Homogenization of shear strength and modulus in spatially variable soils
Journal
Proceedings - IACMAG 2017, 15th International Conference of the International Association for Computer Methods and Advances in Geomechanics
Pages
1511-1519
Date Issued
2017
Author(s)
Abstract
Random finite element analyses (RFEA) are generally required for geotechnical problems, because random fields are needed to describe spatially varying soil properties in a realistic way. In practice, there is a common perception that a reasonably accurate but significantly simpler analysis can be conducted by replacing the spatially heterogeneous soil medium with a spatial average over a prescribed influence domain (say one diameter below a footing). This invited paper presents a detailed study of this homogenization approach. Extensive numerical results show that the widely used Vanmarcke-type spatial average over a prescribed region is not suitable for ultimate limit state problems that are governed by mobilized soil strength and that a special spatial average along the critical slip curve is needed. One key take away from this paper is an effective yet practical homogenization scheme called the weakest-path model that approximately describes the spatial average along the critical slip curve, rather than the spatial average along any arbitrary prescribed path. This model produces the statistics of this special spatial average (which is qualitatively different from the Vanmarcke-type prescribed spatial average) without invoking finite element analysis to locate the trajectory of the critical slip curve in each spatially heterogeneous realization. For the serviceability limit state, numerical results show that the spatial average over a prescribed domain is a suitable approximation for the mobilized soil modulus. However, the traditional Vanmarcke-type spatial average conducted with a uniform weighting over the averaging domain cannot represent the mobilized modulus well. A new spatial averaging method that adopts non-uniform mobilization, called the U-mobilization model, is proposed to approximate the mobilized Young’s modulus. The results presented in this paper will lead to a more rational evaluation method for the characteristic value that satisfies both probabilistic and mechanical considerations. ? 2017 15th International Conference of the International Association for Computer Methods and Advances in Geomechanics
Subjects
Geomechanics; Shear strength; Soils; Characteristic value; Geotechnical problems; Homogenization approach; Homogenization scheme; Mobilized strength and modulus; Path models; Serviceability limit state; Spatial average; Finite element method
Other Subjects
Geomechanics; Shear strength; Soils; Characteristic value; Geotechnical problems; Homogenization approach; Homogenization scheme; Mobilized strength and modulus; Path models; Serviceability limit state; Spatial average; Finite element method
Type
conference paper