On modelling of slope stability in sensitive clay
Doctoral thesis, 2023
The aim of this thesis, therefore, is to explore and integrate advanced soil models for analysing the stability of slopes in natural sensitive clay. As such, the evolving hydromechanical processes known to be occurring in a slope, ranging from anisotropy to rate dependency, should be accounted for. The main research effort has consisted of; (i) verification of the use of an anisotropic failure criterion, based on the NGI-ADP model, in the upper bound limit analysis Discontinuity Layout Optimisation (DLO), and (ii) investigation the applicability of the advanced, rate-dependent, Creep-SCLAY1S model for analysing slope stability.
The result findings indicate that DLO is a most satisfactory alternative to the use of the NGI-ADP model in a Finite Element code, and a more robust alternative than Limit Equilibrium
Method. Furthermore, the second part of the study showed that while it is feasible to use a rate-dependent model for slopes, great care needs to be taken to the initialisation of the state variables, most notably the effective stress state in the sloping ground. The best results were obtained by approximately simulating the geological formation processes leading to a natural slope. The gravity increase method, instead of the strength reduction method, was required to quantify the slope stability. Consequently, the rate of increasing the gravity, i.e. the rate of loading, was shown to have a significant impact on the mobilised shear strength, thereby also the calculated stability. Overall, this thesis has contributed to the understanding of the transient coupled hydromechanical processes acting in a natural slope, and have shown that simplifications are necessary for practical applications.
mobilisation of shear strength
Chalmers, Architecture and Civil Engineering, Geology and Geotechnics
On evaluating slope stability in sensitive clay -a comparison of methods through a case study
Proceedings of the 27th European Young Geotechnical Engineers Conference,; (2019)p. 249-254
Paper in proceeding
Sellin, C., Abed, A., Dijkstra, J., Karlsson, M., & Smith, C. C. Anisotropic strength in discontinuity layout optimisation for undrained slope stability analysis
Sellin, C., Karlsson, M., & Karstunen, M. Impact of rate-dependency on slope stability in sensitive clays
Slope stability assessment in sensitive clay with an advanced constitutive model
Proceedings of the 10th European Conference on Numerical Methods in Geotechnical Engineering,; (2023)
Paper in proceeding
The currently used methods for assessing the stability in sensitive clays, however, overly simplify the soil behaviour, which might lead to unnecessary stability-improving measures in some cases, whilst yet unforeseen risks in others. Meanwhile, advanced soil models for simulating sensitive clay behaviour have been developed for other types of geotechnical problems.
This thesis explores two recently available methods for analysing the stability of natural slopes in sensitive clays. The first method allows for improved analysis of slope stability in their current state. The second approach allows to include the (future) processes of flow and deformation, including the effect of state and time. The latter results highlight the importance of simulating the past loading history when using a time-dependent soil model. Overall, the results increase the understanding of the time-dependent hydromechanical processes acting in a natural slope. Yet, some simplifications may be necessary for practical applications.
Digital Twin Cities Centre
VINNOVA (2019-00041), 2020-02-29 -- 2024-12-31.
BIG A2020-09 Simple analyses of slopes in a changing climate
Swedish Transport Administration (TRV 2020-26622), 2020-03-16 -- 2023-09-30.
Effects of climate change on soft clay slopes
Swedish Transport Administration (2016/106280I D6366), 2017-01-01 -- 2020-04-30.
NordicLink - Securing Nordic linear infrastructure networks against climate induced natural hazards
NordForsk (98335), 2020-09-01 -- 2023-08-31.
Effects of climate change on slope stability in sensitive clays
Formas (2016-00834), 2017-01-01 -- 2020-12-31.
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5372
SB-H5, Sven Hultins gata 6
Opponent: Prof. Steinar Nordal, Department of Civil and Environmental Engineering, Norwegian University of Science and Technology