Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

中文翻译：

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预制垂直排水管水下真空预压吸渗对沉降影响的数值研究

真空预压结合预制垂直排水沟 (PVD) 具有改善水下软质沉积物的潜力，但是，其发展在一定程度上受限于对该机制的不清楚的理解。本文旨在扩展对PVDs水下真空预压场景中重叠水影响机制的理解。系统研究通过小应变有限元排水分析进行，分离分析方案考虑了吸力固结、渗流及其组合。在超孔隙压力的积累方面，研究了改良土壤区域沉降的发展和从重叠水通过未改良土壤区域进入改良区域的渗流演变。根据数值分析结果，提出了一种理论方法。它能够估计沿改善的土壤表面随时间变化的非均匀沉降，以响应吸力固结和渗流的综合影响。讨论了PVDs水下和陆上真空预压的区别，并提供了一些实际意义和建议。