Incremental stress-strain-behaviour of sand at low-cycle loading and application on excavation models

内城基坑工程设计中的一个重要方面是对基坑的使用能力进行评估，同时对邻近基坑建筑物的变形进行估算。近年来的研究成果表明了岩土工程施工过程的意义，以及在高、低周反复荷载作用下发生的变形和应力状态的变化。在模拟土压力、墙体变形和沉降时，初始、卸载和再加载过程中的应力路径相关刚度起着重要作用。目前，岩土工程施工过程及其对施工状态的影响的考虑-除了一些例外-还不是最先进的。此外，通常的本构模型往往不能预测由于这些过程的变形现实或准确不够，以提高预测的基坑壁的变形，设想的研究项目应提供基本的实验结果，以支持一个新的本构模型的开发，并促进其校准和验证。通过应用其他研究小组的结果（例如接触元件），应通过使用数值挖掘模型计算变形来测试该模型的性能，特别是为此目的而开发的。根据这些结果，并与TP 6合作，最终可能会回答开放性问题，即振动和灌浆桩安装过程中岩土工程施工过程引起的变形预测。

An important aspect in the design of inner-city-located excavations is the assessment of the service ability and at the same time the deformation estimation of adjacent pits buildings. Recent research results have shown the meaning of geotechnical construction processes and the occurring deformations at high- and low-cycle loading-processes and changes of stress-states respectively. The stress-path-dependent stiffness at first-, un- and reloading processes when simulating earth-pressure, wall-deformations and settlements plays an important role. At the moment, the consideration of geotechnical construction processes and their effects on construction-states is – apart from some exceptions – not state of the art yet. In addition to that, common constitutive models are often not able to predict the deformation due to these processes realistically or accurately enough.To improve the prediction of deformations of excavation-pit-walls, the envisaged research-projects shall produce basic experimental results to support the development of a new constitutive powerful model and to facilitate its calibration and validation. By applying the results of the other researchgroup- teams (e.g. contact-elements) the performance of this model shall be tested by calculating deformations with a numerical excavation-model, especially developed for this purpose. Based on these results and collaborating with TP6 the opening question, i.e. the prognosis of deformations due to geotechnical construction processes during the installation of vibrated and grouted piles, may eventually be answered.