Shield-Darcy Model: groundwater flow model calculates critical slip in piping for field conditions
G. Hoffmans, Geotechnical Engineering No. 4, March 2021, page 9
This publication describes the Shields-Darcy piping model for an aquifer in which the average grain size ranges from 0.1mm to 0.3mm. The discharges schematised herein on the river side, on the land side and in the subsurface are determined using Ohm's law and the continuity equation. For field conditions, the resistance equation obtained leads to an analytical formula, which is similar to Bligh's calculation rule. Full article
A tailored test for embankments with grass revetments in the wave impact zone. Mathematical model for determining the failure probability of clay revetments due to wave impacts.
E. Sirks, M. Klein Breteler, P. Buring, Geotechniek No 4, March 2021, page 18
Part of the Koehool-Lauwersmeer dike section is a grass dike with a gentle slope and a clay layer about 1.5m below the grass revetment. To assess the safety of this grass revetment, the available instruments are too conservative. Therefore, a mathematical model was developed with which the dike was assessed with a tailored test in a further safety analysis. The model takes both the loads on the dike and the strength of the dike into account probabilistically, resulting in a failure probability in line with the flood probability approach of the WBI. The developed calculation model is also applicable to other locations. Full article
Characteristic soil behaviour during loading and unloading of Eem clay in an undrained triaxial test
J.W. Bosschaart, F.A.J.M. Mathijssen, Geotechniek No 4, March 2021, page 24
The results of 27 undrained and 2 drained triaxial tests on slightly to moderately overconsolidated Eem clay, where axial and radial stress changes were imposed, are presented and analysed in outline in this paper. For both axial extension and radial stress changes, the observed behaviour clearly deviates from them, possibly caused by a coupling between anisotropic plasticity and elasticity within the corresponding flow contour. Full article
Geogrid-anchored sheet piles. Part 3: experiments and numerical analysis
B. Wittekoek, S.J.M. van Eekelen, J. Terwindt, M. Korff, P.G. van Duijnen, O. Detert, J. van den Berg, R. Hölter, D. König, Geotechniek No 4, March 2021, page 66
It is relatively new to use geogrids to anchor sheet piling. A series of tests in Deltares' laboratory shows how this geogrid anchoring works and how this methodology relates to CUR166 (CRW C166 sheet pile structures). The tests are simulated with 2D Plaxis sums. We see how the location of the top load, the length of the geogrids and the number of geogrids determine the bearing capacity of the structure. The results provide insight into the stabilising effect of the geogrid and the effective length of the geogrid. Full article
CUR 198 design guideline retaining structures of reinforced soil. Part 1: experiences with the analytical design rules
P. G. van Duijnen, M.G.J.M. Peters, S.J.M. van Eekelen, Geotechniek No 4, March 2021, page 73
A completely revised version of CUR 198: "Retaining Structures of Reinforced Soil" was published in 2017. The design guideline provides a design procedure consisting of eight calculation steps. This article discusses some experiences with the analytical calculations and design rules. Full article