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

在前期研究成果的基础上，开展了模型试验和室内试验，旨在研究无粘性土在典型低吸力范围内的力学特性。为了研究毛管作用对静态平板载荷试验结果的影响，进行了模型平板载荷试验。此外，单调加载的室内试验旨在了解非饱和砂土的应力-应变特性和抗剪性能。然后进行进一步的循环实验室测试，以回答循环荷载是否会影响车辆的性能，例如重型车辆的交叉，对路面地基土基质吸力的变化以及这种变化是否对沉降的累积有重要影响。模型比例的平板载荷试验将尽可能在项目第一阶段按计划进行，并将进行评估利用相似性理论。对于非饱和砂土试样的实验室试验，由于迄今已有的结果，将采用一种新的低基质吸力范围的控制和测量概念。这一概念意味着基质吸力以低于大气压的形式出现，如自然界中发现的负孔隙水压力，并将应用于综合试验方案，包括简单的剪切试验和三轴试验，试样具有恒定吸力或恒定含水量。最后，利用室内非饱和砂土试验结果对三相动力模型进行了验证，以便将其应用于模型试验和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.