Influence of uncertain soil models on the construction and design of geotechnical structures

在这项研究项目中，SPP1886将研究土体状态变量、应力状态和孔隙率的变化，以及它对圆锥贯入试验(CPTS)结果及以后对岩土结构设计的影响。借助于汉堡一个岩土勘探试验场的现有CPT数据，将进行数值优化的反参数确定，从而通过对CPT的数值模拟来推断垂直应力和空隙比分布。对于以这种方式获得的土模型，将进行进一步的数值模拟，例如，对也被测量数据覆盖的试验点的全位移桩的模拟。数值结果和测量结果将被用来研究和建立CPT尖端阻力与土壤状态变量之间的相关性。此外，还将评估在桩安装过程中获得的机械参数与土壤性质和估计桩承载力的相关性。总而言之，将研究数据的方差和不确定性对数值结果和设计的影响。在拟议的第二个研究周期中，最初假定的轴对称调查应扩展到试验场的全三维数值模型。在该模型中，土体状态变量的随机分布，即应力状态和孔隙率，将由现有的CPT测深网格确定。为此，假设状态变量的分形分布。在三维模型的帮助下，进一步研究了土体状态变量的方差对岩土结构数值设计的影响。

In this research project within the SPP 1886 it is supposed to investigate the variation of soil state variables, stress state and void ratio, and its influence on the result of cone penetration tests (CPTs) and beyond on the design of geotechnical structures. With the help of available CPT data from a geotechnically well explored test site in Hamburg an inverse parameter determination with numericaloptimization will be performed, allowing to deduce the vertical stress and void ratio distribution by numerical simulation of the CPTs. With the soil models obtained in this way further numerical simulations, e. g. simulations of full displacement piles at the test site, which are also covered by measured data, will be performed. The numerical and measured results will be used to investigate and develop correlations between CPT tip resistance and soil state variables. Furthermore, the correlation of machine parameters, obtained during pile installation, with soil properties and with estimated pile bearing capacity will be evaluated. All in all, the influence of data variance and uncertainty on the numerical results and on the design will be investigated. In a proposed second research period the initially assumed axisymmetric investigations are supposed to be expanded to a full three-dimensional numerical model of the test site. In this model a random distribution of the soil state variables, stress state and void ratio, will be determined from the available grid of CPT soundings. For this purpose, a fractal distribution of state variables is assumed. With the help of the three-dimensional models further numerical investigations on the influence of variance of soil state variables on the numerical design of geotechnical structures will be performed.