Tall buildings with basement levels are increasingly being built due to need for space in large cities. Frequently, such structures are built involving a raft foundation and diaphragm walls below the water table. In addition, sometimes such buildings are located on floodplains. Therefore, if a river flood event occurs, the building can be exposed to pore water pressure (due to the fluctuation of water table) acting beneath its raft foundation. The generated subpressures will depend on the water table changes with time, and on the way such pressures are transmitted through the ground. Previous works have studied this behavior through laboratory and small-scale tests or numerically; however, many of them have used a constant hydraulic gradient and the water table fluctuations with time have been ignored. In this work, the evolution of pore water pressures with time mobilized beneath a raft foundation of a building built in a floodplain is studied. To do that, full-scale numerical models capable of simulate a river flooding and its corresponding overflow are developed. Such models incorporate data from water table change–time curves recorded during real river floods associated with a set of river regimes. Additionally, the effect of factors such as the soil permeability, the diaphragm wall length, and the soil thicknesses on water pore pressures beneath a raft foundation are also analyzed. Results suggest numerical models developed herein are capable of reproducing pore pressures induced beneath a raft foundation during river flooding. Furthermore, it was found that the above-mentioned factors could impact the percentage of pore water pressure mobilized beneath the raft foundation with respect to the maximum pore water pressure that could be induced during river flooding, and that the principal risk arises in buildings near large catchments where the flow increases over an extended period. Finally, practical implications and recommendations to practitioners are provided.

中文翻译：

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真实河流洪水期间筏板基础下孔隙水压力响应的数值模拟


由于大城市对空间的需求，带有地下室的高层建筑越来越多地被建造。通常，此类结构的建造涉及地下水位以下的筏板基础和连续墙。此外，有时此类建筑物位于洪泛区。因此，如果发生河流洪水事件，建筑物可能会受到筏式基础下方作用的孔隙水压力（由于地下水位波动）的影响。产生的负压将取决于地下水位随时间的变化，以及这种压力通过地面传输的方式。以前的作品通过实验室和小规模测试或数值研究了这种行为；然而，他们中的许多人都使用恒定的水力梯度，并且忽略了地下水位随时间的波动。在这项工作中，研究了在洪泛区建造的建筑物筏板基础下的孔隙水压力随时间的变化。为此，开发了能够模拟河流洪水及其相应溢流的全尺寸数值模型。这些模型结合了与一组河流状况相关的真实河流洪水期间记录的地下水位变化-时间曲线的数据。此外，还分析了土壤渗透性、连续墙长度和土壤厚度等因素对筏板基础下水孔隙压力的影响。结果表明，本文开发的数值模型能够再现河流泛滥期间筏式基础下方引起的孔隙压力。 此外，研究发现，上述因素可能会影响筏板基础下方的孔隙水压力相对于河流泛滥期间可能引起的最大孔隙水压力的百分比，并且主要风险出现在大型建筑物附近流量长期增加的集水区。最后，为从业者提供了实际意义和建议。