絮凝-固化-真空预压联合处理吹淤新技术的内在机理与设计理论

This project aims to develop a new "flocculating-stabilizing-vacuum preloading" combined method(FSVPCM) for quick improvement of reclaimed ground filled with dredged mud. This method makes use of flocculating agent (F agent) to improve the dewatering ability and permeability of the dredged mud, utilizes the flocculating-stabilizing compound agent (FS agent) to effectively strengthen the super soft surface layer to form a bearing platform, and then depends on the traditional vacuum preloading technology to improve the bearing capacity of the reclaimed ground. Due to the presence of F/FS agents, FSVPCM is able to accelerate the vacuum preloading efficiency and overcome some other limitations of traditional solutions. However, F agent treated mud (FM) and FS agent treated mud (FSM) belong to new filling materials due to the complex physical, chemical and electrochemical reactions taking place in the mixtures. Their engineering characteristics remain unknown and no theoretical framework has been properly established. Therefore systematic investigation will be performed in this project to bridge the gaps. First, a series of laboratory trial mixture tests are to be conducted to identify the treatment efficiency of different types and dosages of F/FS agents, and the optimal types and dosages of F/FS agents will be determined. Second, the evolution of macro engineering properties of FM/FSM materials and the relevant micro mechanism will be revealed via laboratory small-scale vacuum preloading tests and environmental scanning electron microscope tests. Third, large-scale settling column tests and large-scale vacuum preloading tests will be carried out, and an appropriate large-strain consolidation theory will be proposed to characterize the evolutions of FM settlement and engineering indices during the full stage from particle sedimentation to self-weight consolidation to preloading consolidation. Finally, in conjunction with all laboratory/field tests and theoretical/numerical analysis, the main design issues will be discussed in detail and some design methodologies and guidelines will be refined for FSVPCM. The outcomes of this project are supposed to resolve the technical challenges of FSVPCM and promote the popularization of this new method in land reclamation practice.

本项目研发一种联合絮凝-固化-真空预压快速处理吹填淤泥方法-FSVPCM，该法借助絮凝剂(F剂)提升淤泥脱水渗透性能，利用絮凝固化复合剂(FS剂)高效固化表层浮泥形成承载层，并依靠真空预压提高地基承载力。FSVPCM能克服传统工法预压效率低等缺陷，值得推广。但是F/FS剂处理淤泥(FM/FSM)本质上属于新填料，其特性不明确，分析理论欠缺。因此，项目将开展试配试验探究不同F/FS剂的处理效果，优选F/FS剂类型；通过小型真空预压试验和电镜扫描，研究FM/FSM宏观性质演化规律及微观机理，建立FM/FSM本构模型；进行沉降柱试验和大型真空预压试验，揭示絮凝沉积-自重固结-预压固结全过程沉降和土性渐变特征，提出FM大变形固结理论；最后结合室内现场试验、理论和数值方法，探讨FSVPCM主要设计环节，凝练可靠的设计方法。成果将扫清FSVPCM技术障碍，促进其推广应用，提升滨海滩涂开拓效率。

近年来我国一大批港口码头扩建工程以及填海造陆工程相继投入建设，填料资源需求量十分惊人。然而受限于日益严格的生态和环境保护规程，开山石材、河砂等理想填料极度匮乏，大多新近围垦工程被迫由疏浚淤泥吹填而成。吹填淤泥往往含水率超高(呈泥浆状)、强度极低、细粒含量高、渗透性差，对其进行地基处理时施工设备往往难以进场，且常规真空(堆载)预压处理存在易淤堵、工期长、排水固结效果不佳等缺陷。因此，本项目研发了一种联合絮凝-固化-真空预压快速处理吹填淤泥方法-FSVPCM，该法借助絮凝剂(F剂)提升淤泥脱水渗透性能，利用絮凝固化复合剂(FS剂)高效固化表层浮泥形成承载层，并依靠真空预压提高地基承载力。具体来说，本项目对比了不同F/FS剂的处理效果，优选了F/FS剂类型；开展了小型真空预压和电镜扫描试验，研究了FM/FSM宏观性质演化规律及微观机理，建立了FM/FSM本构模型；实施了沉降柱试验和大型真空预压试验，揭示了絮凝沉积-自重固结-预压固结全过程沉降和土性渐变特征，提出了FM大变形固结理论；且针对FSVPCM的主要设计环节，凝练了可靠的设计方法和实施流程。研究结果表明：絮凝剂的掺入，可以显著改善淤泥的孔隙结构，扩大排水通道，显著增大预压过程中的排水速率、大大提高吹淤造地工程的施工效率，且聚丙烯酰胺(PAM)处理疏浚淤泥浆的合理掺量范围为0.137%~0.197%。使用FSCM代替传统单一水泥固化法，能大大提高固化效率，使同等条件下试样的不排水抗剪强度至少提高5倍以上，充分论证了利用FS剂高效固化表层浮泥形成承载层的技术可行性。PAM分子主要通过吸附架桥等作用改变絮团结构，促使土体骨架“三维化”和“整体化”，从而有效提高固化淤泥的强度。项目成果为FSVPCM的应用和推广扫清技术障碍，有助于明显提升滨海滩涂开拓效率。