水平排水板-真空预压-絮凝联合加固吹填淤泥的机理及固结理论研究

For faster improvement of the dredged fill, this project proposes a new method by using the combination of horizontal drains, vacuum preloading, and flocculants. This new method, called PHDVPF, switches the traditional PVD-vacuum preloading to PHD-vacuum preloading, which allows the filling process and the treatment process to happen simultaneously, therefore significantly reducing the construction period. Meanwhile, the PHDVPF uses flocculants to improve the permeability and reduce the clogging of the fills, therefore further accelerating the consolidation process. The PHDVPF has the potential to resolve some major defects of the traditional PVD treatment method (i.e., low efficiency, long duration, and easy clogging), and therefore is worth promoting. However, the PHDVPF is a new method in nature and, therefore, its working mechanism has not been investigated and its design theory lacks. For the above reasons, this project plans to conduct a systematic investigation by using laboratory model tests, large full-size tests, microscopic observations, numerical modeling, and theoretical analyses, aiming to reveal the working mechanism of the PHDVPF, to understand how flocculants modify the engineering properties of the fills and alleviate the clogging effect, to uncover the characteristics of pore-pressure dissipation and strength gaining, to understand the whole-process settlement trends of “flocculating sedimentation – self-weight consolidation – primary consolidation” and thus establish the PHDVPF consolidation model, to investigate the key technical parameters and thus establish the PHDVPF design method. The outcome of this research will resolve the main technical challenges of the PHDVPF and thus promote more popular usage of this new method in land reclamation practice.

本项目提出一种联合“水平排水板-真空预压-絮凝”快速加固吹填淤泥的新方法-PHDVPF，该法将传统竖向排水板-真空预压改为水平排水板-真空预压，可实现边吹填边加固，显著缩短工期；同时，通过絮凝剂改善淤泥脱水渗透性能并缓解排水板堵塞，进一步提高固结速度。PHDVPF有望解决传统方法效率低、周期长、易堵塞等缺陷，值得推广。但是PHDVPF本质上属于新方法，其作用机理尚不明确，计算理论欠缺。对此，本项目将通过室内模型试验、大型足尺试验、微观测试、数值模拟和理论分析开展系统深入的研究，揭示PHDVPF作用机理，明确絮凝改性淤泥的工程特性及缓解堵塞效应的机制，明确淤泥孔压消散规律和强度增长规律；揭示絮凝沉积-自重固结-主固结全过程沉降演化规律，建立PHDVPF固结计算模型；明确PHDVPF关键技术参数，建立PHDVPF设计方法。成果将扫清PHDVPF主要技术障碍，促进其推广应用，提升软土加固效率。

我国清淤工程每年都会产生大量的疏浚淤泥。为解决如何快速加固吹淤地基和消纳清淤工程中的巨量疏浚淤泥的难题，本项目对吹填淤泥加固处理方法进行了研究，提出了一种水平排水板-真空预压-化学调理（PHDVPF）联合处理吹填淤泥的方法，揭示了PHDVPF加固吹填淤泥的作用机理，建立了用于水平排水板真空预压下软土固结变形计算的固结模型。项目主要研究内容和结论如下：..（1）通过系列室内试验研究揭示了水平排水板-真空预压-化学调理联合加固吹填淤泥的作用机理、沉降变形规律及影响因素。本项目提出的PHDVPF快速固结方法，实现了吹填过程和固结过程的同步进行，且絮凝作用将加速泥颗粒沉积、提高淤泥脱水渗透性能、并缓解排水板堵塞，使得加固淤泥的效率和效果显著提升。..（2）建立了水平真空预压固结沉降模型，并推导了水平真空预压固结解析解，实现了非连续边界条件下水平真空预压固结分析，并利用数值模拟和大型现场试验结果验证了解析解的正确性，该解析解为水平真空预压固结的计算分析奠定了理论基础。并基于分段线性方法，建立了大变形水平真空预压固结数值模型，该数值模型为水平真空预压法处理疏浚淤泥的设计提供了分析工具。..本项目研究成果不仅充实了我国环境岩土工程理论，同时，提出的PHDVPF快速固结方法能有效弥补传统方法处理周期长的缺陷，大大提高吹填淤泥固结脱水效率，可推广应用于堆场淤泥脱水减量及滨海地区围填造地等工程实践。