析了不同水泥掺量、基质吸力和围压条件下固化淤泥的力学特性和变形特性，系统研究了非饱和固化淤泥在胶结结构性和基质吸力共同作用下的变形和力学特性变化规律；建立了不同水泥掺量固化淤泥的土水特征曲线以及屈服应力、无侧限抗压强度、压缩指数、回弹指数等与水泥掺量和基质吸力之间的关系。继而，从非饱和结构性土的可能形成过程出发，对结构性土的有效应力进行修正，将非饱和结构性土的胶结作用和吸力应力考虑到有效应力当中并定义新的结构性因子，并将非饱和结构性土的正常固结压缩指数定义为结构性因子和饱和度的函数，结合结构性因子的发展式，建立了同时考虑胶结结构性和基质吸力影响的弹塑性本构模型。研究结果表明，固化淤泥的力学特性和变形特性与水泥掺量和基质吸力有关，水泥掺量越高、基质吸力越大，固化淤泥的屈服应力、抗剪强度越大；本项目提出的本构模型能够较好地反映非饱和天然结构性土和人工固化土的力学和变形特性。本项目研究成果丰富并创新了固化淤泥的理论体系，为固化淤泥资源化利用提供了理论依据和应用基础。