Influence of capillarity on the mechanical behaviour of non-cohesive soils under dynamically loaded logistic areas

对于第一个项目期的结果，后续阶段包括模型试验和室内试验，目的是研究非粘性土在典型的低吸力范围内的力学特性。为了研究毛细作用对静力平板荷载试验结果的影响，静力平板荷载试验是道路建设中经常使用的密实度控制方法。此外，单调加载的室内试验旨在了解非饱和砂土的应力-应变特性和抗剪强度。然后进行进一步的室内循环试验，以回答诸如重型车辆交叉引起的循环荷载是否对路面地基土中基质吸力的变化产生影响，以及这种变化是否对沉降累积有重要影响。模型比例尺的平板荷载试验将最大限度地按计划在第一个项目期进行，并将利用相似理论进行评估。对于非饱和砂样的实验室试验，根据迄今已有的结果，将使用一种新的控制和测量概念来控制和测量低基质吸力范围。这一概念意味着在自然界中以亚大气负孔隙水压力的形式发生基质吸力，并将应用于综合测试方案，包括简单剪切测试和具有恒定吸力或恒定含水率的试件的三轴测试。最后，利用室内非饱和砂土试件的试验结果对动力三相模型进行验证，以便将其应用于模型试验和选定的现场试验的重新计算。

With regard to the results of the first project period, the sequel period consists of model tests and laboratory tests, intending to investigate the mechanical behaviour of non cohesive soils within their typical low suction range.For the investigation of the influence of capillarity on the results of static plate load tests, which are frequently used for densification control in road construction, plate load tests in a model scale are performed. Furthermore, laboratory tests with monotonic loading aim at the understanding of the stress-strain-behaviour and shear resistance of unsaturated sand. Afterwards further cyclic laboratory tests are performed in order to answer the question whether cyclic loading, for instance caused by crossing of heavy vehicles, has an impact on the change of matric suction in the pavement subsoil and whether this change is ofportance for an accumulation of settlements.The plate load tests in model scale will be done as planned for the first project period to the greatest possible extent and will be evaluated using the theory of similarity. For the laboratory tests on unsaturated sand specimens a new control and measurement concept for low matric suction ranges will be used owing to the hitherto existing results. The concept implies the occurrence of matric suction in the form of subatmospheric, negative pore water pressures as found in nature and will be applied in a comprehensive test programme, consisting of simple shear tests and triaxial tests with either constant suction or constant water content of the specimen. The loading will be applied monotonically and cyclically.Finally, a dynamic three-phase-model is supposed to be validated with the help of the test results of the laboratory tests performed on unsaturated sand specimens, in order to apply it to the recomputation of the model tests and chosen field tests.